Keggin type transition metal substituted polyacid and preparation method and application of Keggin type transition metal substituted polyacid assembly
By preparing Keggin-type transition metal-substituted polyacids and self-assembling them with surfactants to form DODAB-V-POM assemblies, the problems of difficult recovery of homogeneous catalysts and high temperature and high pressure limitations were solved, realizing efficient CO2 cycloaddition reactions under mild conditions, improving catalytic activity and expanding the application forms of catalysts.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-26
- Publication Date
- 2026-03-27
AI Technical Summary
Existing homogeneous catalysts have problems such as difficulty in recovery, easy contamination of products, and poor catalyst reproducibility in the cycloaddition reaction of CO2 with epoxides. Furthermore, the high temperature and high pressure conditions limit their large-scale application.
Keggin-type transition metal-substituted polyacids were prepared by a one-step hydrothermal or solvent method. The surfactant bis(octadecyldimethylammonium bromide) (DODAB) was coated by ion exchange and self-assembled under a good solvent-poor solvent assembly strategy to form a DODAB-V-POM assembly with a regular structure, which was then used as a heterogeneous catalyst for CO2 cycloaddition reactions.
It achieves efficient catalytic reaction of CO2 and epoxides under mild conditions. The catalyst has a stable structure, is easy to separate and recover, and has significantly improved catalytic activity. It is suitable for the generation of cyclic carbonates under photothermal synergistic conditions and has good prospects for industrial application.
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Figure CN121732229A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst preparation technology, specifically to a method and application for preparing Keggin-type transition metal substituted polyacids and their assemblies. Background Technology
[0002] With the massive consumption of fossil fuels, atmospheric CO2 concentrations continue to rise, triggering global warming and a series of environmental problems. To achieve the "dual carbon" goal (carbon reduction and emission reduction), the efficient capture and resource utilization of CO2 has become a research hotspot. Among these methods, converting CO2 with epoxides into cyclic carbonates via cycloaddition reactions is considered a promising carbon reduction pathway due to its 100% atom economy. The resulting cyclic carbonates have wide applications in lithium-ion battery electrolytes, fine chemical intermediates, and other fields.
[0003] However, this reaction typically requires harsh conditions of high temperature and high pressure, resulting in high energy consumption and limiting its large-scale application. In recent years, research on solar-driven CO2 cycloaddition reactions has gradually emerged, offering the possibility of achieving CO2 conversion under mild conditions. However, due to the thermodynamic stability and chemical inertness of the CO2 molecule itself, efficient catalytic systems usually need to possess multiple active sites, including Lewis acids, Lewis bases, and nucleophilic halide anions (such as I⁻, Br⁻, Cl⁻), to synergistically promote the ring-opening of epoxides and the insertion of CO2.
[0004] Currently, commonly used homogeneous co-catalysts such as tetrabutylammonium bromide (TBAB) can provide the necessary basic sites and halide ions, but they suffer from problems such as difficulty in recovery, easy product contamination, and poor catalyst reproducibility, and are also not conducive to in-depth research on the reaction mechanism. Therefore, developing heterogeneous catalysts with stable structures, well-defined active sites, and easy separation and recovery has become the key to promoting the development of this technology. Summary of the Invention
[0005] This invention aims to provide a method for preparing Keggin-type transition metal substituted polyacids and their assemblies, and their applications, providing a heterogeneous catalyst with stable structure, well-defined active sites, and easy separation and recovery for the cycloaddition reaction of CO2 and epoxides.
[0006] To solve the above technical problems, the specific solution adopted in this invention is as follows: a method for preparing Keggin-type transition metal substituted polyacids, wherein Fe, Cu or V are partially substituted at different sites of the Keggin-type polyacids using a one-step hydrothermal method or solvent method to obtain Keggin-type transition metal substituted polyacids.
[0007] Preferably, it includes the following steps: 1) Dissolve Keggin-type trivacant phosphotungstic acid in deionized water, then add vanadium oxysulfate, and stir the reaction to obtain a trivacant polyacid precursor solution: 2) Heat the tri-vacancy polyacid precursor solution prepared in step 1) to 60-80℃ and stir, then add liquid bromine until the solution changes color, then add potassium chloride; raise the temperature to 80-100℃ and stir until completely dissolved, then obtain orange crystals by hot filtration. 3) Place the orange crystals obtained in step 2) in an acidic environment at 60-80°C. o Recrystallization from deionized water, repeated 2-4 times, yields orange crystals that are Keggin-type vanadium-substituted polyacids K5[PV2W]. 10 O 40 ], abbreviated as V-POM.
[0008] Preferably, the preparation method of Keggin-type tri-vacancy phosphotungstenate in step 1) is as follows: dissolve sodium tungstate in deionized water, then add phosphoric acid and glacial acetic acid, stir until the solution changes color, and then filter and modify the solution to obtain Keggin-type tri-vacancy phosphotungstenate.
[0009] Preferably, in step 3), during the recrystallization process, phosphoric acid and sodium hydroxide are used as buffer solutions to adjust the pH of the recrystallization solution to 2-4.
[0010] A method for preparing a Keggin-type transition metal-substituted polyacid assembly involves using an ion exchange method to coat the anionic cluster of a Keggin-type transition metal-substituted polyacid prepared by any of the above-mentioned methods with the surfactant dioctadecyldimethylammonium bromide. The assembly is then self-assembled using a good solvent-poor solvent assembly strategy to obtain the Keggin-type transition metal-substituted polyacid assembly.
