Dissimilar metal nano-cluster for reducing CO2 into CO through photocatalysis, preparation method of dissimilar metal nano-cluster and method for reducing CO2 into CO through photocatalysis

Abstract

The invention belongs to the technical field of material science, and particularly relates to a dissimilar metal nano-cluster for reducing CO2 into CO through photocatalysis, a preparation method of the dissimilar metal nano-cluster and a method for reducing CO2 into CO through photocatalysis. Transition metal nickel salt and rare earth metal europium salt are mixed and dissolved in an organic solvent containing ligand thiadiazole; and adjusting the proportion of a deprotonation reagent triethylamine to obtain the high-purity and high-yield nano-cluster green blocky crystal. The nano-cluster contains 24 nickel ions and 10 europium ions which are bridged through thiadiazole ligands and solvent molecules, so that the nano-cluster has better thermal stability and corrosion resistance; a plurality of europium ions coordinated with water molecules exist in the molecular structure of the nano-cluster provided by the invention and can be used as a catalytic activity center, and the europium ions and nickel ions have a synergistic effect; the nano-cluster can efficiently photocatalyze CO2 to be reduced into CO, the selectivity reaches 100%, and the catalyzed nano-cluster can still keep good structural stability.

Description

Technical Field

[0001] The present invention belongs to the field of material science and technology, and particularly relates to a heterometallic nanocluster for photocatalytic reduction of CO2 to CO, a preparation method thereof, and a method for photocatalytic reduction of CO2 to CO. Background Art

[0002] The extensive use of fossil fuels has led to a sharp increase in atmospheric CO2 concentrations, triggering environmental crises such as global warming and ocean acidification. Therefore, the development of efficient CO2 capture and conversion technologies is urgently needed. Photocatalytic CO2 reduction is considered a key technology for CO2 reduction due to its direct use of solar energy to drive the reaction and the production of clean products (such as CO, CH4, and CH3OH). However, from a catalyst perspective alone, photocatalytic CO2 reduction faces numerous challenges, such as intense competition from side reactions (such as the hydrogen evolution reaction (HER), insufficient yield of the target product, and insufficient catalyst stability. Therefore, the development of catalysts with high activity, selectivity, and stability is crucial to overcoming this technological bottleneck.

[0003] Currently, the most studied photocatalytic materials include semiconductor materials (such as TiO2 and CdS), noble metal-based materials (such as Pt and Au), and single metal complexes (such as Ru and Ir). However, the performance of these materials is limited by defects such as a single active site, a limited photoresponse range, and untunable electronic structure.

[0004] Compared to the aforementioned materials, transition metal-rare earth metal cluster materials have the advantages of abundant raw materials and low prices, and the catalytic performance of the materials can be improved through multi-metal synergy. However, there are currently only four pure transition metal-rare earth metal clusters used for the photocatalytic reduction of CO2 to CO. The difficulty lies in the different affinities of transition metal and rare earth ions for coordination ions, making atomic-level structural control difficult. Secondly, the lack of in situ characterization methods for intermetallic electron transfer pathways and intermediate adsorption configurations has led to insufficient mechanistic understanding. In addition, the complex solution environment during the photocatalytic process makes it difficult to maintain the structure of such cluster materials stable, affecting catalytic performance. These factors have severely restricted the application of transition metal-rare earth metal clusters in the field of photocatalysis. Therefore, the development of structurally stable and highly catalytically active transition metal-rare earth metal nanoclusters remains a difficult problem that needs to be solved. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a heterometallic nanocluster for photocatalytic reduction of CO2 to CO, a preparation method thereof, and a method for photocatalytic reduction of CO2 to CO.

[0006] The present invention is specifically implemented through the following technical solutions.

[0007] The present invention provides a heterometallic nanocluster for photocatalytic reduction of CO2 to CO, the molecular formula of which is [Ni 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O; where mmt is a deprotonated thiadiazole ligand, [NO3] - is the nitrate ion, [CH3COO] - is the acetate ion, [CH3O] - is a deprotonated methanol molecule, [OH] - Deprotonated water molecules.

