Heterometallic doped titanium-oxygen cluster compound, preparation method thereof and application of heterometallic doped titanium-oxygen cluster compound in selective oxidation of photo-assisted electro-catalysis benzyl alcohol

Abstract

The invention discloses a dissimilar metal doped titanium-oxygen cluster compound, a preparation method thereof and application of the dissimilar metal doped titanium-oxygen cluster compound in selective oxidation of photo-assisted electro-catalysis benzyl alcohol. The inner cavity type {Ti16O22} core and four M atoms distributed around the core form a dissimilar metal doped twenty-core titanium oxygen cluster; and the compound is connected with twelve Fcdc ligands. The titanium-oxygen cluster compound is stable in structure; the catalyst has a narrow optical band gap and excellent photo-generated charge separation and transfer capability, can utilize the synergistic effect of light energy and electric energy, can efficiently and highly selectively catalyze selective oxidation of benzyl alcohol under mild conditions, is mild in reaction conditions, is high in atom economy in the whole process, is environment-friendly, and accords with the green chemistry principle. Through hydrothermal reaction preparation, nucleation and growth of a cluster compound with a specific nuclear number can be realized; the hydrothermal reaction conditions are mild, and the operation is simple; according to the preparation method, macro-scale preparation of the dissimilar metal doped titanium-oxygen cluster compound can be achieved, the product yield is high, and the reproducibility is excellent.

Description

Technical Field

[0001] This invention belongs to the field of green catalysis technology of metal-oxygen clusters, specifically relating to a heterometal-doped titanium-oxygen cluster compound, its preparation method, and its application in photo-assisted electrocatalytic selective oxidation of benzyl alcohol. Background Technology

[0002] Benzaldehyde is an important chemical intermediate widely used in the pharmaceutical, fragrance, dye, and cosmetic industries. Traditional methods for preparing benzaldehyde by the oxidation of benzyl alcohol mainly rely on stoichiometric oxidants (such as potassium permanganate and potassium dichromate) or noble metal catalysts (such as Pd, Au, and Pt). These methods suffer from poor atom economy, severe environmental pollution, high catalyst costs, and harsh reaction conditions. Therefore, developing green, efficient, and selective benzaldehyde synthesis routes has significant scientific and industrial value. Among these, photo-assisted electrocatalysis, combining light and electrical energy, has become a highly promising green technology. However, traditional heterogeneous catalysts (such as supported noble metals or metal oxides) often suffer from unclear active site structures, difficulties in elucidating catalytic mechanisms at the molecular level, and the challenge of balancing catalytic efficiency and selectivity.

[0003] In recent years, metal-oxide clusters, especially titanium-oxide clusters, as a molecular-level metal oxide model, have shown great potential in the field of catalysis due to their well-defined structure, tunable composition, and excellent photoelectric properties. While pure titanium-oxide clusters have been extensively studied in photocatalysis, their inherently wide bandgap leads to low utilization efficiency of visible light, and the single titanium active center often faces challenges in selective control during organic oxidation reactions. Heterometallic doping is a powerful means of controlling the electronic structure and surface properties of materials. Introducing a second metal into the titanium-oxide cluster framework can not only form intermetallic electronic interactions, effectively narrowing the bandgap of the titanium-oxide cluster and enhancing its absorption capacity for visible light; it can also establish electron transfer channels within the cluster, promoting the separation of photogenerated charges; importantly, it can introduce new catalytically active sites with specific functions, achieving synergistic catalysis and thus improving activity and selectivity.

[0004] However, due to significant differences in hydrolysis rate and coordination habit between heterometallic ions and titanium ions, they readily undergo separate hydrolysis and precipitation during conventional synthesis, resulting in amorphous mixtures rather than structurally defined heterometallic clusters. Existing synthetic methods are mostly micro-scale, sporadic solvothermal reactions with poor reproducibility and difficulty in achieving gram-level or larger-scale preparations, severely hindering their fundamental research and practical applications. Furthermore, currently reported titanium oxide clusters are mainly used in traditional photocatalytic reactions such as dye degradation and water splitting. Research on their use as well-defined molecular catalysts, especially in the emerging synergistic catalytic system of photo-assisted electrocatalysis—which effectively couples two clean energy sources, light and electricity—for high-value-added organic synthesis remains largely unexplored.

[0005] Therefore, developing a series of novel heterometallic doped titanium oxide clusters that can be prepared in large quantities and exploring their innovative applications in photo-assisted electrocatalytic organic synthesis is not only of great scientific value, but also provides a brand-new technical solution for developing next-generation efficient and green fine chemical synthesis routes. Summary of the Invention

[0006] For the reasons stated above, the first objective of this invention is to provide a heterometallic doped icosahedron titanium oxide cluster compound having an internal cavity {Ti 16 O 22 It has a stable structure consisting of a core, four M atoms distributed around the core, and twelve redox-active Fcdc ligands; it has a narrow optical band gap and excellent photogenerated charge separation capability, making it a high-performance optoelectronic material.

[0007] The second objective of this invention is to provide a method for preparing heterometallic doped icosahedral titanium oxide clusters, which achieves nucleation and growth of clusters with a specific number of nuclei through hydrothermal reaction; and realizes the large-scale preparation of heterometallic doped titanium oxide clusters with high yield and excellent reproducibility.

