KR102592128B1 - Metal-organic framework with 3d hierarchical porous structure and method for fabricating the same - Google Patents

Abstract

The disclosed metal-organic framework has three-dimensionally connected aligned micro-pores with a diameter of 100 nm to 1 μm and nanopores with a diameter of 1 nm to 10 nm and connected to the micro-pores. This metal-organic framework can reduce pressure drop by enabling smooth movement of fluid through micropores, and can have a large specific surface area due to nanopores.

Description

Metal-organic framework with 3D hierarchical porous structure and method for manufacturing the same {METAL-ORGANIC FRAMEWORK WITH 3D HIERARCHICAL POROUS STRUCTURE AND METHOD FOR FABRICATING THE SAME}

The present invention relates to porous structures. More specifically, it relates to a metal-organic framework with a three-dimensional hierarchical porous structure and a method for manufacturing the same.

Porous materials with nano-sized pores can have a very large surface area compared to the same mass/volume, so they can be used in application fields such as catalyst/ion exchange/energy fields that require high surface density (Patent Document 1, Non-Patent Document One). In particular, the specific surface area can be maximized in fine nanostructures of 10 nanometers or less, and for example, in the field of catalysts, it has been reported that the efficiency is highest in materials with nanostructures of several nanometers.

Accordingly, much research has been conducted to reduce the pore size to several nanometers in order to manufacture structures with a large surface area. In fact, for efficient gas separation and collection, it is desirable to form pores of 2 nm or less to increase the interaction between the target gas and the wall of the porous material. However, as the size of the pores decreases, the rate at which reactive substances diffuse into the structure rapidly decreases, which may lead to performance degradation. Additionally, when gas passes through a porous structure, a pressure drop occurs, and this phenomenon may limit the use of porous materials as gas-phase catalysts and applications.

As a structure to solve the above problems, a hierarchical nanostructure was proposed. Hierarchical nanostructures can increase specific surface area while lowering pressure drop through mixing various pore sizes. Methods for producing three-dimensional hierarchical nanostructures combining nanostructures of different scales have been proposed through various manufacturing methods. However, according to conventional methods, random structures are obtained or aligned structures are obtained. A hierarchical structure was created by chance in the three-dimensional nanostructure (Non-patent Document 2).

(1) Republic of Korea Patent No. 10-2112029

(1) Nano Energy, 54, 184-191 (2018) (2) PNAS, 117, 11, 5680-5685 (2020)

One object of the present invention is to provide a metal-organic framework having a three-dimensional hierarchical nanostructure in which aligned nanostructures with a diameter of 1 μm or less and fine nanostructures with a diameter of 10 nm or less are hierarchically combined.

Another object of the present invention is to provide a method for producing the metal-organic framework.

However, the problem to be solved by the present invention is not limited to the above-mentioned problem, and may be expanded in various ways without departing from the spirit and scope of the present invention.

The metal-organic framework according to exemplary embodiments of the present invention for achieving the above-described object of the present invention includes aligned micro pores having a diameter of 100 nm to 1 μm and connected in three dimensions, and the micro pores It is connected and has nanopores with a diameter of 1 nm to 10 nm.

A method for producing a metal-organic framework according to an embodiment of the present invention includes forming a porous template, providing an organic ligand precursor in the pores of the porous template, and adding an organic ligand precursor to the organic ligand precursor bound to the porous template. Providing metal ions to synthesize a metal-organic precursor and removing the porous template to form aligned micropores connected to nanopores in the metal-organic precursor and connected to each other in three dimensions.

According to one embodiment, the micro pores have a diameter of 100 nm to 1 ㎛ and the nano pores have a diameter of 1 nm to 10 nm.

According to one embodiment, the organic ligand precursor is benzene-1,4-dicarboxylic acid, benzene-1,3,5-tricarboxylic acid (benzene-1, 3,5-tricarboxylic acid, 2-methylimidazole, ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid ), o-phthalic acid, m-phthalic acid, p-phthalic acid, 2-hydroxy-1,2,3-propanetricarboxylic acid (2 -hydroxy-1,2,3-propanetricarboxylic acid), 1H-1,2,3-triazole (1H-1,2,3-triazole), 1H-1,2,4-triazole (1H-1, At least one selected from the group consisting of 2,4-triazole) and 3,4-dihydroxy-3-cyclobutene-1,2-dione Includes.

