CN114050239B - Silver nanocrystalline modified mesoporous metal oxide composite material and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of nano materials, and particularly relates to a silver nanocrystalline modified mesoporous metal oxide composite material and a preparation method thereof. Firstly, preparing silver nanocrystals coated with oleylamine and dispersing the silver nanocrystals into an organic solvent; dissolving amphiphilic block copolymer PEO-b-PS in an organic solvent to obtain a first transparent solution; adding an inorganic micromolecular precursor into an organic solvent to obtain a second transparent solution; uniformly mixing the two transparent solutions, and then adding the mixture into a dispersion liquid to obtain a colloid solution; standing and volatilizing the colloid solution at room temperature, drying, solidifying and grinding into powder; and calcining the powder in a nitrogen atmosphere in stages, and calcining the powder in an air atmosphere to obtain the mesoporous metal oxide composite material loaded by the silver nanocrystals. The invention effectively improves the loading capacity and uniformity of the mesoporous metal oxide, and the grain size and the mesoporous size of the loaded silver nanocrystalline are controllable and uniform, thereby improving the basic performance of the mesoporous metal oxide loaded by the silver nanocrystalline.

Description

A kind of silver nanocrystal-modified mesoporous metal oxide composite material and preparation method

Technical field

The invention belongs to the technical field of nanomaterials, and specifically relates to a silver nanocrystal-modified mesoporous metal oxide composite material and a preparation method.

Background technique

Ordered mesoporous materials are a new type of nanomaterials with adjustable and ordered mesoporous channel structure, high specific surface area, and large pore volume. Among them, mesoporous metal oxide materials have high specific surface area, pore volume, interconnected pores and abundant reactive sites, which can effectively promote the transmission of guest molecules and play a role in macromolecule adsorption, catalytic reactions, drug storage and transportation, etc. It has important applications and can be used to prepare gas sensors, etc. Resistive sensors based on semiconductor metal oxides are cheap, simple in structure, sensitive and fast in response, and easy to mass-produce. Therefore, they have become the most important type of sensor among gas sensors and a research hotspot. In addition, loading precious metals on metal oxides can make full use of the catalytic properties and sensitization properties of precious metals, effectively reduce the activation energy of surface reactions, increase the defects of the metal carrier, and increase the concentration of adsorbed oxygen, thereby further improving the performance of the gas sensor.

In the existing technology, the synthesis steps of precious metal-loaded mesoporous metal oxide composite materials are complicated, and the carrier or precious metal particles need to be prepared in advance; at the same time, the pore structure of the carrier is uncontrollable, and the stability and dispersion of the precious metal particles are poor, making it difficult to produce them on a large scale. Production. In addition, most of the synthesized materials have disordered mesopores, which is not conducive to material transport.

Contents of the invention

In view of the above-mentioned problems existing in the prior art, the object of the present invention is to provide a silver nanocrystal-modified mesoporous metal oxide composite material with high and uniform silver loading and excellent performance and a preparation method.

The present invention adopts a sol-gel chemical synthesis method, using amphiphilic block copolymers as structure guiding agents and pore-forming agents, inorganic small molecules as metal oxide precursors, and assembled with pre-synthesized silver nanocrystals. The solvent evaporation induced co-assembly (EICA) method loads uniformly sized and highly dispersed silver nanocrystals into mesoporous metal oxides to increase the loading capacity of mesoporous metal oxides and achieve the loading of silver nanocrystals. Precise control of nanocrystal size.

The preparation method of silver nanocrystal-modified mesoporous metal oxide composite materials provided by the present invention uses an amphiphilic block copolymer (PEO-b-PS) with a large molecular weight as a template agent and pore-forming agent. During the solvent evaporation process , the amphiphilic block copolymer will form micelles, and the electrostatic force between the hydrophilic end of the template agent (PEO) and the inorganic small molecule precursor (such as WCl6, etc.) forms the micelle shell, and the hydrophobic block ( PS) is pre-synthesized by hydrophobic interaction to wrap silver nanocrystals with predetermined sizes, and obtain ordered mesoscopic organic-inorganic composite materials through the solvent evaporation induced self-assembly (EISA) method. After high-temperature heat treatment with nitrogen and air, the mesoporous metal oxide composite material modified with silver nanocrystals is directly obtained.

