An ionic metal-organic framework catalyst for CO2 cycloaddition reaction and its preparation method and application

Abstract

The present invention belongs to the field of catalyst preparation and application, and discloses an ionic metal-organic framework catalyst for CO2 cycloaddition reactions, its preparation method, and application. The catalyst is constructed from a linear dicarboxylic acid ligand containing an imidazolium substituent and a metal oxygen cluster Zr6O4(OH)4, with nucleophilic bromide ions dispersed as counteranions within the positively charged metal-organic framework. It has a classic UiO66 topological structure, a high specific surface area, and significant mesoporous characteristics. It can effectively catalyze the synthesis of cyclic carbonates from CO2 and epoxides under mild conditions without a co-catalyst, solvent, or other conditions. The catalyst is recyclable, and the product is easily separated and purified.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst preparation and application, and relates to an ionic metal-organic framework catalyst for CO2 cycloaddition reactions, its preparation method, and its application. Specifically, it relates to an ionic metal-organic framework catalyst covalently modified with an imidazolium substituent, its preparation method, and its application. Background Art

[0002] The continued emission of CO2 has exacerbated the greenhouse effect, causing various environmental problems and seriously threatening human survival. The chemical conversion of CO2 into other molecules can not only help alleviate the greenhouse effect, but also provide useful chemicals for humanity. The cycloaddition reaction of CO2 with epoxides has a 100% atomic utilization rate and is considered one of the most ideal reactions for the chemical fixation of CO2. At the same time, its product, cyclic carbonate, is a class of high value-added products. Currently, the catalysts used in industry for this reaction are mainly homogeneous catalysts, which have harsh reaction conditions, difficult product separation and purification, and difficult catalyst recycling. Therefore, the development of highly efficient and recyclable heterogeneous catalysts under mild conditions is of great significance.

[0003] In traditional heterogeneous catalyst systems, the cycloaddition reaction of CO2 and epoxides is usually carried out under the synergistic action of heterogeneous catalysts containing Lewis acid sites and nucleophilic halide ions. The reaction mechanism is roughly as follows: the Lewis acid sites in the heterogeneous catalyst can adsorb and activate the epoxide, and the nucleophilic reagent Br - or I - The ion reacts with the epoxy compound to form a haloalkoxy anion intermediate, which further adds to the CO2 molecule to form an alkylated carbonate anion intermediate. Finally, a cyclic carbonate is formed through an intramolecular ring closure reaction, and the nucleophilic halide ion is released, and the catalyst is regenerated and used for the next cycle. Therefore, when using Lewis acid heterogeneous catalysts, it is usually necessary to add additional nucleophilic reagents as co-catalysts, such as tetrabutylammonium bromide. However, the presence of homogeneous co-catalysts makes the product difficult to purify and also increases operating costs. Summary of the Invention

[0004] The present invention aims to solve the problem that traditional heterogeneous catalysts require the additional introduction of homogeneous co-catalysts such as tetrabutylammonium bromide during use. The invention provides an ionic metal-organic framework catalyst for the cycloaddition reaction of CO2 and epoxides, a preparation method thereof, and an application thereof. The prepared catalyst has a classic UiO-66 topological structure; it has a high specific surface area and significant mesoporous characteristics, can effectively catalyze the synthesis of cyclic carbonates from CO2 and epoxides under no co-catalyst, no solvent and mild conditions, can be recycled, and the product is easy to separate and purify.

[0005] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0006] An ionic metal-organic framework catalyst for CO2 cycloaddition reaction, characterized in that it is constructed from a linear dicarboxylic acid ligand containing an imidazolium substituent and a metal oxygen cluster Zr6O4(OH)4, named (Br - )R-Imidazolium-MOF-1; it has a classic UiO-66 topological structure.

