A functionalized polyoxovanadate compound, a preparation method and application thereof in catalyzing oxidation of 5-hydroxymethylfurfural

Abstract

The application provides a kind of functional polyoxovanadate compound, preparation method and its application in catalyzing 5-hydroxymethylfurfural oxidation, belong to polyoxometalate and catalysis chemistry technical field.The functional polyoxovanadate compound can be represented by chemical formula V6O6(OR)4L6(C6H5XO3)4;Wherein, the oxidation number of V is +4, R is selected from methyl, ethyl or propyl, L is selected from imidazole or homologues of imidazole, X is selected from P or As.The functional polyoxovanadate compound structure is novel, preparation method is simple, and can catalyze the reaction of oxygen oxidation 5-hydroxymethylfurfural to prepare 2,5-furandicarboxaldehyde, the conversion rate of catalytic oxidation is high, the selectivity is good, the reaction condition is mild, the catalyst can be recycled and utilized for many times, and the application of such catalyst in biomass conversion is laid.

Description

Technical Field

[0001] The invention belongs to the technical field of polyoxometalates and catalytic chemistry, and relates to a functionalized polyvanadium oxycluster compound, a preparation method and application thereof in catalyzing the oxidation of 5-hydroxymethylfurfural. Background Art

[0002] With the continuous depletion of fossil energy and environmental pollution, the development and utilization of renewable energy has attracted widespread attention worldwide. Compared to fossil energy, biomass energy (including sugars, lignin, lipids, etc.) offers advantages such as widespread availability, rich variety, renewability, and low pollution, making it an effective alternative to fossil energy. Converting biomass feedstock into high-value-added chemical products is one of the key development directions in biomass conversion and utilization.

[0003] 5-Hydroxymethylfurfural (HMF) is an important biomass platform molecule obtained by dehydrating sugars and is considered a key bridge compound between bio-based chemistry and petroleum-based chemistry. The HMF molecular structure contains an aldehyde group and a hydroxyl group. Depending on the site and degree of oxidation, a variety of high-value-added oxidation products can be obtained: including 5-hydroxymethyl-2-furancarboxylic acid, 2,5-furandicarboxaldehyde (DFF), 5-formyl-2-furancarboxylic acid, and 2,5-furandicarboxylic acid. When the degree of oxidation is higher, the CC bond breaks and maleic anhydride can be generated. Among them, the oxidation product DFF is an important intermediate for medicines, fragrances, pesticides, and polymer materials, and is the product with the highest added value in the HMF oxidation reaction.

[0004] From the perspective of "green chemistry," using oxygen as an oxidant is considered a sustainable strategy for HMF oxidation. However, this reaction is thermodynamically challenging because the activation of oxygen requires overcoming a high energy barrier. Furthermore, controlling product selectivity and specifically generating DFF is crucial. To address this issue, a variety of homogeneous and heterogeneous catalysts have been developed. Currently, these primarily include bio-enzymatic, noble metal, and transition metal catalytic systems. Bio-enzymatic systems offer mild reaction conditions and high selectivity. However, enzyme catalysts suffer from long production cycles, poor storage, and instability in the reaction medium, significantly limiting their application in industrial catalysis. Noble metal catalysts offer high activity and selectivity, but are also expensive and unsuitable for large-scale industrial production. In recent years, transition metal catalysts have been explored for the oxidation of HMF to DFF, demonstrating high catalytic activity. Compared to noble metals, transition metals are abundant, inexpensive, and possess excellent catalytic activity and stability, making them promising catalysts. Vanadium, with its diverse oxidation states, exhibits excellent performance in catalyzing redox reactions. Currently, vanadium-containing compounds (such as oxides and complexes) have been used as catalysts for the selective oxidation of HMF. However, these systems generally encounter challenges such as high temperatures, high pressures, and high catalyst requirements. Therefore, based on the current state of this field and potential application needs, the development of efficient, mild, and green catalysts is key to promoting the efficient oxidation of HMF to DFF.

[0005] Chinese invention patent CN104098533A discloses a method for preparing DFF from glucose. Vanadium pentoxide is used as a catalyst and the reaction is carried out at 100°C for 3 hours to oxidize HMF to DFF, achieving a DFF yield (based on glucose) of up to 46.7%.

[0006] Susan K. Hanson et al. disclosed a new complex vanadium catalyst in the article "Mild and Selective Vanadium-Catalyzed Oxidation of Benzylic, Allylic, and Propargylic Alcohols Using Air" (Organic Letters, 2011, 13, 8, 1908-1911), the structure of which is as follows:

[0007]

[0008] The vanadium complex catalyst is used to catalyze the reaction of oxidizing HMF to DFF, and the yield can reach 94%.

