A uranium-containing tellurium tungstate, its preparation method and application

Abstract

The present invention provides a uranium-containing tellurium tungstate, a preparation method and an application thereof, belonging to the technical field of new polyacid chemistry materials. The chemical formula of the present invention is [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O, belonging to the monoclinic system, space group P21 / n, and the unit cell parameters are: #imgabs0# α = γ = 90°, β = 89.899°, #imgabs1# Z = 4. After stirring sodium tungstate, sodium perchlorate and sodium tellurite in an aqueous solution, dimethylamine hydrochloride is added and the pH is adjusted, and then uranyl nitrate is added for a water bath reaction followed by post-treatment to obtain the uranium-containing tellurium tungstate. The uranium-containing tellurium tungstate of the present invention has a clear structure and good stability, and has photochromism. Its preparation process is simple and easy to operate.

Description

Technical Field

[0001] The present invention belongs to the technical field of new polyoxometalate chemistry materials, and particularly relates to a uranium tellurium tungstate, a preparation method thereof, and an application thereof. Background Art

[0002] The energy shortage crisis and carbon emission problems are making countries around the world re-examine the importance of nuclear power development. As a prerequisite for the sustainable development of nuclear energy, how to safely and efficiently handle the spent fuel generated by the nuclear fuel cycle remains a worldwide problem yet to be solved. Uranium, as the main component of spent fuel (accounting for up to 95%), the research on its related coordination chemistry is of great significance for the reprocessing of spent fuel. Polyoxometalates (abbreviated as POMs) are a large class of high-nuclear metal-oxygen clusters formed by the connection of transition metal elements such as Mo, W, and V with oxygen atoms, with structural diversity and tunable functions, and have been rapidly developed in the research of catalysis, medicine, magnetism, etc. (M.T. Pope, A. Müller, Angew. Chem. Int. Ed. Engl. 1991, 30, 34 - 48; H.N. Miras, J. Yan, D.-L. Long, L. Cronin, Chem. Soc. Rev. 2012, 41, 7403 - 7430; L. Qin, R. Wang, X. Xin, M. Zhang, T. Liu, H. Lv, G.-Y. Yang, Appl. Catal. B Environ. 2022, 312, 121386; M. Lu, M. Zhang, J. Liu, T.-Y. Yu, J.-N. Chang, L.-J. Shang, S.-L. Li, Y.-Q. Lan, J. Am. Chem. Soc. 2022, 144, 1861 - 1871.). Hexavalent uranyl ion (UO2 2+)As a hard acid, it readily forms bonds with oxygen atoms. The surface of POMs anions is rich in coordinatable oxygen atoms, and the two are expected to combine to form uranium-containing polyoxometalates with novel structures. Currently, the development of uranium-containing polyoxometalates is relatively slow, mainly including Keggin and Dawson-type heteropolyoxometalates (G.-P. Yang, K. Li, C.-W. Hu, Inorg. Chem. Front., 2022, 9, 5408-5433.). There are only 5 reports on uranium-containing polyoxometalates with other configurations (V.W. Day, C.W. Earley, W.G. Klemperer, D.J. Maltbie, J. Am. Chem. Soc. 1985, 107, 8261-8262; V.W. Day, W.G. Klemperer, D.J. Maltbie, Organometallics 1985, 4, 104-111; Y. Jeannin, Comptes Rendus Chimie, 2005, 8, 999-1004; T. Deb, L. Zakharov, C. Falaise, M. Nyman, Inorg. Chem. 2016, 55, 755-761; N.P. Martin, E. Petrus, M. Segado, A. Arteaga, L.N. Zakharov, C. Bo, M. Nyman, Chem. Eur. J. 2019, 25, 10580-10584.). It is worth noting that the property research of uranium-containing polyoxometalates is relatively scarce (G.-P. Yang, K. Li, C.-W. Hu, Inorg. Chem. Front., 2022, 9, 5408-5433.), while POMs have attracted extensive attention in the field of photochromism (T. Yamase, Chem. Rev. 1998, 98, 307-325; Y.-M. Di, M.-H. Li, M.-H. You, S.-Q. Zhang, M.-J. Lin, Inorg. Chem. 2021, 60, 16233-16240).