[0007] The preparation method of the ionic metal-organic framework catalyst for CO2 cycloaddition reaction is as follows:

[0008] a. Add acetylacetone, anhydrous potassium carbonate, and N,N-diethylformamide (DMF) to a three-necked flask. Add carbon disulfide dropwise in an ice bath and stir at room temperature for 20 minutes. Then, add ethyl bromoacetate dropwise in an ice bath. After the addition is complete, stir at room temperature for 12 hours, heat to 50°C, and stir for 2 hours. After the reaction is complete, cool to room temperature and pour directly into deionized water. Filter and dry the precipitate to obtain ethyl 3,4-dimethylthiophenedicarboxylate. The molar ratio of acetylacetone, anhydrous potassium carbonate, carbon disulfide, and ethyl bromoacetate is 1:5:1:2. The amount of DMF used is 100 mL.

[0009] b. Add 3,4-dimethylthiophene dicarboxylic acid ethyl ester, N-bromosuccinimide (NBS), 0.05g benzoyl peroxide (BPO) to a three-necked flask, and add dry 1,2-dichloroethane thereto, and heat under reflux for 8h; after the reaction is completed, the insoluble white solid succinimide is removed by filtration, and the resulting yellow solution is evaporated under reduced pressure to obtain a pale yellow crude product, which is recrystallized from an ethyl acetate / ethanol mixed solution to obtain a white solid 3,4-dibromomethylthiophene dicarboxylic acid ethyl ester; the molar ratio of 3,4-dimethylthiophene dicarboxylic acid ethyl ester, N-bromosuccinimide (NBS), and benzoyl peroxide (BPO) is 1:3:0.08, and the amount of 1,2-dichloroethane used is 60mL;

[0010] c. Place 3,4-dibromomethylthiophene dicarboxylic acid ethyl ester, potassium carbonate, imidazole and acetonitrile in a three-necked flask and react in a water bath at 80°C for 3 hours. After reaction, cool to room temperature, filter to remove potassium carbonate, evaporate to remove solvent under reduced pressure, dissolve the resulting solid in dichloromethane, transfer to a separatory funnel, wash three times with saturated sodium carbonate solution, and finally dry over anhydrous magnesium sulfate. Remove the solvent under reduced pressure to obtain 3,4-di(imidazolyl)thiophene dicarboxylic acid ethyl ester crystals; the molar ratio of 3,4-dibromomethylthiophene dicarboxylic acid ethyl ester, potassium carbonate, imidazole and is 1:5:16, and the amount of acetonitrile is 100 mL;

[0011] d. The 3,4-bis(imidazolylmethyl)thiophene dicarboxylic acid ethyl ester was placed in an ethanol / water mixed solution containing potassium hydroxide and hydrolyzed, the pH was adjusted to 2, the precipitate was filtered and dried to obtain 3,4-diimidazolylmethylthiophene dicarboxylic acid; the mass ratio of the 3,4-bis(imidazolylmethyl)thiophene dicarboxylic acid ethyl ester and potassium hydroxide was 1:1.5, and the volume ratio of ethanol and water was 1:1;

[0012] e. The 3,4-dimethylthiophene dicarboxylic acid ethyl ester was placed in an ethanol / water mixed solution containing potassium hydroxide and hydrolyzed, the pH was adjusted to 2, the precipitate was filtered and dried to obtain 3,4-dimethylthiophene dicarboxylic acid; the mass ratio of the 3,4-dimethylthiophene dicarboxylic acid ethyl ester and potassium hydroxide was 1:1.5, and the volume ratio of ethanol and water was 1:1;

[0013] f. Dissolve 3,4-bis(imidazolylmethyl)thiophene dicarboxylic acid, 3,4-dimethylthiophene dicarboxylic acid, benzoic acid, and a zirconium salt in N,N-dimethylformamide, place in a reactor, heat at 150°C for 36 hours, filter, and soak the resulting precipitate in dichloromethane and heat-activate to obtain a solid, named Imidazolyl-MOF-1. The zirconium salt is one of zirconium chloride, zirconyl chloride, or zirconyl nitrate; the molar ratio of 3,4-bis(imidazolylmethyl)thiophene dicarboxylic acid, 3,4-dimethylthiophene dicarboxylic acid, benzoic acid, and zirconium salt is 1:1:60:2, and the amount of N,N-dimethylformamide used is 10 mL;

[0014] g. Imidazolyl-MOF-1, alkylating agent and acetonitrile were added to the reaction vessel and placed in an oven at 100°C for 48 hours. After the reaction was completed, the mixture was cooled and filtered, washed with DMF, refluxed in dichloromethane for 4 hours, and then vacuum dried to obtain an ionic metal-organic framework catalyst (Br - )R-Imidazolium-MOF-1(R=C n H 2n+1 , n≥2); the alkylating agent is one of ethyl bromide, propyl bromide, butyl bromide, and hexyl bromide. The molar ratio of the imidazolyl-MOF-1 to the alkylating agent is 1:125, and the amount of acetonitrile used is 15 mL.