The preparation method of the silver nanocrystal-modified mesoporous metal oxide composite material provided by the invention, the specific steps are:

Step A: Dissolve a predetermined proportion of silver nitrate and oleylamine in the first organic solvent and mix evenly with ultrasonic, then add a predetermined proportion of ascorbic acid and stir in the dark for 1-2 hours; add ethanol to the stirred solution for sedimentation. After centrifugation, a precipitate is obtained, and then the precipitate is washed and dried to obtain solid particles whose surface is coated with oleylamine silver nanocrystals.

This step is the process of preparing silver nanocrystals. The obtained silver nanocrystal solid particles have a high degree of crystallinity and a uniform particle size of 5-10 nm. They can be conveniently adjusted according to the feeding concentration and reaction time of silver nitrate; at the same time, the silver nanocrystals The surface of crystalline solid particles is covered with oleylamine. The silver nitrate accounts for 1-2wt.% of the solution quality, the oleylamine accounts for 45-50wt.% of the solution quality, and the ascorbic acid accounts for 2-4wt.% of the solution quality. The first organic solvent includes toluene, cyclohexane, n-hexane, benzene and other non-polar organic reagents.

Step B: Dispersing silver nanocrystals into a second organic solvent to obtain a silver nanocrystal dispersion liquid.

In this step, the concentration of silver nanocrystals in the obtained dispersion is 0.05-1.5wt.%. The second organic solvent includes: non-polar solvents such as cyclohexane, toluene, n-hexane or mixed solvents thereof.

Step C: Dissolve the amphiphilic block copolymer PEO-b-PS with large molecular weight in the third organic solvent and stir thoroughly to obtain a first transparent solution; add the inorganic small molecule precursor and hydrolysis inhibitor to tetrahydrofuran THF or absolute ethanol EtOH to obtain a second transparent solution; mix the first transparent solution and the second transparent solution evenly, add a predetermined proportion of the silver nanocrystal dispersion obtained in step B, and stir thoroughly to obtain a transparent colloidal solution.

In this step, the third organic solvent includes one or more of tetrahydrofuran, toluene, chloroform, and dimethylformamide.

The PEO block molecular weight of the amphiphilic block copolymer is 2000~5000 g/mol, and the PS block molecular weight is 10000~30000 g/mol; by controlling the activity or adjusting the time, temperature, feed ratio, etc. of the free radical polymerization reaction, By controlling the molecular weight of the amphiphilic block copolymer, the size of the mesopores can be adjusted through the molecular weight. The concentration of PEO-b-PS in the first transparent solution is 0.5-2wt.%.

The inorganic small molecule precursor is one or more of tungsten chloride, tetrabutyl titanate, aluminum acetylacetonate, and zirconium acetylacetonate; the inorganic small molecule precursors are all commercial reagents, which are convenient and easy to obtain. When the inorganic small molecule precursor is one component, a metal oxide is obtained, and silver nanocrystals are loaded in a mesoporous metal oxide; when the inorganic small molecule precursor is two or more types, two or more are obtained. One or more metal oxides, silver nanocrystals are loaded in the composite mesoporous metal oxide. Different inorganic small molecules are used as metal oxide precursors to synthesize silver nanocrystal modified WO ₃ , TiO ₂ , Al ₂ O ₃ , ZrO ₂ and other mesoporous metal oxides or composite mesoporous metal oxides in the reaction. The concentration of the inorganic small molecule precursor in the second transparent solution is 2-10wt.%. The hydrolysis inhibitor is one or more of acetylacetone, hydrochloric acid, acetic acid, and dilute nitric acid. The hydrolysis inhibitor controls the hydrolysis rate of tetrabutyl titanate to obtain porous inorganic oxides.

In this step, after the dispersion is added to the mixed solution, the silver nanocrystals in the dispersion are covered with oleylamine on the surface and can automatically assemble with the PS segments through hydrophobic interaction to avoid destroying the orderly accumulation of micelles and at the same time achieve silver nanocrystals. The nanocrystals are directly and uniformly loaded in the mesoporous channels.