[0008] The heterometallic nanocluster is a spherical structure with closed tips. Within each heterometallic nanocluster molecule, two europium ions are located at the two closed tips of the spherical structure. The two europium ions at the tips contain methanol molecules, which, after removal, form active sites. The remaining eight europium ions are located between the two europium ions. Twenty-four nickel ions are distributed around the ten europium ions, and the 24 nickel ions and the ten europium ions are bridged by 16 thiadiazole ligands. A single heterometallic nanocluster molecule measures 2.0 nanometers by 2.2 nanometers.

[0009] The present invention provides a method for preparing the heterometallic nanoclusters for photocatalytic reduction of CO2 to CO, comprising the following steps: A mixed solution of europium nitrate, nickel acetate and thiadiazole ligand is prepared, wherein the solvent in the mixed solution contains methanol.

[0010] Deprotonated base and potassium bromide are added to the mixed solution, and then a solvent thermal reaction is carried out, and the heterometallic nanocluster crystal material is obtained through programmed cooling.

[0011] Preferably, the deprotonating base is triethylamine. The molar ratio of europium nitrate, nickel acetate, thiadiazole, potassium bromide and triethylamine is 1:1-3:0.5-1:0.5-1:1.5-3.

[0012] Preferably, the solvent thermal reaction temperature is 100-160 degrees Celsius, the reaction time is 24-72 hours, and the programmed cooling rate is 3-5 degrees Celsius per hour.

[0013] Preferably, the solvent in the mixed solution is a mixture of methanol and other solvents, wherein the other solvents are one or more of ethanol, acetonitrile and water. More preferably, the solvent is a mixed solvent of methanol and acetonitrile in a volume ratio of 1:1.

[0014] Specifically, the preparation of the mixed solution includes the following steps: dissolving europium nitrate in a first solvent to obtain a first solution; dispersing nickel acetate and a thiadiazole ligand in a second solvent to obtain a second solution; mixing the first solution and the second solution to obtain a mixed solution; one of the first solvent and the second solvent is methanol, and the other solvent is one or more of a mixture of ethanol, acetonitrile and water.

[0015] The present invention also provides a method for photocatalytic reduction of CO2 to CO, comprising the following steps: The above-mentioned heterometallic nanoclusters are used as photocatalysts, and the photocatalyst, ruthenium pyridine and sacrificial agent are dissolved in a mixed solvent. Under the illumination of a visible light source, a photocatalytic reaction is carried out to reduce CO2 to CO, and the catalytic product does not contain hydrogen. After the reaction is completed, the photocatalyst is recovered and recycled.

[0016] Preferably, the mass ratio of the photocatalyst, ruthenium pyridine, and sacrificial agent is 1-2:3-6:4-10; the photocatalytic reaction time is 3-5 hours; and the mixed solvent is a mixture of acetonitrile and water in a volume ratio of 2-6:1-4. More preferably, the mass ratio of the photocatalyst, ruthenium pyridine, and sacrificial agent is 1:5:9; the catalytic reaction time is 3-5 hours; and the mixed solvent is a mixture of acetonitrile and water in a volume ratio of 20:9.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a heterometallic nanocluster for photocatalytic reduction of CO2 to CO, the molecular formula of which is Ni 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O; where mmt is a deprotonated thiadiazole ligand, [NO3] - is the nitrate ion, [CH3COO] - is the acetate ion, [CH3O] - is a deprotonated methanol molecule, [OH] - The heterometallic nanoclusters are structurally stable and can efficiently catalyze the reduction of CO2 to CO under light conditions.

