Arsenic-based polyoxotungstate material, preparation method and application

Abstract

The invention discloses an arsenic-based polytungstate material as well as a preparation method and application thereof, and belongs to the field of polyacid-based advanced functional materials. The invention provides a polyoxotungstate material constructed by Cu-Eu dissimilar metals based on arsenic heteroatoms, the chemical formula of the polyoxotungstate material is NaH3 [Cu (en) 2 (H2O)] [{Cu (en) 2} {Cu (en) 2} 1.5 Eu (AsW11O39) 2]. 3.5 H2O, and the polyoxotungstate material belongs to a triclinic system and a P-1 space group. The arsenic-based polyoxotungstate material is simple in synthesis step and low in cost, can present better catalytic degradation activity on an antibiotic tetracycline hydrochloride in a dark and normal-temperature environment without the assistance of any auxiliary agent, and after the catalytic reaction is completed, the structure of the catalyst is still kept complete, so that the arsenic-based polyoxotungstate material is suitable for industrial production. Potential application prospects are realized in the aspect of antibiotic pollution treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of polyoxometalate-based advanced functional materials, and particularly relates to an arsenic-based polyoxotungstate material, a preparation method and an application thereof. Background Art

[0002] Antibiotics have been widely used in human medicine, livestock and poultry, and aquaculture. Residues of antibiotics have often been reported in environmental media (water bodies, sediments and soils). At present, the pollution situation of antibiotics is relatively severe. As a type of "new pollutant", antibiotics have the characteristics of strong stability, poor biodegradability, high persistence and good solubility. Some conventional treatment processes are difficult to eliminate them. Therefore, it is still a great challenge to efficiently remove the residues of antibiotics in the water environment.

[0003] Currently, the common methods for removing antibiotics mainly include physical adsorption, chemical oxidation, biodegradation and advanced oxidation processes, etc. Each of them has its own advantages and disadvantages. Therefore, it is urgent to explore more green, convenient, environmentally friendly, economical and efficient antibiotic pollutant removal technologies.

[0004] Polyoxometalate materials are a class of nano- or micro-scale polynuclear metal-oxygen clusters with special structures formed by the polymerization of high oxidation state ions (Mo Ⅵ , W Ⅵ , V Ⅳ,Ⅴ , Nb Ⅴ , Ta Ⅴ ) of pre-transition metals with oxygen. They usually have characteristics such as reversible multi-electron redox and strong Lewis acidity and basicity, and can exhibit physical and chemical properties quite different from those of traditional transition metal oxides. At present, there has been no report on the application of pure polyoxometalate materials in the degradation of the new pollutant antibiotics. Summary of the Invention

[0005] The purpose of the present invention is to prepare an arsenic-based polyoxotungstate material that can efficiently degrade the new pollutant antibiotics by using a synthesis strategy of stepwise assembly with simple and easily available reaction raw materials.

[0006] To achieve the above objectives, the technical solutions adopted by the present invention are as follows:

[0007] A preparation method of an arsenic-based polyoxotungstate material, comprising the following steps:

[0008] S1: Disperse a certain amount of polyacid precursor Na3[α-AsW 12 O 40 , metal salts CuCl2·2H2O and EuCl3·6H2O, and ethylenediamine ligand in distilled water, and stir and react at room temperature;

[0009] S2: While continuously stirring, adjust the pH with an acid solution;

[0010] S3: After continuing to stir for a period of time, raise the temperature for a high-temperature reaction;

[0011] S4: After the high-temperature reaction ends, cool to room temperature to obtain purple block crystals.

[0012] In one embodiment of the present invention, in S1, the molar ratio of Na3[α-AsW 12 O 40 , CuCl2·2H2O, and EuCl3·6H2O is 0.15:0.6:(0.25 - 0.3)

[0013] In one embodiment of the present invention, in S1, the dosage conditions of CuCl2·2H2O and the ethylenediamine ligand are 0.6 mmol:(0.08 - 0.12) mL.

[0014] In one embodiment of the present invention, in S1, the stirring reaction time is 1 h.

[0015] In one embodiment of the present invention, in S2, the acid solution can specifically be an HCl solution.