[0003] Photochromism (PC) refers to the reversible change in color and absorption spectrum of a compound when irradiated with light of a certain wavelength. In 1867, Fritzsche first observed the photochromic phenomenon. When tetracene was exposed to sunlight, it turned colorless and returned to its original orange color when placed in the dark (J. Fritzsche, Science Paris, 1867, 69, 78 - 78.). It wasn't until 1950 that Hirshberg defined this phenomenon as photochromism (Y. Hirshberg, CR Hebd. Seances Acad Science, 1950, 231, 903 - 904.). In 1978, Professor Heller pointed out that photochromism has good applications in information storage and optical recording, etc. Since then, PC has received extensive attention from people in the high - tech field. The color - change mechanism of POMs is that under ultraviolet - visible light irradiation, the electrons in the low - energy O 2p orbitals of POMs transition to the high - energy metal d orbitals, causing the metal ions to change from d 0 to d 1 state. During the process of d 1 electron transfer in the metal center or d - d orbitals, an intervalence charge transfer (IVCT) process occurs, resulting in a change in the color of the polyoxometalate (heteropoly blue or heteropoly brown) (T. Yamase, Chem. Rev. 1998, 98, 307 - 326; T. He, J. Yao, Progress in Materials Science 2006, 51, 810 - 879; Z. Ku, S. Jin, Journal of Wuhan University of Technology - Materials Science Edition 2008, 23, 367 - 371.). In recent years, research groups such as Niu Jingyang and Mialane have conducted relevant research on the photochromism of polyoxometalates (A. Parrot, A. Bernard, A. Jacquart, Angew. Chem. Int. Ed. 2017, 56, 4872 - 4876; K. Zheng, B. Niu, C. Lin, Y. Song, P. Ma, J. Wang, J. Niu, Chin. Chem. Lett. 2023, 34, 107238 - 107241.). Currently, in terms of both quantity and structural types, the research on uranium - containing polyoxometalate clusters is relatively less, especially the research on uranium - containing polyoxometalates in photochromic materials. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a uranium-containing tellurium tungstate, a preparation method thereof, and an application thereof. The preparation method of the uranium-containing tellurium tungstate of the present invention has a low cost, a safe and simple preparation process, and is easy to operate. Moreover, the prepared uranium-containing tellurium tungstate has photochromic properties, so it has potential application value in the field of POM photochromic materials.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows:

[0006] A uranium-containing tellurium tungstate, the chemical formula of the uranium-containing tellurium tungstate is [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O, belonging to the monoclinic system, the space group is P21 / n, and the unit cell parameters are: α = γ = 90°, β = 89.899°, Z = 4.

[0007] Furthermore, the structural unit of the uranium-containing tellurium tungstate [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O contains 14 [H2N(CH3)2] + ions, 4 Na + ions, one [(UO2)2(H2O)2(Te3W 21 O 75 H)2] 18- polyoxyanion and 18 crystal water molecules.

[0008] Furthermore, the [(UO2)2(H2O)2(Te3W 21 O 75 H)2] 18- polyoxyanion contains two uranyl ions and two [Te3W 21 O 75 12- units.

[0009] The preparation method of the described uranium-containing tellurium tungstate is as follows:

[0010] ​Dissolve Na2WO4·2H2O in water, then add NaClO4·H2O, Na2TeO3 and dimethylamine hydrochloride respectively and stir, and add glacial acetic acid to adjust the pH to 5.2 - 6.0. Subsequently, add an aqueous solution of uranyl nitrate at the same time, and adjust the pH to 4.0 - 5.0 with glacial acetic acid. Heat in a water bath, filter after the solution cools to room temperature, and let the clarified filtrate stand and volatilize at room temperature to obtain uranyl tellurium tungstate crystals.

[0011] Furthermore, the concentration of the UO2(NO3)2·6H2O aqueous solution is 1.0 mol / L.

[0012] Furthermore, the molar ratio of Na2WO4·2H2O, NaClO4·H2O, Na2TeO3, dimethylamine hydrochloride and UO2(NO3)2·6H2O in the reaction solution is 75:8:6:120:(1 - 3).

[0013] Furthermore, the temperature of the water bath heating is 90 - 95 °C, and the time is 0.5 - 3 h; the standing and volatilization time is 10 - 20 days.

[0014] Furthermore, the application of the uranyl tellurium tungstate in photochromic materials.

