A UiO-66-NH2 / Pt / UiO-66-NH2 catalyst, its preparation and application

Abstract

A UiO-66-NH2 / Pt / UiO-66-NH2 catalyst, its preparation, and its application belong to the field of photocatalytic reduction of CO2. It has a "sandwich" structure: defective UiO-66-NH2 serves as the active component substrate, with a noble metal interlayer of Pt acting as the photocatalytic active center, and UiO-66-NH2 as the outer layer. Pt nanoparticles act as electron mediators, thereby efficiently improving photocatalytic activity. The close contact between the highly dispersed Pt and UiO-66-NH2 shortens the electron transport distance and promotes interfacial charge transfer. Furthermore, UiO-66-NH2 not only inhibits Pt aggregation and leaching but also provides more active sites for the reaction, enabling the material to exhibit excellent activity and stability in CO2 reduction under visible light.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and relates to a catalyst, its preparation method and application, particularly to a defective UiO-66-NH2 / Pt / UiO-66-NH2 catalyst with a "sandwich" structure, its preparation method and its application in photocatalytic reduction of CO2. Background Technology

[0002] With the rapid development of modern industry, the excessive emission of carbon dioxide (CO2) from the combustion of fossil fuels is a global problem, leading to ecological crises such as global warming and resource shortages, severely restricting sustainable social development. Among various strategies for utilizing solar energy, photocatalytic CO2 reduction is considered a highly promising strategy. It can directly convert renewable solar energy into chemical energy, where solar energy is the driving force for exciting and transferring holes and electrons to induce oxidation and reduction reactions. This allows for the clean and sustainable utilization of solar energy to convert CO2 into useful products. Under sunlight, photocatalysts can induce CO2 reduction and convert it into fuels and chemicals. The preparation of highly efficient photocatalysts is crucial for the development and application of photocatalytic CO2 reduction systems.

[0003] As an emerging porous crystalline material, metal-organic frameworks (MOFs) have become a promising platform for reducing carbon dioxide emissions. MOFs are porous materials formed by coordination bonds between metal ions (or clusters) and multidentate organic ligands. MOFs possess advantages such as finely designed band gaps and catalytically active sites, efficient charge transfer pathways, high porosity, regular channel structures, high dielectric constants, and flexible topologies. Based on these unique properties, the preparation of photocatalysts involving MOFs has attracted widespread attention, and recent studies have demonstrated the enormous potential of MOF materials as photocatalysts for carbon dioxide emission reduction.

[0004] Improving photoinduced electron separation and transfer has become a primary issue in photocatalysis. However, single MOF materials also have some limitations, mainly low conductivity, poor stability, and poor product selectivity. These limitations restrict the wider application of MOFs. Therefore, it is necessary to develop highly efficient composite photocatalysts to achieve efficient charge separation, high stability, broad response spectrum, and high selectivity. Summary of the Invention

[0005] To address the problems of existing technologies, the present invention aims to provide a unique perspective on catalyst preparation. It develops a highly efficient heterogeneous catalyst for photocatalytic CO2 reduction by effectively combining metal-organic frameworks (MOFs) with metal nanoparticles. A photoresponsive defect-type UiO-66-NH2 is selected as the active component substrate, with the noble metal Pt serving as the photocatalytic active center. The close contact between the highly dispersed Pt nanoparticles and UiO-66-NH2 shortens the electron transport distance, promotes interfacial charge transfer, and improves photocatalytic performance. Furthermore, UiO-66-NH2 not only inhibits Pt aggregation and leaching but also provides more active sites for the reaction, enabling the material to exhibit excellent activity and stability in CO2 reduction under visible light.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] One objective of this invention is to provide a method for preparing a composite photocatalyst UiO-66-NH2 / Pt / UiO-66-NH2 for photocatalytic CO2 reaction, the method comprising the following steps:

[0008] (1) Preparation of active component substrate UiO-66-NH2;

[0009] (2) Load Pt nanoparticles onto UiO-66-NH2 to obtain UiO-66-NH2 / Pt: Disperse the UiO-66-NH2 synthesized in step (1) into a solution of noble metal Pt nanoparticles; stir for a period of time and centrifuge to obtain UiO-66-NH2 / Pt;

[0010] (3) Preparation of UiO-66-NH2 / Pt / UiO-66-NH2: Disperse the UiO-66-NH2 / Pt synthesized in step (2) into a solvent, then add metal salt and organic ligand, stir, heat, and centrifuge to obtain sample UiO-66-NH2 / Pt / UiO-66-NH2.

