Co / Ni co-doped high-nuclear-number titanium-oxygen cluster compound as well as preparation method and application thereof

Abstract

The invention discloses a Co / Ni co-doped high-nuclear-number titanium-oxygen cluster compound as well as a preparation method and application thereof, and relates to the field of materials and photocatalytic materials. The molecular formula of the Co / Ni co-doped high-nuclear-number titanium oxygen cluster compound is Ti < 14 > M2O21 (OH2) Bz18 (BzH) (Nfm) 2, and the molecular formula of the Co / Ni co-doped high-nuclear-number titanium oxygen cluster compound is Ti < 14 > CoNi; wherein M represents a co-doped metal center of Co and Ni, Bz is a benzoic acid ligand, and Nfm is an N-formylmorpholine molecule. According to the Co / Ni co-doped high-nuclear-number titanium oxygen cluster compound prepared by the preparation method disclosed by the invention, due to co-doping of Co and Ni, the high-nuclear-number titanium oxygen cluster compound has relatively high catalytic performance and selectivity and has excellent stability; when the photocatalyst is used for preparing CO through photocatalysis of CO2, the selectivity of the product CO is greater than 89%, and no by-product (such as CH4 and HCOOH) is generated.

Description

Technical Field

[0001] This invention relates to the fields of materials and photocatalytic materials, specifically to a Co / Ni co-doped high-nucleus titanium oxide cluster compound, its preparation method, and its application. Background Technology

[0002] Photocatalytic CO2 reduction technology has attracted widespread attention in recent years. This technology utilizes solar energy to drive the conversion of CO2 into high-value-added chemicals (such as CO and CH4), offering advantages such as being environmentally friendly and energy-efficient. However, existing technologies still face many challenges: traditional semiconductor catalysts (such as TiO2) can only respond to ultraviolet light and have high carrier recombination rates; molecular catalysts, while possessing well-defined active sites, are typically expensive and have poor stability; and metal cluster catalysts suffer from complex synthesis and sintering issues. In particular, the extremely high chemical stability of CO2 molecules (C=O bond energy reaches 750 kJ / mol) and the presence of the competitive hydrogen evolution reaction (HER) severely limit catalytic efficiency and selectivity.

[0003] Titanium-oxo clusters (TOCs) are a class of polynuclear metal-oxygen clusters formed by coordination between titanium and oxygen atoms. They possess well-defined structures and tunable compositions, exhibiting unique advantages in photocatalysis. These materials are based on well-defined Ti-O-Ti units and can form structures ranging from Ti3 to Ti... 18 Even higher core count architectures (such as the classic Ti) 16 O 16 cubane structure), its electronic structure has the following characteristics: (1) Ti 4+ 3D 0 (1) Electronic configuration imparts charge transfer properties in the ultraviolet region (such as LMCT transition of Ti-O bond); (2) Abundant μ2-O and μ3-O coordination sites on the surface can activate CO2 molecules; (3) HOMO-LUMO energy levels can be precisely controlled by ligand modification or metal doping.

[0004] In recent years, high-nucleus titanium oxide clusters (≥12 nuclei) have attracted attention due to their three-dimensional extended Ti-O network, such as Ti... 18 O 27 The clusters exhibit a rare "titanium-oxygen cage" structure, with a specific surface area three times larger than that of traditional Ti6O6 clusters, and expose more five-coordinate titanium active sites. However, these materials still suffer from problems such as rapid photogenerated electron-hole recombination and excessive adsorption of key intermediates. Summary of the Invention

[0005] In view of the above prior art defects, the purpose of the present application is to provide a Co / Ni co-doped high nuclear number titanium oxide cluster compound, a preparation method and application, which can effectively solve the problems of traditional titanium oxide cluster catalyst active site structure ambiguity, unclear structure, poor selectivity, complex preparation process and the like in the prior art.

[0006] In order to achieve the above-mentioned or other purposes, the present application is realized by the following technical solutions.

[0007] A Co / Ni co-doped high nuclear number titanium oxide cluster compound, the molecular formula of the Co / Ni co-doped high nuclear number titanium oxide cluster compound is Ti 14 M2O 21 (OH2)Bz 18 (BzH)(Nfm)2, abbreviated as Ti 14 CoNi; wherein M represents a Co and Ni co-doped metal center, Bz is a benzoic acid ligand, and Nfm is an N-formyl morpholine molecule.

