A Zn-Salen-based ionic polymer catalyst, its preparation method and application

Abstract

The present invention discloses a Zn-Salen-based ionic polymer catalyst, its preparation method and application. Using 3,4-diamino-1-benzylpyridine bromide, 4-hydroxyisophthalaldehyde and zinc acetate as raw materials, and methanol as a solvent, reflux for 16 h to synthesize a pyridine ionic liquid-functionalized Zn-Salen complex with dialdehyde groups. Then, further carry out a polymerization reaction with benzamidine hydrochloride under the condition of cesium carbonate as a catalyst and a programmed temperature rise of 60-120 °C. After washing with an organic solvent and vacuum drying, the Zn-Salen-based ionic polymer catalyst is obtained. The preparation method of the present invention is simple, the raw materials are easily available, the purification process is simple, the catalyst has high purity. The obtained Zn-Salen-based ionic polymer catalyst can exhibit high activity and selectivity in the reaction of synthesizing cyclic carbonates from CO<subgt;2< / subgt; and epoxides under solvent-free and co-catalyst-free conditions, and can be simply separated and reused; it belongs to the technical field of heterogeneous catalysts.

Description

Technical Field

[0001] The present invention belongs to the technical field of heterogeneous catalysts, and particularly relates to a multi-Zn-Salen-based ionic polymer catalyst, a preparation method thereof, and an application thereof in catalyzing the synthesis of cyclic carbonates from carbon dioxide and epoxides. Background Art

[0002] At present, the strategy of capturing CO2 and using and storing it as a C1 synthon to synthesize useful chemicals, namely CO2 capture, utilization, and storage (CCUS), has become the most promising technology. Among the numerous reactions involving CO2, the reaction of synthesizing cyclic carbonates from CO2 and epoxides has 100% atom economy, and the driving force of the reaction comes from the release of ring strain, avoiding a large amount of additional energy consumption. In addition, cyclic carbonates have great application prospects and can be used as lithium battery electrolytes, raw materials for polymer synthesis, reaction intermediates, etc.

[0003] For the cycloaddition reaction of CO2 and epoxides, a variety of homogeneous and heterogeneous catalytic systems have been developed. Among them, the acid-base synergistic catalysis mechanism is widely accepted in the CO2 cycloaddition reaction, and the catalytic systems designed based on this mechanism have the characteristics of mild reaction conditions and high efficiency (Journal of Chemical Industry and Engineering, 2016, 67, 258). In particular, the development of bifunctional catalysts based on Lewis acidic metal complexes and ionic liquids that can provide nucleophilic halogen ions has been rapid. However, most of the above catalytic systems are homogeneous, and heterogeneous catalysts have the characteristics of easy separation and recovery compared with them. Furthermore, the heterogenization strategy of ionic liquid-functionalized metal complex catalysts has attracted extensive attention. Among them, porous organic polymers stand out with their excellent physical and chemical properties (Green Chem. Eng., 2022, 3, 96; ACS Catal., 2018, 8, 9079). As early as 2017, Ji et al. successfully prepared metal porphyrin-based porous ionic polymers by Yamamoto-Ullmann coupling reaction using metal porphyrins and ionic liquids as monomers (ChemSusChem, 2017, 10, 2534). Metal Salen-based porous ionic polymers were successfully prepared by free radical polymerization using metal Salen complexes and ionic liquids as monomers (ChemSusChem, 2017, 10, 1526). The above bifunctional polymers exhibited excellent catalytic performance in the reaction of catalyzing the synthesis of cyclic carbonates from CO2 and epoxides.

