EP4619150A2 - Method of preparation of ultrathin metal-organic frameworks & uses thereof - Google Patents

Method of preparation of ultrathin metal-organic frameworks & uses thereof

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Publication number
EP4619150A2
EP4619150A2 EP23804705.4A EP23804705A EP4619150A2 EP 4619150 A2 EP4619150 A2 EP 4619150A2 EP 23804705 A EP23804705 A EP 23804705A EP 4619150 A2 EP4619150 A2 EP 4619150A2
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EP
European Patent Office
Prior art keywords
substrate
film
mof
thin film
zif
Prior art date
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Pending
Application number
EP23804705.4A
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German (de)
French (fr)
Inventor
Kumar Varoon Agrawal
Qi Liu
Michael Tsapatsis
Yurun MIAO
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Ecole Polytechnique Federale de Lausanne EPFL
Johns Hopkins University
Original Assignee
Ecole Polytechnique Federale de Lausanne EPFL
Johns Hopkins University
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Priority claimed from EP22207344.7A external-priority patent/EP4368285A1/en
Application filed by Ecole Polytechnique Federale de Lausanne EPFL, Johns Hopkins University filed Critical Ecole Polytechnique Federale de Lausanne EPFL
Publication of EP4619150A2 publication Critical patent/EP4619150A2/en
Pending legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/223—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material containing metals, e.g. organo-metallic compounds, coordination complexes
    • B01J20/226—Coordination polymers, e.g. metal-organic frameworks [MOF], zeolitic imidazolate frameworks [ZIF]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/021—Carbon
    • B01D71/0211—Graphene or derivates thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/028—Molecular sieves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3202—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the carrier, support or substrate used for impregnation or coating
    • B01J20/3204—Inorganic carriers, supports or substrates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/32—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating
    • B01J20/3231—Impregnating or coating ; Solid sorbent compositions obtained from processes involving impregnating or coating characterised by the coating or impregnating layer
    • B01J20/3234—Inorganic material layers
    • B01J20/3236—Inorganic material layers containing metal, other than zeolites, e.g. oxides, hydroxides, sulphides or salts
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004—Photosensitive materials
    • G03F7/0042—Photosensitive materials with inorganic or organometallic light-sensitive compounds not otherwise provided for, e.g. inorganic resists
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/20—Exposure; Apparatus therefor
    • G03F7/2051—Exposure without an original mask, e.g. using a programmed deflection of a point source, by scanning, by drawing with a light beam, using an addressed light or corpuscular source
    • G03F7/2059—Exposure without an original mask, e.g. using a programmed deflection of a point source, by scanning, by drawing with a light beam, using an addressed light or corpuscular source using a scanning corpuscular radiation beam, e.g. an electron beam

Definitions

  • the present invention pertains generally to the field of preparation of metal-organic frameworks (MOFs), in particular Zeolitic imidazolate frameworks (ZIFs) and uses thereof.
  • MOFs metal-organic frameworks
  • ZIFs Zeolitic imidazolate frameworks
  • MOFs are organic-inorganic structures, highly porous structures that are obtained through precisely controlled structures in which two components of metal cations as nodes and organic molecules as bridges have been engineered.
  • Zeolitic imidazolate frameworks (ZIFs) (Banerjee et al., 2008, Science 319, 939-943; Guillerm et al., 2014, Chem. Soc. Rev. 43, 6141-6172') are nanoporous ordered materials belonging to a class of metal-organic frameworks (MOFs) but exhibiting zeolitic topology and high chemical and thermal stability and that hold promise for applications in molecular separations (Zhou et al., 2018, Sci. Adv. 4:eaaul393; Ma et al., 2018, Science 361, 1008-1011), patterning (Stassen et al. 2013, CrystEngComm, 15, 9308-9311; Miao et al.
  • MOFs metal-organic frameworks
  • ZIFs are constructed by linking Zn2 + or Co 2+ ions with organic imidazolate (Im) linkers.
  • Im organic imidazolate
  • ZIFs generally exhibit high CO2 uptake, making them suitable for CO2 based gas separation and storage.
  • the presence of organic linkers enables various strategies to fine tune pore size and aperture as well as the pore polarity of ZIFs.
  • A-scale biological channels represent the ideal design of selective layer because of their nanometer-scale pathlength (Epsztein etal, 2020, Nat. Nanotechnol. 15, 426- 436).
  • ZIF-8 is constructed by linking 2-methylimidazolate with Zn2+ metal ions and has a sodalite (SOD) topology containing a cuboctahedral structure (Park, et al., 2006, Proc. Natl. Acad. Set. U. S. A., 103, 10186-10191). Due to this unit cell structure permeation through ZIF-8 can occur in three dimensions. Moreover, the flexibility of the 2-methylimidazolate linkers in the ZIF-8 structure make the framework dynamic, where linker rotation can increase the crystallographic size of the pore aperture from 3.4 A to a dynamic pore aperture of 4.0-4.2 A (Qian et al., 2020, Chem. Rev., 120, pp. 8161-8266).
  • the range of the ZIF-8 pore aperture size lies within the spectrum of the kinetic diameters of several industrial relevant gases, such as CO2 (3.3 A), N2 (3.64 A) and CH4 (3.8 A), which can be regarded as the main motivation for the use of ZIF-8 in mixed matrix membranes (Essen et al., 2020, Separation and Purification Technology 260, 1, 118103).
  • Amorphous MOFs exhibit unique physical and chemical properties due to the absence of anisotropy and crystalline grains (Bennett et al., 2018, Nat. Rev. Mater. 3, 431-440). They are especially attractive for lithographic patterning because of their improved homogeneity and processability compared to their polycrystalline counterparts.
  • the present invention is based on the unexpected finding of a process that allows obtaining macroscopically uniform ultrathin amorphous MOF films, in particular two-dimensional (2D) ZIF (2DZIF) films on graphitic substrates, with thickness down to that of a single structural building unit (2 nm), the smallest structural repeating unit, with record high permselective H2 flux. It was unexpectedly found that the provision of a film having a thickness of the smallest height needed to be ordered leads to 2DZIF films with a rigid lattice framework that allows achieving efficient H2/N2 selectivity.
  • the unique lattice parameter which can be obtained is due to registry of the 2DZIF to the underlying graphitic substrate.
  • the lattice registry refers to an excellent match between the lattice parameters of 2DZIF and a supercell of graphene which maximizes the interaction of 2DZIF with graphene lattice favoring the growth of 2DZIF on graphene.
  • the lattice registry also makes the lattice framework of 2DZIF rigid, allowing to realize a large H2/N2 selectivity.
  • One of the specific objects of this invention is to provide an efficient method of preparation of 2D ZIF films under a fully controlled growth process with a resolution of a single layer.
  • ultrathin e.g., from about 2 nm to about 20 nm
  • 2D ZIF films on graphitic substrates and related 2D materials for membrane applications.
  • Objects of this invention have been achieved by providing a method for the preparation of a porous metal-organic framework according to claim 1.
  • a method for the preparation of a MOF coated 2D substrate comprising the steps of: a) Providing a 2D substrate; b) Providing an ultra-diluted MOF metal precursor solution, wherein said an ultra-diluted MOF metal precursor solution contains ⁇ 20 mM of metal ions and ⁇ 40 mM organic ligand, in particular ⁇ 10 mM of metal ions and ⁇ 20 mM organic ligand and more particularly ⁇ 2 mM of metal ions and ⁇ 16 mM organic ligand; c) contacting the said substrate with the ultra-diluted MOF metal precursor solution for about 2 to about 30 min (e.g., 2 to 20 min or 2 to 15 min), for example by fully or partially immersing said substrate in said precursor solution or by flowing the said precursor solution over the substrate; d) removing the obtained MOF coated substrate from the precursor solution, wherein the MOF
  • the obtained product in the form of ZIF coated graphene substrate is used for preparing a gas filter.
  • H2 flux typically higher than 1 mol m' 2 s' 1
  • H2/N2 separation factor typically higher than 20
  • Objects of this invention have been achieved by providing a graphitic substrate coated with two- dimensional crystalline ZIF (2DZIF) film according to claim 16 or 17.
  • Objects of this invention have been achieved by providing an amorphous substrate coated with an amorphous ZIF (aZIF) film according to claim 21.
  • aZIF amorphous ZIF
  • Objects of this invention have been achieved by providing a use of an amorphous porous substrate coated with amorphous ZIF (aZIF) film according to claim 22.
  • aZIF amorphous ZIF
  • a graphitic substrate coated with a two-dimensional crystalline ZIF (2DZIF) film wherein the said film’s thickness is from about 2 nm to about 20 nm (e.g., about 2 nm) and the film’s pore density from about 10 to about 60%, in particular 30% to about 60% (e.g., Also disclosed herein is a gas selective filter wherein the graphene membrane is made with a method according to the invention.
  • 2DZIF two-dimensional crystalline ZIF
  • gas selective filter comprising a membrane for gas separation, in particular for separating H2 from N2 and CH4.
  • the H2 permeance of the gas filter is from about 2’000 GPU to about 20’000 GPU, namely from about 7.7 x 10' 7 to about 7.7 x 10' 6 mol m' 2 s' 1 Pa' 1 (e.g., 6 x 10' 6 mol m' 2 s' 1 Pa' 1 at 25°C under 2 bar).
  • the H2/N2 selectivity of a gas filter according to the invention is higher than 20, in particular from 20 to about 117 (e.g., from about 25 to 70) at 25°C under 2 bar.
  • the gas filter according to the invention according to the invention exhibits high permselective H2 flux.
  • a method for the preparation of a MOF coated on amorphous substrate comprises the steps of a) Providing an amorphous substrate; b) providing a MOF metal precursor solution, wherein said MOF metal precursor solution contains ⁇ 20 mM of metal ions and ⁇ 200 mM organic ligand, in particular contains ⁇ 10 mM of metal ions and ⁇ 40 mM organic ligand and more particularly ⁇ 2 mM of metal ions and ⁇ 16 mM organic ligand; c) contacting the said substrate with the MOF metal precursor solution for about 2 to about 30 min (e.g., 2 to 20 min or 2 to 15 min), for example by fully or partially immersing said substrate in said precursor solution or by flowing the said precursor solution over the substrate; d) removing the obtained amorphous MOF coated substrate, wherein the amorphous MOF coated substrate comprises a MOF layer from about 2 to about 1’000 nm coated on said amorphous substrate.
  • Amorphous films can be deposited under ultra dilute conditions as described for obtaining crystalline MOFs but also at higher concentrations.
  • amorphous porous substrate coated with an amorphous ZIF (aZIF) film wherein the said film’s thickness is from about 8 nm to about 20 nm (e.g., about 10 nm).
  • an amorphous porous substrate coated with an amorphous ZIF (aZIF) film wherein the said film’s thickness is from about 8 nm to about 30 nm or more depending on the deposition time and the number of coatings used to deposit the aZIF film on the substrate.
  • the obtained product in the form of a ZIF coated non-porous substrate is used in imprinting or lithographic patterning processes (e.g., generating a patterned aZIF coating on substrates).
  • a miniaturized catalytic, sensing, luminescent or biomedical (e.g. microfluidic or lab-on-a-chip device) device comprising an amorphous ZIF (aZIF) film according to the invention.
  • aZIF amorphous ZIF
  • Also disclosed herein is a method for patterning a thin MOF film on a substrate.
  • the aZIF films may be converted to crystalline ZIFs upon exposure to imidazole ligands or vapors of organic solvents, e.g. ethanol or DMF.
  • the method reported here will likely accelerate the development of 2D crystalline and ultrathin amorphous MOF films for applications ranging from separation membranes to patterning.
  • Figure 1 illustrates the synthesis ZIF films from ultra-dilute solutions as described in Example 1.
  • a Schematic representation of the formation of a ZIF film on a substrate
  • b Composition diagram comparing the precursor solution composition used in the method of the invention with those reported in the literature (as detailed in Table 1).
  • AFM c
  • d the corresponding height profile of a monolayer ZIF film on HOPG.
  • e Monolayer and multilayer ZIF films on HOPG with discrete thicknesses as a function of synthesis time.
  • Figure 2 presents the structure determination of 2DZIF films as described in Example 2.
  • a Bright- field TEM image of the 2DZIF film supported on suspended graphene, and (b) its corresponding SAED pattern. The pattern from graphene is identified with green circles and those from 2DZIF with white circles
  • c In-plane GIXRD data from a 2DZIF film (middle) prepared on graphene/Si/SiO2 along with a radially integrated trace (bottom) of the SAED pattern shown in (b).
  • d Nls XPS spectra from ZIF-8, ZIF-L (comparative, not from the invention) and 2DZIF films.
  • N-Zn and N-H coordination environments are shown on the right, e: DFT-relaxed structure of the 2DZIF and a visualization of the 6-member-ring (6-MR) and its 3.2 A gap.
  • f HRTEM image of the 2DZIF film lying flat on the hkO plane, resting on suspended graphene, and (g) corresponding Fourier transform compared with the simulated diffraction pattern from the proposed structure oriented along the c-out-of-plane direction
  • h Left: CTF-corrected image of the highlighted area in (f) based on a defocus value of -130 nm analysed from the Thon rings in the Fourier transform pattern.
  • Right simulated projected potential map along the [001] direction of 2DZIF.
  • Figure 3 presents the characterization of the 2DZIF structure as described in Example 2 and its relationship with comparative ZIF-L.
  • a Schematic contrasting the arrangement of layers within a ZIF-L crystal with that of a monolayer 2DZIF according to the invention
  • b Epitaxial relationship between the graphene lattice and 2DZIF.
  • c Structures of a 2DZIF layer according to the invention (left) and ZIF-L (right) viewed along the [001], [100], and [010] directions
  • d Schematic illustration of the etching of 2DZIF in water.
  • Figure 4 represents possible applications of 2DZIF obtained by a method of the invention
  • a Schematic of a 2DZIF film supported on nanoporous graphene (NG) reinforced with PTMSP.
  • b EE, CO2, N2 and CH4 permeances of the PTMSP/NG support and the supported 2DZIF film on PTMSP/NG.
  • c 2DZIF membrane separation performance for an equimolar H2/N2 mixed feed
  • d Comparison of the H2/N2 separation performance of 2DZIF membranes with the state-of-the-art membranes (as detailed in Fig. 4e).
  • GO, CMP, and HOF refer to graphene oxide, conjugated microporous polymers and hydrogen-bonded organic frameworks, respectively, e: Gas permeance and ideal selectivity of a film of the invention compared to the state of the art in the literature; f: Optical photo of 1 cm scale 2DZIF membrane in module and (g) its schematic structure.
  • Figure 5 presents the synthesis MOF films from ultradilute solutions according to a method of the invention as described in Example 4.
  • a Structure of the metal-organic framework U1O-66-NH2;
  • b SEM image of U1O-66-NH2 film synthesized on HOPG;
  • c AFM image and corresponding height profile for UiO-66-NH2 film synthesized on HOPG.
  • e and
  • f Bright-field TEM image of the UiO- 66-NH2 film supported on suspended graphene and its corresponding SAED pattern, where grey and white circles are presenting diffraction from graphene and U1O-66-NH2, respectively.
  • Figure 6 illustrates the synthesis ZIF films on Si/SiO2 as described in Examples 5 and 6 from ultradilute solutions
  • a SEM and optical images of a ZIF film on Si/SiO2.
  • b AFM and the corresponding height profile (c) of the ZIF film on Si/SiO2
  • d Ellipsometry of several ZIF films on Si/SiO2 wafer.
  • Figure 7 presents the structure determination of aZIF films as described in Example 8.
  • a In-plane GIXRD data from an aZIF film prepared on Si/SiC>2
  • Figure 8 represents possible applications of aZIF obtained by a method of the invention
  • a Schematic of the negative tone patterning process, where the electron beam irradiated regions remain while the non-irradiated regions are removed in the development step using water.
  • d AFM height profile corresponding to the line in (c).
  • Figure 9 represents the synthesis of another 2DZIF film using Zn as the metal and benzimidazole (Bim) as the linker with composition of Zn2(Bim)4 according to the invention on 2D substrates using another ultradilute precursor solutions as described in Example 9.
  • A schematic representation of the range of compositions of the ultradilute precursor solutions where 2D film can be successfully grown according to a method of the invention.
  • B electron diffraction pattern from the 2D Zn2(Bim)4 film showing single crystal diffraction.
  • C average of H2/CO2 separation properties (H2 permeance and H2/CO2 selectivity) from the 2D Zn2(Bim)4 film, depending on the number of cycles of deposition (one cycle and five cycles).
  • Figure 10 represents the characterization of dip coated films as described in Example 5.
  • A SEM and optical micrographs of amorphous ZIF film on a silicon wafer; the area that was immersed in the solution and was coated with amorphous ZIF is on the right and is marked ’’aZIF”;
  • B Atomic force microscopy (AFM) image height image of an amorphous ZIF film deposited on a silicon wafer.
  • C the height profile measured across the deposition boundary indicating a film thickness of 14 nm.
  • Figure 11 illustrates the preparation of flow-coated films as described in Example 6.
  • A Photograph (top) and drawing (bottom) of the flow coating device. The two solutions are introduced from the left side of the device and are mixed in the chamber containing the stirrer (the stirrer color is blue), and then they flow over the substrate under laminar flow.
  • B Flow coated films, with the coating time indicated above each wafer (2, 4, 6, 8 min) and the thickness measured by ellipsometry indicated under each wafer (66, 148, 215, 266 nm).
  • Figure 12 illustrates the preparation of spin-coated films as described in Example 7.
  • the thickness measured from ellipsometry are 96 and 204 nm for the 2 and 4 min coated films, respectively.
  • Figure 13 illustrates aZIF film patterned by a 5 keV electron beam using 2-pm squares of different doses, as indicated in units of mC/cm 2 (A) followed by development in acidic solutions as described in Example 10, in 0.01 M aqueous solution of acetic acid (B) or HC1 (C) for 10 min.
  • Figure 14 illustrates aZIF film patterned by a 5 keV electron beam using 2-pm squares of different doses, as indicated in units of mC/cm 2 (A) followed by development in basic solutions as described in Example 11, in 0.01 M aqueous solution of TPAOH (B) for 10 min.
  • Figure 15 illustrates aZIF film patterned by a 5 keV electron beam using squares of different doses, followed by dry development using hfac-H at 120°C for 10 min as described in Example 12.
  • the electron dose for each 2 pm square in unit of mC/cm 2 is indicated in the schematic above the AFM images.
  • the three columns correspond to dose ranges of 0.125-2.5, 0.5-10 and 2-40 mC/cm 2 from left to right, respectively.