[0008] The crystal system of the crystal state of the Co / Ni co-doped high nuclear number titanium oxide cluster compound is triclinic, the space group is P-1, the unit cell parameter a is b is c is α is 98.82°, β is 100.74°, γ is 101.84°, and the unit cell volume is

[0009] The size of the Co / Ni co-doped high nuclear number titanium oxide cluster compound of the present application is 1.9-2.4 nm.

[0010] The present application also provides a method for preparing the above-mentioned Co / Ni co-doped high nuclear number titanium oxide cluster compound, comprising the following steps:

[0011] 1) benzoic acid, cobalt acetate tetrahydrate, nickel acetate tetrahydrate are added to a solvent, stirred and mixed uniformly to obtain a suspension;

[0012] 2) tetraisopropyl titanate is added to the suspension obtained in step 1), stirred and mixed uniformly, then morpholine and formic acid are sequentially added, and stirring is continued until the reaction system is uniform; the reaction system is transferred to a reaction bottle for reaction, after the reaction is completed, it is cooled to room temperature, and finally the target product Co / Ni co-doped high nuclear number titanium oxide cluster compound is obtained after filtration, washing and vacuum drying.

[0013] Further, the molar ratio of titanium acid tetraisopropyl ester, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, benzoic acid, morpholine, and formic acid is (3-4):(0.4-0.6):(0.4-0.6):(9-12):(1.0-1.5):(4-6). In the preparation method of the present application, morpholine is added to effectively control the hydrolysis-condensation rate of the titanium source through coordination of nitrogen atoms; and the addition of formic acid provides a proton environment to promote the dissociation and subsequent integration of metal ions in cobalt / nickel acetate.

[0014] Further, the solvent is selected from one of methanol, tetrahydrofuran, acetonitrile, and dimethylformamide, or the solvent is a mixed solution of acetonitrile and dimethylformamide. Preferably, the solvent is a mixed solution of acetonitrile and dimethylformamide, and the volume ratio of acetonitrile to dimethylformamide is 1:1. More preferably, the solvent is acetonitrile, and the polarity of acetonitrile can effectively promote the dissolution and dispersion of the precursor.

[0015] Further, the molar ratio of the solvent to titanium acid tetraisopropyl ester is (70-80):(3-4).

[0016] Further, the reaction temperature in step 2) is 90-100°C, and the reaction time is 3-5 days.

[0017] Preferably, acetonitrile is used for washing after the reaction is completed. Preferably, the vacuum drying temperature is 20-60°C, and the drying time is 10-24 hours.

[0018] The third aspect of the present application also provides the application of the Co / Ni co-doped high-nuclear titanium oxide cluster compound in the photocatalytic CO2 reduction reaction.

[0019] A method for preparing CO by photocatalytic CO2 reduction reaction, which uses a Co / Ni co-doped high-nuclear titanium oxide cluster compound as a catalyst to selectively reduce CO2 to CO under visible light irradiation.

[0020] Specifically, the method comprises the following steps: dispersing the catalyst Co / Ni co-doped high-nuclear titanium oxide cluster compound in a mixed solvent of acetonitrile and ultrapure water, adding a cocatalyst and a sacrificial agent, performing a photocatalytic reaction in a carbon dioxide atmosphere, and recovering the catalyst Ti 14 CoNi after washing with acetonitrile and vacuum drying, and recycling.

[0021] Further, the molar ratio of the Co / Ni co-doped high-nuclear titanium oxide cluster compound to the cocatalyst is (0.001-0.002):(4-8).

[0022] Further, the cocatalyst is selected from tris(2,2'-bipyridine)ruthenium(II) dichloride ([Ru(bpy)3]Cl 2· 6H2O).

[0023] Further, the sacrificial agent is selected from triethanolamine or triethylamine.

[0024] Further, the molar ratio of the Co / Ni co-doped high nuclear number titanium oxide cluster compound to the sacrificial agent is (0.001-0.002):(7-8).

[0025] Further, the volume ratio of acetonitrile, the sacrificial agent and ultrapure water is (3-4):(1-1.2):(0.1-0.4).

[0026] Further, the conditions of the photocatalytic reaction are as follows: the light source is visible light with λ≥400 nm, the light intensity is controlled at 134±5 mW / cm 2 , the reaction time is 0-2 h, and the reaction system temperature is maintained at 20-25℃.