[0008] The third objective of this invention is to provide an application and method of using icoseno-titanium oxide clusters as catalysts in the selective oxidation of benzyl alcohol via photo-assisted electrocatalysis. This invention creatively utilizes the synergistic effect of light and electrical energy to achieve highly efficient and selective catalytic oxidation of benzyl alcohol under mild conditions (room temperature, normal pressure, neutral medium). The reaction conditions are mild, the entire process is highly atom-economical, environmentally friendly, and conforms to the principles of green chemistry.

[0009] The first objective of this invention can be achieved by adopting the following technical solution:

[0010] A heterometallic doped icosahedron titanium oxide cluster compound, characterized by having the general chemical formula [Ti 16 M4(Fcdc) 12 ( μ 2-O)6( μ 3-O) 12 ( μ [4-O)4(H2O)4]·H2O, where Fcdc is a deprotonated 1,1'-ferrocene dicarboxylic acid ligand; μ 2-O represents the O atom connected in a double bridge; μ 3-O represents the three-bridged O atom; μ 4-O represents four bridged O atoms; M is any one of Mn, Co or Fe.

[0011] Furthermore, the cluster compound is in a cubic crystal system. PCrystallized in space group 213; cell parameters are: a=28.35±0.2Å, b=28.35±0.2Å, c=28.35±0.2Å, α=β=γ=90º.

[0012] The second objective of this invention can be achieved by adopting the following technical solution:

[0013] A method for preparing a heterometallic doped icosahedron titanium oxide cluster includes the following steps:

[0014] Titanium source and M metal salt are reacted with 1,1'-ferrocene dicarboxylic acid ligand in a solvothermal reaction system and under certain conditions to obtain the heterometallic doped icosenonuclear titanium oxide cluster.

[0015] Furthermore, the titanium source is tetrabutyl titanate and / or tetraisopropyl titanate.

[0016] Furthermore, the M metal salt is one or a combination of two or more of the acetate or chloride salts of manganese, cobalt, or iron.

[0017] Furthermore, the molar ratio of titanium to M metal in the titanium source is (1.2-1.8):1.

[0018] Furthermore, in the solvothermal system, the solvent is one or a combination of two or more of isopropanol, N,N-dimethylformamide, or acetonitrile.

[0019] Furthermore, the solvothermal reaction conditions are: a temperature of 80℃-120℃, and a reaction time of 36-168h.

[0020] Furthermore, the total molar amount of Ti and M metals added is 2-2.2 times the molar amount of 1,1'-ferrocene dicarboxylic acid ligand.

[0021] Furthermore, the molar volume ratio of 1,1'-ferrocene dicarboxylic acid ligand to solvent is 1 mmol: (0.8-1.2) mL.

[0022] Furthermore, the reaction is carried out under the influence of a regulator, namely triethylamine.

[0023] Furthermore, the amount of triethylamine added is 0.9-1.6 times the molar amount of the 1,1'-ferrocene dicarboxylic acid ligand.

[0024] Furthermore, the reaction system also contains tetrabutylammonium bromide.

[0025] Furthermore, the amount of tetrabutylammonium bromide added is 1 to 1.5 times the molar amount of 1,1'-ferrocene dicarboxylic acid ligand.

[0026] The third objective of this invention can be achieved by adopting the following technical solution:

[0027] Application of heterometal-doped icosahedron titanium oxide clusters as catalysts in the selective oxidation of benzyl alcohol by photo-assisted electrocatalysis.

[0028] The fourth objective of this invention can be achieved by adopting the following technical solution:

[0029] A photo-assisted electrocatalytic selective oxidation method for benzyl alcohol uses a heterometal-doped titanium oxide cluster as a catalyst to oxidize benzyl alcohol to benzaldehyde in an electrolyte under visible light irradiation and an applied bias voltage.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. The heterometallic doped icosahedron titanium oxide cluster compound of the present invention is composed of an internal cavity {Ti 16 O 22 The nucleus and four M atoms surrounding it constitute a heterometallic doped icosahedron titanium oxide cluster; twelve redox-active Fcdc ligands are also distributed around the nucleus. This titanium oxide cluster compound has a stable structure, a narrow optical band gap, and excellent photogenerated charge separation and transfer capabilities, showing clear application potential in the field of photoelectric conversion, and is a high-performance optoelectronic material.

[0032] 2. The method for preparing heterometallic doped icosahedron titanium oxide clusters of the present invention achieves nucleation and growth of clusters with a specific number of nuclei through hydrothermal reaction. The hydrothermal reaction conditions are mild and the operation is simple; it not only realizes the large-scale preparation of heterometallic doped titanium oxide clusters, but also achieves high product yield and excellent reproducibility.