[0011] The preferred step (1) preparation steps of the active component substrate UiO-66-NH2 include: adding metal salt and organic ligand to a solvent, heating, centrifuging, washing, drying, and obtaining a sample.

[0012] The preferred metal salt in step (1) is a metal salt of Ce or / and Zr; preferably, the Ce metal salt is selected from one or more of chlorides or nitrates; the zirconium salt is selected from zirconium acetylacetonate and zirconium chloride octahydrate; the organic ligand is aminoterephthalic acid; the molar ratio of metal salt to ligand is 3:1 to 1:5, for example 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5;

[0013] In preferred step (1), the solvent is a mixture of water and a conditioner, which is environmentally friendly. Preferably, the defect conditioner is selected from acetic acid, ethanol, hydrobromic acid, formic acid, propionic acid, and hydrochloric acid. Preferably, the ratio of the conditioner to water is 1:4 to 4:1; for example, 1:4; 1:3; 1:2; 1:1; 4:1; 3:1; 2:1. The concentration of the dissolved aminoterephthalic acid is 0.0264 to 0.0309 mol·L⁻¹. -1 ;

[0014] The preferred step (1) has a reaction temperature of 80–100°C and a reaction time of 10–14 h.

[0015] The preferred method for preparing the Pt nanoparticle solution in step (2) includes the following steps: dispersing polyvinylpyrrolidone (PVP) and a platinum precursor compound in a solvent containing a reducing agent; heating and refluxing to obtain a Pt nanoparticle solution; preferably, the molecular weight of PVP is selected from 30,000 or 55,000; the platinum precursor compound is selected from sodium chloroplatinate or chloroplatinic acid; the molar ratio of PVP to the platinum precursor compound is 1:3 to 1:5; the solvent is an alcohol or an aqueous alcohol solution; the volume ratio of alcohol to water is preferably 1:1 to 9:1; the alcohol is both a reducing agent and a solvent, preferably selected from methanol, ethanol, n-propanol, butanol, and n-butanol; the concentration of the dispersed Pt nanoparticle solution is 0.005 to 0.01 mol·L⁻¹. -1 Preferably, the heating temperature is 150–180°C, and the reaction time is 2–3 hours.

[0016] Preferably, the loading of Pt in the preparation method of UiO-66-NH2 / Pt in step (2) can be flexibly adjusted as needed; each 0.1 g of UiO-66-NH2 corresponds to the above-mentioned 1-20 mL Pt nanoparticle solution; for example, the volume of the Pt nanoparticle solution is 1 mL, 2 mL, 3 mL, 4 mL, 5 mL, 6 mL, 7 mL, 8 mL, 9 mL, 10 mL, 15 mL, 18 mL, 20 mL, etc.; the stirring time is 0.5-3 h.

[0017] Preferably, the metal salt mentioned in step (3) is a Ce or / and Zr metal salt; preferably, the Ce metal salt is selected from one or more of chlorides or nitrates, and the zirconium salt is selected from one or more of zirconium acetylacetonate and zirconium chloride octahydrate; the organic ligand is aminoterephthalic acid; the molar ratio of metal salt to ligand is 3:1 to 1:5; the mass ratio of metal salt to UiO-66-NH2 / Pt is 3:1 to 5:1; and the concentration of aminoterephthalic acid after dissolution is 0.0264 to 0.0309 mol·L. -1The solvent is a mixed solution of water and a regulator, wherein the regulator is selected from formic acid, acetic acid, and propionic acid; preferably, the volume ratio of water to regulator is 1:4 to 4:1, the reaction temperature is 90 to 120°C, and the reaction time is 20 to 24 hours.

[0018] The second objective of this invention is to provide a composite nanocatalyst UiO-66-NH2 / Pt / UiO-66-NH2, which is prepared by the method described above.

[0019] A third objective of this invention is to provide a use for the UiO-66-NH2 / Pt / UiO-66-NH2 catalyst described above, for the photocatalytic reduction of CO2 to CO. Preferred specific steps: Weigh 1-5 mg of the catalyst, 0.1 mL of water, 0.3 mL of triethylamine, and 1.5 mL of acetonitrile. Then, using visible light or a xenon lamp as the photocatalytic light source and carbon dioxide as the reaction atmosphere, first equilibrate under dark conditions for one hour at a reaction pressure of 0.05-1 MPa, and then proceed with the photocatalytic reaction.

