A nitrogen-containing ligand functionalized polyvanadium oxygen cluster compound and its preparation method and application

Abstract

The present invention discloses a nitrogen-containing ligand functionalized polyvanadium oxygen cluster compound, the chemical formula of which is: IV 2O2(OH)2(H2O)2(C 10 H8N2)2]Cl2·8H2O, the compound belongs to the monoclinic system, P twenty one / c Space group, unit cell parameters are: a=9.9679(2)Å, b=15.0712(4)Å, c=10.9311(2)Å; α=90°, β=108.1550(10)°, γ=90°. It is prepared by the reaction of reducing agent hydrazine hydrate, potassium metavanadate and 2,2'-bipyridine under conventional aqueous solution conditions. The material has high stability and excellent catalytic oxidation performance for removing sulfur-containing pollutants; in addition, its preparation process is simple, easy to synthesize, high yield, low cost, and has potential application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of oxygen cluster compounds, and in particular relates to a nitrogen-containing ligand functionalized polyvanadium oxygen cluster compound and a preparation method and application thereof. Background Art

[0002] Polyoxometalates (POM) are usually polynuclear complexes formed by the connection of early transition metal ions, especially elements of Groups VB and VIB, through oxygen atoms. Polyoxometalates can be divided into two categories, isopolyoxometalates (Iso-POM) and heteropolyoxometalates (Hetero-POM), according to their composition. Homopolyanions are obtained by condensation of the same inorganic oxygen-containing acid radical ions, such as Lindqvist-type {V6O 13} polyvanadium oxygen clusters; heteropoly anions are obtained by condensation of different types of inorganic oxygen-containing acid radical ions, such as [V III 3V IV 18 P6O 60 (DACH)3] 9– , where P is a heteroatom, also known as a central atom, and V is an addendaatom, also known as a polyatom (Müller A, Peters F, Pope MT, Gatteschi D, Chem. Rev., 1998, 98, 239−271; Long DL, Burkholder E, Cronin L, Chem. Soc. Rev., 2007, 36, 105−121; M. Piepenbrink, MU Triller, NHJGorman, Angew. Chem. Int. Ed., 2002, 41: 2523–2525; H. Wan, C. Wang, Y. Zhang, et al. Inorg. Chem., 2014, 53, 10498−10505;Wang JL, Liu XM, Du ZY, Xu Y, Dalton Trans., 2021, 50, 7871−7886; Wang L, Zhou BB,Yu K, Inorg. Chem., 2013,52, 5119−5127.).

[0003] As an important branch of polyoxometalates, polyoxovanadate (POV) has a variety of topological structures, in which the metal vanadium has different coordination modes: {VO4} tetrahedral, {VO5} tetrahedral or trigonal bipyramidal, {VO6} octahedral and variable oxidation states. Therefore, polyoxovanadates have shown potential application prospects in catalysis, materials, electrochemistry, magnetism, medicinal chemistry and other fields (Li JK, Wei CP, Guo D, et al, Dalton Trans., 2020, 49, 14148−14157; Monakhov KY, Bensch W, Kögerler P, Chem. Soc. Rev., 2015, 44, 8443−8483; HouY, Han P, Zhang L, et al, Inorg. Chem. Front., 2023, 10, 148−157; Wang K, Niu Y, Zhao D, et al, Inorg. Chem., 2017, 56, 14053−14059; Wang J, Cao J, Du Z, et al, Chinese Chem Lett., 2023, 34, 106917; InoueY, Kodama S, Taya N, et al. Inorg. Chem., 2018, 57, 7491−7494.).

[0004] In the study of organic-inorganic hybrid polyvanadium oxo-cluster materials, nitrogen-containing ligands can usually form N / O−V covalent bonds with metal vanadium ions through N atoms or O atoms; act as counter cations in hybrid materials; connect another metal ion (such as cobalt, copper, zinc, etc.) to the polyvanadium oxo-cluster through coordination bonds, and serve as a framework modification or bridging unit (CAVACO I, PESSOA JC, and DUARTE MT, Polyhedron., 1993, 12(10): 1231–1237; Chen, Q, Zubieta, J, Inorg. Chem. 1990, 29, 1456–1458; Chen B, Huang X, Wang B, et al. Chem. Eur. J., 2013, 19(14): 4408–4413; Hayashi Y, Coordi Chem Rev., 2011, 255, 2270−2280;Inoue Y, Kodama S, Taya N, et al, Inorg. Chem.,2018, 57 (13): 7491−7494;Li J, Huang X, Yang S, et al, Cryst. Growth Des., 2015, 15, 4, 1907–1914; MonakhovKY, Bensch W and Kögerler P, Chem. Soc. Rev., 2015, 44, 8443–8483; Zhang, JL, Zhao QX, Cheng, MY, et al, Tungsten, 2023, doi:org / 10.1007 / s42864-022-00199-6; Li J, Zhang D, Chi Y, et al. Polyoxometalates, 2022, 1(2): 9140012.).