[0004] From the perspective of the basic principles of heterogeneous catalysis, the adsorption of reactants at catalytic active sites is one of the key steps to complete the catalytic reaction. The micropores in porous organic polymers are conducive to CO2 enrichment, and the CO2-philic groups or atoms enhance this enrichment effect and even enable selective CO2 adsorption (J. Mater. Chem. A, 2017, 5, 1334; Chemical Industry and Engineering Progress, 2021, 40, 3564). For example, due to the larger quadrupole moment of CO2 molecules, there is a certain dipole-dipole interaction between nitrogen atoms and CO2 molecules, endowing the polymer with the characteristic of preferential CO2 adsorption. This characteristic is particularly important in the catalytic conversion reaction of impure CO2. However, when designing porous organic polymerization catalysts based on metal complexes and ionic liquids, the introduction of CO2-philic groups or atoms is mostly ignored, resulting in the rarity of currently developed multifunctional porous organic polymer catalytic materials. In the process of designing multifunctional porous organic polymer catalytic materials, it is found that a class of porous organic polymers, covalent triazine frameworks, have characteristics such as high specific surface area, high porosity, and stable physical and chemical structures (J. Mater. Chem. A, 2019, 7(10): 5153-5172). In particular, a large number of triazine structures in the framework contain abundant nitrogen atoms, and such polymers exhibit excellent performance in CO2 adsorption tests. At the same time, they show high activity and high selectivity in the CO2 cycloaddition reaction (ACS Appl. Mater. Interfaces, 2017, 9, 7209). Therefore, a multifunctional porous organic polymer catalytic material can be obtained by constructing metal complexes and ionic liquids in covalent triazine frameworks. In 2020, Cao et al. successfully obtained a cobalt porphyrin-based ionic covalent triazine framework through a solvent-free thermal synthesis method and applied it to the cycloaddition reaction of CO2 and epoxides. The results showed that when epichlorohydrin was used as the raw material, at 0.1 MPa and 120 °C, the reaction time of 24 h could achieve a product yield of 94% (Catal. Sci. Technol., 2020, 10, 8026). This research achievement provides a reference for the subsequent development of catalytic materials with similar structural and functional characteristics. In addition, there is no report on multifunctional triazine framework catalysts designed based on other metal complexes such as metal Salen complexes.

[0005] Therefore, based on the above situation, further developing multifunctional triazine framework catalytic materials with high activity, high selectivity, and high stability based on metal Salen complexes and other complexes and applying them to CO2 selective capture and catalytic conversion reactions have great fundamental research significance and application value. Summary of the Invention

[0006] The first object of the present invention is to provide a Zn-Salen-based ionic polymer catalyst, which has abundant nitrogen atoms and can play a good role in selectively adsorbing and enriching CO2 during the catalytic process, making the catalytic efficiency higher.

[0007] The second object of the present invention is to provide a preparation method of the above catalyst. The preparation method is simple, the raw materials are easy to obtain, the yield is high, and all solvents in the reaction can be recovered.

[0008] The third object of the present invention is to provide the synthesis of cyclic carbonate from CO2 and epoxide catalyzed by the above catalyst. This reaction does not require the addition of any solvent and cocatalyst, and the reaction conditions are relatively mild.

[0009] For this reason, the first technical solution provided by the present invention is as follows:

[0010] A Zn-Salen-based ionic polymer catalyst, whose structural formula is shown in formula (I):

[0011]

[0012] The second technical solution provided by the present invention is a preparation method of a Zn-Salen-based ionic polymer heterogeneous catalyst. This method uses 3,4-diaminopyridine, 4-hydroxyisophthalaldehyde and zinc acetate as raw materials, and generates a Zn-Salen complex with bis-aldehyde groups through a Schiff-base reaction. Then, the above complex reacts with benzamidine hydrochloride to prepare a Zn-Salen-based ionic polymer heterogeneous catalyst.