[0033] 3. The heterometallic doped icosenonuclear titanium oxide cluster compound of the present invention has photoelectric properties and can utilize the synergistic effect of light energy and electrical energy to efficiently and selectively catalyze the selective oxidation of benzyl alcohol under mild conditions (room temperature, normal pressure, neutral medium). The reaction conditions are mild, the whole process is highly atom-economical, environmentally friendly, and in line with the principles of green chemistry. Attached Figure Description

[0034] Figure 1 The cluster compound [Ti] of this invention 16 The molecular ball-and-stick structure diagram of M4; where: blue = Ti atom, blue-green = M (Mn, Co, Fe) atom, yellow = Fe atom in 1,1'-ferrocene dicarboxylic acid, gray = C atom, red = O atom, pink = H2O molecule (Ow).

[0035] Figure 2 For clusters [Ti 16 M4] in {Ti 16 O 22 Schematic diagram of the nuclear structure.

[0036] Figure 3 For clusters [Ti 16 The local coordination environment diagram of the M center in [M4] shows its trigonal bipyramidal geometry; the coordination environment diagram of the ferrocene carboxylic acid ligand and the metal.

[0037] Figure 4 The cluster compound [Ti] prepared in Example 1 16 [Mn4] Large-scale preparation product diagram.

[0038] Figure 5 The cluster compound [Ti] prepared in Example 1 16 Image of Mn4 crystal.

[0039] Figure 6 The cluster compound [Ti] prepared in Example 3 16 Photograph of Co4 crystal.

[0040] Figure 7 The cluster compound [Ti] prepared in Example 5 16 Photograph of Fe4 crystal.

[0041] Figure 8 For clusters [Ti 16 X-ray powder diffraction pattern (PXRD) of Mn4.

[0042] Figure 9 For clusters [Ti 16 X-ray powder diffraction pattern (PXRD) of Co4.

[0043] Figure 10 For clusters [Ti 16 X-ray powder diffraction pattern (PXRD) of Fe4].

[0044] Figure 11 For clusters [Ti 16 Infrared spectrum of M4.

[0045] Figure 12 For clusters [Ti 16 X-ray photoelectron spectroscopy (XPS) spectra of Mn4, where (a) is the total spectrum, (b) is the Ti 2p spectrum, (c) is the Mn 2p spectrum, and (d) is the Fe 2p spectrum.

[0046] Figure 13 For clusters [Ti 16 X-ray photoelectron spectroscopy (XPS) spectra of Co4, where (a) is the total spectrum, (b) is the Ti 2p spectrum, (c) is the Co 2p spectrum, and (d) is the Fe 2p spectrum.

[0047] Figure 14 For clusters [Ti 16X-ray photoelectron spectroscopy (XPS) spectra of Fe4], where (a) is the total spectrum, (b) is the Ti 2p spectrum, (c) is the Fe 2p spectrum, and (d) is the C 1s spectrum.

[0048] Figure 15 For clusters [Ti 16 Solid-state UV-Vis absorption spectrum of M4.

[0049] Figure 16 For clusters [Ti 16 Tauc plot of M4].

[0050] Figure 17 For clusters [Ti 16 [M4] is the photocurrent-time (it) response diagram of the photoelectrode under simulated solar switching cycle.

[0051] Figure 18 For clusters [Ti 16 The conversion rate and yield of benzaldehyde to benzyl alcohol by M4 as the working electrode under photo-assisted electrocatalysis.

[0052] Figure 19 For clusters [Ti 16 A comparison of the conversion rate and yield of benzaldehyde in the oxidation of benzyl alcohol to benzaldehyde under photo-assisted electrocatalysis and electrocatalysis conditions using M4 as the working electrode.

[0053] Figure 20 For clusters [Ti 16 The yield diagram of benzyl alcohol to benzaldehyde was obtained by recycling Mn4] as the working electrode for three reactions.

[0054] Figure 21 For clusters [Ti 16 X-ray powder diffraction patterns before and after three cycles of using Mn4 as the working electrode.

[0055] Figure 22 For clusters [Ti 16 Infrared spectra before and after three cycles of using Mn4] as the working electrode. Detailed Implementation

[0056] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0057] A heterometallic doped icosahedron titanium oxide cluster compound, characterized by having the general chemical formula [Ti16 M4(Fcdc) 12 ( μ 2-O)6( μ 3-O) 12 ( μ [4-O)4(H2O)4]·H2O, where Fcdc is a deprotonated 1,1'-ferrocene dicarboxylic acid ligand; μ 2-O represents the O atom connected in a double bridge; μ 3-O represents the three-bridged O atom; μ 4-O represents four bridged O atoms; M is any one of Mn, Co or Fe.

[0058] The heterometallic-doped icosahedron titanium oxide cluster compound of this application has an internal cavity {Ti 16 O 22 The nucleus is surrounded by four M atoms and twelve Fcdc ligands; four μ The 4-O bridges each connect one M atom, linking the four M atoms to {Ti}. 16 O 22 The cores are connected.

[0059] Each M atom adopts a trigonal bipyramidal geometry (MO5), with three carboxyl oxygen atoms (equatorial plane) from different Fcdc ligands, and one... μ A 4-O atom is coordinated with an axially coordinated water molecule. Each Fcdc ligand is linked to three different titanium atoms and one M atom via a carboxyl oxygen atom; thus, the Fcdc ligand is associated with {Ti}. 16 O 22 The cores are connected; such as Figures 1-3 As shown.