[0020] The beneficial technical effects of the present invention are as follows:

[0021] This invention loads Pt nanoparticles into defective UiO-66-NH2, and then coats it with another layer of UiO-66-NH2. The resulting "sandwich" structure MOF composite material not only retains the original porous structure characteristics of the initial MOFs, exhibiting an octahedral structure, but also facilitates carbon dioxide adsorption. The close contact between the highly dispersed Pt nanoparticles and UiO-66-NH2 shortens the electron transport distance, promotes interfacial charge transfer, and efficiently improves photocatalytic activity. Furthermore, the "sandwich" structure of UiO-66-NH2 not only inhibits Pt aggregation and leaching, improving stability, but also provides more active sites, enabling the material to exhibit excellent activity and stability in CO2 reduction under visible light.

[0022] Meanwhile, this invention also provides a feasibility for developing porous materials with high photocatalytic performance, and achieves high photocatalytic performance by controlling the defect type of MOF.

[0023] The preparation method provided by this invention is simple, uses water as a solvent, is green and environmentally friendly, easy to implement, has a high yield, and is easy to mass-produce. Attached Figure Description

[0024] Figure 1 The X-ray powder diffraction pattern of the composite UiO-66-NH2 / Pt / UiO-66-NH2 obtained in this invention;

[0025] Figure 2 This is a scanning electron microscope image of the composite UiO-66-NH2 / Pt / UiO-66-NH2 obtained in this invention;

[0026] Figure 3 This is a transmission electron microscope (TEM) image of the composite UiO-66-NH2 / Pt / UiO-66-NH2 obtained in this invention.

[0027] Figure 4 This is a graph showing the catalytic activity of the composite UiO-66-NH2 / Pt / UiO-66-NH2 obtained in this invention for carbon dioxide under dark and light conditions. Detailed Implementation

[0028] The technical solution of the present invention will now be further illustrated through specific embodiments. This detailed description should not be considered a limitation of the present invention, but rather a more detailed description of certain aspects, characteristics, and embodiments of the present invention. Those skilled in the art will understand that the following embodiments are merely preferred examples of the present invention to facilitate a better understanding of the invention, and are therefore not intended to limit the invention.

[0029] Example 1

[0030] Preparation of UiO-66-NH2 / Pt / UiO-66-NH2 complex:

[0031] (1) Dissolve aminoterephthalic acid (0.056 g) and zirconium chloride octahydrate (0.224 g) in a mixed solution of 4 mL water and 6 mL acetic acid and react at 90 °C for 12 h. Centrifuge and dry to obtain UiO-66-NH2.

[0032] (2) 133 mg of polyvinylpyrrolidone (PVP) was dissolved in 180 mL of methanol, and then sodium chloroplatinate (0.049 g) was added. The mixture was heated at 170 °C for 3 h to obtain a Pt nanoparticle solution.

[0033] (3) Take 5 mL of the prepared Pt nanoparticle solution and 0.1 g of UiO-66-NH2, stir for 3 h to obtain solution A, and centrifuge and dry to obtain UiO-66-NH2 / Pt;

[0034] (4) Aminoterephthalic acid (0.056 g) and zirconium chloride octahydrate (0.224 g) were dissolved in 4 mL of water and 6 mL of acetic acid to form solution B. After thorough mixing, the UiO-66-NH2 / Pt synthesized in (3) was added and stirred. The mixture was reacted at 90 °C for 12 h. The mixture was then removed, washed, and dried to obtain UiO-66-NH2 / Pt / UiO-66-NH2.

[0035] (5) Weigh 5 mg of catalyst, 0.1 mL of water, 0.3 mL of triethylamine, and 1.5 mL of acetonitrile. Use a 300 W xenon lamp as the light source for the photocatalytic experiment and carbon dioxide as the reaction atmosphere. First, equilibrate in the dark for one hour at a reaction pressure of 0.1 MPa, then irradiate with light. Take samples every hour and analyze the results by gas chromatography. The CO yield at the sixth hour after the reaction was 1156 mmol / g, the yield was 192 mmol / g / h, and the selectivity was 98%.

[0036] Example 2

[0037] Preparation of UiO-66-NH2 / Pt / UiO-66-NH2 complex:

[0038] (1) Dissolve aminoterephthalic acid (0.12 g) and zirconium chloride octahydrate (0.16 g) in a mixed solution of 3 mL water and 2 mL acetic acid and heat at 100 °C for 12 h. Centrifuge and dry to obtain UiO-66-NH2.

