Preparation method and application of catalyst based on metal-salen polymer

Abstract

The invention discloses a preparation method and application of a catalyst based on a metal-salen polymer, and belongs to the technical field of catalyst preparation. The preparation method comprises the following steps: carrying out in-situ compounding on a salen polymer and silicon oxide through a surfactant micelle solution to obtain salen-POP coated SiO2, and then carrying out a coordination reaction to prepare the metal-salen polymer-based catalyst M-salen-POP coated SiO2. In the catalyst, a metal-salen site can be fully exposed, and silicon oxide is rich in hydroxyl and can form a hydrogen bond with carbon dioxide, so that enrichment of reactants is facilitated. The obtained catalyst cooperates with the temperature response ionic liquid, the reaction of carbon dioxide and an epoxy compound can be catalyzed under the solvent-free condition to prepare cyclic carbonate, the catalyst is easy to recover, the product is simple to purify, and the catalyst has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and particularly relates to a preparation method and application of a catalyst based on metal-salen polymer. Background Art

[0002] The conversion of the main greenhouse gas carbon dioxide into high-value-added chemicals has attracted extensive attention. Among them, the reaction of CO 2 with epoxides to prepare cyclic carbonates has the advantages of no by-products generation and 100% atom utilization rate, and is an efficient and green CO 2 resource utilization strategy. In addition, cyclic carbonates are widely used in fields such as polymers, solvents, battery electrolytes, etc. Therefore, the reaction of carbon dioxide with epoxides to prepare cyclic carbonates is of great significance in fine chemical industry and industrial synthesis.

[0003] Metal-Salen catalysts are a class of complexes formed by the condensation reaction of salicylaldehyde and diamine to form a tetradentate ligand and then coordinating with metal ions (such as Co, Zn, Al, etc.), and have the advantages of high activity and adjustable structure, and are widely used in the field of carbon dioxide cycloaddition. Wang Yi et al. in the article "Salen-Co(Ⅲ) Complex Catalyzed CO 2In "Synthesis of cyclic carbonates from carbon dioxide and ethylene oxide", when the Salen-Co(III) complex was directly applied to the reaction of ethylene oxide to form cyclic carbonates, there were problems such as difficult separation of the Salen-Co(III) complex and difficulty in recycling. Li He et al. reported a COF-salen–M catalyst based on covalent organic framework materials in "Synthesis of covalent organic frameworks via in situ salen skeleton formation for catalytic applications" (J. Mater. Chem. A, 2019, 7, 5482). It could efficiently catalyze the cycloaddition reaction of carbon dioxide in synergy with TBAB, but the synthesis conditions of covalent organic framework materials were harsh and the yield was low. Cao Rong et al. obtained a porous ionic polymer containing Al-salen by quaternization reaction of benzyl chloride-functionalized Al-salen and imidazolyl triazine compounds in the article "A bifunctional cationic porous organic polymer based on a Salen-(Al) metalloligand for the cycloaddition of carbon dioxide to produce cyclic carbonates" and applied it to the cycloaddition reaction of carbon dioxide. However, the polymer was connected by ionic bonds and had a low specific surface area, which was not conducive to the exposure of active sites and limited its catalytic activity. Summary of the Invention

[0004] The object of the present invention is to provide a preparation method and application of a catalyst based on a metal-salen polymer. The catalyst based on the metal-salen polymer prepared by this method can synergistically act with a temperature-responsive ionic liquid to efficiently catalyze the reaction of carbon dioxide and epoxide under solvent-free conditions. The yield of cyclic carbonate can reach 99%. Moreover, the catalyst is easy to recycle, the product purification is simple, the catalyst has a large specific surface area, and the active sites are fully exposed.