[0005] There are many kinds of organic nitrogen-containing ligands. The introduction and modification of nitrogen-containing ligands can effectively reduce the total charge number and improve the stability of the system. In addition, by combining nitrogen-containing ligands on polyvanadium oxygen clusters, this can not only diversify the structure of POV, but also combine the properties of POV with nitrogen-containing ligands to obtain ideal multifunctionality (see JL Wang, JP Cao, YH Zhu, Q Wang, et al, Sci. Chi. Chem., 2023, 66, 107–116.). In 1993, Pessoa et al. reported a derivative of isopolytetravanadate constructed by two 2,2'-bipyridines and four methoxy groups. The oxygen in two methoxy groups in this compound is a triple bridging oxygen, and the other two methoxy groups are double bridging oxygens. Two 2,2'-bipyridine ligands participate in the coordination as bidentate ligands (see I. Cavaco, JC Pessoa and MT Duarte, Polyhedron. ,1993, 12(10): 1231–1237). In 2002, Krebs et al. synthesized a Lindqvist-type hexavanadium oxycluster stabilized by six methoxy groups, with two ligand-functionalized oxyvanadium groups capping the two sides of the octahedral hexavanadium oxycluster. Lindqvist-hexavanadium oxycluster is very common, but the oxyvanadium group-capped compound is the first reported. The vanadium ion in the oxyvanadium group eventually forms an octahedral configuration of {VO4N2} (see Piepenbrink M, Triller MU, Gorman NHJ, et al. Angew. Chem. Int. Ed., 2002, 41, 2523–2525). In 2003, Dr. Kabanos et al. used methanol containing a certain amount of triethylamine as solvent and used [V VIOCl2(thf)2] and a series of nitrogen-donating bidentate ligands 1,10-phenanthroline, 5-methyl-1,10-phenanthroline, bipyridine and 5,5′-dimethyl-1,10-phenanthroline were used as raw materials to synthesize five examples with [V2 IV V4 V ] core POV-based nitrogen-containing ligand functionalized derivatives. In 2008, Chinese scientists Li Yantuan et al. synthesized a compound with a similar core structure to the above-mentioned compound, except that the organic nitrogen-containing ligand was different (see Manos MJ, Tasiopoulos AJ, Tolis EJ, et al. Chem. Eur. J., 2003, 9(3): 695–703; Zhang GL, Li YT, Luo XQ, et al. Z. Anorg. Allg. Chem., 2008, 634(6): 1161–1165.). The above reports all focus on the structure, magnetism and electrochemistry of polyvanadium oxoclusters, and no reports on the use of polyvanadium oxoclusters functionalized with nitrogen-containing ligands for catalysis have been found.