[0011] Preferably, it includes the following steps: 1) Dissolve dioctadecyldimethylammonium bromide in chloroform to obtain solution A; 2) Dissolve a Keggin-type transition metal-substituted polyacid in deionized water to obtain solution B; 3) Under stirring, add solution A obtained in step 1) dropwise to solution B obtained in step 2), and after continuous stirring, obtain Keggin-type transition metal substituted polyacid group assembly powder by evaporating the solvent; 4) Dissolve the Keggin-type transition metal substituted polyacid group assembly powder obtained in step 3) in chloroform, then add acetone, and finally obtain the Keggin-type transition metal substituted polyacid group assembly by evaporating the solvent. Alternatively, dissolve the Keggin-type transition metal substituted polyacid group assembly powder obtained in step 3) in acetonitrile, add dichloromethane, and finally obtain the Keggin-type transition metal substituted polyacid group assembly by evaporating the solvent. Alternatively, dissolve the Keggin-type transition metal substituted polyacid group assembly powder obtained in step 3) in chloroform, add toluene, and finally obtain the Keggin-type transition metal substituted polyacid group assembly by evaporating the solvent.
[0012] Preferably, in step 1), the dissolved mass of dioctadecyldimethylammonium bromide is based on the maximum mass that can be completely dissolved.
[0013] Preferably, in step 3), solution A is added in excess to solution B.
[0014] A Keggin-type transition metal-substituted polyacid group assembly is prepared by any of the above-mentioned methods for preparing Keggin-type transition metal-substituted polyacid group assemblies.
[0015] The above-mentioned application of Keggin-type transition metal-substituted polyacid group assemblies in the photothermal carbon dioxide cycloaddition reaction involves dispersing the Keggin-type transition metal-substituted polyacid group assemblies as catalysts in an epoxide solvent, and then supplying carbon dioxide for cycloaddition reaction under light and heating conditions.
[0016] Based on the above technical solutions, the present invention has the following beneficial effects: (1) This invention employs a stepwise solvothermal method to achieve the controllable preparation of Keggin-type transition metal-substituted polyacids (V-POMs) under mild conditions. Compared with traditional high-temperature, high-pressure, or electrochemical methods, this method is simple to operate, has low energy consumption, high yield, and high product purity, and has good economic efficiency and scalability.
[0017] (2) By co-assembling quaternary ammonium salt surfactant (DODAB) with V-POM, a heterogeneous assembly with an ordered nanosphere structure was constructed. This structure not only effectively avoids the problems of active component dissolution and structural collapse in traditional homogeneous catalytic systems, but also significantly improves the stability and recyclability of the catalyst in the reaction medium.
[0018] (3) The polyoxometalates (POMs) used in this invention are a class of metal-oxygen cluster compounds with well-defined structures. They have unique band structures and excellent photoresponse performance, showing broad prospects in the field of photocatalysis. In particular, by introducing transition metals such as V, Cu, and Fe for substitution, their redox properties and surface acidity can be further regulated, enhancing light absorption capacity and introducing new reaction sites, thereby significantly improving the activation capacity and catalytic reaction efficiency of CO2 molecules.
[0019] (4) By adjusting the DODAB feeding ratio, two assembly precursors were successfully prepared: (DODA)5PV2W 10 O 40 With (DODA)6PV2W 10 O 40 ∙Br. The latter, due to the introduction of nucleophilic Br⁻, exhibits excellent performance in the photothermal synergistic catalytic CO₂ cycloaddition reaction without the need for an external co-catalyst, with its catalytic activity being approximately 10 times that of the former.
[0020] (5) This invention breaks through the current limitation that polyacid-based catalysts mainly rely on COFs, MOFs, g-C3N4 and other supports for immobilization, and proposes a simple construction method based on a self-assembly strategy. In addition, POM can self-assemble with quaternary ammonium salt surfactants through electrostatic interactions to construct nanomaterials with specific morphologies and interface structures, providing a new idea for designing multifunctional composite catalytic materials, significantly reducing the catalyst preparation cost, and expanding the application forms of POM in heterogeneous catalysis.
[0021] (6) The prepared DODAB-V-POM assembly can efficiently catalyze the reaction of various epoxides with CO2 to generate corresponding cyclic carbonates under photothermal synergistic conditions at room temperature and pressure, showing good prospects for industrial application. Compared with pure thermal catalysis, the catalytic performance of this assembly under photothermal synergistic conditions is improved by nearly 2 times, and it shows excellent universality and structural stability for various substrates such as epichlorohydrin, epibromopropane, and glycidyl ether, and has good potential for practical application. Attached Figure Description
[0022] Figure 1 The preparation of Na8H[PW9O] in Example 1 is as follows. 34 SEM image of [image missing]; Figure 2 The Na8H[PW9O] prepared in Example 1 34 SEM-EDS plot; Figure 3 The preparation of Na8H[PW9O] in Example 1 is as follows. 34 XRD pattern of ]; Figure 4 The preparation of Na8H[PW9O] in Example 1 is as follows. 34 FTIR plot of ]; Figure 5 This is the XRD pattern of V-POM prepared in Example 2; Figure 6 This is the Raman spectrum of V-POM prepared in Example 2; Figure 7The (DODA)5PV2W prepared in Example 3 is... 10 O 40 SEM image of the assembly; Figure 8 The (DODA)6PV2W prepared in Example 4 is... 10 O 40 • SEM image of Br; Figure 9 These are thermogravimetric maps of V-POM and DODAB-V-POM prepared in Examples 2-4; Figure 10 These are the DRS diagrams of V-POM and DODAB-V-POM prepared in Examples 2-4; Figure 11 It is the (DODA)6PV2W scheme in Example 4. 10 O 40 ∙TEM image of Br; Figure 12 It is the (DODA)6PV2W scheme in Example 5. 10 O 40 ∙TEM image of the Br assembly; Figure 13 It is the (DODA)6PV2W scheme in Example 6. 10 O 40 ∙TEM image of the Br assembly; Figure 14 These are SAXS diagrams of the DODAB-V-POM assemblies in Examples 3 and 4; Figure 15 These are FTIR images of the V-POM and DODAB-V-POM assemblies in Examples 2-4; Figure 16 It is (DODA)5PV2W in embodiments 7 and 8. 10 O 40 Assembly and (DODA)6PV2W 10 O 40 • Performance comparison of Br assemblies under photothermal catalysis; Figure 17 It is the (DODA)6PV2W scheme in Example 9. 10 O 40 • Performance comparison of Br assemblies under photothermal and thermocatalytic conditions; Figure 18 In Example 10, the scheme is (DODA)6PV2W 10 O 40 • Universality test diagram of Br assembly; Figure 19 It is (DODA)6PV2W in embodiments 7-10 of this invention.10 O 40 • Mechanism diagram of Br assembly in photothermal catalytic CO2 cycloaddition reaction; Figure 20 This is a morphological image of the DODAB-V-POM assembly prepared according to the present invention. Detailed Implementation
[0023] This invention discloses a method for preparing and applying Keggin-type transition metal-substituted polyacids and their assemblies. The Keggin-type transition metal-substituted polyacids have the general formula X-POM (molecular formula [PM...). 11 XO 40 ] n- Where M is W or Mo, and X is a transition metal such as Fe, Cu, or V. The core of this invention lies in: first, precisely substituting metals such as V, Cu, and Fe at specific sites in a polyacid using a stepwise method; then, coating the polyacid (taking vanadium-substituted V-POM as an example) anionic cluster with the surfactant dioctadecyldimethylammonium bromide (DODAB) using an ion exchange method; finally, self-assembly under a "good solvent-poor solvent" assembly strategy to obtain a DODAB-V-POM assembly with regular morphology and novel structure.