According to one embodiment, in order to provide metal ions to the organic ligand precursor, zinc (Zn), copper (Cu), nitel (Ni), cobalt (Co), iron (Fe), malganese (Mn), chromium ( A solution containing at least one ion selected from the group consisting of Cr), cadmium (Cd), magnesium (Mg), calcium (Ca), zirconium (Zr), gadolinium (Gd), europium (Eu) and terbium (Tb). The porous mold is immersed in.

According to one embodiment, the solution containing the metal ion includes water (deionized water), methanol, ethanol, propanol, butanol, dimethylformamide, Ethylene glycol, tetrahydrofuran, acetone, acetonitrile, benzene, carbon tetrachloride, chloroform, methylene chloride, cyclohexane (cyclohexane), dimethoxyethane, diethylformamide, dioxane, ether, ethyl acetate, glycerin, pentane, hexane ( selected from the group consisting of hexane, heptane, methyl, t-butyl ether, xylene, t-butyl alcohol, and toluene. Contains at least one

According to one embodiment, the porous mold is formed by near-field nanopatterning.

According to one embodiment, the porous template is removed by oxygen plasma at temperatures below 60°C.

According to one embodiment, the porous template includes a polymer.

According to one embodiment, providing an organic ligand precursor in the pores of the porous template so that the metal-organic framework fills the pores of the porous template, and the organic ligand precursor metal-organic framework bonded to the porous template. The step of providing metal ions to the manufacturing method is performed repeatedly.

As described above, according to exemplary embodiments of the present invention, a metal-organic framework having a hierarchical pore structure of three-dimensionally connected aligned micro-pores and nano-pores can be obtained. This metal-organic framework can reduce pressure drop by enabling smooth movement of fluid through micropores, and can have a large specific surface area due to nanopores.

When manufacturing a metal-organic framework using a porous template with a periodic structure as in the present invention, the volume of the framework increases relative to the amount of precursor during the synthesis process, and the volume increase is evenly induced to form a uniform structure. You can get it.

In addition, porous templates of various materials and shapes can be used to form metal-organic frameworks with shapes suitable for various application fields.

1 to 5 are cross-sectional views showing a method for manufacturing a metal-organic framework according to an embodiment of the present invention.
Figure 6 is a schematic diagram showing a porous template, an intermediate composite, and a metal-organic framework in a method for producing a metal-organic framework according to an embodiment of the present invention.
Figure 7 is a digital photograph of a wafer on which a porous template was placed according to the number of repetitions of synthesis of the metal-organic framework in Example 1.
Figure 8 is a SEM (scanning electron microscope) photograph showing the cross section and top view of the metal-organic framework before and after removal of the template (porous mold) in Example 1.

Hereinafter, a metal-organic framework and a method for manufacturing the same according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. Since the present invention can be subject to various changes and can take various forms, specific embodiments will be illustrated and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention. In the attached drawings, the dimensions of the structures are enlarged from the actual size for clarity of the present invention.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, or a combination thereof described in the specification, but are not intended to indicate the presence of one or more other features or numbers. It should be understood that this does not exclude in advance the possibility of the existence or addition of steps, operations, components, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined in the present application, should not be interpreted in an ideal or excessively formal sense. No.

1 to 5 are cross-sectional views showing a method for manufacturing a metal-organic framework according to an embodiment of the present invention. Figure 6 is a schematic diagram showing a porous template, an intermediate composite, and a metal-organic framework in a method for producing a metal-organic framework according to an embodiment of the present invention.

Referring to FIG. 1, an adhesive film 112 and a photoresist film 120 are formed on the base substrate 100.

According to one embodiment, the base substrate 100 may include a non-conductive material such as glass, silicon, quartz, etc. However, embodiments of the present invention are not limited to this, and the base substrate 100 may include a conductive material such as metal, or may have a laminate structure of a conductive material and a non-conductive material.

