Lead-doped titanium-oxygen cluster compound with medium and high nuclear numbers as well as preparation method and application of lead-doped titanium-oxygen cluster compound

Abstract

The invention discloses a lead-doped titanium-oxygen cluster compound with medium and high nuclear numbers as well as a preparation method and application thereof, and belongs to the field of materials, fine chemical engineering and photocatalytic materials. The molecular formula of the lead-doped titanium oxygen cluster compound with the medium and high nuclear numbers is H3Ti16Pb6 (mu4-O) 4 (mu3-O) 12 (mu2-O) 10 (Bz) 18 (OQ) 8 (OAc), mu4-O represents a four-bridged O atom, mu3-O represents a three-bridged O atom, mu2-O represents a two-bridged O atom, Bz represents a benzoic acid ligand, OQ represents an 8-hydroxyquinoline ligand, and OAc represents an acetic acid ligand. The preparation method is simple, raw materials are easy to obtain, and industrial production is easy; and the post-treatment is simple, and the pollution is less. According to the lead-doped titanium-oxygen cluster compound with the medium and high nuclear numbers prepared by the method, due to coordination of the 8-hydroxyquinoline, the band gap width of the titanium-oxygen cluster compound is reduced, and the response capability to visible light is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of materials, photocatalytic materials and fine chemical synthesis, and particularly relates to a lead-doped medium-high nuclear number titanium oxygen cluster compound and a preparation method and application thereof. BACKGROUND

[0002] Aniline is a key organic intermediate for the production of MDI, dyes, medicines and rubber additives. At present, more than 90% of aniline in industry still relies on the catalytic hydrogenation process of nitrobenzene with Raney nickel or supported noble metal (such as Pd / C, Pt / Al2O3) as catalyst. The process needs to be carried out at a high temperature of 100℃-250℃ and a high pressure of 1-5 MPa hydrogen, which has the problem of high energy consumption; at the same time, the noble metal catalyst used is expensive and easy to be deactivated due to sintering, which further increases the cost; and the reaction process is prone to over-hydrogenation to generate cyclohexylamine and other by-products, resulting in a decrease in product selectivity; in addition, its hydrogen source is highly dependent on fossil fuel reforming hydrogen, which indirectly causes a large amount of carbon dioxide emission. Therefore, the development of a green aniline hydrogenation technology that can operate at normal pressure and room temperature and uses renewable energy to supply hydrogen has become the focus of attention of the current academic and industrial circles.

[0003] The use of solar energy to drive the reduction of nitrobenzene to aniline at normal temperature and pressure is considered as an important research direction to replace the above-mentioned thermal catalytic process. The currently reported photocatalytic systems are mainly divided into three categories: (1) based on CdS, g-C3N4, BiVO4 and other narrow-bandgap inorganic semiconductor materials, although such materials have good visible light response characteristics, they generally have environmental risks of heavy metal ion dissolution, low quantum efficiency, serious photogenerated carrier recombination and insufficient reduction capacity due to the position of the conduction band; (2) based on TiO2 composite materials loaded with noble metals (such as Au, Pd), the activity of this system is high, but it depends on expensive noble metals, and the intrinsic band gap of TiO2 (~3.2eV) mainly covers the ultraviolet light region, which significantly limits the spectral utilization rate of sunlight; (3) based on the system of homogeneous photosensitizer (such as [Ru(bpy)2] 2+ ) and sacrificial agent (such as TEOA), although a higher activity can be obtained, the catalyst and reaction system are difficult to separate, which hinders its practical application. In summary, the existing photocatalytic systems still generally face the technical challenges of being difficult to balance the catalytic activity, material stability, system cost and environmental friendliness when applied to the hydrogenation of nitrobenzene to aniline.