[0015] The beneficial effects of the present invention are as follows:

[0016] 1. In the present invention, simple raw material Na2WO4·2H2O is reacted with heteroatoms to synthesize uranyl tellurium tungstate [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O, which enriches the structural diversity.

[0017] 2. The preparation method of the uranyl tellurium tungstate prepared in the present invention adopts a conventional aqueous solution preparation method. After the reaction is completed, it can be obtained by simple post-treatment operation of standing and volatilization. The cost is low, the preparation process is safe and simple, and it is easy to operate.

[0018] 3. The uranyl tellurium tungstate [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75The structure of [UO₂)₂(H₂O)₂(Te₃W₁₂O₄₂)]·18H₂O is well-defined. At 25 °C, after irradiating the uranium tellurium tungstate with light for 2 h, the crystal color of the uranium tellurium tungstate changes from yellow to black. After stopping the light irradiation, the discolored uranium tellurium tungstate is placed in the dark for 2 days, and it is observed that the uranium tellurium tungstate returns to its original yellow color, showing a reversible photochromic phenomenon. When the uranium tellurium tungstate that has regained its color is irradiated with light again, a reversible color change-fading process can still be observed, which has potential application value in polyoxometalate-based photochromic materials. Description of the Drawings

[0019] 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 for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0020] Figure 1 It is the structural diagram of the uranium tellurium tungstate prepared in Example 1 of the present invention. Among them, a and b are the ball-and-stick and polyhedron schematic diagrams of the anion [(UO₂)₂(H₂O)₂(Te₃W₁₂O₄₂)]; c is the polyhedron structural diagram of the [TeW₉O₃₀] unit; d is the polyhedron structural diagram of the [TeW₆O₂₁] unit; e is the ball-and-stick diagram of the [Te₃W₁₂O₄₂] unit; f is the schematic diagram of the O atom positions in the [TeW₆O₂₁] unit; g is the dihedral angle between two [TeW₆O₂₁] units; h is the geometric configuration of the U atom. 21 O 75 H)₂ 18- ; c is the polyhedron structural diagram of the [TeW₉O₃₀] unit; d is the polyhedron structural diagram of the [TeW₆O₂₁] unit; e is the ball-and-stick diagram of the [Te₃W₁₂O₄₂] unit; f is the schematic diagram of the O atom positions in the [TeW₆O₂₁] unit; g is the dihedral angle between two [TeW₆O₂₁] units; h is the geometric configuration of the U atom. 33 8- unit; d is the polyhedron structural diagram of the [TeW₆O₂₁] unit; e is the ball-and-stick diagram of the [Te₃W₁₂O₄₂] unit; f is the schematic diagram of the O atom positions in the [TeW₆O₂₁] unit; g is the dihedral angle between two [TeW₆O₂₁] units; h is the geometric configuration of the U atom. 21 2- unit; e is the ball-and-stick diagram of the [Te₃W₁₂O₄₂] unit; f is the schematic diagram of the O atom positions in the [TeW₆O₂₁] unit; g is the dihedral angle between two [TeW₆O₂₁] units; h is the geometric configuration of the U atom. 21 O 75 12- unit; f is the schematic diagram of the O atom positions in the [TeW₆O₂₁] unit; g is the dihedral angle between two [TeW₆O₂₁] units; h is the geometric configuration of the U atom. 21 2- unit; g is the dihedral angle between two [TeW₆O₂₁] units; h is the geometric configuration of the U atom. 21 2- units; h is the geometric configuration of the U atom.

[0021] Figure 2 It is the color change of the uranium tellurium tungstate prepared in Example 1 of the present invention under 10 W visible light irradiation.

[0022] Figure 3 It is the visible light absorption spectrum (a), the relationship diagram between the diffuse reflectance spectrum of the Kubelka-Munk function and energy (eV) before light irradiation (b), the relationship diagram between the diffuse reflectance spectrum of the Kubelka-Munk function and energy (eV) after light irradiation (c), and the relationship diagram between the reflectance and the light irradiation time at different light irradiation times (d) of the uranium tellurium tungstate prepared in Example 1 of the present invention. ​​​​​

[0023] Figure 4 The first-order kinetic fitting curve of the uranium-containing tellurium tungstate prepared in Example 1 of the present invention under light irradiation.