[0006] Subsequently, Professor Hu Changwen's research group at Beijing Institute of Technology reported three nitrogen-containing ligand-functionalized compounds V in 2013. IV 2V V 4O 14 (mIM)8, V IV 2V V 4O 14 (eIM)8 and V V 6O 15 (mIM)8 (mIM and eIM are methylimidazole and ethylimidazole, respectively). IV 2V V 4O 14 (eIM)8 shows excellent activity in the dehydrogenation of oxidative alcohols. The authors speculate that the possible catalytic reaction mechanism is: V IV / V V The presence of mixed-valent vanadium species may accelerate the transfer of electrons, thereby initiating the catalytic reaction. IV 2V V 4O 14 (eIM)8 and V V 6O 15 (mIM)8 catalyzes the dehydrogenation of benzyl alcohol and found that under the same conditions, V IV 2V V 4O 14 (eIM)8 to V V 6O 15(mIM)8 and raw materials VOSO4 and V2O5 all showed higher selectivity and better catalytic activity. This is the first report on the use of nitrogen-containing ligand-functionalized polyvanadium oxygen clusters for alcohol oxidation catalysis (see Chen B, Huang X, Wang B, et al. Chem. Eur. J., 2013, 19(14): 4408–4413.). The Ishii group has reported several cases of nitrogen-containing ligand-functionalized octavanadium oxyclusters, tetravanadium oxyclusters, and heptavanadium oxyclusters, and studied the interconversion of these compounds in different solvents (see Kodama S, Taya N, and Ishii Y, Inorg. Chem., 2014, 53(6): 2754−2756; Kodama S, Taya N, Inoue Y, et al. Inorg. Chem., 2016, 55: 6712−6718; Inoue Y, Kodama S, Taya N, et al. Inorg. Chem., 2018, 57 (13): 7491−7494). Zubieta and Hagrman from the United States reported two examples of terpyridine-functionalized decavanadates [V2O4(terpy)2]3[V 10 O 28 ]·2H2O and nonavanadate [V9O 22 (terpy)3] (see Hagrman P Jand Zubieta J, Inorg. Chem., 2000, 39(15):3252–3260.). The research group of Professor Xu Yan from Nanjing University of Technology reported a 1,2-diaminocyclohexane functionalized twenty-one-nuclear heteropolyvanadium oxycluster anion [V III 3V IV 18 P6O 60 (DACH)3] 9– , the study found that there is ferromagnetic interaction inside the anion cluster (see Wan H, Wang C, ZhangY, et al. Inorg. Chem. , 2014, 53(19): 10498−10505.). In recent years, it has been found that polyvanadates show better catalytic activity than polytungstates and polymolybdates (see Mizuno N, Kamata K, Coordin Chem Rev., 2011, 255, 2358−2370; Wang J, Liu X, Du Z and Xu Y, Dalton Trans.,2021, 50, 7871−7886.). In 2021, Su Zhongmin's research group reported two octahedral and rhombic dodecahedral compounds constructed by oxygen-containing ligands, aromatic polycarboxylic acid ligands and {V5O9Cl} building blocks. Among them, the dodecahedral compounds, as heterogeneous catalysts, showed efficient and universal catalytic activity in oxidative desulfurization. Although the ligands of this type of compound contain nitrogen elements, the nitrogen atoms do not participate in the coordination (see Gan HM, Qin C, Zhao L, et al, Cryst. Growth Des., 2021, 21, 2, 1028−1034.). In 2022, Chi Yingnan's group at Beijing Institute of Technology reviewed the catalysis of polyvanadium oxygen clusters in the selective oxidation of organic molecules (see Li J, Zhang D, Chi Y, et al, Polyoxometalates , 2022, 1, 9140012), the review found that the research on catalysis of polyvanadium oxygen clusters functionalized with organic nitrogen-containing ligands mainly focuses on the oxidative dehydrogenation reaction of alcohols, and the research in the field of catalytic oxidative desulfurization is relatively small. In 2023, Xu Yan's research group at Nanjing University of Technology synthesized four Z-type hexavanadium oxygen clusters constructed with nitrogen-containing ligands, which can be used as efficient heterogeneous catalysts for CO2 cycloaddition and oxidative desulfurization reactions (see Wang J, Cao J, Du Z, et al, Chinese Chem. Lett., 2023, 34, 106917). Summary of the invention

[0007] The present invention aims to overcome the defects of the prior art and provide a novel nitrogen-containing ligand functionalized polyvanadium oxycluster compound and a preparation method and application thereof.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] A nitrogen-containing ligand functionalized polyvanadium oxygen cluster compound, the chemical formula of which is: IV 2O2(OH)2(H2O)2(C 10 H8N2)2]Cl2·8H2O, the compound belongs to the monoclinic system, P twenty one / c Space group, unit cell parameters are: a=9.9679(2)Å, b=15.0712(4)Å, c=10.9311(2)Å; α=90°, β=108.1550(10)°, γ=90°.

[0010] A method for preparing the above-mentioned nitrogen-containing ligand functionalized polyvanadium oxygen cluster compound comprises the following steps: reacting a potassium metavanadate aqueous solution with a hydrazine hydrate solution at 80-95°C for more than 1 hour, then adding 2,2'-bipyridine and β-alanine solid to the system while hot, adjusting the pH to 2.4-4.2 (a person skilled in the art can determine the amount of hydrochloric acid solution by conventional techniques), then reacting at 80-95°C for 2-6 hours, filtering while hot, cooling the filtrate, standing it, and precipitating crystals to obtain the compound.

