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

Abstract

The present invention discloses a preparation method and application of a catalyst based on a metal-salen polymer, and belongs to the field of catalyst preparation technology. The present invention uses a surfactant micelle solution to in-situ compound a salen polymer with silicon oxide to obtain salen-POP@SiO2, and then obtains a catalyst M-salen-POP@SiO2 based on a metal-salen polymer through a coordination reaction. In the catalyst, the metal-salen site can be fully exposed, and silicon oxide is rich in hydroxyl groups, which can form hydrogen bonds with carbon dioxide, which is beneficial to the enrichment of reactants. The obtained catalyst cooperates with a temperature-responsive ionic liquid to catalyze the reaction of carbon dioxide and epoxy compounds to prepare cyclic carbonates under solvent-free conditions, and the catalyst is easy to recycle, the product purification is simple, and has good application prospects.

Description

Technical Field

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

[0002] The conversion of carbon dioxide, a major greenhouse gas, into high-value-added chemicals has attracted widespread attention. The reaction of CO2 with epoxides to prepare cyclic carbonates offers the advantages of no byproducts and 100% atomic efficiency, making it an efficient and green strategy for CO2 resource utilization. Furthermore, cyclic carbonates are widely used in polymers, solvents, battery electrolytes, and other fields. Therefore, the reaction of CO2 with epoxides to prepare cyclic carbonates holds great significance in fine chemicals and industrial synthesis.

[0003] Metal-salen catalysts are complexes formed by the condensation reaction of salicylaldehyde and diamine to form a tetradentate ligand, which is then coordinated with a metal ion (such as Co, Zn, or Al). They exhibit high activity and structural tunability, making them widely used in the carbon dioxide cycloaddition reaction. In their article, "Salen-Co(III) Complex Catalyzes the Formation of Cyclic Carbonates from CO2 and Ethylene Oxide," Wang Yi et al. directly applied the salen-Co(III) complex to the reaction of ethylene oxide to form cyclic carbonates. However, the salen-Co(III) complex is difficult to separate and recycle. In their article, "Synthesis of Covalent Organic Frameworks via In Situ Salen Skeleton Formation for Catalytic Applications" (J. Mater. Chem. A, 2019, 7, 5482), Li He et al. reported a covalent organic framework-based catalyst, COF-salen–M, which synergizes with TBAB to efficiently catalyze carbon dioxide cycloaddition reactions. However, the synthesis conditions of the covalent organic framework are demanding, and the yield is low. 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", Cao Rong et al. quaternized benzyl chloride-functionalized Al-salen with an imidazolyl triazine compound to obtain a porous ionic polymer containing Al-salen and applied it to the carbon dioxide cycloaddition reaction. However, the polymer is connected by ionic bonds and has a low specific surface area, which is not conducive to the exposure of active sites and limits its catalytic activity. Summary of the Invention

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

[0005] To achieve the purpose of the invention, the present invention provides a method for preparing a catalyst based on a metal-salen polymer, comprising the following steps:

[0006] (1) Dissolve hexadecyltrimethylammonium bromide and sodium lauryl sulfate in deionized water and sonicate for 0.5-1 h to obtain a micellar solution;

[0007] The salicylaldehyde derivative and the o-diamine monomer are dissolved in polar organic solvents respectively, and then added to equal volumes of the micelle solution, and ultrasonicated for 0.5-1 h to obtain a first solution and a second solution respectively;

[0008] 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;

[0009] (2) Adding ethyl 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;

[0010] (3) Disperse salen-POP@SiO2 in an ethanol solution containing transition metal acetate, stir and reflux for 8-24 hours. After the reaction is completed, filter and wash, and the resulting solid is vacuum dried for 8-24 hours to obtain the catalyst M-salen-POP@SiO2, which is a metal-salen polymer-based catalyst.

