Preparation and application of imine covalent organic framework material containing imidazolyl ionic liquid

Abstract

The invention discloses preparation and application of an imido covalent organic framework material containing imidazolyl ionic liquid. The imido covalent organic framework material (ILs-TPN-COFs) containing the imidazolyl ionic liquid is obtained by connecting the imidazolyl ionic liquid [CnCmILs (at) Br] to an imido covalent organic framework TPN-COFs through a covalent bond. The material has an ionic liquid tertiary amine N active site and a halogen anion active site, and can promote CO2 activation and ring opening of epoxide. The ILs-TPN-COFs catalytic material has the advantages of uniform distribution of active sites, better stability, easiness in separation of the catalyst from a reaction system, better repeatability and the like. According to the invention, the prepared novel ILs-TPN-COFs material is applied to catalysis of synthesis of propylene carbonate from carbon dioxide and epoxypropane, and shows excellent catalytic performance under mild reaction conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of synthesis of covalent organic frameworks containing ionic liquids, and in particular relates to a preparation method of an imine covalent organic framework material containing imidazolyl ionic liquids and an application thereof in catalytic conversion of carbon dioxide. Background Art

[0002] CO 2 As a C1 resource, it has the advantages of being renewable, low-cost and non-toxic. Converting it into high-value-added chemicals, energy products and materials is one of the effective ways to solve energy and environmental problems and is of great significance to sustainable development. 2 The production of cyclic carbonates by cycloaddition reaction with epoxides is considered to be an efficient way to utilize CO 2 The process has a high atomic utilization rate and meets the requirements of green chemistry. Propylene carbonate is a widely used cyclic carbonate. Electrolytes based on propylene carbonate have the advantages of wide operating temperature, high oxidation stability, high energy density, long service life, and good low and high temperature performance, making them potential candidates for lithium-ion batteries. In addition, cyclic carbonates are widely used as polar aprotic solvents and intermediates in the production of pharmaceuticals and fine chemicals. 2 There are several routes for synthesizing cyclic carbonates as raw materials: propylene glycol-phosgene method, propylene glycol-CO 2 Method, propylene oxide-CO 2 Cycloaddition. 2 The cycloaddition method is an addition reaction, and the atom economy of the process can theoretically reach 100%, which is more in line with the requirements of green chemistry.

[0003] Due to CO 2 The spatial configuration of is linear. When it is in the ground state, the molecular energy is very low, the chemical properties are stable, it has thermodynamic stability and kinetic inertness, and activation is very difficult. 2 Conversion usually requires high activation energy and harsh reaction conditions (high temperature and high pressure). 2 The conversion reaction can be carried out under relatively mild temperature and pressure conditions. Designing and synthesizing a new type of efficient catalyst has become a current research hotspot. Most of the catalysts that have been developed have shortcomings, for example: metal oxides often require co-catalysts and are easily decomposed when exposed to water, ionic liquid catalysts are not easy to recover, and the active centers of alkali halide catalysts are easily lost. Metal complex catalysts have high activity, stability, and high adjustability of active sites, which can give them specific functions. They have received widespread attention in recent years.

[0004] Covalent organic frameworks (COFs) are mainly composed of small organic molecule monomers connected to each other by strong covalent bonds. Different from traditional covalent interactions, the covalent organic framework (COFs) materials formed by dynamic covalent bonding can self-repair through the formation and breaking of covalent bonds, and finally form the most thermodynamically stable framework structure. This dynamic action gives COFs thermal stability, crystallinity, diversity and chemical stability. They are a class of porous polymer materials composed of porous, crystalline, covalent bonds, usually with rigid structure, excellent thermal stability (temperature up to 600 ° C), stability in water and low density. They show excellent porosity, and their specific surface area exceeds that of well-known zeolites and porous silicates. They also have the unique properties of regular crystal structure, open pores and uniform size, so they can be used as excellent catalyst carriers.

[0005] There are many types of organic monomers for synthesizing COFs. According to the type of covalent bond formed by the condensation reaction, COFs can be divided into: boric acid, triazine, imine, phenylhydrazone, keto-enamine, polyimide, phthalocyanine and porphyrin.

