A "core-shell" structure Ce-BTC@MIL-125 catalyst for photocatalytic CO2 reduction reaction and its preparation method

Abstract

The invention discloses a method for photocatalytic CO 2 The "core-shell" structure Ce-BTC@MIL-125 catalyst for reduction reaction and its preparation method belong to the field of photocatalytic technology. The structure of the "core-shell" structure Ce-BTC@MIL-125 catalyst includes: Ce-BTC as the core and a MIL-125 nanoparticle shell grown in situ around Ce-BTC. The "core-shell" structure Ce-BTC@MIL-125 catalyst obtained by the present invention has excellent stability and large specific surface area. At the same time, the constructed heterogeneous structure realizes the efficient separation of photogenerated electron-hole pairs, showing excellent photocatalytic CO 2 Reduction activity.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysts, and in particular to a "core-shell" structure Ce-BTC@MIL-125 catalyst for photocatalytic CO2 reduction reaction and a preparation method thereof. Background Art

[0002] The rapid consumption of fossil fuels has led to an increasing concentration of atmospheric carbon dioxide, which is the main cause of global warming. To address this problem, a lot of effort has been invested in the capture, storage, and utilization of carbon dioxide. Among them, the conversion of carbon dioxide into high-value-added chemicals provides a promising route for the removal of excess carbon dioxide and the output of chemical raw materials. However, as an interesting strategy, the main challenge in this case is the high energy required for C=O bond cleavage. Among the various developed carbon dioxide conversion technologies, photocatalytic carbon dioxide reduction reaction is considered to be a preferred strategy that can directly convert renewable solar energy into chemical energy, resulting in the emergence of new photocatalysts in recent years. The photocatalytic performance of photocatalysts is mainly determined by the efficiency of light utilization, charge transfer, and surface reactions. In the development of photocatalysts, many explorations have focused on enhancing these factors; however, the activity of photocatalytic carbon dioxide reduction is still low and cannot meet the needs of current environmental and energy issues. Therefore, the development of new photocatalysts for the reduction of carbon dioxide is very necessary.

[0003] In recent years, as a unique class of porous crystalline materials, metal-organic frameworks (MOFs) composed of metal nodes and organic linkers have shown excellent performance in gas adsorption / separation, catalysis, energy conversion, chemical sensing and other fields due to their advantages such as high porosity, regular pore structure and flexible topology. According to recent studies, many MOF structures can exhibit semiconductor properties, making them potentially useful as photocatalysts. In the field of photocatalytic CO2 reaction, MOF-based photocatalysts have finely designed band gaps, catalytic active sites and efficient charge transfer pathways due to the high degree of regulation of metal nodes and organic linkers. In addition, the pores of MOFs can have adjustable pore sizes and surface chemistry, which is conducive to the rational design of efficient MOF-based photocatalysts with enhanced CO2 capture capabilities. Therefore, in view of the above advantages, the preparation of MOF-based photocatalysts for CO2 reduction has attracted widespread attention. Summary of the invention

[0004] The purpose of the present invention is to provide a "core-shell" structure Ce-BTC@MIL-125 catalyst for photocatalytic CO2 reduction reaction and a preparation method thereof. The present invention organically combines the advantages of two single MOFs, first preparing Ce-BTC as the core; then in situ growing MIL-125 nanoparticles on the surface of Ce-BTC as the shell to form a "core-shell" structure Ce-BTC@MIL-125. The constructed heterojunction structure effectively increases the utilization rate of visible light, realizes the efficient separation of photogenerated electron-hole pairs, and effectively overcomes the shortcomings of a single MOF with a narrow light response range and a high carrier recombination rate.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is to provide a "core-shell" structure Ce-BTC@MIL-125 catalyst for photocatalytic CO2 reduction reaction, the structure comprising: Ce-BTC as the core and a MIL-125 nanoparticle shell grown in situ around Ce-BTC.

[0007] The second technical solution of the present invention is to provide a method for preparing the above-mentioned "core-shell" structure Ce-BTC@MIL-125 catalyst for photocatalytic CO2 reduction reaction, comprising the following steps:

[0008] (1) Preparation of Ce-BTC;

[0009] (2) Ce-BTC and polyvinyl pyrrolidone are dispersed in a mixed solution of N,N-dimethylformamide and methanol and immersed; metal salts and ligands that form MIL-125 are added, and after the reaction is completed, a Ce-BTC@MIL-125 catalyst with a "core-shell" structure is obtained.