[0004] Titanium oxo-clusters, as the structural precise models between molecular compounds and TiO2 nanocrystals, possess the inherent stability and semiconductor properties (e.g. suitable photoelectrochemical properties) of TiO2 materials, and their core structure, ligands, defects and surface functional groups can be precisely designed and regulated at the atomic scale, providing a unique opportunity for the development of new photocatalytic materials. However, low-core titanium oxo-clusters (e.g. Ti4, Ti6) usually exhibit significant quantum size effect, resulting in excessive negative shift of the conduction band position, fast recombination rate of photo-generated electron-hole pairs, and limited photocatalytic efficiency; although medium-high core clusters (core number ≥ 20) exhibit more potential for matching in terms of energy band structure and carrier transport, the growth conditions of high-quality single crystals thereof are usually harsh. More importantly, most of the reported medium-high core titanium oxo-clusters lack effective visible light capturing groups, and thus usually have no or little catalytic activity for nitrobenzene hydrogenation reaction under visible light irradiation.

[0005] Therefore, how to precisely construct the synergistic properties of high core (to optimize the carrier behavior), wide spectral response (especially in the visible light region) and high catalytic activity in titanium oxo-clusters through ligand engineering or metal doping strategies, overcome the bottleneck of existing titanium oxo-clusters in photocatalytic nitrobenzene hydrogenation application, and thus obtain a new type of photocatalytic material with high efficiency, stability, controllable cost and environmental friendliness, has become a research direction with great development potential in the field, and is also a technical problem urgently to be solved in the field. SUMMARY

[0006] In view of the above shortcomings of the prior art, the purpose of the present application is to provide a lead-doped medium-high core number titanium oxo-cluster, a preparation method and application thereof, which can effectively solve the problems existing in the prior art.

[0007] In order to achieve the above object or other objects, the present application is implemented by the following technical solutions.

[0008] A lead-doped medium-high core number titanium oxo-cluster, the molecular formula of the medium-high core number titanium oxo-cluster is H3Ti 16 Pb6(μ4-O)4(μ3-O) 12 (μ2-O) 10 (Bz) 18 (OQ)8(OAc), which is briefly denoted as Ti 16 Pb6; wherein μ4-O represents a four-bridging O atom, μ3-O represents a three-bridging O atom, μ2-O represents a two-bridging O atom, Bz represents a benzoic acid ligand, OQ represents an 8-hydroxyquinoline ligand, and OAc represents an acetic acid ligand.

[0009] The crystal system of the crystal state of the lead-doped medium-high core number titanium oxo-cluster of the present application is triclinic, the space group is P-1, the unit cell parameters a is b is c is a is 78.4°, b is 72.5°, g is 64.3°, and the unit cell volume is

[0010] The cluster core size of the lead-doped medium-high nuclear number titanium oxide cluster compound of the present application is 1.9 nm to 2.6 nm.

[0011] The lead-doped medium-high nuclear number titanium oxide cluster compound H3Ti 16 Pb6(μ4-O)4(μ3-O) 12 (μ2-O) 10 (Bz) 18 (OQ)8(OAc)(abbreviated as Ti 16 Pb6), the framework is symmetrically assembled by 16 titanium atoms using a binuclear titanium oxide unit, 6 Pb 2+ are differentially coordinated on the Ti-O framework, wherein 4 Pb 2+ are embedded in the framework, 2 Pb 2+ are exposed to the framework surface, and 16 Ti(IV) and 6 Pb(II) are bridged by μ2-O, μ3-O, and μ4-O to form a framework structure, the periphery is stabilized by 18 benzoic acid ligands (Bz), 8 8-hydroxyquinoline ligands, and 1 acetic acid (AcOH) ligand, and the 8-hydroxyquinoline (HOQ) ligand is combined on the metal core surface in a bidentate coordination mode, and the benzoic acid ligand is combined in a monodentate or bidentate coordination mode; the number of μ2-O, μ3-O, and μ4-O bridge oxygens is 10, 12, and 4, respectively.