[0018] The heterometallic nanocluster of the present invention is a spherical structure with a closed top. Each heterometallic nanocluster molecule contains 24 nickel ions and 10 europium ions. Two europium ions are located at the two closed tops of the spherical structure. The two europium ions at the top contain solvent methanol molecules. After the methanol molecules are removed, they form active sites. The remaining eight europium ions are located between the two europium ions. The 24 nickel ions are distributed around the 10 europium ions. The 24 nickel ions and the 10 europium ions are bridged by 16 thiadiazole ligands. The individual molecules are approximately 2.0 nanometers by 2.2 nanometers in size and have good thermal stability and corrosion resistance. They can exist stably at 300 degrees Celsius. The transition metal and rare earth metal are bridged by the thiadiazole ligands. The rare earth ions at the top of the molecules have multiple easily removable solvent molecules, thus serving as active sites for adsorbing and stabilizing CO2. Photocatalytic experiments show that there is a synergistic effect between europium ions and nickel ions, which jointly promote the conversion of CO2 into CO under photocatalytic conditions. The CO generation rate reaches 6545.3 μmol / g / h and the selectivity reaches 100%. As a photocatalyst material, it exhibits excellent catalytic performance and is a good catalytic material.

[0019] The heterometallic nanoclusters for photocatalytic reduction of CO2 to CO provided by the present invention have a simple preparation process, can obtain a pure sample under the conditions of a solvent thermal reaction, are simple to subsequently process, and are easy to enrich. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a molecular structure diagram of the heterometallic nanoclusters in Example 1.

[0021] Figure 2 This is a thermogravimetric curve of the heterometallic nanoclusters in Example 1.

[0022] Figure 3 This is the trend of CO production change with increasing reaction time in the experiment of photocatalytic CO2 reduction to CO by heterometallic nanoclusters in Example 1.

[0023] Figure 4 This is a graph showing the photocatalytic cycle test data of heterometallic nanoclusters in Example 1.

[0024] Figure 5 is the X-ray powder diffraction pattern of the heterometallic nanoclusters in Example 1.

[0025] Figure 6 is the peak position of europium ions in the X-ray photoelectron spectrum of the heterometallic nanoclusters in Example 1.

[0026] Figure 7 It is the peak position of nickel ions in the X-ray photoelectron spectrum of the heterometallic nanoclusters in Example 1.

[0027] Figure 8This is the fluorescence lifetime test data of ruthenium pyridine. DETAILED DESCRIPTION

[0028] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention is further described below with reference to specific examples and accompanying drawings. However, the examples are not intended to limit the present invention. The experimental methods and detection methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0029] The present invention provides a heterometallic nanocluster for photocatalytic reduction of CO2 to CO, the molecular formula of which is: [Ni 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O, wherein mmt is a deprotonated thiadiazole ligand, [NO3] - is the nitrate ion, [CH3COO] - is the acetate ion, [CH3O] - is a deprotonated methanol molecule, [OH] - Deprotonated water molecules.

[0030] The method for preparing the heterometallic nanoclusters for photocatalytic reduction of CO2 to CO comprises the following steps: A mixed solution of europium nitrate, nickel acetate and thiadiazole ligand is prepared, wherein the solvent in the mixed solution contains methanol; a deprotonated base and potassium bromide are added to the mixed solution, and then a solvent thermal reaction is carried out, and a heterometallic nanocluster crystal material is obtained through programmed cooling.

[0031] In a specific embodiment of the present application, the solvent in the mixed solution is a mixture of methanol and other solvents, wherein the other solvent is one or more of ethanol, acetonitrile and water. More preferably, the solvent is a mixture of methanol and acetonitrile in a volume ratio of 1:1.

[0032] In a specific embodiment of the present application, the solvent thermal reaction temperature is 100-160 degrees Celsius, the reaction time is 24-72 hours, and the programmed cooling rate is 3-5 degrees Celsius per hour.

[0033] In a specific embodiment of the present application, the deprotonating base used is triethylamine, and the ligand is thiadiazole.

[0034] The molar ratio of the europium nitrate, nickel acetate, thiadiazole, potassium bromide and triethylamine is 1:1-3:0.5-1:0.5-1:1.5-3.

