A cerium cluster compound based on organosilane protection and its preparation method and application

Abstract

The present invention relates to a cerium cluster compound based on organosilane protection and a preparation method and application thereof, belonging to the field of metal cluster compound preparation technology and application. The molecular formula of the cerium cluster compound is C 165 H 183 Ce 13 O 68 Si 24 ; The cerium cluster compound is a pure crystal phase; The cerium cluster compound crystal belongs to the trigonal system, the space group is #imgabs0#, the unit cell parameters are #imgabs1##imgabs2#α=90°, β=90°, γ=120°, #imgabs3# The refluxed siloxane precursor is mixed with a methanol solution of cerium nitrate, and the cluster compound can be obtained under solvent thermal conditions. The preparation method of the present invention is simple and easy to repeat. At the same time, the cluster compound not only has good stability, but also has a unique structure and multiple active metal sites. It shows a good catalytic effect on the classic organic reaction Knoevenagel condensation, and the catalytic reaction conditions are mild, without high temperature and high pressure, and is expected to be used in the fields of drug synthesis and multifunctional polymer preparation.

Description

Technical Field

[0001] The invention relates to a cerium cluster compound based on organosilane protection and a preparation method and application thereof, belonging to the field of metal cluster compound preparation technology and application. Background Art

[0002] The abundance of cerium in the earth's crust is the highest among all rare earth elements (accounting for 0.0046%), and it has two stable oxidation states: Ce. 3+ and Ce 4+ Due to the valence-changing properties of cerium and its excellent ability to store and release oxygen, cerium oxide CeO2 (especially cerium dioxide nanoparticles) has potential application value in catalysis, polishing, energy conversion and other fields.

[0003] In recent years, the research on CeO2 nanoparticles has shown explosive growth, with its application research in the field of catalysis being the most prominent. For example: Patent document CN101811039A discloses the preparation of a sulfur-modified cerium dioxide catalyst and its application in catalytic NO conversion reaction. Patent document CN103820114A discloses a method for preparing cerium dioxide nanorods and its application in catalytic NH3 oxidation reaction. Patent document CN108786825A discloses a method for preparing porous nickel and transition metal-doped cerium dioxide loaded on porous nickel and exhibits high catalytic activity in electrocatalytic hydrogen evolution reaction. In addition, patent documents CN101039876A, CN106974897A, CN108408756A, etc. respectively disclose different preparation methods of cerium dioxide nanoparticles and are respectively applied to chemical mechanical polishing, bio-drug delivery and microwave absorption.

[0004] However, similar to the scientific problems faced by nanoparticle science, the polydispersity of size, agglomeration and surface inhomogeneity make it difficult to conduct a more in-depth systematic study. 3+ The concentration and location of ions, oxygen vacancies, and protonated oxygen species (such as OH -, H2O) and the study of their correlation is extremely challenging. In comparison, nanoclusters have the advantages of atomically precise structure, high monodispersity and purity, and adjustable surface organic ligand functions, and are considered to be an ideal model for correlating material structure and performance. Patent document CN108659234A reports a metal-organic framework structure based on hexanuclear cerium clusters and studies its adsorption properties for hydrogen, carbon dioxide and methane gases. Patent document CN108183225A reports the preparation of a heterometallic cerium-titanium cluster, which is then in-situ polymerized with 3,4-ethylenedioxythiophene to obtain a composite material, which is further applied to lithium-ion battery negative electrode materials. So far, there are relatively few studies on pure cerium nanoclusters, mainly focusing on the preparation of multi-nuclear cerium clusters with organic carboxylic acids as protective ligands (such as Nat. Commun. 2017, 8, 1445; Inorg. Chem. 2021, 60, 1641; Inorg. Chem.2022, 61, 20461; Chem. Commun. 2012, 48, 1499; Chem. Mater. 2020, 32, 8522). Compared with cerium clusters protected by organic carboxylic acids, cerium clusters protected by organosilane ligands can be used as ideal molecular models of metal catalysts supported by silica, but single-crystalline cerium clusters with organosilane as ligands have not been reported. For this reason, the present invention is proposed. Summary of the invention

[0005] In view of the above-mentioned state of the prior art, the inventors of the present invention have conducted in-depth and extensive research in the field of multi-nuclear cerium clusters in order to find multi-nuclear cerium clusters that can show good catalytic effects on organic reactions Knoevenagel condensation. The inventors of the present invention have found that using organosilane as a ligand to replace the organic carboxylic acid ligand not only makes the multi-nuclear cerium cluster show multiple active metal sites, but also shows good catalytic effects on organic reactions Knoevenagel condensation. The present invention is realized based on the above-mentioned findings.