[0013] Specifically, it includes the following steps:

[0014] 1) Take 3,4-diamino-1-benzylpyridinium bromide and 4-hydroxyisophthalaldehyde with a molar ratio of 1:1-2 and add them to a round-bottom flask containing methanol. After stirring and mixing at room temperature for 1 h, zinc acetate dihydrate is added. Then it is placed in a 60 °C reaction bath and stirred for 16 h. The obtained precipitate is washed several times with methanol, ethyl acetate, acetone and petroleum ether, and then vacuum dried at 80 °C for 24 h to obtain a pyridine ionic liquid-functionalized Zn-Salen complex containing bis-aldehyde groups;

[0015] 2) Add the pyridine ionic liquid-functionalized Zn-Salen complex containing bis-aldehyde groups prepared in step 1) and benzamidine hydrochloride with a molar ratio of 1:1-3 to a thick-walled pressure-resistant bottle containing dimethyl sulfoxide and deionized water. Then cesium carbonate is added, and it is placed in a constant-temperature magnetic stirrer and reacted for 4.5 days by a programmed temperature rise method. After cooling to room temperature, the obtained solid is washed with acid and solvents, and finally vacuum dried at 120 °C for 12 h to obtain a Zn-Salen-based ionic polymer catalyst.

[0016] Further, the molar ratio of the 3,4-diamino-1-benzylpyridinium bromide to zinc acetate dihydrate in step 1) is: 1∶1 - 2.5.

[0017] Further, the molar ratio of the phthalimid hydrochloride to cesium carbonate in step 2) is: 1∶1 - 3;

[0018] Further, the programmed temperature rising method in step 2) is: the heating rate is 10°C / min, hold for 12 h when reaching 60°C, then hold for 12 h when reaching 80°C, then hold for 12 h when reaching 100°C, and finally heat up to 120°C and continue the reaction for 3 days;

[0019] Further, the solvent used for pickling in step 2) is an HCl aqueous solution or an HBr aqueous solution;

[0020] Further, the dosage and concentration of the acid solution used for pickling in step 2) are 100 - 300 mL and 1 - 2 mmol / L;

[0021] Further, the washing in step 2) adopts a method combining suction filtration washing and Soxhlet extraction. The solvent for suction filtration washing is 60 - 100 mL of deionized water, tetrahydrofuran and acetone, and the Soxhlet extraction uses 250 mL of tetrahydrofuran as the solvent.

[0022] The third technical solution of the present invention is the application of a Zn-Salen-based ionic polymer catalyst in the reaction of catalytically synthesizing cyclic carbonates from CO2 and epoxides, which successively includes the following steps: Without adding any solvent and cocatalyst, a certain volume concentration of CO2 and an epoxide are subjected to a cycloaddition reaction under constant stirring at a certain pressure and reaction temperature in the presence of 20 mg of the catalyst, and a cyclic carbonate is obtained after reacting for 8 - 72 h;

[0023] The certain volume concentration of CO2 in the above steps is 15 - 100% of CO2, and the CO2 with a concentration lower than 100% is obtained by mixing any one of the inert gases such as nitrogen, helium, neon or argon into the CO2 gas;

[0024] The epoxide in the above steps has the structural formula as described in formula (II):

[0025]

[0026] The cyclic carbonate in the above steps has the structural formula as described in formula (III):

[0027]

[0028] The pressure in the above steps is 0.5 - 6.0 MPa. Preferably, the reaction pressure is 1.0 MPa;

[0029] The reaction temperature in the above steps is 80 - 150 °C. Preferably, the reaction temperature is 120 °C;

[0030] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0031] 1. The preparation method of the Zn-Salen-based ionic polymer catalyst provided by the present invention is simple, the raw materials are easy to obtain, the yield is high, all solvents in the reaction can be recycled, and the obtained catalyst is stable to air and water.

[0032] 2. The Zn-Salen-based ionic polymer catalyst prepared by the present invention has abundant nitrogen atoms, which can play a good role in selectively adsorbing and enriching CO2 during the catalytic process, making the catalytic efficiency higher; especially, it can smoothly convert low-concentration CO2 into cyclic carbonate when used as a raw material, effectively reducing the energy consumption generated in the process of obtaining pure CO2, and realizing the coupling of CO2 selective capture and catalytic conversion.