[0035] Specifically, europium nitrate is dissolved in a first solvent to obtain a first solution; nickel acetate and a thiadiazole ligand are dispersed in a second solvent to obtain a second solution; the first solution and the second solution are mixed to obtain a mixed solution; among the first solvent and the second solvent, one solvent is methanol, and the other solvent is one or more mixtures of ethanol, acetonitrile and water.

[0036] The heterometallic nanoclusters provided by the present invention can be used for the photocatalytic reduction of CO2 to CO. Specifically, when the heterometallic nanoclusters are used as catalysts for the photocatalytic reduction of CO2 to CO, 5 mg to 10 mg of the heterometallic nanoclusters, 15 mg to 30 mg of ruthenium pyridine [Ru(bpy)3]Cl2ˑ6H2O, and 20 mg to 50 mg of a sacrificial agent, BIH, are added to a mixed solvent consisting of 10 mL to 30 mL of acetonitrile and 5 mL to 20 mL of water. The photocatalytic reaction proceeds under visible light illumination, and after completion, the photocatalyst is recovered and recycled.

[0037] The heterometallic nanocluster material can efficiently convert CO2 into CO in a system containing a photosensitizer ruthenium pyridine [Ru(bpy)3]Cl2ˑ6H2O and a sacrificial agent BIH.

[0038] In a specific embodiment of the present application, the heterometallic nanoclusters are used in the photocatalytic reduction of CO2 to CO. The light source used in the catalytic reaction is a 300W xenon lamp, and the catalytic product does not contain hydrogen.

[0039] The transition metal and rare earth metal in the heterometallic nanoclusters of the present invention are bridged by thiadiazole ligands and solvent molecules. The rare earth ions at the top of the molecules have multiple easily removable solvent molecules, thus serving as active sites for adsorbing and stabilizing CO2. Rare earth ions can broaden the light absorption range to the visible and even near-infrared regions, and can also stabilize reaction intermediates through Lewis acidic sites. Transition metals provide flexible redox active sites, and the electron transfer pathway between the two metals can inhibit carrier recombination, further improving catalytic efficiency. Combined with actual photocatalytic testing and research, the heterometallic clusters of the present invention have demonstrated excellent photocatalytic CO2 conversion to CO.

[0040] The present invention will be specifically described below through the following examples.

[0041] Example 1 A heterometallic nanocluster for photocatalytic reduction of CO2 to CO, with the molecular formula [Ni 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34(H2O)6]·10Br·CH3OH·5H2O; where mmt is a deprotonated thiadiazole ligand, [NO3] - is the nitrate ion, [CH3COO] - is the acetate ion, [CH3O] - is a deprotonated methanol molecule, [OH] - Deprotonated water molecules.

[0042] The preparation method thereof comprises the following steps: Weigh 0.3 g (0.65 mmol) of europium nitrate into a beaker and add 5 ml of methanol to completely dissolve the rare earth.

[0043] 0.16 g (0.65 mmol) of nickel acetate and 0.07 g (0.5 mmol) of thiadiazole were dispersed in 5 ml of acetonitrile and completely dissolved.

[0044] The above two solutions were mixed and poured into a 15 ml polytetrafluoroethylene bottle, and 0.06 g (0.5 mmol) potassium bromide and 0.32 ml (2.3 mmol) triethylamine were added. The mixture was reacted under pressure in a temperature-controlled oven at 130 degrees Celsius for 72 hours, and then cooled to room temperature for 36 hours to obtain green transparent block crystals of Ni. 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O, washed three times with acetonitrile, the product yield was 47%, the purity was above 95%, and its crystal structure was obtained by single crystal X-ray diffractometer.

[0045] Figure 1 This is a schematic diagram of the structure of the heterometallic nanocluster from Example 1 (H atoms omitted in the figure), showing the arrangement of 24 nickel ions and 10 europium ions, with eight europium ions located in the center and two at the apex. Sixteen thiadiazole ligands bridge the nickel and europium ions, ultimately forming a spherical structure with a closed top. The rare earth ions at the apex of the molecules have multiple easily removable solvent molecules, making them active sites for adsorbing and stabilizing CO2. The synergistic effect between the two metals gives the highly stable transition metal-rare earth metal nanoclusters excellent photocatalytic properties for the reduction of CO2 to CO.