Step D, transfer the colloidal solution to a petri dish, leave it to evaporate at room temperature for 12 hours, then dry the petri dish in an oven at 40-60°C for 12-24 hours, and finally transfer the petri dish to 80-100 The organic-inorganic composite film is cured in an oven at ℃ for 12-24 hours to obtain an organic-inorganic composite film. The composite film is scraped off from the petri dish and ground into powder.

Step E, place the obtained powder in a tube furnace, heat it to 300°C-350°C in a nitrogen atmosphere at a rate of 1-2°C/min for 2-4 hours, and then continue to heat it to 500°C at a rate of 1-5°C/min. Calcined at ℃-600℃ for 1-2 h, a mesoporous metal oxide-carbon composite material supported by silver nanocrystals was obtained.

In this step, the low-temperature carbonization method in a nitrogen atmosphere is used to convert the sp ² hybridized carbon atoms in the PS block and the carbon in the oleylamine into amorphous carbon in situ. When calcined in the air, the amorphous residual carbon - On the one hand, it serves as a rigid support to maintain the mesoporous structure during the high-temperature calcining and crystallization process of metal oxides. On the other hand, it can prevent the growth and migration of silver nanocrystals and serves as a sacrificial agent to prevent silver from being oxidized, limiting the particle size of silver nanocrystals to 5-10nm.

Step F: Place the obtained silver nanocrystal-supported mesoporous metal oxide-carbon composite material in a muffle furnace, and heat it to 450°C-600°C for 1-2 hours in an air atmosphere at 2-5°C/min to obtain Mesoporous metal oxides supported by silver nanocrystals.

The present invention also provides a mesoporous metal oxide composite material modified with silver nanocrystals prepared by the above preparation method. The composite material uses mesoporous metal oxide as a matrix and is uniformly loaded with silver nanocrystals in the mesoporous structure, and The pore size of mesopores is 30-40 nm, and the size of silver nanocrystal particles is 5-10 nm.

Wherein, the mesoporous metal oxide includes one or more combinations of WO ₃ , TiO ₂ , Al ₂ O ₃ , and ZrO ₂ .

It can be seen from the above technical solutions that the silver nanocrystal-modified mesoporous metal oxide composite material and preparation method provided by the embodiments of the present invention control the synthesis of Ag/WO ₃ and Ag/TiO by controlling the type of inorganic small molecule precursors. _2. Mesoporous metal oxide composite materials modified with various silver nanocrystals such as Ag/Al ₂ O ₃ and Ag/ZrO ₂ . The pore size of the mesopores of the synthesized composite material is 30-40 nm, and the size of the silver nanocrystal particles is 5-10 nm. The size of the mesopores of the composite material is controlled by controlling the molecular weight of the block copolymer, and the pre-synthesized silver nanocrystals are controlled by controlling the molecular weight of the block copolymer. The size and oleylamine ratio control the particle size of silver nanocrystals in the composite material, which effectively improves the loading amount and uniformity of silver in the mesoporous metal oxide, making the particle size of the loaded silver nanocrystals controllable and uniform, effectively improving the The stability of the silver precious metal loading greatly reduces the impact of the precious metal loading on the stability of the mesoporous skeleton, and improves the catalytic performance of the mesoporous metal oxide supported by silver nanocrystals.

Description of the drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. Those of ordinary skill in the art can also obtain other drawings based on these drawings without exerting creative efforts.

Figure 1 is a transmission electron microscope image of silver nanocrystal supported mesoporous tungsten trioxide Ag/WO ₃ provided in Embodiment 1 of the present invention;

Figure 2 is a transmission electron microscope image of silver nanocrystal supported mesoporous titanium dioxide Ag/TiO ₂ provided in Embodiment 2 of the present invention;

Figure 3 is a transmission electron microscope image of silver nanocrystal supported mesoporous aluminum oxide Ag/Al ₂ O ₃ provided in Embodiment 3 of the present invention;

Figure 4 is a transmission electron microscope image of silver nanocrystal supported mesoporous zirconia Ag/ZrO ₂ provided in Embodiment 4 of the present invention.