[0024] Figure 5 The X-ray powder diffraction comparison pattern of the uranium-containing tellurium tungstate prepared in Example 1 of the present invention before and after color change-fading. Specific embodiments

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] Example 1

[0027] The uranium-containing tellurium tungstate [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O in this example is prepared as follows:

[0028] (1) Preparation of UO2(NO3)2·6H2O solution (1.0 mol·L -1 ): 5.02 g of uranyl nitrate (UO2(NO3)2·6H2O) is dissolved in 10.0 mL of distilled water.

[0029] (2) Under stirring conditions, 15.0 g of Na2WO4·2H2O is dissolved in 120.0 mL of water, 0.65 g of NaClO4·H2O is added, and after stirring at room temperature for 30 min, 1.0 g of Na2TeO3 is added and stirring continues at room temperature for 30 min. 6 g of dimethylamine hydrochloride is added and stirred for 20 min, then the pH is adjusted to 5.6 with 98% glacial acetic acid and stirring continues for 10 min. Subsequently, 0.6 mL of the UO2(NO3)2·6H2O solution prepared in step (1) is added and the pH is adjusted to 4.5 with 98% glacial acetic acid. React at 90 °C for 1 h, filter and leave for 15 days to obtain yellow crystals, and the yield is about 18% (based on UO2(NO3)2·6H2O).

[0030] Among them, the molar ratio of the reaction raw materials Na2WO4, NaClO4·H2O, Na2TeO3, dimethylamine hydrochloride and UO2(NO3)2·6H2O is 75:8:6:120:1.

[0031] Example 2

[0032] This example involves the preparation method of uranium-containing tellurium tungstate [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O, and the steps are as follows:

[0033] (1) Preparation of UO2(NO3)2·6H2O solution (1.0 mol·L -1 ): 5.02 g of uranyl nitrate (UO2(NO3)2·6H2O) is dissolved in 10.0 mL of distilled water to obtain it.

[0034] (2) Under stirring conditions, 15.0 g of Na2WO4·2H2O is dissolved in 120.0 mL of water, 0.65 g of NaClO4·H2O is added, and after stirring at room temperature for 30 min, 1.0 g of Na2TeO3 is added and stirring continues at room temperature for 30 min. Then 6 g of dimethylamine hydrochloride is added and stirred for 20 min, and the pH is adjusted to 5.6 with 98% glacial acetic acid and stirring continues for 10 min. Subsequently, 0.6 mL of the UO2(NO3)2·6H2O solution prepared in step (1) is added and the pH is adjusted to 4.5 with 98% glacial acetic acid. React at 95 °C for 0.5 h, filter and leave for 15 days to obtain yellow crystals, and the yield is about 23% (based on UO2(NO3)2·6H2O).

[0035] Among them, the molar ratio of the reaction raw materials Na2WO4, NaClO4·H2O, Na2TeO3, dimethylamine hydrochloride and UO2(NO3)2·6H2O is 75:8:6:120:1.

[0036] Example 3

[0037] This example involves the preparation method of uranium-containing tellurium tungstate [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O, and the steps are as follows:

[0038] (1) Preparation of UO2(NO3)2·6H2O solution (1.0 mol·L -1 ) : 5.02 g of uranyl nitrate (UO2(NO3)2·6H2O) is dissolved in 10.0 mL of distilled water to obtain it.

[0039] (2) Under stirring conditions, dissolve 15.0 g of Na2WO4·2H2O in 120.0 mL of water, add 0.65 g of NaClO4·H2O, stir at room temperature for 30 min, then add 1.0 g of Na2TeO3 and continue stirring at room temperature for 30 min. Add 6 g of dimethylamine hydrochloride and stir for 20 min, then adjust the pH to 5.6 with 98% glacial acetic acid and continue stirring for 10 min. Subsequently, add 0.6 mL of the UO2(NO3)2·6H2O solution prepared in step (1) and adjust the pH to 4.5 with 98% glacial acetic acid. React at 90 °C for 3 h, filter and let stand for 15 days to obtain yellow crystals, with a yield of approximately 32% (based on UO2(NO3)2·6H2O).

[0040] Among them, the molar ratio of the reaction raw materials Na2WO4, NaClO4·H2O, Na2TeO3, dimethylamine hydrochloride and UO2(NO3)2·6H2O is 75:8:6:120:1.

