A compound, its preparation method and application

Abstract

This invention discloses a compound, its preparation method, and its applications, with the molecular formula C0. 49 H 70 Mo9N7O 33 P, preparation method, firstly, H3PMo 12 O 40 • 13H₂O was dissolved in ultrapure water and stirred until completely dissolved. Then, 3-ethylpyridine solution was added to the above solution using a pipette. After stirring, the mixture was immediately transferred to a sealed stainless steel high-pressure reactor lined with polytetrafluoroethylene. The temperature was raised to 160°C and maintained for crystallization for 3 days. Afterward, the power was turned off and the reactor was slowly cooled to room temperature. The residue was filtered out, and the reactor was sealed and allowed to stand to obtain green blocky crystals. This can be used as a material for adsorbing organic dyes.

Description

Technical Field

[0001] This invention belongs to the field of compounds, specifically relating to a compound, its preparation method, and its application. Background Technology

[0002] Polyoxometalates (POMs) are a class of nanoclusters with defined topological structures composed of early transition metals and oxygen. They can be viewed as a series of metal-oxygen polyhedral structural units (MOs). x The components are connected by sharing angles, sides, or planes, where M is a transition metal (M = V). 5+ , Nb 5+ , Ta 5+ Mo 6+ W 6+ (Mostly in their highest oxidation state). Among the diverse range of heteropoly compounds, Keggin-type POMs are the earliest discovered heteropoly acids, with the general structural formula [XM]. 12 O 40 ] n- (X = P, Si, Ge, As, etc., M = Mo, W) are the most stable species, and due to their structural diversity, they have been the subject of scientific study for a long time. The first heteropolyacid was discovered by Berzerius in 1826, but its structure was not determined by Gibbs and Scheibler as (NH4)3[PMo] in 1909. 12 O 40 Keggin-type POMs have five isomers: α, β, γ, δ, and ε, with the α structure being the most studied. The α-Keggin anion is a highly symmetrical oxygen-containing cluster consisting of 12 MO6 octahedra surrounding an XO4 tetrahedron. Each set of three octahedra is connected by shared edges to form four trimetallic oxygen clusters (M3O4). 13 Then it is connected to the central tetrahedron via a common angle. The difference between these isomers lies in M3O. 13 The properties of the connection, which will connect an M3O 13 Rotate 60° to obtain C 3v Symmetric β isomer, C 3-axis passing through the rotated M3O 13 All M3O 13 Still connected via a shared corner. The second M3O 13 Rotation by 60° produces the γ isomer ( C 2v (symmetric), in which two M3O 13 The remaining M3O are connected via a shared edge. 13Connected via a shared corner. The remaining two M3O 13 Continuous rotation by 60° yielded δ and α isomers. The δ isomer possesses... C 3v Symmetry, with 3 side-shared bonds and 1 corner-shared bond. The α-isomer shares all shared sides with M3O. 13 have T d Symmetry. With each successive M3O 13 Rotate, share edge M3O 13 The quantity increased.

[0003] Covalently functionalized polyoxometalates (POMs) have been widely used to control and enhance their redox properties. Specifically, POMs can covalently couple an effective, unlimited range of organic components, opening exciting new avenues for their rational design. Furthermore, unlike organic-inorganic component combinations, they promote the formation of complex molecular structures and the emergence of new, unique functions. POM hybrid clusters obtained through organic covalent modification can be divided into two categories: one where one or more oxygen atoms in the POM polyhedron are replaced by N or O atoms of an organic ligand, allowing direct connection to the metal center of the POM unit to form MO or MN covalent bonds (M being Mo, W, Si, etc.); and another where the N atom of the organic ligand covalently connects with the oxygen atoms on the POM cluster shell through electrophilic interactions to form NO bonds. Clearly, N- or O-containing organic ligands are candidate materials for designing and preparing organic covalent POM hybrids. Among these, N-containing organic ligands mainly include organic imides, organic diazoimides, pyridines, and diazacyclic ligands, specifically used for the hybrid modification of POMs. Keggin-type POMs molecules under certain alkaline conditions MO x Polyhedral dehiscence forms different types of vacant POMs, and due to their highly nucleophilic terminal oxygen sites, vacant POMs are conducive to covalent interactions with the electrophilic groups of the organic moiety. Besides their designable properties, vacant POMs also possess well-defined coordination sites and diverse coordination directions and numbers, making them ideal building blocks for inorganic-organic system architectures. However, they are metastable and frequently undergo unexpected isomerization or decomposition reactions, which are difficult to control, thus limiting their applications. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems, the first objective of the present invention is to provide a compound, the second objective is to provide a method for preparing the compound, and the third objective is to provide its application.