Detailed ways

The technical problems, technical solutions and advantages of the present invention will be elucidated in detail below with reference to exemplary embodiments. The exemplary embodiments described below are only used to explain the present invention and cannot be construed as limitations of the present invention. It will be understood by one of ordinary skill in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It should also be understood that terms such as those defined in general dictionaries are to be understood to have a meaning consistent with their meaning in the context of the prior art and are not used in an idealized or overly formal meaning unless defined herein. to explain.

Example 1:

This embodiment provides a silver nanocrystal-modified mesoporous tungsten oxide composite material and a preparation method thereof.

The preparation method includes the following steps:

Step A: Dissolve 85 mg silver nitrate and 4.05 g oleylamine in 5 ml toluene solution and sonicate evenly, then add 175 mg ascorbic acid and stir in the dark for 1 hour; add 80 ml ethanol to the stirred solution for sedimentation, and centrifuge A precipitate is obtained, and the silver nanocrystalline solid is obtained after washing and drying the precipitate;

Step B, disperse the silver nanocrystal solid into 10 ml cyclohexane solution to obtain a dispersion for later use;

Step C: Dissolve 75 mg of amphiphilic block copolymer (PEO- b -PS) with large molecular weight in 5 ml THF and stir thoroughly to obtain the first transparent solution; add 300 mg WCl ₆ and 300 μL acetylacetone to 1 ml of EtOH to obtain a second transparent solution; mix the first transparent solution and the second transparent solution evenly, add an appropriate amount of pre-synthesized silver nanocrystal dispersion, and stir thoroughly to obtain a transparent colloidal solution; the amphiphilic solution described in this example The molecular weight of the PEO segment of the linear block copolymer is 2000g/mol, and the molecular weight of the PS block is 10000g/mol;

Step D, transfer the colloidal solution to a petri dish, leave it at room temperature to evaporate for 12 hours, then transfer the petri dish to a 40°C oven for drying for 12 hours, and finally transfer the petri dish to a 100°C oven for curing for 12 hours. Obtain an organic-inorganic composite film, scrape the film from the petri dish and grind it into powder;

Step E: Place the obtained powder in a tube furnace, heat it to 350°C for 3 hours at 1°C/min in a nitrogen atmosphere, and then continue to heat it to 500°C for 1 hour at 5°C/min to obtain the silver nanocrystal load. Mesoporous tungsten oxide-carbon composite materials;

Step F, place the obtained silver nanocrystal-supported mesoporous metal oxide-carbon composite material in a muffle furnace, and heat it to 450° C. for 1 hour in an air atmosphere to obtain silver nanocrystal-supported mesopores. Tungsten oxide composite material Ag/WO ₃ .

Referring to Figure 1, the obtained Ag/WO ₃ composite material has mesoporous tungsten oxide as the matrix, and silver nanocrystals are evenly loaded in the mesoporous structure. The pore size of the mesopores is 35 nm, and the silver nanocrystal particle size is 7 nm.

Example 2:

This embodiment provides a silver nanocrystal-modified mesoporous titanium oxide composite material and a preparation method thereof.

The preparation method includes the following steps:

Step A: Dissolve 85 mg silver nitrate and 4.05 g oleylamine in 5 ml toluene solution and sonicate evenly, then add 175 mg ascorbic acid and stir for 1 h in the dark. Add 80 ml of ethanol to the stirred solution for sedimentation, centrifuge, and wash to obtain a silver nanocrystal solid;

Step B, disperse the silver nanocrystals into 10 ml n-hexane solution to obtain a dispersion for later use;

Step C, dissolve 75 mg of amphiphilic block copolymer (PEO- b -PS) with large molecular weight in 5 mL of chloroform, stir thoroughly to obtain the first transparent solution; add 600 μL of tetrabutyl titanate to 1 ml into THF, then add 75 μL each of hydrochloric acid and glacial acetic acid to obtain a second transparent solution; mix the first transparent solution and the second transparent solution evenly, add an appropriate amount of pre-synthesized silver nanocrystal dispersion, and stir thoroughly to obtain a transparent colloidal solution; The molecular weight of the PEO segment of the amphiphilic block copolymer is 5000g/mol, and the molecular weight of the PS block is 20000g/mol;