[0060] {Ti 16 O 22 The core is a tetrahedral {Ti} 16 O 22 The unit consists of 16 Ti atoms connected by 22... μ 3 / μ It is composed of 4-O atoms interconnected. Specifically, four trinuclear oxygen-core titanium {Ti3O} subunits serve as the vertices of the tetrahedron, while the other four Ti atoms are located at the center of each face of the tetrahedron, connected by... μ The 3-O atom connects with the Ti atom in the vertex {Ti3O} subunit, together forming the complete {Ti} unit. 16 O 22}Skeleton. Importantly, {Ti 16 O 22 All Ti atoms in the nucleus exhibit a distorted octahedral configuration.

[0061] The {Ti} of this application16 O 22 The nucleus is an aggregate that can accept multiple electrons.

[0062] As one embodiment, the cluster compound is in a cubic crystal system. P Crystallized in space group 213; cell parameters are: a=28.35±0.2Å, b=28.35±0.2Å, c=28.35±0.2Å, α=β=γ=90º.

[0063] This application also provides a method for preparing heterometallic doped icosenonuclear titanium oxide clusters, comprising the following steps: Titanium source and M metal salt are reacted with 1,1'-ferrocene dicarboxylic acid ligand in a solvothermal reaction system and under certain conditions to obtain the heterometallic doped icosenonuclear titanium oxide cluster.

[0064] As one embodiment, the precursor solution preparation step includes: dissolving a titanium source and a metal salt M in an organic solvent in a certain proportion to form a precursor solution A; 1,1'-ferrocene dicarboxylic acid (H2Fcdc) was added to precursor solution A and a solvothermal reaction was carried out.

[0065] As one embodiment, the preparation steps of the precursor solution and ligand solution are included: dissolving the titanium source and the M metal salt in an organic solvent in a certain proportion to form the precursor solution A; 1,1'-ferrocene dicarboxylic acid (H₂Fcdc) is dissolved in an organic solvent to form ligand solution B. Precursor solution A and ligand solution B are mixed and subjected to a solvothermal reaction.

[0066] In one embodiment, the titanium source is tetrabutyl titanate and / or tetraisopropyl titanate; the M metal salt is one or a combination of two or more of the acetates or chlorides of manganese, cobalt, or iron.

[0067] In one implementation, the molar ratio of titanium to M metal in the titanium source is (1.2-1.8):1.

[0068] As one embodiment, the solvent is one or a combination of two or more of isopropanol, N,N-dimethylformamide or acetonitrile.

[0069] As one implementation method, the solvothermal reaction conditions are: a temperature of 80℃-120℃ and a reaction time of 36-168h.

[0070] In one embodiment, the reaction is carried out under a regulator, namely triethylamine; the amount of triethylamine added is 0.9-1.6 times the molar amount of 1,1'-ferrocene dicarboxylic acid ligand.

[0071] In this embodiment, 1,1'-ferrocene dicarboxylic acid (H2Fcdc) and a regulator are dissolved in an organic solvent to form ligand solution B. Alternatively, 1,1'-ferrocene dicarboxylic acid (H2Fcdc) and a regulator are directly added to precursor solution A.

[0072] In one implementation, the total molar amount of Ti and M metals added is 2-2.2 times the molar amount of 1,1'-ferrocene dicarboxylic acid ligand.

[0073] The molar volume ratio of 1,1'-ferrocene dicarboxylic acid ligand to solvent is 1 mmol: (0.8-1.2) mL.

[0074] As one embodiment, the reaction system also contains tetrabutylammonium bromide; the amount of tetrabutylammonium bromide added is 1-1.5 times the molar amount of 1,1'-ferrocene dicarboxylic acid ligand.

[0075] In this embodiment, 1,1'-ferrocene dicarboxylic acid (H2Fcdc) and tetrabutylammonium bromide are dissolved in an organic solvent to form ligand solution B. Alternatively, 1,1'-ferrocene dicarboxylic acid (H2Fcdc) and tetrabutylammonium bromide are directly added to precursor solution A.

[0076] In one embodiment, 1,1'-ferrocene dicarboxylic acid (H2Fcdc) and tetrabutylammonium bromide are dissolved in an organic solvent, and then a regulator is added to form ligand solution B. Alternatively, 1,1'-ferrocene dicarboxylic acid (H2Fcdc) and tetrabutylammonium bromide are directly added to precursor solution A, and then a regulator is added.

[0077] As one embodiment, the reaction also includes a post-processing step: after the reaction is completed, the temperature is lowered to room temperature to precipitate the target cluster crystal; the crystal is collected by filtration, washed with mother liquor and diethyl ether, and dried under vacuum to obtain the heterometallic doped icosahedron titanium oxide cluster.

[0078] This application also provides the application of heterometal-doped icosahedron titanium oxide clusters as catalysts in the selective oxidation of benzyl alcohol by photo-assisted electrocatalysis.

[0079] This application also provides a method for selective oxidation of benzyl alcohol by photo-assisted electrocatalysis, using the aforementioned heterometal-doped titanium oxide cluster as a catalyst, and oxidizing benzyl alcohol to benzaldehyde in an electrolyte under visible light irradiation and an applied bias voltage.

