CN112920416A

CN112920416A - Preparation method of transition metal-based SURMAOFs based on liquid phase epitaxy method

Info

Publication number: CN112920416A
Application number: CN202110090863.2A
Authority: CN
Inventors: 刘进轩; 梁竞
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2021-01-22
Filing date: 2021-01-22
Publication date: 2021-06-08

Abstract

The invention provides a preparation method for synthesizing a transition metal-based SURMAFS film by adopting a liquid phase epitaxy method. The method comprises the steps of firstly modifying the surface of a load, then sequentially immersing the load into a transition metal salt solution, an ethanol solution, an organic ligand solution and an ethanol solution, and separating the steps for 3min to ensure the volatilization of solvent molecules. The SURMOFs film prepared by the method has high orientation in structure, is nano-flaky in appearance, and still keeps stable after being calcined in an inert atmosphere at 300 ℃. Compared with the traditional hydrothermal method, the method can prepare the SURMOFs film on various substrates by adopting a liquid phase epitaxy method, can regulate the thickness of the SURMOFs film in the growth process, accurately controls the appearance and the growth orientation of the SURMOFs, and is very beneficial to researching the growth mechanism of the MOF.

Description

Preparation method of transition metal-based SURMAOFs based on liquid phase epitaxy method

Technical Field

The invention relates to the technical field of new material synthesis, in particular to a preparation method of transition metal-based SURMAOFs based on a liquid phase epitaxy method.

Background

SURMAOFs (Surface-supported metal-organic frameworks) refer to Surface-supported metal-organic framework materials, which are receiving increasing attention as a new class of nanomaterials. SURMOFs have advantages not found in conventional MOFs: (1) the thickness, the surface roughness, the growth orientation and the size of the material can be accurately controlled; (2) the method is favorable for researching the growth mechanism of the metal organic framework compound; (3) its structure can be regulated during growth to regulate its properties; (4) the SURMOFs film in the form of a film can be used in a variety of fields such as sensing, photovoltaics, energy storage, water splitting, and electronic devices.

Currently, the methods used to prepare SURMOFs films are: chemical vapor deposition, atomic layer deposition, electrochemical preparation and the like. The chemical vapor deposition method requires the preparation of reactants into volatile substances through thermal decomposition reaction, and has high limitations and poor crystallinity of the prepared SURMOFs film. The atomic deposition method can prepare a film with the thickness of one atomic layer, but the method has high requirement on the surface roughness of the substrate, and the method needs a long time for synthesizing SURMOFs film with a certain thickness. The electrochemical method is very fast for synthesizing SURMOFs thin films, but the synthesis conditions are complex, and the prepared thin films are poor in uniformity and difficult to accurately control the thickness.

Disclosure of Invention

In view of the above-mentioned problems, the present invention provides a method for preparing SURMOFs film having high orientation and being stable at 300 ℃ by liquid phase epitaxy. The synthetic raw materials are cheap and easy to obtain, the synthetic method is simple and convenient, the whole preparation process is environment-friendly, and the thickness of the material can be accurately controlled.

The technical means adopted by the invention are as follows:

a preparation method of synthetic transition metal-based SURMOFs comprises the following steps:

(1) modifying the surface of the substrate;

(2) immersing the modified substrate into a transition metal salt solution for 5-10 min, and drying;

(3) immersing the substrate in absolute ethyl alcohol for 3-5 min, and drying;

(4) immersing the substrate into an organic ligand solution for 5-10 min, and drying;

(5) immersing the substrate in absolute ethyl alcohol for 3-5 min, and drying.

Further, in the steps (2) to (5), the drying treatment is to place the substrate in a drying atmosphere for 3-10 min; the drying atmosphere is air at 40-60 ℃.

Further, the substrate is one of gold sheet, carbon paper, glassy carbon or conductive glass.

Further, when the substrate is carbon paper, the surface modification is specifically that the substrate is subjected to ultrasonic treatment for 20-30 min by using deionized water and ethanol respectively, and then the substrate is placed into an oxygen plasma cleaning machine and treated for 3-5 min at 40kHz RF frequency, so that a layer of hydroxyl is attached to the surface of the substrate; when the substrate is a gold sheet, glassy carbon or conductive glass, the surface modification is specifically that the substrate is immersed in a 16-mercaptohexadecanoic acid solution for 24-36 h to enable the surface of the substrate to have a monolayer with carboxyl as a terminal, and then the substrate is respectively washed by a weak base solution and a weak acid solution and dried for later use.