[0012] The present application also provides a method for preparing the above-mentioned lead-doped medium-high nuclear number titanium oxide cluster compound, comprising the following steps:

[0013] 1) Lead acetate trihydrate, benzoic acid, and 8-hydroxyquinoline are added to a solvent acetonitrile, and stirred and mixed uniformly to obtain a suspension; morpholine and acetic acid are added to the above-mentioned suspension, and continued to be stirred and mixed uniformly;

[0014] 2) Titanium tetraisopropoxide is added to the reaction system obtained in step 1), and stirred and mixed uniformly under sealing, and a heat preservation reaction is performed; after the reaction is completed, the target product is obtained through post-treatment.

[0015] In an example of the present application, the molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, 8-hydroxyquinoline, acetic acid, morpholine, and benzoic acid is (1-4):(1-2):(1-2):(1-2):(1-2):(9-11). Preferably, the molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, 8-hydroxyquinoline, acetic acid, morpholine, and benzoic acid is 3:1:1:2:1:11.

[0016] In an example of the present application, the molar ratio of the solvent acetonitrile to titanium tetraisopropoxide is (23-25):1.

[0017] In an example of the present application, the reaction temperature in step 2) is 95-105°C. If the reaction temperature is too high, the ligand will decompose. If the reaction temperature is too low, the reaction will not be complete. In an example of the present application, the reaction time in step 2) is 7-14 days.

[0018] In an example of the present application, the post-treatment includes but is not limited to washing and vacuum drying. Preferably, acetonitrile is used for washing, the vacuum drying temperature is 20-60°C, and the drying time is 2-24 hours.

[0019] The present application also provides the use of the above-mentioned lead-doped medium-high nuclear number titanium oxide cluster compound in a photocatalytic selective reduction reaction.

[0020] A method for preparing an amine compound by catalyzing a nitroaromatic compound using a photocatalytic selective reduction reaction, which uses a lead-doped medium-high nuclear number titanium oxide cluster compound as a catalyst, and the nitroaromatic compound is selected from one or more of nitrobenzene, 2-nitrochlorobenzene, 4-nitrochlorobenzene, 4-nitro-bromobenzene, 4-nitro-iodobenzene, and 2-nitro-iodobenzene.

[0021] Further, the method comprises the following steps: mixing the catalyst, the lead-doped medium-high nuclear number titanium oxide cluster compound, the nitroaromatic compound, and a reducing agent in methanol, performing a light irradiation reaction under a nitrogen atmosphere, and obtaining the amine compound after the reaction is completed, and recycling the catalyst Ti 16 Pb6after the treatment. 16 Pb6is washed with methanol and dried for recycling.

[0022] In an example of the present application, the molar ratio of the lead-doped medium-high nuclear number titanium oxide cluster compound, the nitroaromatic compound, and the reducing agent is (0.001-0.002):(0.1-0.2):1.

[0023] In an example of the present application, the reducing agent is selected from hydrazine hydrate.

[0024] In an example of the present application, the N2 pressure is 1 atm.

[0025] In an example of the present application, the molar ratio of the solvent methanol to the nitroaromatic compound is (120-125):0.1.

[0026] In an example of the present application, the light irradiation reaction is performed under visible light with λ≥400 nm and light intensity of 134 mW / cm 2 The light irradiation reaction time is 3-4 hours, and the light irradiation temperature is 23-27°C.

[0027] After the light reaction, the treatment methods include but are not limited to: extraction, centrifugation, drying.

[0028] The application provides a lead-doped medium-high nuclear number titanium oxygen cluster compound and a preparation method and application thereof.

[0029] The lead-doped medium-high nuclear number titanium oxygen cluster compound prepared by the preparation method has a reduced band gap width due to the coordination of 8-hydroxyquinoline and the doping of Pb, and the response capability to visible light is improved, so that the medium-high nuclear number titanium oxygen cluster compound can realize high-selectivity hydrogenation of nitroarenes under the driving of visible light. 16 The catalytic rate (TOF=32.3h-1) of the Pb6 is significantly better than that of other ligand-coordinated titanium oxygen cluster compounds. 16 The conversion rate of the Pb6 only decreases from 100% to 94%, and the IR before and after the reaction shows that the crystal structure has no obvious change. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The crystal structure of the single crystal of the lead-doped medium-high nuclear number titanium oxygen cluster compound Ti 16 The crystal photograph of the Pb6 (the crystal photograph is obtained by photographing with a microscope).