[0006] The present invention designs an imine-based covalent organic framework material containing an imidazolyl ionic liquid, which obtains a higher conversion rate and propylene carbonate yield under mild temperature and pressure conditions. The imidazolyl ionic liquid contains the tertiary amine N active site of the imidazole group, Br − The active site and the α-carbon atom active site of the alkyl chain have both Lewis acid and Lewis base centers, which are beneficial to the subsequent CO 2 Imine COFs materials have two main functions. One is to enhance the CO 2 The adsorption capacity is enhanced by its porous, large specific surface area and nitrogen-rich characteristics. 2 The selective adsorption capacity of CO 2 The first is to enrich near the active sites of the ionic liquid; the second is to play the role of a framework for immobilizing the ionic liquid, so that the active sites of the ionic liquid are evenly distributed, so that the catalyst can be reused, and at the same time, it also provides mesopores for the exposure and mass transfer of the active sites. The advantage of the present invention designing an imine covalent organic framework material containing an imidazolyl ionic liquid as a catalyst is that the imidazolyl ionic liquid is used to functionally modify the imine covalent organic framework material, so that a homogeneous catalyst with catalytic activity is connected to the heterogeneous catalyst COFs framework to form a composite heterogeneous catalyst, which successfully makes the catalyst have both the catalytic performance of the ionic liquid and the characteristic that the heterogeneous catalyst is insoluble in the reaction system, so that the catalyst material of the present invention has the characteristics of high catalytic activity and strong reusability, so that the catalyst has a high catalytic activity for propylene oxide-CO under relatively mild conditions. 2The cycloaddition method for synthesizing propylene carbonate has a high catalytic effect and the catalyst can be recovered and reused. Summary of the invention

[0007] The main purpose of the present invention is to prepare an imine covalent organic framework material (ILs-TPN-COFs) containing imidazolyl ionic liquid and catalyze the reaction of propylene oxide-CO under relatively mild conditions. 2 Synthesis of propylene carbonate by cycloaddition method.

[0008] In order to achieve the above-mentioned purpose of the invention, the present invention adopts the following technical solutions: A method for preparing an imine-based covalent organic framework material containing an imidazolyl ionic liquid comprises the following synthesis steps: (1) Aniline compounds, phthalaldehyde compounds, pyridinedicarboxaldehyde compounds, organic solvents, and acetic acid are sequentially added to a Pyrex tube; after ultrasonication for 30 min, three freeze-pump-thaw operations are performed to achieve vacuum and oxygen-free conditions in the reaction system; the degassed Pyrex tube is naturally thawed and placed in an oven for heating to react; after the reaction is completed, the oven is closed and the tube is naturally cooled to room temperature; the crude product is washed with a solvent for multiple times until the filtrate is colorless, and the washed product is placed in an oven for drying to obtain an orange-red solid product, an imine covalent organic framework, named TPN-COFs.

[0009] (2) 1-Methylimidazole and dibromoalkane are dissolved in organic solvent C, and the mixture is added to a 100 mL round-bottom flask, heated in an oil bath, and refluxed with stirring. After the reaction is completed, the organic solvent C is removed by a rotary evaporator, and thoroughly washed with a solvent, then dissolved in ethanol, and placed in an oven for drying to obtain the desired imidazole-based ionic liquid, which is named [C n C m ILs@Br] (n = 1, m = 1, 2, 3, 4, 5; m is determined by the carbon chain length of the dibromoalkane).

[0010] (3) The imine covalent organic framework TPN-COFs and imidazolyl ionic liquid [C n C m ILs@Br], anhydrous potassium carbonate (K 2 CO 3 ) was dissolved in organic solvent D, and the mixture was added to a 100 mL three-necked round-bottom flask under N 2 The mixture was heated in an oil bath and cooled under reflux and stirred. After the reaction, the precipitate was collected and washed with a solvent for multiple times until the filtrate was colorless. The product was placed in an oven for drying to finally obtain a brown solid product containing an imide covalent organic framework material containing an imidazolyl ionic liquid, named ILs-TPN-COFs.

[0011] The aniline compound in step (1) is 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine; the phthalaldehyde compound in step (1) is 2,5-dihydroxy-1,4-phthalaldehyde; and the pyridinedicarboxaldehyde compound in step (1) is 2,2'-bipyridine-5,5'-dicarboxaldehyde.

[0012] The molar ratio of the aniline compound, the phthalaldehyde compound and the pyridinedicarboxaldehyde compound in step (1) is 1:(0.1-1):(0.1-1).

[0013] The organic solvent in step (1) is one or more of 1,4-dioxane, mesitylene, o-dichlorobenzene and n-butanol.

[0014] In step (1), the reaction temperature is 100° C.-150° C., and the reaction time is 2 days-4 days; The solvents used to wash the crude product in step (1) are tetrahydrofuran and acetone, and the washing times are 2-5 times; In step (1), the drying temperature is 70-90° C. and the drying time is 12-20 h.