  • Figure 16 illustrates positive tone patterning of a aZIF as described in Example 13.
  • the aZIF film is first treated with the vapor of dclm at 75°C for 90 min, followed by patterning with 5 kV, 0.5 mC/cm 2 electron beam using a dot pattern of 100 nm diameter and 100 nm spacing, and subsequently immersed in acetone for 10 s to remove the irradiated area.
  • MOF Metal organic framework
  • Metal organic framework refers to uniform structured porous materials fabricated by linking inorganic and organic units by strong bonds (reticular synthesis) which consist in of metal ions or clusters coordinated to organic ligands to form one-, two-, or three-dimensional structures.
  • the organic ligands included are sometimes referred to as "struts” or “linkers”.
  • struts or “linkers”.
  • the choice of metal and linker dictates the structure and hence properties of the MOF. For example, the metal's coordination preference influences the size and shape of pores by dictating how many ligands can bind to the metal and in which orientation.
  • SBU secondary building units
  • a system of nomenclature has been developed and subunits of a MOF, called secondary building units (SBU), can be described by topologies common to several structures.
  • Each topology also called a net, is assigned a symbol (Seidi et al., 2020, Materials (Basel).13(12): 2881; Furukawa et al., 2013, Science 341:1230444).
  • a Zr-MOF, UiO-66 is a coordination polymer».
  • the monomers, AKA “building blocks”, are bdc and ZreO4 (OH)4 clusters.
  • UiO-66 is the progenitor of a family of zirconium-based MOFs: the same ZreO4 (OH)4 clusters found in UiO- 66 serve as SBUs for a whole class of materials displaying a wide range of topologies, accessible by employing linkers having specific geometrical and symmetrical features.
  • ZIFs Zeolitic imidazolate frameworks
  • ZIF-8 Zn-Based MOF.
  • UiO-66 a zirconium(IV)-based MOF
  • BDC bidentate benzene-1,4- dicarboxylic acid
  • 2D substrate refers to a 2D materials, including graphitic substrates and hexagonal boron nitride (A-BN), M0S2, and the like.
  • Porosity of 2D materials can be measured in a standard manner by transmission electron microscopy-based imaging.
  • graphitic substrate stands for graphitic-like material, namely atomically-smooth crystalline substrate which includes graphite and its derivatives such as highly-oriented pyrolytic graphite (HOPG) or graphene or porous graphene substrates. According to another aspect, it also includes other two-dimensional materials (e.g., M0S2, A-BN, etc.).
  • HOPG is a highly pure and ordered form of synthetic graphite characterized by a low mosaic spread angle, meaning that the individual graphite crystallites are well aligned with each other.
  • the best HOPG samples have mosaic spreads of less than 1 degree.
  • amorphous substrate refers to any material without any crystallographic order at its surface. It includes Si/SiO2 wafers, amorphous SiN, glass, amorphous ceramics and the like.
  • MOF metal precursor solution comprises metal ions such as Zn 2+ or Co 2+ or Zr +4 , an organic ligand such as 2-methylimidazole or imidazole, or benzimidazole or 2-ethylimidazole or purine or benzene- 1,4-dicarboxylic acid, and a solvent such as water.
  • metal ions such as Zn 2+ or Co 2+ or Zr +4
  • organic ligand such as 2-methylimidazole or imidazole, or benzimidazole or 2-ethylimidazole or purine or benzene- 1,4-dicarboxylic acid
  • solvent such as water.
  • photomask refers to a prepatterned stencil that allows either light or electrons to pass through onto the resist only where the defined pattern is.
  • resist is used herein to refer to a thin photosensitive layer used to transfer circuit patterns to the surface of a substrate on which the resist is deposited.
  • Fig. la an illustration of a method of preparation of a MOF coated on a 2D substrate according to an embodiment of the invention.
  • the illustrated method generally comprises the steps of: a) Providing a 2D substrate; b) providing an ultra-dilute MOF metal precursor solution, wherein said an ultra-diluted MOF metal precursor solution contains ⁇ 20 mM of metal ions and ⁇ 40 mM organic ligand, in particular ⁇ 10 mM of metal ions and ⁇ 20 mM organic ligand and more in particularly ⁇ 2 mM of metal ions and ⁇ 16 mM organic ligand; c) contacting the said substrate with the ultra-diluted MOF metal precursor solution for about 2 to about 30 min (e.g., 2 to 20 min or 2 to 15 min), for example by fully or partially immersing said substrate in said precursor solution or by flowing the said precursor solution over the substrate; c) removing the obtained MOF coated 2D substrate from the precursor solution, wherein the MOF
  • the 2D substrate is a porous 2D substrate with a porosity from about 0.1 to about 30% and a thickness from about 0.3 to about 1 nm.
  • the 2D substrate is a porous 2D substrate with pore size from about 0.3 to about 5 nm.
  • the 2D substrate is a 2D porous graphite substrate with a porosity about 5 to about 20% (e.g., from about 10 to about 18 %) and thickness of about 0.3 to about 1.0 nm (e.g., 0.3 nm).
  • the 2D porous substrate is a HOPG substrate, for example with a thickness about 1 mm.
  • the 2D porous substrate is a 2D porous graphite substrate mechanically reinforced with a porous polymeric film (e.g., PTMSP or Teflon AF layer of about 50 to 1000 nm) or nanoporous carbon film with thickness of 100 to 1000 nm.
  • a porous polymeric film e.g., PTMSP or Teflon AF layer of about 50 to 1000 nm
  • nanoporous carbon film with thickness of 100 to 1000 nm.
  • the metal-organic framework is a ZIF, in particular a Zn-based MOF.
  • the metal-organic framework is a Zr-MOF, in particular UiO-66.
  • the said substrate is fully or partially immersed in the ultra-diluted MOF metal precursor solution for about 2 to about 30 min (e.g., 2 to 15 min).
  • a method of the invention for the preparation of a two-dimensional crystalline ZIF (2DZIF) film on a 2D substrate wherein ultra-dilute MOF metal precursor solution contains ⁇ 10 mM of metal ions and ⁇ 20 mM organic ligand.
  • ultra-dilute MOF metal precursor solution contains ⁇ 10 mM of metal ions and ⁇ 11 mM organic ligand.
  • the metal-organic framework is a ZIF and the MOF metal precursor solution contains ⁇ 20 mM of Zn 2+ and ⁇ 40 mM 2-methylimidazole (2mlm).
  • the said substrate is exposed to a flowing solution containing metal ions and imidazolate ligands for about 2 min to about 30 min or up to any desired time depending on the target thickness; the longer the coating time, the thicker the deposit.
  • the metal-organic framework is a ZIF and the ultra-diluted MOF metal precursor solution contains ⁇ 2 mM of Zn 2+ and ⁇ 16 mM 2-methylimidazole (2mlm).
  • the ultra-diluted MOF metal precursor solution contains from about 0.5 to about 2 mM of Zn 2+ (e.g., from about 1 to about 2 mM of Zn 2+ ).
  • the ultra-diluted MOF metal precursor solution contains from about 4 to about 16 mM 2-methylimidazole (e.g., from about 8 to about 16 mM 2- methylimidazole).
  • the metal-organic framework is a ZIF and the ultradiluted MOF metal precursor solution contains ⁇ 20 mM of Zn 2+ and ⁇ 20 mM benzimidazole (BIm), in particular contains ⁇ 10 mM of Zn 2+ and ⁇ 11 mM benzimidazole (BIm).
  • the ultra-diluted MOF metal precursor solution contains from about 1 to about 20 mM of Zn 2+ (e.g., from about 5 to about 10 mM of Zn 2+ ).
  • the ultra-diluted MOF metal precursor solution contains from about 1 to about 10 mM benzimidazole (e.g., from about 3 to about 7 mM benzimidazole).
  • the thickness of the MOF film depends on two parameters: concentration of precursor solution as well as deposition time and can therefore be adjusted by varying those parameters in the frame of the present invention.
  • the porous substrate is immersed in the ultra-diluted MOF metal precursor solution from 1 to about 10 minutes (e.g., about 2 to about 5 minutes).
  • the MOF coated substrate according to the invention comprises a MOF layer from about 2 to about 10 nm coated on said substrate
  • the obtained MOF coated 2D substrate obtained from step d) can be further submitted to one or more (e.g., 1 to 4 further cycles of steps b) to c)) to achieve repeated depositions through the immersion in the ultradiluted precursor solution.
  • the thickness obtained for 2 cycles (2 layers) is about 4 nm and about 10 nm for 5 cycles.
  • a method according to the invention allows the preparation of a MOF, in particular a ZIF film under epitaxial condition, i.e. where the deposited film takes on a lattice structure and orientation identical to those of the substrate.
  • the resulting 2D ZIF coated porous graphene substrate is used for preparing a gas filter.
  • a graphitic substrate coated with two-dimensional crystalline ZIF (2DZIF) film wherein the said film’s thickness is from about 2 to about 20 nm (e.g., from about 2 to about 18 nm, such as from about 2 to about 10 nm) and the film’s pore density from about 30 to about 60% (e.g., 50 %).
  • 2DZIF two-dimensional crystalline ZIF
  • a graphitic substrate coated with two-dimensional crystalline ZIF (2DZIF) film according to the invention wherein the size of the pores of the ZIF film is from about 0.25 to about 1 nm, preferably from about 0.3 to about 0.4 nm.
  • a graphitic substrate coated with two-dimensional crystalline ZIF (2DZIF) film wherein the crystalline structure comprises a pore aperture made of a six-membered zinc-imidazolate coordination ring with an effective van der Waals gap of about 3.2 A estimated by a crystallography software (Diamond).
  • 2DZIF two-dimensional crystalline ZIF
  • a gas selective filter wherein the graphene membrane is prepared with a method according to the invention.
  • a gas selective filter comprising a porous graphitic substrate coated with two-dimensional ZIF (2DZIF) film according to the invention.
  • gas selective filter selecting Ft from N2 comprising an assembly of graphene membranes according to the invention.
  • a gas selective filter comprising a membrane for gas separation, in particular for separating H2 from N2.
  • the H2 permeance of the gas filter is from about 15’000 GPU to about 20’000 GPU, namely from about 50.2 x 10' 7 to about 7.7 x 10' 6 mol m' 2 s' 1 Pa' 1 (e.g., 6 x 10" 6 mol m' 2 s' 1 Pa' 1 ) at 25°C under 2 bar.
  • the H2/N2 selectivity of a gas filter according to the invention is from about 50 to about 70 at 25°C.
  • an illustration of a method of preparation of a MOF coated on an amorphous substrate generally comprises the steps of: e) Providing an amorphous substrate; f) providing a MOF metal precursor solution, wherein said MOF metal precursor solution contains ⁇ 20 mM of metal ions and ⁇ 200 mM organic ligand, in particular contains ⁇ 10 mM of metal ions and ⁇ 40 mM organic ligand and more in particular ⁇ 2 mM of metal ions and ⁇ 16 mM organic ligand; g) contacting the said substrate with the MOF metal precursor solution for about 2 to about 30 min (e.g., 2 to 20 min or 2 to 15 min), for example by fully or partially immersing said substrate in said precursor solution or by flowing the said precursor solution over the substrate; h) removing the obtained amorphous MOF coated substrate, wherein the amorphous MOF coated substrate comprises a MOF layer from about 2 to about 1,000 n
  • the substrate is a silicon wafer.
  • the amorphous substrate is a Si/SiO2 wafer.
  • the substrate is a SiNx thin membrane.
  • the said substrate is first contacted with a source of diluted metal ion such as Zn 2+ (e.g. Zn(NOs)2) and then the diluted organic ligand is added to the solution to form the ultra-diluted MOF metal precursor solution.
  • a source of diluted metal ion such as Zn 2+ (e.g. Zn(NOs)2)
  • the diluted organic ligand is added to the solution to form the ultra-diluted MOF metal precursor solution.
  • the contacting is performed using two streams of solutions, 1 and 2, that are mixed before contacting the substrate to form an ultra-diluted MOF metal precursor solution, where stream 1 containing the solution of the metal ions, and stream 2 containing the solution of the ligand.
  • the contacting step is performed in a flow coating or spin coating device where the mixing of the two streams of solutions is accomplished immediately before the fluid contacts the substrate.
  • amorphous substrate coated with an amorphous ZIF (aZIF) film wherein the said film’s thickness is from about 2 to 20 nm, in particular, 8 nm to about 20 nm (e.g., about 10 to 19 nm).
  • a method for providing an amorphous ZIF (aZIF) film wherein the imidazolate is a derivative of l,3-diazacyclopenta-2,4-diene having a chemical C3N2HR3, wherein the R groups are positioned at the 1, 4, and 5 positions of 1,3- diazacyclopenta-2,4-diene and are each independently selected from -H, -CH3, -CH2CH3, -Cl, -Br, -I, -C4H4, and -CHO.
  • aZIF amorphous ZIF
  • the imidazolate is selected from: and combinations thereof.
  • a method for providing an amorphous ZIF (aZIF) film wherein the metal ion is one of Zn +2 , Co +2/+3 , In +3 , or mixtures thereof.
  • a method for patterning a thin ZIF film on a substrate comprising:
  • a method for patterning a thin film according to the invention wherein the patterning further comprises irradiating the thin film with an electron source, an X-ray source, a deep ultraviolet, an extreme ultraviolet source, or other radiation source capable of producing secondary electrons.
  • the electron beam has an acceleration voltage with a range from about 2keV to about 100 keV.
  • the electron beam has a current with a range from about 6.3 pA to about 1.2 nA.
  • the electron beam has a dosage with a range from about 0.01 mC cm' 2 to about 50 mC cm' 2 .
  • a method for etching a thin film on a substrate wherein the thin film comprises a thin film of an amorphous ZIF (aZIF) film according to the invention, the method comprising contacting the film with an etching solution.
  • aZIF amorphous ZIF
  • the etching solution is an acidic solution.
  • the etching solution is a basic solution.
  • the etching solution is water, methanol, ethanol, DMF, HC1, acetic acid, solutions of NaOH, KOH, TMAOH, TEAOH, TPAOH, or TBAOH in water or mixtures thereof.
  • a method for etching a thin film on a substrate wherein the said film is contacted with the etching solution for a period of time between about 1 minute and about 24 hours, at temperature from room temperature to about 60°C.
  • a method of developing a patterned thin film on a substrate wherein the patterned thin film comprises a thin amorphous ZIF (aZIF) film according to the invention, patterned by any of the methods described therein, followed by liquid-etching using any of the methods to form a patterned deposit as described herein.
  • aZIF thin amorphous ZIF
  • the film is purged with an inert gas and removed from the reactor.
  • a method for etching a thin film on a substrate wherein a vapor-phase etchant is contacted with the film.
  • a method for etching a thin film on a substrate wherein the etchant B comprises one or more P-diketonates.
  • the one or more P-diketonates is selected from:
  • the thin film is exposed to the etchant for a period of time between about 1 minute and about 15 minutes under a set temperature ranging between about 25°C to about 300°C, for example, 5 minutes at 120 °C.
  • the thin film is sequentially exposed to the etchant for a period of time between 1 minute and 15 minutes followed by purging the reactor with an inert gas comprising a combination of one or more of helium, neon, argon, krypton, or xenon, for a period of time between 1 minute and 15 minutes.
  • an inert gas comprising a combination of one or more of helium, neon, argon, krypton, or xenon, for a period of time between 1 minute and 15 minutes.
  • a method of developing a patterned thin film on a substrate according to the invention wherein the patterned thin film comprises a thin amorphous ZIF (aZIF) film according to the invention, patterned by any of the methods described therein, followed by dry-etching using any of the methods as described herein to form a patterned deposit.
  • aZIF thin amorphous ZIF
  • the obtained product in the form of a ZIF coated amorphous porous substrate is used in imprinting or lithographic patterning processes (e.g., generating a patterned MOF coating on removable substrates).
  • Patterned MOF can be used in microelectronics, electrochemical devices and in sensors.
  • a non-crystalline thin film according to the invention wherein the metal ion is selected from Co +2 / +3 , Zn +2 , and In +3 or combinations thereof.
  • a non-crystalline thin film wherein the ratio of the metal to the imidazolate compound as determined by X-ray photoelectron spectroscopy (XPS) is 1 : 1.5 to 1 :2.5.
  • XPS X-ray photoelectron spectroscopy
  • a non-crystalline thin film wherein the imidazolate is a derivative of l,3-diazacyclopenta-2,4-diene having a chemical C3N2HR3, wherein the R groups are positioned at the 1, 4, and 5 positions of l,3-diazacyclopenta-2,4-diene and are each independently selected from -H, -CH3, -CH2CH3, -Cl, -Br, -I, -C4H4, and -CHO.
  • a non-crystalline thin film wherein the imidazolate is selected from: and combinations thereof.
  • a non-crystalline metal-imidazolate thin film according to the invention wherein the ligand comprises 2-methylimidazole (2mlm).
  • a non-crystalline metal-imidazolate thin film according to the invention wherein the metal-imidazolate film comprises a zinc-imidazolate film.
  • the thin non-crystalline film has a surface roughness of less than 5 nm.
  • a patterned deposit on a substrate made by any of the methods described therein.
  • the developed pattern has a line edge roughness of less than 2 nm.
  • the developed pattern has a feature resolution of about 10 nm.
  • the developed pattern has a feature thickness between about 2 and about 50 nanometers.
  • the developed pattern has a pitch of 30 nanometers or less.
  • an article comprising a non-crystalline thin film of the invention.
  • an article comprising a non-crystalline thin film of the invention, wherein the article is selected from an extreme ultraviolet lithography (EUVL) resist, a membrane for gas separation, a gas sensor, and a microelectronic device.
  • EUVL extreme ultraviolet lithography
  • an article comprising a non-crystalline thin film of the invention, further comprising a material resulting from the irradiation of the thin film and which is not removed by a subsequent etching process.
  • an article comprising a non-crystalline thin film of the invention, further comprising a material resulting from the irradiation of portions of the thin film and a subsequent etching or dissolution process that preferentially removes the irradiated or the non-irradiated portion of the thin film.
  • an article comprising a non-crystalline thin film of the invention, wherein the article is selected from a structural material, a dielectric barrier, and a photomask.
  • a miniaturized catalytic, sensing, luminescent or biomedical (e.g. microfluidic or lab-on-a-chip device) device comprising an amorphous ZIF (aZIF) film according to the invention.
  • aZIF amorphous ZIF
  • the method reported here will likely accelerate the development of 2D crystalline and ultrathin amorphous MOF films for applications ranging from separation membranes to patterning.
  • the film crystallinity is determined by the interaction of molecular precursors with the substrate ranging from epitaxy- determined order to amorphous films in the absence of any crystallographic registry.