[0046] Figure 2 This is the thermogravimetric curve of the heterometallic nanocluster in Example 1, the material is abbreviated as Ni 24 Eu 10 It can be seen that in the absence of solvent molecules co-crystallization, the molecular structure does not collapse until 300 degrees Celsius, showing excellent thermal stability.

[0047] The photocatalytic reduction of CO2 to CO using the heterometallic nanoclusters prepared in Example 1 as a catalyst comprises the following steps: 5 mg of heterometallic nanoclusters, 25 mg of ruthenium pyridine [Ru(bpy)3]Cl2ˑ6H2O, and 45 mg of the sacrificial agent BIH were added to a mixed solvent consisting of 20 mL of acetonitrile and 9 mL of water. The reaction was carried out under irradiation with a 300W xenon lamp. After the reaction, the solid was recovered, washed three times with acetonitrile, and dried in air at room temperature to recover the heterometallic nanocluster catalyst.

[0048] Figure 3 In the experiment of photocatalytic CO2 reduction to CO by heterometallic nanoclusters in Example 1, the CO production trend changes with the increase of reaction time. After three hours of reaction, the CO production reaches 98.18 μmol, showing high catalytic activity.

[0049] Figure 4 The photocatalytic cycling test was carried out on the heterometallic nanoclusters of Example 1. The results showed that after five cycles, the material was still able to maintain good catalytic activity and exhibited excellent catalytic stability.

[0050] Figure 5 This is the X-ray powder diffraction pattern of the heterometallic nanoclusters in Example 1. The simulated peaks are consistent with the experimentally measured peaks, indicating that the material has good phase purity. The peaks after catalysis also match those before catalysis, showing good structural stability.

[0051] Figure 6 is the peak position of europium ions in the X-ray photoelectron spectrum of the heterometallic nanoclusters of Example 1, indicating that the valence state of europium ions in the material is +3. Figure 7 It is the peak position of nickel ions in the X-ray photoelectron spectrum, indicating that the valence state of nickel ions in the material is +2.

[0052] Figure 8 The fluorescence lifetime test of ruthenium pyridine was carried out. When BIH and Ni prepared in Example 1 were added, 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O significantly shortened the fluorescence lifetime of ruthenium pyridine, indicating that Ni 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34The (H2O)6]·10Br·CH3OH·5H2O cluster has a significant quenching effect on ruthenium pyridine, and electron transfer occurs.

[0053] By testing and analyzing the rate of photocatalytic generation of CO by the heterometallic nanoclusters in Example 1, after 5 hours of reaction under the above optimal conditions, the generation rate of CO was 6545.3 μmol / g / h, and the selectivity was 100%. The higher value shows a stronger catalytic performance. The rare earth ions and transition metal ions in the molecular structure have a synergistic effect, and the interaction between the two metal ions jointly promotes the improvement of catalytic efficiency. Rare earth ions can broaden the light absorption range to visible light and even the near-infrared region, and can also stabilize the reaction intermediates through Lewis acidic sites; transition metals can provide flexible redox active sites, and the electron transfer path between the two metals can suppress carrier recombination and further improve the catalytic efficiency. In order to prove the synergistic effect between the above-mentioned Ni ions and Eu ions, the present invention also tested the Ni prepared by the composite of Ni ions and Gd ions. 24 Gd 10 The material is prepared by the same method as the Ni prepared in Example 1. 24 Eu 10 The materials are the same, the difference is that the Eu element is replaced by the Gd element, and the Ni 24 Gd 10 The material was used as a catalyst and the same catalytic reaction as above was used for testing. The results showed that its catalytic performance (CO yield of 1633.3 μmol / g / h and selectivity of 62%) was much lower than that of the Ni prepared in Example 1. 24 Eu 10 Similarly, the present invention also tested Co 24 Eu 10 The catalytic performance of Ni prepared in Example 1 was much better than that of Ni prepared in Example 1. 24 Eu 10 This shows that only when Ni ions and Eu ions are present at the same time can there be a synergistic effect to improve the catalytic efficiency.