[0016] In one embodiment of the present invention, in S2, the pH is 3.8 - 4.2.

[0017] In one embodiment of the present invention, in S3, the continued stirring time is 30 min.

[0018] In one embodiment of the present invention, in S3, the high-temperature reaction conditions are to react at 140 - 160 °C for 3 - 4 days.

[0019] In one embodiment of the present invention, the preparation method of the above-mentioned arsenic-based polyoxotungstate material specifically includes the following steps:

[0020] S1: Put 0.15 mmol of Na3[α-AsW 12 O 40 polyacid precursor, 0.6 mmol of CuCl2·2H2O, 0.28 mmol of EuCl3·6H2O, and 0.1 mL of ethylenediamine ligand into a polytetrafluoroethylene inner container containing 10 mL of distilled water, and stir at room temperature for 1 h;

[0021] S2: While continuously stirring, adjust the pH value of the suspension in step 1 to 3.95 with a 4 mol / L HCl solution;

[0022] S3: After continuing to stir for 30 min, put the reaction kettle into a forced-air drying oven and heat and react at 150 °C for 3 days;

[0023] S4: After cooling to room temperature, purple bulk crystals are obtained in a polytetrafluoroethylene inner container.

[0024] Based on the above method, the present invention provides an arsenic-based polyoxotungstate material with a novel structure.

[0025] In one embodiment of the present invention, the chemical formula of the above arsenic-based polyoxotungstate material is NaH3[Cu(en)2(H2O)][{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2]·3.5H2O; where en refers to ethylenediamine NH2CH2CH2NH2.

[0026] The obtained arsenic-based polyoxotungstate material belongs to the triclinic system, space group P-1, and its unit cell parameters are α = 114.315(2)°, β = 90.651(2)°, γ = 94.210(2)°.

[0027] The obtained arsenic-based polyoxotungstate material is composed of [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- polyanion, 1 Na + ion, 3 H + ions for charge balance, 1 free [Cu(en)2(H2O)] 2+ ion and 3.5 water molecules.

[0028] The polyanion [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- in the obtained arsenic-based polyoxotungstate material includes 1 {Eu(AsW 11 O 39 )2} 11- anion, 1.5 six-coordinate [Cu(en)2] 2+ cations and 1 five-coordinate [Cu(en)2] 2+ cation. Each six-coordinate [Cu(en)2] 1.5 cation in [{Cu(en)2}{Cu(en)2} 11 O 39 )2] 6- polyanion is coordinated with two adjacent {Eu(AsW 2+ O 11 O 39)2} 11- The terminal oxygen atoms of the anion are connected by two Cu-OW bonds, and the adjacent {Eu(AsW 11 O 39 )2} 11- The anion is hexacoordinated by a bridge [Cu1(en)2] 2+ , [Cu3(en)2] 2+ and [Cu5(en)2] 2+ Connected into a 2D structure. 1.5 Eu(AsW 11 O 39 )2] 6- Pentacoordinated [Cu(en)2] in polyanion 2+ The cation is bonded to a {Eu(AsW 11 O 39 )2} 11- The terminal oxygen atoms of the anion are connected.

[0029] The obtained arsenic-based polytungstate material {Eu(AsW 11 O 39 )2} 11- The anion is composed of two monovacant Keggin-type [As W 11 O 39 ] 7- Anion sandwiches an eight-coordinated rare earth Eu Ⅲ formed.

[0030] The eight-coordinated Eu in the obtained arsenic-based polytungstate material Ⅲ Located in [AsW 11 O 39 ] 7- The vacancy position of the anion is related to the two [AsW 11 O 39 ] 7- The eight oxygen atoms (O45, O27, O50, O22, O70, O43, O74, O16) at the vacant positions of the anion are coordinated to adopt a distorted tetragonal anti-prismatic geometric configuration.