  • a gas selective filter comprising a 2D ZIF coated graphene membrane having a thickness of 2 to 10 nm wherein the size of the pores of the ZIF film is in the range of 0.25-1 nm, preferably 0.3-0.4 nm.
  • a method and of the invention further advantageously provides useful starting materials for the preparation of membranes suitable for separation H2 from N2 where a H2 permeance reaching 20’000 gas permeation units with H2/N2 selectivity reaching 52, at 25°C.
  • Si/SiC>2 wafer with single layer graphene was bought from Ted Pella.
  • Highly oriented pyrolytic graphite (HOPG) ZYA quality, GRAS/1.0x7x7
  • HOPG Highly oriented pyrolytic graphite
  • Si nitride TEM supports 50 nm silicon nitride film on a 200 pm silicon frame with nine viewing windows, each 0.1 x 0.1 mm) were purchased from Ted Pella.
  • Example 1 Method of preparation of ZIF films according to the invention on 2D substrates Various substrates 2D porous graphite substrates were used as substrates in a method according to the invention. a) Providing a 2D substrate
  • a 2D graphite substrate such as highly-oriented pyrolytic graphite (HOPG) or graphene/Si/SiCb is provided.
  • HOPG highly-oriented pyrolytic graphite
  • Si/SiCb graphene/Si/SiCb
  • the 2D graphite substrate was prepared depending on the envisioned applications. Examples are provided below.
  • a single-layer graphene (SLG) was synthesized by using low-pressure CVD of methane on copper foil following the literature for example as described in Huang et al., 2021, Sci. Adv. 7:eabf0116.
  • the copper foil was annealed at 1077°C in a EE/ Ar atmosphere for 60 min.
  • CO2 (100 mL/min) and H2 (8 mL/min) flow was introduced successively, each for 30 min, to remove the contaminations.
  • CEE (24 mL/min) and H2 (8 mL/min) flow was used to grow single-layer graphene on copper film for 30 min at pressure of 460 mTorr.
  • an O2 plasma cleaner EQ-PCE-3, 13.56 Mhz, 17 W was carried out to introduce nanopores. Briefly, the atmosphere in the plasma chamber was exchanged by O2 flow to pressure around 50 mTorr. Then, a plasma was generated for 4 s to etch SLG to get nanoporous graphene (NG). After the plasma treatment, a solution of Poly(l- trimethylsilyl-l-propyne) (PTMSP) in toluene (1.25 wt%) was spin-coated on NG at 1000 rpm for 30 s and 2000 rpm for 30 s, respectively. After that, the sample was placed in ambient air at room temperature overnight. Then, copper foil was etched by a combination of FeCh (0.5 M in water), HC1 (0.1 M in water) and water. Then, the obtained graphene/PTMSP film is used as a substrate in step b).
  • PTMSP Poly(l- trimethylsilyl-l-propyne)
  • the 2D substrate was then immersed in an ultradilute precursor solution ( ⁇ 2 mM Zn +2 and ⁇ 16 mM 2-methylimidazole (2-mIm), respectively) for a few minutes (Fig. la).
  • an ultradilute precursor solution ⁇ 2 mM Zn +2 and ⁇ 16 mM 2-methylimidazole (2-mIm), respectively
  • Fig. la the 2D graphite substrate was partially immersed.
  • 1 ml of 2-mIm aqueous solution was added. After an incubation time of few minutes, the substrate was removed to stop the reaction.
  • the ZIF films obtained by a method according to the invention were further characterized by various techniques as follows.
  • ZIF films prepared on HOPG prepared as described above were examined by optical and scanning electron microscopy (SEM). A sharp change in contrast was observed at the air/precursor-solution interface beyond which the film had a uniform contrast indicating that the film was smooth, continuous, and macroscopically uniform (Fig. If and 1g).
  • Atomic force microscopy (AFM) imaging near the interface confirmed that the ZIF film is indeed continuous and has a thickness of ca. 2 nm (Fig. 1c and d). 4 and 6 nm thick films were obtained by increasing the growth time from 5 min to 10 and 15 min, respectively (Fig. le). A discrete, 2 nm, increase in film thickness suggests a crystalline order.
  • SEM scanning electron microscope
  • PXRD Powder X-ray diffraction
  • TEM images and selected-area electron diffraction (SAED) images were obtained with a Talos F200X microscope operated at 200 kV.
  • TEM images for patterns on silicon nitride were obtained on a ThermoFisher TF30 TEM operating at 300 kV.
  • AC-HRTEM Low-dose aberration corrected high resolution TEM
  • Cs- corrected FEI G2 Titan 60-300 electron microscope at 300 kV using a Gatan K2 direct-detection camera in electron counting mode.
  • the AC-HRTEM images were acquired with the dose fractionation function, and each image stack is composed of 120 frames with 0.05 s exposure for each frame, with a total electron dose of ⁇ 60 e“A' 2 .
  • the raw image was denoised by using an average background subtraction filter (ABSF).
  • ABSF average background subtraction filter
  • the CTF correction was performed based on the defocus value determined from the amorphous thon rings in the Fourier transform, and the projected electrostatic potential was simulated by the QSTEM software (QSTEM V2, 31).
  • Simulated ED pattern was carried out by using Singlecrystal module of CrystalMaker software.
  • AFM images and modulus measurement were recorded on a Bruker MultiMode 8 AFM.
  • modulus measurement a Bruker Tap525 A rectangular probe was used and calibrated with standard sample sapphire, polystyrene and HOPG.
  • XPS were carried out on an Axis Supra (Kratos Analytical) using the monochromated K x-ray line of an aluminium anode.
  • Synchrotron GIXRD was carried out at beamline BM01, Swiss-Norwegian beamline (SNBL) at the European Synchrotron Radiation Facility (ESRF) with wavelength of 0.683 A.
  • the 2DZIF/graphene/PTMSP film was transferred on Si/SiC>2 wafer with 2DZIF layer facing the wafer. Then, the sample was annealed at 70°C for 4 h, to increase the adhesion between film and Si/SiC>2 wafer. After that, the sample was immersed in toluene for 12 h, to remove PTMSP layer.
  • the AFM image of 2DZIF film with triangular morphology after 5 min of water etching was collected directly on the film with 2DZIF layer facing up.
  • the 2DZIF/graphene/PTMSP film with triangular morphology was first scooped by glass slide with 2DZIF layer facing the slide, and a Si/SiC>2 wafer attached with double-sided carbon tape was pressed onto PTMSP layer.
  • the 2DZIF/graphene/PTMSP film was transferred onto Si/SiC>2 wafer, resulting in 2DZIF layer facing up.
  • AFM measurement of was carried out directly on the sample without any treatment.
  • 2DZIF/graphene/PTMSP film was transferred on TEM grid with 2DZIF layer facing the TEM grid. Then, the sample was annealed at 70°C for 4 h, to increase the adhesion between film and TEM grid. After that, the sample was immersed in toluene for 12 h, to remove the PTMSP layer.
  • Graphene supported ZIF film obtained by a method of the invention could be suspended on a holey transmission electron microscopy (TEM) grid (Fig. 2a) and it appeared that the film was devoid of large crystals and appeared uniform.
  • Selected area electron diffraction (SAED) from a micrometersized area yielded three sets of diffraction patterns (Fig. 2b). The first two sets ((01), highlighted with grey circles) had six-fold symmetry originating from two slightly misoriented (by 3.0°) grains of graphene, while the last set had two-fold symmetry and belonged to a single grain of ZIF (highlighted with white circles), confirming that ZIF prepared on graphene was crystalline.
  • the in-plane GIXRD pattern revealed sharp diffraction peaks, consistent with the peak positions obtained by the radial integration of the SAED pattern (Fig. 2c) confirming that the film formed on the graphitic substrate exhibits crystalline order.
  • the sharpness of the GIXRD peak indicates that the grains were at least 0.1-0.2 pm in size.
  • the presence of the order in the ZIF film when prepared over a graphitic substrate indicates a strong role of epitaxy in the formation of the ordered 2DZIF films.
  • X-ray photoelectron spectroscopy (XPS) of the 2DZIF and aZIF films was carried out to gain further insights into their coordination environments (Fig. 2d).
  • the Nls XPS data of 2DZIF when compared to that of ZIF -L layers (comparative) and a prototypical nonlayered ZIF (ZIF-8) revealed that both 2DZIF and ZIF-L yield two peaks (399.0 and 400.2 eV corresponding to N-Zn and N-H bonds, respectively) in contrast to a single peak (399.0 eV) from the ZIF-8 crystals.
  • N-H abundant surface terminations
  • the population of N-H species was significantly diminished for aZIF indicating a nonlayered amorphous structure.
  • the layer in 2DZIF is composed of alternating 4-member ring (MR) and 6-MR chains while terminal 2-mIm linkers are present on both sides of the layer (Fig. 2e and 3c).
  • the pore aperture of 2DZIF is constituted by the 6-MR and corresponds to a gap of 3.2 A. This value is in between that of ZIF-L (3.0 A) and ZIF-8 (3.4 A).
  • ABC-HRTEM Aberration-corrected high-resolution TEM
  • Fig. 3a highlights the morphological differences in ZIF-L and 2DZIF. While the layers in ZIF-L and 2DZIF are stacked along the c-axis, the former grows as a leaf-shaped layered crystal whereas the latter can form macroscopically uniform monolayer films. The unique leaf shape is formed because ZIF-L layers stack with first progressively increasing and then progressively decreasing lateral size along the b-axis.
  • planar morphology of 2DZIF is determined by its epitaxial relationship with the graphitic lattice with near perfect registry along the b-direction (lattice mismatch of 0.2%) and a mismatch along the a-direction (5.36%, Fig. 3b.
  • This allows unimpeded grain growth of 2DZIF on the graphitic lattice.
  • ZIF-L and 2DZIF have orthorhombic lattices
  • the unit-cell parameters of 2DZIF are distinct from those of ZIF-L where the latter has a significantly shorter parameter along the b (17.060 A) axis (Fig. 3c).
  • the grains of 2DZIF could be visualized by partial etching of 2DZIF films based on the well documented dissolution of ZIFs in water with reaction condition of 0.5 mM Zn 2+ , 4 mM 2-mIm for 4 min (Fig. 3d). After partial dissolution, the grain shape was triangular with a lateral size of 1-2 pm (Fig. 3e) consistent with earlier observations of domains in the sub-monolayer film. The three sides of the triangular grains could be assigned to be (110), (110) and (100) lattice planes, respectively, reported to be the minimum surface energy planes for ZIF layers (Zhu et al., 2017, supra). AFM images (Fig. 3f) confirmed that the grains have uniform thickness of ⁇ ca. 2 nm consistent with the structure of 2DZIF.
  • the 2DZIF film (2DZIF grown on HOPG) was mechanically robust with Young’s modulus of 8.1 ⁇ 2.1 GPa (Fig. 3h & i), comparable to that of the three-dimensional analogs (Tan et al., 2010, PNAS 107, 9938-9943).
  • Example 3 Gas performance of 2DZIF films according to the invention
  • Eb-sieving performance was assayed on 2DZIF films obtained as described in Example 1 using nanoporous graphene (NG) mechanically reinforced with a dense 250-nm-thick polyfl - (trimethylsilyl)propyne] (PTMSP) film where the NG/PTMSP film acts as a 2D substrate (Fig. 4a).
  • the pores in NG were intentionally designed to be large (1.8 ⁇ 1.2 nm) (He et al., 2019, Energy Environ. Sci., 12, 3305-3312) to rule out any molecular sieving from NG and to allow the determination of Fb-sieving from the 2DZIF film.
  • the resulting 2DZIF/graphene/PTMSP film was transferred to substrate (macroporous W support with l-mm 2 -size testing area) for further characterizations or applications.
  • the gas separation performance of the membranes was recorded on a homemade permeation setup.
  • the pressure on the feed side was maintained at 2-8 bar and on the permeate side at 1 bar during the measurements. All measurements were done after reaching the steady state with argon as the sweep gas.
  • the membranes were sealed with stainless-steel gasket.
  • the composition of permeate was analysed using an online Hiden Analytical HPR-20 mass spectrometer.
  • the 2DZIF films resting on the macroporous metal foil support (area of 1 mm 2 ), exhibited a molecular cut-off for molecules larger than H2, indicating that gas transport was controlled by the 6-MR of 2DZIF (Fig. 4b).
  • Centimeter-scale 2DZIF membrane could be also prepared, thanks to the highly uniform deposition of 2DZIF films on graphene (Fig. If and g), which also presents attractive permselective H2 permeance (Fig. 4f & g; Table 2) and H2/N2 selectivity, in agreement with the smaller-area membranes.
  • the resistance (RJ) of gas permeance membrane is defined as,
  • L is the thickness of membrane
  • Pi is permeability of the membrane material to gas i
  • Ji is permeance of the membrane material to gas z
  • A is the effective area of membrane.
  • the 2DZIF membrane is composed of two parts, supportive NG/Teflon layer and selective 2DZIF layer, that means the total resistance (Rtotai) can be expressed as a combination of resistance from supportive NG/Teflon layer, Rapport, and selective 2DZIF layer, R2D/1F,
  • J to tai, Jsupport and J DZIF are permeance of total membrane, support layer and 2DZIF layer, respectively 2 .
  • a 2D film of UiO-66-NH2 was deposited on HOPG (Fig. 5) under the following conditions of 1 mM Zr 4+ , 1 mM BDC-NH2 aqueous solution for 2 min.
  • the film crystallinity is determined by the interaction of molecular precursors during curse of the method of preparation according to the invention and that useful ultrathin amorphous films could be obtained by using an amorphous substrate in a method according to the invention.
  • Ultrathin amorphous ZIF films with controlled thickness could be obtained by liquid phase coating of an amorphous substrate, such as a silicon wafer, in a method according to the invention using dip coating. a) Providing an amorphous substrate
  • a Si/SiC>2 wafer with a 300-nm-thick oxide layer was provided and used as received.
  • amorphous silicon nitride (50-nm thick silicon nitride (SiNx)) was pre-treated with oxygen plasma for 10 min (29.6 W, 400 mTorr oxygen pressure) in a plasma cleaner (Harrick Plasma) to improve the surface reactivity and the pre-treated SiN layer was provided as an electron-beam transparent substrate.
  • a plasma cleaner Hard Plasma
  • the amorphous substrate was then immersed in an ultradilute precursor solution ( ⁇ 2 mM Zn +2 and ⁇ 16 mM 2-methylimidazole (2-mIm), respectively) for a few minutes (Fig. 6a).
  • the substrate was partially immersed in a petri dish containing 29 ml of Zn(NOs)2 aqueous solution at room temperature the amorphous substrate was partially immersed. Then, 1 ml of 2-mIm aqueous solution was added. After an incubation time of 2-15 minutes, the substrate was removed to stop the reaction.
  • the obtained ZIF films are referred to as aZIF. They were characterized by electron and atomic force microscopy. Figure 10 shows one such film with thickness of 14 nm.
  • the ratio of Zn to 2-methylimidazole is about 2.
  • Example 6 Method of preparation of aZIF films using a flow coating device
  • a 1 cm wide silicon wafer is placed in a flow coating device ( Figure 11 (A)).
  • Precursor solutions containing 4 mM Zn +2 and 32 mM 2-mIm are injected into the device separately at flow rate of 2 mL/min, respectively, and mixed by a stir bar at 900 rpm.
  • the mixed solution which contains 2 mM Zn +2 and 16 mM 2-mIm then proceeds to contact and flow over the silicon wafer.
  • the aZIF film is deposited at a rate of about 20 nm/min.
  • the silicon wafer is removed from the device and blown dry with air. The thickness of the film is determined by ellipsometry and AFM (Fig. 11 (B))
  • Example 7 Method of preparation of aZIF films using a spin coating device
  • a 2 cm x 2 cm silicon wafer is placed in a spin coater.
  • the spin speed is set at 500 rpm.
  • Precursor solutions containing 4 mM Zn +2 and 32 mM 2-mIm are fed into the spin coater at a flow rate of 2 mL/min, respectively, and mixed immediately before dropped onto the silicon wafer.
  • the mixed solution is continuously dropped onto the wafer for 2 or 4 min.
  • the films were characterized by electron and atomic force microscopy and their thickness was measured by ellipsometry ( Figure 12).
  • the aZIF film on the amorphous silicon nitride support obtained as described in Example 5 was subsequently exposed to a direct-write electron beam using 1 : 1 line- and space-patterns ranging from 10 to 40 nm in line width (or half pitch) using a Thermo Fisher Helios G4 UC Dual Beam microscope operating at 20 kV accelerating voltage and 400 pA beam current.
  • the areal doses were 80 mC/cm 2 for all patterns (Fig. 8a).
  • a 2DZIF was synthesized on nanoporous graphene (NG)/PTMSP support film ultradilute precursor solution: Zn 2+ : 6.25 mM, bim': 6 mM leading to membrane M8.
  • the obtained 2D ZIF film after a single cycle of deposition according to the invention was characterized by electron diffraction (Fig. 9B).
  • the electron diffraction was collected from a suspended film in transmission electron microscope from an area of 1 micrometer.
  • the resulting pattern constitutes a pattern from a single crystalline grain, indicating that the Zn2(bim)4 film has at least 1 pm sized grain in the lateral (2D) direction. This also confirms the crystallinity of 2D Zn2(bim)4 film.
  • the gas performance was characterized according to Example 3 except that in this case H2 and CO2 were probed (as against H2 and N2). This separation is also challenging and very useful for an important application called precombustion carbon capture for the production of clean H2 from fossil fuel.
  • the aZIF film on the silicon wafer obtained as described in Example 6 was exposed to electron beam using a matrix of 2-pm square patterns with varied dose as indicated in Figure 13, ranging from 2 to 40 mC/cm 2 . After exposure and development in 0.01 M aqueous solution of HC1 or acetic acid for 10 min, followed by blow drying in a stream of nitrogen gas, the irradiated area was preserved depending on the electron dose, while the non-irradiated area was dissolved ( Figure 13), confirming aZIF as a negative-tone resist after development in acidic solutions.
  • Example 11 Development of electron beam patterned aZIF films in basic solutions
  • the aZIF film on the silicon wafer obtained as described in Example 6 was exposed to electron beam using a matrix of 2-pm square patterns with varied dose as indicated in Figure 14, ranging from 2 to 40 mC/cm 2 . After exposure and development in 0.01 M aqueous solution of TPAOH for 10 min and blown dried in a stream of nitrogen gas, it was observed that the irradiated area was preserved depending on the electron dose, while the non-irradiated area was dissolved ( Figure 14), confirming aZIF as a negative-tone resist after development in basic solutions.