[0005] To achieve the aforementioned first objective, the present invention provides the following technical solution: a compound, characterized in that: its molecular formula is C 49 H70 Mo9N7O 33 P, structure as follows Figure 1 As shown.

[0006] The second objective of this invention is achieved as follows: a method for preparing the compound, characterized in that: firstly, H3PMo... 12 O 40 • Dissolve 13H2O in ultrapure water and stir until completely dissolved. Then, add 3-ethylpyridine solution to the above solution using a pipette. After stirring, immediately transfer the mixture to a sealed stainless steel high-pressure reactor lined with polytetrafluoroethylene. Heat to 160 °C and maintain crystallization for 3 days. After that, turn off the power and allow it to cool slowly to room temperature. Open the reactor, filter out the residue, seal and let stand to obtain green block crystals.

[0007] In the above scheme: after filtering out the residue, the light green transparent mother liquor is transferred to a beaker, sealed with plastic wrap, and left to stand at room temperature for 3-4 days to obtain light green blocky crystals.

[0008] A third object of the present invention is to provide the use of the compound as a material for adsorbing organic dyes.

[0009] Based on these properties of Keggin-type POMs, we focused on their organic covalent modification. Among them, vacant POMs with highly nucleophilic terminal oxo sites are key precursors for functional groups, such as vacant Keggin-type [PMo] 11 O 39 ] 7- and [PMo9O] 34 ] 9- However, the inherent metastable state of these vacancy species complicates the synthetic process, requiring at least one additional synthetic step, such as the arduous process of obtaining the water-insoluble Bu4N. + Salt synthesis is used to stabilize vacancy structures and protect their missing sites. Inspired by this sensitive behavior, we developed an efficient in-situ covalent functionalization method for Keggin-type POMs and established a simple Keggin / 3-ethylpyridine aqueous phase reaction system. The 3-ethylpyridine molecule is expected to achieve the following objectives under in-situ conditions: (i) triggering the degradation of saturated clusters to vacancy clusters; and (ii) grafting as a functional agent onto the surface of POMs. Although various methods for surface modification of POMs have been reported, the harsh reaction conditions, complex synthetic steps, and environmental unfriendliness have greatly limited the development and application of this system in various fields. Exploring and developing simple, economical, and efficient novel organic synthesis reactions is an effective way to solve the current technical challenges of reaction systems.

[0010] A novel in-situ degradation and organic synthesis technique for Keggin-type POMs under a simple aqueous reaction system has been developed. This strategy effectively solves many technical challenges in the traditional organic modification of POMs. In-depth research in this project will enrich the synthetic methods of POM organic modification chemistry, improve reaction routes, broaden research ideas and directions, and promote the development and application of POM organic derivatives in various fields. It is certain that the development of novel synthetic techniques has brought new opportunities and broad prospects for the organic modification of POMs. We utilize the degradability of Keggin-type POMs under alkaline conditions, using 3-ethylpyridine as a pH adjuster, to synthesize saturated phosphomolybdic acid [PMo] in aqueous solution. 12 O 40 ] 3- ([PMo) 12 In situ degradation into three-vacancy [PMo9O] 34 ] 9- ([PMo9]) and the unstable vacant POM was covalently modified by substituting the terminal oxygen. Attached Figure Description

[0011] Figure 1 This is a structural diagram of the grafted compound of the present invention.