[0006] Therefore, an object of the present invention is to provide a multi-core cerium cluster with organosilane as ligand. The multi-core cerium cluster has a unique structure and multiple active metal sites. Compared with the existing multi-core cerium cluster with organic carboxylic acid as ligand, the multi-core cerium cluster with organosilane as ligand of the present invention has twelve ethanol as terminal ligands in addition to six tetraphenylsiloxane ligands on the periphery, which are relatively easy to leave and expose active metal sites, greatly improving the catalytic reaction activity.

[0007] Another object of the present invention is to provide a method for preparing the multi-nuclear cerium cluster compound with organosilane as ligand. The preparation method is simple and easy to repeat.

[0008] Another object of the present invention is to provide a multi-nuclear cerium cluster compound with organosilane as a ligand, which is used as a catalyst for catalyzing the Knoevenagel condensation reaction, exhibiting a good catalytic effect, and the catalyst has good cycle performance.

[0009] The technical solution for achieving the above-mentioned purpose of the present invention can be summarized as follows:

[0010] A multi-nuclear cerium cluster compound with organosilane as ligand, wherein the molecular formula of the cerium cluster compound is [Ce 13 O8(Ph4Si4O8)6(EtOH) 12 ], the inner core contains thirteen Ce ions; among them: (Ph4Si4O8) is tetraphenylsiloxane organic ligand, and EtOH is ethanol molecule.

[0011] According to the present invention, preferably, the multi-nuclear cerium cluster is R 3(-) space group, unit cell parameters are a = 19.8 Å, b = 19.8 Å, c = 51.4 Å, α = 90 o , β = 90 o , γ = 120 o , V = 17412.7 Å 3 .

[0012] According to the present invention, preferably, the multi-core cerium cluster compound is a pure phase crystalline substance, specifically, a yellow block crystalline substance, and the crystal system is a trigonal system. The multi-core cerium cluster compound is an organosilane cerium cluster compound.

[0013] According to the present invention, preferably, the single crystal molecular structure model of the multi-nuclear cerium cluster is as follows Figure 1 shown.

[0014] According to the present invention, the method for preparing the multi-nuclear cerium cluster compound comprises the following steps:

[0015] The phenyltrialkoxysilane is dissolved in an ethanol solvent, and a base is added and then refluxed. The mixture is then mixed with a mixed solution of acetonitrile and dimethylformamide of a cerium salt, and then triethylamine is added to carry out a solvothermal reaction to obtain a polynuclear cerium cluster.

[0016] According to the present invention, preferably, the phenyltrialkoxysilane is phenyltrimethoxysilane or phenyltriethoxysilane, and phenyltrimethoxysilane is most preferred.

[0017] According to the present invention, preferably, the molar ratio of the alcohol to the phenyltrialkoxysilane is (500-300):1, and more preferably 380:1.

[0018] According to the present invention, preferably, the alkali is selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, and sodium hydroxide is most preferred.

[0019] According to the present invention, preferably, the molar ratio of the base to the phenyltrialkoxysilane is (10-15):1, and more preferably 12:1.

[0020] According to the present invention, preferably, the reflux time is 2-5 hours, most preferably 3 hours.

[0021] According to the present invention, preferably, the cerium salt is selected from cerium chloride and cerium nitrate, and cerium nitrate is most preferred.

[0022] According to the present invention, preferably, the temperature of the solvothermal reaction is 80-120°C, more preferably 90-110°C, and most preferably 100°C.

[0023] According to the present invention, preferably, the solvent thermal reaction time is 40-70 hours, more preferably 45-60 hours, and most preferably 50 hours.