[0033] 3. Using the Zn-Salen-based ionic polymer catalyst provided by the present invention to catalyze the synthesis of cyclic carbonate from CO2 and epoxide, no solvent and co-catalyst need to be added, the reaction conditions are mild, the catalytic activity is high, the product selectivity is high, and the recycling and regeneration process is simple and can be reused multiple times. Description of the Drawings

[0034] Figure 1 It is the infrared spectrum of the Zn-Salen-based ionic polymer catalyst provided for Example 2;

[0035] Figure 2 It is the EDS energy spectrum of the Zn-Salen-based ionic polymer catalyst provided for Example 2;

[0036] Figure 3 It is the gas chromatogram of the cyclic carbonate synthesized in Example 3;

[0037] Figure 4 It is the gas chromatogram of the cyclic carbonate synthesized in Example 4;

[0038] Figure 5 It is the gas chromatogram of the cyclic carbonate synthesized in Example 5;

[0039] Figure 6 It is the gas chromatogram of the cyclic carbonate synthesized in Example 6;

[0040] Figure 7 It is the gas chromatogram of the cyclic carbonate synthesized in Example 7;

[0041] Figure 8 Gas chromatogram of the cyclic carbonate synthesized in Example 8;

[0042] Figure 9 Gas chromatogram of the cyclic carbonate synthesized in Example 9;

[0043] Figure 10 Gas chromatogram of the cyclic carbonate synthesized in Example 10. Detailed implementation manners

[0044] The present invention will be further described in detail below through examples. However, these examples are only for illustrative purposes and should not be construed as any limitation to the present invention.

[0045] Synthesis of pyridine ionic liquid-functionalized Zn-Salen complex containing dialdehyde groups

[0046] Add 3,4-diamino-1-benzylpyridinium bromide (4 mmol, 1.12 g), 4-hydroxyisophthalaldehyde (8 mmol, 1.20 g) and 60 mL of methanol into a 150 mL round-bottom flask. After stirring and mixing at room temperature for 1 h, add zinc acetate dihydrate (4.05 mmol, 0.889 g). Then place it in a 60 °C reaction bath and stir for 16 h. The obtained precipitate is washed successively 3 times with methanol (30 mL), ethyl acetate (30 mL), acetone (30 mL) and petroleum ether (30 mL), and then dried under vacuum at 80 °C for 24 h to obtain 1.64 g of pyridine ionic liquid-functionalized Zn-Salen complex containing dialdehyde groups.

[0047] Preparation of Zn-Salen-based ionic polymer catalyst

[0048] Add the pyridine ionic liquid-functionalized Zn-Salen complex containing dialdehyde groups prepared in Example 1 (1.0 mmol, 0.608 g), phthalimid hydrochloride (2.0 mmol, 0.470 g), 5 mL of dimethyl sulfoxide, and 0.2 mL of deionized water to a 100 mL thick-walled pressure-resistant bottle. Subsequently, add cesium carbonate (4.5 mmol, 1.466 g). After stirring evenly at room temperature, place it in a thermostatic magnetic stirrer and heat the reaction using a programmed temperature increase method: the heating rate is 10 °C / min. When it reaches 60 °C, maintain for 12 h, then reach 80 °C and maintain for 12 h, then reach 100 °C and maintain for 12 h, and finally heat up to 120 °C and continue the reaction for 3 days. After the reaction is completed and cooled to room temperature, the obtained solid is washed with 250 mL of 2 mmol / L hydrochloric acid solution, and then successively washed 3 - 5 times with deionized water (60 mL), tetrahydrofuran (60 mL), and acetone (60 mL) using a Buchner funnel. Further purify the obtained solid by Soxhlet extraction using 250 mL of tetrahydrofuran as the solvent. Finally, dry it under vacuum at 120 °C for 12 h to obtain 0.805 g of the Zn-Salen-based ionic polymer catalyst. Refer to the infrared spectrogram Figure 1 ; Refer to the EDS energy spectrum Figure 2 .