[0039] (2) 66 mg of polyvinylpyrrolidone (PVP) was dissolved in a mixture of 80 mL of methanol and 10 mL of water, and then sodium chloroplatinate (0.052 g) was added and heated at 180 °C for 2.5 h to obtain a Pt nanoparticle solution.

[0040] (3) Take 8 mL of the prepared Pt nanoparticle solution and 0.05 g of UiO-66-NH2, stir for 3 h to obtain solution A, and centrifuge and dry to obtain UiO-66-NH2 / Pt;

[0041] (4) Aminoterephthalic acid (0.12 g) and zirconium chloride octahydrate (0.16 g) were dissolved in 3 mL of water and 2 mL of propionic acid to form solution B. The UiO-66-NH2 / Pt synthesized in (3) was added and stirred thoroughly. The mixture was reacted at 100 °C for 12 h. The solution was then removed, washed, and dried to obtain UiO-66-NH2 / Pt / UiO-66-NH2.

[0042] (5) Weigh 5 mg of catalyst, 0.1 mL of water, 0.3 mL of triethylamine, and 1.5 mL of acetonitrile. Use a 300 W xenon lamp as the light source for the photocatalytic experiment and carbon dioxide as the reaction atmosphere. First, equilibrate in the dark for one hour at a reaction pressure of 0.1 MPa, then irradiate with light. Take samples every hour and analyze the results by gas chromatography. The CO yield at the 6th hour after the reaction was 1200 mmol / g, the yield was 200 mmol / g / h, and the selectivity was 99%.

[0043] Example 3

[0044] Preparation of UiO-66-NH2 / Pt / UiO-66-NH2 complex:

[0045] (1) Dissolve aminoterephthalic acid (0.30 g) and zirconium chloride octahydrate (0.58 g) in a mixture of 5 mL water and 5 mL acetic acid and heat at 80 °C for 20 h. Centrifuge and dry to obtain UiO-66-NH2.

[0046] (2) 13.3 mg of polyvinylpyrrolidone (PVP) was dissolved in 18 mL of ethanol, and then 0.0035 g of chloroplatinic acid was added. The reaction was carried out at 150 °C for 3 h to obtain a Pt nanoparticle solution.

[0047] (3) Take 10 mL of the prepared Pt nanoparticle solution and UiO-66-NH2 (0.1 g), stir for 3 h to obtain solution A, and centrifuge and dry to obtain UiO-66-NH2 / Pt;

[0048] (4) Aminoterephthalic acid (0.30 g) and zirconium chloride octahydrate (0.58 g) were dissolved in 5 mL of water and 5 mL of acetic acid. 400 μL of cerium ammonium nitrate aqueous solution and 5 mL of formic acid were added to form solution B. The UiO-66-NH2 / Pt synthesized in (3) was added, and the mixture was stirred thoroughly and reacted at 80 °C for 12 h. The mixture was then removed, washed, and dried. Under a N2 atmosphere, it was calcined at 250 °C for 2.5 h to obtain UiO-66-NH2 / Pt / UiO-66-NH2.

[0049] (5) Weigh 1 mg of catalyst, 0.1 mL of water, 0.3 mL of triethylamine, and 1.5 mL of acetonitrile. Use a 300 W xenon lamp as the light source for the photocatalytic experiment and carbon dioxide as the reaction atmosphere. First, equilibrate in the dark for one hour at a reaction pressure of 0.2 MPa, and then irradiate with light. Take samples every hour and analyze the results by gas chromatography. The CO yield after the sixth hour of reaction was 1085 mmol / g, the yield was 180.83 mmol / g / h, and the selectivity was 99%.

[0050] The above description is merely a preferred embodiment of the present invention, but the present invention should not be limited to the content disclosed in this embodiment. Therefore, any equivalent or modified versions made without departing from the spirit of the present invention fall within the scope of protection of the present invention.

Claims

1. The use of a UiO-66-NH2 / Pt / UiO-66-NH2 catalyst for photocatalytic reduction of CO2 to produce CO; the UiO-66-NH2 / Pt / UiO-66-NH2 catalyst is a "sandwich" structure of a defective UiO-66-NH2 / Pt / UiO-66-NH2 catalyst structure, with defective UiO-66-NH2 as the active component substrate, a noble metal interlayer Pt as the photocatalytic active center, and an outer layer of UiO-66-NH2.