[0024] According to the present invention, the above multi-nuclear cerium cluster compound is used in catalyzing Knoevenagel condensation reaction.

[0025] According to the present invention, a method for catalyzing the Knoevenagel condensation reaction of benzaldehyde and its derivatives with malononitrile comprises the following steps:

[0026] Benzaldehyde or a benzaldehyde derivative, malononitrile and a multi-nuclear cerium cluster compound are added into a solvent, sealed and stirred for reaction, and a Knoevenagel condensation reaction product can be obtained.

[0027] According to the present invention, preferably, the solvent is acetonitrile, methanol, ethanol, dimethyl sulfoxide, dichloromethane, tetrahydrofuran or toluene.

[0028] According to the present invention, preferably, the benzaldehyde derivative is methylbenzaldehyde or bromobenzaldehyde.

[0029] According to the present invention, preferably, the sealed stirring reaction time is 0.5-1 hour.

[0030] The beneficial effects of the present invention are as follows:

[0031] Compared with the prior art, the multi-nuclear cerium cluster compound of the present invention has a unique structure and multiple active metal sites, and the preparation method is simple and easy to repeat. In catalyzing the Knoevenagel condensation reaction, the catalytic reaction conditions are mild, and high temperature, high pressure and inert atmosphere are not required. The catalytic efficiency is high, and the catalyst has good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The Ce with organosilane as ligand in the present invention 13 Molecular structure model diagram of cluster compounds.

[0033] Figure 2 This is the GS-MS chart of the product of Example 8 of the present invention.

[0034] Figure 3 This is the GC chart of the product of Example 8 of the present invention.

[0035] Figure 4 This is the GC chart of the product of Example 10 of the present invention.

[0036] Figure 5 Ce synthesized in Example 1 of the present invention 13 Infrared spectrum of the cluster.

[0037] Figure 6 Ce synthesized in Example 1 of the present invention 13 Solid UV-visible absorption spectrum of the cluster compound. DETAILED DESCRIPTION

[0038] According to a first aspect of the present invention, there is provided a multi-nuclear cerium cluster compound with organosilane as a ligand, wherein the molecular formula of the cerium cluster compound is [Ce 13 O8(Ph4Si4O8)6(EtOH) 12 ], the core contains thirteen Ce ions; wherein: (Ph4Si4O8) is a tetraphenylsiloxane organic ligand, and EtOH is an ethanol molecule. The multi-nuclear cerium cluster of the present invention is hereinafter referred to as Ce 13 Clusters. Free molecules are not included in the molecular formula.

[0039] Ce of the present invention 13 The cluster compound has a unique structure and multiple active metal sites. Compared with the existing multi-core cerium cluster compounds with organic carboxylic acid as ligands, the multi-core cerium cluster compound with organic silane as ligands of the present invention can be used as an ideal molecular model of metal cerium nanoparticles supported by silica.

[0040] In one or more embodiments of the present invention, the Ce 13 The cluster compound is R 3(-) space group, unit cell parameters are a =19.8 Å, b = 19.8 Å, c = 51.4 Å, α = 90 o , β = 90 o , γ = 120 o , V = 17412.7 Å3 .

[0041] In one or more embodiments of the present invention, the Ce 13 The cluster compound is a pure phase crystalline substance, specifically, a yellow block crystalline substance. 13 The crystal system of the cluster compound is trigonal. 13 The cluster compound is an organosilyl cerium cluster compound.

[0042] In one or more embodiments of the present invention, the Ce 13 The single crystal molecular structure model of the cluster compound is as follows Figure 1 As shown, hydrogen atoms are omitted to present the structural effect more clearly.

[0043] According to a second aspect of the present invention, there is provided a method for preparing a multi-nuclear cerium cluster compound using organosilane as a ligand, comprising the following steps:

[0044] Phenyltrialkoxysilane is dissolved in ethanol solvent, and after adding an appropriate amount of base, it is refluxed for a certain period of time, and then mixed with a mixed solution of acetonitrile and dimethylformamide of cerium salt, and then a small amount of triethylamine is added, and the mixture is transferred to a reactor for solvent thermal reaction. After the reaction is completed, it is cooled to room temperature to obtain an organosilane-protected tridecanuclear cerium cluster.