[0011] Specifically, potassium metavanadate (KVO3) solid can be first dissolved in 80-95°C hot water, and then 80±10% hydrazine hydrate solution is added and reacted for 1-3 hours.

[0012] Furthermore, the molar ratio of potassium metavanadate, reducing agent hydrazine hydrate, 2,2'-bipyridine and β-alanine is preferably 2:1:(0.42-1.34):1-2.

[0013] During the preparation of the nitrogen-containing ligand functionalized polyvanadium oxycluster compound, dilute hydrochloric acid can be used to adjust the pH. The dilute hydrochloric acid used is a commercially available product and is diluted using a volumetric flask before use. The use of dilute hydrochloric acid is a conventional technique in the art, and those skilled in the art can also select a hydrochloric acid solution of a corresponding concentration as needed.

[0014] The present invention also provides the use of the polyvanadium oxygen cluster compound functionalized with nitrogen-containing ligands in catalytic oxidation of sulfides.

[0015] The above-mentioned nitrogen-containing ligand functionalized polyvanadium oxycluster compound is used in the catalytic oxidation of sulfides. Specifically, the sulfides may include toluene sulfide, diphenyl sulfide, alkyl sulfides (such as dipropyl sulfide, dibutyl sulfide), thiophenes (such as dibenzothiophene, benzothiophene), etc.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1) The present invention provides a novel nitrogen-containing ligand functionalized polyvanadium oxygen cluster compound, which has a simple preparation process, is easy to synthesize, has a high yield, low cost, and has potential application prospects.

[0018] 2) The present invention found that the polyvanadium oxycluster compound material has high stability. The test results show that the polyvanadium oxycluster compound functionalized with nitrogen-containing ligand has excellent catalytic oxidation performance of various sulfur-containing pollutants (including toluene sulfide, diphenyl sulfide, alkyl sulfides such as dipropyl sulfide, dibutyl sulfide, thiophenes such as dibenzothiophene, benzothiophene, etc.), and is a potential material for catalytic removal of sulfur-containing organic pollutants, and can be used in homogeneous catalytic oxidation desulfurization. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The crystal structure diagram of the polyvanadium oxycluster compound monomer functionalized with nitrogen-containing ligands of the present invention;

[0020] Figure 2 is a π-π stacking diagram of the polyvanadium oxycluster compound functionalized with nitrogen-containing ligands of the present invention in space;

[0021] Figure 3 The infrared spectrum of the polyvanadium oxygen cluster compound functionalized with nitrogen-containing ligands of the present invention;

[0022] Figure 4 The figure is the powder X-ray diffraction pattern of the polyvanadium oxycluster compound functionalized with nitrogen-containing ligands of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto.

[0024] In the following examples, the raw materials used are all commercially available products that can be directly purchased or prepared using conventional techniques in the art. For example, dilute hydrochloric acid is a commercially available product and is diluted using a volumetric flask before use. The use of dilute hydrochloric acid is a conventional technique in the art, and those skilled in the art may also select hydrochloric acid solutions of other concentrations as needed. Room temperature refers to 25±5°C.

[0025] Example 1

[0026] A preparation method of a nitrogen-containing ligand functionalized polyvanadium oxygen cluster compound comprises the following steps: weighing 6.90g KVO3 (50.0 mmol) and dissolving it in 150mL 90°C hot water; after complete dissolution, adding 1.5mL hydrazine hydrate solution (80wt%, 24.75 mmol) and reacting for 1 hour; then adding 5.2g (33.3 mmol) of 2,2-bipyridine solid and 2.3g (25.8 mmol) of β-alanine; then adjusting the pH to 2.4 with 2moL / L dilute hydrochloric acid solution; then reacting at 90°C for 3.5 hours and filtering while hot; cooling to room temperature; and filtrating the filtrate overnight (12h) to obtain yellow-green crystals; and the crystals are post-treated (filtering, washing, drying, the same below) to obtain a yield of 68%.