[0005] To achieve the object of the invention, the present invention provides a preparation method of a catalyst based on a metal-salen polymer, comprising the following steps: (1) Dissolve cetyltrimethylammonium bromide and sodium dodecyl sulfate in deionized water and ultrasonicate for 0.5 - 1 h to obtain a micellar solution; Dissolve the salicylaldehyde derivative and the o-diamine monomer in polar organic solvents respectively, and then add them to the micellar solution of equal volume respectively and ultrasonicate for 0.5 - 1 h to obtain a first solution and a second solution respectively; Mix the first solution and the second solution, stir for 0.5 - 1 h, and let it stand at room temperature for 8 - 24 h to obtain the third solution; (2)Add tetraethyl orthosilicate to the third solution, and then stir and react at room temperature for 24 - 48 h; after the reaction, filter by suction, wash, and obtain solid powder; subsequently, add the obtained solid powder to the solution of ammonium salt, stir and reflux for 8 - 24 h, after the reaction, filter by suction, wash, and obtain salen-POP@SiO 2 ; (3)Disperse salen-POP@SiO 2 in the ethanol solution containing transition metal acetate, stir and reflux for 8 - 24 h, after the reaction, filter by suction, wash, and vacuum dry the obtained solid for 8 - 24 h to obtain the catalyst M-salen-POP@SiO 2 , that is, the catalyst based on metal-salen polymer.

[0006] Furthermore, in the step (1), the structural formula of the salicylaldehyde derivative is as follows:

[0007] The o-diamine monomer is one of ethylenediamine, o-phenylenediamine or 1,2-cyclohexanediamine; the polar organic solvent is one of dimethyl sulfoxide, N,N-dimethylformamide or dioxane.

[0008] Furthermore, in the step (1), the molar ratio of sodium dodecyl sulfate, cetyltrimethylammonium bromide, and deionized water is 1:30 - 40:15000 - 18000; the concentration of the salicylaldehyde derivative in the organic solvent is 0.1 - 0.4 mol / L, and the concentration of the o-diamine monomer in the organic solvent is 0.15 - 0.6 mol / L; the concentration of the salicylaldehyde derivative in the first solution is 1.6 - 6.6 mmol / L, and the concentration of the o-diamine monomer in the second solution is 2.5 - 9.8 mmol / L.

[0009] Furthermore, in the step (2), the volume ratio of tetraethyl orthosilicate to the third solution is 1 - 4:100; the ammonium salt is one of ammonium chloride, ammonium nitrate or ammonium sulfate; the concentration of the ammonium salt is 25 - 50 g / L.

[0010] Furthermore, in the step (3), the transition metal acetate is M(OAc) 2 , M is one of Cu, Zn or Co, and the dosage of the transition metal acetate is 1 - 2.5 mmol / g salen-POP@SiO 2 .

[0011] Another object of the present invention is to apply the catalyst based on metal-salen polymer prepared by the above method, and apply it in cooperation with a temperature-responsive ionic liquid to the reaction of carbon dioxide and epoxide to prepare cyclic carbonate.

[0012] The beneficial effects of the present invention compared with the prior art are as follows: 1. The technical solution provided by the present invention enables the salen-polymer to be uniformly coated on silica through the aldehyde-amine condensation reaction and silicone hydrolysis reaction in the micellar solution, and then a catalyst based on metal-salen polymer is prepared through a metal coordination reaction, so that the metal-salen sites can be fully exposed, and silica is rich in hydroxyl groups, which can form hydrogen bonds with carbon dioxide, facilitating the enrichment of reactants and further improving the catalytic efficiency.

[0013] 2. By fixing the salen polymer on the silica support to form a stable composite material, combined with the high specific surface area and hierarchical pore structure, the catalyst can be recovered by simple suction filtration. The catalyst can be separated by centrifugation after the reaction, and the product purification is simple, which is suitable for industrial application.

[0014] 3. The present invention adopts the in-situ composite technology of micellar solution to carry out the aldehyde-amine condensation reaction and the hydrolysis reaction of tetraethyl orthosilicate at room temperature, avoiding high temperature or high pressure conditions. At the same time, by adjusting the surfactant (the molar ratio of sodium dodecyl sulfate to cetyltrimethylammonium bromide is 1:30 - 40), the stability of the micelle is optimized to ensure the uniform loading of the salen-polymer.