[0009] Gary A. Halliday et al., in "One-Pot, Two-Step, Practical Catalytic Synthesis of 2,5-Diformylfuran from Fructose" (Organic Letters, 2003, 5, 11, 2003-2005), disclose a technique for converting fructose into HMF in DMSO, followed by air oxidation of the HMF without separation over a vanadium catalyst to form DFF. The vanadium-containing catalysts used for oxidation include vanadium pentoxide, γ-vanadyl phosphate, δ-vanadyl phosphate, hemihydrated vanadyl phosphate, (VO)4(Ph2PO2)2(OMe)6(MeOH)2, [(VO)4P2O7(OMe)4] -4 (2,4,6-collidinium + )4、[(VO) 12 (PhPO3)8(OH) 12 ] -4 (2,4,6-collidinium + )4, etc. Under the conditions of reaction temperature of 150°C and pressure of 1 atmosphere, the conversion rate of the catalytic oxidation reaction of HMF to DFF is 31%-61%.

[0010] In summary, the prior art has not yet been able to provide a novel functionalized polyvanadium oxycluster compound as a heterogeneous catalyst to further improve the conversion rate and selectivity of the oxidation reaction of HMF to DFF with oxygen as the oxidant. Summary of the Invention

[0011] In view of this, the prior art has not yet provided a novel functionalized polyvanadium oxycluster compound to serve as a heterogeneous catalyst to further improve the conversion and selectivity of the catalytic oxidation reaction of HMF to DFF using oxygen as the oxidant. The present invention aims to provide a functionalized polyvanadium oxycluster compound, a preparation method, and its use in catalytic oxidation.

[0012] To achieve the above-mentioned purpose of the invention, on the one hand, the present invention provides a functionalized polyvanadium oxycluster compound, which can be represented by the chemical formula V6O6(OR)4L6(C6H5XO3)4; wherein the oxidation number of V is +4, R is selected from methyl, ethyl or propyl, L is selected from imidazole or its homologues, and X is selected from P or As.

[0013] Preferably, the propyl group is isopropyl group.

[0014] Preferably, the structure of the compound includes the following features: the coordination mode of vanadium has both a five-coordinated square pyramid configuration and a six-coordinated octahedral configuration.

[0015] More preferably, the structure of the compound further includes the following features: a double-layer skeleton is formed by four penta-coordinated vanadium atoms in the center, the two layers are connected by four phosphorus atoms, and there is a hexa-coordinated vanadium atom at each end.

[0016] More preferably, the structure of the compound also includes the following features: the central skeleton vanadium atom is a square pyramid configuration, connected by sharing edges, and each vanadium atom is connected to four bridging oxygen atoms O b and a terminal oxygen atom O t Coordination, the upper and lower skeletons are connected by phenylphosphonic acid ligands, and the vanadium atoms on the left and right ends are in a six-coordinated octahedral configuration. Each vanadium atom is coordinated with three N atoms from 1-methylimidazole and two bridging oxygen atoms O b and a terminal oxygen atom O t coordination.

[0017] Preferably, L is selected from one of imidazole, 1-methylimidazole, 1-ethylimidazole and 1-propylimidazole.

[0018] More preferably, L is selected from one of imidazole, 1-methylimidazole, 1-ethylimidazole, and 1-n-propylimidazole.

[0019] Preferably, the functionalized polyvanadium oxycluster compound can be represented by one of the following chemical formulas:

[0020] V6O6(OMe)4(mIM)6(C6H5PO3)4, V6O6(OEt)4(eIM)6(C6H5PO3)4,

[0021] V6O6(OiPr)4(pIM)6(C6H5PO3)4, V6O6(OMe)4(IM)6(C6H5PO3)4,

[0022] V6O6(OMe)4(mIM)6(C6H5AsO3)4, V6O6(OEt)4(eIM)6(C6H5AsO3)4,

[0023] V6O6(OiPr)4(pIM)6(C6H5AsO3)4, V6O6(OMe)4(IM)6(C6H5AsO3)4.

[0024] In the above chemical formula, mIM represents 1-methylimidazole, IM represents imidazole, eIM represents 1-ethylimidazole, pIM represents 1-n-propylimidazole; Me represents methyl, Et represents ethyl, iPr represents isopropyl, C6H5PO3 represents phenylphosphonate,

[0025] C6H5AsO3 represents phenylarsonic acid.

[0026] More preferably, the functionalized polyvanadium oxycluster compound can be represented by one of the following chemical formulas:

[0027] V6O6(OMe)4(mIM)6(C6H5PO3)4, V6O6(OEt)4(eIM)6(C6H5PO3)4,

[0028] V6O6(OMe)4(mIM)6(C6H5AsO3)4, V6O6(OEt)4(eIM)6(C6H5AsO3)4,

[0029] V6O6(OiPr)4(pIM)6(C6H5AsO3)4, V6O6(OMe)4(IM)6(C6H5AsO3)4.

[0030] More preferably, the functionalized polyvanadium oxycluster compound can be represented by one of the following chemical formulas:

[0031] V6O6(OMe)4(mIM)6(C6H5PO3)4、V6O6(OMe)4(mIM)6(C6H5AsO3)4、

[0032] V6O6(OiPr)4(pIM)6(C6H5AsO3)4, V6O6(OMe)4(IM)6(C6H5AsO3)4.

[0033] On the other hand, the present invention provides a method for preparing the functionalized polyvanadium oxycluster compound, comprising the following steps:

[0034] Mixing vanadium source 1, vanadium source 2, solvent, imidazole ligand, and organic acid ligand, and performing a solvothermal reaction to obtain a functionalized polyvanadium oxycluster compound;

[0035] Wherein, the imidazole-based ligand is selected from imidazole or its homologues, and the organic acid ligand is selected from phenylphosphonic acid or phenylarsonic acid.