[0010] The preparation steps of Ce-BTC in step (1) include:

[0011] The cerium salt and the ligand are dissolved in a mixed solution of N,N-dimethylformamide and water, and Ce-BTC is obtained after the reaction is completed;

[0012] Preferably, the cerium salt is cerium nitrate hexahydrate, the ligand is trimesic acid; the volume ratio of N,N-dimethylformamide to water is 1:1 to 8:1; the reaction temperature is 80-120°C; the reaction time is 12-36 hours;

[0013] More preferably, the volume ratio of N,N-dimethylformamide to water is 5:1; the reaction temperature is 100° C.; and the reaction time is 24 hours.

[0014] Preferably, in step (2), the molar ratio of Ce-BTC to polyvinyl pyrrolidone is 10:1 to 1:10; the volume ratio of N,N-dimethylformamide to methanol is 5:1 to 10:1; the soaking time is 0.5 to 2 hours; the metal salt is a titanium salt; the ligand is one of unsubstituted terephthalic acid or terephthalic acid substituted with a substituent, and the substituent is selected from any one of amino, carboxyl, hydroxyl or halogen; the molar ratio of the metal salt to the ligand is 5:1 to 1:5; the stirring time is 15-60 minutes; the reaction temperature is 120-160°C; and the reaction time is 15-30 hours;

[0015] More preferably, the molar ratio of Ce-BTC to polyvinyl pyrrolidone is 1:1; the volume ratio of N,N-dimethylformamide to methanol is 9:1; the immersion time is 1 hour; the metal salt is tetrabutyl titanate; the ligand is 2-aminoterephthalic acid; the molar ratio of the metal salt to the ligand is 5:3; the stirring time is 20 minutes; the reaction temperature is 150°C; and the reaction time is 24 hours.

[0016] The third technical solution of the present invention is to provide a "core-shell" structure Ce-BTC@MIL-125 catalyst for photocatalytic CO2 reduction reaction and its application in the field of photocatalytic technology.

[0017] The "core-shell" structure Ce-BTC@MIL-125 catalyst for photocatalytic CO2 reduction reaction obtained by the present invention not only retains the morphology of two single MOFs, but also increases the utilization rate of visible light through the constructed heterojunction structure, and realizes the efficient separation of photogenerated electron-hole pairs. At the same time, the catalyst has excellent stability and large specific surface area.

[0018] The preparation method provided by the invention is simple and has high yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the X-ray powder diffraction pattern of Ce-BTC@NH2-MIL-125 obtained in Example 1.

[0020] Figure 2 This is a scanning electron microscope image of Ce-BTC@NH2-MIL-125 obtained in Example 1.

[0021] Figure 3 This is the catalytic activity diagram of Ce-BTC, NH2-MIL-125 and Ce-BTC@NH2-MIL-125 obtained in Example 1 towards carbon dioxide under light conditions. DETAILED DESCRIPTION

[0022] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0023] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0024] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0025] Example 1

[0026] Preparation of Ce-BTC@NH2-MIL-125:

[0027] (1) Weigh 5 mmol of cerium nitrate hexahydrate and 10 mmol of trimesic acid and dissolve them in a mixed solution of 50 mL of N,N-dimethylformamide and 10 mL of water, stir for 15 minutes, transfer to a polytetrafluoroethylene-lined autoclave, and crystallize at 100° C. for 24 hours. The obtained solid product is filtered, washed three times with methanol, and vacuum dried to obtain Ce-BTC.

[0028] (2) 100 mg Ce-BTC and 100 mg polyvinyl pyrrolidone were dispersed in a mixed solution of 9 mL N,N-dimethylformamide and 1 mL methanol and soaked for 1 hour; 0.15 mL tetrabutyl titanate and 0.77 mmol 2-aminoterephthalic acid were added and stirred for 30 minutes. The mixed solution was transferred to a polytetrafluoroethylene-lined autoclave and crystallized at 150 ° C for 24 hours. The solid product was filtered, washed and dried to obtain Ce-BTC@NH2-MIL-125.

[0029] The X-ray powder diffraction pattern of Ce-BTC@NH2-MIL-125 obtained in Example 1 is shown in Figure 1 .

