A multiphase catalyst, its preparation method and application

Abstract

The present application provides a heterogeneous catalyst, a preparation method thereof and an application thereof, belonging to the technical field of high molecular compounds. A metal Salen / phosphonium salt cross-linked polyionic liquid is prepared by cross-linking with diamine and then coordinating with a metal as a heterogeneous catalyst for the coupling reaction of CO2 and epoxides. Among them, the synergistic effect of the dual-functional active sites of aluminum as a Lewis acid site and halide anions as nucleophiles can promote the catalytic reaction. When it is used in the ring synthesis reaction of epoxides, it has the advantages of high conversion rate, high selectivity, etc.

Description

Technical Field

[0001] The present application relates to a heterogeneous catalyst, a preparation method thereof and an application thereof, belonging to the technical field of high molecular compounds. Background Art

[0002] Carbon dioxide mainly comes from the combustion of fossil fuels and is one of the main culprits causing the greenhouse effect. Therefore, to solve the catastrophic environmental problems such as global warming, glacier retreat and permafrost melting caused by the greenhouse effect, it is urgent to reduce the content of carbon dioxide in the air. Compared with adsorbing carbon dioxide, converting the adsorbed carbon dioxide into high-value-added chemicals, such as cyclic carbonates, is one of the most promising methods.

[0003] Cyclic carbonates are widely used as organic synthesis intermediates, polar aprotic solvents, electrolytes for lithium-ion batteries and monomers for polymers. Considering the thermodynamic stability and kinetic inertness of CO2, it is very necessary to design and develop advanced catalysts to promote the conversion of CO2 into high-value-added chemicals under mild conditions. Although the preparation of cyclic carbonates on homogeneous catalysts such as tetrabutylammonium bromide (TBAB) and potassium iodide (KI) has been industrialized, the reaction process requires high temperature (T>200 °C) and high pressure (carbon dioxide pressure > 6.0 MPa), the raw material source is limited, and the catalyst operation is cumbersome.

[0004] Salen ligands are an important class of metal complexes, which have a [O, N, N, O] tetradentate bis-Schiff base structure and can coordinate with various metal ions to form stable Salen metal complexes. Therefore, appropriate substituents can also be inserted on the benzene ring to anchor Salen on a solid support, thereby preparing a heterogeneous catalyst. In its catalytic application cases, the synthesis of cyclic carbonates by the coupling reaction of epoxides and CO2 has received increasing attention. However, the commonly used catalytic systems often have the disadvantages of harsh reaction conditions, low catalytic activity and difficulty in recycling. Summary of the Invention

[0005] In view of this, the present application first provides a heterogeneous catalyst, which has a highly cross-linked polymer backbone, abundant Lewis acid metal centers, active sites of nucleophilic active centers, and phosphonium-containing functional cations, and these functional cations endow the synthesized catalyst with the expected ability to fix carbon dioxide under mild and solvent-free catalytic conditions.

[0006] Specifically, the present application is achieved through the following scheme:

[0007] A heterogeneous catalyst, the structural formula of which is expressed as:

[0008] In the formula, M is Al, X is Cl, and the heterogeneous catalyst is denoted as PPh2PSt-Salen-Al.

[0009] The above-mentioned heterogeneous catalyst contains Lewis acid metal sites and halide ions, endowing the catalyst with bifunctionality. As a heterogeneous catalyst for carbon dioxide conversion, it has a highly cross-linked polymer backbone, abundant Lewis acid metal centers and active sites of nucleophilic active centers, as well as phosphonium-containing functional cations. These functional cations endow the synthesized catalyst with the expected ability to fix carbon dioxide under mild and solvent-free catalytic conditions; and the synergistic effect of the bifunctional active sites of aluminum as Lewis acid sites and halide anions as nucleophiles responds to its higher catalytic performance.