[0036] Preferably, the vanadium source 1 is selected from at least one of ammonium metavanadate, potassium metavanadate, vanadium pentoxide, and sodium metavanadate.

[0037] More preferably, the vanadium source 1 is selected from one of ammonium metavanadate, potassium metavanadate, vanadium pentoxide, and sodium metavanadate.

[0038] Preferably, the vanadium source 2 is selected from at least one of vanadyl acetylacetonate and vanadyl sulfate.

[0039] More preferably, the vanadium source 2 is selected from vanadyl acetylacetonate and vanadyl sulfate.

[0040] Preferably, the solvent is selected from at least one of methanol, ethanol, isopropanol, and N,N-dimethylformamide.

[0041] More preferably, the solvent is a mixture of at least one of methanol, ethanol, isopropanol and N,N-dimethylformamide.

[0042] More preferably, the solvent is a mixture of one of methanol, ethanol, isopropanol and N,N-dimethylformamide.

[0043] Further preferably, the solvent is selected from one of the following mixtures:

[0044] A mixture of methanol and N,N-dimethylformamide in a volume ratio of 3:1; a mixture of ethanol and N,N-dimethylformamide in a volume ratio of 3:1; a mixture of isopropanol and N,N-dimethylformamide in a volume ratio of 3:1.

[0045] Preferably, the imidazole-based ligand is selected from one of imidazole, 1-methylimidazole, 1-ethylimidazole, and 1-propylimidazole.

[0046] More preferably, the imidazole-based ligand is selected from one of imidazole, 1-methylimidazole, 1-ethylimidazole, and 1-n-propylimidazole.

[0047] Preferably, the molar ratio of the vanadium source 1 to the vanadium source 2 is 1.5-2.5:1 in terms of vanadium atoms.

[0048] More preferably, the molar ratio of the vanadium source 1 to the vanadium source 2 is 2:1 in terms of vanadium atoms.

[0049] Preferably, the molar ratio of the imidazole ligand to the organic acid ligand is 1:0.06-0.2.

[0050] Preferably, the mixing is specifically stirring at room temperature for 30 minutes.

[0051] Preferably, the solvent thermal reaction is carried out in a stainless steel reactor lined with polytetrafluoroethylene.

[0052] Preferably, the reaction temperature of the solvothermal reaction is 90-120°C.

[0053] More preferably, the reaction temperature of the solvothermal reaction is 100°C.

[0054] Preferably, the reaction time of the solvothermal reaction is 50-100 h.

[0055] More preferably, the reaction time of the solvothermal reaction is 72 h.

[0056] Preferably, after the solvent thermal reaction, the mixture is cooled to room temperature and then washed.

[0057] More preferably, the washing is washing with ethanol.

[0058] Preferably, the functionalized polyvanadium oxycluster compound is specifically obtained as a green crystalline functionalized polyvanadium oxycluster compound.

[0059] In another aspect, the present invention provides the use of the functionalized polyvanadium oxycluster compound in catalytic oxidation, comprising the following steps:

[0060] 5-Hydroxymethylfurfural, a functionalized polyvanadium oxygen cluster compound and a solvent are mixed and reacted in an oxygen atmosphere to obtain a product 2,5-furandicarboxaldehyde.

[0061] Preferably, the functionalized polyvanadium oxycluster compound is pretreated, specifically comprising the steps of grinding the catalyst sample and vacuum drying it at 100° C. for 4 hours.

[0062] Preferably, the molar ratio of the 5-hydroxymethylfurfural to the functionalized polyvanadium oxycluster compound is 10-15:1.

[0063] More preferably, the molar ratio of the 5-hydroxymethylfurfural to the functionalized polyvanadium oxycluster compound is 12:1.

[0064] Preferably, the mass volume ratio of the 5-hydroxymethylfurfural to the solvent is 15 mg:0.5-2 mL.

[0065] More preferably, the mass volume ratio of the 5-hydroxymethylfurfural to the solvent is 15 mg:1 mL.

[0066] Preferably, the solvent is selected from at least one of toluene, N,N-dimethylformamide, dimethyl sulfoxide, chlorobenzene and xylene.

[0067] More preferably, the solvent is selected from one of toluene, N,N-dimethylformamide, dimethyl sulfoxide and chlorobenzene.

[0068] Preferably, the reaction temperature is 80-100°C.

[0069] More preferably, the reaction temperature is 90°C.

[0070] Preferably, the reaction time is 4-6 hours.

[0071] More preferably, the reaction time is 5 h.

[0072] Preferably, the reaction in an oxygen atmosphere is specifically:

[0073] An oil bath was used as the heating source, a Schlenk flask was used as the reactor, and an O2 balloon was used to provide the oxygen source for the reaction.

[0074] Preferably, after the reaction is completed, the functionalized polyvanadium oxycluster compound is filtered and recovered for recycling.

[0075] More preferably, the recycling method is: the recovered catalyst is washed three times with ethanol and vacuum dried at 60° C. for 4 hours before being used in the next cycle.