[0015] The present invention also claims protection for the ionic metal-organic framework catalyst (Br - )Application of C3H7-Imidazolium-MOF-1 in the catalytic reaction of CO2 and epoxides to synthesize cyclic carbonates.

[0016] The beneficial effects of the present invention compared with the prior art are:

[0017] The ionic metal-organic framework catalyst (Br - C3H7-Imidazolium-MOF-1 organically integrates Lewis acidic sites with nucleophilic bromide ions, which serve as counteranions dispersed within a positively charged metal-organic framework containing zirconium oxo clusters. Its high surface area and pronounced mesoporous nature allow it to effectively catalyze the synthesis of cyclic carbonates from CO2 and epoxides under mild, catalyst-free, solvent-free conditions. The product is recyclable and easily separated and purified. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the nuclear magnetic spectrum of the ligand 3,4-bis(imidazolylmethyl)thiophenedicarboxylic acid in Example 1 of the present invention.

[0019] Figure 2 Imidazolyl-MOF-1 and (Br in Example 1 of the present invention - )Powder diffraction pattern of C3H7-Imidazolium-MOF-1.

[0020] Figure 3 (Br - )Photoelectron spectrum of C3H7-Imidazolium-MOF-1.

[0021] Figure 4 The (Br prepared in Example 1 of the present invention - )N2 adsorption and pore size distribution of C3H7-Imidazolium-MOF-1.

[0022] Figure 5 Prepared by the embodiment of the present invention (Br - ) Schematic diagram of the cyclic test results of the reaction of epichlorohydrin with CO2 catalyzed by C3H7-Imidazolium-MOF-1 and the powder diffraction pattern after the catalytic reaction. DETAILED DESCRIPTION

[0023] The present invention is described in detail below by specific examples, but the scope of protection of the present invention is not limited. Unless otherwise specified, the experimental methods adopted in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0024] Example 1:

[0025] The preparation method of the ionic metal-organic framework catalyst containing imidazolium of the present invention is carried out in the following steps:

[0026] a. To a 250mL three-necked flask were added 10g of acetylacetone (0.1mol), 69.1g of anhydrous potassium carbonate (0.5mol) and 100mL of DMF, and 6mL of CS2 (0.1mol) was slowly added dropwise under ice bath conditions. After the addition was complete, the mixture was stirred at room temperature for 20min, and then ice bathed again. A mixed solution of 22mL of ethyl bromoacetate (0.2mol) and 20mL of DMF was slowly added dropwise. After the addition was complete, the mixture was stirred at room temperature for 12h, heated to 50°C and stirred for 2h. After the reaction was completed, the mixture was cooled to room temperature and poured directly into deionized water to produce a large amount of precipitate, which was collected by filtration and dried to give ethyl 3,4-dimethylthiophenedicarboxylate in a yield of 92%.

[0027] b. A 250 mL three-necked flask was charged with 1.56 g of ethyl 3,4-dimethylthiophenedicarboxylate (5 mmol), 2.67 g of N-bromosuccinimide (NBS) (15 mmol), and 0.05 g of benzoyl peroxide (BPO) (0.4 mmol). 60 mL of dry 1,2-dichloroethane was added and the mixture was heated under reflux for 8 h. After the reaction, the insoluble white solid succinimide was removed by filtration. The resulting yellow solution was evaporated under reduced pressure to obtain a pale yellow solid crude product. This was recrystallized from a 1 / 3 ethyl acetate / ethanol mixture to obtain ethyl 3,4-dibromomethylthiophenedicarboxylate as a white solid in a 70% yield.