[0010] Meanwhile, the second object of the applicant is to provide a preparation method of the above-mentioned heterogeneous catalyst, including the following steps:

[0011] (1) Preparation of methyl salicylaldehyde-4-vinyl diphenylphosphonium salt: Dissolve 4-(diphenylphosphino)styrene (Ph2PSt) and 2,6-di-tert-butyl-4-methylphenol (BHT) in an appropriate amount of toluene, evacuate and fill with nitrogen, add a toluene solution of 5-chloromethyl salicylaldehyde (5-CS) under a nitrogen atmosphere, heat and reflux in an oil bath, and after the reaction is completed and cooled to room temperature, filter the solid and wash it with ethyl acetate to obtain methyl salicylaldehyde-4-vinyl diphenylphosphonium salt (Ph2PSt-5-CS);

[0012] (2) Preparation of methyl salicylaldehyde-4-vinyl diphenylphosphonium salt homopolymer: Dissolve Ph2PSt-5-CS and AIBN in chloroform, react at 65 °C under a N2 atmosphere, cool to room temperature, and sediment to obtain methyl salicylaldehyde-4-vinyl diphenylphosphonium salt homopolymer (PPh2PSt-5-CS);

[0013] (3) Synthesis of metal Salen / quaternary phosphonium salt polyionic liquid: PPh2PSt-5-CS is swollen in an appropriate amount of methanol solution, evacuated and filled with N2, slowly dropwise add a methanol solution of ethylenediamine under a N2 atmosphere, and react overnight at 65 °C. After cooling, filter the solid and wash it with CH2Cl2. Disperse the obtained solid in MeOH / CH2Cl2, evacuate and fill with N2, add a mixed solution of AlCl3 under a N2 atmosphere, stir at 45 °C for 12 hours, and after the mixture is cooled to room temperature, filter the solid, wash it with CH2Cl2, and dry it under vacuum to obtain the heterogeneous catalyst PPh2PSt-Salen-Al.

[0014] Furthermore, as a preference:

[0015] In step (1), the preparation method of 4-(diphenylphosphino)styrene is as follows: using magnesium powder as a catalyst, adding anhydrous THF under a N2 atmosphere, placing it in an ice-water bath and stirring. First, slowly add 4-bromostyrene dropwise under the condition of the ice-water bath, and after it is added dropwise completely, remove the ice-water bath and transfer it to room temperature for stirring for 2 hours; then, under the condition of the ice-water bath, slowly add diphenylphosphine chloride (Ph2PCl) dropwise, and after it is added dropwise completely, remove the ice-water bath and transfer it to room temperature for stirring overnight; then add an ice-water bath and quench with a saturated NH4Cl aqueous solution, extract the mixture with ether, filter and concentrate the organic layer, purify the residue by silica gel chromatography to obtain 4-(diphenylphosphino)styrene Ph2PSt. More preferably, in the silica gel chromatography purification, PE / DCM = 10:1 (PE is petroleum ether, DCM is dichloromethane).

[0016] The above process can be expressed by the following reaction formula:

[0017]

[0018] In step (1), the preparation method of 5-chloromethylsalicylaldehyde is as follows: at room temperature, add paraformaldehyde and salicylaldehyde to concentrated hydrochloric acid with stirring, then dropwise add phosphorus oxychloride within 1 h, continuously stir and react for 28 h. After the reaction is completed (white solid precipitates), perform suction filtration to obtain the crude product. Wash the filter cake with an appropriate amount of deionized water, then wash it with a 3% (mass fraction) NaHCO3 aqueous solution, and finally wash it with deionized water until neutral. Dry it under vacuum at 60 °C overnight, and then recrystallize it with petroleum ether, filter, wash, and dry to obtain 5-chloromethylsalicylaldehyde.

[0019] The above process can be expressed by the following reaction formula:

[0020]

[0021] For the third aspect purpose of the applicant, it provides the application of the above heterogeneous catalyst in the synthesis of epoxides. The heterogeneous catalyst is used for the cycloaddition reaction of an epoxy substrate and carbon dioxide to obtain a cyclic carbonate.

[0022] When the above catalyst is used in the cycloaddition reaction of an epoxide, the epoxide can be effectively converted into the corresponding cyclic carbonate, with considerable conversion and high selectivity. The selectivity of all cyclic carbonate products remains almost constant (>99%), and almost no by-products are observed in this reaction. Description of the Drawings

[0023] Figure 1 The solid state 13C spectrum of PPh2PSt-Salen-Al prepared in Example 1 13 C spectrum;

[0024] Figure 2For the PPh2PSt-Salen-Al prepared in Example 1 31 P NMR spectrum;

[0025] Figure 3 SEM images and elemental distribution maps of the product prepared in Example 1,

[0026] In the figure: (a) SEM image of PPh2PSt-5-CS, (b) SEM image of PPh2PSt-Salen-Al, (c) elemental distribution maps of C, P, N, O, Cl, and Al;

[0027] Figure 4 Gas adsorption isotherm curves of PPh2PSt-Salen-Al prepared in Example 1 at different temperatures;

[0028] Figure 5 For the CO2 isosteric heat of adsorption (Q st ) of PPh2PSt-Salen-Al prepared in Example 1;

[0029] Figure 6 NH3 temperature-programmed adsorption curve of PPh2PSt-Salen-Al prepared in Example 1;

[0030] Figure 7 CO2 temperature-programmed adsorption curve of PPh2PSt-Salen-Al prepared in Example 1. Specific implementation manners

[0031] In the following examples, the instruments and equipment used are as follows:

[0032] (1) Experimental instruments

[0033] The instruments used in the following examples are shown in Table 1.