[0076] More preferably, the effective number of recycling times is 5-10 times.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] (1) The present invention provides a novel functionalized polyvanadium oxycluster compound and a preparation method thereof. Imidazole ligands and organic acid ligands are simultaneously introduced into the polyvanadium oxycluster compound to obtain a novel polyvanadium oxycluster compound with high purity and crystalline form, further expanding the scope of the functionalized polyvanadium oxycluster compound family.

[0079] (2) The functionalized polyvanadium oxycluster compound provided by the present invention can catalyze the oxidation reaction of HMF to DFF by oxygen. By using the natural green oxidant oxygen, the reaction conditions are milder, achieving higher conversion rate and selectivity.

[0080] (3) The functionalized polyvanadium oxycluster compound provided by the present invention can be used as a heterogeneous catalyst, which is beneficial for cleaning, separation and reuse of the catalyst, and also facilitates the separation and purification of the product organic molecules.

[0081] (4) The functionalized polyvanadium oxycluster compound provided by the present invention is simple to synthesize, does not use expensive ligands and precious metal elements, and has good catalytic performance, laying the foundation for the application of such catalysts in biomass conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 This is the infrared spectrum of the functionalized polyvanadium oxycluster compound prepared in Example 1.

[0083] Figure 2 is a molecular structure diagram of the functionalized polyvanadium oxycluster compound prepared in Example 1.

[0084] Figure 3 is the powder X-ray diffraction pattern of the functionalized polyvanadium oxycluster compound prepared in Example 1.

[0085] Figure 4 This is a graph showing the changes in HMF and DFF contents over time during the HMF oxidation reaction catalyzed by the functionalized polyvanadium oxycluster compound prepared in Example 1, wherein the circles represent the HMF concentration of the reactant and the triangles represent the DFF concentration of the product. DETAILED DESCRIPTION

[0086] The following non-limiting examples are provided to enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way. The following is merely an illustrative description of the scope of the present invention, and those skilled in the art may make various changes and modifications to the present invention based on the disclosed content, which should also fall within the scope of the present invention.

[0087] The present invention will be further described below by way of specific examples. The various chemical reagents used in the examples of the present invention were obtained through conventional commercial channels unless otherwise specified. Unless otherwise specified, the contents described below are all by weight. Unless otherwise specified, it is understood that the experiments were conducted at room temperature.

[0088] In the following examples, the sources of raw materials are as follows:

[0089]

[0090]

[0091] Here, DMF refers to N,N-dimethylformamide, and DMSO refers to dimethyl sulfoxide.

[0092] In the following examples, the instrument information is as follows:

[0093] Instrument name Instrument model Instrument Manufacturer Gas chromatograph GC-2014C Shimadzu mass spectrometer 7890A-5975C Agilent X-ray powder diffractometer Bruker D8 Brooke infrared spectrometer Nicolet 170XFT-IR Shimadzu X-ray single crystal diffractometer Bruker APEX-IICCD Brooke Blast drying oven DHG-9030A Yiheng

[0094] Example 1

[0095] (1) A method for preparing a functionalized polyvanadium oxycluster compound.

[0096] 0.117 g of ammonium metavanadate (1 mmol), 0.132 g of vanadyl acetylacetonate (0.5 mmol), and 0.10 g of phenylphosphonic acid (0.6 mmol) were dissolved in a mixture of 6 mL of methanol and 2 mL of DMF. 600 μL of 1-methylimidazole was added and stirred at room temperature for 30 minutes. Once completely dissolved, the mixture was placed in a 25 mL Teflon-lined stainless steel reactor and reacted at 100°C for 72 hours. The mixture was then cooled to room temperature and washed with ethanol to yield green crystals, the functionalized polyvanadium oxycluster compound (hereinafter referred to as V-1).

[0097] The above compound V-1 was characterized by infrared spectroscopy, and the results were as follows: Figure 1 As shown. Figure 1 It can be seen that the characteristic vibration is mainly caused by 1-methylimidazole and phenylphosphonic acid groups. It can be observed at 1635cm -1 The characteristic peak at 1100 cm is caused by the stretching vibration of C=C and C=N of imidazole, and the stretching vibration of P=O is at 1100 cm -1 1000cm-1 The following characteristic peaks are mainly inorganic group vibrations. Specifically, the terminal V=O t Vibration (O t : terminal oxygen atom) appears at 940 cm -1 and 980cm -1 660cm -1 , 590cm -1 and 570cm -1 Can be assigned to VO b -V vibration (O b : bridging oxygen atom).

[0098] The structure of compound V-1 was characterized by X-ray single crystal diffraction. Figure 2 As shown. It can be seen that the double-layer skeleton is formed by four five-coordinated vanadium atoms in the center, and the two layers are connected by four phosphorus atoms, with a six-coordinated vanadium atom at each end. The central skeleton vanadium atoms are in a square pyramid configuration, connected by sharing edges, and each vanadium atom is connected to four bridging oxygen atoms O b and a terminal oxygen atom O t Coordination. The upper and lower skeletons are connected by phenylphosphonic acid ligands. The vanadium atoms on the left and right ends are in a six-coordinated octahedral configuration. Each vanadium atom is coordinated with three N atoms from 1-methylimidazole and two bridging oxygen atoms O b and a terminal oxygen atom O t coordination.