Further, the weak acid solution is a mixed solution of ethanol and acetic acid, and the volume ratio of the ethanol to the acetic acid is 1: 8-1: 10; the weak base solution is a mixed solution of ethanol and triethylamine, and the volume ratio of the ethanol to the triethylamine is 1: 45-1: 50; the solvent of the 16-mercaptohexadecanoic acid solution is a mixed solution of ethanol and acetic acid, and the mass-volume ratio (mg: ml: ml) of the 16-mercaptohexadecanoic acid to the ethanol to the acetic acid is 1:130: 15-1: 150: 20.

Further, the organic ligand solution is terephthalic acid solution, 2-hydroxy terephthalic acid solution, 2-amino terephthalic acid solution or 2-nitro terephthalic acid solution, the concentration is 0.8-1.6 mM, and the solvent is absolute ethyl alcohol.

Further, the solvent of the transition metal salt solution is absolute ethyl alcohol, and the transition metal salt is one or more of nitrate, chloride or sulfate corresponding to iron, cobalt or nickel; the concentration of the transition metal salt solution is 0.8-2 mM.

Further, the steps (2) to (5) are circulated once, and the circulation frequency is 20-150 times.

Further, when the transition metal salt solution is one of nitrate, chloride or sulfate corresponding to Cu, the solvent is absolute ethyl alcohol with the concentration of 1.0-1.5 mM, the organic ligand solution is 1.2-2.0 mM trimesic acid (BTC) solution, and the solvent is absolute ethyl alcohol.

The invention adopts a pulling coating machine to sequentially and circularly soak a pretreated substrate in a metal ion solution, an ethanol solution, an organic ligand solution and an ethanol solution so as to synthesize the transition metal-based SURMOFs film.

Compared with the prior art, the invention has the following advantages:

1. the transition metal-based SURMOFs film prepared by the method has controllable thickness and is stable at 300 ℃.

2. The liquid phase epitaxy method is characterized in that metal and organic ligand precursors are alternately deposited on the surface of a functionalized substrate, and the method comprises two key steps of substrate modification and deposition process. Compared with a chemical vapor deposition method and an atomic deposition method which need expensive equipment for supporting, the liquid phase epitaxy method has the advantages of low cost, simplicity and convenience in operation, controllable preparation process and the like, and has great advantages in both research and application. Compared with the electrochemical preparation method, the SURMAFs film prepared by the liquid phase epitaxy method has better uniformity and crystallinity.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1, (a) is a NiCo-BDC SURMAFS X-ray diffraction pattern synthesized on a conductive glass (FTO); (b) NiCo-BDC SURMAFS X-ray diffraction patterns with different cycle times are synthesized on the gold sheet substrate.

FIG. 2 is a graph showing the distribution of the element content of NiCo-BDC SURMOFs with a gold plate as a substrate and 100 layers.

FIG. 3 is the X-ray diffraction pattern of 100 layers of NiCo-BDC SURMOFs with gold plate as the substrate after pyrolysis at 300 ℃.

FIG. 4 shows scanning electron micrographs of 100 layers of NiCo-BDC SURMOFs after pyrolysis treatment at 300 ℃ for 2 h.

FIG. 5 is an X-ray diffraction pattern of 100-layer Co-BDC SURMOFs with different concentrations on carbon paper.

FIG. 6 is a scanning electron micrograph of 100 layers of Co-BDC SURMOFs with different concentrations on carbon paper as the substrate.

FIG. 7 is a scanning electron micrograph of 100 layers of CoNi-BDC-OH SURMOFs with carbon paper as the substrate.

In FIG. 8, (a) to (d) are scanning electron micrographs of NiCo-BDCSRMOFs of 20 cycles, 50 cycles, 100 cycles and 120 cycles on the gold plate, respectively.

FIG. 9 is a SEM image of Cu-BTCSURMOFs with a gold plate as the substrate 30 layer.