[0034] Table 1: Characterization and testing instruments used in this case

[0035]

[0036] (2) Experimental reagents

[0037] The reagents used in the following examples are shown in Table 2.

[0038] Table 2: Reagents used in this case

[0039]

[0040]

[0041] Example 1

[0042] In this example, the preparation of the heterogeneous catalyst is carried out as follows:

[0043] (1) Synthesis of 4-(diphenylphosphino)styrene (Ph2PSt):

[0044] Place magnesium powder (1.41 g, 58.6 mmol, 2 eq) in a 250 mL round-bottom flask equipped with a magnetic stir bar. After adding anhydrous THF (30 mL) under a N2 atmosphere, place the round-bottom flask in an ice-water bath and stir. Slowly add 4-bromostyrene (6.63 g, 36.2 mmol, 1.2 eq) to the flask through a dropping funnel. After the addition is complete, stir at room temperature for 2 hours. Under the condition of an ice-water bath, slowly add diphenylphosphine chloride (Ph2PCl) (6.62 g, 30.3 mmol, 1 eq) to the round-bottom flask in the same manner. After the addition is complete, remove the ice-water bath and stir overnight at room temperature. Add an ice-water bath and quench with saturated NH4Cl aqueous solution. Extract the mixture with diethyl ether. Filter and concentrate the organic layer. Purify the residue by silica gel chromatography (PE / DCM = 10:1 v / v) to obtain white solid Ph2PSt (3.69 g, yield: 42.6%).

[0045] The above process can be represented by the following reaction formula:

[0046]

[0047] 1 1H NMR (400 MHz, Chloroform-d) δ 7.36–7.14 (Ar-H, 8H), 6.63 (–CH=, 1H), 5.70–5.20 (=CH2, 2H) ppm.

[0048] (2) Synthesis of 5-chloromethylsalicylaldehyde (5-Chloromethylsalicylaldehyde, 5-CS):

[0049] At room temperature (rt), add 200 mL of concentrated hydrochloric acid to a 500 mL three-necked round-bottom flask. Add paraformaldehyde (11.75 g, 0.39 mol) and salicylaldehyde (30 g, 0.25 mol) with stirring. Then, dropwise add 7.5 mL of phosphorus oxychloride (POCl3) within 1 h and continuously stir the reaction for 28 h. After the reaction is complete, a white solid precipitates. Filter the cake by suction filtration, wash it with an appropriate amount of deionized water, then wash it with a 3% (mass fraction) aqueous NaHCO3 solution, and finally wash it with deionized water until neutral. Dry the crude product of 5-chloromethylsalicylaldehyde under vacuum at 60 °C overnight, and then recrystallize it with petroleum ether, filter, wash, and dry to obtain the product 5-chloromethylsalicylaldehyde (26.53 g, yield: 63%).

[0050] The above process can be represented by the following reaction formula:

[0051]

[0052] 1 1H NMR (400 MHz, Chloroform-d) δ 11.07 (-OH, 1H), 9.90 (-CHO, 1H), 7.59 - 7.00 (Ar-H, 3H), 4.59 (-CH2-, 2H).

[0053] (3) Preparation of methyl salicylaldehyde-4-vinyl diphenylphosphonium salt (Ph2PSt-5-CS)

[0054] Dissolve Ph2PSt (2.0 g, 7.0 mmol) and 2,6-di-tert-butyl-4-methylphenol (BHT) (0.15 mg, 0.71 mmol) in an appropriate amount of toluene and place them in a two-necked round-bottom flask. Evacuate and fill with nitrogen. Add a toluene solution of 5-CS (1.5 g, 8.7 mmol) under a nitrogen atmosphere. Place the round-bottom flask in a preheated oil bath at 110 °C and reflux for 12 hours. After several minutes of reaction, a white solid precipitates. After the reaction is completed and cooled to room temperature, filter the solid and wash it three times with ethyl acetate. Dry it in a vacuum oven at 30 °C to obtain a white solid powder (3.05 g, yield: 95.6%).