[0011] Furthermore, in step (1), the structural formula of the salicylaldehyde derivative is as follows:

[0012]

[0013] The o-diamine monomer is one of ethylenediamine, o-phenylenediamine or 1,2-cyclohexanediamine; and the polar organic solvent is one of dimethyl sulfoxide, N'N-dimethylformamide or dioxane.

[0014] Furthermore, in the step (1), the molar ratio of sodium lauryl sulfate, hexadecyltrimethylammonium 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 ortho-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 ortho-diamine monomer in the second solution is 2.5-9.8 mmol / L.

[0015] Furthermore, in the step (2), the volume ratio of ethyl 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.

[0016] Furthermore, in 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.

[0017] Another object of the present invention is to apply the metal-salen polymer-based catalyst prepared by the above method in conjunction with a temperature-responsive ionic liquid to the reaction of carbon dioxide with an epoxy compound to prepare a cyclic carbonate.

[0018] The beneficial effects of the present invention compared to the prior art are as follows:

[0019] 1. The technical solution provided by the present invention is to uniformly coat the salen polymer onto silicon oxide through an aldehyde-amine condensation reaction and a silicone grease hydrolysis reaction in a micellar solution, and then prepare a metal-salen polymer-based catalyst through a metal coordination reaction, so that the metal-salen site can be fully exposed. In addition, silicon oxide is rich in hydroxyl groups and can form hydrogen bonds with carbon dioxide, which is beneficial to the enrichment of reactants and further improves the catalytic efficiency.

[0020] 2. This invention immobilizes the salen polymer on a silica support to form a stable composite material. Its high specific surface area and hierarchical pore structure allow the catalyst to be recovered by simple filtration. The catalyst can be separated by centrifugation after the reaction, simplifying product purification and making it suitable for industrial applications.

[0021] 3. The present invention adopts micellar solution in-situ compounding technology to carry out aldehyde-amine condensation and tetraethyl orthosilicate hydrolysis reaction at room temperature, avoiding high temperature or high pressure conditions. At the same time, by adjusting the surfactant (sodium lauryl sulfate and hexadecyltrimethylammonium bromide molar ratio of 1:30-40), the stability of the micelle is optimized to ensure uniform loading of the salen-polymer.

[0022] 4. The present invention uses a metal-salen polymer-based catalyst in synergistic application with a temperature-responsive ionic liquid to efficiently catalyze the reaction of carbon dioxide with an epoxy compound to prepare cyclic carbonates in the absence of a solvent. The yield of the target product can reach 99%, and the catalyst is easy to recover, and the product purification is simple and easy to separate, showing good application prospects in actual production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the nitrogen adsorption-desorption isotherm of Cat2 obtained in Example 2 at 77K;

[0024] Figure 2 This is the thermogravimetric curve of Cat2 obtained in Example 2 under air atmosphere;

[0025] Figure 3 This is a transmission electron microscope photograph of Cat2 obtained in Example 2. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and examples, but the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments obtained without creative work all fall within the scope of protection of the present invention. Example 1

[0027] (1) 30 mmol of hexadecyltrimethylammonium bromide and 1 mmol of sodium dodecyl sulfate were dissolved in 270 mL of deionized water and ultrasonicated for 0.5 h to obtain a micellar solution; 0.05 mmol of aldehyde A and 0.075 mmol of ethylenediamine were dissolved in 0.5 mL of dimethyl sulfoxide, respectively, and then added to 30 mL of the micellar solution and ultrasonicated for 0.5 h to obtain a first solution and a second solution respectively; the obtained first solution and the obtained second solution were mixed, stirred for 0.5 h, and allowed to stand at room temperature for 8 h to obtain a third solution.

[0028] (2) 0.6 mL of tetraethyl orthosilicate was added to the third solution obtained in step (1), and the mixture was stirred at room temperature for 24 h. After the reaction, the mixture was filtered and washed to obtain a solid powder. Subsequently, the solid powder was added to 200 mL of 25 g / L ammonium chloride solution, stirred and refluxed for 8 h, and after the reaction, the mixture was filtered and washed to obtain salen-POP@SiO2.