[0054] Example 2 Weigh 0.34 g (1 mmol) of europium nitrate into a beaker and add 5 ml of acetonitrile to completely dissolve the rare earth.

[0055] 0.16 g (0.65 mmol) of nickel acetate and 0.07 g (0.5 mmol) of thiadiazole were dispersed in 5 ml of methanol and completely dissolved.

[0056] The above two solutions were mixed and poured into a 15 ml polytetrafluoroethylene bottle, and 0.06 g (0.5 mmol) potassium bromide and 0.32 ml (2.3 mmol) triethylamine were added. The mixture was reacted under pressure in a temperature-controlled oven at 130 degrees Celsius for 72 hours, and then cooled to room temperature for 36 hours to obtain green transparent block crystals. The molecular structure of the crystals was determined to be [Ni 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O. Washed three times with acetonitrile. The product yield was 44%.

[0057] Example 3 Weigh 0.3 g (0.65 mmol) of europium nitrate into a beaker and add 5 ml of acetonitrile to completely dissolve the rare earth.

[0058] 0.25 g (1 mmol) of nickel acetate and 0.07 g (0.5 mmol) of thiadiazole were dispersed in 5 ml of methanol and completely dissolved.

[0059] The above two solutions were mixed and poured into a 15 ml polytetrafluoroethylene bottle, and 0.06 g (0.5 mmol) potassium bromide and 0.32 ml (2.3 mmol) triethylamine were added. The mixture was reacted under pressure in a temperature-controlled oven at 130 degrees Celsius for 72 hours, and then cooled to room temperature for 36 hours to obtain green transparent block crystals. The molecular structure of the crystals was determined to be Ni by single crystal X-ray diffractometry. 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O. Washed three times with acetonitrile. The product yield was 38%.

[0060] Example 4 Weigh 0.3 g (0.65 mmol) of europium nitrate into a beaker and add 5 ml of acetonitrile to completely dissolve the rare earth.

[0061] 0.25 g (1 mmol) of nickel acetate and 0.07 g (0.5 mmol) of thiadiazole were dispersed in 5 ml of methanol and completely dissolved.

[0062] The above two solutions were mixed and poured into a 15 ml polytetrafluoroethylene bottle, and 0.06 g (0.5 mmol) potassium bromide and 0.32 ml (2.3 mmol) triethylamine were added. The mixture was reacted under pressure in a temperature-controlled oven at 150 degrees Celsius for 36 hours, and then cooled to room temperature for 24 hours to obtain green transparent block crystals. The molecular structure of the crystals was determined to be Ni by single crystal X-ray diffractometry. 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O. Washed three times with acetonitrile. The product yield was 35%.

[0063] Example 5 Weigh 0.3 g (0.65 mmol) of europium nitrate into a beaker and add 5 ml of acetonitrile to completely dissolve the rare earth.

[0064] 0.25 g (1 mmol) of nickel acetate and 0.07 g (0.5 mmol) of thiadiazole were dispersed in 5 ml of methanol and completely dissolved.

[0065] The above two solutions were mixed and poured into a 15 ml polytetrafluoroethylene bottle, and 0.06 g (0.5 mmol) potassium bromide and 0.32 ml (2.3 mmol) triethylamine were added. The mixture was reacted under pressure in a temperature-controlled oven at 150 degrees Celsius for 72 hours, and then cooled to room temperature for 36 hours to obtain green transparent block crystals. The molecular structure of the crystals was determined to be Ni by single crystal X-ray diffractometry. 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O. Washed with acetonitrile three times, the product yield was 21%.

[0066] Example 6 Weigh 0.3 g (0.65 mmol) of europium nitrate into a beaker and add 5 ml of acetonitrile to completely dissolve the rare earth.