[0015] 4. The catalyst based on metal-salen polymer of the present invention is applied in cooperation with a temperature-responsive ionic liquid, which can efficiently catalyze the reaction of carbon dioxide and epoxide to prepare cyclic carbonate under solvent-free conditions. The yield of the target product can reach 99%. Moreover, the catalyst is easy to recover, and the product purification is simple and easy to separate, showing good application prospects in actual production. Description of the Drawings

[0016] Figure 1 It is the nitrogen adsorption and desorption isotherm curve of Cat2 obtained in Example 2 at 77K; Figure 2 It is the thermogravimetric curve of Cat2 obtained in Example 2 in an air atmosphere; Figure 3 It is the transmission electron microscope photograph of Cat2 obtained in Example 2. Detailed Embodiments

[0017] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. However, the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only partial embodiments of the present invention. For those skilled in the art, without creative efforts, obtaining other similar embodiments will fall within the protection scope of the present invention. Example 1

[0018] (1) Dissolve 30 mmol of cetyltrimethylammonium bromide and 1 mmol of sodium dodecyl sulfate in 270 mL of deionized water, and ultrasonicate for 0.5 h to obtain a micellar solution; dissolve 0.05 mmol of aldehyde A and 0.075 mmol of ethylenediamine in 0.5 mL of dimethyl sulfoxide respectively, and then add them to 30 mL of the micellar solution respectively, and ultrasonicate for 0.5 h to obtain a first solution and a second solution accordingly; mix the obtained first solution and the obtained second solution, stir for 0.5 h, and stand at room temperature for 8 h to obtain a third solution.

[0019] (2) Add 0.6 mL of tetraethyl orthosilicate to the third solution obtained in step (1), and then stir and react at room temperature for 24 h. After the reaction is completed, filter by suction and wash to obtain a solid powder; subsequently, add the obtained solid powder to 200 mL of 25 g / L ammonium chloride solution, stir and reflux for 8 h. After the reaction is completed, filter by suction and wash to obtain salen-POP@SiO 2 .

[0020] (3) Disperse 200 mg of salen-POP@SiO 2 in 10 mL of an ethanol solution containing 0.2 mmol of copper acetate, stir and reflux for 8 h. After the reaction is completed, filter by suction and wash. The obtained solid is dried in a vacuum oven for 8 h to obtain the catalyst Cu-salen-POP@SiO 2 , named Cat1. Example 2

[0021] (1) Dissolve 32 mmol of cetyltrimethylammonium bromide and 1 mmol of sodium dodecyl sulfate in 300 mL of deionized water, and ultrasonicate for 0.75 h to obtain a micellar solution; dissolve 0.1 mmol of aldehyde B and 0.15 mmol of 1,2-cyclohexanediamine in 0.5 mL of N,N-dimethylformamide respectively, and then add them to 30 mL of the micellar solution respectively, and ultrasonicate for 0.75 h to obtain a first solution and a second solution accordingly; mix the obtained first solution and the obtained second solution, stir for 0.75 h, and stand at room temperature for 16 h to obtain a third solution.

[0022] (2) Add 1.2 mL of tetraethyl orthosilicate to the third solution obtained in (1), and then stir and react at room temperature for 36 h. After the reaction, filter by suction and wash to obtain a solid powder. Subsequently, add the obtained solid powder to 200 mL of an ethanol solution of ammonium nitrate with a concentration of 35 g / L, stir and reflux for 16 h. After the reaction, filter by suction and wash to obtain salen-POP@SiO 2 .

[0023] (3) Disperse 200 mg of salen-POP@SiO 2 in 10 mL of an ethanol solution containing 0.35 mmol of zinc acetate, stir and reflux for 16 h. After the reaction, filter by suction and wash. The obtained solid is dried in a vacuum oven for 16 h to obtain the catalyst Zn-salen-POP@SiO 2 , named Cat2. Example 3

[0024] (1) Dissolve 40 mmol of cetyltrimethylammonium bromide and 1 mmol of sodium dodecyl sulfate in 324 mL of deionized water, and ultrasonicate for 1 h to obtain a micelle solution; dissolve 0.2 mmol of aldehyde A and 0.3 mmol of o-phenylenediamine in 0.5 mL of dioxane respectively, and then add them to 30 mL of the micelle solution respectively, and ultrasonicate for 1 h to obtain the first solution and the second solution accordingly; mix the first solution and the second solution, stir for 1 h, and stand at room temperature for 24 h to obtain the third solution.

[0025] (2) Add 2.4 mL of tetraethyl orthosilicate to the third solution obtained in (1), and then stir and react at room temperature for 48 h. After the reaction, filter by suction and wash to obtain a solid powder. Subsequently, add the solid powder to 200 mL of a 50 g / L ammonium sulfate solution, stir and reflux for 24 h. After the reaction, filter by suction and wash to obtain salen-POP@SiO 2 .