[0015] The dibromoalkane in step (2) is dibromomethane (CH 2 Br 2 )、1,2-dibromoethane (C 2 H 4 Br 2 )、1,3-dibromopropane (C 3 H 6 Br 2 ) and 1,4-dibromobutane (C 4 H 8 Br 2 )、1,5-dibromopentane (C 5 H 10 Br 2 )

[0016] The molar ratio of 1-methylimidazole to dibromoalkane in step (2) is 1:(1-3).

[0017] The organic solvent C in step (2) is acetonitrile.

[0018] The reaction temperature in step (2) is 60°C-80°C, and the reaction time is 1 day-2 days.

[0019] In step (2), the washing solvent is ethyl acetate, the amount used each time is 3-5 ml, and the number of washing times is 4-7 times.

[0020] In step (3), the drying temperature is 70-90°C and the drying time is 12-20 h.

[0021] The organic solvent D in step (3) is N,N -Dimethylformamide.

[0022] The reaction temperature in step (3) is 100°C-130°C, and the reaction time is 1 day-3 days.

[0023] In step (3), the washing solvents are water and acetone, respectively, and the washing times are 4-7 times.

[0024] The drying temperature of the washed product in step (3) is 70-90°C, and the drying time is 12-20 h.

[0025] The present invention uses an imine-based covalent organic framework material (ILs-TPN-COFs) containing an imidazolyl ionic liquid as a catalyst in the reaction of carbon dioxide and propylene oxide cycloaddition to synthesize propylene carbonate. The specific operation includes: adding propylene oxide and ILs-TPN-COFs materials into a high-pressure reactor, charging 1.0-3.0 MPa of CO 2 , set the reaction temperature to 110-170 ℃, react for 5-9 hours under stirring to obtain propylene carbonate.

[0026] The beneficial effects of the present invention are: The imine covalent organic framework material TPN-COFs provided by the present invention is a solid powder with high specific surface area, large porosity, good thermal stability, CO 2 The advantages of high adsorption capacity and designable active sites are as follows. Imine COFs are formed by Schiff base polycondensation of aromatic aldehydes and aromatic amines connected by C=N covalent bonds. The nitrogen-rich properties of the Schiff base structure (-C=N-) make COFs highly resistant to CO 2 COFs with higher nitrogen content have a stronger affinity for CO 2 The stronger the selective adsorption capacity. Imidazole-based ionic liquid [CnCmILs@Br] has high catalytic activity, but is easily soluble in the reaction system, difficult to recycle, and easy to corrode equipment. In the present invention, the imidazolyl ionic liquid [CnCmILs@Br] is connected to the imine covalent organic framework material (TPN-COFs) through a covalent bond, and the prepared ILs-TPN-COFs new material is also a solid powder. Under relatively mild conditions, the material catalyzes the reaction of propylene oxide-CO 2 The cycloaddition method can achieve a good catalytic effect in the reaction system for synthesizing propylene carbonate. It also successfully solves the problems of difficulty in recycling imidazole-based ionic liquids and equipment corrosion, and has a high application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1 The figure is a flow chart for the preparation of imine-based covalent organic framework materials (ILs-TPN-COFs) containing imidazolyl ionic liquids; Figure 2 This is the XRD pattern of the imine covalent organic framework material (TPN-COFs) of Example 1; Figure 3 The infrared spectra of the imine covalent organic framework material (TPN-COFs) and the three organic monomers 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 2,5-dihydroxy-1,4-benzenedicarboxylic aldehyde, and 2,2'-bipyridine-5,5'-dicarboxaldehyde of Example 1; Figure 4 It is a comparison diagram of infrared spectra of the imine covalent organic framework material (TPN-COFs) of Example 1 and the imine covalent organic framework material (ILs-TPN-COFs) containing imidazolyl ionic liquid; Figure 5 This is the XPS graph of the imine covalent organic framework material (TPN-COFs) of Example 1; Figure 6 This is the XPS graph of the imine covalent organic framework material (ILs-TPN-COFs) containing imidazolyl ionic liquid in Example 1; Figure 7 It is an imine covalent organic framework material (ILs-TPN-COFs) structure containing imidazolyl ionic liquid. Specific implementation methods The present invention is further described by the following specific examples, but the protection scope of the present invention is not limited to the following examples.

[0028] Example 1 (1) Synthesis of imine covalent organic frameworks TPN-COFs 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine (0.08 mmol), 2,5-dihydroxy-1,4-benzenedicarboxylic acid aldehyde (0.06 mmol), 2,2'-bipyridine-5,5'-dicarboxaldehyde (0.06 mmol), mesitylene:n-butanol (volume ratio 1:1, total volume 2 ml), and acetic acid aqueous solution (6 M, 0.2 ml) were added to a Pyrex tube in sequence; after ultrasonication for 30 min, three freeze-vacuum-thaw operations were performed to achieve vacuum and oxygen-free conditions in the reaction system; the degassed Pyrex tube was naturally thawed and placed in 120 After the reaction was completed, the oven was closed and the mixture was cooled to room temperature naturally. The crude product was washed with tetrahydrofuran and acetone for several times until the filtrate was colorless. The washed product was placed in an oven and dried at 80°C for 12h to obtain an orange-red solid product named TPN-COFs.