[0024] This invention keyly utilizes a non-equilibrium ion exchange method to synergistically anchor long-chain cations (DODA⁺) and nucleophilic groups (Br⁻) to the periphery of polyacid anion clusters through electrostatic interactions, thereby forming a regular structure through self-assembly in a two-phase organic solvent. Tests show that this assembly simultaneously possesses Lewis acidic sites (derived from the polyacid framework and substituted transition metals) and Lewis basic sites (derived from nitrogen atoms in the surfactant), and incorporates a nucleophilic Br⁻ that promotes ring-opening of epoxides in CO₂ cycloaddition reactions, thus constituting a bifunctional active site system. Therefore, this assembly exhibits excellent catalytic conversion and substrate universality in photothermal CO₂ cycloaddition reactions. Furthermore, the regular and ordered "coating" and "protection" of the polyacid anion clusters by the surfactant further enhances the exposure rate of active sites and the overall structural stability of the catalyst.
[0025] To achieve the above-mentioned objectives, the specific preparation and application of this invention are described below: In a first aspect, the present invention provides a method for preparing Keggin-type vanadium-substituted polyacids (V-POM).
[0026] The method mainly includes the following steps: Preparation of Keggin-type tri-vacancy phosphotungstenate precursor: Weigh 10-15 g of sodium tungstate (Na2WO4) and dissolve it in 10-15 mL of deionized water. After stirring until completely dissolved, add 0.3-0.5 mL of 85% phosphoric acid (H3PO4) and 2.0-2.5 mL of 99% glacial acetic acid (C2H4O2). Stir vigorously until the solution turns milky white, then filter and dry the resulting solid at 60 °C to obtain tri-vacancy Keggin-type phosphotungstenate Na8H[PW9O] 34 ].
[0027] Preparation of vanadium oxysulfate (VOSO4) aqueous solution: Weigh 0.4-0.6 g of VOSO4 solid, add 1.5-2 mL of deionized water, stir until completely dissolved, and set aside for use.
[0028] Vanadium metal substitution reaction: Weigh 3-5 g of Na8H[PW9O] prepared in step 1. 34 Add 6-10 mL of deionized water and dissolve completely. Then, while stirring at 400-600 rpm, slowly add the VOSO4 aqueous solution prepared in step 2 dropwise over 8-10 minutes. Continue stirring for 30-60 minutes to obtain a purplish-black trivacurized polyacid precursor solution.
[0029] Oxidation and crystallization: Heat the mixture obtained in step 3 to 60-80℃ and stir for 1-2 hours. Then, add 2-4 mL of liquid bromine (Br2) dropwise until the solution changes from black to clear orange. Stop adding immediately. Then, add 2-3 g of potassium chloride (KCl), raise the temperature to 80-100℃, stir until completely dissolved, and then perform hot filtration to obtain orange crystals.
[0030] Purification: The orange crystals obtained in step 4 were dissolved in acidic deionized water (pH 2-4, pH adjusted using 0.5 M phosphoric acid and 0.1 M sodium hydroxide buffer) at 60-80℃ for recrystallization. This recrystallization process was repeated 2-4 times to finally obtain high-purity Keggin-type vanadium-substituted polyacid with the molecular formula K5[PV2W] 10 O 40 ], abbreviated as V-POM.
[0031] Secondly, the present invention provides a method for preparing a polyacid group assembly based on the above-mentioned V-POM.
[0032] The method mainly includes the following steps: Preparation of surfactant solution: Dissolve 0.3-0.5 g of dioctadecyldimethylammonium bromide (DODAB) in 15-20 mL of chloroform (CHCl3) and stir until completely dissolved to obtain solution A. The amount of DODAB added must ensure that its molar ratio with the subsequent V-POM is 5:1 or 6:1.
[0033] Preparation of polyacid aqueous solution: Dissolve 150-200 mg (i.e. 0.1-0.2 g) of V-POM prepared in the first aspect in 10-20 mL of deionized water to obtain solution B.
[0034] Ion exchange and composite: Solution A was added dropwise to solution B while stirring at 400-600 rpm for 1-2 hours. The mixture was then placed in a fume hood and allowed to stand until the solvent had completely evaporated, yielding DODAB-V-POM composite powder.
[0035] By adjusting the molar ratio of DODAB to V-POM, two different assembly precursors can be obtained: when the molar ratio is 5:1, the precursor with the molecular formula (DODA)5PV2W is obtained. 10 O 40 The complex; when the molar ratio is 6:1, the molecular formula (DODA)6PV2W is obtained. 10 O 40 ∙Br complex, which retains nucleophilic bromide ions (Br⁻) due to the introduction of excess DODAB.