[0045] In one or more embodiments of the present invention, the phenyltrialkoxysilane is phenyltrimethoxysilane or phenyltriethoxysilane, and phenyltrimethoxysilane is most preferred.

[0046] In one or more embodiments of the present invention, the alcohol solvent is preferably methanol, ethanol, isopropanol, tert-butyl alcohol, and most preferably ethanol. The molar ratio of alcohol to phenyltrialkoxysilane is (500-300): 1, and most preferably 380: 1.

[0047] The addition of solvent can promote the alcoholysis and polycondensation of organosilane, which is more controllable than water solvent.

[0048] In one or more embodiments of the present invention, the base is preferably sodium hydroxide, potassium hydroxide, lithium hydroxide, and most preferably sodium hydroxide. The main function of the base is to adjust the pH value of the solution, thereby regulating the degree of hydrolysis and polycondensation of siloxane.

[0049] In one or more embodiments of the present invention, the molar ratio of the base to the phenyltrialkoxysilane is (10-15): 1, most preferably 12: 1.

[0050] In one or more embodiments of the present invention, the reflux time is 2-5 hours, preferably 3 hours. The main purpose of reflux is to control the hydrolysis and polycondensation reaction rates of siloxane.

[0051] In one or more embodiments of the present invention, the cerium salt is selected from cerium chloride and cerium nitrate, and cerium nitrate is most preferred.

[0052] In one or more embodiments of the present invention, the solvothermal reaction temperature is 80-120° C., more preferably 90-110° C., and most preferably 100° C. If the reaction temperature is lower, the reaction time needs to be extended.

[0053] In one or more embodiments of the present invention, the solvent thermal reaction time is 40-70 hours, more preferably 45-60 hours, and most preferably 50 hours.

[0054] According to a third aspect of the present invention, there is provided Ce 13 Application of cluster compounds in catalyzing Knoevenagel condensation reactions.

[0055] Furthermore, a method for catalyzing the Knoevenagel condensation reaction of benzaldehyde and its derivatives with malononitrile is provided, comprising the following steps:

[0056] Benzaldehyde or a benzaldehyde derivative, malononitrile and a multi-nuclear cerium cluster compound are added into a solvent, sealed and stirred for reaction, and a Knoevenagel condensation reaction product can be obtained.

[0057] Knoevenagel condensation reaction, also known as Knoevenagel reaction, refers to the reaction in which compounds with active methylene groups (such as malononitrile, malonate, β-ketoester, cyanoacetate, nitroacetate, etc.) undergo aldol condensation with aldehydes or ketones under the catalysis of alkaline substances such as ammonia, amines or their carboxylates, and dehydrate to obtain α, β-unsaturated dicarbonyl compounds or their related compounds.

[0058] The present invention adopts Ce 13 Cluster compounds are used as catalysts for Knoevenagel condensation reactions, replacing conventional catalysts such as ammonia, amines or their carboxylates. Not only do they have mild catalytic reaction conditions, without the need for high temperature, high pressure and inert atmosphere, but they also have high catalytic efficiency and good cyclic performance.

[0059] In one or more embodiments of the present invention, the solvent is acetonitrile, methanol, ethanol, dimethyl sulfoxide, dichloromethane, tetrahydrofuran or toluene.

[0060] In one or more embodiments of the present invention, the benzaldehyde derivative is methylbenzaldehyde or bromobenzaldehyde.

[0061] In one or more embodiments of the present invention, the sealed stirring reaction time is 0.5-1 hour.

[0062] In one or more embodiments of the present invention, the prepared Ce 13 Cluster catalyst (2 mg), solvent (2 mL), benzaldehyde and its derivatives (1 mmol) and malononitrile (1 mmol) were added to a dry glass bottle, sealed, and stirred at room temperature for a certain period of time without inert gas protection. After the reaction, the product was determined by GC-MS and the conversion rate was determined by GC.

[0063] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The described embodiments are only a part of the present invention, not all embodiments. Based on this, the embodiments described in the present invention and other embodiments obtained by other workers in the field without obvious innovation are all within the scope of protection of the present invention.

