WO2023206781A1 - Vesicle-type mof/go composite material and preparation method therefor - Google Patents

Abstract

Disclosed in the present disclosure are a vesicle-type MOF/GO composite material and a preparation method therefor. The method comprises the following steps: carrying out oxidative stripping treatment on graphite to obtain a graphene oxide; dispersing the graphene oxide in an aqueous solution to obtain a graphene oxide dispersion; preparing an oil phase solution and an aqueous phase solution, the oil phase solution being prepared by dissolving organic ligands in a water-insoluble organic solvent, the aqueous phase solution comprising a deionized water solution in which a metal salt is dissolved and the graphene oxide dispersion; mixing the oil phase solution and the aqueous phase solution, emulsifying a mixed solution to obtain an emulsion, and heating the emulsion, so as to grow MOF crystal grains on the surface of the graphene oxide; adding a certain quantity of the organic ligands and of the metal salt again, and carrying out emulsification again; and heating an emulsion obtained after emulsification, so as to promote growth of the MOF crystal grains, thereby obtaining a vesicle-type MOF/GO composite material. The vesicle-type composite material has an excellent adsorption characteristic, and can achieve an effective selective adsorption of a specified component.

Description

Vesicle MOF/GO composite materials and preparation methods thereof

Cross-references to related applications

This application is filed based on the Chinese patent application with application number 202210438095.

Technical field

The present disclosure belongs to the technical field of composite materials, and particularly relates to a vesicle-type MOF/GO composite material and a preparation method thereof.

Background technique

With the continuous development of social economy, global warming caused by the greenhouse effect has become an urgent problem for mankind to solve. Industrial development, economic growth, and human life are all inseparable from energy. Therefore, we need to continuously develop new technologies and create new materials to reduce the impact of greenhouse gases on the environment and climate.

Metal-organic framework (MOF) materials have excellent properties such as high porosity, controllable structure, and easy modification. However, they also have some shortcomings, such as poor chemical stability and thermal stability, which to a large extent This limits the application development of MOF. In order to realize the application of MOF in actual production, new functions need to be introduced to enhance the characteristics of the material.

As the most popular carbon material, graphene has a unique structure and properties. Graphene is composed of a single layer of carbon atoms arranged in a 2D honeycomb lattice configuration. Graphene is oxidized using a strong oxidant and then peeled off to obtain graphene oxide (GO). GO sheets have good hydrophilic properties and dispersion properties in solutions. After being combined with MOF materials, it can solve the problem of poor water resistance of MOF materials and improve the stability, dispersion and biocompatibility of MOF materials in aqueous solutions.

Existing MOF-GO composite materials are made by dispersing metal framework materials in graphene oxide aqueous solution; the MOF in the composite material produced by this method is unevenly dispersed on the surface of graphene oxide and has poor stability. , thus affecting the performance of MOF-GO composite materials.

Contents of the invention

In order to solve the above technical problems, the purpose of this disclosure is to provide a vesicle-type MOF/GO composite material and a preparation method thereof. The vesicle-type composite material has a hollow vesicle structure in which the MOF particles are evenly dispersed on the graphene surface. It has good properties and stability and can be used in catalytic purification, gas adsorption and other fields. It has excellent adsorption characteristics and can achieve effective and selective adsorption of specified components.

In order to achieve the above technical objectives and achieve the above technical effects, the present disclosure is implemented through the following technical solutions:

A method for preparing vesicle MOF/GO composite materials, including the following steps:

Step 1: Use the Hummers method to oxidize and peel graphite to obtain graphene oxide;

Step 2, disperse the prepared graphene oxide in an aqueous solution and perform ultrasonic dispersion to obtain a graphene oxide dispersion;

Step 3: Prepare an oil phase solution and an aqueous phase solution; wherein, the oil phase solution is prepared by dissolving the organic ligand in a water-insoluble organic solvent; the aqueous phase solution includes a deionized aqueous solution in which a metal salt is dissolved and the solution prepared in step 2 The obtained graphene oxide dispersion;

Step 4: Mix the oil phase solution and the water phase solution, use an emulsifier to emulsify the mixed solution to obtain an emulsion, heat the emulsion to 50-60°C, and maintain it for 1-2 hours to grow MOF crystals on the surface of graphene oxide. grain;

Step 5: Add a certain amount of the organic ligand and metal salt described in Step 3 to the reaction system of Step 4 again, and emulsify again;

Step 6: Heat the emulsion obtained after emulsification in Step 5 to 50-60°C and maintain it for 1-2 hours to promote the growth of MOF grains and obtain a vesicle-type MOF/GO composite material.

