Preparation and Application of a Pyridyl Anderson-Type Polyoxometalate Crystal and Its Composite Material

Abstract

The present invention relates to the preparation and application of a pyridyl Co / Ni-Anderson type polyoxometalate crystal and its composite material, belonging to the technical field of chemical synthesis. The crystal uses a pyridyl Anderson type polyoxometalate as a ligand, and metal cobalt ions or nickel ions are coordinated with the polyoxometalate ligand. Ru(bpy)<subgt;3< / subgt>Cl<subgt;2< / subgt> and the pyridyl Anderson type polyoxometalate crystal are added to acetonitrile, stirred for 12 to 18 hours and then left to stand. The supernatant is removed by centrifugation, and the precipitate is collected, washed, and a composite material of the pyridyl Anderson type polyoxometalate crystal is obtained. The composite material is used as a photocatalyst, which is environmentally friendly, efficient and reusable.

Description

Technical Field

[0001] The present invention relates to the preparation and application of a pyridyl Anderson-type polyoxometalate crystal and its composite material, belonging to the technical field of chemical synthesis. Background Art

[0002] Polyoxometalates (POMs) are a class of oxygen-containing polyacids composed of high oxidation states of early transition metal ions (such as V, Mo, W, etc.) coordinated by oxygen atoms to form a certain structure. Since the discovery of the first heteropolyacid metal salt in 1826 and the synthesis of the first heteropolyacid - 12-tungstosilicic acid in 1864, the development of polyacid chemistry has had a long history of nearly two centuries. With the popularization and maturity of single crystal X-ray diffraction technology, the atomic structure of polyoxometalates has been clarified, and six basic structures, namely Keggin (XM 12 O 40 ), Dawson (X2M 18 O 62 ), Anderson (XM6O 24 ), Waugh (XM9O 32 ), Silverton (XM 12 O 42 ), and Lindqvist (M6O 19 ), have been successively proposed. Anderson-type polyoxometalates are one of the six classic polyacid structures. They can form high-dimensional extended structures as flexible polydentate ligands with transition metals or rare earth elements and have potential application prospects. The Anderson polyacid modified by pyridyl TRIS (polydentate alkoxy organic ligand RC(CH2OH)3), [MnMo6O 18 -{(OCH2)3CC5H4N}2] 3- not only has rigid pyridyl groups capable of coordination at both ends, but its terminal oxygen can also provide a good coordination environment, enhancing the flexibility of the polyacid coordination mode and the diversity of the coordination framework structure. However, its synthesis steps are relatively cumbersome. Based on the pyridyl Anderson-type polyacid, it is extremely important to construct higher-dimensional polyacid compound structures by combining metal ions with polyacid ligands and explore their application values in the fields of catalysis, adsorption, etc. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide the preparation and application of a pyridyl Anderson-type polyoxometalate crystal and its composite material.

[0004] To achieve the above purpose, the technical solution of the present invention is as follows.

[0005] A pyridyl Anderson-type polyoxoacid crystal, wherein the crystal uses a pyridyl Anderson-type polyoxoacid as a ligand, and metal cobalt ions or nickel ions are coordinated with the polyoxoacid ligand; the crystallographic data is shown in Table 1:

[0006] Table 1

[0007]

[0008] A preparation method of the pyridyl Anderson-type polyoxoacid crystal described in the present invention, the method steps include:

[0009] When the metal ion is cobalt ion:

[0010] Dissolve 4-pyridin-4-ylbenzoic acid in a centrifuge tube containing N,N-dimethylformamide, then add a soluble cobalt salt and the Anderson polyoxoacid ligand {(TBA)3[MnMo6O 18 (TRI)2]}, after dissolution, add pyridine, heat the centrifuge tube at 80 - 110 °C for 9 - 12 h and then cool it to obtain a pyridyl Anderson-type polyoxoacid crystal in the centrifuge tube;

[0011] Among them, the dosage ratio of 4-pyridin-4-ylbenzoic acid, soluble cobalt salt, (TBA)3[MnMo6O 18 (TRI)2], and pyridine is 0.3 - 0.5 mmol: 0.2 - 0.3 mmol: 0.05 - 0.1 mmol: 20 - 30 μL;

[0012] When the metal ion is nickel ion:

[0013] Dissolve 1,3,5-tris(4-carboxyphenyl)benzene and a soluble nickel salt in a centrifuge tube containing N,N-dimethylformamide, then add the Anderson polyoxoacid ligand {(TBA)3[MnMo6O 18 (TRI)2]}, after generating a small amount of precipitate, add benzoic acid and tetrabutylammonium bromide, stir and dissolve until the solution is clear, transfer the solution to a quartz bottle and heat it at 80 - 110 °C for 9 - 12 h and then cool it to obtain a pyridyl Anderson-type polyoxoacid crystal in the quartz bottle;

[0014] Among them, the molar ratio of 1,3,5-tris(4-carboxyphenyl)benzene, soluble nickel salt, (TBA)3[MnMo6O 18 (TRI)2], benzoic acid and tetrabutylammonium bromide is 0.2 - 0.34: 0.2 - 0.34: 0.05 - 0.1: 0.3 - 0.4: 0.5 - 0.74.