[0031] Figure 2 The crystal structure of the single crystal of the lead-doped medium-high nuclear number titanium oxygen cluster compound Ti 16 The crystal structure of the single crystal of the lead-doped medium-high nuclear number titanium oxygen cluster compound Ti

[0032] Figure 3 The crystal structure of the single crystal of the lead-doped medium-high nuclear number titanium oxygen cluster compound Ti 16 The powder X-ray diffraction spectrum of the Pb6.

[0033] Figure 4 The crystal structure of the single crystal of the lead-doped medium-high nuclear number titanium oxygen cluster compound Ti 16 The UV-vis DRS spectrum of the Pb6.

[0034] Figure 5 The crystal structure of the single crystal of the lead-doped medium-high nuclear number titanium oxygen cluster compound Ti 16 The kinetic curve and the corresponding selectivity curve of the Pb6 in the catalytic hydrogenation reaction of nitrobenzene.

[0035] Figure 6 The lead-doped medium-high nuclear number titanium oxo-cluster compound Ti 16 The conversion rate comparison of repeated 4 times experiments of Pb6 in the photocatalytic selective reduction reaction of p-nitrobenzene.

[0036] Figure 7 The lead-doped medium-high nuclear number titanium oxo-cluster compound Ti 16 The conversion rate comparison of repeated 4 times experiments of Pb6 in the photocatalytic selective reduction reaction of p-nitrobenzene. 16 The infrared spectrum comparison chart of Pb6. DETAILED DESCRIPTION

[0037] The present application is further explained by the following specific examples, which should not be construed as limiting. The present application can be carried out by different embodiments and by applying to other specific embodiments, and the details in the present application can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the following examples and features in the examples can be combined with each other without conflict. It should also be understood that the terms used in the examples of the present application are for describing specific embodiments, and are not intended to limit the scope of protection of the present application. The test methods in the following examples are not specified, and are generally carried out under conventional conditions or under the conditions recommended by the manufacturers.

[0038] It should be noted that the terms such as "up", "down", "left", "right", "middle" and "one" in the present application are only for the convenience of description, and are not intended to limit the scope of the present application. The change or adjustment of the relative relationship without substantial change of the technical content is also considered as the scope of the present application.

[0039] 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.

[0040] Example 1

[0041] The lead-doped medium-high nuclear number titanium oxo-cluster compound Ti 16 The preparation method of Pb6 is as follows:

[0042] 1) Benzoic acid (1.34 g, 11 mmol), 8-hydroxyquinoline (0.15 g, 1 mmol) and lead acetate trihydrate (0.38 g, 1 mmol) were added into a 20 mL capacity vial in sequence, 4 mL acetonitrile solution was added as solvent, and the mixture was pre-mixed in a magnetic stirrer (800 rpm) for 5 minutes to form an orange suspension. Then 100 μL of morpholine and 100 μL of glacial acetic acid were added into the system in sequence, and the suspension was continuously stirred for 10 minutes under air atmosphere to mix thoroughly.

[0043] 2) Titanium tetraisopropoxide (0.92 mL, 3.11 mmol) was added into the reaction system, and the orange suspension changed into an orange-red clear solution. The reaction vessel was temporarily sealed and mixed in a magnetic stirrer (800 rpm) for 10 minutes. After thorough mixing, the reaction was further crystallized in an oven at 100 °C for 7 days.

[0044] 3) After the reaction was completed, orange-red transparent block crystals were observed at the bottom of the vial. The crystals were washed with acetonitrile for three times, and then dried in a vacuum oven at 30 °C for 12 hours. The crystals were collected to obtain the target product H3Ti 16 Pb6(μ4-O)4(μ3-O) 12 (μ2-O) 10 (Bz) 18 (OQ)8(OAc) with a yield of 20%.