[0028] c. To a 250 mL three-necked flask, 4.7 g (10 mmol) of ethyl 3,4-dibromomethylthiophene dicarboxylate, 10.9 g of imidazole (160 mmol), 6.9 g of anhydrous potassium carbonate (50 mmol) and 100 mL of acetonitrile were added. The mixture was reacted in a water bath at 80°C for 3 h. After the reaction was completed, the mixture was cooled to room temperature, the potassium carbonate was removed by filtration, and the solvent was removed by evaporation under reduced pressure. The resulting solid was dissolved in 60 mL of dichloromethane, transferred to a separatory funnel, washed three times with 50 mL of saturated sodium carbonate solution, and finally dried over anhydrous magnesium sulfate, filtered, and naturally crystallized to obtain pink crystals of ethyl 3,4-di(imidazole methylene)thiophene dicarboxylate with a yield of 72%.

[0029] d. A mixed solution of 1 g of ethyl 3,4-bis(imidazolylmethylidene)thiophenedicarboxylate, 1.5 g of potassium hydroxide, 10 mL of deionized water, and 10 mL of ethanol was added to a 100 mL flask. The mixture was heated under reflux for 4 h, then cooled to room temperature and the pH was adjusted to 2 with 1 M HCl. A large amount of white precipitate was precipitated, which was filtered and washed with water until neutral to obtain 3,4-bis(imidazolylmethylidene)thiophenedicarboxylic acid as a white solid with a yield of 95%.

[0030] e. A mixed solution of 1 g of ethyl 3,4-dimethylthiophenedicarboxylate, 1.5 g of potassium hydroxide, 10 mL of deionized water, and 10 mL of ethanol was added to a 100 mL flask. The mixture was heated under reflux for 4 h, then cooled to room temperature and the pH was adjusted to 2 with 1 M HCl. A large amount of white precipitate was precipitated, which was filtered and washed with water until neutral to obtain 3,4-dimethylthiophenedicarboxylic acid as a white solid with a yield of 95%.

[0031] f. To a 20mL polytetrafluoroethylene reactor, 0.058g of 3,4-di(imidazolyl)thiophene dicarboxylic acid (0.15mmol), 0.038g of 3,4-dimethylthiophene dicarboxylic acid (0.15mmol), and 0.07g of zirconium chloride (0.3mmol) were added, followed by 1g of benzoic acid (9mmol) and 5mL of DMF. Ultrasonication was performed for 20min to uniformly disperse the product. The product was placed in an oven at 150°C and reacted for 36h. The solid was collected by filtration and washed with DMF. The product was soaked in dichloromethane, activated by heating, and dried to obtain a white solid named Imidazolyl-MOF-1 with a yield of 56%.

[0032] g. Imidazolyl-MOF-1 was placed in DMF and heated with stirring for 3 h, refluxed in acetone for 3 h, and then dried in vacuum; 1 g of Imidazolyl-MOF-1, 5 mL of bromopropane, and 15 mL of acetonitrile were added to a 20 mL polytetrafluoroethylene reactor and placed in a 100 ° C oven for 48 h. After the reaction was completed, it was cooled and filtered, washed with DMF, refluxed in dichloromethane for 4 h, and dried in vacuum to obtain an ionic metal-organic framework catalyst containing imidazolium (Br - )C3H7-Imidazolium-MOF-1.

[0033] Experimental research:

[0034] Experimental Example 1:

[0035] The NMR results of the ligand 3,4-di(imidazolylmethyl)thiophenedicarboxylic acid prepared in Example 1 are shown in the attached figure. Figure 1 δ8.57 (s, 1H) corresponds to the hydrogen on the carbon between the two nitrogen atoms of imidazole, 7.36-7.37 (d, J = 9.1 Hz, 2H) corresponds to the other two hydrogen atoms of imidazole, and 5.81 (s, 2H) corresponds to the hydrogen atom of the methylene group attached to imidazole. These data demonstrate that the H NMR spectrum of the experimentally prepared ligand 3,4-bis(imidazolylmethylidene)thiophenedicarboxylic acid corresponds to its structural information, confirming the successful synthesis of the pre-designed ligand.