[0027] In summary, the Co / Ni bimetallic co-doping into the titanium oxide cluster compound is innovatively selected, and by introducing the Co / Ni bimetallic co-doping, from the perspective of electronic structure regulation, the introduction of Co 2+ (3d 7 ) and Ni 2+ (3d 8 ) forms a unique d 7 -d 8 electron synergistic effect, and this combination has more significant electronic regulation ability than single metal doping (such as Fe 3+ or Cu 2+ ): the Co site provides electron donor properties through its unfilled d orbital, while the Ni site exhibits moderate electron accepting ability, and the synergistic effect of the two can precisely adjust the d band center position of the titanium oxide cluster. In addition, in terms of photo-physical processes, the Co / Ni co-doping produces a unique metal-to-cluster charge transfer (MCCT) effect, which is different from the traditional metal-to-ligand charge transfer (MLCT), and MCCT significantly expands the visible light response range. More importantly, compared with the reported single metal doping system, the Co / Ni co-doping in the application forms a more abundant heterometallic core active interface on the Ti-O skeleton.

[0028] The core of the Co / Ni co-doped high nuclear number titanium oxide cluster compound prepared in the application is formed by 14 six-coordinated Ti 4+ ions connected by bridge oxygen atoms to form a double cone structure with a σ symmetry surface. Two heterometallic ions (Co 2+ and Ni 2+ ) are respectively located at the two end vertex positions of the Ti 14 O 21 core and are connected to the titanium oxide core through μ3-O bridges, and each is surrounded by three benzoate (Bz) ligands and adjacent Ti 4+The bridging fixation forms a stable [M(mu3-O)(Bz)3Ti] structural unit. 14 This unique coordination mode in CoNi indicates that the molecule is essentially built up by Ti 14 O 21 metal-oxygen clusters selectively capture Co 2+ and Ni 2+ ions to form a complex structure. X-ray single-crystal diffraction analysis further reveals that neutral solvent molecules N-formylmorpholine (Nfm) form weak coordination interactions (bond order 0.264) with the heterometallic ions via the aldehyde oxygen and ether oxygen, which weak interactions expose the Ti 14 CoNi molecules to assemble into one-dimensional chain-like supramolecular structures. It is worth noting that: (1) Nfm coordination only exists during the crystal packing process and can spontaneously dissociate in solution; (2) the weak coordination bond characteristics (bond order < 0.3) ensure sufficient exposure of the active sites during the catalytic process; (3) the one-dimensional chain-like arrangement forms regular mesoporous channels, providing an ideal channel for reactant diffusion. This precisely designed molecular structure provides an ideal active site arrangement and mass transfer path for achieving efficient photocatalytic CO2 reduction.

[0029] The preparation method disclosed in the present application uses a solvothermal synthesis method. After the raw materials are mixed, the reaction is carried out by heating in a solvent, so that the Co / Ni co-doped high-nuclear-number titanium oxygen cluster compound can be obtained. The preparation method is simple, the raw materials are easy to obtain, and the industrial production is easy. In the reaction process, no template agent or surfactant is needed, the raw material cost is low, the post-treatment is simple, the pollution is small, and the green environmental protection requirement is met.

[0030] The Co / Ni co-doped high-nuclear-number titanium oxygen cluster compound prepared in the present application has high catalytic performance and selectivity due to the co-doping of Co and Ni. When it is used for photocatalytic CO2 preparation CO, the selectivity of the product CO is greater than 89%, and no by-products (such as CH4 and HCOOH) are generated. Isotope labeling experiment 13 CO2→ 13 CO) confirms that the product is derived from CO2 reduction, and excludes the interference of system carbon pollution. Moreover, when the Co / Ni co-doped high-nuclear-number titanium oxygen cluster compound is used as a catalyst for photocatalytic CO2 preparation CO reaction, after 5 cycles of experiments, the CO yield is stably maintained at 5880 μmol·g -1 , which proves that the catalyst Ti 14 CoNi has excellent stability. After participating in 5 cycles of experiments and being recovered, the XRD and IR of the catalyst Ti 14 CoNi show that the crystal structure has no obvious change, which is better than similar catalysts. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1Co / Ni co-doped high-nuclear titanium oxo-cluster Ti 14 Crystal photos of CoNi (The crystal photos were taken by microscope, and the size was marked in the photo).

[0032] Figure 2 Co / Ni co-doped high-nuclear titanium oxo-cluster Ti 14 Crystal structure of single crystal of CoNi.