[0099] Powder X-ray diffraction was used to characterize V-1. Figure 3 shown. Figure 3 The experimentally determined X-ray diffraction pattern of compound V-1 is consistent with the peak positions of the theoretical simulation data, which indicates that the compound has a high phase purity.

[0100] (2) A method for catalyzing the oxidation of HMF.

[0101] During the catalytic reaction, an oil bath was used as the heating source, a Schlenk flask was used as the reactor, and an O2 balloon was used to provide the oxygen source. Before each catalytic reaction, the catalyst was pretreated by vacuum drying. The catalyst sample was ground and vacuum dried at 100°C for 4 hours. HMF (15 mg, 0.11 mmol), V-1 (15 mg) and toluene (1 mL) were added to a Schlenk tube equipped with an O2 balloon and heated at 90°C for 5 hours. After the reaction, the catalyst was separated by filtration and quantitatively analyzed by gas chromatography. For the cycle test, the collected catalyst was washed three times with ethanol and vacuum dried at 60°C for 4 hours before being used in the next cycle.

[0102] The type of product was determined by nuclear magnetic resonance spectroscopy, and the experimental results were quantitatively analyzed by gas chromatography-internal standard method. Biphenyl was selected as the internal standard to complete the determination of HMF and DFF standard curves. The changes of HMF and DFF content in the catalytic system over time are shown in Figure 2. Figure 4 shown.

[0103] Example 2

[0104] (1) A method for preparing a functionalized polyvanadium oxycluster compound.

[0105] 0.138 g of potassium metavanadate (1 mmol), 0.132 g of vanadyl acetylacetonate (0.5 mmol), and 0.10 g of phenylphosphonic acid (0.6 mmol) were dissolved in a mixture of 6 mL of ethanol and 2 mL of DMF. 600 μL of 1-ethylimidazole was added and stirred at room temperature for 30 minutes. Once completely dissolved, the mixture was placed in a 25 mL Teflon-lined stainless steel reactor and reacted at 100°C for 72 hours. The mixture was then cooled to room temperature and washed with ethanol to yield green crystals, which were the functionalized polyvanadium oxycluster compound (hereinafter referred to as V-2).

[0106] (2) A method for catalyzing the oxidation of HMF.

[0107] During the catalytic reaction, an oil bath was used as the heating source, a Schlenk flask was used as the reactor, and an O2 balloon was used to provide the oxygen source. Before each catalytic reaction, the catalyst was pretreated by vacuum drying. The catalyst sample was ground and vacuum dried at 100°C for 4 hours. HMF (15 mg, 0.11 mmol), V-2 (20 mg) and DMF (1 mL) were added to a Schlenk tube equipped with an O2 balloon and heated at 90°C for 5 hours. After the reaction, the catalyst was separated by filtration and quantitatively analyzed by gas chromatography. For the cycle test, the collected catalyst was washed three times with ethanol and vacuum dried at 60°C for 4 hours before being used in the next cycle.

[0108] Example 3

[0109] (1) A method for preparing a functionalized polyvanadium oxycluster compound.

[0110] 0.188 g of vanadium pentoxide (1 mmol), 0.132 g of vanadyl acetylacetonate (0.5 mmol), and 0.10 g of phenylphosphonic acid (0.6 mmol) were dissolved in a mixture of 6 mL of isopropanol and 2 mL of DMF. 1-n-propylimidazole (600 μL) was added and stirred at room temperature for 30 minutes. Once completely dissolved, the mixture was placed in a 25 mL stainless steel reactor lined with polytetrafluoroethylene and reacted at 100°C for 72 hours. The mixture was then cooled to room temperature and washed with ethanol to yield green crystals, the functionalized polyvanadium oxycluster compound (hereinafter referred to as V-3).

[0111] (2) A method for catalyzing the oxidation of HMF.

[0112] During the catalytic reaction, an oil bath was used as the heating source, a Schlenk flask was used as the reactor, and an O2 balloon was used to provide the oxygen source. Before each catalytic reaction, the catalyst was pretreated by vacuum drying. The catalyst sample was ground and vacuum dried at 100°C for 4 hours. HMF (15 mg, 0.11 mmol), V-3 (10 mg) and DMSO (1 mL) were added to a Schlenk tube equipped with an O2 balloon and heated at 90°C for 5 hours. After the reaction, the catalyst was separated by filtration and quantitatively analyzed by gas chromatography. For the cycle test, the collected catalyst was washed three times with ethanol and vacuum dried at 60°C for 4 hours before being used in the next cycle.

[0113] Example 4

[0114] (1) A method for preparing a functionalized polyvanadium oxycluster compound.

[0115] 0.121 g of sodium metavanadate (1 mmol), 0.081 g of vanadyl sulfate (0.5 mmol), and 0.10 g of phenylphosphonic acid (0.6 mmol) were dissolved in a mixture of 6 mL of methanol and 2 mL of DMF. 300 mg of imidazole was added and stirred at room temperature for 30 minutes. Once completely dissolved, the mixture was placed in a 25 mL Teflon-lined stainless steel reactor and reacted at 100°C for 72 hours. The mixture was then cooled to room temperature and washed with ethanol to yield green crystals, which were the functionalized polyvanadium oxycluster compound (hereinafter referred to as V-4).