[0055] 1 1H NMR (400 MHz, DMSO- d6 ) δ 11.13 (–OH, 1H), 10.16 (–CHO, 1H), 7.93–6.96 (Ar–H, 17H), 6.87 (–CH=, 1H), 6.14–5.56 (=CH2, 2H), 5.11 (–CH2–, 2H). (4) Preparation of homopolymer of methyl salicylaldehyde-4-vinyl diphenylphosphonium salt (PPh2PSt-5-CS)

[0056] Dissolve Ph2PSt-5-CS (2 g, 4.4 mmol) and AIBN (7 mg, 0.044 mmol) in chloroform in a 50 mL round-bottom flask, and react at 65 °C under a N2 atmosphere for 48 h. Then cool the solution to room temperature. Obtain a yellow solid (PPh2PSt-5-CS) by precipitation and wash it several times with chloroform. Dry the final product in vacuo at 50 °C overnight (1.93 g, yield: 96.5%).

[0057] (5) Synthesis of PPh2PSt-Salen:

[0058] PPh2PSt-5-CS was swollen in an appropriate amount of methanol solution, transferred to a two-necked round-bottom flask, evacuated and filled with N2. Under a N2 atmosphere, a methanol solution of ethylenediamine (36 mg, 0.6 mmol) was slowly added dropwise, and the reaction was carried out at 65 °C for 12 h. After cooling, the solid was filtered and washed three times with CH2Cl2. Finally, it was dried under vacuum at 30 °C overnight to obtain the target product as a light yellow solid (0.5568 g, yield: 99.29%).

[0059] (6) Synthesis of metal Salen / phosphonium salt polyionic liquid (PPh2PSt-Salen-Al):

[0060] PPh2PSt-Salen (0.5568 g) was dispersed in a 50 mL round-bottom flask containing MeOH / CH2Cl2 (5 mL, v:v = 9:1). Evacuated and filled with N2, a mixed solution of AlCl3 (0.15 g, 1.3 mmol) in MeOH / CH2Cl2 (5 mL, v:v = 9:1) was added to the round-bottom flask under a N2 atmosphere, and stirred at 45 °C for 12 hours. After the mixture was cooled to room temperature, the solid was filtered, washed with CH2Cl2, and dried under vacuum. The obtained product was a white solid (0.59 g, yield: 92.3%).

[0061] The above process can be represented by the following reaction formula:

[0062]

[0063] The products in the above reaction were tested, and the results are as follows:

[0064] 1) Solid-state nuclear magnetic carbon spectrum and phosphorus spectrum analysis ( 13 C, 31 P NMR)

[0065] Combined with Figure 1 、 Figure 2 It can be seen that in the solid-state 13 C, 31 P NMR spectra of PPh2PSt-Salen-Al, the presence of characteristic functional group vibration peaks can be clearly observed, confirming the successful preparation of the catalyst PPh2PSt-Salen-Al.

[0066] 2) Scanning electron microscope analysis (SEM)

[0067] The morphologies of PPh2PSt-5-CS and PPh2PSt-Salen-Al catalysts were observed through scanning electron microscope images, as Figure 3 shown. The structure of PPh2PSt-5-CS was in the form of massive particles ( Figure 3(a) figure); After introducing the metal ligand, the structure of the PPh2PST-Salen-Al catalyst is in the form of rod-shaped particles of irregular sizes ( Figure 3 (b) figure in the middle), and the sizes of these particles are between 0.6 and 2.4 nm. In addition, SEM-EDX spectrum analysis shows that the elements C, P, N, O, Cl, and Al are well distributed in the PPh2PSt-Salen-Al catalyst. These results indicate that the functional metal Salen ligand has been successfully introduced into the PPh2PSt-5-CS polymer to form a metal ligand / phosphonium salt bifunctional catalyst.

[0068] 3) CO2 adsorption curve and isosteric heat of adsorption

[0069] The adsorption curve and isosteric heat of adsorption curve of the obtained heterogeneous catalyst PPh2PSt-Salen-Al were obtained, and the results show that: the prepared heterogeneous catalyst has good adsorption performance for CO2: Combining Figure 4 , under the conditions of 273 K and 1 atm, the CO2 absorption amount of PPh2PSt-Salen-Al is 10.17 cm 3 / g. Combining Figure 5 , at low CO2 coverage, the Q st of PPh2PSt-Salen-Al is 30.38 kJ·mol -1 , indicating that there is a strong interaction between CO2 molecules and the PPh2PSt-Salen-Al catalyst.