[0012] Figure 2 a) The compound forms a 1D chain through H-bonds; b) The compound forms a 2D layered structure through H-bonds.

[0013] Figure 3 a) 3D network skeleton of the compound; b) 3D topological mesh of the compound.

[0014] Figure 4 a) XPS spectrum and peak fitting of Mo 3d signal; b) XPS full spectrum of compound.

[0015] Figure 5 Simulation and experimental study of the PXRD of the compound.

[0016] Figure 6 TG / DTG curves of the compound Figure 7 This is the Fourier transform infrared spectrum (FT-IR) of the compound.

[0017] Figure 8 The UV-Vis spectra of the compound, 3-ethylpyridine, and phosphomolybdic acid are shown.

[0018] Figure 9 The CV chromatogram of the compound after multiple cycles in 0.1 M Na2SO4 + 0.5 M H2SO4 solution (scan rate: 50 mV∙s) -1 ).

[0019] Figure 10 a) UV-vis of MB solution in the presence of the compound; b) C / C0 of MB solution in the presence of the compound as a function of reaction time. Detailed Implementation

[0020] The present invention will now be further described with reference to the accompanying drawings and embodiments.

[0021] Example 1 Reagents used Reagent Name Chemical formula purity Manufacturer 3-Ethylpyridine <![CDATA[C7H9N]]> Analytical Pure Adamas Reagent Company, China Phosphomolybdic acid <![CDATA[H3PMo 12 EITHER 40 ·13H2O]]> Analytical Pure Adamas Reagent Company, China Anhydrous sodium sulfate <![CDATA[Na2SO4]]> Analytical Pure Tianjin Chemical Reagent Factory No. 6 concentrated sulfuric acid <![CDATA[H2SO4]]> Analytical Pure Chongqing Chuandong Chemical Co., Ltd. Nafion <![CDATA[C9HF 17 O5S]]> Analytical Pure Adamas Reagent Company, China Methylene blue <![CDATA[C 16 H 18 ClN3S]]> Analytical Pure Adamas Reagent Company, China Potassium bromide KBr Spectroscopically pure Tianjin Tianguang Optical Instrument Co., Ltd. Prepared according to the following method: First, H3PMo 12 O 40 • 13H₂O (0.2 g, 0.1096 mmol) was dissolved in 4 mL of ultrapure water and stirred for 15 min until completely dissolved. Then, 1 mL of 3-ethylpyridine solution was added to the above solution using a pipette, and the mixture was stirred for 30 min. Immediately afterward, the mixture was transferred to a sealed 20 mL stainless steel autoclave lined with polytetrafluoroethylene. The temperature was raised to 160°C and maintained for crystallization for 3 days. Afterward, the power was turned off and the mixture was allowed to cool slowly to room temperature. The residue was filtered off, and the light green transparent mother liquor was transferred to a beaker, sealed with plastic wrap, and allowed to stand at room temperature for 3-4 days to obtain light green blocky crystals. The crystals were filtered and dried, with a yield of 58.73% (based on Mo). Elemental analysis: C 49 H 70 Mo9N7O 33 P (experimental values): C 27.10, H 3.00, Mo 39.70, N 4.50, O 24.30, P 1.40%; (theoretical values): C 27.07, H 2.80, Mo 40.01, N 4.59, O 23.56, P 1.47%. FT-IR (KBr pellet, v ): 754(w), 854(w), 935(s), 1054(s), 1544(s), 1464(m), 3073(m) cm -1 .