[0015] Preferably, the soluble cobalt salt is nitrate or acetate; the soluble nickel salt is nitrate or acetate.

[0016] A composite material of the pyridyl-based Anderson-type polyoxoacid crystal of the present invention, the composite material is prepared by the following method, and the method steps include:

[0017] Add ruthenium (II) tris(2,2'-bipyridine) dichloride (Ru(bpy)3Cl2) and the pyridyl-based Anderson-type polyoxoacid crystal into acetonitrile, stir for 12 - 18 h and then let it stand, centrifuge to remove the supernatant, collect the precipitate, wash it, and obtain a composite material of the pyridyl-based Anderson-type polyoxoacid crystal;

[0018] Wherein, the molar ratio of Ru(bpy)3Cl2 to the polyoxoacid crystal is 1 - 2:1.

[0019] Preferably, the stirring rate is 300 - 600 r / min.

[0020] Preferably, in the composite material, the mass fraction of Ru is 4% - 7%.

[0021] An application of the composite material of the pyridyl-based Anderson-type polyoxoacid crystal of the present invention, the composite material is used as a photocatalyst.

[0022] Preferably, the composite material is used for the photocatalytic reaction of benzylamine substances or methyl phenyl sulfide substances.

[0023] Preferably, the benzylamine substance is or , R is an electron-donating group; the structural formula of the sulfide substance is , R' is an electron-donating group.

[0024] Preferably, R is -CH3, -OCH3, -tBu, -Br or -Cl; R' is -CH3, -COCH 3、 -NO2 or -Br.

[0025] Preferably, the composite material can be recycled for more than 5 times.

[0026] Beneficial effects

[0027] The present invention provides a pyridyl-based Anderson-type polyoxoacid crystal, the crystal uses the pyridyl-based Anderson-type polyoxoacid as a ligand, and metal cobalt ions or nickel ions coordinate with the polyoxoacid ligand. The polyoxoacid crystal has a novel structure, and after being loaded with ruthenium, it can be used as a catalyst in photocatalytic reactions.

[0028] The present invention provides a method for preparing a pyridyl Anderson-type polyoxometalate crystal. The polyoxometalate crystal is synthesized by a solvothermal method, and the reaction solvent must be N,N-dimethylformamide (DMF). When preparing the polyoxometalate crystal Co-1, 4-pyridin-4-ylbenzoic acid needs to be dissolved by ultrasonic first, and then a soluble cobalt salt is added. If the two are dissolved simultaneously, the synthesized crystal is smaller, which is not conducive to obtaining single crystal diffraction data. Then, a polyoxometalate ligand is added, and finally pyridine is added. When preparing the polyoxometalate crystal Ni-1, 1,3,5-tris(4-carboxyphenyl)benzene and a soluble nickel salt are dissolved in DMF, then a polyoxometalate ligand is added, and finally benzoic acid and tetrabutylammonium bromide are added. During the reaction process, the amounts of each substance must be strictly controlled. In addition, Co-1 needs to react in a centrifuge tube, and the crystal quality in a quartz bottle is poor; the reaction of Ni-1 is best in a quartz bottle, and no crystal can be obtained in a centrifuge tube.

[0029] The present invention provides a composite material of a pyridyl Anderson-type polyoxometalate crystal. The polyoxometalate crystal is compounded with Ru(bpy)3Cl2, and the obtained composite material can be used as a photocatalyst, which is environmentally friendly, efficient and reusable. Brief Description of the Drawings

[0030] Figure 1 It is the structural formula of the polyoxometalate ligand in the embodiment of the present invention.

[0031] Figure 2 It is the structural formula of the polyoxometalate crystal in Example 1 of the present invention.

[0032] Figure 3 It is the structural formula of the polyoxometalate crystal in Example 2 of the present invention.

[0033] Figure 4 It is the infrared spectrum diagram of the polyoxometalate crystal and its composite material in Examples 1-2 of the present invention.