[0031] The five crystallographically independent Cu ions in the resulting arsenic-based polytungstate material exhibit two different coordination geometries:

[0032] [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- Hexacoordinated [Cu1(en)2] in polyanion 2+ , [Cu3(en)2]2+ and [Cu5(en)2] 2+ ions both adopt an octahedral geometry and coordinate with the 4 N atoms provided by two ethylenediamines and two terminal O atoms provided by two adjacent {Eu(AsW 11 O 39 )2} 11- anions (specifically, the hexacoordinate bridge [Cu1(en)2] 2+ coordinates with O59 from two adjacent {Eu(AsW 11 O 39 )2}, [Cu3(en)2] 11- coordinates with O26 from two adjacent {Eu(AsW 2+ O 11 O 39 )2}, and [Cu5(en)2] 11- coordinates with O73 from two adjacent {Eu(AsW 2+ O 11 O 39 )2}); 11- coordinates with O73 from two adjacent {Eu(AsW

[0033] [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- In the polyanion, the pentacoordinate [Cu(en)2] 2+ ion adopts a square pyramidal coordination geometry and coordinates with the 4 N atoms provided by two ethylenediamines and 1 terminal O atom (O25) provided by {Eu(AsW 11 O 39 )2} 11- anion;

[0034] The free {Cu(en)2(H2O)} 2+ ion adopts a square pyramidal coordination geometry and coordinates with the four N atoms from two ethylenediamines and a water molecule.

[0035] In the obtained arseno-based polyoxotungstate material, the valences of As, Eu, Cu, and W are +5, +3, +2, and +6, respectively.

[0036] The present invention also provides the application of the above-mentioned arseno-based polyoxotungstate material in the field of catalytic degradation of organic pollutant antibiotics.

[0037] The present invention also provides the application of the above-mentioned arseno-based polyoxotungstate material as a catalyst in the catalytic degradation of the organic pollutant antibiotic tetracycline hydrochloride.

[0038] The arseno-based polyoxotungstate material provided by the present invention can exhibit good catalytic degradation activity for the antibiotic tetracycline hydrochloride under very mild conditions, and thus has broad application prospects in the field of degrading new pollutants antibiotics. It is found through experiments in the present invention that: even under the conditions of normal temperature, normal pressure, darkness and without the assistance of any additives, the arseno-based polyoxotungstate material can achieve efficient catalytic degradation of the antibiotic tetracycline hydrochloride; and after the catalytic reaction is completed, the catalyst after catalysis is centrifuged and separated, and infrared spectroscopy test and X-ray powder diffraction test show that the structure of the catalyst before and after catalysis remains intact and is not damaged.

[0039] The present invention provides a preparation method of an arseno-based polyoxotungstate material and its application as a catalyst for catalytic degradation of the new pollutant antibiotic tetracycline hydrochloride. Compared with the prior art, the present invention has the following advantages:

[0040] The organic-inorganic composite polyoxotungstate material of the present invention not only has the functional characteristics of inorganic and organic components, but also exhibits the multi-functional characteristics carried by different metal ions, and has shown strong functional advantages in the fields of catalysis, magnetism, electricity, biology, etc.

[0041] The arseno-based polyoxotungstate material synthesized in the present invention adopts a step-by-step assembly synthesis strategy, the preparation method is simple, the product yield and purity are relatively high, and its molecular structure can be accurately determined by X-ray single crystal diffraction technology.

[0042] As a heterogeneous catalyst in the application of catalytic degradation of the new pollutant antibiotic tetracycline hydrochloride, the arseno-based polyoxotungstate material provided by the present invention can exhibit good catalytic degradation activity even under the conditions of darkness, normal temperature environment and without the assistance of any additives, and the catalytic stability of the arseno-based polyoxotungstate material is good, and it has potential application prospects in the treatment of new pollutants. Brief Description of the Drawings

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0044] Figure 1 It is the polyanion structure diagram of the arseno-based polyoxotungstate material obtained in Example 1 of the present invention.

[0045] Figure 2 It is the 2D structure diagram of the arseno-based polyoxotungstate material obtained in Example 1 of the present invention.

[0046] Figure 3 It is for the arseno-based polyoxotungstate material obtained in Example 1 of the present invention {Eu(AsW 11 O39 )2} 11- Structure diagram of the structural unit.

[0047] Figure 4 Coordination mode of the rare earth ion Eu in the arsenic-based polyoxotungstate material obtained in Example 1 of the present invention Ⅲ Coordination mode.