[0070] 4) NH3 / CO2-temperature programmed desorption analysis (NH3 / CO2-TPD)

[0071] The NH3 / CO2-temperature programmed adsorption curve of the obtained heterogeneous catalyst PPh2PSt-Salen-Al was obtained, as shown in Figure 6 , Figure 6 The absorption peaks in it indicate that there are weak and medium-strength acid and base sites in the heterogeneous catalyst PPh2PSt-Salen-Al prepared in this case.

[0072] Example 2

[0073] In this example, the heterogeneous catalyst prepared in Example 1 was used for the cycloaddition reaction, and the process is as follows:

[0074] Under solvent-free conditions, 20.9 mg of the heterogeneous catalyst PPh2PSt-Salen-Al prepared in Example 1 was added to a 25 ml Schlenk tube equipped with a magnetic stir bar. Then, 10 mmol of ECH was measured and added to the Schlenk tube. The reaction was carried out at 70 °C under 0.1 MPa CO2 for 24 h. After the reaction was completed, the catalyst was separated by filtration, washed with dichloromethane, and dried under vacuum at 60 °C, and then the next catalytic cycle could be continued.

[0075] Replacement Example 1

[0076] This example was set the same as Example 2, except that the catalysts used were PPh2PSt-5-CS, PPh2PSt-Salen, Salen-Al, PPh2PSt-5-CS / Salen-Al, PPh2PSt-Salen-Co, and PPh2PSt-Salen-Zn respectively, and the group without adding a catalyst was used as the blank group.

[0077] By 1 1H NMR was used to determine the reaction selectivity and conversion rate of the substrate, and the results are shown in Table 3.

[0078] Table 3: Effects of different catalysts on the cycloaddition reaction of CO2 and ECH

[0079] Serial number Catalyst Conversion rate, % Selectivity, % 1 Blank group Trace - 2 <![CDATA[PPh2PSt-5-CS]]> 37.11 >99 3 <![CDATA[PPh2PSt-Salen]]> 48.19 >99 4 Salen-Al 24.81 >99 5 <![CDATA[PPh2PSt-5-CS / Salen-Al]]> 63.90 >99 6 <![CDATA[PPh2PSt-Salen-Al]]> 77.64 >99 7 <![CDATA[PPh2PSt-Salen-Co]]> 40.12 >99 8 <![CDATA[PPh2PSt-Salen-Zn]]> 12.28 >99 。

[0080] Compared with the heterogeneous catalyst PPh2PSt-Salen-Al prepared in Example 2, the highest conversion rate of ECH by PPh2PSt-5-CS, PPh2PSt-Salen, and Salen-Al was less than 50% (Serial Nos. 1-4); after physically mixing PPh2PSt-5-CS and Salen-Al, the conversion rate of ECH reached 63.90% (Serial No. 5), which proved that the synergistic effect of the dual active centers of the metal center and the nucleophile was beneficial to the catalytic cycloaddition reaction of CO2 and epoxides. However, small molecule Salen has homogeneous behavior and is difficult to separate. While the heterogeneous catalyst incorporating poly(ionic liquid) and metal Salen into the same polymer backbone had a conversion rate of ECH of 77.64% under the same reaction conditions (Serial No. 6, i.e., Example 2). This was mainly attributed to the intramolecular synergistic effect of the metal Lewis acidic center and the halogen anions. Metal Salen / phosphonium salt catalysts with different metal coordinations also showed different catalytic activities (Serial Nos. 6-8, Table 3). The stronger the Lewis acidity of the metal, the stronger the catalytic activity. 3.7 Investigation of the substrate applicability of the metal Salen / phosphonium salt cross-linked poly(ionic liquid) bifunctional catalyst

[0081] Example 3

[0082] This example has the same configuration as Example 2, except that: PPh2PSt-Salen-Al: 42 mg, epoxide: 10 mmol, 1 atm CO2, and the results are as follows:

[0083]

[0084] It can be seen from the above reaction formula that most of the epoxides (1a-1e) substituted with different functional groups can be effectively converted into the corresponding cyclic carbonates (2a-2e) with considerable conversion and high selectivity. The selectivity of all cyclic carbonate products remains almost constant (>99%), and almost no by-products are observed in this reaction.