[0049] The catalyst in Example 3 catalyzes the cycloaddition reaction of CO2 and epichlorohydrin

[0050] Under room temperature conditions, add 20 mg of the Zn-Salen-based ionic polymer catalyst and 3 mmol of epichlorohydrin to a 10 mL stainless steel autoclave. After sealing the autoclave, repeatedly and slowly charge and discharge CO2 gas 3 times. Then charge CO2 to make the pressure stable at 1.0 MPa. Place the autoclave in a 100 °C thermostatic stirrer and stir for 12 h. After the reaction is completed, slowly release the unreacted CO2 after cooling in an ice-water bath. Subsequently, add 5 mL of ethyl acetate to the autoclave and separate the solid catalyst by centrifugation. Take an appropriate amount of the supernatant for gas chromatography analysis, refer to Figure 3 ; The calculated conversion rate is 99.9%, and the selectivity is 97.9%.

[0051] Example 4 Catalyze the reaction of carbon dioxide and epibromohydrin to synthesize cyclic carbonate

[0052] Under room temperature conditions, add 20 mg of the Zn-Salen-based ionic polymer catalyst and 3 mmol of epibromohydrin into a 10 mL stainless steel reactor. After sealing the reactor, use CO2 gas to slowly charge and discharge the gas repeatedly 3 times. Then charge CO2 to make the pressure stable at 1.0 MPa. Place the reactor in a constant temperature stirrer at 120 °C and stir for 12 h. After the reaction is completed, cool it in an ice-water bath and slowly release the unreacted CO2. Subsequently, add 5 mL of ethyl acetate to the reactor and separate the solid catalyst by centrifugation. Take an appropriate amount of the supernatant for gas chromatography analysis, refer to Figure 4 ; The calculated conversion rate is 99.9%, and the selectivity is 97.5%.

[0053] Example 5: The catalyst catalyzes the cycloaddition reaction of CO2 and propylene oxide

[0054] Under room temperature conditions, add 20 mg of the Zn-Salen-based ionic polymer catalyst and 3 mmol of propylene oxide into a 10 mL stainless steel reactor. After sealing the reactor, use CO2 gas to slowly charge and discharge the gas repeatedly 3 times. Then charge CO2 to make the pressure stable at 1.0 MPa. Place the reactor in a constant temperature stirrer at 120 °C and stir for 12 h. After the reaction is completed, cool it in an ice-water bath and slowly release the unreacted CO2. Subsequently, add 5 mL of ethyl acetate to the reactor and separate the solid catalyst by centrifugation. Take an appropriate amount of the supernatant for gas chromatography analysis, refer to Figure 5 ; The calculated conversion rate is 96.7%, and the selectivity is 98.8.

[0055] Example 6: Catalyze the reaction of carbon dioxide and epoxybutane to synthesize cyclic carbonate

[0056] Under room temperature conditions, add 20 mg of the Zn-Salen-based ionic polymer catalyst and 3 mmol of epoxybutane into a 10 mL stainless steel reactor. After sealing the reactor, use CO2 gas to slowly charge and discharge the gas repeatedly 3 times. Then charge CO2 to make the pressure stable at 1.0 MPa. Place the reactor in a constant temperature stirrer at 120 °C and stir for 12 h. After the reaction is completed, cool it in an ice-water bath and slowly release the unreacted CO2. Subsequently, add 5 mL of ethyl acetate to the reactor and separate the solid catalyst by centrifugation. Take an appropriate amount of the supernatant for gas chromatography analysis, refer to Figure 6 ; The calculated conversion rate is 70.7%, and the selectivity is 99.2%.