[0030] The scanning electron microscope image of Ce-BTC@NH2-MIL-125 obtained in Example 1 is shown in Figure 2 .

[0031] Weigh 1 mg of catalyst, 1 mL of water, 3 mL of triethylamine, and 5 mL of acetonitrile. Use a 300 W xenon lamp as the light source for the photocatalytic experiment. Fill with high-purity (999.99%) carbon dioxide gas, flush it ten times, and use it as the reaction gas. The reaction pressure is 0.2 MPa, and then irradiate with light (the light radiation intensity is 150 mW / cm 2 ), samples were taken at 1, 2, 3, 4, 5 and 6 hours respectively, and the results were analyzed by gas chromatography.

[0032] The catalysts used were Ce-BTC obtained in Example 1, Ce-BTC@NH2-MIL-125, and NH2-MIL-125 nanoparticles prepared from tetrabutyl titanate and 2-aminoterephthalic acid solution with the same concentration as in Example 1. The products at different times were analyzed using an Agilent gas chromatograph, and the percentage of CO gas in the total gas was substituted into PV=nRT (where V represents the total volume of the reactor used, which is 0.12 m 3 ) The CO production results are shown in Figure 3 ,from Figure 3 It can be seen that CO is the only carbon-containing product, and the Ce-BTC@NH2-MIL-125 catalyst has the highest CO yield, with a total CO yield of 0.323 mmol / g within 6 hours and a CO product selectivity of more than 99%.

[0033] From the above, it can be concluded that the photocatalytic performance of the prepared "core-shell" structured Ce-BTC@NH2-MIL-125 catalyst is greatly improved compared with the two monomer MOFs. This is due to the fact that the constructed heterostructure increases the utilization of visible light and the efficient separation of photogenerated electron-hole pairs, which provides certain ideas for the development of catalysts for photocatalytic carbon dioxide reduction.

[0034] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A "core-shell" structure Ce-BTC@MIL-125 catalyst for photocatalytic CO2 reduction reaction, characterized in that: The catalyst has a core of Ce-BTC and an in-situ grown MIL-125 nanoparticle shell around the Ce-BTC; the catalyst has a "core-shell" structure, in which the Ce-BTC core is surrounded by the MIL-125 nanoparticle shell in an orderly manner.

2. The method for preparing a "core-shell" structure Ce-BTC@MIL-125 catalyst for photocatalytic CO2 reduction reaction according to claim 1, characterized in that: The following steps are involved: (1) Preparation of Ce-BTC; (2) Ce-BTC and polyvinyl pyrrolidone are dispersed in a mixed solution of N,N-dimethylformamide and methanol and immersed; metal salts and ligands for forming MIL-125 are added and stirred. After the crystallization reaction is completed, a Ce-BTC@MIL-125 catalyst with a "core-shell" structure is obtained; The molar ratio of Ce-BTC to polyvinyl pyrrolidone is 10:1 to 1:10; the volume ratio of N,N-dimethylformamide to methanol is 5:1 to 10:1; the soaking time is 0.5 to 2 hours; the metal salt is a titanium salt; the ligand is one of unsubstituted terephthalic acid or terephthalic acid substituted with a substituent, and the substituent is selected from any one of amino, carboxyl, hydroxyl or halogen; the molar ratio of the metal salt to the ligand is 5:1 to 1:5; the stirring time is 15-60 minutes; the reaction temperature is 120-160°C; and the reaction time is 15-30 hours.

3. The preparation method according to claim 2, characterized in that: The preparation steps of Ce-BTC in step (1) include: The cerium salt and the ligand are dissolved in a mixed solution of N,N-dimethylformamide and water, stirred, and Ce-BTC is obtained after the crystallization reaction is completed; The cerium salt is cerium nitrate hexahydrate, the ligand is trimesic acid; the volume ratio of N,N-dimethylformamide to water is 1:1-8:1; the reaction temperature is 80-120°C; and the reaction time is 12-36 hours.

4. Application of the "core-shell" structure Ce-BTC@MIL-125 catalyst for photocatalytic CO2 reduction reaction as described in claim 1 in the production of CO by photocatalytic CO2 reduction.

5. The use according to claim 4, characterized in that: The catalyst is dispersed in a mixed solution of water, acetonitrile and triethylamine, CO2 is introduced, and the reaction is carried out under the irradiation of a xenon lamp.

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