Claims

1. A multiphase catalyst, characterized in that, Its structural formula is expressed as: , where M is Al and X is Cl.

2. The preparation method of the multiphase catalyst according to claim 1, characterized in that It includes the following steps: (1) Preparation of methyl salicylaldehyde-4-vinyl diphenylphosphonium salt: Dissolve 4-(diphenylphosphino)styrene and 2,6-di-tert-butyl-4-methylphenol in toluene, add a toluene solution of 5-chloromethyl salicylaldehyde under a nitrogen atmosphere, heat under reflux in an oil bath, and after the reaction is completed and cooled to room temperature, filter and wash to obtain methyl salicylaldehyde-4-vinyl diphenylphosphonium salt; (2) Preparation of poly(methyl salicylaldehyde-4-vinyl diphenylphosphonium salt): Dissolve methyl salicylaldehyde-4-vinyl diphenylphosphonium salt and azobisisobutyronitrile in chloroform, and react at 65 °C under a N2 atmosphere, then cool to room temperature and precipitate to obtain poly(methyl salicylaldehyde-4-vinyl diphenylphosphonium salt); (3) Synthesis of metal Salen / quaternary phosphonium salt polyionic liquid: After swelling the poly(methyl salicylaldehyde-4-vinyl diphenylphosphonium salt), dropwise add a methanol solution of ethylenediamine under a N2 atmosphere, and react at 65 °C overnight, then cool down, filter and wash. Disperse the obtained solid in MeOH / CH2Cl2, add an AlCl3 solution under a N2 atmosphere, stir at 45 °C for 12 hours, and after the mixture is cooled to room temperature, filter, wash and dry under vacuum to obtain a heterogeneous catalyst.

3. The preparation method of a multiphase catalyst according to claim 2, characterized in that, In step (1), the preparation method of 4-(diphenylphosphino)styrene is as follows: Using magnesium powder as a catalyst, add anhydrous THF under a N2 atmosphere, place it in an ice-water bath and stir, then dropwise add 4-bromostyrene and diphenylphosphine chloride respectively. After removing the ice-water bath, transfer it to room temperature and stir overnight; then add an ice-water bath again and quench with a saturated NH4Cl aqueous solution. Extract the mixture with ether, filter and concentrate the organic layer, and purify the residue by silica gel chromatography to obtain 4-(diphenylphosphino)styrene.

4. The preparation method of a multiphase catalyst according to claim 3, characterized in that, The addition method of the 4-bromostyrene and diphenylphosphine chloride is as follows: First, slowly dropwise add 4-bromostyrene completely under the condition of an ice-water bath, then remove the ice-water bath and transfer it to room temperature and stir for 2 hours; then, under the condition of an ice-water bath, slowly dropwise add diphenylphosphine chloride completely and then transfer it to room temperature.

5. The preparation method of a multiphase catalyst according to claim 3, characterized in that: In the silica gel chromatography purification, the volume ratio of PE to DCM is 10:

1.

6. The preparation method of a multiphase catalyst according to claim 2, characterized in that, In step (1), the preparation method of 5-chloromethyl salicylaldehyde is as follows: At room temperature, add paraformaldehyde and salicylaldehyde to concentrated hydrochloric acid with stirring, then dropwise add phosphorus oxychloride within 1 h, continuously stir and react for 28 h. After the reaction is completed, perform suction filtration to obtain the crude product. Wash the filter cake with an appropriate amount of deionized water, then wash it with a 3% (mass fraction) NaHCO3 aqueous solution, and finally wash it with deionized water until neutral. Dry it under vacuum at 60 °C overnight, and then recrystallize it with petroleum ether, filter, wash and dry to obtain 5-chloromethyl salicylaldehyde.

7. Use of the multiphase catalyst according to claim 1 in the synthesis of epoxides, characterized in that: The heterogeneous catalyst is used for the cycloaddition reaction of an epoxy substrate and carbon dioxide to obtain a cyclic carbonate.

8. Use of the multiphase catalyst according to claim 7 in the synthesis of epoxides, characterized in that: Add 20 - 42 g of the heterogeneous catalyst per 10 mol of epoxide.

9. Use of the multiphase catalyst according to claim 7 in the synthesis of epoxides, characterized in that: The reaction temperature is 70 °C and the CO2 pressure is 0.1 - 1 MPa.

10. Use of the multiphase catalyst according to claim 7 in the synthesis of epoxides, characterized in that, The structural formula of the epoxy substrate is: any one of

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