Step D, transfer the above colloidal solution to a petri dish, leave it at room temperature to evaporate for 12 hours, then transfer the petri dish to a 60°C oven for drying for 12 hours, and finally transfer the petri dish to an 80°C oven for curing for 24 hours to obtain Organic-inorganic composite film, scrape the film from the petri dish and grind it into powder;

In step E, the obtained powder sample is placed in a tube furnace and calcined in a nitrogen atmosphere at a temperature of 1°C/min to 350°C for 2 hours to obtain a silver nanocrystal-supported mesoporous titanium dioxide-carbon composite material;

Step F, place the obtained silver nanocrystal-supported mesoporous titanium dioxide-carbon composite material in a muffle furnace, and heat it up to 450° C. for 1 hour in an air atmosphere to obtain a silver nanocrystal-supported mesoporous titanium dioxide composite. Material.

Referring to Figure 2, the obtained Ag/TiO ₂ composite material has mesoporous titanium dioxide as the matrix, and silver nanocrystals are evenly loaded in the mesoporous structure. The pore size of the mesopores is 30 nm, and the silver nanocrystal particle size is 5 nm.

Example 3:

This embodiment provides a silver nanocrystal-modified mesoporous alumina composite material and a preparation method thereof.

The preparation method includes the following steps:

Step A: Dissolve 85 mg silver nitrate and 4.05 g oleylamine in 5 ml toluene solution and sonicate evenly, then add 175 mg ascorbic acid and stir for 1 h in the dark. Add 80 ml of ethanol to the stirred solution for sedimentation, centrifuge, and wash to obtain a silver nanocrystal solid;

Step B, disperse the silver nanocrystals into 10 ml of toluene solution to obtain a dispersion for later use;

Step C: Dissolve 75 mg of amphiphilic block copolymer (PEO- b -PS) with large molecular weight in 5 mL of dimethylformamide and stir thoroughly to obtain the first transparent solution; add 375 mg of aluminum acetylacetonate to 3 ml of THF, and then add 150 μL of concentrated nitric acid to obtain a second transparent solution; mix the first transparent solution and the second transparent solution evenly, add an appropriate amount of pre-synthesized silver nanocrystal dispersion, and stir thoroughly to obtain a transparent colloidal solution; so The molecular weight of the PEO segment of the amphiphilic block copolymer is 3000g/mol, and the molecular weight of the PS block is 15000g/mol;

Step D, transfer the above solution to a petri dish, leave it to evaporate at room temperature for 24 hours, then transfer the petri dish to a 50°C oven to dry for 18 hours, and finally transfer the petri dish to a 90°C oven to solidify for 18 hours to obtain an organic solution. -Inorganic composite film, scrape the film from the petri dish and grind it into powder;

In step E, the obtained powder sample is placed in a tube furnace and calcined in a nitrogen atmosphere at a temperature of 1°C/min to 350°C for 3 hours to obtain a silver nanocrystal-supported mesoporous alumina-carbon composite material;

Step F: Place the obtained silver nanocrystal-supported mesoporous alumina-carbon composite in a muffle furnace, and heat it up to 600°C for 2 hours at 5°C/min in an air atmosphere to obtain the silver nanocrystal-supported mesoporous alumina-carbon composite. Aluminum composite.

Referring to Figure 3, the obtained Ag/Al ₂ O ₃ composite material has mesoporous alumina as the matrix, and silver nanocrystals are evenly loaded in the mesoporous structure. The pore size of the mesopores is 40nm, and the silver nanocrystal particle size is 10nm. .

Example 4:

This embodiment provides a silver nanocrystal-modified mesoporous zirconium dioxide composite material and a preparation method thereof.