[0027] Example 2

[0028] A preparation method of a nitrogen-containing ligand functionalized polyvanadium oxygen cluster compound comprises the following steps: dissolving 6.90 g KVO3 (50.0 mmol) in 150 mL 90°C hot water, adding 1.5 mL hydrazine hydrate solution (80 wt%, 24.75 mmol) after complete dissolution, reacting for 1 hour, adding 2.6 g (16.7 mmol) of 2,2'-bipyridine solid and 2.3 g (25.8 mmol) of β-alanine, adjusting the pH to 3.4 with 2 mol / L dilute hydrochloric acid solution, reacting at 80°C for 3.5 hours, filtering while hot, cooling to room temperature, and filtrating the filtrate overnight to obtain yellow-green crystals, which are obtained by post-treatment with a yield of 33%.

[0029] Example 3

[0030] A preparation method of a nitrogen-containing ligand functionalized polyvanadium oxygen cluster compound comprises the following steps: dissolving 6.90 g KVO3 (50.0 mmol) in 150 mL 90°C hot water, adding hydrazine hydrate solution (80%, 1.0 mL, 24.75 mmol) to react for 1 hour after the mixture is completely dissolved, adding 1.6 g (10.3 mmol) of 2,2'-bipyridine solid and 2.3 g (25.8 mmol) of β-alanine, adjusting the pH to 4.2 with 2 mol / L dilute hydrochloric acid solution, reacting at 90°C for 2 hours, filtering while hot, cooling to room temperature, and filtrating the filtrate overnight to obtain yellow-green crystals, which are obtained by post-treatment with a yield of 12%.

[0031] The products prepared in Examples 1 to 3 above were tested, and it was found that the chemical formula of the products was: [V IV 2O2(OH)2(H2O)2(C 10 H8N2)2]Cl2·8H2O. This compound belongs to the monoclinic system. P twenty one / c The space group and unit cell parameters are: a=9.9679(2)Å, b=15.0712(4)Å, c=10.9311(2)Å; α=90°, β=108.1550(10)°, =90°. The analysis of C, H, N and metal elements shows that for the molecular formula C 20 H 38 N4O 14 The elemental analysis results (%) of the compound of V2Cl2 are as follows: C, 32.84; H, 5.24; V, 13.93; N, 7.66; Cl, ​​9.70. Measured values: C, 32.36; H, 5.01; V, 13.81; N, 7.42. The valence state of vanadium in the compound of the present invention is shown by bond valence calculation (BVS) to be +4 (Table 1). The structural diagram of the polyvanadium oxygen cluster compound functionalized with nitrogen-containing ligands of the present invention is as follows: Figure 1As shown, Figure 1 The crystal structure diagram of the monomer of polyvanadium oxo cluster compound functionalized with nitrogen-containing ligands; Figure 2 This is the π-π stacking diagram of polyvanadium oxoclusters functionalized with nitrogen-containing ligands in space.

[0032] Table 1. BVS results of vanadium atoms in the compounds of the present invention

[0033]

[0034] The structure of the polyvanadium oxy-cluster compound functionalized with nitrogen-containing ligands of the present invention is described as follows: Most of the conventionally reported polyvanadium oxy-cluster compounds are polyanions, while the polyvanadium oxy-cluster synthesized in the present invention is a polycation, which is very rare. The compound molecule contains two Cl − ion, a[V IV 2O2(OH)2(H2O)2(C 10 H8N2)2] 2+ Polycation and eight crystal waters. [V IV 2O2(OH)2(H2O)2(C 10 H8N2)2] 2+ The polycation can be regarded as a binuclear homopolyvanadium oxygen cluster unit supporting two 2,2'-bipyridine molecules. The bidentate nitrogen-containing ligand is bound to the V in the [VO2(OH)(H2O)] unit through two nitrogen atoms. 4+ Ion coordination eventually forms an octahedral {VO4N2} coordination configuration, with an average bond length of 1.904Å for the V−O bond and 2.196Å for the V−N bond, both of which are consistent with the conventional values ​​reported in the literature ( Figure 1 ). Two {VO4N2} octahedra are linked together by two double bridging oxygens to form [V IV 2O2(OH)2(H2O)2(C 10 H8N2)2] 2+ Polycation. O1 is a μ2-O atom, which is monoprotonated, and O3 is diprotonated, that is, each vanadium atom is connected to a water molecule at the top, while O2 is a terminal oxygen atom ( Figure 1 ). The distance between the aromatic ring of the 2,2'-bipyridine ligand and the aromatic ring ligand on another dinuclear polycation is 3.326Å, and there is a strong π-π stacking interaction between the clusters ( Figure 2 ). Crystal water and Cl − Ions fill in between clusters, playing the role of filling and neutralizing charges ( Figure 2 ). The powder X-ray diffraction results show that the polyvanadium oxycluster compound sample functionalized with nitrogen-containing ligands of the present invention is a pure substance.