[0067] Take 0.25 g (1 mmol) of nickel acetate and 0.14 g (1 mmol) of thiadiazole and disperse them in 5 ml of methanol and dissolve them completely.

[0068] The above two solutions were mixed and poured into a 15 ml polytetrafluoroethylene bottle, and 0.06 g (0.5 mmol) potassium bromide and 0.32 ml (2.3 mmol) triethylamine were added. The mixture was reacted under pressure in a temperature-controlled oven at 130 degrees Celsius for 72 hours, and then cooled to room temperature for 36 hours to obtain green transparent block crystals. The molecular structure of the crystals was determined to be Ni by single crystal X-ray diffractometry. 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O. Washed three times with acetonitrile. The product yield was 38%.

[0069] Example 7 Weigh 0.3 g (0.65 mmol) of europium nitrate into a beaker and add 5 ml of water to completely dissolve the rare earth.

[0070] 0.25 g (1 mmol) of nickel acetate and 0.07 g (0.5 mmol) of thiadiazole were dispersed in 5 ml of methanol and completely dissolved.

[0071] The above two solutions were mixed and poured into a 15 ml polytetrafluoroethylene bottle, and 0.06 g (0.5 mmol) potassium bromide and 0.32 ml (2.3 mmol) triethylamine were added. The mixture was reacted under pressure in a temperature-controlled oven at 130 degrees Celsius for 72 hours, and then cooled to room temperature for 36 hours to obtain green transparent block crystals. The molecular structure of the crystals was determined to be Ni by single crystal X-ray diffractometry. 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O. Washed with acetonitrile three times, the product yield was 9%.

[0072] Example 8 Weigh 0.3 g (0.65 mmol) of europium nitrate into a beaker and add 5 ml of acetonitrile to completely dissolve the rare earth.

[0073] 0.25 g (1 mmol) of nickel acetate and 0.07 g (0.5 mmol) of thiadiazole were dispersed in 5 ml of methanol and completely dissolved.

[0074] The above two solutions were mixed and poured into a 15 ml polytetrafluoroethylene bottle, and 0.06 g (0.5 mmol) potassium bromide and 0.42 ml (3 mmol) triethylamine were added. The mixture was reacted under pressure in a temperature-controlled oven at 130 degrees Celsius for 72 hours, and then cooled to room temperature for 36 hours to obtain green transparent block crystals. The molecular structure of the crystals was determined to be Ni by single crystal X-ray diffractometry.24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O. Washed with acetonitrile three times, the product yield was 40%.

[0075] The present invention discloses a method for preparing heterometallic nanoclusters for photocatalytic reduction of CO2 to CO. Rare earth metal and transition metal sources are reacted via a solvothermal reaction to yield chemically stable, highly stable, and catalytically active transition-rare earth heterometallic nanoclusters. The synthesis method is simple and easy, and the nanoclusters exhibit good stability in organic solvents and high thermal stability, maintaining structural stability at 300 degrees Celsius. After five cyclic catalytic tests, the material's structure remained stable, demonstrating excellent catalytic tolerance and stability.

[0076] The heterometallic nanoclusters of the present invention have the characteristics of unique transition metal-rare earth metal assembly structure, wide light absorption range and multi-active site synergistic catalysis; among them, rare earth metals can stabilize the reaction intermediates through Lewis acid sites, while the electron transfer pathways of transition metals and rare earth metals can inhibit carrier recombination and improve the quantum efficiency of light; organic ligands (such as carboxylic acids, phosphonic acids, and N-heterocycles) can regulate the electron density and spatial configuration of the clusters and optimize the CO2 binding mode.