[0026] (3) Disperse 200 mg of salen-POP@SiO 2 in 10 mL of an ethanol solution containing 0.5 mmol of cobalt acetate, stir and reflux for 24 h. After the reaction, filter by suction and wash. The obtained solid is dried in a vacuum oven for 24 h to obtain the catalyst Co-salen-POP@SiO 2 , named Cat3. Example 4

[0027] 10 mmol of propylene oxide, 50 mg of Cat1 obtained in Example 1, and 50 μmol of temperature-responsive ionic liquid were placed in a 15 mL stainless steel autoclave, sealed, filled with 2 MPa of carbon dioxide, and then transferred to an oil bath at 120 °C and stirred for 8 h. After the reaction, the autoclave was cooled with an ice-water bath. Subsequently, the unreacted carbon dioxide was released, and the reaction liquid was transferred to a centrifuge tube containing a certain internal standard (biphenyl). After centrifugation, the supernatant was taken for gas chromatography analysis, and the yield of propylene carbonate was 86%. Example 5

[0028] Similar to Example 4, Cat2 obtained in Example 2 was used to replace Cat1 in Example 4, and other reaction conditions and procedures remained unchanged. The yield of propylene carbonate was 99%. Example 6

[0029] Similar to Example 4, Cat3 obtained in Example 3 was used to replace Cat1 in Example 4, and other reaction conditions and procedures remained unchanged. The yield of propylene carbonate was 92%. Example 7

[0030] Testing the universality of catalyst Cat2: Similar to Example 6, epichlorohydrin, 1,2-epoxyhexane, and styrene oxide were used as reaction substrates to replace propylene oxide in Example 5, and other conditions remained unchanged. The conversion rates of the substrates used are shown in the following table.

[0031] Table 1. Reaction results of the cycloaddition reaction of other epoxides with carbon dioxide catalyzed by Cat2 in Example 7: Comparative Example 1

[0032] The difference from Example 2 is that no micellar solution is used. The specific experimental scheme is as follows: (1) 0.1 mmol of aldehyde B and 0.15 mmol of cyclohexanediamine were each dissolved in 0.5 mL of N,N-dimethylformamide, and then added to 30 mL of deionized water and sonicated for 0.75 h to obtain a first solution and a second solution respectively; the obtained first solution and the obtained second solution were mixed, stirred for 0.75 h, and left to stand at room temperature for 16 h to obtain a third solution.

[0033] (2) 1.2 mL of tetraethyl orthosilicate was added to the third solution obtained in (1), and then stirred at room temperature for 36 h. After the reaction, filtration and washing were carried out to obtain a solid powder. Subsequently, the obtained solid powder was added to 200 mL of an ethanol solution of 35 g / L ammonium nitrate, stirred and refluxed for 16 h. After the reaction, filtration and washing were carried out to obtain salen-POP@SiO 2 .

[0034] (3) Disperse 200 mg of salen-POP@SiO 2 in 10 mL of an ethanol solution containing 0.35 mmol of zinc acetate, stir and reflux for 16 h. After the reaction is completed, perform suction filtration and washing. The obtained solid is dried in a vacuum oven for 16 h to obtain the comparative catalyst Zn-salen-POP@SiO 2 , named Cat2-1. Comparative Example 2

[0035] The difference from Example 2 is that the silica precursor TEOS is not added. The specific experimental protocol is as follows: (1) Dissolve 32 mmol of cetyltrimethylammonium bromide and 1 mmol of sodium dodecyl sulfate in 300 mL of deionized water, and ultrasonicate for 0.75 h to obtain a micelle solution; dissolve 0.1 mmol of aldehyde B and 0.15 mmol of cyclohexanediamine in 0.5 mL of N,N-dimethylformamide respectively, and then add them to 30 mL of the de-micellized solution respectively, and ultrasonicate for 0.75 h to obtain a first solution and a second solution respectively; mix the obtained first solution and the obtained second solution, stir for 0.75 h, and stand at room temperature for 16 h to obtain a third solution.