[0048] Figure 5 Coordination mode of the Cu ion in the arsenic-based polyoxotungstate material obtained in Example 1 of the present invention

[0049] Figure 6 Infrared spectrum of the arsenic-based polyoxotungstate materials obtained in Examples 1-3 of the present invention (Curve 1 is the infrared spectrum of the compound obtained in Example 1, Curve 2 is the infrared spectrum of the compound obtained in Example 2, and Curve 3 is the infrared spectrum of the compound obtained in Example 3).

[0050] Figure 7 X-ray powder diffraction pattern of the arsenic-based polyoxotungstate materials obtained in Examples 1-3 of the present invention (including the theoretical values fitted according to X-ray single crystal diffraction, the X-ray powder diffraction pattern of the compound obtained in Example 1, the X-ray powder diffraction pattern of the compound obtained in Example 2, and the X-ray powder diffraction pattern of the compound obtained in Example 3).

[0051] Figure 8 Ultraviolet-visible absorption spectrum of the arsenic-based polyoxotungstate material obtained in Example 1 of the present invention for catalytic degradation of tetracycline hydrochloride (from top to bottom, the curves are: degradation for 0 h, dark stirring for 0.5 h, 1.5 h, 2.5 h, 3.5 h, 4.5 h, 5.5 h, 6.5 h after the catalyst is added to the system).

[0052] Figure 9 For Na3[α-AsW in Comparative Example 1 of the present invention 12 O 40 as a catalyst for the catalytic degradation of tetracycline hydrochloride, the ultraviolet-visible absorption spectrum (from top to bottom, the curves are: degradation for 0 h, dark stirring for 0.5 h, 1.5 h, 2.5 h, 3.5 h, 4.5 h, 5.5 h, 6.5 h after the catalyst is added to the system).

[0053] Figure 10 Ultraviolet-visible absorption spectrum of Na2WO4·2H2O as a catalyst for the catalytic degradation of tetracycline hydrochloride in Comparative Example 1 of the present invention (from top to bottom, the curves are: degradation for 0 h, dark stirring for 0.5 h, 1.5 h, 2.5 h, 3.5 h, 4.5 h, 5.5 h, 6.5 h after the catalyst is added to the system).

[0054] Figure 11UV-Vis absorption spectra of the catalytic degradation of tetracycline hydrochloride by EuCl3·6H2O as a catalyst in Comparative Example 1 (from top to bottom, the curves are: degradation for 0 h, dark stirring for 0.5 h, 1.5 h, 2.5 h, 3.5 h, 4.5 h, 5.5 h, 6.5 h after the catalyst is added to the system).

[0055] Figure 12 UV-Vis absorption spectra of the catalytic degradation of tetracycline hydrochloride by CuCl2·2H2O as a catalyst in Comparative Example 1 (from top to bottom, the curves are: degradation for 0 h, dark stirring for 0.5 h, 1.5 h, 2.5 h, 3.5 h, 4.5 h, 5.5 h, 6.5 h after the catalyst is added to the system).

[0056] Figure 13 Infrared spectrum after the catalytic degradation experiment of the arsenic-based polyoxotungstate material in Example 5 of the present invention.

[0057] Figure 14 X-ray powder diffraction pattern after the catalytic degradation experiment of the arsenic-based polyoxotungstate material in Example 5 of the present invention. Detailed implementation mode

[0058] The present invention will be further described and illustrated through specific examples below. It should be understood that the examples described in this specification are only for explaining the present invention, and the protection scope of the present invention is not limited thereto.

[0059] Example 1: Preparation of an arsenic-based polyoxotungstate material

[0060] The chemical formula of the arsenic-based polyoxotungstate material is: NaH3[Cu(en)2(H2O)][{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2]·3.5H2O.