[0041] Example 4

[0042] This example involves the preparation method of uranium tellurium tungstate [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O, and the steps are as follows:

[0043] (1) Preparation of UO2(NO3)2·6H2O solution (1.0 mol·L -1 ): Dissolve 5.02 g of uranyl nitrate (UO2(NO3)2·6H2O) in 10.0 mL of distilled water.

[0044] (2) Under stirring conditions, dissolve 15.0 g of Na2WO4·2H2O in 120.0 mL of water, add 0.65 g of NaClO4·H2O, stir at room temperature for 30 min, then add 1.0 g of Na2TeO3 and continue stirring at room temperature for 30 min. Add 6 g of dimethylamine hydrochloride and stir for 20 min, then adjust the pH to 5.2 with 98% glacial acetic acid and continue stirring for 10 min. Subsequently, add 0.6 mL of the UO2(NO3)2·6H2O solution prepared in step (1) and adjust the pH to 5.0 with 98% glacial acetic acid. React at 93 °C for 2 h, filter and let stand for 20 days to obtain yellow crystals, with a yield of approximately 12% (based on UO2(NO3)2·6H2O).

[0045] Among them, the molar ratio of the reaction raw materials Na2WO4, NaClO4·H2O, Na2TeO3, dimethylamine hydrochloride and UO2(NO3)2·6H2O is 75:8:6:120:1.

[0046] Example 5

[0047] This example involves the preparation method of uranyl tellurium tungstate [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O, and the steps are as follows:

[0048] (1) Preparation of UO2(NO3)2·6H2O solution (1.0 mol·L -1 ): 5.02 g of uranyl nitrate (UO2(NO3)2·6H2O) was dissolved in 10.0 mL of distilled water to prepare it.

[0049] (2) Under stirring conditions, 15.0 g of Na2WO4·2H2O was dissolved in 120.0 mL of water, 0.65 g of NaClO4·H2O was added, and after stirring at room temperature for 30 min, 1.0 g of Na2TeO3 was added and stirring continued at room temperature for 30 min. Then 6 g of dimethylamine hydrochloride was added and stirred for 20 min, and the pH was adjusted to 6.0 with 98% glacial acetic acid and stirring continued for 10 min. Subsequently, 0.6 mL of the UO2(NO3)2·6H2O solution prepared in step (1) was added and the pH was adjusted to 4.0 with 98% glacial acetic acid. Reacted at 95 °C for 0.5 h, filtered and left for 10 days to obtain yellow crystals, and the yield was about 23% (based on UO2(NO3)2·6H2O).

[0050] Among them, the molar ratio of the reaction raw materials Na2WO4, NaClO4·H2O, Na2TeO3, dimethylamine hydrochloride and UO2(NO3)2·6H2O is 75:8:6:120:1.

[0051] Example 6

[0052] This example involves the preparation method of uranyl tellurium tungstate [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O, and the steps are as follows:

[0053] (1) Preparation of UO2(NO3)2·6H2O solution (1.0 mol·L -1 ): 5.02 g of uranyl nitrate (UO2(NO3)2·6H2O) was dissolved in 10.0 mL of distilled water to prepare it.

[0054] (2) Under stirring conditions, dissolve 15.0 g of Na2WO4·2H2O in 120.0 mL of water, add 0.65 g of NaClO4·H2O, stir at room temperature for 30 min, then add 1.0 g of Na2TeO3 and continue stirring at room temperature for 30 min. Add 6 g of dimethylamine hydrochloride and stir for 20 min, then adjust the pH to 6.0 with 98% glacial acetic acid and continue stirring for 10 min. Subsequently, add 1.8 mL of the UO2(NO3)2·6H2O solution prepared in step (1) and adjust the pH to 4.0 with 98% glacial acetic acid. React at 95 °C for 0.5 h, filter and let stand for 10 days to obtain yellow crystals with a yield of approximately 19% (based on UO2(NO3)2·6H2O).

[0055] Among them, the molar ratio of the reaction raw materials Na2WO4, NaClO4·H2O, Na2TeO3, dimethylamine hydrochloride and UO2(NO3)2·6H2O is 75:8:6:120:3.