[0064] The raw materials, methods and equipment used in the examples are all conventional reagents, methods and equipment in the art. Unless otherwise specified, the reagents and materials involved in the present invention are all commercially available.

[0065] Example 1, Ce 13 Cluster preparation

[0066] A method for preparing a cerium cluster compound based on organosilane protection comprises the following steps:

[0067] Phenyltrimethoxysilane (4.8 g), 50 mL ethanol, and 1.2 g sodium hydroxide were added to a round-bottom flask in sequence, refluxed at 80 °C for 2.5 hours, and cooled to room temperature for use. Accurately weigh 32.6 mg of cerium nitrate and dissolve it in 5 mL of acetonitrile and N,N-dimethylformamide mixed solution, add 20 uL triethylamine, and then add 1 mL of the refluxed solution, transfer to a reactor, keep at 100 °C for 40 hours, and slowly cool to room temperature to obtain yellow block crystals with a yield of 62%.

[0068] Example 2, Ce 13 Cluster preparation

[0069] A method for preparing a cerium cluster compound based on organosilane protection comprises the following steps:

[0070] Phenyltrimethoxysilane (4.8 g), 50 mL ethanol, and 1.0 g sodium hydroxide were added to a round-bottom flask in sequence, refluxed at 80 °C for 2.5 hours, and cooled to room temperature for use. Accurately weigh 32.6 mg of cerium nitrate and dissolve it in 5 mL of acetonitrile and N,N-dimethylformamide mixed solution, add 20 uL triethylamine, and then add 1 mL of the refluxed solution, transfer to a reactor, keep at 100 °C for 40 hours, and slowly cool to room temperature to obtain yellow block crystals with a yield of 60%.

[0071] Example 3, Ce 13Cluster preparation

[0072] A method for preparing a cerium cluster compound based on organosilane protection comprises the following steps:

[0073] Phenyltrimethoxysilane (4.8 g), 50 mL ethanol, and 1.0 g sodium hydroxide were added to a round-bottom flask in sequence, refluxed at 80 °C for 2.5 hours, and cooled to room temperature for use. Accurately weigh 32.6 mg of cerium nitrate and dissolve it in 5 mL of acetonitrile and N,N-dimethylformamide mixed solution, add 30 uL triethylamine, and then add 1 mL of the refluxed solution, transfer to a reactor, keep at 100 °C for 40 hours, and slowly cool to room temperature to obtain yellow block crystals with a yield of 63%.

[0074] Example 4, Ce 13 Cluster preparation

[0075] A method for preparing a cerium cluster compound based on organosilane protection comprises the following steps:

[0076] Phenyltrimethoxysilane (4.8 g), 50 mL ethanol, and 1.2 g sodium hydroxide were added to a round-bottom flask in sequence, refluxed at 80 °C for 3 hours, and cooled to room temperature for use. Accurately weigh 32.6 mg of cerium nitrate and dissolve it in 5 mL of acetonitrile and dimethylformamide mixed solution, add 30 uL triethylamine, and then add 1 mL of the refluxed solution, transfer to a reactor, keep at 100 °C for 40 hours, and slowly cool to room temperature to obtain yellow block crystals with a yield of 65%.

[0077] Example 5, Ce 13 Cluster preparation

[0078] A method for preparing a cerium cluster compound based on organosilane protection comprises the following steps:

[0079] Phenyltrimethoxysilane (4.8 g), 50 mL ethanol, and 1.2 g sodium hydroxide were added to a round-bottom flask in sequence, refluxed at 80 °C for 3 hours, and cooled to room temperature for use. Accurately weigh 32.6 mg of cerium nitrate and dissolve it in 5 mL of acetonitrile and dimethylformamide mixed solution, add 30 uL triethylamine, and then add 1 mL of the refluxed solution, transfer to a reactor, keep at 100 °C for 47 hours, and slowly cool to room temperature to obtain yellow block crystals with a yield of 70%.