[0033] Figure 3 Co / Ni co-doped high-nuclear titanium oxo-cluster Ti 14 XRD spectrum of CoNi.

[0034] Figure 4 Co / Ni co-doped high-nuclear titanium oxo-cluster Ti 14 UV-vis DRS spectrum of CoNi.

[0035] Figure 5 Co / Ni co-doped high-nuclear titanium oxo-cluster Ti 14 Isotope labeling experiment results of CoNi in photocatalytic CO2 reduction reaction.

[0036] Figure 6 Co / Ni co-doped high-nuclear titanium oxo-cluster Ti 14 Comparison of CO and H2 yield of CoNi in photocatalytic CO2 reduction reaction for 5 times.

[0037] Figure 7 Co / Ni co-doped high-nuclear titanium oxo-cluster Ti 14 CoNi, catalyst Ti involved in 5 times of photocatalytic selective reduction reaction 14 Comparison chart of infrared spectrum of CoNi.

[0038] Figure 8 Co / Ni co-doped high-nuclear titanium oxo-cluster Ti 14 CoNi, catalyst Ti involved in 5 times of photocatalytic selective reduction reaction 14 Comparison chart of XRD spectrum of CoNi.

[0039] Figure 9 Comparison of yield of CO and H2 and CO selectivity of products of CoNi, catalyst Ti involved in 5 times of photocatalytic selective reduction reaction after 2h of photocatalytic CO2 reduction reaction.

[0040] Figure 10Comparative Example 6 to Comparative Example 10 DETAILED DESCRIPTION

[0041] The present application is described in greater detail by way of specific examples. Other advantages and permutations of the present application will become apparent to those skilled in the art upon reading the following specification and figures. The embodiments disclosed herein are for purposes of example and are not intended to limit the scope of the application. The various features of the application can be used individually or in any combination depending on the needs of the application, as will be apparent to those skilled in the art. The use of the terms "preferably", "more preferably", "most preferably" and the like are used to describe a particularly desirable feature, embodiment or example, but should not be read as limiting the scope of the application. The description herein of any advantages and shortcomings is not to be construed as indicating that certain embodiments are or are not encompassed by the application.

[0042] It should be noted that the terms "upper", "lower", "left", "right", "intermediate", "one", and the like as used herein are only intended to ease the description and are not intended to limit the scope of the application. Changes or adjustments in the relative positions of these terms, without substantial changes in the technical content, are also considered as the scope of the application.

[0043] The technical solutions of the present application are described in detail below through several specific examples and comparative examples. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by conventional methods in the art. Unless otherwise specified, the detection methods used in the examples of the present application are conventional detection methods in the industry.

[0044] Example 1

[0045] Co / Ni-doped high-nuclear titanium oxo-cluster Ti 14 The preparation method of CoNi is as follows:

[0046] Benzoic acid (1.46 g, 12 mmol), Co(CH3COO)3·4H2O (0.012 g, 0.5 mmol) and Ni(CH3COO)3·4H2O (0.012 g, 0.5 mmol) were added to a 20 mL vial, 4 mL of acetonitrile was added and stirred uniformly. Then tetraisopropyl titanate (0.92 mL, 3 mmol) was added, followed by the addition of morpholine (100 μL) and 10 drops of formic acid. After stirring for 2 h, the vial was sealed and heated in an oven at 100 °C for 3 days. After the reaction was completed, it was filtered, washed with acetonitrile, and dried at 60 °C under vacuum for 2 h to obtain dark red block-shaped crystals of Ti 14 CoNi, yield 52.7%.

[0047] The obtained block crystal was photographed by microscope, and the obtained photograph is shown in Figure 2. Figure 1 As can be seen from the photograph, the obtained crystal is a block crystal, and the cluster core size is 1.9-2.4 nm.

[0048] The block crystal was taken for X-ray single crystal diffraction test, and the result is shown in Figure 3. Figure 2 As can be seen from the photograph, the obtained product is Ti 14 CoNi of the application, and from the figure, it can be seen that Ti 14 The core of Ti 14 Co2 is composed of titanium atoms and oxygen atoms through Ti-O-Ti bridging bonds, forming a three-dimensional Ti 14 O 21 Core two ends, respectively, show different coordination environment, wherein Co is coordinated with four oxygen atoms and two morpholine (C4H9NO) molecules, forming a six-coordinated octahedral geometry. Ni is coordinated with five oxygen atoms and one water molecule, also showing a six-coordinated octahedral geometry. In the crystal growth process, the morpholine solvent molecule plays a key role, which alternately connects the clusters as a bridge to form a one-dimensional chain-like stacking structure. The neutral solvent molecule N-formyl morpholine (Nfm) forms a weak coordination (bond order 0.264) with the heterometallic ion through its aldehyde oxygen and ether oxygen.