2. Use according to claim 1, characterized in that, The preparation method of the UiO-66-NH2 / Pt / UiO-66-NH2 catalyst comprises the following steps: (1) preparing the active component substrate defective UiO-66-NH2; (2) loading Pt nanoparticles on the UiO-66-NH2 to obtain defective UiO-66-NH2 / Pt: dispersing the defective UiO-66-NH2 synthesized in step (1) into a noble metal Pt nanoparticle solution; stirring for a period of time, and centrifuging to obtain UiO-66-NH2 / Pt; (3) preparation of UiO-66-NH2 / Pt / UiO-66-NH2: dispersing the UiO-66-NH2 / Pt synthesized in step (2) into a solvent, then adding a metal salt and an organic ligand, stirring, heating, and centrifuging to obtain the sample UiO-66-NH2 / Pt / UiO-66-NH2; The preparation steps of the active component substrate defective UiO-66-NH2 in step (1) comprise: adding a metal salt and an organic ligand into a solvent, heating, centrifuging, drying, and obtaining a sample; the metal salt is a metal salt of Ce or / and Zr; the solvent is a mixed solution of water and a regulator, and the volume ratio of the regulator to water is 1:4 to 4:1; the regulator is selected from one of acetic acid, ethanol, hydrobromic acid, formic acid, propionic acid, and hydrochloric acid; the reaction temperature is 80-100°C; the reaction time is 10-14 h; the metal salt of Ce is selected from one or more of chloride or nitrate; the metal salt of Zr is selected from one of zirconium acetylacetonate or zirconium chloride octahydrate; and the organic ligand is amino terephthalic acid; In step (3), the metal salt is a metal salt of Ce or / and Zr; the organic ligand is amino terephthalic acid; the molar ratio of the metal salt of Ce or / and Zr to the ligand is 3:1 to 1:5; the mass ratio of the metal salt of Ce or / and Zr to UiO-66-NH2 / Pt is 3:1 to 5:1; the solvent used is a mixed solution of water and a regulator, and the regulator is selected from formic acid, acetic acid, and propionic acid; the volume ratio of water to the regulator is 1:4 to 4:1; the metal salt of Ce is selected from one or more of chloride or nitrate, and the metal salt of Zr is selected from one or more of zirconium acetylacetonate or zirconium chloride octahydrate; and the organic ligand is amino terephthalic acid.

3. Use according to claim 2, characterized in that, The concentration of the organic ligand in step (3) is 0.0264-0.0309 mol-L -1 .

4. Use according to claim 2, characterized in that, In step (2), the preparation method of the noble metal Pt nanoparticle solution comprises the following steps: dispersing polyvinylpyrrolidone (PVP) and a platinum precursor compound into a solvent containing a reducing agent; heating and refluxing to obtain a Pt noble metal nanoparticle solution. Polyvinylpyrrolidone (PVP) is selected from any one of molecular weight 30000 or 55000; the platinum precursor compound is selected from any one of sodium chloroplatinate, chloroplatinic acid; the molar ratio of PVP to platinum precursor compound is 1:3~1:5; the solvent is alcohol or alcohol aqueous solution; the volume ratio of alcohol to water is 1:1~9:1; the alcohol is selected from methanol, ethanol, n-propanol, butanol, n-butanol; the concentration of the dispersed Pt nanoparticle solution is 0.005~0.01 mol·L -1 ; the heating temperature is 150~180 ℃; the reaction time is 2~3 h.

5. The use according to claim 2, characterized in that, The loading amount of Pt in the preparation method of the UiO-66-NH2 / Pt in step (2) is flexibly adjusted according to requirements; 1-20 ml of the Pt nanoparticle solution is used for every 0.1 gram of UiO-66-NH2; and the reaction time is 0.5-3 hours.

6. The use according to claim 2, characterized in that, The reaction temperature in step (3) is 90-120 DEG C; and the reaction time is 20-24 hours.

7. According to the application of claim 2, 1-5 mg of catalyst, 0.1 mL of water, 0.3 mL of triethylamine and 1.5 mL of acetonitrile are weighed, then visible light or a xenon lamp is used as a light source for photocatalysis, carbon dioxide is used as a reaction atmosphere, the reaction pressure is 0.05-1 MPa, and then the light irradiation reaction is carried out.

Images