The preparation method includes the following steps:

Step A, dissolve 85 mg silver nitrate and 4.05 g oleylamine in 5 ml toluene solution and sonicate evenly, then add 175 mg ascorbic acid and stir for 1 h in the dark. Add 80 ml of ethanol to the stirred solution for sedimentation, centrifuge, and wash to obtain a silver nanocrystal solid;

Step B, disperse the silver nanocrystals into 10 ml of cyclohexane solution to obtain a dispersion for later use;

Step C, dissolve 75 mg of amphiphilic block copolymer (PEO- b -PS) with large molecular weight in 5 mL of toluene, stir thoroughly to obtain the first transparent solution; add 375 mg of zirconium acetylacetonate into 3 ml of THF , then add 150 μL of concentrated nitric acid to obtain a second transparent solution; mix the first transparent solution and the second transparent solution evenly, add an appropriate amount of pre-synthesized silver nanocrystal dispersion, and stir thoroughly to obtain a transparent colloidal solution; the amphiphilic The molecular weight of the PEO segment of the block copolymer is 4000g/mol, and the molecular weight of the PS block is 18000 g/mol;

Step D, transfer the above colloidal solution to a petri dish, leave it to evaporate at room temperature for 24 hours, then transfer the petri dish to a 40°C oven for drying for 24 hours, and finally transfer the petri dish to a 100°C oven for curing for 12 hours to obtain Organic-inorganic composite film, scrape the film from the petri dish and grind it into powder;

In step E, the obtained powder sample is placed in a tube furnace and calcined in a nitrogen atmosphere at a temperature of 1°C/min to 350°C for 3 hours to obtain a silver nanocrystal-supported mesoporous zirconia-carbon composite material;

Step F, place the obtained silver nanocrystal-supported mesoporous zirconia-carbon composite material in a muffle furnace, and heat it up to 600°C for 2 hours at 5°C/min in an air atmosphere to obtain the silver nanocrystal-supported mesoporous zirconia-carbon composite material. Zirconium composites.

Referring to Figure 4, the obtained Ag/Al ₂ O ₃ composite material has mesoporous zirconium dioxide as the matrix, and silver nanocrystals are evenly loaded in the mesoporous structure. The pore size of the mesopores is 38nm, and the silver nanocrystal particle size is 6nm.

The above are preferred embodiments of the present invention. It should be noted that the present invention is not limited to the exemplary embodiments disclosed above. The essence of the description is only to help those skilled in the relevant fields comprehensively understand the specific details of the present invention. For those of ordinary skill in the art, without departing from the principles described in the present invention, several improvements and modifications, easily conceivable changes or substitutions made within the technical scope disclosed in the present invention should be covered by within the protection scope of the present invention.

Claims (10)

1. The preparation method of the mesoporous metal oxide composite material modified by silver nanocrystals is characterized in that an amphiphilic block copolymer is used as a structure guiding agent and a pore-forming agent through a sol-gel chemical synthesis method, inorganic small molecules are used as metal oxide precursors, and are assembled with silver nanocrystals synthesized in advance, and silver nanocrystals which are uniform in size and are highly dispersed are loaded in mesoporous metal oxide through a solvent volatilization induction co-assembly method, so that the loading capacity of the mesoporous metal oxide is improved, and the accurate regulation and control of the size of the loaded silver nanocrystals are realized; the method comprises the following specific steps:

step A, dissolving silver nitrate and oleylamine in a first organic solvent in a preset proportion, uniformly mixing by ultrasound, adding ascorbic acid in a preset proportion, and uniformly stirring in a dark place; adding ethanol into the stirred solution for sedimentation, centrifuging to obtain a precipitate, washing and drying the precipitate to obtain solid particles coated with oleylamine silver nanocrystals on the surface;

step B, dispersing silver nanocrystals into a second organic solvent to obtain silver nanocrystal dispersion;

step C, dissolving an amphiphilic block copolymer PEO-b-PS with a large molecular weight in a third organic solvent, and fully stirring to obtain a first transparent solution; adding an inorganic micromolecular precursor and a hydrolysis inhibitor into tetrahydrofuran THF or ethanol EtOH to obtain a second transparent solution; uniformly mixing the first transparent solution and the second transparent solution, adding the silver nanocrystalline dispersion liquid with a preset proportion, and fully stirring to obtain a transparent colloid solution;