[0049] After the block crystal was taken and fully ground, X-ray powder diffraction detection was performed, and the result is shown in Figure 4. Figure 3 As can be seen from the figure, the XRD spectrum of Ti 14 CoNi prepared in Example 1 of the application is highly consistent with the main diffraction peak position in the range of 2θ = 5-50°, indicating that the target cluster structure is successfully obtained.

[0050] The block crystal prepared by drying was ground and mixed with spectroscopically pure barium sulfate at a ratio of 1:50-1:200, and the powder was filled into a sample cell. After preheating, the wavelength of the ultraviolet-visible spectrophotometer was set to 200-800 nm, and the barium sulfate reference was calibrated. The sample absorbance was scanned, and the characteristic peak was analyzed after background subtraction. The result is shown in Figure 5. Figure 4 As can be seen from the figure, the absorption band edge of Ti 14 CoNi cluster reaches 550 nm, indicating that the cluster can efficiently respond to visible light. The co-doping of Co / Ni effectively broadens the light response range, making it exhibit excellent capture ability in the ultraviolet-visible light region.

[0051] Example 2

[0052] The difference between this example and Example 1 is that the molar ratio of tetraisopropyl titanate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, benzoic acid, morpholine, and formic acid is 3:0.4:0.4:9:1.0:4, the solvent is acetonitrile, the reaction temperature is 95°C, the reaction time is 5 days, the vacuum drying temperature is 20°C, and the drying time is 24 h.

[0053] Example 3

[0054] The difference between this example and Example 1 is that the molar ratio of tetraisopropyl titanate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, benzoic acid, morpholine, and formic acid is 3:0.6:0.6:10:1.5:5, the solvent is acetonitrile, the reaction temperature is 90°C, the reaction time is 4 days, the vacuum drying temperature is 20°C, and the drying time is 10 h.

[0055] Example 4

[0056] The difference between this example and Example 1 is that the molar ratio of tetraisopropyl titanate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, benzoic acid, morpholine, and formic acid is 4:0.6:0.6:12:1.5:6, the solvent is acetonitrile, the reaction temperature is 90°C, the reaction time is 4 days, the vacuum drying temperature is 20°C, and the drying time is 10 h.

[0057] Example 5

[0058] The difference between this example and Example 1 is that the molar ratio of tetraisopropyl titanate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, benzoic acid, morpholine, and formic acid is 4:0.4:0.4:9:1.0:4, the solvent is acetonitrile, the reaction temperature is 95°C, the reaction time is 4 days, the vacuum drying temperature is 20°C, and the drying time is 10 h.

[0059] Example 6

[0060] Take 5 mg of Co / Ni co-doped high-nuclear titanium oxide cluster prepared in Example 1 as catalyst, in order to improve the dispersion, load it uniformly on the surface of CNTs, add 5 mg (6.7 mmol) [Ru (bpy) 3]Cl2·6H2O, 3 mL of acetonitrile (solvent), 1 mL (7.5 mmol) of triethanolamine (sacrificial agent) and 100 μL of H2O (proton source) into the reaction container, stir until completely dissolved and uniformly mixed. After sealing the reaction system, high-purity CO2 gas is filled (10 min to replace air). A 300 W xenon lamp (equipped with a 400 nm cutoff filter) is used as a light source to vertically irradiate the reaction solution. The reaction container is placed in a constant temperature water bath to control the temperature at 25°C to avoid local overheating affecting the reaction kinetics. At 0.5 h, 1.0 h, 1.5 h and 2 h, respectively, use airtight syringes to take samples, and use gas chromatography (GC) to quantitatively analyze gaseous products (such as CO, H2) and liquid products (such as HCOOH). Gas chromatography analysis: use a gas chromatograph (model, FuLi 9700) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID) to quantitatively analyze the gaseous products after the reaction. Draw a standard curve by injecting a known amount of CO and H2 standard gas for quantitative analysis. The yield of CO is obtained by calculating the ratio of the total amount of CO generated to the mass of the catalyst used. The selectivity of CO is calculated by the formula S CO = nCO / (nCO + nH2) x 100%, where nCO and nH2 are the amounts of CO and H2 measured by GC, respectively.