[0029] (2) Synthesis of imidazolyl ionic liquids [C 1 C 4 ILs@Br] 1-Methylimidazole (20 mmol) and 1,4-dibromobutane (40 mmol) were dissolved in acetonitrile (20 ml), and the mixture was added to a 100 mL round-bottom flask, heated in a 70 °C oil bath for 24 h, and refluxed with stirring. After the reaction was completed, the acetonitrile was removed by a rotary evaporator and washed with ethyl acetate. After washing, it was dissolved in ethanol and placed in an oven to dry at 80 °C to obtain a light yellow viscous imidazole-based ionic liquid, named [C 1 C 4 ILs@Br].

[0030] (3) Synthesis of imine-based covalent organic frameworks containing imidazolyl ionic liquids The imine covalent organic framework (0.2 g), anhydrous potassium carbonate (1.448 mmol), and imidazole ionic liquid (6.4 mmol) were dissolved in N,N -dimethylformamide (40 ml), the mixture was added to a 100 mL three-necked round-bottom flask and heated under N 2 The mixture was heated in an oil bath at 120°C for 36 h, cooled and refluxed with stirring. After the reaction, the precipitate was collected, washed with water and acetone several times until the filtrate was colorless, and then dried in an oven at 80°C for 12 h to obtain a brown solid product named ILs-TPN-COFs.

[0031] Example 2 The preparation method of the imine-based covalent organic framework material (ILs-TPN-COFs) containing imidazolyl ionic liquid of the present invention specifically comprises the following steps: Basically the same as Example 1, except that n-butanol is replaced with o-dichlorobenzene, and the characterization results of the prepared covalent organic framework are similar to those of Example 1.

[0032] Example 3 The preparation method of the imine-based covalent organic framework material (ILs-TPN-COFs) containing imidazolyl ionic liquid of the present invention specifically comprises the following steps: Basically the same as Example 1, except that mesitylene is replaced with o-dichlorobenzene, and the characterization results of the prepared covalent organic framework are similar to those of Example 1.

[0033] Example 4 The preparation method of the imine-based covalent organic framework material (ILs-TPN-COFs) containing imidazolyl ionic liquid of the present invention specifically comprises the following steps: The method is basically the same as Example 1, except that 1,4-dibromobutane is replaced with dibromomethane. The characterization results of the prepared covalent organic framework are similar to those of Example 1.

[0034] Example 5 The preparation method of the imine-based covalent organic framework material (ILs-TPN-COFs) containing imidazolyl ionic liquid of the present invention specifically comprises the following steps: The method is basically the same as Example 1, except that 1,4-dibromobutane is replaced with 1,2-dibromoethane. The characterization results of the prepared covalent organic framework are similar to those of Example 1.

[0035] Example 6 The preparation method of the imine-based covalent organic framework material (ILs-TPN-COFs) containing imidazolyl ionic liquid of the present invention specifically comprises the following steps: The method is basically the same as Example 1, except that 1,4-dibromobutane is replaced with 1,3-dibromopropane. The characterization results of the prepared covalent organic framework are similar to those of Example 1.

[0036] Example 7 The preparation method of the imine-based covalent organic framework material (ILs-TPN-COFs) containing imidazolyl ionic liquid of the present invention specifically comprises the following steps: The method is basically the same as Example 1, except that 1,4-dibromobutane is replaced with 1,5-dibromopentane. The characterization results of the prepared covalent organic framework are similar to those of Example 1.

[0037] Figure 1 This is a flow chart for the preparation of imine-based covalent organic framework materials (ILs-TPN-COFs) containing imidazolyl ionic liquids in Example 1.

[0038] Figure 2The PXRD pattern of the imine covalent organic framework material (TPN-COFs) prepared in this Example 1 was used to characterize the crystallinity of COFs by means of a powder X-ray diffractometer (PXRD). The scanning range was set to 2θ = 1 °~ 30 °, with a step length of 0.02°, and the TPN-COFs powder was placed on a glass substrate for scanning. There are 4 obvious characteristic peaks on the curve, with the peak with the highest diffraction intensity at 2.68°, and other diffraction peaks at 4.73°, 5.40° and 7.24°. The PXRD data can preliminarily prove that COFs have been successfully synthesized and have good crystallinity.