[0116] (2) A method for catalyzing the oxidation of HMF.

[0117] During the catalytic reaction, an oil bath was used as the heating source, a Schlenk flask was used as the reactor, and an O2 balloon was used to provide the oxygen source. Before each catalytic reaction, the catalyst was pretreated by vacuum drying. The catalyst sample was ground and vacuum dried at 100°C for 4 hours. HMF (15 mg, 0.11 mmol), V-4 (15 mg) and chlorobenzene (1 mL) were added to a Schlenk tube equipped with an O2 balloon and heated at 100°C for 5 hours. After the reaction, the catalyst was separated by filtration and quantitatively analyzed by gas chromatography. For the cycle test, the collected catalyst was washed three times with ethanol and vacuum dried at 60°C for 4 hours before being used in the next cycle.

[0118] Example 5

[0119] (1) A method for preparing a functionalized polyvanadium oxycluster compound.

[0120] 0.117 g of ammonium metavanadate (1 mmol), 0.132 g of vanadyl acetylacetonate (0.5 mmol), and 0.10 g of phenylarsonic acid (0.5 mmol) were dissolved in a mixture of 6 mL of methanol and 2 mL of DMF. 600 μL of 1-methylimidazole was added and stirred at room temperature for 30 minutes. Once completely dissolved, the mixture was placed in a 25 mL Teflon-lined stainless steel reactor and reacted at 100°C for 72 hours. The mixture was then cooled to room temperature and washed with ethanol to yield green crystals, which were the functionalized polyvanadium oxycluster compound (hereinafter referred to as V-5).

[0121] (2) A method for catalyzing the oxidation of HMF.

[0122] During the catalytic reaction, an oil bath was used as the heating source, a Schlenk flask was used as the reactor, and an O2 balloon was used to provide the oxygen source. Before each catalytic reaction, the catalyst was pretreated by vacuum drying. The catalyst sample was ground and vacuum dried at 100°C for 4 hours. HMF (15 mg, 0.11 mmol), V-5 (15 mg) and toluene (1 mL) were added to a Schlenk tube equipped with an O2 balloon and heated at 90°C for 5 hours. After the reaction, the catalyst was separated by filtration and quantitatively analyzed by gas chromatography. For the cycle test, the collected catalyst was washed three times with ethanol and vacuum dried at 60°C for 4 hours before being used in the next cycle.

[0123] Example 6

[0124] (1) A method for preparing a functionalized polyvanadium oxycluster compound.

[0125] 0.188 g of vanadium pentoxide (1 mmol), 0.081 g of vanadyl sulfate (0.5 mmol), and 0.10 g of phenylarsonic acid (0.5 mmol) were dissolved in a mixture of 6 mL of ethanol and 2 mL of DMF. 600 μL of 1-ethylimidazole was added and stirred at room temperature for 30 minutes. Once completely dissolved, the mixture was placed in a 25 mL Teflon-lined stainless steel reactor and reacted at 100°C for 72 hours. The mixture was then cooled to room temperature and washed with ethanol to yield green crystals, the functionalized polyvanadium oxycluster compound (hereinafter referred to as V-6).

[0126] (2) A method for catalyzing the oxidation of HMF.

[0127] During the catalytic reaction, an oil bath was used as the heating source, a Schlenk flask was used as the reactor, and an O2 balloon was used to provide the oxygen source. Before each catalytic reaction, the catalyst was pretreated by vacuum drying. The catalyst sample was ground and vacuum dried at 100°C for 4 hours. HMF (15 mg, 0.11 mmol), V-6 (15 mg) and chlorobenzene (1 mL) were added to a Schlenk tube equipped with an O2 balloon and heated at 80°C for 5 hours. After the reaction, the catalyst was separated by filtration and quantitatively analyzed by gas chromatography. For the cycle test, the collected catalyst was washed three times with ethanol and vacuum dried at 60°C for 4 hours before being used in the next cycle.

[0128] Example 7

[0129] (1) A method for preparing a functionalized polyvanadium oxycluster compound.

[0130] 0.121 g of sodium metavanadate (1 mmol), 0.132 g of vanadyl acetylacetonate (0.5 mmol), and 0.10 g of phenylarsonic acid (0.5 mmol) were dissolved in a mixture of 6 mL of isopropanol and 2 mL of DMF. 1-n-propylimidazole (600 μL) was added and stirred at room temperature for 30 minutes. Once completely dissolved, the mixture was placed in a 25 mL Teflon-lined stainless steel reactor and reacted at 100°C for 72 hours. The mixture was then cooled to room temperature and washed with ethanol to yield green crystals, the functionalized polyvanadium oxycluster compound (hereinafter referred to as V-7).

[0131] (2) A method for catalyzing the oxidation of HMF.