[0061] Application Example 2

[0062] The experimental conditions in Application Example 2 are the same as in Application Example 1, except that: 13 CO2 is used as the carbon source for the isotopic labeling experiment. After the reaction is completed, the gaseous products are quantitatively analyzed by gas chromatography-mass spectrometry, and compared with the gas chromatography-mass spectrometry of the reaction product CO2 in Application Example 1, as shown in Figure 5 The figure shows that the peak at m / z = 29 indicates that the production 13 CO indeed comes from CO2, rather than the decomposition of other organic matter in the photocatalytic reaction.

[0063] Application Example 3

[0064] The reaction is carried out according to the reaction conditions in Application Example 1. During the reaction, samples of the reaction system are taken every 0.5 hour and detected by gas chromatography. After 2 hours of reaction, Ti 14 CoNi is recovered, and the recovered Ti 14CoNi was put into the same reaction again after being washed and dried, and the reaction conditions were the same as above. The reaction process continued, and samples were taken every 0.5 hour for gas chromatography detection. After 2 hours of reaction, Ti 14 CoNi was recovered, and so on. The recovered catalyst Ti 14 CoNi was repeatedly put into the above-mentioned photocatalytic reaction for 5 times. The yields of CO and H2 obtained by gas chromatography of the reaction liquid of the five reactions were as follows: Figure 6 As can be seen from the figure, after 5 cycles, the catalytic activity of Ti 14 CoNi did not decrease significantly, which indicated that the catalyst had high durability.

[0065] The filtrate after the last reaction was taken and analyzed by ICP-OES to explore the stability of the catalyst. The results are shown in Table 1. It can be seen that Ti, Co and Ni elements were not detected in the filtrate. This indicates that the catalyst framework remains intact during the reaction process, and the active metal species does not leach out.

[0066] Table 1. ICP-OES element analysis of Ti 14 CoNi after 5 reactions

[0067]

[0068] 1 ND: not detected (below the detection limit of the instrument).

[0069] The Ti 14 CoNi recovered after 5 cycles of experiments 14 CoNi were successively subjected to FT-IR and PXRD detection. The obtained FT-IR spectrum is shown in Figure 7 The obtained PXRD spectrum is shown in Figure 8 As can be seen from the figure, after 5 cycles of reactions, the Ti 14 CoNi and Ti 14 CoNi did not change significantly in XRD and structure, which further proved that Ti 14 CoNi had high stability in the photocatalytic process.

[0070] Comparative Example 1

[0071] The reaction conditions were the same as in Application Example 1, except that the catalyst used in this example was Ti 14 Co2 compound, which was uniformly loaded on the surface of CNTs.

[0072] By changing the addition of metal salt, a Co-doped high-nuclear titanium oxygen cluster Ti14 Co2, the procedure is as follows:

[0073] Benzoic acid (1.46 g, 12 mmol), cobalt acetate tetrahydrate (0.024 g, 1.0 mmol) and acetonitrile (4 mL) were added into a 20 mL vial in sequence and stirred at room temperature until a homogeneous suspension was formed. Then, tetraisopropyl titanate (0.92 mL, 3 mmol) was slowly added into the mixture, followed by the addition of morpholine (100 μL) and formic acid (about 10 drops). After the reaction system was continuously stirred at room temperature for 2 h, the vial was sealed and placed in an oven at 100 °C for 3 days. After the reaction was completed, the mixture was cooled to room temperature, and the solid product was collected by filtration, washed thoroughly with acetonitrile, and dried under vacuum at 60 °C for 24 h, finally obtaining pink block crystals of Ti 14 Co2, with a yield of 62.78%.

[0074] Comparative Example 2

[0075] The reaction conditions were consistent with those of Application Example 1, except that the catalyst used in this example was Ti 14 Ni2compound, which was uniformly loaded onto the surface of CNTs.