[0035] The product in Example 1 was tested using infrared spectroscopy. Figure 3is the infrared spectrum of the polyvanadium oxygen cluster compound functionalized with nitrogen-containing ligands of the present invention, Figure 3 Display: Material is located at 971-949 cm −1 The spectral band is attributed to the V=O symmetric stretching vibration peak in the polyvanadium oxygen cluster, 1600-1442 cm −1 The strong absorption band at 3500-2992 cm −1 The absorption band is attributed to the characteristic vibration of crystal water molecules. Figure 4 The X-ray powder diffraction spectrum of the polyvanadium oxygen cluster compound functionalized with nitrogen-containing ligands of the present invention is shown in FIG. The measured spectrum is substantially consistent with the simulated spectrum, indicating that the compound of the present invention used for the study of catalytic properties is a pure substance.

[0036] Catalytic application test

[0037] Sulfide is a kind of environmental pollutant, which is oxidized to form sulfoxide or sulfone. Due to the various applications of sulfoxide and sulfone in organic synthesis reactions, the catalytic oxidation of sulfide has attracted increasing attention. With the help of a thermostatic automatic stirring organic reactor and a liquid-mass spectrometer, the catalytic oxidation activity of the compound of the present invention on several sulfides was tested at a temperature of 30°C using carbon dichloride (CH2Cl2) or acetonitrile (CH3CN) as solvent and tert-butyl hydroperoxide (TBHP) as oxidant. The details are as follows:

[0038] 0.0035 g (0.5% = mol% = 4.8 μmol) of the nitrogen-containing ligand functionalized polyvanadium oxygen cluster compound of the present invention was dissolved in 2 mL of CH2Cl2, and 180 μL (1 mmol) of TBHP was added. The catalytic oxidation reaction performance of the compound of the present invention was studied using three types of sulfides, namely toluene sulfide, alkyl sulfides (dipropyl sulfide, dibutyl sulfide, etc.) and thiophene (dibenzothiophene, benzothiophene, etc.) as substrates, and the results are presented in Tables 2 and 3 together with the experimental results of the raw materials 2,2'-bipyridine and potassium metavanadate.

[0039] As shown in Table 2, the amount of TBHP (entries 3-5), the amount of solvent (entries 1, 5), and the amount of catalyst (entries 1, 5, 6) are important factors affecting the product conversion rate. Under the optimal conditions, the compound of the present invention exhibits excellent catalytic performance in the reaction of converting toluene sulfide to toluene sulfoxide (entry 1, conversion rate = 94%, selectivity = 100%). Within 15 minutes, at a temperature of 30°C, alkyl sulfides such as dipropyl sulfide were converted into corresponding sulfoxide products with a conversion rate of 98% and a selectivity of 99%, indicating that the compound of the present invention has excellent catalytic efficiency in a relatively short time (entries 10-13). The experiment found that the conversion rate of alkyl aryl sulfide catalytic oxidation was higher than that of diphenyl sulfide (entries 1, 9). In addition, thiophene and benzothiophene are heterocyclic aromatic compounds with relatively stable properties and are difficult to catalytically oxidize. Using the compound of the present invention as a catalyst, TBHP as an oxidant, and CH2Cl2 medium at 30°C, dibenzothiophene and benzothiophene substrates were catalytically oxidized. Within two hours, the maximum conversion of dibenzothiophene was 42%, and the conversion of benzothiophene was 23%. Dibenzothiophene was mainly oxidized to the corresponding sulfoxide, and benzothiophene was mainly oxidized to the corresponding sulfone, with selectivities of 98% and 66%, respectively.

[0040] Table 2. Experimental results of the compounds of the present invention catalyzing the oxidation of various substrates

[0041]

[0042] Remark: a The conversion was determined by gas chromatography using dodecane as an internal standard. The products were identified by GC-MS (gas chromatography-mass spectrometry). b Entries 1 to 4: 1 mmol of substrate; 4.8 μmol of catalyst; 2 mL of CH2Cl2 solvent; reaction temperature 30 °C. c Entry 5: As above, but with 1.5 mL of CH2Cl2 solvent. d Reaction conditions for entries 6 and 7: as above, but with 3 μmol and 6 μmol of catalyst, respectively. e Reaction conditions for entry 8: as above, but with 2 mL CH3CN as solvent. f Reaction conditions for entries 9 to 15: 1 mmol of substrate; 4.8 μmol of catalyst; 2 mL of CH2Cl2; reaction temperature 30°C.