[0022] The structure of the compound is as follows Figure 1 As shown, X-ray single-crystal diffraction analysis results indicate that the compound crystallizes in a triclinic matrix. P- Space group 1. Its asymmetric unit consists of a three-vacant A-α Keggin-type polyanion [PMo9O] with a terminal oxygen replaced by 3-ethylpyridine. 31 (C7H9N)3] 3- (Abbreviated as [PMo9O]) 31 (3-EP)3] 3-3-EP (3-ethylpyridine) consists of 2 free water molecules, 3 free and protonated 3-ethylpyridine molecules, and 1 unprotonated 3-ethylpyridine molecule. In the compound, the parent [PMo9O] 31 (3-EP)3] 3- It is [A-α-PMo9O] 34 ] 9- This compound is formed after the oxo active site is replaced by 3-ethylpyridine. The absence of chirality in the compound is due to the significant steric hindrance of 3-ethylpyridine, which restricts the rotation and torsion of the Mo-N single bond.

[0023] There are many complex intermolecular forces in the compound, such as the uncoordinated 3-ethylpyridine and the polyacid anion cluster [PMo9O]. 31 (3-EP)3] 3- Numerous hydrogen bonds exist between the shell oxygen atoms, extending the asymmetric unit to higher dimensions. A protonated 3-ethylpyridine cation resides between the two polyacid clusters, linked to [PMo9O] via C22 and C32 on 3-ethylpyridine. 31 (3-EP)3] 3- The O12 and O26 on the chain form hydrogen bonds C22-H22…O12 (3.071(8) Å, 125°) and C32-H32…O26 (3.328(8) Å, 138°), with the two hydrogen bonds alternating, extending the asymmetric unit infinitely into a 1D chain, denoted as 1D. a The opposite 1D chain is 1D. -a The two opposing 1D chains are connected by hydrogen bonds between C22 and O30, C22-H22…O30 (3.291(9) Å, 140°), as shown in the figure. Figure 2 As shown in a. The two connected 1D chains are then further linked to [PMo9O] via C35 and C3 on another free 3-ethylpyridine. 31 (3-EP)3] 3- The O19 and O27 on the anion cluster form hydrogen bonds C35-H35…O19 (3.304(11) Å, 159°) and C3-H3B…O27 (3.376(18) Å, 173°), extending the 1D chain into a 2D layer, such as... Figure 2 As shown in b. Finally, the 2D layer is extended into a 3D network framework by forming hydrogen bonds C28-H28B…O27 (3.379(8) Å, 172°) between the C28 on the coordinated 3-ethylpyridine and the shell oxygen atom O27 on the polyacid anion cluster, as shown in b. Figure 3 As shown.

[0024] Structural confirmation of the compound 1. X-ray photoelectron spectroscopy analysis like Figure 4 As shown, bond valence calculations (BVS) indicate that all Mo centers in the compound are in the +6 oxidation state. Furthermore, X-ray photoelectron spectroscopy (XPS) characterization further confirmed the oxidation states. Figure 4 a). The Mo 3d XPS spectrum of the compound shows two peaks at 232.5 eV and 235.6 eV, corresponding to Mo, respectively. 6+ 3D 5 / 2 and Mo 6+ 3D 3 / 2 Energy levels. Full-spectrum analysis, as expected, revealed that the compound remains a p-containing heteropolyacid, such as... Figure 4 As shown in b. The XPS analysis results are consistent with the BVS calculation results; therefore, the molecular formula of the compound should be [P]. V Mo Ⅵ 90 31 (3-EP)3]·(3-HEP)3∙(3-EP)∙(H2O)2.

[0025] 2. X-ray powder diffraction analysis like Figure 5 As shown, we used X-ray powder diffraction (PXRD) analysis to test the stability of the compound. The crystals were placed in air for more than 30 days before the corresponding experiments were conducted. Figure 5 It can be seen that the spectrum obtained from the experiment is in good agreement with the simulated spectrum obtained from the single-crystal X-ray diffraction structure analysis. The difference in peak intensity is due to the different orientation of the sample during the test, which means that the compound has good phase purity, is very stable in air, and the framework has not changed.