[0036] Self-assembly: Weigh 20-50 mg of the DODAB-V-POM composite powder obtained in step 3, dissolve it in 2-4 mL of chloroform (a good solvent), and after it is completely dissolved, add 1-4 mL of acetone (a poor solvent) (alternatively, combinations of solvents with significantly different polarities, such as acetonitrile-dichloromethane or chloroform-toluene, can be used). After allowing the solvent to slowly evaporate, a DODAB-V-POM assembly with a regular nanosphere structure can be obtained.
[0037] Thirdly, the present invention provides the application of the above-mentioned DODAB-V-POM assembly in the photothermal catalytic CO2 cycloaddition reaction.
[0038] The specific application method is as follows: 20 mg of the assembled catalyst is dispersed in a reactor containing 2 mL of epoxide (such as epichlorohydrin) solvent, and CO2 gas at a pressure of 0.1 MPa is introduced into the system. Under room temperature initial conditions, a 300W xenon lamp is used as the light source for irradiation, and the reaction temperature is maintained by the heat energy converted from light energy, reaching a maximum of approximately 66°C. Samples can be taken periodically during the reaction to detect the amount of cyclic carbonates formed, in order to evaluate the catalytic performance. This assembled material exhibits excellent catalytic activity and versatility for various epoxide substrates, including epichlorohydrin, epibromopropane, and glycidyl ether.
[0039] The technical solution of the present invention will be described below through several embodiments. Unless otherwise specified, the experimental materials used in the embodiments below can be purchased from conventional biochemical reagent companies.
[0040] Example 1 (1) Weigh 12 g of sodium tungstate (Na2WO4) and dissolve it in 15 mL of deionized water, stirring until dissolved; (2) Add 0.3 mL of phosphoric acid (H3PO4) and 2.2 mL of glacial acetic acid (C2H4O2) to the solution prepared in step (1), and stir vigorously until the solution turns white; (3) Filter the white turbid solution obtained in step (2) under vacuum, 60 o After drying with C, Keggin-type tri-vacancy phosphotungstic acid salt Na8H[PW9O] is obtained. 34 Precursor, ready for use; (4) Weigh 0.4 g of solid VOSO4 into a 10 mL glass reaction flask, add 1.7 mL of deionized water, and stir until completely dissolved to obtain an aqueous solution of vanadium oxysulfate (VOSO4) for later use; (5) Weigh 3 g of the prepared Na8H[PW9O] 34 Add 6 mL of deionized water, and after it is completely dissolved, add vanadium oxysulfate (VOSO4) aqueous solution dropwise. The solution turns from purple to black. (6) Heat the black precursor mixture obtained in step (5) to 60°C. o C. After stirring for 1 h, add 2 mL of liquid bromine (Br2) dropwise until the solution changes from black to clear orange, then immediately stop. Next, add 2.5 g of potassium chloride (KCl) and raise the temperature to 80°C. o C. After stirring until completely dissolved, filter hot to obtain orange crystals; (7) Dissolve the orange crystals obtained in step (6) at pH=2 and temperature of 80°C. o Recrystallization of C in deionized water yields orange crystals, which are high-purity Keggin-type vanadium-substituted polyacid K5[PV2W]. 10 O40 ], abbreviated as V-POM.
[0041] (8) Dissolve 0.5 g of dioctadecyldimethylammonium bromide (DODAB) in 15 mL of chloroform (CHCl3) to obtain solution A; (9) Weigh 0.3 g of the recrystallized Keggin-type V-POM from step (7) and dissolve it in 10 mL of deionized water to obtain solution B; (10) Under stirring, add solution A obtained in step (8) dropwise to solution B obtained in step (9), stir continuously for 30 min, place in a fume hood, and obtain DODAB-V-POM after the solvent evaporates; (11) Weigh 10 mg of DODAB-V-POM powder obtained in step (3) and dissolve it in 4 mL of chloroform (CHCl3). After it is completely dissolved, add 4 mL of acetone and let the solvent evaporate to obtain the DODAB-V-POM assembly.
[0042] Figure 1 This embodiment prepares and synthesizes Na8H[PW9O] 34 SEM image of [image missing]; Figure 2 The Na8H[PW9O] prepared in this embodiment 34 SEM-EDS plot; Figure 3 The Na8H[PW9O] prepared in this embodiment 34 XRD pattern of ]; Figure 4 The Na8H[PW9O] prepared in this embodiment 34 FTIR plot of ].
[0043] Example 2 (1) Weigh 10 g of sodium tungstate (Na2WO4) and dissolve it in 15 mL of deionized water, stirring until dissolved; (2) Add 0.2 mL of phosphoric acid (H3PO4) and 2 mL of glacial acetic acid (C2H4O2) to the solution prepared in step (1), and stir vigorously until the solution turns white; (3) Filter the white turbid solution obtained in step (2) under vacuum, 60 o After drying with C, Keggin-type tri-vacancy phosphotungstic acid salt Na8H[PW9O] is obtained. 34 Precursor, ready for use; (4) Weigh 0.35 g of solid VOSO4 into a 10 mL glass reaction flask, add 1.7 mL of deionized water, and stir until completely dissolved to obtain an aqueous solution of vanadium oxysulfate (VOSO4) for later use. (5) Weigh 3 g of the prepared Na8H[PW9O] 34Add 6 mL of deionized water, and after it is completely dissolved, add vanadium oxysulfate (VOSO4) aqueous solution dropwise. The solution turns from purple to black. (6) Heat the black precursor mixture obtained in step (5) to 60°C. o C. After stirring for 1 h, add 2 mL of liquid bromine (Br2) dropwise until the solution changes from black to clear orange, then immediately stop. Next, add 2.5 g of potassium chloride (KCl) and raise the temperature to 80°C. o C. After stirring until completely dissolved, filter hot to obtain orange crystals; (7) Dissolve the orange crystals obtained in step (6) at pH=2 and temperature of 80°C. o Recrystallization of C in deionized water yields orange crystals, which are high-purity Keggin-type vanadium-substituted polyacid K5[PV2W]. 10 O 40 ], abbreviated as V-POM.