[0034] Figure 5 It is the EDS element mapping diagram of the composite material in Examples 1-2 of the present invention; (a) is Ru(bpy)3@Co-1; (b) is Ru(bpy)3@Ni-1.

[0035] Figure 6 It is the X-ray photoelectron spectroscopy diagram of the composite material in Examples 1-2 of the present invention; (a) is the XPS full spectrum diagram of the composite material Ru(bpy)3@Co-1; (b) is the high-resolution spectrum diagram of Co2p; (c) is the high-resolution spectrum diagram of Ru3p; (d) is the XPS full spectrum diagram of the composite material Ru(bpy)3@Ni-1; (e) is the high-resolution spectrum diagram of Ni2p; (f) is the high-resolution spectrum diagram of Ru3d.

[0036] Figure 7 It is the photocatalytic performance diagram of the composite material in Example 4 of the present invention.

[0037] Figure 8 This is the X-ray diffraction pattern of the composite material described in Example 4 of the present invention before and after cycling. Detailed implementation manners

[0038] The present invention will be further described in detail below with reference to specific embodiments.

[0039] Example 1

[0040] The preparation of the pyridyl Anderson-type polyoxometalate crystal Co-1 is as follows:

[0041] Weigh 4-pyridine-4-ylbenzoic acid (2 mg, 0.5 mmol) into a 5 mL centrifuge tube, add N,N-dimethylformamide (1 mL), dissolve it by ultrasonic treatment, and then add cobalt(II) nitrate hexahydrate (3 mg, 0.21 mmol), and continue ultrasonic dissolution. Subsequently, add (TBA)3[MnMo6O 18 (TRI)2] (5 mg, 0.05 mmol, with the structure as shown in Figure 1 ), continue ultrasonic dissolution, add pyridine (30 µL), place the centrifuge tube in an 80 °C oven and react for 10 h. After the reaction, cool it to room temperature to obtain red rhombic crystals Co-1 that can be used for single crystal diffraction. Dry it at room temperature, and finally obtain 30 mg of the pyridyl Anderson-type polyoxometalate crystal Co-1. The yield of the polyoxometalate crystal is 45% (based on (TBA)3[MnMo6O 18 (TRI)2]).

[0042] The preparation method of the composite material Ru(bpy)3Cl2@Co- is as follows:

[0043] Weigh Ru(bpy)3Cl2 (0.6 mg) and Co-1 (5 mg) in a 5 mL centrifuge tube according to a molar ratio of 1:1, add 2 mL of acetonitrile, dissolve it by ultrasonic treatment, stir at low speed (350 r / min) at room temperature for 18 h, let it stand after the reaction, centrifuge to remove the supernatant, wash it repeatedly with acetonitrile until the supernatant is colorless, and dry it at room temperature to obtain green solid powder Ru(bpy)3Cl2@Co-1.

[0044] Example 2

[0045] The preparation of the pyridyl Anderson-type polyoxometalate crystal Ni-1:

[0046] Weigh 1,3,5-tris(4-carboxyphenyl)benzene (3.3 mg, 0.2 mmol) and nickel nitrate hexahydrate (5 mg, 0.34 mmol) separately into a 5 mL centrifuge tube, add N,N-dimethylformamide (1 mL), dissolve by ultrasonic treatment, and then add (TBA)3[MnMo6O 18 (TRI)2] (5 mg, 0.05 mmol), continue ultrasonic treatment to form a small amount of precipitate, successively add benzoic acid (2 mg, 0.33 mmol) and tetrabutylammonium bromide (12 mg, 0.74 mmol), stir to dissolve and the solution becomes clear. Transfer the clear solution into a 10 mL quartz bottle and react in an oven at 80 °C for 12 h. After the reaction, cool to room temperature to obtain green block crystals that can be used for single crystal diffraction. Dry in air at room temperature to finally obtain 94 mg of pyridyl Anderson-type polyacid crystal Ni-1 with a yield of 90% (based on (TBA)3[MnMo6O 18 (TRI)2]).

[0047] Preparation method of composite material Ru(bpy)3Cl2@Ni-1, the method steps are as follows:

[0048] Weigh Ru(bpy)3Cl2 and Ni-1 in a 5 mL centrifuge tube according to a molar ratio of 1:1, add 2 mL of acetonitrile, dissolve by ultrasonic treatment, and then stir at low speed (350 r / min) at room temperature for 18 h. After the reaction, let it stand, centrifuge to remove the supernatant, add acetonitrile to wash repeatedly until the supernatant is colorless, and dry in air at room temperature to obtain solid powder Ru(bpy)3Cl2@Ni-1.