[0080] In one embodiment, the electrode prepared by loading the heterometallic doped titanium oxide cluster compound onto the electrode or by using raw materials containing the heterometallic doped titanium oxide cluster compound is the working electrode, the platinum sheet or graphite rod is the counter electrode, and the Ag / AgCl or saturated calomel electrode is the reference electrode, thus forming a three-electrode system.

[0081] In one embodiment, the electrolyte comprises benzyl alcohol, an electrolyte, and a solvent. The electrolyte is sodium bromide and / or sodium perchlorate; the solvent is a mixture of water and acetonitrile.

[0082] In one implementation, the bias voltage is +0.8V to +1.4V. vs. Ag / AgCl.

[0083] As one implementation method, visible light is provided by a xenon lamp equipped with a 420nm cutoff filter.

[0084] The following is a further explanation using specific embodiments.

[0085] Example 1: Cluster compound [Ti] 16 Large-scale preparation of Mn4]

[0086] 90 mmol of tetrabutyl titanate and 60 mmol of manganese acetate tetrahydrate were dispersed in a mixed solvent of 1200 ml acetonitrile and 300 ml isopropanol, and mixed thoroughly to obtain a mixture. 75 mmol of 1,1'-ferrocene dicarboxylic acid was added to the mixture, and the mixture was stirred for 30 min until homogeneous. Then, 90 mmol of triethylamine was added to the above mixture, and the mixture was stirred for 10 min to ensure thorough mixing and dissolution. The milk bottle was sealed and placed in a 100°C oven for 4 days. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, where a large number of octahedral blocky crystals were observed to precipitate (e.g., Figure 4 The crystals were washed three times with acetonitrile, filtered, and dried in a vacuum oven at 60°C for 12 hours to obtain the final product, with a yield of 78% and a molecular formula of C. 144 H 104 Fe 12 Mn4O 74 Ti 16 H2O; named Ti 16 Mn4; Appearance like Figure 5 As shown.

[0087] Example 2

[0088] In a 3-liter round-bottom flask, 2 L of a 1:4 volume ratio of isopropanol / acetonitrile mixed solvent was added. Then, 120 mmol of tetrabutyl titanate, 80 mmol of manganese acetate tetrahydrate, and 100 mmol of 1,1'-ferrocene dicarboxylic acid were added, and the mixture was stirred for 60 min. Next, 90 mmol of triethylamine was added to the mixture, and the mixture was stirred for 10 min to ensure thorough mixing and dissolution. The reaction flask containing the mixture was heated to 80 °C for 5 days. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, where a large number of microcrystals were observed. The microcrystals were washed three times with a mixed solvent of acetonitrile and isopropanol, filtered, and collected. The microcrystals were then dried in a vacuum drying oven at 60 °C for 12 h to obtain the final product Ti. 16 Mn4, with a yield of 75%.

[0089] Example 3: Cluster compound [Ti] 16 Large-scale preparation of Co4] 90 mmol of tetrabutyl titanate and 60 mmol of cobalt acetate tetrahydrate were dispersed in a mixed solvent of 1200 ml acetonitrile and 300 ml N,N'-dimethylformamide and mixed thoroughly to obtain a mixture. 75 mmol of 1,1'-ferrocene dicarboxylic acid and 90 mmol of tetrabutylammonium bromide were added to the mixture, and the mixture was stirred for 30 min until homogeneous. Then, 90 mmol of triethylamine was added to the above mixture, and the mixture was stirred for 10 min to ensure thorough mixing and dissolution. The mixture was sealed in a milk bottle and placed in a 100°C oven for 4 days. After the reaction, the mixture was allowed to cool naturally to room temperature, and a large number of octahedral blocky crystals were observed to precipitate. The crystals were washed three times with a mixed solvent of acetonitrile and N,N'-dimethylformamide, filtered, and collected. The crystals were then dried in a vacuum drying oven at 60°C for 12 h to obtain the final product. The molecular formula is C2. 144 H 104 Fe 12 Co4O 74 Ti 16 H2O; named Ti 16 Co4; Appearance like Figure 6 As shown.

[0090] Example 4

[0091] In a 3L round-bottom flask, 2L of a mixed solvent of N,N'-dimethylformamide / acetonitrile (volume ratio 1:4) was added. Then, 120 mmol of tetrabutyl titanate, 100 mmol of manganese acetate tetrahydrate, 100 mmol of 1,1'-ferrocene dicarboxylic acid, and 100 mmol of tetrabutylammonium bromide were added, and the mixture was stirred for 60 min. Next, 90 mmol of triethylamine was added to the mixture, and the mixture was stirred for 10 min to ensure thorough mixing and dissolution. The reaction flask containing the mixture was heated to 80°C for 5 days. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, where a large number of microcrystals were observed. The microcrystals were washed three times with a mixed solvent of acetonitrile and N,N'-dimethylformamide, filtered to collect the microcrystals, and dried in a vacuum oven at 60°C for 12 h to obtain the final product Ti. 16 Co4.