[0026] 3. Thermogravimetric analysis To understand the thermal stability of the compound, we used thermogravimetric analysis (TG) and differential thermal analysis (DTG) to study the thermal behavior of the title compound. Under nitrogen protection, at a heating rate of 10 °C / min, and in a temperature range of 25–900 °C, as follows... Figure 6 As shown, the weight loss of the compound can be divided into four stages. The first three stages are continuous processes. The title compound begins to lose weight at ~98 °C (center of the DTG curve) and continues until ~544 °C, with a weight loss of 36% (calculated value 35.41%). This is attributed to the loss of 2 H₂O, 3 coordinated 3-ethylpyridines, and 4 free 3-ethylpyridines. Continued heating of the compound revealed further weight loss, corresponding to the collapse of the [PMo9] parent structure.

[0027] 4. IR Analysis We used a Nicolet 360 spectrometer to record the compounds at wavelengths of 400–4000 cm⁻¹. -1Infrared spectrum within the range, such as Figure 7 As shown. The infrared spectrum of the compound exhibits characteristic absorption peaks of the 3-ethylpyridine ligand and polyacids, in the 700–1100 cm⁻¹ range. -1 The region exhibits a typical Keggin anion band at 1054 cm⁻¹. -1 The peak at 935 cm⁻¹ can be attributed to the stretching vibration of the PO bond. -1 The peak at that location is attributed to Mo-O t Key (O) t The stretching vibration of oxygen (terminal oxygen), 845 cm -1 The peak at that location corresponds to Mo-O b -Mo key (O b The stretching vibration of the bridging oxygen (754 cm) -1 The peak that appears is Mo-O c -Mo key (O c The stretching vibrations of the central oxygen (PMo) and these characteristic peaks are related to the raw material [PMo]. 12 (1065, 965, 870, 780 cm) -1 Compared to shifting to lower wavenumbers, this is because the Mo-N bond interaction is stronger than the Mo-O bond, and these bonds are weakened to some extent. As we hypothesized, 3-ethylpyridine replaces the terminal oxygen atom, directly bonding to the metallic Mo atom. Furthermore, for ethyl-substituted pyridine derivatives, the wavenumbers are typically in the 1300-1000 cm⁻¹ range. -1 and 900-700 cm -1 In-plane and out-of-plane bending vibrations of the CH bond were observed in the region, with the highest wavenumber reaching 3460 cm⁻¹. -1 The characteristic peak at 3073 cm⁻¹ corresponds to the OH bond vibration of the H₂O molecule. -1 The absorption band at 2974 cm⁻¹ can be considered as the absorption peak of the stretching vibration of the CH bond in unsaturated carbon atoms, while the absorption band at 2974 cm⁻¹ can be considered as the absorption peak of the stretching vibration of the CH bond in unsaturated carbon atoms. -1 This is the absorption peak of the stretching vibration of the CH bond in saturated carbon atoms, at 1600 cm⁻¹. -1 It is an NH bond bending vibration, at 1544 and 1464 cm⁻¹. -1 The characteristic peaks at these locations represent the stretching vibrations of C=C and C=N bonds, which are characteristic infrared peaks of 3-ethylpyridine. The above analysis confirms the presence of a Keggin-type structure and a 3-ethylpyridine ligand in the compound, and demonstrates that the ligand and the anionic cluster are covalently coordinated. The results agree well with the structural analysis results from single-crystal X-ray diffraction.

[0028] 5. UV-vis analysis of compounds The optical properties of compounds are studied by measuring ultraviolet-visible (UV-vis) spectra in aqueous solutions. Figure 8). Matrix [PMo 12 It exhibits a strong absorption band at 209 nm, which is due to the terminal oxygen atoms merging into the molybdenum atoms (O). t The charge transfer transition of [PMo] leads to a ligand-centric π-π* transition in free 3-ethylpyridine at 261 nm. After complexation, the compound (the compound of this invention) exhibits a strong absorption band at 208 nm and a weaker absorption band at 260 nm, a value close to that of 3-ethylpyridine. 12 Compared to free 3-ethylpyridine, both showed a 1 nm blue shift, which can be attributed to the 3-ethylpyridine modification at the POM center.