In some embodiments, the organic ligand is methylimidazole.

In some embodiments, the water-insoluble organic solvent is octanol.

In some embodiments, the cationic element of the metal salt is selected from one or more of cobalt, iron, nickel, copper, zinc, platinum, palladium, ruthenium, gold, silver, indium, and zirconium.

In some embodiments, the anion of the metal salt is selected from one or more of acetate ion, sulfate ion, nitrate ion, chloride ion, phosphate ion, formate ion, and oxalate ion.

In some embodiments, the concentration of the graphene oxide dispersion is 2 to 3 mg/mL.

In some embodiments, the mixing volume ratio of the oil phase solution, the deionized water solution in which the metal salt is dissolved, and the graphene oxide dispersion is 1:1:1.

In some embodiments, the concentration of the oil phase solution is 10-15 mg/mL.

In some embodiments, in the deionized water solution in which the metal salt is dissolved, the concentration of the metal salt is 5˜8 mg/mL.

In some embodiments, the mass of the organic ligand added in step 5 is 2 to 3 times the mass of the organic ligand in the oil phase solution in step 3.

In some embodiments, the mass of the metal salt added in step 5 is 2 to 2.5 times the mass of the metal salt in the aqueous solution in step 3.

In some embodiments, an emulsifier is used to mix the oil phase solution and the aqueous phase solution at a rotation speed of 10,000 rpm for 5 minutes to obtain an emulsion.

The present disclosure further provides a vesicle-type MOF/GO composite material, which is prepared using the above preparation method; the composite material uses graphene oxide emulsion droplets as capsules, and dense MOF nanocrystals grow on the surface of the graphene oxide emulsion droplets. .

In some embodiments, the particle size of a single graphene oxide emulsion droplet is 50 μm, and the particle size of the MOF nanocrystal is 50-80 nm.

Beneficial effects of this disclosure:

This disclosure uses GO sheets as stabilizers to prepare emulsions, and induces the coordination and nucleation of MOF at its oil-water interface to prepare preliminary MOF/GO composite materials. Then, it is secondarily processed by increasing the concentration of metal salts and organic ligands. Secondary emulsification, an emulsion using the preliminary MOF/GO composite material as a stabilizer is produced, and then heated to promote further growth of MOF crystals on the interface, a vesicle-type MOF/GO composite material can be produced.

The disclosed method uses emulsion as a template to grow nanoparticles in situ through the interface to obtain vesicle-type MOF/GO composite materials. It is a very simple, convenient and effective method; using graphene oxide and the initially formed MOF/ The emulsion formed by GO composite material as a stabilizer has a large liquid/liquid interface, which can provide a stable platform for the in-situ growth of MOF nanoparticles, so that the nanoparticles on the interface continue to increase and gradually accumulate to a certain extent. This vesicle composite material was obtained.

The vesicle composite material of the present disclosure has a hollow structure, using graphene oxide emulsion droplets as capsules, and dense MOF nanocrystals are grown on the surface of the graphene oxide emulsion droplets to form a composite material.

This disclosure obtains a vesicle composite material by chemically modifying graphene oxide; the MOF nanocrystals in the vesicle composite material are evenly and densely distributed on the surface of graphene oxide, and the recombination rate on graphene oxide is Higher, better stability, can better improve the adsorption and other properties of vesicle composite materials.

The disclosed vesicle MOF/GO composite material has good stability, uniform dispersion and biocompatibility, and has excellent adsorption characteristics. It can be used in catalytic purification, gas adsorption and other fields, and can realize the control of designated groups. It can selectively adsorb and separate many toxic gases, including H ₂ S, NH ₃ and NO ₂ .

Description of the drawings

Figure 1 is a material morphology diagram of Example 1 of the present disclosure; (a) is the internal morphology diagram of the powder prepared after drying the MOF-seed/GO composite material; (b) is the vesicle-type MOF/GO composite material of the present disclosure. Internal morphology of the powder after drying of the GO composite material; (c) is a laser confocal image of the vesicle MOF/GO composite material of the present disclosure.