[0044] (8) Dissolve 0.3 g of dioctadecyl dimethyl ammonium bromide (DODAB) in 15 mL of chloroform (CHCl3) to obtain solution A; (9) Weigh 0.1 g of the recrystallized Keggin-type V-POM from step (7) and dissolve it in 10 mL of deionized water to obtain solution B; (10) Under stirring, add solution A obtained in step (8) dropwise to solution B obtained in step (9), stir continuously for 1 h, place in a fume hood, and obtain DODAB-V-POM after the solvent evaporates; (11) Weigh 20 mg of DODAB-V-POM powder obtained in step (3) and dissolve it in 2 mL of chloroform (CHCl3). After it is completely dissolved, add 2 mL of acetone and let the solvent evaporate to obtain the DODAB-V-POM assembly.
[0045] Figure 5 This is the XRD pattern of the V-POM prepared and synthesized in this embodiment; Figure 6 This is the Raman spectroscopy image of the V-POM prepared in this embodiment.
[0046] Example 3 (1) Weigh 10 g of sodium tungstate (Na2WO4) and dissolve it in 15 mL of deionized water, stirring until dissolved; (2) Add 0.2 mL of phosphoric acid (H3PO4) and 2 mL of glacial acetic acid (C2H4O2) to the solution prepared in step (1), and stir vigorously until the solution turns white; (3) Filter the white turbid solution obtained in step (2) under vacuum, 60 o After drying with C, Keggin-type tri-vacancy phosphotungstic acid salt Na8H[PW9O] is obtained.34 Precursor, ready for use; (4) Weigh 0.35 g of solid VOSO4 into a 10 mL glass reaction flask, add 1.7 mL of deionized water, and stir until completely dissolved to obtain an aqueous solution of vanadium oxysulfate (VOSO4) for later use. (5) Weigh 3 g of the prepared Na8H[PW9O] 34 Add 6 mL of deionized water, and after it is completely dissolved, add vanadium oxysulfate (VOSO4) aqueous solution dropwise. The solution turns from purple to black. (6) Heat the black precursor mixture obtained in step (5) to 60°C. o C. After stirring for 1 h, add 2 mL of liquid bromine (Br2) dropwise until the solution changes from black to clear orange, then immediately stop. Next, add 2.5 g of potassium chloride (KCl) and raise the temperature to 80°C. o C. After stirring until completely dissolved, filter hot to obtain orange crystals; (7) Dissolve the orange crystals obtained in step (6) at pH=2 and temperature of 80°C. o Recrystallization of C in deionized water yields orange crystals, which are high-purity Keggin-type vanadium-substituted polyacid K5[PV2W]. 10 O 40 ], abbreviated as V-POM.
[0047] (8) Dissolve 0.32 g of dioctadecyldimethylammonium bromide (DODAB) in 15 mL of chloroform (CHCl3) to obtain solution A; (9) Weigh 0.28 g of the recrystallized Keggin-type V-POM from step (7) and dissolve it in 20 mL of deionized water to obtain solution B; (10) While stirring, add solution A obtained in step (8) dropwise to solution B obtained in step (9), continue stirring for 1 h, place in a fume hood, and after the solvent evaporates, obtain (DODA)5PV2W 10 O 40 ; (11) Weigh 20 mg of (DODA)5PV2W obtained in step (3). 10 O 40 The powder was dissolved in 2 mL of chloroform (CHCl3). After complete dissolution, 2 mL of acetone was added, and the solvent was allowed to evaporate to obtain (DODA)5PV2W. 10 O 40 (DODAB-V-POM) assembly.
[0048] Figure 7 This embodiment prepares and synthesizes (DODA)5PV2W. 10 O40 Thermogravimetrics; Figure 8 This is the (DODA)5PV2W prepared in this embodiment. 10 O 40 SEM image; Figure 10 This is the (DODA)5PV2W prepared in this embodiment. 10 O 40 DRS diagram of the assembly; Figure 12 This is the (DODA)5PV2W prepared in this embodiment. 10 O 40 SAXS diagram of the assembly; Figure 13 This is the (DODA)5PV2W prepared in this embodiment. 10 O 40 FTIR plot of the assembly.
[0049] Example 4 (1) Weigh 10 g of sodium tungstate (Na2WO4) and dissolve it in 15 mL of deionized water, stirring until dissolved; (2) Add 0.2 mL of phosphoric acid (H3PO4) and 2 mL of glacial acetic acid (C2H4O2) to the solution prepared in step (1), and stir vigorously until the solution turns white; (3) Filter the white turbid solution obtained in step (2) under vacuum, 60 o After drying with C, Keggin-type tri-vacancy phosphotungstic acid salt Na8H[PW9O] is obtained. 34 Precursor, ready for use; (4) Weigh 0.35 g of solid VOSO4 into a 10 mL glass reaction flask, add 1.7 mL of deionized water, and stir until completely dissolved to obtain an aqueous solution of vanadium oxysulfate (VOSO4) for later use. (5) Weigh 3 g of the prepared Na8H[PW9O] 34 Add 6 mL of deionized water, and after it is completely dissolved, add vanadium oxysulfate (VOSO4) aqueous solution dropwise. The solution turns from purple to black. (6) Heat the black precursor mixture obtained in step (5) to 60°C. o C. After stirring for 1 h, add 2 mL of liquid bromine (Br2) dropwise until the solution changes from black to clear orange, then immediately stop. Next, add 2.5 g of potassium chloride (KCl) and raise the temperature to 80°C. o C. After stirring until completely dissolved, filter hot to obtain orange crystals; (7) Dissolve the orange crystals obtained in step (6) at pH=2 and temperature of 80°C. o Recrystallization of C in deionized water yields orange crystals, which are high-purity Keggin-type vanadium-substituted polyacid K5[PV2W]. 10 O40 ], abbreviated as V-POM.