Detailed Description

The present invention will be further illustrated with reference to the following specific examples, but the present invention is not limited to the following examples. The method is a conventional method unless otherwise specified. The starting materials are commercially available from the open literature unless otherwise specified.

Example 1

First, a solution for treating a substrate is prepared: 1mg of 16-mercaptohexadecanoic acid solution was dissolved in a mixed solution of 130ml of ethanol solution and 15ml of acetic acid. A conductive glass with a size of 1cm by 2cm was then soaked with this solution for 24 h. Washing with triethylamine solution (ethanol as solvent; volume ratio of 1:49) for three times, wherein the volume of each time is 2 ml; and then washed with acetic acid solution (ethanol as solvent; volume ratio of 1:9) for three times, and the volume of each time is 2 ml.

Sequentially immersing the treated conductive glass into 1.2mM Ni-Co double metal salt mixed solution for 10 min; soaking in ethanol solution for 3 min; immersing into 0.8mM terephthalic acid solution of organic ligand for 10 min; soaking in ethanol solution for 3 min; the above steps are separated by 3min to ensure the solvent molecules to volatilize. And sequentially dipping the metal salt solution, the ethanol solution, the organic ligand solution and the ethanol solution for one cycle, and repeating the above steps for 20-150 times to obtain the NiCo-BDC SURMAFs film.

FIG. 1(a) shows that NiCo-BDC SURMOFs crystals have a (200) plane X-ray diffraction peak at 8.68 deg., indicating that the SURMOFs films were successfully assembled on a conductive glass substrate and grown in only one orientation (200), indicating that the films have high crystallinity.

Example 2

First, a solution for treating a substrate is prepared: 1mg of 16-mercaptohexadecanoic acid solution was dissolved in a mixed solution of 130ml of ethanol solution and 15ml of acetic acid. Gold flakes of size 1cm by 2cm were subsequently soaked with this solution for 24 h. Washing with triethylamine solution (ethanol as solvent; volume ratio of 1:49) for three times, wherein the volume of each time is 2 ml; and then washed with acetic acid solution (ethanol as solvent; volume ratio of 1:9) for three times, and the volume of each time is 2 ml.

Sequentially immersing the processed gold sheets into 1.2mM Ni-Co double metal salt mixed solution for 10 min; soaking in ethanol solution for 3 min; immersing into 0.8mM terephthalic acid solution of organic ligand for 10 min; soaking in ethanol solution for 3 min; the above steps are separated by 3min to ensure the solvent molecules to volatilize. And sequentially dipping the metal salt solution, the ethanol solution, the organic ligand solution and the ethanol solution for one cycle, and repeating the above steps for 20-150 times to obtain the NiCo-BDC SURMAFs film.

FIG. 1(b) is an XRD pattern of NiCo-BDC SURMAFS obtained by repeating the above steps for various times, and shows that the method can be used for preparing NiCo-BDC SURMAFS crystals grown along the (200) orientation on gold sheets, and the cycle number has no obvious influence on the crystallinity of the film.

The NiCo-BDC SURMOFs film which is cycled for 100 times is taken for element content distribution analysis, the result is shown in figure 2, Si, Cl, Ti and Au elements come from a gold substrate, C, O, Ni and Co come from the SURMOFs film which grows on the substrate, and the successful detection of the Ni and Co elements indicates that the SURMOFs film is bimetal.

Example 3

First, a solution for treating a substrate is prepared: 1mg of 16-mercaptohexadecanoic acid solution was dissolved in a mixed solution of 150ml of ethanol solution and 20ml of acetic acid. Gold flakes of size 1cm by 2cm were subsequently soaked with this solution for 24 h. Washing with triethylamine solution (ethanol as solvent; volume ratio of 1:49) for three times, wherein the volume of each time is 2 ml; and then washed with acetic acid solution (ethanol as solvent; volume ratio of 1:9) for three times, and the volume of each time is 2 ml. Sequentially immersing the processed gold sheets into 1.6mM Ni-Co double metal salt mixed solution for 10 min; soaking in ethanol solution for 3 min; 1.2mM is immersed in an organic ligand terephthalic acid solution for 10 min; soaking in ethanol solution for 3 min; the above steps are separated by 3min to ensure the solvent molecules to volatilize. Repeating the steps for 20-150 times to obtain the NiCo-BDC SURMAFs film.