[0057] Example 7: Catalyze the reaction of carbon dioxide and phenyl glycidyl ether to synthesize cyclic carbonate

[0058] At room temperature, 20 mg of Zn-Salen-based ionic polymer catalyst and 3 mmol of phenyl glycidyl ether were added to a 10 mL stainless steel reactor. After sealing the reactor, CO2 gas was repeatedly and slowly charged and discharged 3 times. Then CO2 was charged to make the pressure stable at 1.0 MPa. The reactor was placed in a constant temperature stirrer at 120 °C and stirred for 24 h. After the reaction ended, the unreacted CO2 was slowly released after cooling in an ice-water bath. Subsequently, 5 mL of ethyl acetate was added to the reactor and the solid catalyst was separated by centrifugation. An appropriate amount of the supernatant was taken for gas chromatography analysis, referring to Figure 7 ; The calculated conversion rate was 96.2%, and the selectivity was 99.9%.

[0059] Example 8: Catalytic reaction of carbon dioxide with styrene oxide to synthesize cyclic carbonate

[0060] At room temperature, 20 mg of Zn-Salen-based ionic polymer catalyst and 3 mmol of styrene oxide were added to a 10 mL stainless steel reactor. After sealing the reactor, CO2 gas was repeatedly and slowly charged and discharged 3 times. Then CO2 was charged to make the pressure stable at 1.0 MPa. The reactor was placed in a constant temperature stirrer at 120 °C and stirred for 24 h. After the reaction ended, the unreacted CO2 was slowly released after cooling in an ice-water bath. Subsequently, 5 mL of ethyl acetate was added to the reactor and the solid catalyst was separated by centrifugation. An appropriate amount of the supernatant was taken for gas chromatography analysis, referring to Figure 8 ; The calculated conversion rate was 82.5%, and the selectivity was 98.4%.

[0061] Example 9: Catalytic reaction of carbon dioxide with epichlorohydrin to synthesize cyclic carbonate

[0062] At room temperature, 20 mg of the Zn-Salen-based ionic polymer catalyst recovered for the fifth time and 3 mmol of epichlorohydrin were added to a 10 mL stainless steel reactor. After sealing the reactor, CO2 gas was repeatedly and slowly charged and discharged 3 times. Then CO2 was charged to make the pressure stable at 1.0 MPa. The reactor was placed in a constant temperature stirrer at 120 °C and stirred for 12 h. After the reaction ended, the unreacted CO2 was slowly released after cooling in an ice-water bath. Subsequently, 5 mL of ethyl acetate was added to the reactor and the solid catalyst was separated by centrifugation. An appropriate amount of the supernatant was taken for gas chromatography analysis, referring to Figure 9 ; The calculated conversion rate was 90.1%, and the selectivity was 96.3%.

[0063] Example 10: Catalytic reaction of carbon dioxide with epichlorohydrin to synthesize cyclic carbonate

[0064] Under room temperature conditions, 20 mg of Zn-Salen-based ionic polymer catalyst and 3 mmol of epichlorohydrin were added to a 10 mL stainless steel autoclave. After sealing the autoclave, the autoclave was repeatedly filled and emptied slowly 3 times with a mixed gas of 15% CO2 + 85% N2 by volume. Then the above-mentioned mixed gas was charged to make the pressure stable at 3.0 MPa. The autoclave was placed in a thermostatic stirrer at 120 °C and stirred for 12 h. After the reaction ended, the unreacted CO2 was slowly released after cooling in an ice-water bath. Subsequently, 5 mL of ethyl acetate was added to the autoclave, and the solid catalyst was separated by centrifugation. An appropriate amount of the supernatant was taken for gas chromatography analysis, referring to Figure 10 ; The calculated conversion rate was 87.5% and the selectivity was 94.6%.

Claims

1. A Zn-Salen-based ionomer catalyst, characterized in that: Its structural formula is shown in formula (I):

2. The method for preparing the Zn-Salen-based ionomer catalyst according to claim 1, characterized in that: The method includes the following steps in sequence: 1) Synthesizing a pyridinium ionic liquid functionalized Zn-Salen complex having a dialdehyde group using 3,4-diamino-1-benzylpyridinium bromide, 4-hydroxyisophthalaldehyde, and zinc acetate as raw materials; 2) polymerizing the pyridinium ionic liquid functionalized Zn-Salen complex having a dialdehyde group prepared in step 1) with phthalamidine hydrochloride at 60-120° C. to obtain the product.