[0061] The above arsenic-based polyoxotungstate material is obtained by a stepwise assembly strategy, and its specific preparation method involves the following steps:

[0062] Synthesize the precursor Na3[α-AsW 12 O 40 according to the conventional method in the art (specifically, see the reference Rocchiccioli-Deltcheff.C, Fournier.M, Franck.R, Thouvenot.R. Inorg.Chem. 1983, 22, 207–216);

[0063] Dissolve 0.15 mmol of Na3[α-AsW 12 O 400.6 mmol of CuCl2·2H2O, 0.28 mmol of EuCl3·6H2O, and 0.1 mL of ethylenediamine ligand were added to a polytetrafluoroethylene inner container containing 10 mL of distilled water, and stirred at room temperature for 1 h. Then, with continuous stirring, the pH value of the resulting suspension was adjusted to 3.95 with 4 mol / L HCl solution, and after continuous stirring for 30 min, the reaction kettle was placed in a forced-air drying oven and reacted at a high temperature of 150 °C for 3 days. After cooling to room temperature, purple block crystals were obtained in the polytetrafluoroethylene inner container, which was the target product, the arseno-polyoxotungstate material.

[0064] Example 2: Preparation of an arseno-polyoxotungstate material

[0065] The chemical formula of the arseno-polyoxotungstate material is: NaH3[Cu(en)2(H2O)][{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2]·3.5H2O.

[0066] The above arseno-polyoxotungstate material was obtained by a stepwise assembly strategy, and its specific preparation method involves the following steps:

[0067] The precursor Na3[α-AsW 12 O 40 was synthesized by the conventional method in the art (specifically, see the reference Rocchiccioli-Deltcheff.C, Fournier.M, Franck.R, Thouvenot.R. Inorg.Chem. 1983, 22, 207–216);

[0068] 0.15 mmol of Na3[α-AsW 12 O 40 polyoxotungstate precursor, 0.6 mmol of CuCl2·2H2O, 0.28 mmol of EuCl3·6H2O, and 0.1 mL of ethylenediamine ligand were added to a polytetrafluoroethylene inner container containing 10 mL of distilled water, and stirred at room temperature for 1 h. Then, with continuous stirring, the pH value of the resulting suspension was adjusted to 3.95 with 4 mol / L HCl solution, and after continuous stirring for 30 min, the reaction kettle was placed in a forced-air drying oven and reacted at a high temperature of 160 °C for 4 days. After cooling to room temperature, purple block crystals were obtained in the polytetrafluoroethylene inner container, which was the target product, the arseno-polyoxotungstate material.

[0069] Example 3: Preparation of an arseno-polyoxotungstate material

[0070] The chemical formula of the arsenic-based polyoxotungstate material is: NaH3[Cu(en)2(H2O)][{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2]·3.5H2O.

[0071] The above arsenic-based polyoxotungstate material is obtained by a stepwise assembly strategy, and its specific preparation method involves the following steps:

[0072] Synthesize the precursor Na3[α-AsW 12 O 40 according to the conventional method in the art (specifically, see the reference Rocchiccioli-Deltcheff.C, Fournier.M, Franck.R, Thouvenot.R. Inorg.Chem. 1983, 22, 207–216);

[0073] Put 0.15 mmol of the Na3[α-AsW 12 O 40 polyacid precursor, 0.6 mmol of CuCl2·2H2O, 0.25 mmol of EuCl3·6H2O, and 0.09 mL of ethylenediamine ligand into a polytetrafluoroethylene inner liner containing 10 mL of distilled water, and stir at room temperature for 1 h; then, while continuously stirring, adjust the pH value of the obtained suspension to 4.20 with a 4 mol / L HCl solution, continue to stir for 30 min, then place the reaction kettle in a forced-air drying oven and react at a high temperature of 150 °C for 3 days. After cooling to room temperature, purple block crystals are obtained in the polytetrafluoroethylene inner liner, which is the target arsenic-based polyoxotungstate material.

[0074] The present invention has determined and characterized the crystal structure of the target arsenic-based polyoxotungstate material prepared in the above Example 1, and the crystallographic data of this compound are listed in Table 1.