[0043] Most oxidation reactions have very low conversion rates when using raw materials as catalysts. As shown in Table 3, under the same conditions, the raw materials KVO3 and 2,2'-bipyridine have almost no catalytic performance in oxidizing sulfides. For example, when KVO3 is used as a catalyst to catalyze the oxidation of toluene sulfide, the conversion rate is only 4%; when 2,2'-bipyridine is used as a catalyst to catalyze the oxidation of toluene sulfide, the conversion rate is only 2% (see Table 3). The compounds of the present invention show excellent catalytic performance in the reaction of converting toluene sulfide into toluene sulfoxide (entry 1, conversion rate = 94%, selectivity = 100%). The nitrogen-containing ligand functionalized {V8} clusters and {V 14 The catalytic desulfurization performance of several compounds such as the cluster is far inferior to that of the compound of the present invention (see Zhang JL, Zhao QX, Cheng MY, Tungsten, 2023, doi:org / 10.1007 / s42864-022-00199-6; Cao JP, Xue YS, Li, NF, et al, J. Am. Chem. Soc., 2019, 141, 49, 19487−19497.). In contrast, the results show that the polyvanadium oxygen cluster compound functionalized with nitrogen-containing ligands of the present invention is a potential material for catalytic oxidation of sulfides, and the compound can be used as a homogeneous catalytic oxidation desulfurization material.

[0044] Table 3. Catalytic oxidation results of toluene sulfide under different catalysts a

[0045]

[0046] Remark: a Reaction conditions: 1 mmol substrate; 1 mmol TBHP; 4.8 μmol catalyst; 2 mL CH2Cl2; reaction temperature 30℃; reaction time 0.5 h; b Conversion determined based on gas chromatography analysis of initial substrate. Products were identified by GC-MS.

[0047] In summary, the polyvanadium oxycluster compound functionalized with nitrogen-containing ligands of the present invention has excellent performance in catalytic oxidation of various sulfides, indicating that it is a potential material for catalytic removal of sulfur-containing organic pollutants.

Claims

1. A polyvanadium oxycluster compound functionalized with a nitrogen-containing ligand, characterized in that: Its chemical formula is: [V IV 2O2(OH)2(H2O)2(C 10 H8N2)2]Cl2·8H2O, where C 10 H8N2) refers to 2,2'-bipyridine, which belongs to the monoclinic system. P twenty one / c Space group, unit cell parameters are: a=9.9679(2)Å, b=15.0712(4)Å, c=10.9311(2)Å; α=90°, β=108.1550(10)°, γ=90°.

2. The method for preparing the nitrogen-containing ligand functionalized polyvanadium oxycluster compound according to claim 1, characterized in that: The following steps are involved: The potassium metavanadate aqueous solution and the hydrazine hydrate solution are reacted at 80-95°C for more than 1 hour, and then 2,2'-bipyridine and β-alanine solid are added to the system while hot, and the pH is adjusted to 2.4-4.2 with dilute hydrochloric acid, and then reacted at 80-95°C for 2-6 hours, filtered while hot, and the filtrate is cooled and allowed to stand to precipitate crystals to obtain the product.

3. The method for preparing the polyvanadium oxycluster compound functionalized with nitrogen-containing ligands as claimed in claim 2, characterized in that: Dissolve potassium metavanadate solid in 80-95℃ hot water, add 80±10% hydrazine hydrate solution, and react for 1-3 hours.

4. The method for preparing the polyvanadium oxycluster compound functionalized with nitrogen-containing ligands as claimed in claim 2 or 3, characterized in that: The molar ratio of potassium metavanadate, hydrazine hydrate and 2,2'-bipyridine is 2:1:(1.34-0.42).

5. Use of the polyvanadium oxycluster compound functionalized with nitrogen-containing ligands as claimed in claim 1 in catalytic oxidation of sulfides.

6. Use of the nitrogen-containing ligand functionalized polyvanadium oxycluster compound as claimed in claim 5 in catalytic oxidation of sulfides, characterized in that: The sulfide is one or more of toluene sulfide, diphenyl sulfide, dipropyl sulfide, dibutyl sulfide, dibenzothiophene and benzothiophene.

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