[0080] Example 6, Ce 13 Cluster preparation

[0081] A method for preparing a cerium cluster compound based on organosilane protection comprises the following steps:

[0082] Phenyltrimethoxysilane (4.8 g), 50 mL ethanol, and 1.2 g sodium hydroxide were added to a round-bottom flask in sequence, refluxed at 80 °C for 3 hours, and cooled to room temperature for use. Accurately weigh 32.6 mg of cerium nitrate and dissolve it in 5 mL of acetonitrile and dimethylformamide mixed solution, add 30 uL triethylamine, and then add 1 mL of the refluxed solution, transfer to a reactor, keep at 80 °C for 50 hours, and slowly cool to room temperature to obtain yellow block crystals with a yield of 65%.

[0083] Example 7, Ce 13 Cluster preparation

[0084] A method for preparing a cerium cluster compound based on organosilane protection comprises the following steps:

[0085] Phenyltrimethoxysilane (4.8 g), 50 mL ethanol, and 1.2 g sodium hydroxide were added to a round-bottom flask in sequence, refluxed at 80 °C for 3 hours, and cooled to room temperature for use. Accurately weigh 32.6 mg of cerium nitrate and dissolve it in 5 mL of acetonitrile and dimethylformamide mixed solution, add 30 uL triethylamine, and then add 1 mL of the refluxed solution, transfer to a reactor, keep at 100 °C for 20 hours, and slowly cool to room temperature to obtain yellow block crystals with a yield of 61%.

[0086] Example 8: Catalytic Application

[0087] An application of a cerium cluster compound protected by organosilane in a Knoevenagel condensation reaction comprises the following steps:

[0088] The Ce prepared in Example 1 13 Cluster catalyst (2 mg), dimethyl sulfoxide (2 mL), benzaldehyde (1 mmol) and malononitrile (1 mmol) were added to a dry glass bottle, sealed, and stirred at room temperature for 1 hour. After the reaction was completed, the conversion rate was determined by GC to be 94.5%.

[0089] Example 9: Catalytic Application

[0090] An application of a cerium cluster compound protected by organosilane in a Knoevenagel condensation reaction comprises the following steps:

[0091] The Ce prepared in Example 2 13 The cluster catalyst (2 mg), methanol (2 mL), benzaldehyde (1 mmol) and malononitrile (1 mmol) were added into a dry glass bottle, sealed and stirred at room temperature for 1 hour. After the reaction was completed, the conversion rate was determined by GC to be 87%.

[0092] Example 10: Catalytic Application

[0093] An application of a cerium cluster compound protected by organosilane in a Knoevenagel condensation reaction comprises the following steps:

[0094] The Ce prepared in Example 3 13 Cluster catalyst (2 mg), ethanol (2 mL), benzaldehyde (1 mmol) and malononitrile (1 mmol) were added into a dry glass bottle, sealed and stirred at room temperature for 1 hour. After the reaction was completed, the conversion rate was determined by GC to be 87.72%.

[0095] Example 11: Catalytic Application

[0096] An application of a cerium cluster compound protected by organosilane in a Knoevenagel condensation reaction comprises the following steps:

[0097] The Ce prepared in Example 4 13 The cluster catalyst (2 mg), dichloromethane (2 mL), benzaldehyde (1 mmol) and malononitrile (1 mmol) were added into a dry glass bottle, sealed and stirred at room temperature for 1 hour. After the reaction was completed, the conversion rate was determined by GC to be 88%.

[0098] Example 12: Catalytic Application

[0099] An application of a cerium cluster compound protected by organosilane in a Knoevenagel condensation reaction comprises the following steps:

[0100] The Ce prepared in Example 5 13 The cluster catalyst (2 mg), dimethyl sulfoxide (2 mL), o-bromobenzaldehyde (1 mmol) and malononitrile (1 mmol) were added into a dry glass bottle, sealed, and stirred at room temperature for 1 hour. After the reaction was completed, the conversion rate was determined by GC to be 91.4%.

[0101] Example 13: Catalytic Application

[0102] An application of a cerium cluster compound protected by organosilane in a Knoevenagel condensation reaction comprises the following steps:

[0103] The Ce prepared in Example 6 13 The cluster catalyst (2 mg), dimethyl sulfoxide (2 mL), p-tolualdehyde (1 mmol) and malononitrile (1 mmol) were added into a dry glass bottle, sealed, and stirred at room temperature for 1 hour. After the reaction was completed, the conversion rate was determined by GC to be 74%.