3. The method for preparing the Zn-Salen-based ionomer catalyst according to claim 2, wherein: The following steps are involved: (1) 3,4-diamino-1-benzylpyridinium bromide and 4-hydroxyisophthalaldehyde in a molar ratio of 1:1-2 were added to a round-bottom flask containing methanol, stirred at room temperature for 1 hour, and then zinc acetate dihydrate was added; the mixture was then placed in a 60°C reaction bath and stirred for 16 hours; the resulting precipitate was washed several times with methanol, ethyl acetate, acetone, and petroleum ether, and then vacuum-dried at 80°C for 24 hours to obtain a pyridinium ionic liquid functionalized Zn-Salen complex containing a dialdehyde group; (2) The pyridinium ionic liquid functionalized Zn-Salen complex containing a dialdehyde group prepared in step 1) and phthalamidine hydrochloride are added to a thick-walled pressure-resistant bottle containing dimethyl sulfoxide and deionized water in a molar ratio of 1:1-3, followed by adding cesium carbonate. The mixture is placed in a constant temperature magnetic stirrer and reacted for 4.5 days using a programmed temperature method. After cooling to room temperature, the obtained solid is acid-washed and solvent-washed, and finally vacuum-dried at 120°C for 12 hours to obtain a Zn-Salen-based ionic polymer catalyst.

4. The method for preparing the Zn-Salen-based ionomer catalyst according to claim 2, wherein: In step 2), the molar ratio of the phthalamidine hydrochloride to the cesium carbonate is 1:1-3.

5. The method for preparing the Zn-Salen-based ionomer catalyst according to claim 2, wherein: In step 1), the molar ratio of the 3,4-diamino-1-benzylpyridinium bromide to zinc acetate dihydrate is 1:1-2.

5.

6. The method for preparing the Zn-Salen-based ionomer catalyst according to claim 2, wherein: Step 2) The programmed temperature method is as follows: the heating rate is 10°C / min, when it reaches 60°C, it is maintained for 12 hours, then it reaches 80°C and is maintained for 12 hours, then it reaches 100°C and is maintained for 12 hours, and finally it is heated to 120°C and the reaction is continued for 3 days.

7. The method for preparing the Zn-Salen-based ionomer catalyst according to claim 2, wherein: The solvent used in the pickling step 2) is a 1-2 mmol / L HCl aqueous solution or a 1-2 mmol / L HBr aqueous solution.

8. The method for preparing the Zn-Salen-based ionomer catalyst according to claim 3, wherein: Step 2) The washing is carried out by combining suction filtration and Soxhlet extraction. The suction filtration and washing solvent is 60-100 mL of deionized water, tetrahydrofuran and acetone. The Soxhlet extraction uses 250 mL of tetrahydrofuran as solvent.

9. The Zn-Salen-based ionomer catalyst according to claim 1 is used to catalyze the cycloaddition reaction of epoxides with CO2 to produce cyclic carbonates.

10. The Zn-Salen-based ionomer catalyst according to claim 9 is used to catalyze the synthesis of cyclic carbonates from CO2 and epoxides, characterized in that: The method comprises the following steps in sequence: without adding any solvent or co-catalyst, reacting CO2 with an epoxide of the structural formula described in formula (II) at a volume concentration of 15 to 100% in the presence of 20 mg of a catalyst, at a pressure of 0.5 to 6.0 MPa and a reaction temperature of 80 to 150° C., with constant temperature stirring for 8 to 72 hours to obtain a cyclic carbonate of the structural formula described in formula (III); The epoxide in the above steps has the structural formula as described in formula (II): The cyclic carbonate described in the above steps has the structural formula as described in formula (III):

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