According to one embodiment, the adhesive film 112 may have an opening exposing the top surface of the base substrate 100. For example, the adhesive film 112 may be formed of a photoresist material. For example, a first photoresist material may be applied on the substrate through a spin coating process. The applied first photoresist material may be subjected to preliminary heat treatment, for example, at a temperature ranging from about 60°C to about 100°C. Next, the area corresponding to the opening can be masked, exposed using a light source such as ultraviolet rays, and developed to remove the unexposed area to form the opening. Next, the adhesive film 112 can be formed by hard baking using a hot plate at a temperature ranging from about 100°C to about 250°C.

The photoresist film 120 may contact the base substrate 100 by filling the opening.

For example, after applying a second photoresist material on the exposed upper surface of the adhesive film 112 and the base substrate 100 through a spin coating process, for example, in the range of about 60°C to about 100°C. The photoresist film 120 may be formed by soft baking at a temperature.

The same or different photoresist materials may be used as the first and second photoresist materials for forming the adhesive film 110 and the photoresist film 120. In some embodiments, an epoxy-based negative-tone photoresist or a DNQ-based positive-tone photoresist may be used as the first photoresist material and the second photoresist material. In one embodiment, an organic-inorganic hybrid material with photocrosslinking properties, a hydrogel, a phenolic resin, etc. may be used as the first photoresist material and the second photoresist material.

Referring to FIGS. 2, 3, and 6, the photoresist film 120 is exposed and developed to form a three-dimensional porous mold 130.

According to one embodiment, three-dimensional distributed light is provided to the photoresist film 120. The three-dimensional exposure may be performed through a proximity-field nanopatterning (PnP) process.

In the PnP method, for example, a periodic three-dimensional distribution generated from the interference phenomenon of light transmitted through a phase mask (MK) containing an elastomer material can be utilized to pattern a polymer material such as photoresist. there is. For example, when a flexible elastomer-based phase mask (MK) with a concavo-convex lattice structure formed on the surface is brought into contact with the photoresist layer, the phase mask is naturally formed on the photoresist layer based on Van der Waals force. It may be in close contact with the surface (e.g., conformal contact).

When a laser having a wavelength similar to the grating period of the phase mask is irradiated to the surface of the phase mask (MK), a three-dimensional distribution of light can be formed by the Talbot effect. When using a negative tone photoresist, crosslinking of the photoresist occurs selectively only in areas where light is strong due to constructive interference, and the exposure dose for crosslinking is not sufficient for the remaining areas where light is relatively weak, causing this phenomenon. It can be dissolved and removed during the development process. Finally, after going through the drying process, a porous polymer structure in which a periodic three-dimensional structure at the level of hundreds of nanometers (nm) to several micrometers (㎛) is connected to a network depending on the wavelength of the laser and the design of the phase mask is formed. can be formed.

According to exemplary embodiments, the pore size and periodicity of the porous polymer structure can be adjusted by adjusting the pattern period of the phase mask used in the PnP method and the wavelength of incident light.

More details on the PnP method can be found in the paper J. Phys, incorporated herein by reference. Chem. B 2007, 111, 12945-12958; Proc. Natl. Acad. Sci. U.S.A. 2004, 101, 12428; Adv. Mater. It is disclosed in 2004, 16, 1369 or Republic of Korea Patent Publication No. 2006-0109477 (published on October 20, 2006).

In some embodiments, the phase mask used in the PnP method is made of polydimethylsiloxane (PDMS), polyurethane acrylate (PUA), perfluoropolyether (PFPE), etc. May contain substances.

According to one embodiment, when the photoresist film 120 is formed of a negative tone photoresist, the non-exposed area may be removed by a developer and the exposed area may remain. Accordingly, a three-dimensional porous mold 130 containing three-dimensional nanopores can be obtained. For example, propylene glycol monomethyl ether acetate (PGMEA) may be used as the developer.

For example, the three-dimensional porous template 130 may include a channel in which nanoscale pores ranging from about 100 nm to about 2,000 nm are three-dimensionally connected or partially connected to each other. Accordingly, the three-dimensional porous mold 130 may include a three-dimensional network structure with periodic distribution by the channels.