[0036] (2) Stir and react at room temperature for 36 h. After the reaction is completed, perform suction filtration and washing to obtain a solid powder. Subsequently, add the obtained solid powder to 200 mL of an ethanol solution of 35 g / L ammonium nitrate, stir and reflux for 16 h. After the reaction is completed, perform suction filtration and washing to obtain salen-POP.

[0037] (3) Disperse the salen-POP obtained in (2) in 10 mL of an ethanol solution containing 0.35 mmol of zinc acetate, stir and reflux for 16 h. After the reaction is completed, perform suction filtration and washing. The obtained solid is dried in a vacuum oven for 16 h to obtain the comparative catalyst Zn-salen-POP, named Cat2-2. Comparative Example 3

[0038] (1) Dissolve 60 mmol of cetyltrimethylammonium bromide and 1 mmol of sodium dodecyl sulfate in 300 mL of deionized water, and ultrasonicate for 0.75 h to obtain a micellar solution; dissolve 0.1 mmol of aldehyde B in 0.5 mL of N,N-dimethylformamide, and then add it to 30 mL of the micellar solution and ultrasonicate for 0.75 h to obtain a first solution; dissolve 0.15 mmol of cyclohexanediamine in 0.5 mL of N,N-dimethylformamide, and then add it to 30 mL of the micellar solution and ultrasonicate for 0.75 h to obtain a second solution; mix the obtained first solution and the obtained second solution, stir for 0.75 h, and stand at room temperature for 16 h to obtain a third solution.

[0039] (2) Add 1.2 mL of tetraethyl orthosilicate to the third solution obtained in (1), and then stir and react at room temperature for 36 h. After the reaction is completed, filter by suction and wash to obtain a solid powder. Subsequently, add the obtained solid powder to 200 mL of an ethanol solution of 35 g / L ammonium nitrate, stir and reflux for 16 h. After the reaction is completed, filter by suction and wash to obtain salen-POP@SiO 2 .

[0040] (3) Disperse 200 mg of salen-POP@SiO 2 in 10 mL of an ethanol solution containing 0.35 mmol of zinc acetate, stir and reflux for 16 h. After the reaction is completed, filter by suction and wash. The obtained solid is dried in a vacuum oven for 16 h to obtain the catalyst Zn-salen-POP@SiO 2 , named Cat2-3. Comparative Example 4

[0041] (1) Dissolve 10 mmol of cetyltrimethylammonium bromide and 1 mmol of sodium dodecyl sulfate in 300 mL of deionized water, and ultrasonicate for 0.75 h to obtain a micellar solution; dissolve 0.1 mmol of aldehyde B in 0.5 mL of N,N-dimethylformamide, and then add it to 30 mL of the micellar solution and ultrasonicate for 0.75 h to obtain a first solution; dissolve 0.15 mmol of cyclohexanediamine in 0.5 mL of N,N-dimethylformamide, and then add it to 30 mL of the micellar solution and ultrasonicate for 0.75 h to obtain a second solution; mix the obtained first solution and the obtained second solution, stir for 0.75 h, and stand at room temperature for 16 h to obtain a third solution.

[0042] (2) Add 1.2 mL of tetraethyl orthosilicate to the third solution obtained in (1), and then stir and react at room temperature for 36 h. After the reaction, filter by suction and wash to obtain a solid powder. Subsequently, add the obtained solid powder to 200 mL of an ethanol solution of ammonium nitrate at 35 g / L, stir and reflux for 16 h. After the reaction, filter by suction and wash to obtain salen-POP@SiO 2 .

[0043] (3) Disperse 200 mg of salen-POP@SiO 2 in 10 mL of an ethanol solution containing 0.35 mmol of zinc acetate, stir and reflux for 16 h. After the reaction, filter by suction and wash. The obtained solid is dried in a vacuum oven for 16 h to obtain the catalyst Zn-salen-POP@SiO 2 , named Cat2-4. Comparative Example 5

[0044] Similar to Example 4, use the catalysts Cat2-1 / Cat2-2 / Cat2-3 / Cat2-4 obtained in Comparative Examples 1-4 to replace Cat1 in Example 4, and keep other reaction conditions and processes unchanged. The yield of propylene carbonate is shown in the following table.