[0045] The obtained red block crystals were photographed by a microscope, and the obtained photograph is shown in Figure 1 It can be seen that the obtained crystals are block red crystals with a cluster core size of 1.9-2.4 nm.

[0046] The red block crystals were taken for X-ray single crystal diffraction test, and the structure is shown in Figure 2 It is determined that the obtained product is the lead-doped titanium oxygen cluster compound Ti 16 Pb6of the application from the figure. It can be seen that Ti 16 Pb6belongs to the P-1 space group of triclinic system, and is a nano-encapsulated cluster with a length width In addition, the structure of the Ti 16 Pb6cluster is composed of 16 Ti 4+ , 6 Pb 2+It consists of 4 μ4-O, 12 μ3-O, 10 μ2-O, 18 benzoate ions, 8 8-hydroxyquinoline ions, and 1 acetic acid ligand. This cluster is composed of two Ti8Pb3O7 unit structures perpendicular to each other, and its metal framework exhibits a centrosymmetric structure. Furthermore, the Ti8Pb3O7 unit structure is formed by a Pb atom and a μ-O that fixes two completely identical Ti4Pb2O3 layers together in parallel, resulting in a well-balanced overall framework structure. 16 In the Pb6 cluster, all Ti atoms are six-coordinated, exhibiting an octahedral configuration. However, the coordination environment of Pb is heterogeneous, with two Pb atoms exhibiting different coordination environments. 2+ Four Pb atoms are anchored outside the metal framework via four 8-hydroxyquinoline atoms. 2+ It is then anchored to the surface of the Ti-oxo core through bridging oxygen and benzoic acid ligands.

[0047] After thoroughly grinding the red blocky crystals, X-ray powder diffraction analysis was performed. Figure 3 As shown in the figure, the Ti prepared according to the embodiment of the present invention can be seen. 16 The XRD pattern of Pb6 closely matches the simulated pattern in the range of 2θ = 2° to 50°, indicating that the target cluster structure was successfully obtained and the crystal has high purity.

[0048] The dried, red, blocky crystals were ground and mixed with spectroscopically pure barium sulfate at a ratio of 1:50 to 1:200. The powder was then filled into the sample cell. After preheating the UV-Vis spectrophotometer, the wavelength was set to 200–800 nm. Using pure barium sulfate as a reference for calibration, the sample absorbance was scanned, and characteristic peaks were analyzed after background subtraction. The results are as follows: Figure 4 As shown in the figure, Ti 16 The Pb6 cluster exhibits an absorption band edge of 600 nm, indicating that this cluster compound can efficiently respond to visible light. The coordination of 8-hydroxyquinoline and the doping of Pb effectively broaden the photoresponse range, enabling it to exhibit excellent capture capabilities in both the ultraviolet and visible light regions.

[0049] Example 2

[0050] The difference between this embodiment and Example 1 is that the molar ratio of tetraisopropoxide titanium, lead acetate trihydrate, acetic acid, morpholine, 8-hydroxyquinoline and benzoic acid is 1:1:1:2:1:9, the molar ratio of solvent acetonitrile to tetraisopropoxide titanium is 23:1, the reaction temperature is 105℃, the reaction time is 7 days, the vacuum drying temperature is 60℃, and the vacuum drying time is 6 hours.

[0051] Example 3

[0052] The difference between this example and Example 1 is that the molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, acetic acid, morpholine, 8-hydroxyquinoline and benzoic acid is 1:2:1.5:1.5:2:10, the molar ratio of solvent acetonitrile and titanium tetraisopropoxide is 25:1; the reaction temperature is 95°C, the reaction time is 14d, the vacuum drying temperature is 40°C, and the vacuum drying time is 10h.

[0053] Example 4

[0054] The difference between this example and Example 1 is that the molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, acetic acid, morpholine, 8-hydroxyquinoline and benzoic acid is 1:1.5:2:2:1.5:11, the molar ratio of solvent acetonitrile and titanium tetraisopropoxide is 24:1; the reaction temperature is 100°C, the reaction time is 10d, the vacuum drying temperature is 20°C, and the vacuum drying time is 24h.