[0036] Experimental Example 2:

[0037] The structure and purity of the sample were confirmed by X-ray powder diffraction. Zr-DMTDC was prepared from dimethylthiophenedicarboxylic acid and zirconium chloride according to the method in the literature (CrystEngComm, 2015, 17, 3586-3590), which was used as a comparative sample to assist in determining the structure of the target product. Figure 2 As shown, it can be seen that the characteristic diffraction peaks of Imidazolyl-MOF-1 at 2θ=6.48°, 7.78°, 13.26°, 15.36° and 23.01° correspond well to the diffraction peaks of Zr-DMTDC, proving that Imidazolyl-MOF-1 and Zr-DMTDC are isostructural and both have a UiO-66 network structure. The diffraction data also show that Imidazolyl-MOF-1 has good crystallinity and purity. Similarly, (Br - )The diffraction patterns of C3H7-Imidazolium-MOF-1 and Imidazolyl-MOF-1 are basically consistent, indicating that the main framework of the material remains intact during the post-synthesis modification process.

[0038] Experimental Example 3:

[0039] In order to further characterize the composition of the samples, X-ray photoelectron spectroscopy was used to characterize the - )C3H7-Imidazolium-MOF-1 was qualitatively analyzed. Figure 3 , (Br - ) The XPS spectrum of C3H7-Imidazolium-MOF-1 shows that (Br - )C3H7-Imidazolium-MOF-1 contains C, N, O, S, Zr, and Br elements. The binding energies of C 1s are 284.6eV, 286.5eV, and 288.8eV, corresponding to the three binding states of C–C, C–N, and C=O, respectively; the binding energies of N 1s are 399.5eV and 401.7eV, corresponding to the unalkylated imidazole N atom and the alkylated imidazolium salt N atom, respectively. At the same time, Figure 3 d shows a broad Br 3d band, which is attributed to the free bromide ions. XPS results further demonstrate that after post-synthesis modification, bromide ions are free and dispersed in the MOFs structure as counter anions.

[0040] Experimental Example 4:

[0041] The porosity of the catalyst prepared in Example 1 was characterized by N2 physical adsorption. Before the adsorption test, the catalyst was refluxed in dichloromethane for 3 h and then dried in vacuum. Figure 4 As shown, (Br -)C3H7-Imidazolium-MOF-1 exhibits type IV adsorption behavior, representing a mesoporous structure. (Br - ) The Brunauer-Emmett-Teller surface areas of C3H7-Imidazolium-MOF-1 are 516 m 2 ·g -1 , the pore diameters are concentrated in the range of 5 to 7 nm. (Br - )The larger pore size of C3H7-Imidazolium-MOF-1 facilitates the catalytic reaction of CO2 and epoxides.

[0042] Experimental Example 5:

[0043] The catalyst prepared in Example 1 of the present invention (Br - )C3H7-Imidazolium-MOF-1 performance. Different temperatures for (Br - The effect of C3H7-Imidazolium-MOF-1 on the synthesis of cyclic carbonates by CO2 and epichlorohydrin was investigated. The reaction conditions were 20 mmol of substrate, (Br - )C3H7-Imidazolium-MOF-1 catalyst 150mg, CO2 pressure 0.1MPa, reaction time 12h, reaction temperature were room temperature, 50℃, 70℃, 90℃ and 110℃ respectively. The experimental results are shown in Table 1. The conversion rate of epichlorohydrin at room temperature was 15.5%. The lower conversion rate was due to the difficulty of the reaction at low temperature. As the temperature increased, the conversion rate of epichlorohydrin gradually increased. When the reaction temperature was raised to 90℃, it was observed that (Br - The conversion rate of C3H7-Imidazolium-MOF-1 in the reaction increased to 82.3%. Further increasing the temperature to 110°C did not improve the conversion rate. Considering cost factors, the reasonable operating temperature of the catalyst is 90°C.

[0044] Table 1 Synthesis of cyclic carbonates by catalytic reaction of CO2 and epichlorohydrin at different temperatures a

[0045]

[0046] a Reaction conditions: 20 mmol of epichlorohydrin, 0.1 MPa of CO2, 150 mg of catalyst, and 12 h. b The conversion and yield were determined by GC-7890II.