[0092] Example 5: Cluster compound [Ti] 16 Large-scale preparation of Fe4] 90 mmol of tetrabutyl titanate and 60 mmol of copper acetate tetrahydrate were dispersed in a mixed solvent of 750 ml acetonitrile and 750 ml N,N'-diethylformamide, and mixed thoroughly to obtain a mixture. 75 mmol of 1,1'-ferrocene dicarboxylic acid and 90 mmol of tetrabutylammonium bromide were added to the mixture, and the mixture was stirred for 30 min until homogeneous. Then, 120 mmol of triethylamine was added to the above mixture, and the mixture was stirred for 10 min to ensure thorough mixing and dissolution. The mixture was sealed in a milk bottle and placed in a 100°C oven for 4 days. After the reaction, the mixture was allowed to cool naturally to room temperature, and a large amount of brown octahedral blocky crystals were observed to precipitate. The crystals were washed three times with a mixed solvent of acetonitrile and N,N'-diethylformamide, filtered, and dried in a vacuum drying oven at 60°C for 12 h to obtain the final product with the molecular formula C. 144 H 104 Fe 16 O 74 Ti 16 H2O; named Ti 16 Fe4; Appearance like Figure 7 As shown.

[0093] Example 6

[0094] In a 3L round-bottom flask, 2L of a 1:1 mixture of N,N'-diethylformamide and acetonitrile was added. Then, 120 mmol of tetrabutyl titanate, 67 mmol of manganese acetate tetrahydrate, 100 mmol of 1,1'-ferrocene dicarboxylic acid, and 150 mmol of tetrabutylammonium bromide were added, and the mixture was stirred for 60 min. Next, 120 mmol of triethylamine was added to the mixture, and the mixture was stirred for 10 min to ensure thorough mixing and dissolution. The reaction flask containing the mixture was heated to 80°C for 5 days. After the reaction, the mixture was allowed to cool naturally to room temperature, where a large number of microcrystals were observed. The microcrystals were washed three times with a mixture of acetonitrile and N,N'-diethylformamide, filtered, and collected. The microcrystals were then dried in a vacuum oven at 60°C for 12 h to obtain the final product, Ti. 16 Fe4.

[0095] Test case

[0096] (1) The cluster compound [Ti] prepared in the example 16 Single-crystal X-ray diffraction (SCXRD) was performed on the cluster [Ti] 16 [M] Crystallographic data and results are shown in Table 1; X-ray powder diffraction tests were performed, and the X-ray powder diffraction results are as follows: Figure 8-10 As shown.

[0097] Table 1: Ti 16 M crystallographic data

[0098]

[0099] a R 1 =Σ||F o | – |F c || / Σ|F o | b wR 2 = |Σw(|F o | 2 – |F c | 2 )| / Σ|w(F o 2 ) 2 | 1 / 2 .

[0100] Single-crystal X-ray diffraction (SCXRD) analysis showed that the heterometallic cluster Ti 16 M4 has the chemical formula [Ti 16 M4(Fcdc) 12 ( μ 2-O)6( μ 3-O) 12 ( μ[4-O)4(H2O)4]·H2O (Fcdc=1,1-ferrocene; M = Mn, Co, Fe), and in cubic space group P Crystallization in 213 (Table 1). The molecular structure consists of an internal hollow titanium-oxygen core {Ti 16 O 22 It consists of four outer M atoms and twelve Fcdc ligands. Figure 1-3 ). {Ti 16 O 22} Through four μ A 4-O bridge and twelve Fcdc ligands are attached to four M atoms. Each M atom exhibits a triangular bipyramidal geometry (MO5), with three O-carboxyl atoms coordinated in the equatorial plane (from the three Fcdc ligands), and μ 4-O atoms and axially positioned water molecules (Ow). The dissociation or substitution of axially coordinated water molecules allows the M atom to become an active center, interacting with foreign species.

[0101] Table 1 shows the data and results, Ti 16 The molecular formula of Mn4 is C 144 H 106 Fe 12 Mn4O 75 Ti 16 Crystallization in the monoclinic system P Space group 213, cell parameters a=b=c=28.35Å, α=β=γ=90º. Ti 16 The molecular formula of Co4 is C 144 H 106 Fe 12 Co4O 75 Ti 16 Crystallization in the monoclinic system P Space group 213, cell parameters a = b = c = 28.2541 Å, α = β = γ = 90º. Ti 16 The molecular formula of Fe4 is C 144 H 106 Fe 16 O 75 Ti 16 Crystallization in the monoclinic system P Space group 213, cell parameters a=b=c=28.465Å, α=β=γ=90º.

[0102] from Figure 8-10 The X-ray powder diffraction test results show that the synthesized Ti 16 The M4 diffraction pattern and the simulated diffraction pattern are highly consistent in peak positions, indicating that the synthesized Ti... 16 M4 has good phase purity, and Ti 16M4 crystals are stable in air and neutral aqueous solutions and exhibit high crystallinity.

[0103] (2) The Ti prepared in the example 16 Fourier transform-infrared spectroscopy was performed on M4, and the infrared spectrum is shown below. Figure 11 As shown.