[0077] The transition metal and rare earth metal in the nanocluster are bridged by ligands, and the rare earth ions at the top of the molecules have multiple easily removable solvent molecules, so they can serve as active sites to adsorb and stabilize CO2. Photocatalytic experiments show that there is a synergistic effect between the two metals. The high-stability transition metal-rare earth metal nanocluster proposed in the present invention exhibits excellent photocatalytic CO2 reduction to CO properties. Within 5 hours, under photocatalytic conditions, they jointly promote the conversion of CO2 to CO. The CO generation rate reaches 6545.3μmol / g / h, and the selectivity reaches 100%. As a photocatalyst material, it exhibits excellent catalytic performance and is a good catalytic material. The heterometallic nanoclusters prepared in Examples 2 to 8 above can also be used for photocatalytic CO2 reduction to CO, and have excellent catalytic performance, which is similar to Example 1 and will not be repeated one by one.

[0078] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications of the present invention fall within the scope of the claims and their equivalents, such changes and modifications are intended to be included.

Claims

1. A heterometallic nanocluster for photocatalytic reduction of CO2 to CO, characterized in that: The molecular formula is [Ni 24 Eu 10 (mmt) 16 (NO3)8(CH3COO)2(CH3O)8(OH) 34 (H2O)6]·10Br·CH3OH·5H2O; wherein mmt is a deprotonated thiadiazole ligand.

2. The heterometallic nanoclusters for photocatalytic reduction of CO2 to CO according to claim 1, characterized in that: The heterometallic nanocluster is a spherical structure with a closed top. In each heterometallic nanocluster molecule, two europium ions are respectively located at the two closed tops of the spherical structure. Solvent methanol molecules exist on the two europium ions at the top to form active sites. The remaining eight europium ions are located between the two europium ions. 24 nickel ions are distributed around the 10 europium ions. The 24 nickel ions and the 10 europium ions are bridged by 16 thiadiazole ligands.

3. The method for preparing heterometallic nanoclusters for photocatalytic reduction of CO2 to CO according to claim 1, characterized in that: The following steps are involved: preparing a mixed solution of europium nitrate, nickel acetate and thiadiazole ligand, wherein the solvent in the mixed solution contains methanol; Triethylamine and potassium bromide are added to the mixed solution, and then a solvent thermal reaction is carried out, and the heterometallic nanocluster crystal material is obtained through programmed cooling.

4. The preparation method according to claim 3, characterized in that The molar ratio of europium nitrate, nickel acetate, thiadiazole, potassium bromide and triethylamine is 1:1~3:0.5~1:0.5~1:1.5~3.

5. The preparation method according to claim 3, characterized in that The solvent thermal reaction temperature is 100-160 degrees Celsius, the reaction time is 24-72 hours, and the programmed cooling rate is 3-5 degrees Celsius per hour.

6. The preparation method according to claim 3, characterized in that The solvent in the mixed solution is a mixture of methanol and other solvents, and the other solvents are one or more of ethanol, acetonitrile and water.

7. The preparation method according to claim 3, characterized in that The preparation of the mixed solution comprises the following steps: Europium nitrate is dissolved in a first solvent to obtain a first solution; nickel acetate and a thiadiazole ligand are dissolved in a second solvent to obtain a second solution; the first solution and the second solution are mixed to obtain a mixed solution; one of the first solvent and the second solvent is methanol, and the other solvent is one or more mixtures of ethanol, acetonitrile and water.

8. The preparation method according to claim 3, characterized in that The solvent in the mixed solution is a mixed solvent of methanol and acetonitrile in a volume ratio of 1:

1.

9. A method for photocatalytic reduction of CO2 to CO, characterized in that: The following steps are involved: The heterometallic nanoclusters described in claim 1 are used as photocatalysts, the photocatalyst, the photosensitizer and the sacrificial agent are dissolved in a mixed solvent, and a photocatalytic reaction is carried out under visible light illumination to reduce CO2 to CO, and the catalytic product does not contain hydrogen. After the reaction is completed, the photocatalyst is recovered and recycled.

10. The method for photocatalytic reduction of CO2 to CO according to claim 9, characterized in that: The mass ratio of the photocatalyst, the photosensitizer and the sacrificial agent is 1-2:3-6:4-10; the photocatalytic reaction time is 3h-5h; and the mixed solvent is a mixture of acetonitrile and water in a volume ratio of 2-6:1-4.

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