[0055] Example 5

[0056] The difference between this example and Example 1 is that the molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, acetic acid, morpholine, 8-hydroxyquinoline and benzoic acid is 4:1:2:2:1.5:9, the molar ratio of solvent acetonitrile and titanium tetraisopropoxide is 24:1; the reaction temperature is 100°C, the reaction time is 10d, the vacuum drying temperature is 20°C, and the vacuum drying time is 24h.

[0057] Example 6

[0058] The difference between this example and Example 1 is that the molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, acetic acid, morpholine, 8-hydroxyquinoline and benzoic acid is 4:1.5:1:1:1:10, the molar ratio of solvent acetonitrile and titanium tetraisopropoxide is 24:1; the reaction temperature is 100°C, the reaction time is 10d, the vacuum drying temperature is 20°C, and the vacuum drying time is 24h.

[0059] Application Example 1

[0060] 10mg of lead-doped medium-high nuclear number titanium oxide cluster compound Ti 16 Pb6, 10μL of nitrobenzene, 5mL of methanol, 97μL of hydrazine hydrate and 20mg of diphenyl (as an internal standard) were added into a reaction vessel, stirred uniformly, sealed, and filled with nitrogen for 10min, and a nitrogen-filled balloon was connected to maintain a nitrogen atmosphere and also to prevent loss of substrate. The reaction system was irradiated by a 300W xenon lamp (λ≥400nm) from the side, and the reaction system was placed in a water bath in a well-ventilated light reaction chamber to maintain a constant temperature. Every 30min after the start of the reaction, a reaction solution was taken, extracted with ethyl acetate, and the upper organic phase was analyzed quantitatively by gas chromatography until the nitrobenzene was completely converted. For example, the reaction solution was taken every 30min, and the reaction was stopped after 2h. The reaction solution was extracted with ethyl acetate, and the upper organic phase was analyzed quantitatively by gas chromatography. The results are shown in Table 1. Figure 5As shown in the figure, it can be seen that Ti 16 Pb6can be completely converted within 4h, and aniline is the only product, indicating that the photocatalytic system has a mild reduction ability and good selectivity, and the catalyst Ti 16 The TOF of Pb6is about 32 per mole of catalyst per hour.

[0061] After the reaction, the catalyst Ti 16 Pb6was separated by centrifugation to obtain the catalyst Ti 16 Pb6was washed by methanol and dried. The recovered catalyst Ti 16 Pb6was put into the above photocatalytic selective reduction reaction again, and after the reaction, the catalyst Ti 16 Pb6was recovered, and so on, the catalyst Ti 16 Pb6was put into the above photocatalytic selective reduction reaction for 4 times; the conversion rate of each time is as Figure 6 As shown in the figure, the horizontal coordinate represents the number of cycles of the catalyst put into the reaction, and from the figure, it can be seen that the conversion rate of the catalyst Ti 16 Pb6was 100% when it was put into the photocatalytic nitrobenzene hydrogenation reaction for the first time, and the conversion rate could still reach 94% after four cycles.

[0062] The catalyst Ti 16 Pb6that participated in the photocatalytic nitrobenzene hydrogenation reaction for 4 times was recovered and subjected to infrared spectrum detection, and at the same time, the Ti 16 Pb6of Example 1 was directly subjected to infrared spectrum detection, and the two were compared, and the results are as Figure 7 As shown in the figure, it can be seen that the infrared spectrum of the catalyst after 4 times of photocatalytic nitrobenzene reaction is basically unchanged compared with the infrared spectrum of Ti 16 Pb6before the reaction, and it can be seen that the lead-doped medium-high nuclear number titanium oxide cluster Ti 16 Pb6of the embodiment of the application has excellent stability, and even after 4 times of photocatalytic nitrobenzene hydrogenation reaction, the crystal structure has no obvious change.