[0056] Structure identification

[0057] The uranium tellurium tungstate prepared in Example 1 above was detected. The chemical formula of the detected product is [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O. The structure diagram of this uranium tellurium tungstate is as shown in Figure 1 shown, Figure 1 where a and b are the ball-and-stick and polyhedron schematic diagrams of the anion [(UO2)2(H2O)2(Te3W 21 O 75 H)2] 18- ; c is the polyhedron structure diagram of the [TeW9O 33 8- unit; d is the polyhedron structure diagram of the [TeW6O 21 2- unit; e is the ball-and-stick diagram of the [Te3W 21 O 75 12- unit; f is the schematic diagram of the O atom position in the [TeW6O 21 2- unit; g is the dihedral angle between two [TeW6O 21 2- units; h is the geometric configuration of the U atom. {WO6}, blue-green octahedron; O, red sphere; Te, blue sphere; W, blue-green sphere; U, yellow sphere.

[0058] The specific structure of the uranium tellurium tungstate of the present invention is described as follows: It contains the anion [(UO2)2(H2O)2(Te3W​​​​​21 O 75 H)2] 18- , four sodium ions, fourteen dimethylamine ions and eighteen crystal water molecules. The results of X-ray single crystal diffraction analysis show that the anion [(UO2)2(H2O)2(Te3W 21 O 75 H)2] 18- is composed of two uranyl ions connecting two [Te3W 21 O 75 12- units, and the uranyl ions are in the ortho position. [Te3W 21 O 75 12- unit is a three-layer structure, consisting of a three-deficient Keggin-type [TeW9O 33 8- unit and two [Te W6O 21 2- connected by sharing corners to form a pagoda-like structure. The Te Ⅳ atom adopts a three-coordinate trigonal pyramid configuration, and the {TeO3} groups in each layer have the same orientation. In the [TeW6O 21 2- fragment, six μ2-O are alternately distributed above and below the plane created by {W6}. The bond length range of the Te-O bond in the {TeO3} unit is The bond angle range of O-Te-O is 90.73°-94.58°. It should be noted that the two [Te3W 21 O 75 12- units are not linearly aligned, and there is an angle of 44.204°. The uranium atom forms a seven-coordinate pentagonal bipyramid configuration with 4 oxygen atoms, 1 coordinated water molecule and 2 acyl oxygen atoms from the [Te3W 21 O 75 12- unit. The average bond length of the uranyl bond is The bond angle is 178.432°.

[0059] Bond valence calculations (see Brown ID, et.al, 1985, B41, 244-247.) show that all W and U in this anion are +6 valence, and all Te atoms are +4 valence. For all O atoms, the BVS values of oxygen atoms O11 and O141 are -0.32 and -0.33 respectively, indicating coordinated water molecules; the BVS values of oxygen atoms O3 and O7 are -1.50 and -1.1, which are hydroxyl groups; the remaining oxygen atoms are -2 valence.

[0060] [H2N(CH3)2] 14 ​​​​​​​Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O has the following unit cell parameters: α = γ = 90°, β = 89.899°.

[0061] Application Example

[0062] The uranium tellurium tungstate prepared in Example 1 was used as a photochromic material, and its performance was tested as follows:

[0063] Using a Vlight porous photocatalytic reaction system with an electric power of 10 W, the uranium tellurium tungstate of the present invention was irradiated with light at 25 °C with 98% current, and its photochromic test was carried out. The results are as Figure 2 shown. After 2 h of irradiation, the color of the uranium tellurium tungstate turned completely black, showing photochromism. After stopping the irradiation, the photochromic uranium tellurium tungstate was dark-treated for 2 days under dark conditions, and it was observed that the uranium tellurium tungstate of the present invention returned to its original yellow color, showing a reversible photochromic phenomenon. When the uranium tellurium tungstate of the present invention that had returned to yellow was irradiated again, a reversible color change-fading process could still be observed.

[0064] Figure 3 Figure a in shows the visible light absorption spectra of the uranium tellurium tungstate at different irradiation times. It can be observed that the intensities of the absorption peaks at 482 nm and 499 nm increase with the increase of the irradiation time. When the color returns to yellow after stopping the irradiation, the intensities of its absorption peaks also decrease. The relationships between the diffuse reflection spectra of the Kubelka-Munk function and the energy (eV) before irradiation and after irradiation are respectively as Figure 3 Figure b in and Figure 3 Figure b in shown. By calculating the band gaps before and after irradiation using the Kubelka-Munk function, it was found that the band gap of the uranium tellurium tungstate of the present invention before irradiation was 2.95 eV, and the band gap after irradiation decreased to 2.38 eV, indicating that irradiation induced photochromism. At room temperature, the kinetics of the photochromic process was fitted, and a preliminary analysis of the kinetics of the photochromic process was carried out. By plotting the graph of the reflectance changing with the irradiation time ( Figure 3 Figure d in), and performing a linear fit on it, the result was in good agreement with the function R(t) = a / (bt + 1) + c.