  • Example 12 Dry development of electron beam patterned aZIF films
  • the aZIF film on the silicon wafer obtained as described in Example 6 was exposed to electron beam using a matrix of 2-pm square patterns with varied dose.
  • the exposed films were placed in a cylindrical quartz reactor system and transferred to an oven.
  • a vial containing ⁇ 1 mL of Hfac-H was placed outside the oven and connected to the reactor inlet with a manual valve separating the reactor from the etchant.
  • the reactor outlet was connected to a cold trap and vacuum pump with a second manual valve separating the reactor from the vacuum.
  • the system was heated to 120 °C under dynamic vacuum and evacuated for 30 minutes until the system pressure had stabilized (approximately 0.025 mbar).
  • the Hfac-H valve was opened for the desired etching time and the sample was exposed to etchant vapors under static vacuum. Following treatment, the system was evacuated under dynamic vacuum for 30 minutes to remove volatile species. The vacuum was then shut off and the system was allowed to cool to room temperature. After etching experiments, AFM height mapping was performed to evaluate pattern dimensions (Figure 15).
  • Example 13 Positive-tone patterning of aZIF films
  • the aZIF film on the silicon wafer obtained as described in Example 5 was heated in a closed 60 mL PTFE reaction vessel with a bed of 0.1 g 4,5-dichloroimidazole (dclm) at 75°C for 90 min.
  • the dclm treated film is then exposed to 5 keV electron beam at 0.5 mC/cm 2 dose using a dot pattern.
  • the diameter of the dots and the spacing between dots are both 100 nm.
  • the film is immersed in acetone for 10 s and blow dried in a stream of nitrogen gas.
  • the area irradiated by the electron beam is removed after the development, i.e., the metal imidazolate serves as a positivetone resist ( Figure 16).

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Abstract

The invention relates to methods for the preparation of ultrathin metal-organic frameworks (MOFs), in particular Zeolitic imidazolate frameworks (ZIFs) and uses thereof and resulting products thereof, in particular useful for the preparation of gas separation membranes, in particular for H2 sieving.

Description

METHOD OF PREPARATION OF ULTRATHIN METAL-ORGANIC FRAMEWORKS
& USES THEREOF
Statement Regarding Federally Sponsored Research
This application contains an invention which was made with government support under grant DE- SC0021212 awarded by the US Department of Energy. The government has certain rights in the invention.
Field of the Invention
The present invention pertains generally to the field of preparation of metal-organic frameworks (MOFs), in particular Zeolitic imidazolate frameworks (ZIFs) and uses thereof.
Background of the Invention
MOFs are organic-inorganic structures, highly porous structures that are obtained through precisely controlled structures in which two components of metal cations as nodes and organic molecules as bridges have been engineered.
Zeolitic imidazolate frameworks (ZIFs) (Banerjee et al., 2008, Science 319, 939-943; Guillerm et al., 2014, Chem. Soc. Rev. 43, 6141-6172') are nanoporous ordered materials belonging to a class of metal-organic frameworks (MOFs) but exhibiting zeolitic topology and high chemical and thermal stability and that hold promise for applications in molecular separations (Zhou et al., 2018, Sci. Adv. 4:eaaul393; Ma et al., 2018, Science 361, 1008-1011), patterning (Stassen et al. 2013, CrystEngComm, 15, 9308-9311; Miao et al. 2022, Nat. Commun. 13, 420) and sensing (Lu et al., 2010, J. Am. Chem. Soc. 132, 7832-7833). ZIFs are constructed by linking Zn2+ or Co2+ ions with organic imidazolate (Im) linkers. As a result of their microporosity, ZIFs generally exhibit high CO2 uptake, making them suitable for CO2 based gas separation and storage. The presence of organic linkers enables various strategies to fine tune pore size and aperture as well as the pore polarity of ZIFs. Despite the wide variety in unraveled ZIF structures, not many different ZIF types have been applied in MMMs for gas separation.
In particular, low-temperature synthesis and activation, high porosity, and A-scale pore aperture of ZIF make it highly advantageous compared to other nanoporous materials especially for application in membrane-based separations. A-scale biological channels represent the ideal design of selective layer because of their nanometer-scale pathlength (Epsztein etal, 2020, Nat. Nanotechnol. 15, 426- 436).
Their chemical and physical properties have been widely explored as a function of framework flexibility (Moggach et al., 2009, Angew. Chem. Int. Ed. 48, 7087-7089; Knebel et al. 2017, Science 358, 347-351) and structural defects (Bennett et al., 2017, Nat. Chem. 9, 11-16; Babu et al., 2019, Adv. Mater. 31, 1900855).
ZIF-8 is constructed by linking 2-methylimidazolate with Zn2+ metal ions and has a sodalite (SOD) topology containing a cuboctahedral structure (Park, et al., 2006, Proc. Natl. Acad. Set. U. S. A., 103, 10186-10191). Due to this unit cell structure permeation through ZIF-8 can occur in three dimensions. Moreover, the flexibility of the 2-methylimidazolate linkers in the ZIF-8 structure make the framework dynamic, where linker rotation can increase the crystallographic size of the pore aperture from 3.4 A to a dynamic pore aperture of 4.0-4.2 A (Qian et al., 2020, Chem. Rev., 120, pp. 8161-8266). The range of the ZIF-8 pore aperture size lies within the spectrum of the kinetic diameters of several industrial relevant gases, such as CO2 (3.3 A), N2 (3.64 A) and CH4 (3.8 A), which can be regarded as the main motivation for the use of ZIF-8 in mixed matrix membranes (Essen et al., 2020, Separation and Purification Technology 260, 1, 118103).
Amorphous MOFs exhibit unique physical and chemical properties due to the absence of anisotropy and crystalline grains (Bennett et al., 2018, Nat. Rev. Mater. 3, 431-440). They are especially attractive for lithographic patterning because of their improved homogeneity and processability compared to their polycrystalline counterparts.
Numerous strategies for generating thin MOF coatings onto the supporting substrates had been developed (Crivello et al., 2021, Mater. Horiz. 2021,8, 168 178) which cand be categorized into two strategies: direct and indirect Zhang et al., 2022, ACS Omega, 7 (21), 17765-17773). In the direct strategy, the MOF coating is in situ settled on the supporting substrates during MOF formation. In the indirect strategy, MOF coatings were obtained by launching the supporting substrate with the as-prepared free-standing MOF film, which was synthesized at the liquid-liquid or liquid-air interface (Bai et al., 2018, ACS Appl. Mater. Interfaces, 10, 25960-25966). The preparation of ultra-thin “defect-free” ZIF-8 on a wide range of unmodified supports (porous polyacryalonitrile, anodized aluminum oxide, metal foil, porous carbon ad graphene) by eletrophoretic nuclei assembly for crystallization of highly intergrown thin-films (ENACT) approach has been described (WO 2019/186134) but the obtained MOF films were rather thick (e.g. 300-500 nm), hosting three-dimensional (3D) grains. The resulting film had a flexible lattice framework, from the flip-flop motion of the organic linker (Zhang et al., 2012, J. Phys. Chem. Lett., 3, 2130), which limited H2/N2 selectivity.
In spite of the variety of the proposed strategies, several obstacles remain on the way to MOFs industrial applications, for example, poor processability in hydro-/solvothermal, expensive equipments required in electrochemical deposition, time consuming in stepwise method, specific substrate designed to direct the growth of MOF crystals in epitaxial growth. Recently, a new strategy was developed in an attempt to achieve MOF coatings independent from the substrates through the treatment of substrates with polyelectrolyte multilayers of polydimethyldiallyl ammonium chloride (PDDA), and tannic acid (TA) (Zhang et al., 2022, supra). However, the resulting layers are quite thick (2 pm), which limits the gas permeance.
The realization of two-dimensional (2D) ZIF films with thickness down to that afforded by a single structural building unit is highly desired to make ZIF analogues to graphene and related 2D materials with an added advantage; the intrinsic nanoporosity of ZIF can be used to separate molecules while maximizing the permselective flux (Gascon et al., 2010, Angew. Chem. Int. Ed. 49, 1530-1532) and offer promising possibilities for removal of various environmental pollutants such as noxious gases, organic pollutants, heavy metals and radionuclides on ZIFs (Sun etal, 2022, Environ. Sci.: Nano, in press).
Another highly desirable feature is a nanometer-scale control over the film thickness which can allow one to fabricate nanoscale patterns. However, the realization of 2D crystalline and ultrathin amorphous ZIF films has remained elusive. While layered ZIFs such as ZIF-L (Chen et al. 2013, Chem. Commun., 49, 9500-9502), Zn2(bim)4 (Peng, et al., 2014) and analogs (Science 346, 1356- 1359; Peng et al., 2017, Angew. Chem. 129, 9889-9893) have been reported, the individual ZIF layers in these materials have a small aspect ratio (100) which prevents the realization of continuous 2D ZIF films over a macroscopic length scale. The state-of-the-art of ZIF deposition methods yield poly crystalline films with thickness larger than 100 nanometers (He et al., 2018; Adv. Funct. Mater., 28, 1707427; Wei et al., 2020, Adv. Funct. Mater., 30, 1907089). This is mainly due to difficulty in achieving in-plane film growth without film thickening.
Therefore, the development of new methods of fabricating MOF films (e.g. ZIF films), in particular 2D ZIF films in a precisely and controlled manner is highly attractive in view of the large-scale deployment of various possible applications for those materials that has been hampered so far by the above-described technical limitations.
Summary of the Invention
The present invention is based on the unexpected finding of a process that allows obtaining macroscopically uniform ultrathin amorphous MOF films, in particular two-dimensional (2D) ZIF (2DZIF) films on graphitic substrates, with thickness down to that of a single structural building unit (2 nm), the smallest structural repeating unit, with record high permselective H2 flux. It was unexpectedly found that the provision of a film having a thickness of the smallest height needed to be ordered leads to 2DZIF films with a rigid lattice framework that allows achieving efficient H2/N2 selectivity. The method of the invention allowed to obtain a structure of 2DZIF having unique crystallographic lattice parameter not reported before, e.g., a = 24.196 A, b = 19.719 A, c = 20.908 A. This also resulted in narrower pores than any known ZIFs suitable for hydrogen separation. The unique lattice parameter which can be obtained is due to registry of the 2DZIF to the underlying graphitic substrate. The lattice registry refers to an excellent match between the lattice parameters of 2DZIF and a supercell of graphene which maximizes the interaction of 2DZIF with graphene lattice favoring the growth of 2DZIF on graphene. The lattice registry also makes the lattice framework of 2DZIF rigid, allowing to realize a large H2/N2 selectivity.
A general object of this invention is to provide an efficient method of preparation of macroscopically uniform ZIF films with a nanometer-scale control over the film thickness.
One of the specific objects of this invention is to provide an efficient method of preparation of 2D ZIF films under a fully controlled growth process with a resolution of a single layer.
It is advantageous to provide a method of preparation of 2D ZIF film which allows the formation of such films with a homogeneous thickness over a large area in a time efficient manner.
It is advantageous to provide a method of preparation of ultrathin (e.g., from about 2 nm to about 20 nm) 2D ZIF films on graphitic substrates and related 2D materials for membrane applications.
It is advantageous to provide a method of preparation of ultrathin ZIF films which allows a precise precisely control of the desired film thickness and properties.
It is advantageous to provide a method of preparation of ZIF films allowing preventing homogeneous nucleation in the bulk solution and promoting heterogeneous nucleation on the substrate surface.
It is advantageous to provide a method of preparation of MOF, in particular, ZIF films at room temperature.
It is advantageous to provide a method of preparation of MOF, in particular, ZIF films presenting a high mechanical strength.
Objects of this invention have been achieved by providing a method for the preparation of a porous metal-organic framework according to claim 1. Disclosed herein is a method for the preparation of a MOF coated 2D substrate comprising the steps of: a) Providing a 2D substrate; b) Providing an ultra-diluted MOF metal precursor solution, wherein said an ultra-diluted MOF metal precursor solution contains < 20 mM of metal ions and < 40 mM organic ligand, in particular < 10 mM of metal ions and < 20 mM organic ligand and more particularly < 2 mM of metal ions and < 16 mM organic ligand; c) contacting the said substrate with the ultra-diluted MOF metal precursor solution for about 2 to about 30 min (e.g., 2 to 20 min or 2 to 15 min), for example by fully or partially immersing said substrate in said precursor solution or by flowing the said precursor solution over the substrate; d) removing the obtained MOF coated substrate from the precursor solution, wherein the MOF coated substrate comprises a MOF layer from about 2 to about 20 nm coated on said substrate.
In an advantageous embodiment, the obtained product in the form of ZIF coated graphene substrate is used for preparing a gas filter.
It is advantageous to provide a gas selective membrane combining high H2 flux (typically higher than 1 mol m'2 s'1) and H2/N2 separation factor (typically higher than 20).
Objects of this invention have been achieved by providing a graphitic substrate coated with two- dimensional crystalline ZIF (2DZIF) film according to claim 16 or 17.
Objects of this invention have been achieved by providing a gas selective separation filter according to claim 18 or 19.
Objects of this invention have been achieved by providing a use of a gas selective filter according to claim 20.
Objects of this invention have been achieved by providing an amorphous substrate coated with an amorphous ZIF (aZIF) film according to claim 21.
Objects of this invention have been achieved by providing a use of an amorphous porous substrate coated with amorphous ZIF (aZIF) film according to claim 22.
Also disclosed herein is a graphitic substrate coated with a two-dimensional crystalline ZIF (2DZIF) film, wherein the said film’s thickness is from about 2 nm to about 20 nm (e.g., about 2 nm) and the film’s pore density from about 10 to about 60%, in particular 30% to about 60% (e.g., Also disclosed herein is a gas selective filter wherein the graphene membrane is made with a method according to the invention.
Also disclosed herein is a use of a gas selective filter comprising a membrane for gas separation, in particular for separating H2 from N2 and CH4.
In an advantageous embodiment, the H2 permeance of the gas filter is from about 2’000 GPU to about 20’000 GPU, namely from about 7.7 x 10'7 to about 7.7 x 10'6 mol m'2 s'1 Pa'1 (e.g., 6 x 10'6 mol m'2 s'1 Pa'1 at 25°C under 2 bar).
In an advantageous embodiment, the H2/N2 selectivity of a gas filter according to the invention is higher than 20, in particular from 20 to about 117 (e.g., from about 25 to 70) at 25°C under 2 bar.
In an advantageous embodiment, the gas filter according to the invention according to the invention exhibits high permselective H2 flux.
Also disclosed herein is a method for the preparation of a MOF coated on amorphous substrate comprises the steps of a) Providing an amorphous substrate; b) providing a MOF metal precursor solution, wherein said MOF metal precursor solution contains < 20 mM of metal ions and < 200 mM organic ligand, in particular contains < 10 mM of metal ions and < 40 mM organic ligand and more particularly < 2 mM of metal ions and < 16 mM organic ligand; c) contacting the said substrate with the MOF metal precursor solution for about 2 to about 30 min (e.g., 2 to 20 min or 2 to 15 min), for example by fully or partially immersing said substrate in said precursor solution or by flowing the said precursor solution over the substrate; d) removing the obtained amorphous MOF coated substrate, wherein the amorphous MOF coated substrate comprises a MOF layer from about 2 to about 1’000 nm coated on said amorphous substrate.
Amorphous films can be deposited under ultra dilute conditions as described for obtaining crystalline MOFs but also at higher concentrations.
Also disclosed herein is an amorphous porous substrate coated with an amorphous ZIF (aZIF) film, wherein the said film’s thickness is from about 8 nm to about 20 nm (e.g., about 10 nm).
Also disclosed herein is an amorphous porous substrate coated with an amorphous ZIF (aZIF) film, wherein the said film’s thickness is from about 8 nm to about 30 nm or more depending on the deposition time and the number of coatings used to deposit the aZIF film on the substrate. In an advantageous embodiment, the obtained product in the form of a ZIF coated non-porous substrate is used in imprinting or lithographic patterning processes (e.g., generating a patterned aZIF coating on substrates).
Also disclosed herein is a miniaturized catalytic, sensing, luminescent or biomedical (e.g. microfluidic or lab-on-a-chip device) device comprising an amorphous ZIF (aZIF) film according to the invention.
Also disclosed herein is a method is provided for patterning a thin MOF film on a substrate.
According to another particular aspect, the aZIF films may be converted to crystalline ZIFs upon exposure to imidazole ligands or vapors of organic solvents, e.g. ethanol or DMF.
According to a particular aspect, the method reported here will likely accelerate the development of 2D crystalline and ultrathin amorphous MOF films for applications ranging from separation membranes to patterning.
Other features and advantages of the invention will be apparent from the claims, detailed description, and figures.
Brief Description of the drawings
Figure 1 illustrates the synthesis ZIF films from ultra-dilute solutions as described in Example 1. a: Schematic representation of the formation of a ZIF film on a substrate, b: Composition diagram comparing the precursor solution composition used in the method of the invention with those reported in the literature (as detailed in Table 1). AFM (c) and the corresponding height profile (d) of a monolayer ZIF film on HOPG. e: Monolayer and multilayer ZIF films on HOPG with discrete thicknesses as a function of synthesis time. Error bars in this figure represent the standard deviation of measurement, f and g, Optical and SEM images of 2DZIF film on graphene/Cu foil, respectively, while SEM image was created from combining 43 * 42 = 1806 images by scanning the whole surface of the sample.
Figure 2 presents the structure determination of 2DZIF films as described in Example 2. a: Bright- field TEM image of the 2DZIF film supported on suspended graphene, and (b) its corresponding SAED pattern. The pattern from graphene is identified with green circles and those from 2DZIF with white circles, c: In-plane GIXRD data from a 2DZIF film (middle) prepared on graphene/Si/SiO2 along with a radially integrated trace (bottom) of the SAED pattern shown in (b). d: Nls XPS spectra from ZIF-8, ZIF-L (comparative, not from the invention) and 2DZIF films. The N-Zn and N-H coordination environments are shown on the right, e: DFT-relaxed structure of the 2DZIF and a visualization of the 6-member-ring (6-MR) and its 3.2 A gap. f: HRTEM image of the 2DZIF film lying flat on the hkO plane, resting on suspended graphene, and (g) corresponding Fourier transform compared with the simulated diffraction pattern from the proposed structure oriented along the c-out-of-plane direction, h: Left: CTF-corrected image of the highlighted area in (f) based on a defocus value of -130 nm analysed from the Thon rings in the Fourier transform pattern. Right: simulated projected potential map along the [001] direction of 2DZIF.