[0132] During the catalytic reaction, an oil bath was used as the heating source, a Schlenk flask was used as the reactor, and an O2 balloon was used to provide the oxygen source. Before each catalytic reaction, the catalyst was pretreated by vacuum drying. The catalyst sample was ground and vacuum dried at 100°C for 4 hours. HMF (15 mg, 0.11 mmol), V-7 (15 mg) and DMSO (1 mL) were added to a Schlenk tube equipped with an O2 balloon and heated at 90°C for 5 hours. After the reaction, the catalyst was separated by filtration and quantitatively analyzed by gas chromatography. For the cycle test, the collected catalyst was washed three times with ethanol and vacuum dried at 60°C for 4 hours before being used in the next cycle.

[0133] Example 8

[0134] (1) A method for preparing a functionalized polyvanadium oxycluster compound.

[0135] 0.138g of potassium metavanadate (1 mmol), 0.081g of vanadyl sulfate (0.5 mmol), and 0.10g of phenylarsonic acid (0.5 mmol) were dissolved in a mixture of 6mL of methanol and 2mL of DMF. 300mg of imidazole was added and stirred at room temperature for 30 minutes. Once completely dissolved, the mixture was placed in a 25mL Teflon-lined stainless steel reactor and reacted at 100°C for 72 hours. The mixture was then cooled to room temperature and washed with ethanol to yield green crystals, which were the functionalized polyvanadium oxycluster compound (hereinafter referred to as V-8).

[0136] (2) A method for catalyzing the oxidation of HMF.

[0137] During the catalytic reaction, an oil bath was used as the heating source, a Schlenk flask was used as the reactor, and an O2 balloon was used to provide the oxygen source. Before each catalytic reaction, the catalyst was pretreated by vacuum drying. The catalyst sample was ground and vacuum dried at 100°C for 4 hours. HMF (15 mg, 0.11 mmol), V-8 (15 mg) and DMF (1 mL) were added to a Schlenk tube equipped with an O2 balloon and heated at 90°C for 5 hours. After the reaction, the catalyst was separated by filtration and quantitatively analyzed by gas chromatography. For the cycle test, the collected catalyst was washed three times with ethanol and vacuum dried at 60°C for 4 hours before being used in the next cycle.

[0138] In the above Examples 1-8, the chemical formulas corresponding to the functionalized polyvanadium oxycluster compounds V-1 to V-8 are shown in the following table:

[0139] Serial number Chemical formula V-1 <![CDATA[V6O6(OMe)4(mIM)6(C6H5PO3)4]]> V-2 <![CDATA[V6O6(OEt)4(eIM)6(C6H5PO3)4]]> V-3 <![CDATA[V6O6(OiPr)4(pIM)6(C6H5PO3)4]]> V-4 <![CDATA[V6O6(OMe)4(IM)6(C6H5PO3)4]]> V-5 <![CDATA[V6O6(OMe)4(mIM)6(C6H5AsO3)4]]> V-6 <![CDATA[V6O6(OEt)4(eIM)6(C6H5AsO3)4]]> V-7 <![CDATA[V6O6(OiPr)4(pIM)6(C6H5AsO3)4]]> V-8 <![CDATA[V6O6(OMe)4(IM)6(C6H5AsO3)4]]>

[0140] Comparative Example 1

[0141] A method for catalyzing the oxidation of HMF.

[0142] Compared with (2) in Example 1, the catalyst V-1 used was replaced with an equal mass of vanadium pentoxide, and the other conditions were the same as (2) in Example 1.

[0143] Comparative Example 2

[0144] A method for catalyzing the oxidation of HMF.

[0145] Compared with Example 1 (2), the catalyst V-1 was replaced with an equal amount of the phenylphosphonic acid functionalized polyvanadium oxide compound V-9, and the other conditions were the same as those in Example 1 (2).

[0146] The preparation method of the V-9 is as follows:

[0147] 0.138 g of potassium metavanadate (1 mmol), 0.10 g of phenylphosphonic acid (0.6 mmol), and 8 mL of water were stirred and mixed, placed in a hydrothermal reactor for hydrothermal reaction at 180° C. for 116 hours to obtain the phenylphosphonic acid functionalized polyvanadium oxycluster compound V-9.

[0148] The chemical formula of V-9 is: (H3O)[(V3O4)(H2O)(PhPO3)3]

[0149] In the above examples and comparative examples, the catalytic HMF oxidation is specifically the catalytic oxidation of HMF to DFF. The reaction can be expressed as the following formula (I):

[0150]

[0151] In Examples 1-8 and Comparative Examples 1-2, the HMF conversion and selectivity are shown in the following table:

[0152] Serial number HMF conversion rate / % DFF product selectivity / % Example 1 95.1 94.2 Example 2 95.7 90.3 Example 3 92.0 89.3 Example 4 97.4 88.8 Example 5 95.4 94.0 Example 6 91.1 92.1 Example 7 95.5 94.6 Example 8 95.7 94.2 Comparative Example 1 88.0 37.5 Comparative Example 2 89.7 31.5

[0153] As shown in the table above, the functionalized polyvanadium oxycluster compounds provided herein achieve high product selectivity when catalyzing the reaction described in Formula (I), compared to the conventional vanadium-based material vanadium pentoxide (Comparative Example 1). The functionalized polyvanadium oxycluster compounds provided herein, incorporating imidazole ligands, achieve superior conversion and selectivity in the reaction described in Formula (I) in Examples 1-8 compared to Comparative Example 2, which does not incorporate imidazole ligands.