Detailed ways

The preferred embodiments of the present disclosure are described in detail below in conjunction with the accompanying drawings, so that the advantages and features of the present disclosure can be more easily understood by those skilled in the art, and the protection scope of the present disclosure can be more clearly defined.

The present disclosure provides a method for preparing vesicle MOF/GO composite materials, which includes the following steps:

Step 1: Use the Hummers method to oxidize and peel graphite to obtain graphene oxide;

Step 2: Disperse the prepared graphene oxide in an aqueous solution and disperse it ultrasonically for 1 to 1.5 hours to obtain a graphene oxide dispersion; the concentration of the graphene oxide dispersion is 2 to 3 mg/mL;

Step 3: Prepare an oil phase solution and an aqueous phase solution; wherein, the oil phase solution is prepared by dissolving the organic ligand in a water-insoluble organic solvent; the aqueous phase solution includes a deionized aqueous solution in which a metal salt is dissolved and the solution prepared in step 2 The obtained graphene oxide dispersion; the concentration of the oil phase solution is 10-15 mg/mL; in the deionized water solution in which the metal salt is dissolved, the concentration of the metal salt is 5-8 mg/mL; the organic ligand is preferably methyl Imidazole; the water-insoluble organic solvent is preferably octanol;

Step 4: Mix the oil phase solution and the water phase solution, use an emulsifier to emulsify the mixed solution to obtain an emulsion, heat the emulsion to 50-60°C, and maintain it for 1-2 hours to grow MOF crystals on the surface of graphene oxide. particles; wherein, the mixing volume ratio of the oil phase solution, the deionized water solution with the metal salt dissolved, and the graphene oxide dispersion is 1:1:1;

Step 5: Add a certain amount of the organic ligand and metal salt described in step 3 to the product of step 4 again, and emulsify again; the mass of the organic ligand added in step 5 is the oil phase solution of step 3 2 to 3 times the mass of the organic ligand in the solution; the mass of the metal salt added in step 5 is 2 to 2.5 times the mass of the metal salt in the aqueous solution of step 3;

Step 6: Heat the emulsion obtained after emulsification in Step 5 to 50-60°C and maintain it for 1-2 hours to promote the growth of MOF grains and obtain a vesicle-type MOF/GO composite material.

Wherein, the cation element of the metal salt is selected from one or more of cobalt, iron, nickel, copper, zinc, platinum, palladium, ruthenium, gold, silver, indium and zirconium; the anion is selected from acetate ion, sulfuric acid One or more of radical ions, nitrate ions, chloride ions, phosphate ions, formate ions, and oxalate ions.

This vesicle-type MOF/GO composite material uses graphene oxide emulsion droplets as capsules. Dense MOF nanocrystals grow on the surface of the graphene oxide emulsion droplets, and the dense MOF nanocrystals form a shell covering the vesicles; among them, a single oxidized The particle size of graphene emulsion droplets is about 50 μm, and the particle size of MOF nanocrystals is 50-80 nm.

Example 1

The preparation method of the vesicle MOF/GO composite material of Example 1 includes the following steps:

Step 1: Use the Hummers method to oxidize and peel graphite to obtain graphene oxide;

Step 2: Disperse the prepared graphene oxide in an aqueous solution and ultrasonically disperse it for 1 hour to obtain a graphene oxide dispersion with a concentration of 2 mg/mL;

Step 3, prepare an oil phase solution and an aqueous phase solution; wherein, the oil phase solution is an octanol solution (5 mL) in which 68.7 mg of methylimidazole is dissolved; the aqueous phase solution includes a solution in which ZnSO ₄ .7H ₂ O (32.3 mg) is dissolved. Deionized water solution (5mL) and graphene oxide dispersion (5mL).