Figure 3 presents the characterization of the 2DZIF structure as described in Example 2 and its relationship with comparative ZIF-L. a: Schematic contrasting the arrangement of layers within a ZIF-L crystal with that of a monolayer 2DZIF according to the invention, b: Epitaxial relationship between the graphene lattice and 2DZIF. c: Structures of a 2DZIF layer according to the invention (left) and ZIF-L (right) viewed along the [001], [100], and [010] directions, d: Schematic illustration of the etching of 2DZIF in water. SEM (e) and AFM (f) images of the triangular grains of 2DZIF obtained by a short etching in water, g: AFM height profile corresponding to the line in (f); AFM image (h) and corresponding modulus map (i) of 2DZIF synthesized on HOPG.
Figure 4 represents possible applications of 2DZIF obtained by a method of the invention, a: Schematic of a 2DZIF film supported on nanoporous graphene (NG) reinforced with PTMSP. b: EE, CO2, N2 and CH4 permeances of the PTMSP/NG support and the supported 2DZIF film on PTMSP/NG. c: 2DZIF membrane separation performance for an equimolar H2/N2 mixed feed, d: Comparison of the H2/N2 separation performance of 2DZIF membranes with the state-of-the-art membranes (as detailed in Fig. 4e). GO, CMP, and HOF refer to graphene oxide, conjugated microporous polymers and hydrogen-bonded organic frameworks, respectively, e: Gas permeance and ideal selectivity of a film of the invention compared to the state of the art in the literature; f: Optical photo of 1 cm scale 2DZIF membrane in module and (g) its schematic structure.
Figure 5 presents the synthesis MOF films from ultradilute solutions according to a method of the invention as described in Example 4. a: Structure of the metal-organic framework U1O-66-NH2; b: SEM image of U1O-66-NH2 film synthesized on HOPG; c: AFM image and corresponding height profile for UiO-66-NH2 film synthesized on HOPG. (e) and (f) Bright-field TEM image of the UiO- 66-NH2 film supported on suspended graphene and its corresponding SAED pattern, where grey and white circles are presenting diffraction from graphene and U1O-66-NH2, respectively.
Figure 6 illustrates the synthesis ZIF films on Si/SiO2 as described in Examples 5 and 6 from ultradilute solutions, a: SEM and optical images of a ZIF film on Si/SiO2. b: AFM and the corresponding height profile (c) of the ZIF film on Si/SiO2; d: Ellipsometry of several ZIF films on Si/SiO2 wafer. Figure 7 presents the structure determination of aZIF films as described in Example 8. a: In-plane GIXRD data from an aZIF film prepared on Si/SiC>2; b): Nls XPS spectra from aZIF. The N-Zn and N-H coordination environments are shown on the right.
Figure 8 represents possible applications of aZIF obtained by a method of the invention, a: Schematic of the negative tone patterning process, where the electron beam irradiated regions remain while the non-irradiated regions are removed in the development step using water. TEM (b) and AFM (c) images of nanoscale patterns made on an aZIF film, d: AFM height profile corresponding to the line in (c).
Figure 9 represents the synthesis of another 2DZIF film using Zn as the metal and benzimidazole (Bim) as the linker with composition of Zn2(Bim)4 according to the invention on 2D substrates using another ultradilute precursor solutions as described in Example 9. A: schematic representation of the range of compositions of the ultradilute precursor solutions where 2D film can be successfully grown according to a method of the invention. B: electron diffraction pattern from the 2D Zn2(Bim)4 film showing single crystal diffraction. C: average of H2/CO2 separation properties (H2 permeance and H2/CO2 selectivity) from the 2D Zn2(Bim)4 film, depending on the number of cycles of deposition (one cycle and five cycles).
Figure 10 represents the characterization of dip coated films as described in Example 5. A: SEM and optical micrographs of amorphous ZIF film on a silicon wafer; the area that was immersed in the solution and was coated with amorphous ZIF is on the right and is marked ’’aZIF”; B: Atomic force microscopy (AFM) image height image of an amorphous ZIF film deposited on a silicon wafer. C: the height profile measured across the deposition boundary indicating a film thickness of 14 nm.
Figure 11 illustrates the preparation of flow-coated films as described in Example 6. A: Photograph (top) and drawing (bottom) of the flow coating device. The two solutions are introduced from the left side of the device and are mixed in the chamber containing the stirrer (the stirrer color is blue), and then they flow over the substrate under laminar flow. B: Flow coated films, with the coating time indicated above each wafer (2, 4, 6, 8 min) and the thickness measured by ellipsometry indicated under each wafer (66, 148, 215, 266 nm).
Figure 12 illustrates the preparation of spin-coated films as described in Example 7. Optical image (A) and AFM (B) of aZIF films deposited on silicon wafers in a spin coater at spin rate of 500 rpm for 2 and 4 min. The thickness measured from ellipsometry are 96 and 204 nm for the 2 and 4 min coated films, respectively. Figure 13 illustrates aZIF film patterned by a 5 keV electron beam using 2-pm squares of different doses, as indicated in units of mC/cm2 (A) followed by development in acidic solutions as described in Example 10, in 0.01 M aqueous solution of acetic acid (B) or HC1 (C) for 10 min.
Figure 14 illustrates aZIF film patterned by a 5 keV electron beam using 2-pm squares of different doses, as indicated in units of mC/cm2 (A) followed by development in basic solutions as described in Example 11, in 0.01 M aqueous solution of TPAOH (B) for 10 min.
Figure 15 illustrates aZIF film patterned by a 5 keV electron beam using squares of different doses, followed by dry development using hfac-H at 120°C for 10 min as described in Example 12. The electron dose for each 2 pm square in unit of mC/cm2 is indicated in the schematic above the AFM images. The three columns correspond to dose ranges of 0.125-2.5, 0.5-10 and 2-40 mC/cm2 from left to right, respectively.
Figure 16 illustrates positive tone patterning of a aZIF as described in Example 13. AFM image (A) and the corresponding height profile (B) of aZIF film patterned in the positive tone mode. The aZIF film is first treated with the vapor of dclm at 75°C for 90 min, followed by patterning with 5 kV, 0.5 mC/cm2 electron beam using a dot pattern of 100 nm diameter and 100 nm spacing, and subsequently immersed in acetone for 10 s to remove the irradiated area.
Detailed description of embodiments of the invention
The expression “MOF” or “Metal organic framework” refers to uniform structured porous materials fabricated by linking inorganic and organic units by strong bonds (reticular synthesis) which consist in of metal ions or clusters coordinated to organic ligands to form one-, two-, or three-dimensional structures. The organic ligands included are sometimes referred to as "struts" or "linkers”. The choice of metal and linker dictates the structure and hence properties of the MOF. For example, the metal's coordination preference influences the size and shape of pores by dictating how many ligands can bind to the metal and in which orientation. To describe and organize the structures of MOFs, a system of nomenclature has been developed and subunits of a MOF, called secondary building units (SBU), can be described by topologies common to several structures. Each topology, also called a net, is assigned a symbol (Seidi et al., 2020, Materials (Basel).13(12): 2881; Furukawa et al., 2013, Science 341:1230444). For example, a Zr-MOF, UiO-66 is a coordination polymer». The monomers, AKA “building blocks”, are bdc and ZreO4 (OH)4 clusters. UiO-66 is the progenitor of a family of zirconium-based MOFs: the same ZreO4 (OH)4 clusters found in UiO- 66 serve as SBUs for a whole class of materials displaying a wide range of topologies, accessible by employing linkers having specific geometrical and symmetrical features. For example, Zeolitic imidazolate frameworks (ZIFs) is a subclass of MOFs, formed in zeolite topologies with metal ions and imidazolate ligands and ZIF-8 is a Zn-Based MOF. Another example is UiO-66, a zirconium(IV)-based MOF, has an exceptional chemical and thermal stability attributing to a high coordination number (12) of the [Zr6(p3-O)4(g3-OH)4] core with bidentate benzene-1,4- dicarboxylic acid (BDC) ligand.
The expression “2D substrate” refers to a 2D materials, including graphitic substrates and hexagonal boron nitride (A-BN), M0S2, and the like.
Porosity of 2D materials can be measured in a standard manner by transmission electron microscopy-based imaging.
The expression “graphitic substrate” stands for graphitic-like material, namely atomically-smooth crystalline substrate which includes graphite and its derivatives such as highly-oriented pyrolytic graphite (HOPG) or graphene or porous graphene substrates. According to another aspect, it also includes other two-dimensional materials (e.g., M0S2, A-BN, etc.).
HOPG is a highly pure and ordered form of synthetic graphite characterized by a low mosaic spread angle, meaning that the individual graphite crystallites are well aligned with each other. The best HOPG samples have mosaic spreads of less than 1 degree.
The expression “amorphous substrate” refers to any material without any crystallographic order at its surface. It includes Si/SiO2 wafers, amorphous SiN, glass, amorphous ceramics and the like.
The expression “MOF metal precursor solution” comprises metal ions such as Zn2+ or Co2+ or Zr+4, an organic ligand such as 2-methylimidazole or imidazole, or benzimidazole or 2-ethylimidazole or purine or benzene- 1,4-dicarboxylic acid, and a solvent such as water. The choice of the metal ion and organic ligand depends on the nature of the MOF to be obtained and can be easily selected in the literature (Seidi et al., 2020, Materials.13(12): 2881).
The term “photomask,” refers to a prepatterned stencil that allows either light or electrons to pass through onto the resist only where the defined pattern is.
The term “resist” is used herein to refer to a thin photosensitive layer used to transfer circuit patterns to the surface of a substrate on which the resist is deposited.
Referring to the figures, in particular first to Fig. la, is provided an illustration of a method of preparation of a MOF coated on a 2D substrate according to an embodiment of the invention. The illustrated method generally comprises the steps of: a) Providing a 2D substrate; b) providing an ultra-dilute MOF metal precursor solution, wherein said an ultra-diluted MOF metal precursor solution contains < 20 mM of metal ions and < 40 mM organic ligand, in particular < 10 mM of metal ions and < 20 mM organic ligand and more in particularly < 2 mM of metal ions and < 16 mM organic ligand; c) contacting the said substrate with the ultra-diluted MOF metal precursor solution for about 2 to about 30 min (e.g., 2 to 20 min or 2 to 15 min), for example by fully or partially immersing said substrate in said precursor solution or by flowing the said precursor solution over the substrate; c) removing the obtained MOF coated 2D substrate from the precursor solution, wherein the MOF coated 2D substrate comprises a MOF layer from about 2 to about 20 nm coated on said 2D substrate.
According to a particular aspect, the 2D substrate is a porous 2D substrate with a porosity from about 0.1 to about 30% and a thickness from about 0.3 to about 1 nm.
According to a particular aspect, the 2D substrate is a porous 2D substrate with pore size from about 0.3 to about 5 nm.
According to a particular aspect, the 2D substrate is a 2D porous graphite substrate with a porosity about 5 to about 20% (e.g., from about 10 to about 18 %) and thickness of about 0.3 to about 1.0 nm (e.g., 0.3 nm).
According to another particular aspect, the 2D porous substrate is a HOPG substrate, for example with a thickness about 1 mm.
According to another particular aspect, the 2D porous substrate is a 2D porous graphite substrate mechanically reinforced with a porous polymeric film (e.g., PTMSP or Teflon AF layer of about 50 to 1000 nm) or nanoporous carbon film with thickness of 100 to 1000 nm.
According to a particular aspect, the metal-organic framework is a ZIF, in particular a Zn-based MOF.
According to another particular aspect, the metal-organic framework is a Zr-MOF, in particular UiO-66.
According to a particular aspect, the said substrate is fully or partially immersed in the ultra-diluted MOF metal precursor solution for about 2 to about 30 min (e.g., 2 to 15 min).
According to another particular aspect, is provided as method of the invention for the preparation of a two-dimensional crystalline ZIF (2DZIF) film on a 2D substrate, wherein ultra-dilute MOF metal precursor solution contains < 10 mM of metal ions and < 20 mM organic ligand. According to another particular aspect, is provided as method of the invention for the preparation of a two-dimensional crystalline ZIF (2DZIF) film on a 2D substrate, wherein ultra-dilute MOF metal precursor solution contains < 10 mM of metal ions and < 11 mM organic ligand.
According to another particular aspect, the metal-organic framework is a ZIF and the MOF metal precursor solution contains < 20 mM of Zn2+ and < 40 mM 2-methylimidazole (2mlm).
According to a particular aspect, the said substrate is exposed to a flowing solution containing metal ions and imidazolate ligands for about 2 min to about 30 min or up to any desired time depending on the target thickness; the longer the coating time, the thicker the deposit.
According to another particular aspect, the metal-organic framework is a ZIF and the ultra-diluted MOF metal precursor solution contains < 2 mM of Zn2+ and < 16 mM 2-methylimidazole (2mlm).
According to another particular aspect, the ultra-diluted MOF metal precursor solution contains from about 0.5 to about 2 mM of Zn2+ (e.g., from about 1 to about 2 mM of Zn2+).
According to another particular aspect, the ultra-diluted MOF metal precursor solution contains from about 4 to about 16 mM 2-methylimidazole (e.g., from about 8 to about 16 mM 2- methylimidazole).
According to another particular embodiment, the metal-organic framework is a ZIF and the ultradiluted MOF metal precursor solution contains < 20 mM of Zn2+ and < 20 mM benzimidazole (BIm), in particular contains < 10 mM of Zn2+ and < 11 mM benzimidazole (BIm).
According to another particular aspect, the ultra-diluted MOF metal precursor solution contains from about 1 to about 20 mM of Zn2+ (e.g., from about 5 to about 10 mM of Zn2+).
According to another particular aspect, the ultra-diluted MOF metal precursor solution contains from about 1 to about 10 mM benzimidazole (e.g., from about 3 to about 7 mM benzimidazole).
The thickness of the MOF film depends on two parameters: concentration of precursor solution as well as deposition time and can therefore be adjusted by varying those parameters in the frame of the present invention.
According to a particular aspect, the porous substrate is immersed in the ultra-diluted MOF metal precursor solution from 1 to about 10 minutes (e.g., about 2 to about 5 minutes).
According to a particular aspect, the MOF coated substrate according to the invention comprises a MOF layer from about 2 to about 10 nm coated on said substrate According to a particular embodiment, the obtained MOF coated 2D substrate obtained from step d) can be further submitted to one or more (e.g., 1 to 4 further cycles of steps b) to c)) to achieve repeated depositions through the immersion in the ultradiluted precursor solution. Typically, the thickness obtained for 2 cycles (2 layers) is about 4 nm and about 10 nm for 5 cycles.
According to a particular aspect, a method according to the invention allows the preparation of a MOF, in particular a ZIF film under epitaxial condition, i.e. where the deposited film takes on a lattice structure and orientation identical to those of the substrate.
According to a particular aspect, the resulting 2D ZIF coated porous graphene substrate is used for preparing a gas filter.
According to a particular aspect, is provided a graphitic substrate coated with two-dimensional crystalline ZIF (2DZIF) film, wherein the said film’s thickness is from about 2 to about 20 nm (e.g., from about 2 to about 18 nm, such as from about 2 to about 10 nm) and the film’s pore density from about 30 to about 60% (e.g., 50 %).
According to a particular aspect, is provided a graphitic substrate coated with two-dimensional crystalline ZIF (2DZIF) film, wherein the structure of 2DZIF has the following crystallographic lattice parameter a = 24.196 A, b = 19.719 A, c = 20.908 A.
According to a particular aspect, is provided a graphitic substrate coated with two-dimensional crystalline ZIF (2DZIF) film according to the invention, wherein the size of the pores of the ZIF film is from about 0.25 to about 1 nm, preferably from about 0.3 to about 0.4 nm.
According to a particular aspect, is provided a graphitic substrate coated with two-dimensional crystalline ZIF (2DZIF) film, wherein the crystalline structure comprises a pore aperture made of a six-membered zinc-imidazolate coordination ring with an effective van der Waals gap of about 3.2 A estimated by a crystallography software (Diamond).
According to a particular aspect, is provided a gas selective filter wherein the graphene membrane is prepared with a method according to the invention.
According to a particular aspect, is provided a gas selective filter comprising a porous graphitic substrate coated with two-dimensional ZIF (2DZIF) film according to the invention.
Also disclosed herein is gas selective filter selecting Ft from N2 comprising an assembly of graphene membranes according to the invention.
Also disclosed herein is a use of a gas selective filter comprising a membrane for gas separation, in particular for separating H2 from N2. In an advantageous embodiment, the H2 permeance of the gas filter is from about 15’000 GPU to about 20’000 GPU, namely from about 50.2 x 10'7 to about 7.7 x 10'6 mol m'2 s'1 Pa'1 (e.g., 6 x 10" 6 mol m'2 s'1 Pa'1) at 25°C under 2 bar.
In an advantageous embodiment, the H2/N2 selectivity of a gas filter according to the invention is from about 50 to about 70 at 25°C.
According to another aspect, is provided an illustration of a method of preparation of a MOF coated on an amorphous substrate according to an embodiment of the invention. The illustrated method generally comprises the steps of: e) Providing an amorphous substrate; f) providing a MOF metal precursor solution, wherein said MOF metal precursor solution contains < 20 mM of metal ions and < 200 mM organic ligand, in particular contains < 10 mM of metal ions and < 40 mM organic ligand and more in particular < 2 mM of metal ions and < 16 mM organic ligand; g) contacting the said substrate with the MOF metal precursor solution for about 2 to about 30 min (e.g., 2 to 20 min or 2 to 15 min), for example by fully or partially immersing said substrate in said precursor solution or by flowing the said precursor solution over the substrate; h) removing the obtained amorphous MOF coated substrate, wherein the amorphous MOF coated substrate comprises a MOF layer from about 2 to about 1,000 nm coated on said amorphous substrate.
According to another particular aspect, the substrate is a silicon wafer.
According to a particular aspect, the amorphous substrate is a Si/SiO2 wafer.
According to another particular aspect, the substrate is a SiNx thin membrane.
According to a particular aspect, the said substrate is first contacted with a source of diluted metal ion such as Zn2+ (e.g. Zn(NOs)2) and then the diluted organic ligand is added to the solution to form the ultra-diluted MOF metal precursor solution.
According to a particular aspect, the contacting is performed using two streams of solutions, 1 and 2, that are mixed before contacting the substrate to form an ultra-diluted MOF metal precursor solution, where stream 1 containing the solution of the metal ions, and stream 2 containing the solution of the ligand. According to another particular aspect, the contacting step is performed in a flow coating or spin coating device where the mixing of the two streams of solutions is accomplished immediately before the fluid contacts the substrate.
According to another particular aspect, the said substrate is contacted with the ultra-diluted MOF metal precursor solution in a spin coater.