[0063] Application Example 2

[0064] The difference between this embodiment and Application Example 1 is that:

[0065] The nitroarene is p-nitrochlorobenzene, and the molar ratio of the lead-doped medium-high nuclear number titanium oxide cluster, p-nitrochlorobenzene, and the reducing agent is 0.001:0.2:1, and other conditions remain unchanged.

[0066] Application Example 3

[0067] The difference between this embodiment and Application Example 1 is that:

[0068] The nitroarene is p-nitrochlorobenzene, the molar ratio of the lead-doped medium-high nuclear number titanium oxide cluster, p-nitrochlorobenzene and the reducing agent is 0.002:0.15:1, and other conditions remain unchanged.

[0069] Application Example 4

[0070] The difference between this embodiment and application example 1 is that:

[0071] The nitroarene is p-nitrochlorobenzene, the molar ratio of the lead-doped medium-high nuclear number titanium oxide cluster, p-nitrochlorobenzene and the reducing agent is 0.002:0.15:1, and other conditions remain unchanged.

[0072] Application Example 5

[0073] The difference between this embodiment and application example 1 is that:

[0074] The nitroarene is p-nitrochlorobenzene, the molar ratio of the lead-doped medium-high nuclear number titanium oxide cluster, p-nitrochlorobenzene and the reducing agent is 0.002:0.15:1, and other conditions remain unchanged.

[0075] Application Example 6

[0076] The difference between this embodiment and application example 1 is that:

[0077] The Ti 16 Pb6prepared in example 2 is used.

[0078] Application Example 7

[0079] The difference between this embodiment and application example 1 is that:

[0080] The Ti 16 Pb6prepared in example 3 is used.

[0081] Application Example 8

[0082] The difference between this embodiment and application example 1 is that:

[0083] The Ti 16 Pb6prepared in example 4 is used.

[0084] The conversion rate and selectivity in application examples 1 to 8 are compared, as shown in table 1, and it can be seen from the table that the selectivity of the lead-doped medium-high nuclear number titanium oxide cluster Ti 16 Pb6prepared in the embodiments of the present application in the hydrogenation reaction of p-nitrochlorobenzene, o-nitrochlorobenzene, p-nitrochlorobenzene and p-nitrochlorobenzene is greater than 99%.

[0085] Table 1 The selectivity of the lead-doped medium-high nuclear number titanium oxide cluster Ti 16 Pb6in the hydrogenation reaction of p-nitrochlorobenzene, o-nitrochlorobenzene, p-nitrochlorobenzene and p-nitrochlorobenzene

[0086]

[0087]

[0088] Comparative Example 1

[0089] Ti 20 Catalytic performance, the steps are as follows:

[0090] The same as Example 1, the catalyst is replaced by [Ti 20 (μ2-O)8(μ3-O) 20 (PA) 14 (OQ) 10 (wherein PA represents propionic acid, OQ represents 8-hydroxyquinoline, which is prepared according to the prior art), and other conditions are not changed; the results show that the selectivity of the visible light driven nitrobenzene hydrogenation reaction is 99%, but the conversion rate within 4h is only 55%, and the titanium oxide cluster compound bonded with 8-hydroxyquinoline is the same, but Ti 16 Pb6 has higher catalytic activity, which may be due to the doping of Pb providing additional active sites for catalytic reaction.

[0091] Comparative Example 2

[0092] TiO2P 25 Catalytic performance comparison, the steps are as follows:

[0093] The same as Example 1, the catalyst is replaced by TiO2P 25 (10mg, commercially available), and other conditions are not changed; after 4h of reaction, there is almost no conversion of nitrobenzene, which proves that the coordination of 8-hydroxyquinoline plays an important role in the photocatalytic hydrogenation of nitroaromatics to form the corresponding amine.

[0094] As can be seen from the above, the lead-doped titanium oxide cluster compound Ti 16 Pb6 has high catalytic activity for the reduction and hydrogenation of nitroaromatics, with a selectivity of more than 99%, high catalytic rate, good stability, and after four cycles of recovery and utilization, its structure still has no obvious change and still has high selectivity.