And (3) heating the NiCo-BDC SURMOFs film which circulates for 100 times to 300 ℃ at the speed of 5 ℃/min in the argon atmosphere, keeping for 2-4 h, and then cooling to room temperature. The pyrolysis results are shown in FIG. 3 and FIG. 4, and the characteristic peak of NiCo-BDC SURMAOFSs at 8.68 ℃ is not changed, which shows that the crystallinity of the film is well maintained. From SEM images, it is clear that the bimetallic SURMAOFSs maintain a two-dimensional sheet-like morphology and have uniform sizes after pyrolysis for 2 hours.

Example 4

Firstly, carbon paper with the size of 1cm multiplied by 2cm is respectively treated with deionized water and ethanol for 20min to remove dirt and impurities on the surface, and then the carbon paper is treated in an oxygen plasma cleaning machine for 3min to enable the surface of the carbon paper to be attached with a layer of hydroxyl. Respectively immersing the treated carbon paper in 0.8mM, 1.2mM, 1.6mM and 2mM Co single metal salt solution for 10 min; soaking in ethanol solution for 3 min; then soaking the substrate in 0.8mM, 1mM, 1.2mM and 1.4mM organic ligand terephthalic acid solution respectively for 10 min; soaking in ethanol solution for 3 min; the above steps are separated by 3min to ensure the solvent molecules to volatilize. Repeating the steps for 20-150 times to obtain Co-BDC SURMOFs films with different solution concentrations, wherein XRD results of 50 times of circulation are shown in figure 5, and electron microscope results are shown in figure 6.

FIG. 5 shows that the SURMOFs film prepared under the conditions that the concentration of the Co ion solution is 1.6mM and the concentration of the terephthalic acid solution is 1.2mM has obvious orientation and good crystallinity; FIGS. 6 (a) and (b) show that Co-BDC SURMOFs nanosheets were formed on the surface of the carbon paper substrate at concentrations of 0.8mM and 1.2mM Co ion solution and 0.8mM and 1mM terephthalic acid solution; (c) the figure shows that when the concentration of the Co ion solution is 1.6mM and the concentration of the terephthalic acid solution is 1.2mM, dense Co-BDC SURMOFs nano-sheets are formed on the carbon paper substrate. (d) The figure shows that the Co-BDC SURMOFs film is more dense when the concentration of the Co ion solution is 2mM and the concentration of the terephthalic acid solution is 1.4 mM.

Example 5

First, a solution for treating a substrate is prepared: 1mg of 16-mercaptohexadecanoic acid solution was dissolved in a mixed solution of 150ml of ethanol solution and 20ml of acetic acid. Gold flakes of size 1cm by 2cm were subsequently soaked with this solution for 24 h. Washing with triethylamine solution (ethanol as solvent; volume ratio of 1:49) for three times, wherein the volume of each time is 2 ml; and then washed with acetic acid solution (ethanol as solvent; volume ratio of 1:9) for three times, and the volume of each time is 2 ml.

Sequentially immersing the processed gold sheets into 1.6mM Ni-Co double metal salt mixed solution for 10 min; soaking in ethanol solution for 3 min; immersing in 1.2mM organic ligand 2-hydroxy phthalic acid solution for 10 min; soaking in ethanol solution for 3 min; the above steps are separated by 3min to ensure the solvent molecules to volatilize. And sequentially dipping the metal salt solution, the ethanol solution, the organic ligand solution and the ethanol solution for one cycle, and repeating the above steps for 20-150 times to obtain the NiCo-BDC-OH SURMOFs film. As is apparent from FIG. 7, the two-dimensional nanosheets are thinner and the porosity of the formed thin film material is increased with the use of the 2-hydroxyphthalic acid ligand.

Example 6

Sequentially immersing the processed gold sheets into 1.2mM Ni-Co double metal salt mixed solution for 10 min; soaking in ethanol solution for 3 min; soaking in 0.8mM organic ligand terephthalic acid solution for 10 min; soaking in ethanol solution for 3 min; the above steps are separated by 3min to ensure the solvent molecules to volatilize. Sequentially dipping the metal salt solution, the ethanol solution, the organic ligand solution and the ethanol solution for one cycle, and repeating the above steps for 20 times, 50 times, 100 times and 120 times respectively. From FIG. 8, it is understood that the number of cycles increases, the two-dimensional nanosheets become larger, the coverage on the substrate increases, and the uniformity of the film is significantly improved.