Step 4: Mix the above-mentioned oil phase solution and aqueous phase solution, and use a high-shear emulsifier B25 to emulsify the mixed solution at a rotation speed of 10,000 rpm for 5 minutes to obtain an emulsion; heat the emulsion to 60°C and maintain it for 1 hour. Promote the growth of MOF grains on the surface of graphene oxide, and name the prepared preliminary composite product MOF-seed/GO composite 1;

The MOF precursor methylimidazole ligand (MIM) is dissolved in n-octanol, and the metal ions are dissolved in the aqueous solution. After the emulsification process, the water/oil system composed of n-octanol and water forms a system with GO as the stabilizer. Emulsion; the emulsion is very stable, the surface of the droplets is smooth, and the size of the droplets is uniform, with the diameter of each droplet being approximately 50 μm;

Since MIM has weak water solubility, it will diffuse toward the GO emulsion interface, while metal ions are adsorbed on the GO surface through electrostatic interaction and coordination with the oxygen-containing functional groups of GO; therefore, MOF nanoparticles can easily The water/oil interface is coordinated and assembled to obtain MOF-seed/GO composite material 1;

Step 5: Add 205.6 mg methylimidazole and 69.0 mg ZnSO ₄ .7H ₂ O to the reaction system in step 4, and use a high shear emulsifier to emulsify the mixture again at 10,000 rpm to produce MOF-seed /GO composite material 1 is an emulsion of stabilizer;

Step 6: Heat the emulsion obtained after emulsification in Step 5 to 60°C and maintain it for 1 hour to promote the growth of MOF grains and obtain vesicle MOF/GO composite material 1, that is, hollow ZIF-8/GO composite material;

In order to further synthesize hollow composites, MOF grains need to grow further on the interface; therefore, step 6 uses MOF-seed/GO composite 1 as an emulsion stabilizer to promote the continued growth of MOF crystals on the MOF-seed/GO stabilized emulsion surface. ; When dense MOF nanocrystals grow on the surface of the emulsion droplets, vesicle-type MOF/GO composite material 1 (hollow MOF/GO composite material) is obtained; in step 6, the MOF nanoparticles grow more densely and are tightly gathered in GO surface, forming a shell layer of hollow ZIF-8/GO composite material.

Example 2

The preparation method of the vesicle MOF/GO composite material in Example 2 includes the following steps:

Step 1: Use the Hummers method to oxidize and peel graphite to obtain graphene oxide;

Step 2: Disperse the prepared graphene oxide in an aqueous solution and ultrasonically disperse it for 1 hour to obtain a graphene oxide dispersion with a concentration of 2 mg/mL;

Step 3, prepare an oil phase solution and an aqueous phase solution; wherein, the oil phase solution is an octanol solution (5 mL) in which 75 mg of methylimidazole is dissolved; the aqueous phase solution includes a deionized water solution (30 mg) in which zinc nitrate hexahydrate (30 mg) is dissolved. 5mL) and graphene oxide dispersion (5mL).

Step 4: Mix the above-mentioned oil phase solution and aqueous phase solution, and use a high-shear emulsifier B25 to emulsify the mixed solution at a rotation speed of 10,000 rpm for 5 minutes to obtain an emulsion; heat the emulsion to 60°C and maintain it for 1 hour. Promote the growth of MOF grains on the surface of graphene oxide, and name the prepared preliminary composite product MOF-seed/GO composite 2;

Step 5: Add 187.5 mg methylimidazole and 66.0 mg zinc nitrate hexahydrate to the reaction system in step 4, and use a high shear emulsifier to emulsify the mixture again at 10,000 rpm to produce MOF-seed/GO Composite material 2 is an emulsion of stabilizer;

Step 6: Heat the emulsion obtained after emulsification in Step 5 to 60°C and maintain it for 1 hour to promote the growth of MOF grains and obtain vesicle MOF/GO composite material 2, which is a hollow ZIF-8/GO composite material.

Composite material morphology observation

Use a transmission electron microscope (TEM, JEOL JEM-2100) to observe the internal morphology of the powder prepared after drying the MOF-seed/GO composite material of Example 1, as shown in (a) of Figure 1; from Figure (a) ) It can be seen that GO sheets, as stabilizers for emulsions, fully realize peeling and extension during the interfacial growth of MOF grains; crystal particles of about 30-50nm are distributed on large exfoliated and dispersed GO sheets.

A transmission electron microscope (TEM, JEOL JEM-2100) was used to observe the internal morphology of the powder prepared after drying the vesicle MOF/GO composite material of Example 1, as shown in (b) of Figure 1; from Figure ( b) It can be seen that crystal particles of about 50-80nm are distributed on the surface of large GO, the particle diameter becomes larger, and the distribution is more dense.