[0050] (8) Dissolve 0.38 g of dioctadecyldimethylammonium bromide (DODAB) in 15 mL of chloroform (CHCl3) to obtain solution A; (9) Weigh 0.28 g of the recrystallized Keggin-type V-POM from step (7) and dissolve it in 20 mL of deionized water to obtain solution B; (10) While stirring, add solution A obtained in step (8) dropwise to solution B obtained in step (9), continue stirring for 1 h, place in a fume hood, and after the solvent evaporates, obtain (DODA)6PV2W 10 O 40 ∙Br; (11) Weigh 20 mg of (DODA)6PV2W obtained in step (3). 10 O 40 · Br powder was dissolved in 2 mL of chloroform (CHCl3). After complete dissolution, 2 mL of acetone was added, and the solvent was allowed to evaporate to obtain (DODA)6PV2W. 10 O 40 ∙Br (DODAB-V-POM) assembly.
[0051] Figure 7 This embodiment prepares and synthesizes (DODA)6PV2W. 10 O 40 • Thermogravimetric diagram of Br; Figure 9 This is the (DODA)6PV2W prepared in this embodiment. 10 O 40 • SEM image of the Br assembly; Figure 10 This is the (DODA)6PV2W prepared in this embodiment. 10 O 40 • DRS diagram of the Br assembly; Figure 11 This is the (DODA)6PV2W prepared in this embodiment. 10 O 40 ∙TEM image of the Br assembly; Figure 12 This is the (DODA)6PV2W prepared in this embodiment. 10 O 40 • SAXS diagram of the Br assembly; Figure 13 This is the (DODA)6PV2W prepared in this embodiment. 10 O 40 ∙FTIR plot of the Br assembly.
[0052] Example 5 (1) Weigh 10 g of sodium tungstate (Na2WO4) and dissolve it in 15 mL of deionized water, stirring until dissolved; (2) Add 0.2 mL of phosphoric acid (H3PO4) and 2 mL of glacial acetic acid (C2H4O2) to the solution prepared in step (1), and stir vigorously until the solution turns white; (3) Filter the white turbid solution obtained in step (2) under vacuum, 60 o After drying with C, Keggin-type tri-vacancy phosphotungstic acid salt Na8H[PW9O] is obtained. 34 Precursor, ready for use; (4) Weigh 0.35 g of solid VOSO4 into a 10 mL glass reaction flask, add 1.7 mL of deionized water, and stir until completely dissolved to obtain an aqueous solution of vanadium oxysulfate (VOSO4) for later use. (5) Weigh 3 g of the prepared Na8H[PW9O] 34 Add 6 mL of deionized water, and after it is completely dissolved, add vanadium oxysulfate (VOSO4) aqueous solution dropwise. The solution turns from purple to black. (6) Heat the black precursor mixture obtained in step (5) to 60°C. o C. After stirring for 1 h, add 2 mL of liquid bromine (Br2) dropwise until the solution changes from black to clear orange, then immediately stop. Next, add 2.5 g of potassium chloride (KCl) and raise the temperature to 80°C. o C. After stirring until completely dissolved, filter hot to obtain orange crystals; (7) Dissolve the orange crystals obtained in step (6) at pH=2 and temperature of 80°C. o Recrystallization of C in deionized water yields orange crystals, which are high-purity Keggin-type vanadium-substituted polyacid K5[PV2W]. 10 O 40 ], abbreviated as V-POM.
[0053] (8) Dissolve 0.38 g of dioctadecyldimethylammonium bromide (DODAB) in 15 mL of chloroform (CHCl3) to obtain solution A; (9) Weigh 0.28 g of the recrystallized Keggin-type V-POM from step (7) and dissolve it in 20 mL of deionized water to obtain solution B; (10) While stirring, add solution A obtained in step (8) dropwise to solution B obtained in step (9), continue stirring for 1 h, place in a fume hood, and after the solvent evaporates, obtain (DODA)6PV2W 10 O 40 ∙Br; (11) Weigh 20 mg of (DODA)6PV2W obtained in step (3). 10 O 40• Br powder was dissolved in 2 mL of acetonitrile. After complete dissolution, 2 mL of dichloromethane was added, and the solvent was allowed to evaporate to obtain (DODA)6PV2W. 10 O 40 ∙Br (DODAB-V-POM) assembly.
[0054] Figure 14 This is the (DODA)6PV2W prepared in this embodiment. 10 O 40 • SEM image of the Br assembly.
[0055] Example 6 (1) Weigh 10 g of sodium tungstate (Na2WO4) and dissolve it in 15 mL of deionized water, stirring until dissolved; (2) Add 0.2 mL of phosphoric acid (H3PO4) and 2 mL of glacial acetic acid (C2H4O2) to the solution prepared in step (1), and stir vigorously until the solution turns white; (3) Filter the white turbid solution obtained in step (2) under vacuum, 60 o After drying with C, Keggin-type tri-vacancy phosphotungstic acid salt Na8H[PW9O] is obtained. 34 Precursor, ready for use; (4) Weigh 0.35 g of solid VOSO4 into a 10 mL glass reaction flask, add 1.7 mL of deionized water, and stir until completely dissolved to obtain an aqueous solution of vanadium oxysulfate (VOSO4) for later use. (5) Weigh 3 g of the prepared Na8H[PW9O] 34 Add 6 mL of deionized water, and after it is completely dissolved, add vanadium oxysulfate (VOSO4) aqueous solution dropwise. The solution turns from purple to black. (6) Heat the black precursor mixture obtained in step (5) to 60°C. o C. After stirring for 1 h, add 2 mL of liquid bromine (Br2) dropwise until the solution changes from black to clear orange, then immediately stop. Next, add 2.5 g of potassium chloride (KCl) and raise the temperature to 80°C. o C. After stirring until completely dissolved, filter hot to obtain orange crystals; (7) Dissolve the orange crystals obtained in step (6) at pH=2 and temperature of 80°C. o Recrystallization of C in deionized water yields orange crystals, which are high-purity Keggin-type vanadium-substituted polyacid K5[PV2W]. 10 O 40 ], abbreviated as V-POM.