According to another particular aspect, the said substrate is contacted with the ultra-diluted MOF metal precursor solution in a flow coater.
According to another particular aspect, the ultra-diluted MOF metal precursor solution contains from 0.25 to 32 mM of metal ions (e.g. 4 mM).
According to another particular aspect, the ultra-diluted MOF metal precursor solution contains from about 4 to 400 mM of 2-methylimidazole (e.g., 32 mM 2-methylimidazole).
Also disclosed herein is an amorphous substrate coated with an amorphous ZIF (aZIF) film, wherein the said film’s thickness is from about 2 to 20 nm, in particular, 8 nm to about 20 nm (e.g., about 10 to 19 nm).
According to another particular aspect, is provided a method for providing an amorphous ZIF (aZIF) film, wherein the imidazolate is a derivative of l,3-diazacyclopenta-2,4-diene having a chemical C3N2HR3, wherein the R groups are positioned at the 1, 4, and 5 positions of 1,3- diazacyclopenta-2,4-diene and are each independently selected from -H, -CH3, -CH2CH3, -Cl, -Br, -I, -C4H4, and -CHO.
According to a further particular embodiment, the imidazolate is selected from: and combinations thereof.
According to another particular aspect, a method is provided for providing an amorphous ZIF (aZIF) film, wherein the metal ion is one of Zn+2, Co+2/+3, In+3, or mixtures thereof. According to another particular aspect, a method is provided for patterning a thin ZIF film on a substrate, the method comprising:
(a) providing a substrate coated with an amorphous ZIF (aZIF) film according to the invention;
(b) loading said substrate coated with said film into an ultra-high vacuum (UHV) chamber; and
(c) patterning the said film of the coated substrate with direct write patterning, maskless patterning, or shadow mask patterning, wherein said thin film has a thickness from 8 nm to 1,000 nm.
According to another further particular aspect, is provided a method for patterning a thin film according to the invention, wherein the patterning further comprises irradiating the thin film with an electron source, an X-ray source, a deep ultraviolet, an extreme ultraviolet source, or other radiation source capable of producing secondary electrons.
According to another further particular aspect, the electron beam has an acceleration voltage with a range from about 2keV to about 100 keV.
According to another further particular aspect, the electron beam has a current with a range from about 6.3 pA to about 1.2 nA.
According to another further particular aspect, the electron beam has a dosage with a range from about 0.01 mC cm'2 to about 50 mC cm'2.
According to another particular aspect, is provided a method for etching a thin film on a substrate, wherein the thin film comprises a thin film of an amorphous ZIF (aZIF) film according to the invention, the method comprising contacting the film with an etching solution.
According to another particular aspect, the etching solution is an acidic solution.
According to another particular aspect, the etching solution is a basic solution.
According to another particular aspect, the etching solution is water, methanol, ethanol, DMF, HC1, acetic acid, solutions of NaOH, KOH, TMAOH, TEAOH, TPAOH, or TBAOH in water or mixtures thereof.
According to another particular aspect, is provided a method for etching a thin film on a substrate, wherein the said film is contacted with the etching solution for a period of time between about 1 minute and about 24 hours, at temperature from room temperature to about 60°C. According to another particular aspect, is provided a method of developing a patterned thin film on a substrate, wherein the patterned thin film comprises a thin amorphous ZIF (aZIF) film according to the invention, patterned by any of the methods described therein, followed by liquid-etching using any of the methods to form a patterned deposit as described herein.
According to another particular aspect, is provided a method for dry etching a thin film on a substrate, wherein the thin film comprises a thin film according to the invention, the method comprising contacting the thin film with a volatile etchant in a closed reactor to produce a volatile organometallic product and an organic product described by the formula A+ B => C + D where A represents the metal/ligand containing film, B represents a volatile etchant, C represents a volatile coordination complex formed by the etchant and the metal, and D represents the volatile ligand originally contained in the film. After etching, the film is purged with an inert gas and removed from the reactor.
According to a further particular aspect, is provided a method for etching a thin film on a substrate, wherein a vapor-phase etchant is contacted with the film.
According to a further particular aspect, is provided a method for etching a thin film on a substrate, wherein the etchant B comprises one or more P-diketonates.
According to a further particular aspect, the one or more P-diketonates is selected from:
O O
1 ,1 ,1 ,5,5,5-hexafluoropentane-
2, 4-dione (Hfac-H) acetylacetone
2 2
2,2,6,6-tetramethyl-3,5-heptanedione anc| combinations thereof.
According to a further particular aspect, the thin film is exposed to the etchant for a period of time between about 1 minute and about 15 minutes under a set temperature ranging between about 25°C to about 300°C, for example, 5 minutes at 120 °C.
According to a further particular aspect, the thin film is sequentially exposed to the etchant for a period of time between 1 minute and 15 minutes followed by purging the reactor with an inert gas comprising a combination of one or more of helium, neon, argon, krypton, or xenon, for a period of time between 1 minute and 15 minutes. According to a further particular aspect, is provided a method of developing a patterned thin film on a substrate according to the invention, wherein the patterned thin film comprises a thin amorphous ZIF (aZIF) film according to the invention, patterned by any of the methods described therein, followed by dry-etching using any of the methods as described herein to form a patterned deposit.
In an advantageous embodiment, the obtained product in the form of a ZIF coated amorphous porous substrate is used in imprinting or lithographic patterning processes (e.g., generating a patterned MOF coating on removable substrates). Patterned MOF can be used in microelectronics, electrochemical devices and in sensors.
According to a further particular aspect, is provided an amorphous ZIF (aZIF) film deposited on a substrate by any of the methods described herein, wherein the aZIF film’s thickness is from about 2 nm to 1,000 nm.
According to a further particular aspect, is provided a non-crystalline thin film according to the invention, wherein the metal ion is selected from Co+2/+3, Zn+2, and In+3 or combinations thereof.
According to another further particular aspect, is provided a non-crystalline thin film, wherein the ratio of the metal to the imidazolate compound as determined by X-ray photoelectron spectroscopy (XPS) is 1 : 1.5 to 1 :2.5.
According to another further particular aspect, is provided a non-crystalline thin film, wherein the imidazolate is a derivative of l,3-diazacyclopenta-2,4-diene having a chemical C3N2HR3, wherein the R groups are positioned at the 1, 4, and 5 positions of l,3-diazacyclopenta-2,4-diene and are each independently selected from -H, -CH3, -CH2CH3, -Cl, -Br, -I, -C4H4, and -CHO.
According to another further particular aspect, is provided a non-crystalline thin film, wherein the imidazolate is selected from: and combinations thereof.
According to another further particular aspect, is provided a non-crystalline metal-imidazolate thin film according to the invention, wherein the ligand comprises 2-methylimidazole (2mlm).
According to another further particular aspect, is provided a non-crystalline metal-imidazolate thin film according to the invention, wherein the metal-imidazolate film comprises a zinc-imidazolate film.
According to another further particular aspect, the thin non-crystalline film has a surface roughness of less than 5 nm.
According to another further particular aspect is provided a patterned deposit on a substrate made by any of the methods described therein.
According to another further particular aspect, the developed pattern has a line edge roughness of less than 2 nm.
According to another further particular aspect, the developed pattern has a feature resolution of about 10 nm.
According to another further particular aspect, the developed pattern has a feature thickness between about 2 and about 50 nanometers.
According to another further particular aspect, the developed pattern has a pitch of 30 nanometers or less.
According to another aspect, is provided an article comprising a non-crystalline thin film of the invention.
According to another further aspect, is provided an article comprising a non-crystalline thin film of the invention, wherein the article is selected from an extreme ultraviolet lithography (EUVL) resist, a membrane for gas separation, a gas sensor, and a microelectronic device.
According to another further aspect, is provided an article comprising a non-crystalline thin film of the invention, further comprising a material resulting from the irradiation of the thin film and which is not removed by a subsequent etching process.
According to another further aspect, is provided an article comprising a non-crystalline thin film of the invention, further comprising a material resulting from the irradiation of portions of the thin film and a subsequent etching or dissolution process that preferentially removes the irradiated or the non-irradiated portion of the thin film. According to another further aspect, is provided an article comprising a non-crystalline thin film of the invention, wherein the article is selected from a structural material, a dielectric barrier, and a photomask.
Also disclosed herein is a miniaturized catalytic, sensing, luminescent or biomedical (e.g. microfluidic or lab-on-a-chip device) device comprising an amorphous ZIF (aZIF) film according to the invention.
According to a particular aspect, the method reported here will likely accelerate the development of 2D crystalline and ultrathin amorphous MOF films for applications ranging from separation membranes to patterning.
Without willing being bound by any theory, it has been found that the film crystallinity is determined by the interaction of molecular precursors with the substrate ranging from epitaxy- determined order to amorphous films in the absence of any crystallographic registry.
As can be seen on Fig. 3b, only when the lattice mismatch between MOF and the substrate is small, the resulting MOF film is crystalline. For amorphous substrates, the obtained MOF structures are random.
According to another particular embodiment, is provided a gas selective filter comprising a 2D ZIF coated graphene membrane having a thickness of 2 to 10 nm wherein the size of the pores of the ZIF film is in the range of 0.25-1 nm, preferably 0.3-0.4 nm.
According to another particular aspect, a method and of the invention further advantageously provides useful starting materials for the preparation of membranes suitable for separation H2 from N2 where a H2 permeance reaching 20’000 gas permeation units with H2/N2 selectivity reaching 52, at 25°C.
The invention having been described, the following examples are presented by way of illustration, and not limitation.
EXAMPLES
Zinc nitrate hexahydrate (Zn(NO3)2’6H2O) was purchased from Sigma- Aldrich. 2-methylimidazole (2-mIm) was from Chemie Brunschwig AG. HC1 (32 wt%) was purchased from Reactolab S.A.. poly[l-(trimethylsilyl)-l-propyne] (PTMSP) was from ABCR. FeCh (97%) and Na2S20s was bought from Sigma-Aldrich. Cu foil (50 mm, 99.9%) were purchased from STREM. Toluene (AR) and methanol (AR) were from Fischer. All chemicals were used without further purifications. Si/SiO2 wafers were purchased from University Wafer Inc. Si/SiC>2 wafer with single layer graphene was bought from Ted Pella. Highly oriented pyrolytic graphite (HOPG) (ZYA quality, GRAS/1.0x7x7) was purchased from ScanSens. Silicon nitride TEM supports (50 nm silicon nitride film on a 200 pm silicon frame with nine viewing windows, each 0.1 x 0.1 mm) were purchased from Ted Pella.
Example 1: Method of preparation of ZIF films according to the invention on 2D substrates Various substrates 2D porous graphite substrates were used as substrates in a method according to the invention. a) Providing a 2D substrate
A 2D graphite substrate such as highly-oriented pyrolytic graphite (HOPG) or graphene/Si/SiCb is provided.
The 2D graphite substrate was prepared depending on the envisioned applications. Examples are provided below.
2D porous graphite substrate for the preparation of 2DZIF membrane for gas separation
A single-layer graphene (SLG) was synthesized by using low-pressure CVD of methane on copper foil following the literature for example as described in Huang et al., 2021, Sci. Adv. 7:eabf0116. Before the synthesis, the copper foil was annealed at 1077°C in a EE/ Ar atmosphere for 60 min. Then, CO2 (100 mL/min) and H2 (8 mL/min) flow was introduced successively, each for 30 min, to remove the contaminations. At last, CEE (24 mL/min) and H2 (8 mL/min) flow was used to grow single-layer graphene on copper film for 30 min at pressure of 460 mTorr.
After the synthesis of single-layer graphene, an O2 plasma cleaner, EQ-PCE-3, 13.56 Mhz, 17 W) was carried out to introduce nanopores. Briefly, the atmosphere in the plasma chamber was exchanged by O2 flow to pressure around 50 mTorr. Then, a plasma was generated for 4 s to etch SLG to get nanoporous graphene (NG). After the plasma treatment, a solution of Poly(l- trimethylsilyl-l-propyne) (PTMSP) in toluene (1.25 wt%) was spin-coated on NG at 1000 rpm for 30 s and 2000 rpm for 30 s, respectively. After that, the sample was placed in ambient air at room temperature overnight. Then, copper foil was etched by a combination of FeCh (0.5 M in water), HC1 (0.1 M in water) and water. Then, the obtained graphene/PTMSP film is used as a substrate in step b).
For the synthesis of 1 cm scale 2DZIF membrane, 1 wt% of Teflon in GALDEN perfluorinated fluid was spin-coated on NG at 300 rpm for 60 s, and heated at 60°C for 3 h. After that, the sample was put into a membrane module for the gas separation test, while Cu foil facing up. This allowed etching of Cu by a 10 wt% Na2S20s aqueous solution. Then, the obtained graphene/teflon film is used as a 2D substrate in step b). b) Immersing the 2D substrate in a precursor an ultradilute precursor solution
The 2D substrate was then immersed in an ultradilute precursor solution (< 2 mM Zn+2 and < 16 mM 2-methylimidazole (2-mIm), respectively) for a few minutes (Fig. la). First, in a petri dish containing 29 ml of Zn(NCb)2 aqueous solution at room temperature the 2D graphite substrate was partially immersed. Then, 1 ml of 2-mIm aqueous solution was added. After an incubation time of few minutes, the substrate was removed to stop the reaction.
The obtained ZIF films on graphitic substrates are referred to as 2DZIF. The use of such ultradilute solutions for the growth of ZIF films has not been reported before (Fig. lb) and as compared under Table 1 below: Table 1
2DZIF membranes for gas separation
When a graphene/PTMSP film was used as a 2D substrate, a 2-min reaction in Zn(NOs)2, 2 mM and 2-mIm, 16 mM aqueous solution was used, and the resulting 2DZIF/graphene/PTMSP film was transferred to a macroporous substrate (e.g. macroporous W support with l-mm2-size testing area) for further characterizations or applications. When a Teflon supported NG substrate was used as 2D substrate, a 10 min reaction time in (Zn(NOs)2, 2 mM and 2-mIm, 16 mM) solution was carried out.
When HOPG was used as a substrate, a growth solution of 1 mM Zn2+ and 8 mM 2-mIm and reaction time of about 5 min was used.
Example 2: Characterization of the ZIF films on 2D substrates
The ZIF films obtained by a method according to the invention were further characterized by various techniques as follows.
ZIF films prepared on HOPG prepared as described above were examined by optical and scanning electron microscopy (SEM). A sharp change in contrast was observed at the air/precursor-solution interface beyond which the film had a uniform contrast indicating that the film was smooth, continuous, and macroscopically uniform (Fig. If and 1g). Atomic force microscopy (AFM) imaging near the interface confirmed that the ZIF film is indeed continuous and has a thickness of ca. 2 nm (Fig. 1c and d). 4 and 6 nm thick films were obtained by increasing the growth time from 5 min to 10 and 15 min, respectively (Fig. le). A discrete, 2 nm, increase in film thickness suggests a crystalline order. A fitting of film thickness with the number of probable layers using the method described below yielded a monolayer thickness of 2 nm. Macroscopic films could be obtained on polycrystalline graphene synthesized by chemical vapor deposition on a Cu foil (Fig. If and 1g). Scanning electron microscope (SEM) measurements were performed on a Teneo Scanning Electron Microscope operating at 1 kV. Powder X-ray diffraction (PXRD) data were collected at a Bruker D8 Discover diffractometer with a Lynxeye XE detector, operated at 40 kV, 400 mA for Cu Ka ( = 1.5406 A) at ambient temperature and pressure. Bright-field transmission electron microscopy (TEM) images and selected-area electron diffraction (SAED) images were obtained with a Talos F200X microscope operated at 200 kV. TEM images for patterns on silicon nitride were obtained on a ThermoFisher TF30 TEM operating at 300 kV.
Low-dose aberration corrected high resolution TEM (AC-HRTEM) was performed on a Cs- corrected FEI G2 Titan 60-300 electron microscope at 300 kV, using a Gatan K2 direct-detection camera in electron counting mode. The AC-HRTEM images were acquired with the dose fractionation function, and each image stack is composed of 120 frames with 0.05 s exposure for each frame, with a total electron dose of ~60 e“A'2. The raw image was denoised by using an average background subtraction filter (ABSF). The CTF correction was performed based on the defocus value determined from the amorphous thon rings in the Fourier transform, and the projected electrostatic potential was simulated by the QSTEM software (QSTEM V2, 31). Simulated ED pattern was carried out by using Singlecrystal module of CrystalMaker software. AFM images and modulus measurement were recorded on a Bruker MultiMode 8 AFM. For modulus measurement, a Bruker Tap525 A rectangular probe was used and calibrated with standard sample sapphire, polystyrene and HOPG. XPS were carried out on an Axis Supra (Kratos Analytical) using the monochromated K x-ray line of an aluminium anode. Synchrotron GIXRD was carried out at beamline BM01, Swiss-Norwegian beamline (SNBL) at the European Synchrotron Radiation Facility (ESRF) with wavelength of 0.683 A.
Sample preparation of 2DZIF on graphene for atomic force microscopy (AFM)
For the AFM sample preparation of 2DZIF film on graphene/PTMSP substrate, the 2DZIF/graphene/PTMSP film was transferred on Si/SiC>2 wafer with 2DZIF layer facing the wafer. Then, the sample was annealed at 70°C for 4 h, to increase the adhesion between film and Si/SiC>2 wafer. After that, the sample was immersed in toluene for 12 h, to remove PTMSP layer.
The AFM image of 2DZIF film with triangular morphology after 5 min of water etching was collected directly on the film with 2DZIF layer facing up. Specifically, the 2DZIF/graphene/PTMSP film with triangular morphology was first scooped by glass slide with 2DZIF layer facing the slide, and a Si/SiC>2 wafer attached with double-sided carbon tape was pressed onto PTMSP layer. As a result, the 2DZIF/graphene/PTMSP film was transferred onto Si/SiC>2 wafer, resulting in 2DZIF layer facing up. AFM measurement of was carried out directly on the sample without any treatment.
Sample preparation for transmission electron microscopy (TEM)
Similar to sample preparation for AFM, 2DZIF/graphene/PTMSP film was transferred on TEM grid with 2DZIF layer facing the TEM grid. Then, the sample was annealed at 70°C for 4 h, to increase the adhesion between film and TEM grid. After that, the sample was immersed in toluene for 12 h, to remove the PTMSP layer.