[0049] Collect diffraction data on a Bruker SMART APEX II-CCD diffractometer, with the light source being graphite-monochromated molybdenum target Kα ray ( λ = 0.71073 Å), and the test temperature is 180 K. Under the conditions of 60 KV and 40 mA, find diffraction peaks and determine cell parameters through the XSCAN program. The diffraction data is collected by ω-2θ scanning mode, and all the scanned data is subjected to empirical absorption correction. The crystal structure is solved by the direct method using the OLEX 2 program, as Figures 2-3 shown; the crystallographic data is shown in Table 1.

[0050] Table 1

[0051]

[0052] Use Thermo IS 5 to perform infrared spectroscopy tests on Anderson-type polyacid crystals and their composite materials, the test range: 2500 - 500 cm -1 , as Figure 4As shown, the results indicate that the infrared spectra of Co-1 and Ni-1 exhibit similar characteristic bands of the Anderson-POM structure. The absorption peaks at 1061, 944, 921, 663, 566 cm −1 are the characteristic absorption peaks of the polyoxoacid ligand [MnMo6O 18 (TRI)2] 3- , while the disappearance of the absorption peaks at 1648, 1383, 1110 cm −1 in the infrared spectra of Ru(bpy)3@Ni-1 / Co-1 indicates that [Ru(bpy)3] 2+ is adsorbed onto the surface of the Ni-1 / Co-1 framework.

[0053] The EDS elemental mapping images of the composite materials Ru(bpy)3@Ni-1 and Ru(bpy)3@Co-1 are as shown in Figure 5 . The images show the metal elements Mn, Mo, Ni, and Co belonging to the polyoxoacid in the framework, as well as the element Ru of the photosensitizer, indicating that [Ru(bpy)3] 2+ is uniformly dispersed on the surfaces of the two frameworks.

[0054] The composite materials Ru(bpy)3@Co-1 and Ru(bpy)3@Ni-1 were characterized using a 5000 Versaprobe III X-ray photoelectron spectrometer. The results show that elements such as C, O, N, Mn, Mo, Co, and Ru are present in Ru(bpy)3@Co-1 / Ni-① (Figs. 6(a) and (d)). The peaks at 781.29 eV and 797.06 eV in the high-resolution spectra of Co2p / Ni2p (Figs. 6(b) and (e)) correspond to the characteristic peaks of Co2p 3 / 2 and Co2p 1 / 2 respectively; the characteristic peaks of Ni2p 3 / 2 and Ni2p 1 / 2 appear at 855.80 eV and 874.69 eV respectively; the peaks at 284.40 eV and 280.30 eV in the high-resolution spectrum of Ru 3p (Fig. 6(c)) correspond to the characteristic peaks of Ru3p 3 / 2 and Ru3p 5 / 2 respectively. The peaks at 484.03 eV and 461.76 eV in the high-resolution spectrum of Ru3d (Fig. 6(f)) correspond to the characteristic peaks of Ru3d 1 / 2 and Ru3d 3 / 2 respectively. Semi-quantitative analysis was performed on Ru(bpy)3@Co-1 and Ru(bpy)3@Ni-1, and the Ru contents were 6.8% and 4.9% respectively.

[0055] Example 3

[0056] Using benzylamine as a model substrate, Ni-1 and Co-1 and their composites loaded with [Ru(bpy)3] 2+ were used as catalysts for the photocatalytic oxidative coupling experiment of benzylamine.

[0057] Benzylamine (0.1 mmol) and the catalyst (1 mg) were added to 5 mL of acetonitrile in a 5 mL quartz bottle. Then, in an air atmosphere at room temperature, a multi-channel photoreaction system was used, and the reaction vessel was irradiated with a 10 W LED light source (λ>400 nm). Finally, the solution after the photocatalytic reaction was monitored using a gas chromatograph (GC-2014C Shimadzu).

[0058] There was no conversion of benzylamine by Ni-1 and Co-1 within 1 h, but the photocatalytic performance of the catalyst after loading [Ru(bpy)3] 2+ was greatly improved. Ru(bpy)3@Co-1 completely oxidized benzylamine within 1 h with 100% imine selectivity, while the conversion rate was only 23% when using the Ru(bpy)3@Ni-1 catalyst (Table 2).

[0059] Table 2

[0060]

[0061] The reaction equation is:

[0062] .