[0056] (8) Dissolve 0.38 g of dioctadecyldimethylammonium bromide (DODAB) in 15 mL of chloroform (CHCl3) to obtain solution A; (9) Weigh 0.28 g of the recrystallized Keggin-type V-POM from step (7) and dissolve it in 20 mL of deionized water to obtain solution B; (10) While stirring, add solution A obtained in step (8) dropwise to solution B obtained in step (9), continue stirring for 1 h, place in a fume hood, and after the solvent evaporates, obtain (DODA)6PV2W 10 O 40 ∙Br; (11) Weigh 20 mg of (DODA)6PV2W obtained in step (3). 10 O 40 ∙Br powder was dissolved in 2 mL of chloroform. After complete dissolution, 2 mL of toluene was added, and the solvent was allowed to evaporate to obtain (DODA)6PV2W. 10 O 40 ∙Br (DODAB-V-POM) assembly.
[0057] Figure 15 This is the (DODA)6PV2W prepared in this embodiment. 10 O 40 • SEM image of the Br assembly.
[0058] Example 7 The catalyst in this embodiment is (DODA)5PV2W prepared in Example 3. 10 O 40 The assembly process was carried out without the use of a catalyst, under visible light, and at room temperature and pressure.
[0059] (1) The prepared (DODA)5PV2W 10 O 40 The assemblies were added to the reaction system in different amounts; (2) The substrate is 1 mmol of epichlorohydrin; (3) Take samples after 4 h of reaction and test the conversion rate of the target chloropropylene carbonate; (4) The reaction was carried out under continuous visible light irradiation by a 300 W xenon lamp; (5) CO2 is introduced by connecting a gas bag containing pure CO2 after the reaction flask is evacuated.
[0060] Example 8 The catalyst in this embodiment is (DODA)6PV2W prepared in Example 4. 10 O 40• Br assembly, the system is carried out without the use of a catalyst, under visible light, and at room temperature and pressure.
[0061] (1) The prepared (DODA)6PV2W 10 O 40 • The Br assembly was added to the reaction system in different amounts; (2) The substrate is 1 mmol of epichlorohydrin; (3) Take samples after 4 h of reaction and test the conversion rate of the target chloropropylene carbonate; (4) The reaction was carried out under continuous visible light irradiation by a 300 W xenon lamp; (5) CO2 is introduced by connecting a gas bag containing pure CO2 after the reaction flask is evacuated.
[0062] Figure 16 It is (DODA)5PV2W in embodiments 7 and 8. 10 O 40 Assembly and (DODA)6PV2W 10 O 40 • Performance comparison of Br assemblies under photothermal catalysis; Example 9 In this embodiment, the catalyst used was (DODA)6PV2W prepared in Example 4. 10 O 40 • Br assembly.
[0063] (1) The synthesized (DODA)6PV2W obtained during preparation 10 O 40 • 20 mg of the Br assembly material was weighed out as a catalyst; (2) The substrate is 1 mmol of epichlorohydrin; (3) The sampling time interval was 1 h, and the reaction lasted for a total of 9 h; (4) The reaction was carried out under continuous visible light irradiation by a 300 W xenon lamp; (5) CO2 is introduced by connecting a gas bag containing pure CO2 after the reaction flask is evacuated.
[0064] Effects of different illumination conditions on the CO2 cycloaddition properties of epichlorohydrin The (DODA)6PV2W prepared in Example 4 10 O 40 • Br assembly, under the same catalyst dosage, sampling interval, and substrate concentration, with varying light conditions.
[0065] At the same room temperature, the sampling interval was 1 h, and a total of 9 h of sampling was conducted. The product was tested by an Agilent gas chromatograph to obtain the conversion rate of cyclochloropropene carbonate.
[0066] Repeat the above steps to prepare 20 mg (DODA) 6PV2W. 10 O 40 • The Br assembly was added to a 1 mmol epichlorohydrin solution and then continuously irradiated with visible light from a 300 W xenon lamp.
[0067] Repeat the above steps to prepare 20 mg (DODA) 6PV2W. 10 O 40 ∙The Br assembly was added to a 1 mmol epichlorohydrin solution and incubated in an oil bath at 66 °C.
[0068] Figure 17 This presents the results of the effects of visible light irradiation on photothermal and purely thermal catalysis on the CO2 cycloaddition performance in this invention. The comparison revealed that the catalytic performance under light irradiation is nearly twice that under thermal catalysis.
[0069] Example 10 In this embodiment, the catalyst used was (DODA)6PV2W prepared in Example 4. 10 O 40 • Br assembly.
[0070] (1) The synthesized (DODA)6PV2W obtained during preparation 10 O 40 • 20 mg of the Br assembly material was weighed out as a catalyst; (2) The substrate is 1 mmol of epichlorohydrin; (3) The sampling time interval was 1 h, and the reaction lasted for a total of 9 h; (4) The reaction was carried out under continuous visible light irradiation by a 300 W xenon lamp; (5) CO2 is introduced by connecting a gas bag containing pure CO2 after the reaction flask is evacuated.
[0071] CO2 cycloaddition properties of different substrates The (DODA)6PV2W prepared in Example 4 10 O 40 • Br assemblies were added to the reaction system under the same catalyst addition amount, the same sampling interval, the same substrate concentration, and the same light irradiation conditions, with the substrate types changed to epichlorohydrin, epibromopropane, and glycidyl ether, respectively.