[0029] 6. Electrochemical behavior We used a three-electrode system to test the electrochemical activity of the title compound in electrolyte solutions of 0.5 M H₂SO₄ and 0.1 M Na₂SO₄ at a scan rate of 50 mV / s. Within the potential range of -200 to 500 mV, the compound exhibited three pairs of reversible redox peaks: I / I', II / II', and III / III'. Three reduction peaks were observed at -74, +151, and +284 mV, and the average value of the reduction and oxidation peak potentials, E0, was [missing value]. 1 / 2 The values ​​were +60 mV (I / I'), +183 mV (II / II'), and +298 mV (III / III'), corresponding to the redox process of the Mo atom. Cyclic voltammetry (CV) results showed that [PMo9] is the active center. After five consecutive cycles, the voltammetric characteristics of the compound did not change significantly, indicating that the structure of the compound is stable under the experimental conditions discussed. Figure 9 As shown.

[0030] 7. Photocatalytic performance study Currently, the degradation and adsorption of organic dyes is an important branch of environmental research. We selected the organic dye methylene blue (MB) to evaluate the adsorption capacity of the title complex. The specific method is as follows: a 100 mg / L MB solution was used as the degradation substrate, and a 300 W xenon lamp was used as the visible light source for photocatalytic performance testing. 100 mg of the compound sample was added to the above solution, and the mixture was continuously magnetically stirred for 30 min in the dark at room temperature to allow MB to reach adsorption-desorption equilibrium. Then, 3-5 mL of the solution was taken and marked as sample 0. The xenon lamp was then turned on to carry out the photocatalytic degradation reaction. Samples were taken every 20 min, and the reaction lasted for 100 min, and the samples were marked as samples 1-5. After sampling, the samples were centrifuged at 3000 r / min for 20 min, and the absorbance of the supernatant was measured by ultraviolet-visible spectroscopy (UV-vis) to observe the change in organic dye concentration. The degradation rate of MB was calculated using the following formula: D = ( C 0- C t ) / C 0×100%. From Figure 10 As can be seen from Figure a, the color and absorption intensity of MB changed significantly with increasing adsorption time. The adsorption rate of the title compound for MB was 78.0%, indicating that the title compound has good adsorption capacity for the organic dye MB.

Claims

1. A compound, characterized in that: The molecular formula is [P V Mo Ⅵ 90 31 [(3-EP)3]·(3-HEP)3∙(3-EP)∙(H2O)2, and the compound crystallizes in the triclinic P-1 space group.

2. A method for preparing the compound according to claim 1, characterized in that: firstly, H3PMo... 12 O 40 Dissolve 13H₂O in ultrapure water, stir until completely dissolved, then add 3-ethylpyridine solution to the above solution using a pipette. H₃PMo 12 O 40 The addition ratio of 13H2O to 3-ethylpyridine solution was 0.2 g H3PMo. 12 O 40 ·13H2O / 1mL 3-ethylpyridine solution, under alkaline conditions, after stirring, immediately transfer the mixture to a sealed stainless steel high-pressure reactor lined with polytetrafluoroethylene, heat to 160 °C and maintain crystallization for 3 days, then turn off the power and allow it to cool slowly to room temperature, open the reactor, filter out the filter residue, seal and let stand to obtain green block crystals.

3. The method for preparing the compound according to claim 2, characterized in that: After filtering out the residue, the light green and transparent mother liquor is transferred to a beaker, sealed with plastic wrap, and left to stand at room temperature for 3-4 days to obtain light green blocky crystals.

4. The use of the compound of claim 1 as a material for adsorbing organic dyes.

Images