[0076] By changing the addition of metal salt, a Ni-doped high-nuclear titanium oxide cluster Ti 14 Ni2, the procedure is as follows:

[0077] Benzoic acid (1.46 g, 12 mmol), nickel acetate tetrahydrate (0.024 g, 1.0 mmol) and acetonitrile (4 mL) were added into a 20 mL vial in sequence and stirred at room temperature until a homogeneous suspension was formed. Then, tetraisopropyl titanate (0.92 mL, 3 mmol) was slowly added into the mixture, followed by the addition of morpholine (100 μL) and formic acid (about 5 drops). After the reaction system was continuously stirred at room temperature for 2 h, the vial was sealed and placed in an oven at 100 °C for 4 days. After the reaction was completed, the mixture was cooled to room temperature, and the solid product was collected by filtration, washed thoroughly with acetonitrile, and dried under vacuum at 60 °C for 10 h, finally obtaining green block crystals of Ti 14 Ni2, with a yield of 60.18%.

[0078] Comparative Example 3

[0079] The reaction conditions were consistent with those of Application Example 1, except that in this example, the Co / Ni co-doped titanium oxide cluster was directly added into the reaction as a catalyst, without being loaded onto the surface of CNTs.

[0080] Comparative Example 4

[0081] The reaction conditions were consistent with those of Comparative Example 1, except that in this example, Ti14 Co2compound is directly added into the reaction as catalyst, without being loaded on the surface of CNTs.

[0082] Comparative Example 5

[0083] The reaction conditions are consistent with those of Comparative Example 2, except that in this example, Ti 14 Ni2compound is directly added into the reaction as catalyst, without being loaded on the surface of CNTs.

[0084] Comparative Example 6

[0085] The reaction conditions are consistent with those of Application Example 1, except that in this example, CNTs are directly added into the reaction system for reaction, without any catalyst on the surface.

[0086] Comparative Example 7

[0087] The reaction conditions are consistent with those of Application Example 1, except that in this example, [Ru(bpy)3]Cl2·6H2O is not added.

[0088] Comparative Example 8

[0089] The reaction conditions are consistent with those of Application Example 1, except that in this example, the reaction is carried out under nitrogen atmosphere.

[0090] Comparative Example 9

[0091] The reaction conditions are consistent with those of Application Example 1, except that in this example, triethanolamine (sacrificial agent) is not added.

[0092] Comparative Example 10

[0093] The reaction conditions are consistent with those of Application Example 1, except that in this example, the reaction is carried out in dark condition without light.

[0094] Performance test

[0095] 1. 1 mL samples reacted for 2 h in Application Example 1 and Comparative Examples 1 to 6 were quantitatively analyzed for CO production by gas chromatography (Ar carrier gas, column temperature 80℃) equipped with a TCD detector, and the results are shown in Table 1. Figure 9 Figure 9 In Table 1, from left to right correspond to Application Example 1 (Ti 14 CoNi@CNT), Comparative Example 1 (Ti 14 Co2@CNT), Comparative Example 2 (Ti 14 Ni2@CNT), Comparative Example 3 (Ti 14 CoNi), Comparative Example 4 (Ti 14 Co2), Comparative Example 5 (Ti 14 ​The amounts of CO and H2 and the CO selectivity of the system after 2 hours of reaction with Ni2 and Comparative Example 6 (CNT) are detected. The figure shows that the Co / Ni bimetallic co-doped catalyst Ti prepared in Example 1... 14 CoNi@CNT exhibits optimal CO2 reduction performance, with a CO yield as high as 5.8 mmol·g. -1 The CO selectivity was significantly higher than other comparative catalysts, while effectively suppressing the hydrogen evolution reaction (HER), achieving 87%. In contrast, the single-metal catalyst (Ti) 14 Co2@CNT and Ti 14 The CO yield and selectivity of Ni2@CNT were significantly reduced, indicating a synergistic effect between Co and Ni sites, which jointly optimized the adsorption behavior of the reaction intermediate. The unsupported catalyst (Ti) 14 The generally low activity of CNTs (such as CoNi) highlights the crucial role of CNT supports in improving the dispersion of active sites and promoting charge transport. The negligible activity of pure CNTs confirms that the reaction is driven by titanium oxide clusters as active centers.

[0096] 2. Samples from Application Example 1, Comparative Example 6 to Comparative Example 10, reacted for 2 hours, were subjected to gas chromatography analysis. The results are as follows: Figure 10 As shown in the figure, no gaseous products were detected under conditions of no catalyst, no sacrificial agent, and darkness. Only trace amounts of CO were detected under conditions without the photosensitizer [Ru(bpy)3]Cl2·6H2O, indicating the crucial role of the photosensitizer. Furthermore, no CO was detected when N2 was used instead of CO2, proving that CO2 is the carbon source.