Use a laser confocal microscope (Nikon H550S) to observe the emulsion surface morphology of the vesicle MOF/GO composite material in Example 1, as shown in (c) in Figure 1. The surface morphology of a single emulsion droplet can be observed from Figure (c). Each emulsion droplet is about 50 μm in size, with crystal particles evenly distributed on the surface. After drying, the structure of the emulsion droplet is broken, and the structure of the GO and MOF crystal particles can be obtained. composite materials.

The disclosed vesicle MOF/GO composite material can be used directly or after drying. It can be widely used in catalytic purification, gas adsorption and other fields to achieve selective adsorption of specified components.

The above are only examples of the present disclosure, and do not limit the patent scope of the present disclosure. Any equivalent structure or equivalent process transformation made using the contents of the disclosure description and drawings, or directly or indirectly applied to other related technologies fields are equally included in the scope of patent protection of this disclosure.

Claims (14)

A method for preparing vesicle MOF/GO composite materials, including the following steps: Step 1: Use the Hummers method to oxidize and peel graphite to obtain graphene oxide; Step 2, disperse the prepared graphene oxide in an aqueous solution and perform ultrasonic dispersion to obtain a graphene oxide dispersion; Step 3: Prepare an oil phase solution and an aqueous phase solution; wherein, the oil phase solution is prepared by dissolving the organic ligand in a water-insoluble organic solvent; the aqueous phase solution includes a deionized aqueous solution in which a metal salt is dissolved and the solution prepared in step 2 The obtained graphene oxide dispersion; Step 4: Mix the oil phase solution and the water phase solution, use an emulsifier to emulsify the mixed solution to obtain an emulsion, heat the emulsion to 50-60°C, and maintain it for 1-2 hours to grow MOF crystals on the surface of graphene oxide. grain; Step 5: Add a certain amount of the organic ligand and metal salt described in Step 3 to the reaction system of Step 4 again, and emulsify again; Step 6: Heat the emulsion obtained after emulsification in Step 5 to 50-60°C and maintain it for 1-2 hours to promote the growth of MOF grains and obtain a vesicle-type MOF/GO composite material. The preparation method according to claim 1, wherein the organic ligand is methylimidazole. The preparation method according to claim 1 or 2, wherein the water-insoluble organic solvent is octanol. The preparation method according to any one of claims 1 to 3, wherein the cationic element of the metal salt is selected from the group consisting of cobalt, iron, nickel, copper, zinc, platinum, palladium, ruthenium, gold, silver, indium and zirconium. one or several kinds. The preparation method according to any one of claims 1 to 4, wherein the anion of the metal salt is selected from the group consisting of acetate ion, sulfate ion, nitrate ion, chloride ion, phosphate ion, formate ion, and oxalate ion. One or more types of ions. The preparation method according to any one of claims 1 to 5, wherein the concentration of the graphene oxide dispersion is 2 to 3 mg/mL. The preparation method according to any one of claims 1 to 6, wherein the mixing volume ratio of the oil phase solution, the deionized water solution in which the metal salt is dissolved, and the graphene oxide dispersion is 1:1:1. The preparation method according to any one of claims 1 to 7, wherein the concentration of the oil phase solution is 10 to 15 mg/mL. The preparation method according to any one of claims 1 to 8, wherein in the deionized water solution in which the metal salt is dissolved, the concentration of the metal salt is 5 to 8 mg/mL. The preparation method according to any one of claims 1 to 9, wherein the mass of the organic ligand added in step 5 is 2 to 3 times the mass of the organic ligand in the oil phase solution of step 3. The preparation method according to any one of claims 1 to 10, wherein the mass of the metal salt added in step 5 is 2 to 2.5 times the mass of the metal salt in the aqueous solution of step 3. The preparation method according to any one of claims 1 to 11, wherein an emulsifier is used to mix the oil phase solution and the aqueous phase solution at a rotation speed of 10,000 rpm for 5 minutes to obtain an emulsion. A vesicle-type MOF/GO composite material, which is prepared by the preparation method described in any one of claims 1 to 12, using graphene oxide emulsion droplets as capsules, and the surface growth of the graphene oxide emulsion droplets There are dense MOF nanocrystals. The composite material according to claim 13, wherein the particle size of the graphene oxide emulsion droplets is 50 μm, and the particle size of the MOF nanocrystals is 50-80 nm.

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