[0154] Further, the effective cycle times of the catalysts in Examples 1-8 were characterized. The specific experimental method was as follows: after the catalysts in (2) of Examples 1-8 were washed and dried, the catalytic oxidation reactions described in the corresponding (2) were repeated, and after each cycle, the HMF conversion rate was calculated. If the HMF conversion rate was less than 80% or the selectivity was less than 75%, the cycle was terminated, and the cycle number was recorded. The effective cycle times of the catalysts in Examples 1-8 are shown in the following table:

[0155] Serial number Effective number of cycles / times Example 1 10 Example 2 8 Example 3 9 Example 4 8 Example 5 9 Example 6 9 Example 7 7 Example 8 9

[0156] As can be seen, the effective cycle times of the catalysts in Examples 1-8 can reach 7-10 times, and the catalysts can be reused.

[0157] Finally, it should be noted that the above content is only used to illustrate the technical solutions of the present application, and is not a limitation on the protection scope of the present application. Simple modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art do not deviate from the essence and scope of the technical solutions of the present application.

Claims

1. A functionalized polyvanadium oxycluster compound, characterized in that: The functionalized polyvanadium oxycluster compound is represented by the chemical formula V6O6(OR)4L6(C6H5XO3)4; wherein the oxidation number of V is +4, R is selected from methyl, ethyl or isopropyl, L is selected from one of imidazole, 1-methylimidazole, 1-ethylimidazole, and 1-propylimidazole, and X is selected from P or As.

2. The functionalized polyvanadium oxycluster compound according to claim 1, characterized in that The structure of the functionalized polyvanadium oxycluster compound includes the following features: the coordination mode of vanadium includes both a five-coordinated square pyramid configuration and a six-coordinated octahedral configuration.

3. The functionalized polyvanadium oxycluster compound according to any one of claims 1 to 2, characterized in that: The functionalized polyvanadium oxycluster compound is represented by one of the following chemical formulas: V6O6(OMe)4(mIM)6(C6H5PO3)4, V6O6(OEt)4(eIM)6(C6H5PO3)4, V6O6(OiPr)4(pIM)6(C6H5PO3)4, V6O6(OMe)4(IM)6(C6H5PO3)4, V6 O6(OMe)4(mIM)6(C6H5AsO3)4, V6O6(OEt)4(eIM)6(C6H5AsO3)4, V6O6(OiPr)4(pIM)6(C6H5AsO3)4, V6O6(OMe)4(IM)6(C6H5AsO3)4.

4. The method for preparing the functionalized polyoxyvanadium cluster compound according to any one of claims 1 to 3, characterized in that: The following steps are involved: Mixing vanadium source 1, vanadium source 2, solvent, imidazole ligand, and organic acid ligand, and performing a solvothermal reaction to obtain a functionalized polyvanadium oxycluster compound; Wherein, the imidazole-based ligand is selected from one of imidazole, 1-methylimidazole, 1-ethylimidazole, and 1-propylimidazole, and the organic acid ligand is selected from phenylphosphonic acid or phenylarsonic acid.

5. The preparation method according to claim 4, characterized in that The vanadium source 1 is selected from at least one of ammonium metavanadate, potassium metavanadate, vanadium pentoxide, and sodium metavanadate; the vanadium source 2 is selected from at least one of acetylacetonato vanadyl and sulfate vanadyl; and the solvent is selected from at least one of methanol, ethanol, isopropanol, and N,N-dimethylformamide.

6. The preparation method according to claim 5, characterized in that The molar ratio of the vanadium source 1 to the vanadium source 2 in terms of vanadium atoms is 1.5-2.5:1; the molar ratio of the imidazole ligand to the organic acid ligand is 1:0.06-0.2; and the solvent is a mixture of any one of methanol, ethanol, and isopropanol and N,N-dimethylformamide.

7. The preparation method according to claim 4, characterized in that The reaction temperature of the solvent thermal reaction is 90-120° C., and the reaction time is 50-100 h.

8. Use of the functionalized polyvanadium oxycluster compound according to any one of claims 1 to 3 or the functionalized polyvanadium oxycluster compound prepared by the preparation method according to any one of claims 4 to 7 in catalyzing the oxidation of 5-hydroxymethylfurfural, characterized in that: The following steps are involved: 5-Hydroxymethylfurfural, a functionalized polyvanadium oxygen cluster compound and a solvent are mixed and reacted in an oxygen atmosphere to obtain a product 2,5-furandicarboxaldehyde.

9. The use according to claim 8, characterized in that The mass ratio of the 5-hydroxymethylfurfural to the functionalized polyvanadium oxycluster compound is 10-15:1; the solvent is selected from at least one of toluene, N,N-dimethylformamide, dimethyl sulfoxide, chlorobenzene, and xylene; the reaction temperature is 80-100° C., and the reaction time is 4-6 hours; after the reaction is completed, the functionalized polyvanadium oxycluster compound is filtered and recovered for recycling.

Images