[0075] Table 1: Crystallographic data of the target compound

[0076]

[0077]

[0078] The results of X-ray single crystal diffraction show that the obtained arsenic-based polyoxotungstate target product NaH3[Cu(en)2(H2O)][{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2]·3.5H2O belongs to the triclinic system, P-1 space group, and its unit cell parameters are α = 114.315(2)°, β = 90.651(2)°, γ = 94.210(2)°. Its molecular structural unit consists of [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- polyanion, 1 Na + ion, 3 H + ions for charge balance, 1 free [Cu(en)2(H2O)] 2+ ion and 3.5 water molecules. The polyanion [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- ( Figure 1 ) includes 1 {Eu(AsW 11 O 39 )2} 11- anion, 1.5 six - coordinated [Cu(en)2] 2+ cations and 1 five - coordinated [Cu(en)2] 2+ cation. In [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- each six - coordinated [Cu(en)2] 2+ cation in the polyanion is connected to the terminal oxygen atoms of two adjacent {Eu(AsW 11 O 39 )2} 11- anions through two Cu - O - W bonds. Adjacent {Eu(AsW 11 O 39 )2} 11- anions are connected into a 2D structure ( 2+ , [Cu3(en)2] 2+ and [Cu5(en)2] 2+ ) by six - coordinated bridging [Cu1(en)2] Figure 2 . In [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- the five - coordinated [Cu(en)2] 2+ cation in the polyanion is connected to a {Eu(AsW 11 O 39 )2} 11-is connected to the terminal oxygen atom of the anion. {Eu(AsW 11 O 39 )2} 11- The anion is composed of two mono - vacant Keggin - type [AsW 11 O 39 7- The anion sandwiches an eight - coordinated rare - earth Eu Ⅲ to form ( Figure 3 ) and this eight - coordinated Eu Ⅲ is located at the vacant position of the [AsW 11 O 39 7- anion. It coordinates with 8 oxygen atoms (O45, O27, O50, O22, O70, O43, O74, O16) at the vacant positions of two [AsW 11 O 39 7- anions, adopting a distorted square antiprismatic geometry ( Figure 4 ).

[0079] Five crystallographically independent Cu ions in this compound exhibit two different coordination geometries ( Figure 5 ). [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- The six - coordinated [Cu1(en)2] 2+ , [Cu3(en)2] 2+ and [Cu5(en)2] 2+ ions in the polyanion all adopt an octahedral geometry, coordinating with 4 N atoms provided by two ethylenediamines and two terminal O atoms provided by two adjacent {Eu(AsW 11 O 39 )2} 11- anions respectively; specifically, the six - coordinated bridging [Cu1(en)2] 2+ coordinates with two O59 from two adjacent {Eu(AsW 11 O 39 )2} 11- , [Cu3(en)2] 2+ coordinates with two O26 from two adjacent {Eu(AsW 11 O 39 )2} 11- , [Cu5(en)2] 2+ coordinates with two O atoms from two adjacent {Eu(AsW 11 O 39 )2} 11- ​​​O73 coordination. [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- Pentacoordinated [Cu4(en)2] in polyanion 2+ The ion adopts a tetrahedral coordination configuration, with four N atoms provided by two ethylenediamines and {Eu(AsW 11 O 39 )2} 11- The anion provides coordination to one terminal O atom; specifically, the pentacoordinated [Cu4(en)2] 2+ ions and [AsW 11 O 39 ] 7- O25 in the anion is coordinated. Free {Cu2(en)2(H2O)} 2+ The ion adopts a tetrahedral coordination configuration, coordinated with four nitrogen atoms from two ethylenediamine atoms and one water molecule. Bond valence calculations show that the valences of As, Eu, Cu and W in the compound are +5, +3, +2 and +6, respectively.

[0080] The infrared spectrum ( Figure 6 ) and X-ray powder diffraction ( Figure 7 ) were analyzed, such as Figure 6 As shown, the saturated Keggin type [AsW 12 O 40 ] 3- The As-O bond vibration region in the precursor is at 911 cm -1 Since the target compound formed a single-vacancy Keggin anion substituted by Eu, the {AsO4} tetrahedron in the structure was deformed, causing the As-O bond vibration peak to red-shift to 1032 cm in the infrared spectrum of the target compound. -1 Nearby; 1000-600cm -1 The peaks in the range are characteristic vibration peaks of polyacid anions, among which 998cm -1 It is the characteristic stretching vibration peak of W=O, 932cm -1 and 859cm -1 The peak at 1589 cm-1 can be attributed to the symmetric stretching vibration and asymmetric stretching vibration of WOW. The vibration region of -NH2 and -CH2 is located at 1589 cm-1. -1 and 1352cm -1 Nearby, the stretching and bending vibrations of HO in crystal water and coordinated water appear at 3436 cm – 1 and 1626cm – 1Position. In Figure 7 By comparison, it is found that the X-ray powder diffraction pattern measured experimentally is in good agreement with the theoretical pattern fitted by X-ray powder diffraction, indicating that the compound used in the test is pure. That is, the target products of arseno-polyoxotungstates with the same composition and morphology, NaH3[Cu(en)2(H2O)][{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2]·3.5H2O, were obtained in Examples 1-3.