[0029] (3) Disperse 200 mg of salen-POP@SiO2 in 10 mL of ethanol solution containing 0.2 mmol of copper acetate, stir and reflux for 8 h. After the reaction is completed, filter and wash, and the resulting solid is dried in a vacuum oven for 8 h to obtain the catalyst Cu-salen-POP@SiO2, named Cat1. Example 2

[0030] (1) 32 mmol of hexadecyltrimethylammonium bromide and 1 mmol of sodium dodecyl sulfate were dissolved in 300 mL of deionized water and ultrasonicated for 0.75 h to obtain a micellar solution; 0.1 mmol of aldehyde B and 0.15 mmol of 1,2-cyclohexanediamine were dissolved in 0.5 mL of N'N-dimethylformamide, and then added to 30 mL of the micellar solution and ultrasonicated 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 allowed to stand at room temperature for 16 h to obtain a third solution.

[0031] (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 and wash to obtain a solid powder. Subsequently, the obtained solid powder is added to 200 mL of 35 g / L ammonium nitrate ethanol solution, stirred and refluxed for 16 h. After the reaction is completed, filter and wash to obtain salen-POP@SiO2.

[0032] (3) Disperse 200 mg of salen-POP@SiO2 in 10 mL of ethanol solution containing 0.35 mmol of zinc acetate and stir under reflux for 16 h. After the reaction is completed, filter and wash the solid. Dry the solid in a vacuum oven for 16 h to obtain the catalyst Zn-salen-POP@SiO2, named Cat2. Example 3

[0033] (1) Dissolve 40 mmol of hexadecyltrimethylammonium bromide and 1 mmol of sodium dodecyl sulfate in 324 mL of deionized water and sonicate for 1 h to obtain a micellar 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 micellar solution and sonicate for 1 h to obtain the first solution and the second solution respectively; mix the first solution and the second solution, stir for 1 h, and let it stand at room temperature for 24 h to obtain the third solution.

[0034] (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 is completed, filter and wash to obtain a solid powder. Subsequently, add the solid powder to 200 mL of 50 g / L ammonium sulfate solution, stir and reflux for 24 h, and after the reaction is completed, filter and wash to obtain salen-POP@SiO2.

[0035] (3) 200 mg of salen-POP@SiO2 was dispersed in 10 mL of ethanol solution containing 0.5 mmol of cobalt acetate and stirred under reflux for 24 h. After the reaction was completed, the solution was filtered and washed. The resulting solid was dried in a vacuum oven for 24 h to obtain the catalyst Co-salen-POP@SiO2, which was named Cat3. Example 4

[0036] 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 reactor, sealed, and filled with 2 MPa of carbon dioxide. The reaction was then transferred to a 120°C oil bath and stirred for 8 hours. After the reaction, the reactor was cooled in an ice-water bath. Unreacted carbon dioxide was then released, and the reaction liquid was transferred to a centrifuge tube containing an internal standard (biphenyl). The reaction was centrifuged, and the supernatant was analyzed by gas chromatography. The yield of propylene carbonate was 86%. Example 5

[0037] Similar to Example 4, Cat2 obtained in Example 2 was used to replace Cat1 in Example 4, and other reaction conditions and processes remained unchanged. The yield of propylene carbonate was 99%. Example 6

[0038] Similar to Example 4, Cat3 obtained in Example 3 was used to replace Cat1 in Example 4, and other reaction conditions and processes remained unchanged. The yield of propylene carbonate was 92%. Example 7

[0039] Test the universality of catalyst Cat2: Similar to Example 6, epichlorohydrin, 1,2-epoxyhexane, and styrene oxide were used as reaction substrates to replace the propylene oxide in Example 5, while other conditions remained unchanged. The conversion rates of the substrates used are shown in the table below.