Structural simulation
The simulation of 2DZIF structure was carried out by Density functional theory (DFT) calculations. At first, the reported ZIF-L structure (Chen et al. 2013, Chem. Commun., 49, 9500-9502) was imported into Forcite module in Material Studio software (Accelrys, San Diego, CA) to calculate the initial structural model, and unit-cell was set to be orthorhombic and a = 24.0 A, b = 20.0 A, c = 20.0 A, a = 90°, f = 90°, y = 90°, respectively, while the connectivity was kept. The calculation task was geometry optimization. The quality was set to be fine, and ‘smart’ algorithm was selected. After that, van der Waals DFT calculations were performed using the Quantum ESPRESSO package (Giannozzi et al., 2009, J. Phys. Condens. Matter, 21, 390052; Giannozzi et al., 2017, J. Phys. Condens. Matter, 29, 465901). The Brillouin zone was sampled at the gamma point. An energy cutoff of 60 Ry was used for the plane wave expansion of the wavefunctions. A kinetic energy cutoff of 480 Ry on the charge was used together with ultra-soft pseudopotentials (Lejaeghere et al., 2016, Science 351, 6280; Prandini, et al., 2018, Comput. Mater. 4, 72'). The relaxation was performed with the Perdew- Burke-Emzerhof (PBE) functional (Perdew et al., 1996, Phys. Rev. Lett. 77, 3865-3868). The system was relaxed to the lowest energy configuration of atoms. The surface geometry had been optimized with the convergence thresholds of 1 x 1 O'4 Ry and 3.28 * 1 O'3 Ry /Bohr for the total energy and forces, respectively.
Graphene supported ZIF film obtained by a method of the invention could be suspended on a holey transmission electron microscopy (TEM) grid (Fig. 2a) and it appeared that the film was devoid of large crystals and appeared uniform. Selected area electron diffraction (SAED) from a micrometersized area yielded three sets of diffraction patterns (Fig. 2b). The first two sets ((01), highlighted with grey circles) had six-fold symmetry originating from two slightly misoriented (by 3.0°) grains of graphene, while the last set had two-fold symmetry and belonged to a single grain of ZIF (highlighted with white circles), confirming that ZIF prepared on graphene was crystalline. The fact that a single 2DZIF grain could grow over two slightly misoriented graphene grains indicates that epitaxial growth can accommodate small lattice mismatch. Diffraction pattern from 2DZIF, typically representing a single grain, was observed from every single spot over a large area. Based on the diffraction pattern, a and b lattice parameters of 2.4 and 2.0 nm, respectively, could be fitted. Synchrotron grazing incidence X-ray diffraction (GIXRD) was carried out of a 10-nm -thick ZIF film on graphene resting on a Si/SiC>2 wafer prepared as described above. The in-plane GIXRD pattern revealed sharp diffraction peaks, consistent with the peak positions obtained by the radial integration of the SAED pattern (Fig. 2c) confirming that the film formed on the graphitic substrate exhibits crystalline order. The sharpness of the GIXRD peak (FWHM of 0.035°) indicates that the grains were at least 0.1-0.2 pm in size.
The presence of the order in the ZIF film when prepared over a graphitic substrate indicates a strong role of epitaxy in the formation of the ordered 2DZIF films.
X-ray photoelectron spectroscopy (XPS) of the 2DZIF and aZIF films was carried out to gain further insights into their coordination environments (Fig. 2d). The Nls XPS data of 2DZIF when compared to that of ZIF -L layers (comparative) and a prototypical nonlayered ZIF (ZIF-8) revealed that both 2DZIF and ZIF-L yield two peaks (399.0 and 400.2 eV corresponding to N-Zn and N-H bonds, respectively) in contrast to a single peak (399.0 eV) from the ZIF-8 crystals. This is consistent with the presence of abundant surface terminations (N-H) in the 2DZIF layers. In comparison, the population of N-H species was significantly diminished for aZIF indicating a nonlayered amorphous structure.
To gain insight into the structure of 2DZIF, structural relaxation based on density functional theory (DFT) was carried out starting with the a and b lattice parameters obtained by SAED and layer thickness from AFM. The relaxed structure has an orthorhombic space group Cmce with the following structural parameters; a = 24.196 A, b = 19.719 A, c = 20.908 A, a = 90°, ? = 90°, and Y = 90°. The layer in 2DZIF is composed of alternating 4-member ring (MR) and 6-MR chains while terminal 2-mIm linkers are present on both sides of the layer (Fig. 2e and 3c). The pore aperture of 2DZIF is constituted by the 6-MR and corresponds to a gap of 3.2 A. This value is in between that of ZIF-L (3.0 A) and ZIF-8 (3.4 A).
Aberration-corrected high-resolution TEM (AC-HRTEM) imaging of the 2DZIF film suspended on a TEM grid was carried out along the [001] crystallographic direction (Fig. 2f). The imaging was carried out using a low-dose beam condition (Zhu et al., 2017, Nat. Mater. 16, 532-536) to minimize damages to the beam sensitive 2DZIF lattice. Indeed, the obtained HRTEM image revealed the high crystallinity of the 2DZIF film. The corresponding Fourier transform validated the c-out-of-plane orientation of the film and was consistent with the simulated electron diffraction pattern from a film lying flat along the same orientation (Fig. 2g). Projection along the c-out-of- plane axis from the contrast transfer function (CTF) corrected image revealed alternating chains of 4-MR and 6-MR (Fig. 2h, left), consistent with the simulated [0001]-projected electrostatic potential map of 2DZIF structure obtained by density functional theory (DFT) structural relaxation (Fig. 2h, right)
The epitaxial relationship of 2DZIF with the graphitic lattice plays an important role in determining its unique 2D structure and morphology especially when contrasted against the closely related material, ZIF-L. Fig. 3a highlights the morphological differences in ZIF-L and 2DZIF. While the layers in ZIF-L and 2DZIF are stacked along the c-axis, the former grows as a leaf-shaped layered crystal whereas the latter can form macroscopically uniform monolayer films. The unique leaf shape is formed because ZIF-L layers stack with first progressively increasing and then progressively decreasing lateral size along the b-axis. In contrast, the planar morphology of 2DZIF is determined by its epitaxial relationship with the graphitic lattice with near perfect registry along the b-direction (lattice mismatch of 0.2%) and a mismatch along the a-direction (5.36%, Fig. 3b. This allows unimpeded grain growth of 2DZIF on the graphitic lattice. While both ZIF-L and 2DZIF have orthorhombic lattices, the unit-cell parameters of 2DZIF are distinct from those of ZIF-L where the latter has a significantly shorter parameter along the b (17.060 A) axis (Fig. 3c). The grains of 2DZIF could be visualized by partial etching of 2DZIF films based on the well documented dissolution of ZIFs in water with reaction condition of 0.5 mM Zn2+, 4 mM 2-mIm for 4 min (Fig. 3d). After partial dissolution, the grain shape was triangular with a lateral size of 1-2 pm (Fig. 3e) consistent with earlier observations of domains in the sub-monolayer film. The three sides of the triangular grains could be assigned to be (110), (110) and (100) lattice planes, respectively, reported to be the minimum surface energy planes for ZIF layers (Zhu et al., 2017, supra). AFM images (Fig. 3f) confirmed that the grains have uniform thickness of ~ ca. 2 nm consistent with the structure of 2DZIF.
The 3.2 A gap in the 6-MR of 2DZIF is attractive for sieving Fb (kinetic diameter of 2.89 A) from larger gas molecules such as CO2 (3.30 A), N2 (3.64 A), and CH4 (3.80 A) (Zhu et al., 2019, RSC Adv. 9, 2339-23399; Yang, et al., 2021, Sci. Bull. 66, 1869-1876).
The 2DZIF film (2DZIF grown on HOPG) was mechanically robust with Young’s modulus of 8.1 ± 2.1 GPa (Fig. 3h & i), comparable to that of the three-dimensional analogs (Tan et al., 2010, PNAS 107, 9938-9943).
Example 3: Gas performance of 2DZIF films according to the invention
Eb-sieving performance was assayed on 2DZIF films obtained as described in Example 1 using nanoporous graphene (NG) mechanically reinforced with a dense 250-nm-thick polyfl - (trimethylsilyl)propyne] (PTMSP) film where the NG/PTMSP film acts as a 2D substrate (Fig. 4a). The pores in NG were intentionally designed to be large (1.8 ± 1.2 nm) (He et al., 2019, Energy Environ. Sci., 12, 3305-3312) to rule out any molecular sieving from NG and to allow the determination of Fb-sieving from the 2DZIF film. The resulting 2DZIF/graphene/PTMSP film was transferred to substrate (macroporous W support with l-mm2-size testing area) for further characterizations or applications.
The gas separation performance of the membranes was recorded on a homemade permeation setup. The pressure on the feed side was maintained at 2-8 bar and on the permeate side at 1 bar during the measurements. All measurements were done after reaching the steady state with argon as the sweep gas. The membranes were sealed with stainless-steel gasket. The composition of permeate was analysed using an online Hiden Analytical HPR-20 mass spectrometer.
The permeances, J;, of gas i was calculated by Eq. SI
J, • = X;/(A-AP;) (SI) where X, is the molar flow rate of component i across the membrane area (A) and AP; is the transmembrane pressure difference for the component i. The selectivity a;/ of two gases (i and j, where i is the faster permeating gas) was calculated by Eq. S2 a,j = J,/ J, (S2)
The 2DZIF films, resting on the macroporous metal foil support (area of 1 mm2), exhibited a molecular cut-off for molecules larger than H2, indicating that gas transport was controlled by the 6-MR of 2DZIF (Fig. 4b). The H2 permeance was large (>15’000 gas permeation units or GPU; 1 GPU = 3.35 x 1O'10 mol m'2 s'1 Pa'1) similar to that from the support film (indicating a negligible transport resistance from the 2DZIF layer.
When an equimolar TUlS mixture was probed with feed pressure of 2 bar, a H2 permeance of 17300 GPU with a H2/N2 separation factor of 115 could be obtained (Fig. 4c). Another membrane when tested under a high-pressure feed (8 bar), exhibited a high H2 flux of 2.8 mol m'2 s'1 and H2/N2 separation factor of 52. This performance constitutes one of the best combinations of H2 flux and H2/N2 separation factor (Fig. 4d) as detailed in Fig. 4e, wherein the following references are cited: 12: Mao et al., 2014, ACS Appl. Mater. Interfaces 6, 4473-4479,' 13: Huang et al., 2018, Adv. Mater. Interfaces, 5, 1800287,' 14: Zhong et al., 2014, Carbon 72, 242-249,' 15: Zhong et al. 2015, J. Mater. Chem. A 3, 15715-15722,' 16: Li et al., 2016, Nat. Commun., 7, 11315,' 17: Eum et al., 2019, Angew. Chemie. Int. Ed. 131, 16542-16546,' 18: De Vos et al., 1998, Science 279, 1710- 1711,' 19: Poshusta et al, 1998, Ind. Eng. Chem. Res. 37, 3924-3929; 20: Guo et al., 2020, Angew. Chemie. Int. Ed., 59, 6284-634; 21: Liu et al., 2020, Nat. Commun., 11, 1633; 22: Lei et al., 2021, Nat. Commun., 12, 268; 23: Feng et al., 2020, Angew. Chemie. Int. Ed. 59, 3840-3845; Huang et al., 2021, Sci. Adv. 7, eabf0116).
Centimeter-scale 2DZIF membrane could be also prepared, thanks to the highly uniform deposition of 2DZIF films on graphene (Fig. If and g), which also presents attractive permselective H2 permeance (Fig. 4f & g; Table 2) and H2/N2 selectivity, in agreement with the smaller-area membranes.
Table 2
*Based on the resistance model as described below. Calculation of intrinsic performance of 2DZIF layer in 1 cm scale membrane:
The resistance (RJ) of gas permeance membrane is defined as,
Where L is the thickness of membrane, Pi is permeability of the membrane material to gas i, Ji is permeance of the membrane material to gas z, and A is the effective area of membrane.
The 2DZIF membrane is composed of two parts, supportive NG/Teflon layer and selective 2DZIF layer, that means the total resistance (Rtotai) can be expressed as a combination of resistance from supportive NG/Teflon layer, Rapport, and selective 2DZIF layer, R2D/1F,
Rtotai ~ Rsupptort + R2DZIF
According to the definition of resistance (/ ) of gas permeance membranes, we will have 1 _ 1 1 Jtotal Jsupport J2DZIF
Where Jtotai, Jsupport and J DZIF are permeance of total membrane, support layer and 2DZIF layer, respectively2.
Take H2 permeance data from Supplementary Table 4 for example, 1 1 2180 2450(GPI/) + J2DZIF
We will have the intrinsic H2 permeance of 2DZIF J2DZIF = 19781 (GPU).
Example 4: Method of preparation of MOE films according to the invention on 2D porous substrates
In order to support that the method of preparation can be applied to other MOFs and is not limited to ZIFs, a 2D film of UiO-66-NH2 was deposited on HOPG (Fig. 5) under the following conditions of 1 mM Zr4+, 1 mM BDC-NH2 aqueous solution for 2 min.
SEM image from panel b confirmed its flat and smooth of UiO-66-NH2 thin film and its thickness is 1.8 nm from the result of AFM measurement (Fig. 5c and 5d). Finally, its crystallinity was checked by electron diffraction, and two patterns were observed, where grey circles and white circles represent graphene and UiO-66-NH2, respectively (Fig. 5e and 5f).
Altogether, those data support that the method of the invention achieves the preparation of MOFs, in particular ZIFs, as macroscopically uniform crystalline 2D films from an ultradilute solution. The 2DZIF film yields exceptional FF-sieving performance, thanks to the ordered 2D structure with a high density of 6-MR with 3.2 A gap, making such a film the ultimate selective layer for membrane application. Example 5: Method of preparation of amorphous ZIF (aZIF) films using dip coating
It was surprisingly found that the film crystallinity is determined by the interaction of molecular precursors during curse of the method of preparation according to the invention and that useful ultrathin amorphous films could be obtained by using an amorphous substrate in a method according to the invention.
Ultrathin amorphous ZIF films with controlled thickness could be obtained by liquid phase coating of an amorphous substrate, such as a silicon wafer, in a method according to the invention using dip coating. a) Providing an amorphous substrate
Examples of substrates are Si/SiC>2 wafer and SiNx thin membranes.
A Si/SiC>2 wafer with a 300-nm-thick oxide layer was provided and used as received.
For electron patterning application, amorphous silicon nitride (SiN) (50-nm thick silicon nitride (SiNx)) was pre-treated with oxygen plasma for 10 min (29.6 W, 400 mTorr oxygen pressure) in a plasma cleaner (Harrick Plasma) to improve the surface reactivity and the pre-treated SiN layer was provided as an electron-beam transparent substrate. b) Immersing the supporting substrate in an ultradilute precursor solution
The amorphous substrate was then immersed in an ultradilute precursor solution (< 2 mM Zn+2 and < 16 mM 2-methylimidazole (2-mIm), respectively) for a few minutes (Fig. 6a). First, the substrate was partially immersed in a petri dish containing 29 ml of Zn(NOs)2 aqueous solution at room temperature the amorphous substrate was partially immersed. Then, 1 ml of 2-mIm aqueous solution was added. After an incubation time of 2-15 minutes, the substrate was removed to stop the reaction. The obtained ZIF films are referred to as aZIF. They were characterized by electron and atomic force microscopy. Figure 10 shows one such film with thickness of 14 nm. The ratio of Zn to 2-methylimidazole, as determined by survey scans of X-ray photoelectron spectroscopy (XPS), is about 2.
Example 6: Method of preparation of aZIF films using a flow coating device
A 1 cm wide silicon wafer is placed in a flow coating device (Figure 11 (A)). Precursor solutions containing 4 mM Zn+2 and 32 mM 2-mIm are injected into the device separately at flow rate of 2 mL/min, respectively, and mixed by a stir bar at 900 rpm. The mixed solution which contains 2 mM Zn+2 and 16 mM 2-mIm, then proceeds to contact and flow over the silicon wafer. The aZIF film is deposited at a rate of about 20 nm/min. After the reaction, the silicon wafer is removed from the device and blown dry with air. The thickness of the film is determined by ellipsometry and AFM (Fig. 11 (B)) Example 7: Method of preparation of aZIF films using a spin coating device
A 2 cm x 2 cm silicon wafer is placed in a spin coater. The spin speed is set at 500 rpm. Precursor solutions containing 4 mM Zn+2 and 32 mM 2-mIm are fed into the spin coater at a flow rate of 2 mL/min, respectively, and mixed immediately before dropped onto the silicon wafer. The mixed solution is continuously dropped onto the wafer for 2 or 4 min. After the coating, the films were characterized by electron and atomic force microscopy and their thickness was measured by ellipsometry (Figure 12).
Example 8: Electron beam patterning of aZIF films obtained by a method according to the invention
The aZIF film on the amorphous silicon nitride support obtained as described in Example 5 was subsequently exposed to a direct-write electron beam using 1 : 1 line- and space-patterns ranging from 10 to 40 nm in line width (or half pitch) using a Thermo Fisher Helios G4 UC Dual Beam microscope operating at 20 kV accelerating voltage and 400 pA beam current. The areal doses were 80 mC/cm2 for all patterns (Fig. 8a).
After exposure and development in water for 24 h and blown dried in a stream of nitrogen gas, it was observed that the irradiated area was preserved while the non-irradiated area was dissolved (Fig. 8b), confirming aZIF as a negative-tone resist. The thickness of the remaining aZIF structure was determined to be ~25 nm by AFM (Fig. 8c and d). The resolution of the resulting pattern, as exemplified by the well-resolved lines at 20 nm half pitch, is comparable to the state-of-the-art metal-containing resists (Oleksak et al., 2014, ACS Appl. Mater. Interfaces, 6, 2917-2921; Xu et al., 2018, Chem. Mater. 30, 4124-4133') which are an emerging class of material that hold promise in extreme ultraviolet lithography and electron beam lithography (Stowers et al., 2009, Microelectron. Eng. 86, 730-733; Luo et al., 2020, RSC Adv. 10, 8385-8395; Manouras et al.,
2020, Nanomaterials 10, 1593).
The simple fabrication of ultrathin ZIF films according to the present invention applied to amorphous substrates could accelerate the development of new ZIF-based resist materials for lithographic applications (Gangnaik et al., 2017, Review, Chem. Mater., 29, 1898-1917, Tu et al.,
2021, Nat. Mater. 20, 93-99, Ghash etal., 2021, Chem. Mater., 33, 5681-5689; Conrad et al., 2018, Angew. Chem. Int. Ed., 57, 13592-13597).