[0065] On this basis, the first-order kinetics process of photochromism was further simulated:

[0066]

[0067] where k is the rate constant, when t = 0, R0 = Rt When, the formula can be transformed into:

[0068]

[0069] Plot the relationship graph of Ln(R0 / R t ) against the change of time t, and perform first-order kinetic linear fitting on it, and calculate the rate constant k = 0.723h -1 , R 2 = 0.987. Therefore, the result conforms to the first-order kinetic process. Figure 4 This is the first-order kinetic fitting curve of the uranium-containing tellurium tungstate prepared in Example 1 of the present invention under light irradiation.

[0070] During the photochromic process, X-ray powder diffraction tests were carried out on the uranium-containing tellurium tungstate of the present invention. The results are as Figure 5 shown, indicating that there are no obvious changes in the comparison of its X-ray powder diffraction pattern with the simulated data during light irradiation and after fading. Therefore, photoinduced structural isomerization and photodecomposition are excluded during the photochromic-fading process, and it is confirmed that the photochromic phenomenon is caused by electron transfer in the structure.

[0071] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A uranium tellurium tungstate, characterized in that, The chemical formula of the uranium-containing tellurium tungstate is [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O, belonging to the monoclinic system, with the space group P21 / n, and the unit cell parameters are: α = γ = 90°, β = 89.899°, Z = 4.

2. The uranium-containing tellurium tungstate according to claim 1, characterized in that, The uranium-containing tellurium tungstate [H2N(CH3)2] 14 Na4[(UO2)2(H2O)2(Te3W 21 O 75 H)2]·18H2O contains 14 [H2N(CH3)2] + ions, 4 Na + ions, one [(UO2)2(H2O)2(Te3W 21 O 75 H)2] 18- polyanion and 18 crystal water molecules.

3. The uranium-containing tellurium tungstate according to claim 1 or 2, characterized in that, The [(UO2)2(H2O)2(Te3W 21 O 75 H)2] 18- The polyanion contains two uranyl ions and two [Te3W 21 O 75 12- units.​ 4. The preparation method of the uranium-containing tellurium tungstate according to claim 3, characterized in that, The steps are as follows: Dissolve Na2WO4·2H2O in distilled water, then add NaClO4·H2O, Na2TeO3 and dimethylamine hydrochloride respectively and stir. Adjust the pH to 5.2 - 6.

0. Subsequently, add a UO2(NO3)2·6H2O solution dropwise to the solution and adjust the pH again to 4.0 - 5.

0. Heat in a water bath. After the reaction solution is cooled to room temperature, filter it. Leave the clear filtrate to stand and volatilize at room temperature to obtain uranium tellurium tungstate crystals.

5. The preparation method of the uranium-containing tellurium tungstate according to claim 4, characterized in that, The solution for adjusting the pH is glacial acetic acid solution.

6. The preparation method of the uranium-containing tellurium tungstate according to claim 5, characterized in that, The solvent of the UO2(NO3)2·6H2O solution is water.

7. The preparation method of the uranium-containing tellurium tungstate according to claim 6, characterized in that, The concentration of the UO2(NO3)2·6H2O solution is 1.0 mol / L.

8. The preparation method of the uranium-containing tellurium tungstate according to claim 7, characterized in that, The molar ratio of Na2WO4·2H2O, NaClO4·H2O, Na2TeO3, dimethylamine hydrochloride and UO2(NO3)2·6H2O in the reaction solution is 75:8:6:120:(1 - 3).

9. The preparation method of the uranium-containing tellurium tungstate according to any one of claims 4-8, characterized in that, The temperature of the water bath heating is 90 - 95 °C, and the time is 0.5 - 3 h; the standing and volatilization time is 10 - 20 days.

10. Use of the uranium tellurium tungstate according to claim 3 in a photochromic material.

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