[0040] Table 1. Reaction results of the cycloaddition reaction of other epoxy compounds with carbon dioxide catalyzed by Cat2 in Example 7:

[0041] Comparative Example 1

[0042] The difference from Example 2 is that no micelle solution is used. The specific experimental scheme is as follows:

[0043] (1) 0.1 mmol of aldehyde B and 0.15 mmol of cyclohexanediamine were dissolved in 0.5 mL of N'N-dimethylformamide, respectively, and then added to 30 mL of deionized water. The mixture was ultrasonicated for 0.75 h to obtain a first solution and a second solution, respectively. The first solution and the second solution were mixed, stirred for 0.75 h, and allowed to stand at room temperature for 16 h to obtain a third solution.

[0044] (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 and wash to obtain a solid powder. Subsequently, the obtained solid powder is added to 200 mL of 35 g / L ammonium nitrate ethanol solution, stirred and refluxed for 16 h. After the reaction is completed, filter and wash to obtain salen-POP@SiO2.

[0045] (3) 200 mg of salen-POP@SiO2 was dispersed in 10 mL of ethanol solution containing 0.35 mmol of zinc acetate and stirred and refluxed for 16 h. After the reaction was completed, the solution was filtered and washed. The resulting solid was dried in a vacuum oven for 16 h to obtain the comparative catalyst Zn-salen-POP@SiO2, which was named Cat2-1. Comparative Example 2

[0046] The difference from Example 2 is that the silicon oxide precursor TEOS is not added. The specific experimental scheme is as follows:

[0047] (1) 32 mmol of hexadecyltrimethylammonium bromide and 1 mmol of sodium dodecyl sulfate were dissolved in 300 mL of deionized water and ultrasonicated for 0.75 h to obtain a micellar solution; 0.1 mmol of aldehyde B and 0.15 mmol of cyclohexanediamine were dissolved in 0.5 mL of N'N-dimethylformamide, and then added to 30 mL of the demicelle solution and ultrasonicated 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 allowed to stand at room temperature for 16 h to obtain a third solution.

[0048] (2) The reaction was stirred at room temperature for 36 h. After the reaction was completed, the mixture was filtered and washed to obtain a solid powder. Subsequently, the obtained solid powder was added to 200 mL of a 35 g / L ammonium nitrate ethanol solution and stirred and refluxed for 16 h. After the reaction was completed, the mixture was filtered and washed to obtain salen-POP.

[0049] (3) The salen-POP obtained in (2) was dispersed in 10 mL of ethanol solution containing 0.35 mmol of zinc acetate and stirred under reflux for 16 h. After the reaction was completed, the solution was filtered and washed. The solid was dried in a vacuum oven for 16 h to obtain a comparative catalyst Zn-salen-POP, which was named Cat2-2. Comparative Example 3

[0050] (1) 60 mmol of hexadecyltrimethylammonium bromide and 1 mmol of sodium dodecyl sulfate were dissolved in 300 mL of deionized water and ultrasonicated for 0.75 h to obtain a micellar solution; 0.1 mmol of aldehyde B was dissolved in 0.5 mL of N'N-dimethylformamide and then added to 30 mL of the micellar solution and ultrasonicated for 0.75 h to obtain a first solution; 0.15 mmol of cyclohexanediamine was dissolved in 0.5 mL of N'N-dimethylformamide and then added to 30 mL of the micellar solution and ultrasonicated for 0.75 h to obtain a second solution; the first solution and the second solution were mixed, stirred for 0.75 h, and allowed to stand at room temperature for 16 h to obtain a third solution.

[0051] (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 and wash to obtain a solid powder. Subsequently, the obtained solid powder is added to 200 mL of 35 g / L ammonium nitrate ethanol solution, stirred and refluxed for 16 h. After the reaction is completed, filter and wash to obtain salen-POP@SiO2.