Example 7

First, a solution for treating a substrate is prepared: 1mg of 16-mercaptohexadecanoic acid solution was dissolved in a mixed solution of 150ml of ethanol solution and 20ml of acetic acid. A conductive glass with a size of 1cm by 2cm was then soaked with this solution for 24 h. Washing with triethylamine solution (ethanol as solvent; volume ratio of 1:49) for three times, wherein the volume of each time is 2 ml; and then washed with acetic acid solution (ethanol as solvent; volume ratio of 1:9) for three times, and the volume of each time is 2 ml.

Sequentially immersing the processed gold sheets into a 1.2mM Cu metal salt mixed solution for 5 min; soaking in ethanol solution for 3 min; soaking in 1.6mM organic ligand trimesic acid (BTC) solution for 5 min; soaking in ethanol solution for 3 min; the above steps are separated by 3min to ensure the solvent molecules to volatilize. Repeating the steps for 20-100 times to obtain the Cu-BTC SURMAFs film. As a result of electron microscopy, as shown in FIG. 9, the film was composed of pyramids, the crystal grains were more dispersed, and the porosity of the film was increased.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method for synthesizing transition metal-based SURMOFs is characterized by comprising the following steps:

(1) modifying the surface of the substrate;

(3) immersing the substrate in absolute ethyl alcohol for 3-5 min, and drying;

(5) immersing the substrate in absolute ethyl alcohol for 3-5 min, and drying.

2. The preparation method according to claim 1, wherein in the steps (2) to (5), the drying treatment is to place the substrate in a drying atmosphere for 3-10 min; the drying atmosphere is air at 40-60 ℃.

3. The method of claim 1, wherein the substrate is one of gold, carbon paper, glassy carbon, or conductive glass.

4. The preparation method according to claim 3, wherein when the substrate is carbon paper, the surface modification is specifically that the substrate is subjected to ultrasonic treatment for 20-30 min by using deionized water and ethanol respectively, and then the substrate is placed into an oxygen plasma cleaning machine and treated for 3-5 min at 40kHz RF frequency; when the substrate is a gold sheet, glassy carbon or conductive glass, the surface modification is specifically that the substrate is immersed in a 16-mercaptohexadecanoic acid solution for 24-36 h, then washed by a weak base solution and a weak acid solution respectively, and dried for later use.

5. The preparation method according to claim 4, wherein the weak acid solution is a mixed solution of ethanol and acetic acid, and the volume ratio of the ethanol to the acetic acid is 1: 8-1: 10; the weak base solution is a mixed solution of ethanol and triethylamine, and the volume ratio of the ethanol to the triethylamine is 1: 45-1: 50; the solvent of the 16-mercaptohexadecanoic acid solution is a mixed solution of ethanol and acetic acid, and the mass-volume ratio (mg: ml: ml) of the 16-mercaptohexadecanoic acid to the ethanol to the acetic acid is 1:130: 15-1: 150: 20.

6. The method according to claim 1, wherein the organic ligand solution is terephthalic acid solution, 2-hydroxy terephthalic acid solution, 2-amino terephthalic acid solution or 2-nitro terephthalic acid solution, the concentration is 0.8-1.6 mM, and the solvent is absolute ethanol.

7. The preparation method according to claim 1, wherein the solvent of the transition metal salt solution is absolute ethyl alcohol, and the transition metal salt is one or more of nitrate, chloride or sulfate corresponding to iron, cobalt or nickel; the concentration of the transition metal salt solution is 0.8-2 mM.

8. The method according to claim 1, wherein the steps (2) to (5) are performed in one cycle, and the number of cycles is 20 to 150.

9. The method according to claim 1, wherein the transition metal salt solution is one of nitrate, chloride and sulfate corresponding to Cu, the solvent is absolute ethanol and has a concentration of 1.0-1.5 mM, the organic ligand solution is 1.2-2.0 mM trimesic acid (BTC) solution, and the solvent is absolute ethanol.