[0081] Example 4: Performance test of arseno-polyoxotungstate material for catalytic degradation of tetracycline hydrochloride

[0082] Specifically, it includes the following steps:

[0083] (1) Prepare a tetracycline hydrochloride solution with a concentration of 25 mg·L -1 and store it in a dark environment.

[0084] (2) Grind the crystalline arseno-polyoxotungstate obtained in Example 1 sufficiently to obtain a powdered sample.

[0085] (3) Weigh 19 mg of the powdered arseno-polyoxotungstate and add it to 30 mL of the tetracycline hydrochloride solution.

[0086] (4) Stir for 30 min under dark conditions to allow the powdered arseno-polyoxotungstate material to come into full contact with the tetracycline hydrochloride solution.

[0087] (5) After centrifuging 3 mL of the sample in (4), take the supernatant and detect it with a UV-visible spectrophotometer.

[0088] (6) Then, under continuous stirring, take 3 mL of the sample in (4) every 1 h, centrifuge it, take the supernatant and detect it with a UV-visible spectrophotometer. It can be seen from Figure 8 that the absorbance of tetracycline hydrochloride gradually decreases with the prolongation of the degradation time, indicating that the amount of tetracycline hydrochloride in the solution is getting less and less. When sampling at 6.5 h in the system, the degradation efficiency reaches 86%.

[0089] Example 5: Stability of arseno-polyoxotungstate material

[0090] The stability of the arseno-polyoxotungstate material used as a catalyst was measured. After the catalytic experiment in Example 4 was completed, the catalyst was centrifuged and its structure was characterized by infrared spectroscopy and X-ray powder diffraction techniques. It can be seen from Figure 13 and Figure 14 that the structure of the catalyst did not change before and after catalysis and remained intact.

[0091] In summary, it can be seen that the arseno-based polyoxotungstate material of the present invention can be used as a catalyst to efficiently catalyze the degradation of the antibiotic tetracycline hydrochloride.

[0092] Comparative Example 1: Comparative experimental test on the performance of degrading tetracycline hydrochloride.

[0093] In order to compare with the arseno-based polyoxotungstate material of the catalyst, under the same conditions, the degradation effects of Na3[α-AsW 12 O 40 ( Figure 9 )、Na2WO4·2H2O( Figure 10 ), EuCl3·6H2O( Figure 11 ) and CuCl2·2H2O( Figure 12 ) as catalysts on tetracycline hydrochloride were studied respectively.

[0094] The results showed that none of the above materials could degrade tetracycline hydrochloride. And it is known that after Na3[α-AsW Figure 9 O 12 O 40 was dissolved in the tetracycline hydrochloride solution, tetracycline hydrochloride might combine with Na3[α-AsW 12 O 40 , resulting in a certain degree of change in the ultraviolet-visible absorption spectrum of tetracycline hydrochloride. At the same time, when each metal component was used alone, there was basically no catalytic degradation effect, indicating that there was a certain catalytic synergistic effect in the polyoxometalate material of the present invention, and finally an excellent catalytic performance effect was exerted as a whole.

[0095] The embodiments provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit their execution order. Obvious improvements made by those skilled in the art to the present invention in combination with the existing common general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. An arsenic-based polyoxotungstate material, characterized in that, The chemical formula of the polyoxotungstate material is: NaH3[Cu(en)2(H2O)][{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2]·3.5H2O, where en refers to ethylenediamine NH2CH2CH2NH2; This polyoxotungstate material belongs to the triclinic system, space group P-1, and the unit cell parameters are α = 114.315(2)°, β = 90.651(2)°, γ = 94.210(2)°.