[0104] from Figure 11 The infrared spectrum clearly shows that at 1031 cm⁻¹ -1 and 2971-2860cm -1 The left and right peaks represent Ti, respectively. 16 Vibrations of Ti-OC and CH in M4. 780-860 cm -1 The peak in this band belongs to the Ti-O vibration in the titanium oxide cluster. The peak is located at ~1481 cm⁻¹ in the infrared spectrum. -1 The bands represent the characteristic bands of the Fcdc components. Meanwhile, ν (COO) at 1540cm -1 and 1621-1656cm -1 The vibrations in the vicinity represent Ti respectively 16 The coordination vibrations of the carboxyl groups in the ligands of M4 are consistent with the molecular structure.

[0105] (3) Ti prepared in the example 16 M4 underwent X-ray photoelectron spectroscopy (XPS) testing, and the XPS plot is shown below. Figure 12-14 As shown.

[0106] like Figure 12-14 As shown, the peaks at binding energies of 458.8 eV and 464.5 eV correspond to the Ti2p of +4 valence Ti, respectively. 2 / 3 and Ti 2p 1 / 2 state; Ti 16 Mn4, Ti 16 Co4 and Ti 16 The Fe 2p spectrum of Fe4 confirms that Fe 2+ The presence of Fe2+ at 721.9 eV and 709.1 eV represents the presence of Fe2+ in divalent iron. 2+ 2p 2 / 3 and Fe 2+ 2p 1 / 2 State; in Ti 16 In the Mn2p spectrum of Mn4, the two peaks with binding energies of 641.2 and 653.0 eV correspond to the Mn 2p3 / 2 and 2p1 / 2 states, respectively, indicating that Mn has a +2 valence. Co 2+ 2p 2 / 3 and Co 2+ 2p 1 / 2The binding energy peaks of the state are located at 781.1 eV and 796.5 eV, indicating that Co has a +2 valence.

[0107] XPS characterization shows that Ti 16 The metallic element in Mn4 is Ti. 4+ Mn 2+ and Fe 2+ The chemical state exists. This means that electron transfer can easily occur during internal oxidation of {Ti}. IV 16 O 22} (acting as an "electronic library") and peripheral restoration M II Between the centers.

[0108] (4) The Ti prepared in the example 16 M4 was used for solid-state ultraviolet absorption spectroscopy (UV-vis) testing. The UV-vis graph is shown below. Figure 15 As shown.

[0109] As can be seen from the UV-vis image, Ti 16 The maximum light absorption range of M4 extends to around 500 nm, with an absorption band extending to approximately 650 nm. This cluster exhibits broad and strong absorption in the 200-800 nm range. Furthermore, the Ti content was further estimated using the Kubelka-Munk function. 16 The optical band gaps (Eg) of M4 are approximately 1.74 (Mn), 1.83 (Co), and 1.70 (Fe) eV, respectively. Figure 16 ).

[0110] (5) The Ti prepared in the example 16 The transient short-circuit photocurrent response of M4 was tested to investigate its photoinduced electron-hole separation efficiency; such as Figure 17 As shown.

[0111] When the Xe lamp is turned on, the photocurrent is generated rapidly and then remains stable without any significant decrease in intensity. When the Xe lamp is turned off, the photocurrent decays rapidly, indicating that Ti... 16 M4 exhibits excellent photocurrent response. It is worth noting that Ti... 16 The short-circuit photocurrent response density of Mn4 clusters is significantly higher than that of Ti. 16 Co4 and Ti 16 Fe4 clusters. This also indicates that Ti 16 Mn4 clusters more effectively suppress photo-excited electron-hole pair recombination, resulting in higher separation efficiency.

[0112] Example of effect

[0113] (1) Photo-assisted electrocatalytic oxidation of benzyl alcohol

[0114] 10 mg of the {Ti} prepared in the example 16 M4} cluster Ti 16 Mn4, Ti 16 Co4 and Ti 16 Fe4+, 10 mg carbon black, and 100 μL Nafion solution were dispersed in 1 mL of a water-ethanol mixture and sonicated to form a uniform catalyst ink. This ink was then drop-coated onto a 1 cm × 2 cm sheet of carbon paper and allowed to air dry at room temperature to create the working electrode.

[0115] In a three-electrode electrolytic cell, the above-described electrodes were used as the working electrodes, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was a mixture of 25 mL of 0.02 M NaBr aqueous solution (pH=6) and acetonitrile (v / v=23:2), containing 0.1 mmol of benzyl alcohol. Argon gas was continuously introduced into the electrolytic cell. Under magnetic stirring, a bias voltage of +1.5 V (vs. Ag / AgCl) was applied, and the working electrode was simultaneously irradiated from the front with a 300 W xenon lamp (AM 1.5 filter). The reaction was carried out at room temperature for 20, 40, 60, 80, and 100 min. After the reaction was completed, the reaction solution was analyzed by gas chromatography; the results are as follows. Figure 18 As shown. Results for the control group without xenon lamp irradiation are as follows. Figure 19 As shown.