[0095] The above examples only illustrate the principles and effects of the present application, and are not intended to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

1. A lead-doped mesohigh-nuclear titanium oxo-cluster compound, characterized in that, The medium-high nuclear number titanium oxo-cluster compound has a molecular formula of H3Ti 16 Pb6(μ4-O)4(μ3-O) 12 (μ2-O) 10 (Bz) 18 (OQ)8(OAc), which is briefly denoted as Ti 16 Pb6; wherein, μ4-O represents a four-bridging O atom, μ3-O represents a three-bridging O atom, μ2-O represents a two-bridging O atom, Bz represents a benzoic acid ligand, OQ represents an 8-hydroxyquinoline ligand, and OAc represents an acetic acid ligand.

2. The lead-doped meso-heteroleptic titanium oxo-cluster compound of claim 1, wherein, The crystal system of the crystal state of the medium-high nuclear number titanium oxo-cluster compound is triclinic, the space group is P-1, the cell parameter a is b is c is α is 78.4°, β is 72.5°, γ is 64.3°, and the cell volume is 3. Process for the preparation of the lead-doped meso-heteroleptic titanium oxo-cluster compounds according to claim 1 or 2, characterized in that, The method comprises the following steps: 1) adding lead acetate trihydrate, benzoic acid and 8-hydroxyquinoline into a solvent acetonitrile, stirring and mixing uniformly to obtain a suspension; adding morpholine and acetic acid into the suspension, and continuing to stir and mix uniformly; 2) adding titanium tetraisopropoxide into the reaction system obtained in step 1), stirring uniformly under sealing, and performing a heat preservation reaction; after the reaction is completed, the target product is obtained through post-treatment.

4. The method of claim 3, wherein, The heat preservation reaction temperature in step 2) is 95-105°C, and the reaction time is 7-14 days.

5. The method of claim 3, wherein, The molar ratio of titanium tetraisopropoxide, lead acetate trihydrate, 8-hydroxyquinoline, acetic acid, morpholine and benzoic acid is (1-4) : (1-2) : (1-2) : (1-2) : (1-2) : (9-11).

6. The application of the lead-doped medium-high nuclear number titanium oxide cluster compound of claim 1 or 2, or the lead-doped medium-high nuclear number titanium oxide cluster compound prepared by the method of any one of claims 3-5, in a photocatalytic selective reduction reaction.

7. A method for preparing an amine compound by catalyzing a nitroaromatic compound using a photocatalytic selective reduction reaction, characterized in that, The lead-doped medium-high nuclear number titanium oxide cluster compound of claim 1 or 2, or the lead-doped medium-high nuclear number titanium oxide cluster compound prepared by the method of any one of claims 3-5, is used as a catalyst, and the nitroaromatic hydrocarbon is selected from one or more of nitrobenzene, 2-nitrochlorobenzene, 4-nitrochlorobenzene, 4-nitrobromobenzene, 4-nitroiodobenzene and 2-nitroiodobenzene.

8. The method of claim 7, wherein, The application relates to a method for preparing an amine compound, which comprises the following steps: mixing a catalyst lead-doped medium-high nuclear number titanium oxygen cluster compound and a nitroaromatic compound in methanol, adding a reducing agent, performing a light irradiation reaction under a nitrogen atmosphere, and obtaining the amine compound after treatment, and recycling the catalyst Ti 16 Pb6 16 Pb6 The catalyst Ti 9. The method of claim 8, wherein, One or more of the following technical features are included: The molar ratio of the lead-doped medium-high nuclear number titanium oxide cluster compound, the nitroaromatic hydrocarbon and the reducing agent is (0.001-0.002) : (0.1-0.2) :

1. The reducing agent is selected from hydrazine hydrate.

10. The method of claim 8, wherein, The illumination reaction time is 3-4 hours, and the illumination temperature is 23-27°C.

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