step D, transferring the transparent colloid solution into a culture dish, standing and volatilizing for 12 hours at room temperature, then drying the culture dish in a baking oven at 40-60 ℃ for 12-24 hours, finally transferring the culture dish into a baking oven at 80-100 ℃ for curing for 12-24 hours to obtain an organic-inorganic composite film, scraping the composite film from the culture dish and grinding the composite film into powder;

step E, placing the obtained powder into a tube furnace, heating to 300-350 ℃ at a heating rate of 1-2 ℃/min in a nitrogen atmosphere, calcining 2-4 h, and continuously heating to 500-600 ℃ at a heating rate of 1-5 ℃/min to calcine 1-2h to obtain the silver nanocrystalline loaded mesoporous metal oxide-carbon composite material;

and F, heating the obtained silver nanocrystalline loaded mesoporous metal oxide-carbon composite material to 450-600 ℃ at a heating rate of 2-5 ℃/min in an air atmosphere, and calcining for 1-2h to obtain the silver nanocrystalline loaded mesoporous metal oxide.

2. The method for preparing a silver nanocrystalline modified mesoporous metal oxide composite according to claim 1, wherein silver nitrate in the step a accounts for 1-2wt.% of the mass of the solvent, oleylamine accounts for 45-50wt wt.% of the mass of the solvent, and ascorbic acid accounts for 2-4wt.% of the mass of the solvent; the concentration of silver nanocrystals in the dispersion of step B was 0.05-1.5wt.%.

3. The method for preparing a silver nanocrystalline modified mesoporous metal oxide composite according to claim 1, wherein the first organic solvent is selected from the group consisting of non-polar organic reagents toluene, cyclohexane, n-hexane, benzene; the second organic solvent is selected from nonpolar solvents such as cyclohexane, toluene and n-hexane; the third organic solvent is selected from tetrahydrofuran, toluene, chloroform and dimethylformamide.

4. The method for preparing a silver nanocrystalline modified mesoporous metal oxide composite according to claim 1, wherein in the step C, the molecular weight of PEO block of the amphiphilic block copolymer is 2000-5000 g/mol, and the molecular weight of PS block is 10000-30000 g/mol.

5. The method for preparing a silver nanocrystalline modified mesoporous metal oxide composite according to claim 1, wherein the molecular weight of the amphiphilic block copolymer is controlled by controlling the activity or adjusting the time, temperature and feed ratio of the free radical polymerization reaction, and the size of the mesoporous pore diameter can be adjusted by the size of the molecular weight.

6. The method of preparing a silver nanocrystalline modified mesoporous metal oxide composite according to claim 1, wherein PEO-b-PS concentration in the first transparent solution is 0.5 to 2wt.%; the concentration of the inorganic small molecule precursor in the second transparent solution is 2-10wt.%.

7. The method for preparing the silver nanocrystalline modified mesoporous metal oxide composite material according to claim 1, wherein the inorganic small molecule precursor is one or more of tungsten chloride, tetrabutyl titanate, aluminum acetylacetonate and zirconium acetylacetonate, and the hydrolysis inhibitor is one or more of acetylacetone, hydrochloric acid, acetic acid and dilute nitric acid.

8. The method for preparing a silver nanocrystalline modified mesoporous metal oxide composite according to claim 1, wherein the particle size of silver nanocrystalline supported in the mesoporous metal oxide in step F is 5 to 10nm.

9. The method for preparing a silver nanocrystalline modified mesoporous metal oxide composite according to claim 1, wherein the mesoporous metal oxide is selected from WO ₃ 、TiO ₂ 、Al ₂ O ₃ 、ZrO ₂ One of them.

10. A silver nanocrystalline modified mesoporous metal oxide composite material prepared by the method of any one of claims 1 to 9, wherein the composite material uses mesoporous metal oxide as a matrix, silver nanocrystalline is uniformly loaded in a mesoporous structure, the pore size of mesopores is 30 to 40nm, and the particle size of silver nanocrystalline is 5 to 10nm.