[0116] The results show that Ti 16 When Mn4 is used as a catalyst, the photo-assisted electrocatalytic conversion of benzyl alcohol is >99%, the selectivity of benzaldehyde can reach 99%, and the yield can reach 98%. Figure 18 a); and Ti 16 The Co4 catalyst can convert approximately 96.9% of benzyl alcohol within 100 minutes of reaction, while the yield of benzaldehyde can reach approximately 81.5%. Figure 18 b); for Ti 16 The Fe4 catalyst may have slightly lower PEC benzyl alcohol oxidation activity than the Ti catalyst. 16 Mn4 and Ti 16 With Co4 catalyst, only about 87.6% of benzyl alcohol was converted during the PEC reaction after 100 min, while about 65.8% of benzaldehyde was generated. Figure 18 c) Furthermore, at different reaction times, Ti 16 Mn4, Ti 16 Co4 and Ti 16 The yield of benzaldehyde produced by the electrocatalytic oxidation of benzyl alcohol using Fe4 catalyst was significantly lower than that of photo-assisted electrooxidation. Figure 19 ).

[0117] (2) Using benzyl alcohol as the substrate, with Ti 16Taking Mn4 as an example, the electrode after the photo-assisted electrocatalytic oxidation of benzyl alcohol is washed with pure water, and the recovered Ti is used. 16 The Mn4 electrode continues the photo-assisted electrocatalytic reaction as in (1), and the catalyst is recovered again, with Ti... 16 The Mn4 electrode was used for the third cycle. After three cycles, the electrode was recovered and washed with pure water to obtain the recovered Ti. 16 Mn4 catalyst. The yield of benzaldehyde to be produced in a three-stage photo-assisted electrocatalytic reaction is as follows: Figure 20 As shown.

[0118] from Figure 20 It can be seen that Ti 16 In the selective oxidation of benzyl alcohol to benzaldehyde using Mn4 catalyst, the yield of benzaldehyde did not decrease significantly after three cycles.

[0119] X-ray powder diffraction (XPD) was performed on the catalyst after three cycles of reaction; the XPD results are as follows: Figure 21 As shown; infrared testing was performed, and the infrared spectrum is as follows. Figure 22 As shown.

[0120] from Figure 21 and 22 The results show that Ti 16 The PXRD and IR spectra of the Mn4 catalyst before and after the reaction were basically consistent, which confirms that it has good structural integrity.

[0121] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A heterometallic doped titanium oxide cluster compound, characterized in that, Its general chemical formula is [Ti 16 M4(Fcdc) 12 ( μ 2-O)6( μ 3-O) 12 ( μ [4-O)4(H2O)4]·H2O, where Fcdc is a deprotonated 1,1'-ferrocene dicarboxylic acid ligand; μ 2-O represents the O atom connected in a double bridge; μ 3-O represents the three-bridged O atom; μ 4-O represents four bridged O atoms; M is any one of Mn, Co or Fe.

2. The heterometallic doped titanium oxide cluster compound according to claim 1, characterized in that, The clusters are in a cubic crystal system. P Crystallized in space group 213; cell parameters are: a=28.35±0.2Å, b=28.35±0.2Å, c=28.35±0.2Å, α=β=γ=90º.

3. A method for preparing heterometallic doped titanium oxide clusters, characterized in that, Includes the following steps: The titanium source and the M metal salt were reacted with the 1,1'-ferrocene dicarboxylic acid ligand in a solvothermal reaction system and under certain conditions to obtain the heterometallic doped titanium oxide cluster.

4. The method for preparing heterometallic doped titanium oxide clusters according to claim 3, characterized in that, The titanium source is tetrabutyl titanate and / or tetraisopropyl titanate; the M metal salt is one or a combination of two or more of the acetate or chloride salts of manganese, cobalt, or iron. The molar ratio of titanium to M metal in the titanium source is (1.2-1.8):

1.

5. The method for preparing heterometallic doped titanium oxide clusters according to claim 3, characterized in that, In the solvothermal system, the solvent is one or a combination of two or more of isopropanol, N,N-dimethylformamide or acetonitrile; The solvothermal reaction conditions are: a temperature of 80℃-120℃ and a reaction time of 36-168h.

6. The method for preparing heterometallic doped titanium oxide clusters according to claim 3, characterized in that, The total molar amount of Ti and M metals added is 2-2.2 times the molar amount of 1,1'-ferrocene dicarboxylic acid ligand; The molar volume ratio of 1,1'-ferrocene dicarboxylic acid ligand to solvent is 1 mmol: (0.8-1.2) mL.

7. The method for preparing heterometallic doped titanium oxide clusters according to claim 3, characterized in that, The reaction was carried out under the presence of a regulator, namely triethylamine; the amount of triethylamine added was 0.9-1.6 times the molar amount of 1,1'-ferrocene dicarboxylic acid ligand.

8. The method for preparing heterometallic doped titanium oxide clusters according to claim 3, characterized in that, The reaction system also contains tetrabutylammonium bromide; the amount of tetrabutylammonium bromide added is 1-1.5 times the molar amount of 1,1'-ferrocene dicarboxylic acid ligand.

9. The application of the heterometallic doped titanium oxide cluster compound as a catalyst in the photo-assisted electrocatalytic selective oxidation of benzyl alcohol, as described in claim 1 or 2.

10. A method for the selective oxidation of benzyl alcohol by photo-assisted electrocatalysis, characterized in that, Using the heterometallic doped titanium oxide cluster compound as described in claim 1 or 2 as a catalyst, benzyl alcohol is oxidized to benzaldehyde in an electrolyte under visible light irradiation and an applied bias voltage.

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