According to one embodiment, the three-dimensional porous mold 130 may be obtained using a PnP method, but embodiments of the present invention are not limited thereto. For example, the three-dimensional porous mold 130 may be formed by methods such as particle self-assembly, interference lithography, direct laser writing, and two-photon lithography.

Referring to Figures 4 and 6, an organic ligand precursor is provided in the pores of the three-dimensional porous template 130. Next, metal ions are provided into the pores of the three-dimensional porous mold 130. As the organic ligand precursor and the metal ion react, a metal-organic framework 131 is formed within the pores of the three-dimensional porous template 130. The metal-organic framework 131 and the porous template 130 may form a composite 132.

In order to fill the metal-organic framework in the pores or form an appropriate size, the steps of providing the organic ligand precursor and the metal ion may be repeated.

The organic ligand precursor may be bound to the inner wall of the pore or may be bound to a previously formed metal-organic framework.

For example, the organic ligand precursor is benzene-1,4-dicarboxylic acid, benzene-1,3,5-tricarboxylic acid, 5-tricarboxylic acid, 2-methylimidazole, ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid, o-phthalic acid, m-phthalic acid, p-phthalic acid, 2-hydroxy-1,2,3-propanetricarboxylic acid (2-hydroxy -1,2,3-propanetricarboxylic acid), 1H-1,2,3-triazole (1H-1,2,3-triazole), 1H-1,2,4-triazole (1H-1,2, 4-triazole) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (3,4-dihydroxy-3-cyclobutene-1,2-dione) or a combination thereof.

For example, the metal ions include zinc (Zn), copper (Cu), nitel (Ni), cobalt (Co), iron (Fe), malganese (Mn), chromium (Cr), cadmium (Cd), and magnesium. (Mg), calcium (Ca), zirconium (Zr), gadolinium (Gd), europium (Eu), and terbium (Tb).

The metal-organic framework may have various microstructures depending on the combination of metal ions and organic ligands. Additionally, nanopores (for example, about 1 nm to 10 nm in diameter) are formed by the skeletal structure.

For example, a solution in which a metal salt or a hydrate thereof containing the metal is dissolved may be used to provide the metal ion. For example, when the metal ion is a zinc ion, Zn(NO ₃ ) _{2.6H 2} O, Zn(CH ₃ CO ₂ ) _{2.6H 2} O, Zn(CH ₃ COO) _{2.6H 2} O, ZnCl A solution containing _{2.6H 2} O ZnBr _{2.6H 2} O or a combination thereof may be used. For example, when the metal ion is a cobalt ion, Co(NO ₃ ) _{2.6H 2} O, Co(CH ₃ CO ₂ ) _{2.6H 2} O, Co(CH ₃ COO) _{2.6H 2} O, CoCl Solutions containing _{2.6H 2} O, CoBr _{2.6H 2} O or combinations thereof may be used.

For example, solvents for dissolving the metal ion solution or the organic ligand precursor include water (deionized water), methanol, ethanol, propanol, butanol, and dimethyl. Dimethylformamide, ethylene glycol, tetrahydrofuran, acetone, acetonitrile, benzene, carbon tetrachloride, chloroform, methylene chloride ( methylene chloride, cyclohexane, dimethoxyethane, diethylformamide, dioxane, ether, ethyl acetate, glycerin, pentane (pentane), hexane, heptane, methyl, t-butyl ether, xylene, t-butyl alcohol, toluene ) or a combination thereof may be used.

For example, the porous template 130 is immersed in a solution containing the organic ligand precursor, and then dried to remove the solvent. Next, the porous template 130 combined with the organic ligand precursor is immersed in a solution containing the metal ion to proceed with a reaction between the metal ion and the organic ligand precursor, thereby obtaining the metal-organic framework. .

Additionally, heat may be applied or pH may be adjusted to promote the reaction between the metal ion and the organic ligand precursor. For example, the heating temperature may be about 80°C to about 150°C. If the temperature is excessively low, it is difficult for the reaction to proceed sufficiently, and if the temperature is excessively high, the porosity of the obtained metal-organic framework may decrease or the arrangement of micropores may become uneven due to deformation of the porous template.