[0063] Due to the good photocatalytic benzylamine oxidation performance of Ru(bpy)3@Co-1, other benzylamine substrates were explored. When electron-donating groups (-CH3, -OCH3, -tBu, -Br, -Cl) were introduced at the para position of benzylamine, there was no effect on the oxidation efficiency of benzylamine, and they were all completely converted to the corresponding imines within 1 h (Table 3, entries 1-4). However, when electron-withdrawing groups were introduced at the para position, as the electron-withdrawing ability of the groups increased (-Br < -Cl < -F), the conversion rate of benzylamine gradually decreased, and the conversion rate of benzylamine with a strong electron-withdrawing group (such as -F) was only 4% (Table 3, entries 5-7), indicating that benzylamine with an electron-withdrawing group at the para position was more difficult to be photocatalytically oxidized, and the stronger the electron-withdrawing ability of the group, the less likely it was to be oxidized.

[0064] Table 3

[0065]

[0066] Example 4

[0067] Using Ru(bpy)3@Co-1 as the catalyst and methyl phenyl sulfide as the substrate, a cyclic test was carried out in a 5 mL methanol / water mixed solvent (volume ratio 1:1). After each reaction, the solution was centrifuged, and the catalyst was washed three times with methanol and once with diethyl ether, and then dried under vacuum for the next cycle. After each catalytic reaction, the solution was colorless, and irradiating the reaction solution with a blue light lamp did not produce fluorescence ([Ru(bpy)3] 2+ ions irradiated with a blue light lamp in the solution have red fluorescence, indicating that there is no [Ru(bpy)3] 2+ leaching after the reaction. As can be seen from Figure 7 , the photocatalytic performance has been maintained at a high level. The powder X-ray diffraction pattern ( Figure 8 ) shows that the positions of the diffraction peaks of Ru(bpy)3@Co-1 remain unchanged after 5 cycles of use, indicating that the framework structure of this photocatalyst is stable during the catalytic cycle reaction.

[0068] In summary, the invention includes but is not limited to the above embodiments. Any equivalent replacement or partial improvement made under the spirit and principle of the present invention will be regarded as within the protection scope of the present invention.

Claims

1. A composite material of pyridyl Anderson-type polyacid crystals, characterized in that: The composite material is prepared by the following method, which comprises the following steps: 4-Pyridin-4-ylbenzoic acid was dissolved in a centrifuge tube containing N,N-dimethylformamide, and then soluble cobalt salt and polyacid ligand (TBA)3[MnMo6O 18 After the (TRI)2] is dissolved, pyridine is added, and the centrifuge tube is heated at 80-110°C for 9-12 hours and then cooled to obtain pyridyl Anderson-type polyacid crystals in the centrifuge tube; wherein TBA is tetra-n-butylammonium, TRI is 2-hydroxymethyl-2-(4-pyridine)-1,3-propanediol with three protons removed, 4-pyridin-4-ylbenzoic acid, soluble cobalt salt, (TBA)3[MnMo6O 18 The ratio of (TRI)2] and pyridine is 0.3-0.5 mmol: 0.2-0.3 mmol: 0.05-0.1 mmol: 20-30 μL; Adding Ru(bpy)3Cl2 and the pyridyl Anderson-type polyacid crystals to acetonitrile, stirring for 12 to 18 hours, then allowing to stand, centrifuging to remove the supernatant, collecting the precipitate and washing it to obtain a composite material of the pyridyl Anderson-type polyacid crystals; wherein the molar ratio of Ru(bpy)3Cl2 to the polyacid crystals is 1 to 2:1; The polyacid crystals use pyridyl Anderson-type polyacids as ligands, and metal cobalt ions are coordinated with the polyacid ligands; the crystallographic data are shown in the following table:

2. The composite material of a pyridyl Anderson-type polyacid crystal according to claim 1, characterized in that: The soluble cobalt salt is nitrate or acetate.

3. The composite material of a pyridyl Anderson-type polyacid crystal according to claim 1, characterized in that: The stirring rate is 300-600 r / min.

4. The composite material of a pyridyl Anderson-type polyacid crystal according to claim 1, characterized in that: In the composite material, the mass fraction of Ru is 4% to 7%.

5. Use of the composite material of the pyridyl Anderson-type polyacid crystal according to any one of claims 1 to 4, characterized in that: The composite material is used as a photocatalyst for the photocatalytic reaction of benzylamine substances or methyl phenyl sulfide substances; The benzylamine substance is R is -CH3, -OCH3, -tBu, -Br or -Cl; the structural formula of the sulfide substance is R' is -CH3, -COCH3, -NO2 or -Br.

6. The use of a composite material of a pyridyl Anderson-type polyacid crystal according to claim 5, characterized in that: The composite material can be recycled more than 5 times.

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