[0097] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A Co / Ni co-doped high nuclearity titanium oxo-cluster compound, characterized in that, The Co / Ni co-doped high nuclear number titanium oxo-cluster compound has a molecular formula of Ti 14 M2O 21 (OH2)Bz 18 (BzH)(Nfm)2, which is briefly denoted as Ti 14 CoNi; wherein M represents a co-doped metal center of Co and Ni, Bz is a benzoic acid ligand, and Nfm is an N-formyl morpholine molecule. 2.The Co / Ni co-doped high nuclear number titanium oxo-cluster compound of claim 1, wherein, The crystal system of the crystal state of the Co / Ni co-doped high-nuclear titanium oxide cluster compound is triclinic, the space group is P-1, the cell parameter a is b is c is α is 98.82°, β is 100.74°, γ is 101.84°, and the cell volume is 3. Process for the preparation of the Co / Ni co-doped high nuclearity titanium oxo clusters of claim 1 or 2, characterized in that, The method comprises the following steps: 1) benzoic acid, cobalt acetate tetrahydrate, nickel acetate tetrahydrate are added into a solvent, and stirred and mixed uniformly to obtain a suspension; 2) tetraisopropyl titanate is added into the suspension obtained in step 1), and stirred and mixed uniformly, then morpholine and formic acid are sequentially added, and stirring is continued until the reaction system is uniform; the reaction system is transferred into a reaction bottle for reaction, after the reaction is completed, cooling is performed to room temperature, and finally the target product Co / Ni co-doped high nuclear number titanium oxide cluster compound is obtained through filtration, washing and vacuum drying.

4. The method of claim 3, wherein, One or more of the following technical features are included: The molar ratio of tetraisopropyl titanate, cobalt acetate tetrahydrate, nickel acetate tetrahydrate, benzoic acid, morpholine and formic acid is (3-4) : (0.4-0.6) : (0.4-0.6) : (9-12) : (1.0-1.5) : (4-6); The solvent is selected from one of methanol, tetrahydrofuran, acetonitrile and dimethylformamide, or the solvent is a mixed solution of acetonitrile and dimethylformamide; The reaction temperature in step 2) is 90-100 DEG C, and the reaction time is 3-5 days.

5. The method of claim 3, wherein, The molar ratio of the solvent to tetraisopropyl titanate is (70-80) : (3-4).

6. The Co / Ni co-doped high nuclear number titanium oxide cluster compound of any one of claims 1-2, or the Co / Ni co-doped high nuclear number titanium oxide cluster compound prepared by the method of any one of claims 3-5, is applied in a photocatalytic CO2 reduction reaction.

7. A method for producing CO by photocatalytic CO2 reduction reaction, characterized by, The Co / Ni co-doped high nuclear titanium oxide cluster compound of claim 1 or 2, or the Co / Ni co-doped high nuclear titanium oxide cluster compound prepared by the method of any one of claims 3-5 is used as a catalyst to selectively reduce CO2 to CO under visible light irradiation.

8. The method of claim 7, wherein, The application relates to a method for preparing a catalyst Co / Ni co-doped high-nuclear titanium oxide cluster compound, which comprises the following steps: dispersing the catalyst Co / Ni co-doped high-nuclear titanium oxide cluster compound in a mixed solvent of acetonitrile and ultrapure water, adding a cocatalyst and a sacrificial agent, and performing a photocatalytic reaction under a carbon dioxide atmosphere; and after the reaction, the catalyst Ti 14 CoNi, which is washed by acetonitrile, vacuum dried and then recycled.

9. The method of claim 8, wherein, One or more of the following technical features are included: The molar ratio of the Co / Ni co-doped high nuclear number titanium oxide cluster compound to the cocatalyst is (0.001-0.002) : (4-8); The cocatalyst is selected from tris(2,2'-bipyridine)ruthenium(II) dichloride; The sacrificial agent is selected from triethanolamine or triethylamine.

10. The method of claim 8, wherein, The conditions of the photocatalytic reaction are as follows: the light source is visible light with λ≥400 nm, the light intensity is controlled at 134±5 mW / cm 2 , the reaction time is 0-2 h, and the reaction system temperature is maintained at 20-25°C.

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