The ZIF films obtained on the Si/SiC>2 wafer substrate as described in Example 5 (Fig. 6a) were observed as being macroscopically smooth, continuous, and uniform ZIF films. AFM of one of these films, prepared using 2 mM Zn2+ and 16 mM 2-mIm and growth time of 10 s, confirmed that the film is smooth with thickness near 8 nm (Fig. 6b and 6c). Ellipsometry of several ZIF films on Si/SiC>2 wafer, prepared by varying the synthesis time, 10 s -5 min, indicated that the film thickness could be tuned in the range of 8-18 nm (Fig. 6d).
In X-ray diffraction (GIXRD), no diffraction from those ZIF films prepared directly on Si/SiC>2 wafer confirmed that that these films were amorphous.
Altogether, those data support that the method of the invention achieves the preparation of ZIFs, as macroscopically uniform amorphous films from an ultradilute solution on non-epitaxial substrates yields macroscopically smooth amorphous ZIF films, which can be used as negativetone resists yielding pattern features down to 10 nm.
Those ultrathin amorphous films are promising for advancing the limit of nanoscale patterning.
Example 9: Preparation of ZIF films according to the invention on 2D substrates using other ultradilute precursor solutions
Further metal-organic framework (MOF) coated substrates were prepared according to a method of the invention as exemplified in Example 1 wherein in this case, the amorphous substrate was then immersed in aqueous precursor solutions ranging comprising < 45 mM Zn+2 and < 20 mM benzimidazole (bim), respectively, Fig. 9A) for a few minutes (e.g., from 2 to 10 min). The greyed area corresponds to the composition of the precursor solution in which a 2D Zn2(bim)4 film can be successfully grown namely for a range of metal ion concentration from 3 mM to 9 mM and linker from 3 mM to 11 mM. (e.g. from about 0.1 wt% Zn2+ to about 0.3 wt% Zn2+ and from about 0.05 wt. % Bim to about 0.18 wt %) and the specific compositions which showed advantageous properties are marked with a star). For Example, a 2DZIF was synthesized on nanoporous graphene (NG)/PTMSP support film ultradilute precursor solution: Zn2+: 6.25 mM, bim': 6 mM leading to membrane M8.
Due to the ultrathin nature of film, handling of the film can lead to incorporation of defects. This can be overcome by deposition of multiple cycles (multiple layers of 2D film). For example, films prepared by 1 cycle and 5 cycle film deposition were compared. 5 cycle of deposition refers to 5- fold thicker 2D film.
The obtained 2D ZIF film after a single cycle of deposition according to the invention was characterized by electron diffraction (Fig. 9B). The electron diffraction was collected from a suspended film in transmission electron microscope from an area of 1 micrometer. The resulting pattern constitutes a pattern from a single crystalline grain, indicating that the Zn2(bim)4 film has at least 1 pm sized grain in the lateral (2D) direction. This also confirms the crystallinity of 2D Zn2(bim)4 film. The gas performance was characterized according to Example 3 except that in this case H2 and CO2 were probed (as against H2 and N2). This separation is also challenging and very useful for an important application called precombustion carbon capture for the production of clean H2 from fossil fuel. The obtained data are supporting that those 2D ZIF films are excellent for H2/CO2 separation (attractive for precombustion carbon capture in H2 production). In particular, a record high performance was obtained with membrane M8 achieving a combination of H2 permeance of 3220 GPU and H2/CO2 selectivity of 122 from centimeter-scale membranes after 5 cycles of treatment (Table 3).
Table 3
Overall, attractive combination of performance could be obtained by 1 to 5 cycle(s) of deposition (Fig. 9C) with advantage of high permeance in single cycle and high selectivity in 5 cycles.
Example 10: Development of electron beam patterned aZIF films in acidic solutions
The aZIF film on the silicon wafer obtained as described in Example 6 was exposed to electron beam using a matrix of 2-pm square patterns with varied dose as indicated in Figure 13, ranging from 2 to 40 mC/cm2. After exposure and development in 0.01 M aqueous solution of HC1 or acetic acid for 10 min, followed by blow drying in a stream of nitrogen gas, the irradiated area was preserved depending on the electron dose, while the non-irradiated area was dissolved (Figure 13), confirming aZIF as a negative-tone resist after development in acidic solutions.
Example 11: Development of electron beam patterned aZIF films in basic solutions
The aZIF film on the silicon wafer obtained as described in Example 6 was exposed to electron beam using a matrix of 2-pm square patterns with varied dose as indicated in Figure 14, ranging from 2 to 40 mC/cm2. After exposure and development in 0.01 M aqueous solution of TPAOH for 10 min and blown dried in a stream of nitrogen gas, it was observed that the irradiated area was preserved depending on the electron dose, while the non-irradiated area was dissolved (Figure 14), confirming aZIF as a negative-tone resist after development in basic solutions.
Example 12: Dry development of electron beam patterned aZIF films
Development of aZIF films that can be removed by a vapor-phase etchant (following the procedures disclosed in https://doi.org/10.26434/chemrxiv-2023-sl35t) would increase the throughput of the process and reduce contamination from solvents with the improved line resolution of amorphous thin films, while not being limited by pattern collapse, capillary forces, and other mechanical stress issues associated with solution-phase development.
The aZIF film on the silicon wafer obtained as described in Example 6 was exposed to electron beam using a matrix of 2-pm square patterns with varied dose. The exposed films were placed in a cylindrical quartz reactor system and transferred to an oven. A vial containing <1 mL of Hfac-H was placed outside the oven and connected to the reactor inlet with a manual valve separating the reactor from the etchant. The reactor outlet was connected to a cold trap and vacuum pump with a second manual valve separating the reactor from the vacuum. The system was heated to 120 °C under dynamic vacuum and evacuated for 30 minutes until the system pressure had stabilized (approximately 0.025 mbar). For the treatment, the Hfac-H valve was opened for the desired etching time and the sample was exposed to etchant vapors under static vacuum. Following treatment, the system was evacuated under dynamic vacuum for 30 minutes to remove volatile species. The vacuum was then shut off and the system was allowed to cool to room temperature. After etching experiments, AFM height mapping was performed to evaluate pattern dimensions (Figure 15).
Example 13: Positive-tone patterning of aZIF films
The aZIF film on the silicon wafer obtained as described in Example 5 was heated in a closed 60 mL PTFE reaction vessel with a bed of 0.1 g 4,5-dichloroimidazole (dclm) at 75°C for 90 min. The dclm treated film is then exposed to 5 keV electron beam at 0.5 mC/cm2 dose using a dot pattern. The diameter of the dots and the spacing between dots are both 100 nm. After exposure, the film is immersed in acetone for 10 s and blow dried in a stream of nitrogen gas. The area irradiated by the electron beam is removed after the development, i.e., the metal imidazolate serves as a positivetone resist (Figure 16).

Claims

Claims
1. A method for the preparation of a metal-organic framework (MOF) coated 2D substrate comprising the steps of: a) Providing a 2D substrate; b) providing an ultra-diluted MOF metal precursor solution, wherein said an ultra-diluted MOF metal precursor solution contains < 20 mM of metal ions and < 40 mM organic ligand, in particular < 10 mM of metal ions and < 20 mM organic ligand, more particularly < 2 mM of metal ions and < 16 mM organic ligand; c) immersing the said substrate in the ultra-diluted MOF metal precursor solution for about 2 to about 30 min; d) removing the obtained the MOF coated substrate from the precursor solution, wherein the MOF coated substrate comprises a MOF layer from 2 to 20 nm coated on said substrate.
2. The method of claim 1 wherein the support is a 2D porous graphitic substrate.
3. The method of claim 2 wherein the 2D porous substrate is selected from a HOPG substrate, a graphene/PTMSP substrate or a nanoporous graphene/teflon substrate.
4. The method of claim 1, wherein the MOF is a ZIF, in particular a Zn-based MOF.
5. The method of any preceding claim wherein the porous metal-organic framework is a Zr-MOF, in particular UiO-66.
6. The method of any one of claims 1 to 5, wherein the MOF is a ZIF and the ultra-diluted MOF metal precursor solution contains < 2 mM of Zn2+ and < 16 mM 2-methylimidazole (2mlm).
7. The method of any one of claims 1 to 5 and 6, wherein the ultra-diluted MOF metal precursor solution contains from 1 to 2 mM of Zn2+.
8. The method of any one of claims 1 to 5 and 7, wherein the ultra-diluted MOF metal precursor solution contains from 8 to 16 mM 2-methylimidazole.
9. The method of any one of claims 1 to 5, wherein the MOF is a ZIF and the ultra-diluted MOF metal precursor solution contains < 20 mM of Zn2+ and < 20 mM benzimidazole (Bim).
10. The method of any one of claims 1 to 5 and 9, wherein the ultra-diluted MOF precursor solution contains from 1 to 20 mM benzimidazole.
11. The method of any one of claims 1 to 5 and 10, wherein the ultra-diluted MOF precursor solution contains from 5 to 10 mM benzimidazole
12. The method of any preceding claims wherein the substrate is immersed in the ultra-diluted MOF metal precursor solution from 1 to 10 minutes (e.g., from 2 to 5 minutes).
13. The method of any preceding claims wherein the obtained MOF coated 2D substrate obtained from step d) is further submitted to one or more (e.g., 1 to 4 further cycles of steps b) to c)) to achieve repeated depositions through the immersion in the ultra-diluted precursor solution.
14. The method according to claim 13 wherein the MOF coated 2D substrate obtained after the last cycle comprises a MOF layer from about 2 to about 10 nm coated on said 2D substrate.
15. A graphitic substrate coated with two-dimensional crystalline ZIF (2DZIF) film obtainable from a method according to any one of claims 1 to 14.
16. A graphitic substrate coated with two-dimensional crystalline ZIF (2DZIF) film, wherein the said film’s thickness is from 2 to 20 nm (e.g., from 2 to 18 nm, such as from 2 to 10 nm) and the film’s pore density from 10% to 60%, in particular 30% to 60% (e.g. 50%).
17. A graphitic substrate coated with two-dimensional crystalline ZIF (2DZIF) film, according to claim 15 or 16 wherein the structure of 2DZIF has the following crystallographic lattice parameter a = 24.196 A, b = 19.719 A, c = 20.908 A.
18. A gas selective filter for separating Fh and N2 comprising a graphene membrane comprising a graphitic substrate coated with two-dimensional ZIF (2DZIF) film obtained from a method according to anyone of claims 1 to 14.
19. A gas selective filter comprising a membrane comprising a membrane comprising a porous graphitic substrate coated with two-dimensional ZIF (2DZIF) film according to claim 15 or 17.
20. Use of a gas selective filter according to any one of claims 18 to 19 for separating H2 and N2.
21. An amorphous substrate coated with an amorphous ZIF (aZIF) film, wherein the said film’s thickness is from 8 nm to-20 nm (e.g. 10 to 19 nm).
22. Use of an amorphous porous substrate coated with amorphous ZIF (aZIF) film according to claim 21 in an imprinting or lithographic patterning process. A method for the preparation of a zeolitic imidazolate framework (ZIF)-coated substrate comprising the steps of: a) Providing an amorphous substrate; b) providing a ZIF precursor solution, wherein said ZIF precursor solution contains < 20 mM of metal ions and < 200 mM organic ligand, in particular contains < 20 mM of metal ions and < 40 mM organic ligand and more particularly < 2 mM of metal ions and < 16 mM organic ligand; c) contacting the said substrate with the MOF metal precursor solution for about 2 to about 30 min or up to any desired time; d) removing the obtained MOF coated substrate from the precursor solution, wherein the MOF coated substrate comprises a MOF layer with thickness from about 2 to about 1’000 nm coated on said substrate. The method of claim 23, wherein ZIF precursor solution contains from 0.25 to 20 mM of metal ions and 4 to 200 mM imidazolate ligand as organic ligand, respectively. The method of claim 23 or 24, where the contacting step is performed using two streams of solutions, 1 and 2, that are mixed before contacting the substrate to form an ultra-diluted MOF metal precursor solution, where stream 1 containing the solution of the metal ions, and stream 2 containing the solution of the ligand. The method of claim 25, where the contacting is performed in a flow coating or spin coating device where the mixing of the two streams is accomplished immediately before the fluid contacts the substrate. The method of any one of claims 24 to 26, wherein the imidazolate is a derivative of 1,3- diazacyclopenta-2,4-diene having a chemical C3N2HR3, wherein the R groups are positioned at the 1, 4, and 5 positions of l,3-diazacyclopenta-2,4-diene and are each independently selected from -H, -CH3, -CH2CH3, -Cl, -Br, -I, -C4H4, and -CHO. The method of claim 27, wherein the imidazolate is selected from: and combinations thereof. The method of any one of claims 24 to 27, where the metal ion is one of Zn+2, Co+2/+3, In+3, or mixtures thereof. A method for patterning a thin film on a substrate, the method comprising:
(a) providing a zeolitic imidazolate framework (ZIF)-coated substrate obtained by a method of any one of claims 24 to 29;
(b) loading the said coated substrate into an ultra-high vacuum (UHV) chamber; and
(c) patterning the zeolitic imidazolate framework (ZIF) film of the coated substrate with direct write patterning, maskless patterning, or shadow mask patterning. The method of claim 30, wherein the patterning step further comprises irradiating the film with an electron source, an X-ray source, a deep ultraviolet, an extreme ultraviolet source, or other radiation source capable of producing secondary electrons. The method of claim 31, comprising patterning by an electron beam having an acceleration voltage with a range from about 2keV to about 100 keV. The method of claim 31 or 32, comprising patterning by an electron beam having a current with a range from about 6.3 pA to about 1.2 nA. The method of any one of claims 31 to 33, comprising patterning by an electron beam having a dosage with a range from about 0.01 mC cm'2 to about 50 mC cm'2 A method for etching a thin film on a substrate, wherein the thin film comprises a thin film obtained by a method according to any one of claims 24 to 30, the method comprising contacting the film with an etching solution. The method of claim 35, where the etching solution is water, methanol, ethanol, DMF, HC1, acetic acid, solutions of NaOH, KOH, TMAOH, TEAOH, TPAOH, or TBAOH in water or mixtures thereof. The method of claim 35 or 36, where the thin film is contacted with the etching solution for a period of time between about 1 minute and about 24 hours, at temperature from room temperature to about 60 °C. A method of developing a patterned thin film on a substrate, wherein the patterned thin film comprises a thin film obtained by a method according to any one of claims 24 to 30 patterned by any of the methods according to claims 30 to 34, followed by liquid-etching using a method of any one of claims claimed in 35 to 37 to form a patterned deposit. A method for dry etching a thin film on a substrate, wherein the thin film comprises a thin film obtained by a method according to any one of claims 24 to 30, the method comprising reacting the thin film with a volatile etchant to produce a volatile organometallic product and an organic product described by the formula A+ B => C + D where A represents the metal/ligand containing film, B represents a volatile molecular etchant, C represents a volatile coordination complex formed by the etchant and the metal , and D represents the volatile ligand originally contained in the film. The method of claim 39, wherein the etchant B comprises one or more P-diketonates. The method of claim 40, wherein the one or more P-diketonates is selected from:
O O
1 ,1 ,1 ,5,5,5-hexafluoropentane-
2, 4-dione (Hfac-H) acetylacetone and
2,2,6,6-tetramethyl-3,5-heptanedione and combinations thereof. The method of any one of claims 39 to 41, wherein the thin film is exposed to the etchant for a period of time between about 1 minute and about 15 minutes under a temperature ranging between e between about 25 °C to about 300 °C. The method of any one of claims 39 to 42, wherein the thin film is sequentially exposed to the etchant for a period of time between 1 minute and 15 minutes followed by purging with an inert gas comprising a combination of one or more of helium, neon, argon, krypton, or xenon, for a period of time between 1 minute and 15 minutes. A method of developing a patterned thin film on a substrate, wherein the patterned thin film comprises a thin film comprises a thin film obtained by a method according to any one of claims 24 to 30 patterned by any of the methods according to claims 30 to 34, followed by dry-etching using any of the methods according to claims 39 to 43 to form a patterned deposit. An amorphous ZIF (aZIF) film deposited on a substrate by any of the methods of claims 24 to 29, wherein the aZIF film’s thickness is from about 2 nm to 1,000 nm. The non-crystalline thin film of claim 45, wherein the metal ion is selected from Co+2/+3, Zn+2, and In+3 or combinations thereof. The non-crystalline thin film of claim 45 to 46, wherein the ratio of the metal to the imidazolate compound as determined by X-ray photoelectron spectroscopy (XPS) is 1 : 1.5 to 1 :2.5. The non-crystalline thin film of claim 47, wherein the imidazolate is a derivative of 1,3- diazacyclopenta-2,4-diene having a chemical C3N2HR3, wherein the R groups are positioned at the 1, 4, and 5 positions of l,3-diazacyclopenta-2,4-diene and are each independently selected from -H, -CH3, -CH2CH3, -Cl, -Br, -I, -C4H4, and -CHO. The non-crystalline thin film of claim 48, wherein the imidazolate is selected from: and combinations thereof.
50. The non-crystalline metal-imidazolate thin film of any one of claims 45 to 49, wherein the ligand comprises 2-methylimidazole (2mlm).
51. The non-crystalline metal-imidazolate thin film according to any one of claims 45 to 50, wherein the metal-imidazolate film comprises a zinc-imidazolate film.
52. The non-crystalline thin film according to any one of claims 45 to 51, wherein the thin film has a thickness from about 2 nm to about 1’000 nm.
53. The non-crystalline thin film of claim 52, wherein the thin film has a surface roughness of less than 5 nm.
54. A patterned deposit on a substrate made by any of the methods of claims 38 to 44.
55. The patterned deposit of claim 54, wherein the developed pattern has a line edge roughness of less than 2 nm.
56. The patterned deposit of claim 54, wherein the developed pattern has a feature resolution of about 10 nm.
57. The patterned deposit of claim 54, wherein the developed pattern has a feature thickness between about 2 and about 50 nanometers.
58. The patterned deposit of claim 4, wherein the developed pattern has a pitch of 30 nanometers or less.
59. An article comprising the non-crystalline thin film of any one of claims 45-58. The article of claim 59, wherein the article is selected from an extreme ultraviolet lithography (EUVL) resist, a membrane for gas separation, a gas sensor, and a microelectronic device. An article comprising the thin film of any one of claims 45-60, further comprising a material resulting from the irradiation of the thin film that is not removed by a subsequent etching process. An article comprising the thin film of any one of claims 45-60, further comprising a material resulting from the irradiation of portions of the thin film and a subsequent etching or dissolution process that preferentially removes the irradiated or the non-irradiated portion of the thin film. The article of claim 62, wherein the article is selected from a structural material, a dielectric barrier, and a photomask.
EP23804705.4A 2022-11-14 2023-11-13 Method of preparation of ultrathin metal-organic frameworks & uses thereof Pending EP4619150A2 (en)

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