[0045] Table 2 Catalytic reaction results of the catalysts obtained in Comparative Examples 1-4 for the cycloaddition reaction of carbon dioxide and propylene oxide:

[0046] Appendix Figure 1 The nitrogen isothermal adsorption and desorption curve of Cat2 at 77 K is given. The adsorption amount increases steeply in the low-pressure region and contains a hysteresis loop, indicating that the material has a hierarchical pore structure. The BET specific surface area is 871 m 2 / g, and the total pore volume is 1.3 cm 3 / g.

[0047] Appendix Figure 2 The thermogravimetric curve of Cat2 in an air atmosphere is given. The catalyst starts to lose weight above 290 °C, indicating that the catalyst has good thermal stability. The weight loss from 290 to 600 °C is attributed to the decomposition of the polymer, and it can be known that the content of salen-POP in the catalyst is about 25%.

[0048] Appendix Figure 3 The TEM photo of Cat2 is given, indicating that it is composed of nanospheres with a size of 30-40 nm, and Zn-salen-POP and SiO 2 can be well compounded.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a catalyst based on metal-salen polymer, characterized in that: The following steps are involved: (1) Dissolve hexadecyltrimethylammonium bromide and sodium dodecyl sulfate in deionized water and sonicate for 0.5-1 h to obtain a micellar solution; The salicylaldehyde derivative and the ortho-diamine monomer are dissolved in polar organic solvents respectively, and then added to equal volumes of micelle solutions respectively, and ultrasonicated for 0.5-1h to obtain a first solution and a second solution respectively; The first solution and the second solution are mixed, stirred for 0.5-1 h, and allowed to stand at room temperature for 8-24 h to obtain a third solution; (2) Adding tetraethyl orthosilicate to the third solution, and then stirring and reacting at room temperature for 24-48 hours; after the reaction is completed, filtering and washing to obtain a solid powder; then, adding the obtained solid powder to an ammonium salt solution, stirring and refluxing for 8-24 hours, and after the reaction is completed, filtering and washing to obtain salen-POP@SiO2; (3) Dispersing salen-POP@SiO2 in an ethanol solution containing transition metal acetate, stirring and reflux for 8-24 hours. After the reaction is completed, filtering and washing are performed, and the obtained solid is vacuum dried for 8-24 hours to obtain the catalyst M-salen-POP@SiO2, that is, a catalyst based on metal-salen polymer.

2. The method for preparing a metal-salen polymer-based catalyst according to claim 1, characterized in that: In the step (1), the structural formula of the salicylaldehyde derivative is as follows: ， The o-diamine monomer is one of ethylenediamine, o-phenylenediamine or 1,2-cyclohexanediamine; The polar organic solvent is one of dimethyl sulfoxide, N'N-dimethylformamide or dioxane.

3. The method for preparing a catalyst based on metal-salen polymer according to claim 1, characterized in that: In the step (1), the molar ratio of sodium dodecyl sulfate, hexadecyltrimethylammonium bromide and deionized water is 1:30-40:15000-18000; the concentration of salicylaldehyde derivative in the organic solvent is 0.1-0.4 mol / L, and the concentration of ortho-diamine monomer in the organic solvent is 0.15-0.6 mol / L; the concentration of salicylaldehyde derivative in the first solution is 1.6-6.6 mmol / L, and the concentration of ortho-diamine monomer in the second solution is 2.5-9.8 mmol / L.

4. The method for preparing a catalyst based on metal-salen polymer according to claim 1, characterized in that: In the step (2), the volume ratio of tetraethyl orthosilicate to the third solution is 1-4:100; the ammonium salt is one of ammonium chloride, ammonium nitrate or ammonium sulfate; and the concentration of the ammonium salt is 25-50 g / L.

5. The method for preparing a catalyst based on metal-salen polymer according to claim 1, characterized in that: In the step (3), the transition metal acetate is M(OAc)2, M is one of Cu, Zn or Co, and the amount of the transition metal acetate is 1-2.5 mmol / g salen-POP@SiO2.

6. Use of a catalyst based on a metal-salen polymer obtained by the method according to any one of claims 1 to 5, characterized in that: A metal-salen polymer-based catalyst is synergistically catalyzed with a temperature-responsive ionic liquid to react carbon dioxide with epoxides to prepare cyclic carbonates.

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