[0052] (3) Disperse 200 mg of salen-POP@SiO2 in 10 mL of ethanol solution containing 0.35 mmol of zinc acetate and stir under reflux for 16 h. After the reaction is completed, filter and wash the solid. Dry the solid in a vacuum oven for 16 h to obtain the catalyst Zn-salen-POP@SiO2, which is named Cat2-3. Comparative Example 4

[0053] (1) Dissolve 10 mmol hexadecyltrimethylammonium bromide and 1 mmol sodium dodecyl sulfate in 300 mL deionized water and sonicate for 0.75 h to obtain a micellar solution; dissolve 0.1 mmol aldehyde B in 0.5 mL N'N-dimethylformamide and then add the mixture to 30 mL micellar solution and sonicate for 0.75 h to obtain a first solution; dissolve 0.15 mmol cyclohexanediamine in 0.5 mL N'N-dimethylformamide and then add the mixture to 30 mL micellar solution and sonicate for 0.75 h to obtain a second solution; mix the first solution and the second solution, stir for 0.75 h, and let stand at room temperature for 16 h to obtain a third solution.

[0054] (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 and wash to obtain a solid powder. Subsequently, the obtained solid powder is added to 200 mL of 35 g / L ammonium nitrate ethanol solution, stirred and refluxed for 16 h. After the reaction is completed, filter and wash to obtain salen-POP@SiO2.

[0055] (3) Disperse 200 mg of salen-POP@SiO2 in 10 mL of ethanol solution containing 0.35 mmol of zinc acetate and stir under reflux for 16 h. After the reaction is completed, filter and wash the solid. Dry the solid in a vacuum oven for 16 h to obtain the catalyst Zn-salen-POP@SiO2, which is named Cat2-4. Comparative Example 5

[0056] Similar to Example 4, the catalysts Cat2-1 / Cat2-2 / Cat2-3 / Cat2-4 obtained in Comparative Examples 1-4 were used to replace Cat1 in Example 4. Other reaction conditions and processes remained unchanged. The yields of propylene carbonate are shown in the table below.

[0057] Table 2 Catalytic reaction results of the catalysts obtained in Comparative Examples 1-4 for the cycloaddition reaction of carbon dioxide and propylene oxide:

[0058]

[0059] Attachment Figure 1 The nitrogen isothermal adsorption-desorption curve of Cat2 at 77 K is given. The adsorption amount in the low-pressure region increases sharply and contains a hysteresis loop, indicating that the material has a multi-level pore structure, with a BET specific surface area of ​​871 m 2 / g, with a total pore volume of 1.3 cm 3 / g.

[0060] Attachment Figure 2 The thermogravimetric curve of Cat2 in air atmosphere is given. The catalyst begins to lose weight above 290 ℃, indicating that the catalyst has good thermal stability. The weight loss between 290-600 ℃ is attributed to the decomposition of the polymer. It can be seen that the content of salen-POP in the catalyst is about 25%.

[0061] Attachment Figure 3 The TEM image of Cat2 is given, showing that it is composed of 30-40 nm nanospheres and that Zn-salen-POP can be well composited with SiO2.

[0062] 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 it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, 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 lauryl sulfate in deionized water and sonicate for 0.5-1 h to obtain a micellar solution; The salicylaldehyde derivative and the o-diamine monomer are dissolved in polar organic solvents respectively, and then added to equal volumes of the micelle solution, and ultrasonicated for 0.5-1 h 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 ethyl 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) Disperse salen-POP@SiO2 in an ethanol solution containing transition metal acetate, stir and reflux for 8-24 hours. After the reaction is completed, filter and wash, and the resulting solid is vacuum dried for 8-24 hours to obtain the catalyst M-salen-POP@SiO2, which is a metal-salen polymer-based catalyst.

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: described , 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 metal-salen polymer-based catalyst according to claim 1, wherein: In the step (1), the molar ratio of sodium lauryl sulfate, hexadecyltrimethylammonium 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 ortho-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 ortho-diamine monomer in the second solution is 2.5-9.8 mmol / L.

4. The method for preparing a metal-salen polymer-based catalyst according to claim 1, wherein: In the step (2), the volume ratio of ethyl 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 metal-salen polymer-based catalyst according to claim 1, wherein: 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 metal-salen polymer-based catalyst prepared 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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