[0072] With the addition of different substrates, epichlorohydrin, epibromopropane, and glycidyl ether were added to the system as reaction substrates to carry out CO2 cycloaddition experiments, and the conversion rates of cyclic carbonates corresponding to different substrates were obtained by testing with an Agilent gas chromatograph.
[0073] Repeat the above steps, in the reaction system (DODA)6PV2W 10 O 40 • The Br assembly was added at a rate of 20 mg, and the substrate was 1 mmol epichlorohydrin under continuous visible light irradiation with a 300 W xenon lamp.
[0074] Repeat the above steps, in the reaction system (DODA)6PV2W 10 O 40 • The Br assembly was added at a rate of 20 mg, and the substrate was 1 mmol of epichlorohydrin under continuous visible light irradiation with a 300 W xenon lamp.
[0075] Repeat the above steps, in the reaction system (DODA)6PV2W 10 O 40 • The Br assembly was added at a dose of 20 mg, and the substrate was 1 mmol glycidol under continuous visible light irradiation with a 300 W xenon lamp.
[0076] Figure 18 This invention demonstrates the ability of different substrate types to be converted into cyclic carbonates under the same conditions. Through comparison, it was found that the prepared (DODA)6PV2W... 10 O 40 • The Br assembly is universally applicable to different epoxides, but the conversion of different cyclic carbonates varies depending on the substrate substituents; Figure 19 It is (DODA)6PV2W in embodiments 7-10 of this invention. 10 O 40 • Mechanism diagram of the Br assembly in the photothermal catalytic CO2 cycloaddition reaction.
[0077] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.
[0078] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.
Claims
1. A method for preparing a Keggin-type transition metal-substituted polyacid, characterized in that: By using a one-step hydrothermal or solvent method, Fe, Cu, or V can be partially substituted at different sites in Keggin-type polyacids to obtain Keggin-type transition metal-substituted polyacids.
2. The method for preparing a Keggin-type transition metal-substituted polyacid as described in claim 1, characterized in that: Includes the following steps: 1) Dissolve Keggin-type trivacant phosphotungstic acid in deionized water, then add vanadium oxysulfate, and stir the reaction to obtain a trivacant polyacid precursor solution: 2) Heat the tri-vacancy polyacid precursor solution prepared in step 1) to 60-80℃ and stir, then add liquid bromine until the solution changes color, then add potassium chloride; raise the temperature to 80-100℃ and stir until completely dissolved, then obtain orange crystals by hot filtration. 3) Place the orange crystals obtained in step 2) in an acidic environment at 60-80°C. o Recrystallization from deionized water, repeated 2-4 times, yields orange crystals that are Keggin-type vanadium-substituted polyacids K5[PV2W]. 10 O 40 ], abbreviated as V-POM.
3. The method for preparing a Keggin-type transition metal-substituted polyacid as described in claim 2, characterized in that: The preparation method of Keggin-type tri-vacancy phosphotungstenate in step 1) is as follows: dissolve sodium tungstate in deionized water, then add phosphoric acid and glacial acetic acid, stir until the solution changes color, and then filter and modify it to obtain Keggin-type tri-vacancy phosphotungstenate.
4. The method for preparing a Keggin-type transition metal-substituted polyacid as described in claim 2, characterized in that: In step 3), during the recrystallization process, phosphoric acid and sodium hydroxide are used as buffer solutions to adjust the pH of the recrystallization solution to 2-4.
5. A method for preparing a Keggin-type transition metal-substituted polyacid group assembly, characterized in that: Using an ion exchange method, the surfactant dioctadecyldimethylammonium bromide is coated around the anionic cluster of a Keggin-type transition metal-substituted polyacid prepared by any of the methods described in claims 1-4. Then, the cluster is self-assembled under a good solvent-poor solvent assembly strategy to obtain a Keggin-type transition metal-substituted polyacid assembly.
6. The method for preparing a Keggin-type transition metal-substituted polyacid group assembly as described in claim 5, characterized in that: Includes the following steps: 1) Dissolve dioctadecyldimethylammonium bromide in chloroform to obtain solution A; 2) Dissolve a Keggin-type transition metal-substituted polyacid in deionized water to obtain solution B; 3) Under stirring, add solution A obtained in step 1) dropwise to solution B obtained in step 2), and after continuous stirring, obtain Keggin-type transition metal substituted polyacid group assembly powder by evaporating the solvent; 4) Dissolve the Keggin-type transition metal substituted polyacid group assembly powder obtained in step 3) in chloroform, then add acetone, and finally obtain the Keggin-type transition metal substituted polyacid group assembly by evaporating the solvent. Alternatively, dissolve the Keggin-type transition metal substituted polyacid group assembly powder obtained in step 3) in acetonitrile, add dichloromethane, and finally obtain the Keggin-type transition metal substituted polyacid group assembly by evaporating the solvent. Alternatively, dissolve the Keggin-type transition metal substituted polyacid group assembly powder obtained in step 3) in chloroform, add toluene, and finally obtain the Keggin-type transition metal substituted polyacid group assembly by evaporating the solvent.
7. The method for preparing a Keggin-type transition metal-substituted polyacid group assembly as described in claim 6, characterized in that: In step 1), the dissolved mass of dioctadecyldimethylammonium bromide is based on the maximum mass that can be completely dissolved.
8. The method for preparing a Keggin-type transition metal-substituted polyacid group assembly as described in claim 6, characterized in that: In step 3), an excess of solution A is added to solution B.
9. A Keggin-type transition metal-substituted polyacid group assembly, characterized in that: It is prepared by the preparation method of a Keggin-type transition metal substituted polyacid group assembly as described in any one of claims 5-8.
10. The application of the Keggin-type transition metal-substituted polyacid group assembly as described in claim 9, characterized in that: In the photothermal carbon dioxide cycloaddition reaction, a Keggin-type transition metal-substituted polyacid group assembly is dispersed as a catalyst in an epoxide solvent, and carbon dioxide is supplied to carry out the cycloaddition reaction under light and heating conditions.