Referring to Figures 5 and 6, the three-dimensional porous template is removed to obtain a metal-organic framework 140 having micropores 130'.

According to example embodiments, the three-dimensional porous mold may be removed through heat treatment, wet etching, or plasma treatment.

The heat treatment may be performed at a temperature of about 400° C. to about 1,000° C., for example, in an air or oxygen atmosphere. An inert gas such as argon (Ar) may be added to the atmosphere for the heat treatment.

The plasma treatment may include oxygen plasma treatment or reactive ion etching (RIE) process. Preferably, in the process of removing the three-dimensional porous template, oxygen plasma is used at a low temperature, for example, at about 100°C or lower, preferably at about 60°C or lower, to prevent deformation of the metal-organic framework 140. may be provided.

In another embodiment, the porous template may include a material other than a polymer, such as a metal or metal oxide. Such a porous mold can be obtained by filling the polymer porous mold with another material and then removing the polymer porous mold. For example, the metal porous template can be removed using a removal solution containing an inorganic acid such as nitric acid, sulfuric acid, hydrofluoric acid, etc.

The metal-organic framework 140 may have an overall shape that is the inverse of the three-dimensional porous template, and may include micro pores 130' corresponding to the three-dimensional porous template and having a diameter of 100 nm to 1 ㎛ and the It may have nanopores formed by the metal-organic framework 140 and having a diameter of about 1 nm to 10 nm.

According to an embodiment of the present invention, a metal-organic framework having a hierarchical pore structure of three-dimensionally connected aligned micro-pores and nano-pores can be obtained. This metal-organic framework can reduce pressure drop by enabling smooth movement of fluid through micropores, and can have a large specific surface area due to nanopores.

When manufacturing a metal-organic framework using a porous template with a periodic structure as in the present invention, the volume of the framework increases relative to the amount of precursor during the synthesis process, and the volume increase is evenly induced to form a uniform structure. You can get it.

In addition, porous templates of various materials and shapes can be used to form metal-organic frameworks with shapes suitable for various application fields.

Hereinafter, the metal-organic framework and its manufacturing method according to exemplary embodiments will be described in more detail through specific experimental examples. The above experimental examples are provided merely as examples, and the scope of the present invention is not limited to the content provided in the above experimental examples.

Example 1

1. Fabrication of 3D porous mold

Photoresist (product name: SU-8 2, manufactured by Micro Chem) was applied on the silicon wafer by spin coating at 3,000 rpm for 30 seconds, and then heated on a hot plate at 65°C for 2 minutes and at 95°C for 3 minutes. Next, a chrome mask with the opening area covered is placed on the wafer coated with photoresist. After exposure to a UV lamp with a wavelength of 365 nm for 30 seconds, the photoresist is crosslinked at 120°C for 5 minutes. Next, it was immersed in a developer to form an adhesive film with a two-dimensional pattern with exposed opening areas.

A new photoresist (SU-8 10, manufactured by Micro Chem) was applied to the substrate on which the adhesive film was formed by spin coating at 1,700 rpm for 30 seconds, and then heated on a hot plate at 65°C for 30 minutes and at 95°C for 30 minutes. . A flexible elastomer-based phase mask (period of 600 nm) with a concave-convex grid structure in a square arrangement is contacted with the photoresist-coated substrate, and the photoresist is heated at 60°C for 6 minutes after irradiating a laser with a wavelength of 355 nm. did. Next, the developer solution was immersed and dried to obtain a three-dimensional porous mold.

2. Synthesis of metal-organic framework

A ligand solution was prepared by dissolving 2.596 g of 2-methylimidazol (Hmim) in 20 ml of methanol. The wafer was immersed in the ligand solution with the three-dimensional porous template facing upward, and then stirred at 170 rpm for more than 7 hours using a magnetic stirrer. Next, the three-dimensional porous mold was taken out and dried at 50°C for more than 2 hours. The porous mold and the wafer were immersed in a metal ion solution prepared by dissolving 0.586 g Zn(NO ₃ ) ₂ ㅇ6H2O (zinc nitrate hexahydrate) in 40 ml methanol for 3 hours without stirring in a direction perpendicular to the ground. In order to sufficiently fill the pores of the porous mold with the metal-organic framework, the above synthesis process was repeated three or more times, and after the final sample was completed, it was immersed in ethanol, stored, and dried.