2. The arseno-based polyoxotungstate material according to claim 1, characterized in that, The arseno-polyoxotungstate is composed of [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- polyanion, one Na + ion, three H + ions for charge balance, one free [Cu(en)2(H2O)] 2+ ion and 3.5 water molecules.

3. The arseno-based polyoxotungstate material according to claim 2, characterized in that, The {Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- The polyanion includes one {Eu(AsW 11 O 39 )2} 11- anion, 1.5 six - coordinated [Cu(en)2] 2+ cations and one five - coordinated [Cu(en)2] 2+ cation; {Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- Each six - coordinated [Cu(en)2] 2+ cation in the polyanion is connected to the terminal oxygen atoms of two adjacent {Eu(AsW 11 O 39 )2} 11- anions through two Cu - O - W bonds. Adjacent {Eu(AsW 11 O 39 )2} 11- anions are connected into a 2D structure by six - coordinated bridging [Cu(en)2] 2+ ; {Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- The five - coordinated [Cu(en)2] 2+ cation in the polyanion is connected to the terminal oxygen atom of one {Eu(AsW 11 O 39 )2} 11- anion through one Cu - O - W bond.

4. The arseno-based polyoxotungstate material according to claim 3, characterized in that, The {Eu(AsW 11 O 39 )2} 11- The anion consists of two monovacant Keggin-type [AsW 11 O 39 ] 7- Anion sandwiches an eight-coordinated Eu Ⅲ form.

5. The arseno-based polyoxotungstate material according to claim 4, characterized in that, The octa-coordinated Eu Ⅲ is located at the vacancy position of the [AsW 11 O 39 7- anion, and coordinates with 8 oxygen atoms at the vacancy positions of two [AsW 11 O 39 7- anions, adopting a distorted square antiprismatic geometry.​​ 6. The arseno-based polyoxotungstate material according to claim 1 or 2, characterized in that, In the arseno-based polyoxotungstate material, [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- In the polyanion, the six-coordinate [Cu(en)2] 2+ ions all adopt an octahedral geometry, coordinating with the 4 N atoms provided by two ethylenediamines and two terminal O atoms provided by two adjacent {Eu(AsW 11 O 39 )2} 11- anions respectively; [{Cu(en)2}{Cu(en)2} 1.5 Eu(AsW 11 O 39 )2] 6- In the polyanion, the five-coordinate [Cu(en)2] 2+ ions adopt a square pyramidal coordination geometry, coordinating with the 4 N atoms provided by two ethylenediamines and one terminal O atom provided by {Eu(AsW 11 O 39 )2} 11 - anions respectively; The free [Cu(en)2(H2O)] 2+ ions adopt a square pyramidal coordination geometry, coordinating with the four N atoms from two ethylenediamines and one water molecule respectively.

7. The arseno-based polyoxotungstate according to claim 1 or 2, characterized in that, In the arsenic-based polyoxotungstate material, the valences of As, Eu, Cu, and W are +5, +3, +2, and +6, respectively.

8. A method for preparing an arsenic-based polyoxotungstate material according to any one of claims 1-7, characterized in that, It includes the following steps: S1: Disperse a certain amount of polyoxometalate precursor Na3[α-AsW 12 O 40 , metal salts CuCl2·2H2O and EuCl3·6H2O, and ethylenediamine ligand in distilled water, and stir and react at room temperature; S2: While continuously stirring, adjust the pH with an acid solution; S3: After continuing to stir for a period of time, raise the temperature for a high-temperature reaction; S4: After the high-temperature reaction ends, cool to room temperature to obtain purple block crystals.

9. The preparation method of the arsenic-based polyoxotungstate material according to claim 8, wherein In S1, the molar ratio of Na3[α-AsW 12 O 40 , CuCl2·2H2O, and EuCl3·6H2O is 0.15:0.6:(0.25 - 0.3); the dosage conditions of CuCl2·2H2O and the ethylenediamine ligand are 0.6 mmol:(0.08 - 0.12) mL; in S2, the pH is 3.8 - 4.2; in S3, the conditions for the high-temperature reaction are to react at 140 - 160 °C for 3 - 4 days.

10. The application of the arsenic-based polyoxotungstate material according to any one of claims 1 - 7 as a catalyst in the catalytic degradation of organic pollutant antibiotics.

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