[0104] Example 14: Cyclic Catalytic Application

[0105] As described in Example 8, the Ce prepared in Example 1 13 The cluster catalyst was recycled for 5 times, and the conversion rate was 92.4% as determined by GC after the reaction, indicating that the catalyst had good recyclability.

[0106] Test example: Ce synthesized in Example 1 13 The cluster compound was structurally characterized, and the molecular structure model is shown in the figure Figure 1 The infrared spectrum of the sample is shown in Figure 5 As shown, the solid UV-visible absorption spectrum is as follows Figure 6 shown.

[0107] Figure 2 is the GC-MS diagram of the catalytic reaction product in Example 8, Figure 2 It can be confirmed that the obtained product is the target product.

[0108] Figure 3 This is the GC chart after the catalytic reaction in Example 8 is completed. Figure 3 It can be confirmed that Ce 13 The clusters have higher catalytic efficiency.

[0109] Figure 4 is the GC diagram of the product of Example 10 of the present invention, Figure 4 It can be confirmed that Ce 13 The clusters have higher catalytic efficiency.

[0110] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A multi-nuclear cerium cluster compound with organosilane as ligand, characterized in that: The molecular formula of the cerium cluster is [Ce 13 O8(Ph4Si4O8)6(EtOH) 12 ], the inner core contains thirteen Ce ions; among them: (Ph4Si4O8) is tetraphenylsiloxane organic ligand, and EtOH is ethanol molecule.

2. The method for preparing the multi-nuclear cerium cluster compound according to claim 1, comprising the following steps: The phenyltrialkoxysilane is dissolved in an ethanol solvent, and a base is added and then refluxed. The mixture is then mixed with a mixed solution of acetonitrile and dimethylformamide of a cerium salt, and then triethylamine is added to carry out a solvothermal reaction to obtain a polynuclear cerium cluster.

3. The method for preparing the multi-nuclear cerium cluster compound according to claim 2, characterized in that: The phenyltrialkoxysilane is phenyltrimethoxysilane or phenyltriethoxysilane.

4. The method for preparing a multi-nuclear cerium cluster according to claim 2, characterized in that: The alkali is selected from sodium hydroxide, potassium hydroxide or lithium hydroxide.

5. The method for preparing a multi-nuclear cerium cluster according to claim 2, characterized in that: The cerium salt is selected from cerium chloride or cerium nitrate.

6. The method for preparing the multi-nuclear cerium cluster according to claim 2, characterized in that: The molar ratio of ethanol to phenyltrialkoxysilane is (500-300):

1.

7. The method for preparing a multi-nuclear cerium cluster according to claim 2, characterized in that: The molar ratio of base to phenyltrialkoxysilane is (10-15):

1.

8. The method for preparing a multi-nuclear cerium cluster according to claim 2, characterized in that: The reflux time is 2-5 hours.

9. The method for preparing a multi-nuclear cerium cluster according to claim 2, characterized in that: The temperature of the solvothermal reaction is 80-120°C, and the time of the solvothermal reaction is 40-70 hours.

10. Use of the multinuclear cerium cluster compound according to claim 1 in catalyzing the Knoevenagel condensation reaction of benzaldehyde, o-bromobenzaldehyde, p-methylbenzaldehyde and malononitrile.

11. A method for catalyzing the Knoevenagel condensation reaction of benzaldehyde and its derivatives with malononitrile, comprising using the multi-nuclear cerium cluster compound of claim 1, comprising the following steps: Benzaldehyde or a benzaldehyde derivative, malononitrile and a multi-nuclear cerium cluster compound are added into a solvent, sealed and stirred for reaction, and a Knoevenagel condensation reaction product can be obtained. The benzaldehyde derivative is o-bromobenzaldehyde or p-methylbenzaldehyde.

12. The method for catalyzing the Knoevenagel condensation reaction of benzaldehyde and its derivatives with malononitrile according to claim 11, characterized in that: The solvent is acetonitrile, methanol, ethanol, dimethyl sulfoxide, dichloromethane, tetrahydrofuran or toluene, and the sealed stirring reaction time is 0.5-1 hour.

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