3. Removal of 3D porous mold

The three-dimensional porous mold was removed at 40°C using an oxygen plasma equipment.

Figure 7 is a digital photograph of a wafer on which a porous template was placed according to the number of repetitions of synthesis of the metal-organic framework in Example 1. Referring to Figure 7, it can be seen that the degree of filling (color) of the porous mold varies depending on the number of synthesis.

Figure 8 is a SEM (scanning electron microscope) photograph showing the cross section and top view of the metal-organic framework before and after removal of the template (porous mold) in Example 1. Referring to FIG. 8, it can be seen that a metal-organic framework with a hierarchical pore structure was obtained according to an embodiment of the present invention.

Although the present invention has been described with reference to exemplary embodiments as described above, those skilled in the art will understand that the present invention can be varied without departing from the spirit and scope of the present invention as set forth in the following patent claims. You will understand that it can be modified and changed.

Metal-organic precursors according to exemplary embodiments of the present invention can be used in various industrial fields that use catalysts or ion exchange structures, such as air purification technology, sensors, batteries, etc.

Claims (10)

delete Forming a porous template containing a polymer and having a periodic three-dimensional structure using near-field nanopatterning;
providing an organic ligand precursor within the pores of the porous template;
synthesizing a metal-organic precursor by providing a metal ion to the organic ligand precursor combined with the porous template; and
By removing the porous template by oxygen plasma at 60°C or lower, nanopores with a diameter of 1 nm to 10 nm are connected within the metal-organic precursor, and aligned three-dimensionally connected to each other and having an overall diameter of 100 nm to 1 μm. A method for producing a metal-organic framework comprising forming micropores. delete The method of claim 2, wherein the organic ligand precursor is benzene-1,4-dicarboxylic acid, benzene-1,3,5-tricarboxylic acid, 3,5-tricarboxylic acid, 2-methylimidazole, ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid ), o-phthalic acid, m-phthalic acid, p-phthalic acid, 2-hydroxy-1,2,3-propanetricarboxylic acid (2 -hydroxy-1,2,3-propanetricarboxylic acid), 1H-1,2,3-triazole (1H-1,2,3-triazole), 1H-1,2,4-triazole (1H-1, At least one selected from the group consisting of 2,4-triazole) and 3,4-dihydroxy-3-cyclobutene-1,2-dione A method for producing a metal-organic framework comprising: The method of claim 2, wherein in order to provide metal ions to the organic ligand precursor, zinc (Zn), copper (Cu), nitel (Ni), cobalt (Co), iron (Fe), malganese (Mn), chromium ( A solution containing at least one ion selected from the group consisting of Cr), cadmium (Cd), magnesium (Mg), calcium (Ca), zirconium (Zr), gadolinium (Gd), europium (Eu) and terbium (Tb). A method for producing a metal-organic framework, characterized in that immersing the porous mold in. The method of claim 5, wherein the solution containing the metal ion includes water (deionized water), methanol, ethanol, propanol, butanol, dimethylformamide, Ethylene glycol, tetrahydrofuran, acetone, acetonitrile, benzene, carbon tetrachloride, chloroform, methylene chloride, cyclohexane (cyclohexane), dimethoxyethane, diethylformamide, dioxane, ether, ethyl acetate, glycerin, pentane, hexane ( containing at least one selected from the group consisting of hexane, heptane, t-butyl ether, xylene, t-butyl alcohol, and toluene A method for producing a metal-organic framework, characterized in that. delete delete delete The method of claim 2, comprising providing an organic ligand precursor within the pores of the porous template so that the metal-organic framework fills the pores of the porous template, and providing a metal ion to the organic ligand precursor bound to the porous template. A method for producing a metal-organic framework, characterized in that the step is performed repeatedly.