[0047] Experimental Example 6:

[0048] Because (Br - )C3H7-Imidazolium-MOF-1 showed good catalytic effect on the cycloaddition reaction of CO2 and epichlorohydrin. We also investigated (Br - )C3H7-Imidazolium-MOF-1 has a catalytic activity for other epoxy compounds, and the results are shown in Table 2. The reaction conditions are all 20 mmol of substrate, 150 mg of catalyst, a reaction pressure of 0.1 MPa, and a reaction time of 24 h. Due to the low boiling point of butylene oxide, the catalytic reaction was carried out at 50 °C, and the other reactions were carried out at 90 °C. The experimental results show that the yield of cyclic carbonates with butylene oxide decreased to 73.5% compared with epichlorohydrin. This is because the low reaction temperature is not conducive to the activation of epoxy compounds. It has a high catalytic activity for allyl glycidyl ether, with a yield of 83.6%, which is close to the yield of epichlorohydrin. The catalyst shows moderate catalytic activity for styrene oxide and phenyl glycidyl ether, which is mainly attributed to the larger size of epoxy compounds having greater steric hindrance, which hinders the contact between the substrate and the active center. In addition, the low reaction activity of the β-C atom of styrene oxide is also one of the important reasons for its low conversion rate. The above results show that (Br - )C3H7-Imidazolium-MOF-1 exhibits relatively good catalytic activity for this type of cycloaddition reaction, especially effectively promoting the addition reaction of CO2 with small molecule epoxy compounds.

[0049] Table 2 Catalytic reaction of CO2 with different epoxides to synthesize cyclic carbonates

[0050]

[0051]

[0052] a Reaction conditions: 20 mmol of epoxy compound, 0.1 MPa of CO2, and 150 mg of catalyst; b Conversion and yield were determined by GC-7890II; c The calculation of the transformation number is based on the metal element.

[0053] Experimental Example 7:

[0054] (Br - The recyclable performance of C3H7-Imidazolium-MOF-1 in the cycloaddition reaction of CO2 with epichlorohydrin was investigated. After each catalytic reaction, the catalyst was separated, washed with methanol and acetone, refluxed in dichloromethane for 4 hours, and dried under vacuum. The regenerated catalyst was then directly used in the next reaction. The results of the recyclable test are shown in the attached figure. Figure 5 As shown in Figure 2, after five cycles, the activity of the catalyst did not decrease significantly. The PXRD pattern after the catalytic reaction showed that (Br - )The structure of C3H7-Imidazolium-MOF-1 remains intact and the main framework is not destroyed. The above results show that (Br - )C3H7-Imidazolium-MOF-1 is recyclable.

[0055] The above-described embodiments are only preferred embodiments of the present invention, and are not intended to be all feasible embodiments of the present invention. Any obvious modifications made by a person skilled in the art without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an ionic metal-organic framework catalyst for CO2 cycloaddition reaction, characterized in that: The details are as follows: a. Acetylacetone, anhydrous potassium carbonate, and N,N-dimethylformamide were added to a three-necked flask. Carbon disulfide was added dropwise under ice bath conditions and stirred at room temperature for 20 min. Ethyl bromoacetate was then added dropwise under ice bath conditions. After the addition was complete, the mixture was stirred at room temperature for 12 h, heated to 50 °C, and stirred for 2 h. After the reaction was completed, the mixture was cooled to room temperature and poured directly into deionized water. The precipitate was filtered and dried to obtain ethyl 3,4-dimethylthiophenedicarboxylate. The molar ratio of acetylacetone, anhydrous potassium carbonate, carbon disulfide, and ethyl bromoacetate was 1:5:1:

2. The amount of N,N-dimethylformamide used was 100 mL. b. Add 3,4-dimethylthiophene dicarboxylic acid ethyl ester, N-bromosuccinimide, and 0.05 g of benzoyl peroxide to a three-necked flask, and add dry 1,2-dichloroethane. Heat and reflux for 8 h. After the reaction, remove the insoluble white solid succinimide by filtration, and evaporate the resulting yellow solution under reduced pressure to obtain a pale yellow crude product. Recrystallize from an ethyl acetate / ethanol mixture to obtain 3,4-dibromomethylthiophene dicarboxylic acid ethyl ester as a white solid. The molar ratio of 3,4-dimethylthiophene dicarboxylic acid ethyl ester, N-bromosuccinimide, and benzoyl peroxide is 1:3:0.08, and the amount of 1,2-dichloroethane used is 60 mL. c. Place ethyl 3,4-dibromomethylthiophene dicarboxylate, potassium carbonate, imidazole, and acetonitrile in a three-necked flask and react in an 80°C water bath for 3 h. After reaction, cool to room temperature, filter out the potassium carbonate, and evaporate the solvent under reduced pressure. The resulting solid is dissolved in dichloromethane, transferred to a separatory funnel, and washed three times with a saturated sodium carbonate solution. Finally, dry over anhydrous magnesium sulfate and remove the solvent under reduced pressure to obtain ethyl 3,4-di(imidazolyl)thiophene dicarboxylate crystals. The molar ratio of ethyl 3,4-dibromomethylthiophene dicarboxylate, potassium carbonate, and imidazole is 1:5:16, and the amount of acetonitrile used is 100 mL. d. hydrolyzing ethyl 3,4-bis(imidazolylmethylidene)thiophene dicarboxylate in an ethanol / water mixture containing potassium hydroxide, adjusting the pH to 2, and precipitating the precipitate. The precipitate was filtered and dried to obtain 3,4-bis(imidazolylmethylidene)thiophene dicarboxylic acid; the mass ratio of ethyl 3,4-bis(imidazolylmethylidene)thiophene dicarboxylate to potassium hydroxide was 1:1.5, and the volume ratio of ethanol to water was 1:1; e. The 3,4-dimethylthiophene dicarboxylic acid ethyl ester was placed in an ethanol / water mixed solution containing potassium hydroxide and hydrolyzed, the pH value was adjusted to 2, the precipitate was filtered and dried to obtain 3,4-dimethylthiophene dicarboxylic acid; the mass ratio of the 3,4-dimethylthiophene dicarboxylic acid ethyl ester and potassium hydroxide was 1:1.5, and the volume ratio of ethanol and water was 1:1; f. Dissolve 3,4-bis(imidazolylmethyl)thiophene dicarboxylic acid, 3,4-dimethylthiophene dicarboxylic acid, benzoic acid, and a zirconium salt in N,N-dimethylformamide, place in a reactor, heat at 150°C for 36 h, filter, and soak the resulting precipitate in dichloromethane and heat-activate to obtain a solid, named Imidazolyl-MOF-1. The zirconium salt is any one of zirconium chloride, zirconyl chloride, or zirconyl nitrate. The molar ratio of 3,4-bis(imidazolylmethyl)thiophene dicarboxylic acid, 3,4-dimethylthiophene dicarboxylic acid, benzoic acid, and zirconium salt is 1:1:60:2, and the amount of N,N-dimethylformamide used is 10 mL. g. Imidazolyl-MOF-1, alkylating agent and acetonitrile were added to the reaction vessel and placed in an oven at 100 °C for 48 h. After the reaction, the mixture was cooled and filtered, washed with N,N-dimethylformamide, refluxed in dichloromethane for 4 h, and then vacuum dried to obtain an ionic metal-organic framework catalyst (Br - )R-Imidazolium-MOF-1, where R = C n H 2n+1 , n≥2; the alkylating agent is any one of ethyl bromide, propyl bromide, butyl bromide and hexyl bromide; the molar ratio of the imidazolyl-MOF-1 and the alkylating agent is 1:125, and the amount of acetonitrile used is 15 mL.

2. The method for preparing an ionic metal-organic framework catalyst for CO2 cycloaddition reaction according to claim 1, wherein the catalyst It is constructed by a linear dicarboxylic acid ligand containing an imidazolium substituent and a metal oxygen cluster Zr6O4(OH)4 and is named (Br - )R-Imidazolium-MOF-1; it has a classic UiO-66 topological structure.

3. The ionic metal-organic framework catalyst (Br) obtained by the preparation method of an ionic metal-organic framework catalyst for CO2 cycloaddition reaction according to claim 1 - )C n H 2n+1 Application of -Imidazolium-MOF-1 in the catalytic reaction of CO2 and epoxides to synthesize cyclic carbonates.

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