[0039] Figure 3 This is the infrared spectrum of the imine covalent organic framework material TPN-COFs. Figure 3 It can be seen that aniline compounds have a wavelength of 3330 cm -1 and 3210 cm -1 There are absorption peaks at 1670 cm-1, which are the stretching vibration absorption peaks of NH of free amino groups; the characteristic absorption peaks of C=O double bonds of phthalaldehyde compounds and pyridinedicarboxaldehyde compounds are at 1670 cm-1, -1 and 1690cm -1 Compared with the three building blocks before the reaction, the vibration absorption peaks of the aldehyde and amino functional groups of TPN-COFs disappeared at 1580 cm -1 A new absorption peak appears at , which is the stretching vibration absorption peak of the C=N double bond generated by the reaction of aldehyde and amine. The formation of imine bond is a significant feature of Schiff base reaction, which further proves that the imine covalent organic framework has been successfully synthesized.

[0040] Figure 4 This is the infrared spectrum of the imine covalent organic framework material TPN-COFs. Figure 4 It can be seen that at 1580 cm -1 The stretching vibration absorption peak of the C=N double bond of the imine bond generated by the reaction of the amino group and the aldehyde group appeared nearby. Comparing the FT-IR images of ILs-TPN-COFs with those of TPN-COFs, the C=N stretching peak can still be observed after modification with the imidazolyl ionic liquid, which means that the covalent connectivity of ILs-TPN-COFs remains good.

[0041] Figure 5This is the XPS graph of the imine covalent organic framework material (TPN-COFs). The XPS spectrum shows that there are three elements, C, N and O, in the material. The signal peaks at 284.80 eV in the C 1s spectrum and 398.08 eV in the N 1s spectrum are related to the C atom and N atom on the imine bond, respectively; in the O 1s spectrum, the signal peak at 531.98 eV is related to the O atom on the phenol group. The appearance of the above signal peaks indicates that the synthesis of TPN-COFs is successful.

[0042] Figure 6 This is the XPS graph of the imine covalent organic framework material (ILs-TPN-COFs) containing imidazolyl ionic liquid. The XPS spectrum shows that there are four elements, C, N, O and Br, in the material. Figure 5 In comparison, in the N 1s spectrum, the signal peaks at 397.62 eV and 400.65 eV are related to the imine bond and the N atom on the imidazole group, respectively; in the Br 3d spectrum, the appearance of the signal peaks at 66.17 eV, 67.23 eV, and 69.47 eV indicates that the material contains Br − . The N atom on the imidazole group and the Br − The appearance of the signal peak confirms that the imidazolyl ionic liquid [C 1 C 4 ILs@Br] was successfully immobilized on TPN-COFs, indicating that ILs-TPN-COFs were successfully synthesized.

[0043] Application Example 1 The single imidazolyl ionic liquid [C 1 C 4 ILs@Br], imine covalent organic frameworks TPN-COFs alone, and imine covalent organic frameworks containing imidazolyl ionic liquids (ILs-TPN-COFs) were used as catalysts for the reaction of propylene oxide with CO. 2 The cycloaddition reaction is catalyzed by the following experimental procedures: Weigh 3 g of propylene oxide and 60 mg of catalyst (mass ratio is 2.0 wt%), add them into the autoclave, and fill with 2 MPa CO 2 The reaction was stirred at 160°C for 8 hours, and the filtered product was taken out for gas chromatography analysis. The yields of propylene carbonate from the three catalytic experiments are shown in the following table.

[0044] Table 1 Catalytic activity results of three catalysts for cycloaddition reaction

[0045] It can be seen from the above table that the single imidazolyl ionic liquid [C 1 C 4ILs@Br] and individual imine-based covalent organic frameworks TPN-COFs in the reaction of propylene oxide with CO 2 The yields of PC in the cycloaddition reaction were 99.20% and 4.34%, respectively. The results showed that the imidazolyl ionic liquid [C 1 C 4 [ILs@Br] has a good catalytic effect in the reaction system, but it is not easy to recover as a catalyst. When the imine covalent organic framework TPN-COFs alone is used as a catalyst, the catalytic effect is poor, but it is a solid powder catalyst that is insoluble in the reaction system and is easy to reuse. When the imine covalent organic framework material (ILs-TPN-COFs) containing imidazolyl ionic liquid of the present invention is used as a catalyst, the yield of PC is 99.01%, which also has a good catalytic effect. At the same time, it also successfully solves the problem of difficulty in recycling imidazolyl ionic liquid and equipment corrosion, and has a high application value.

[0046] Obviously, the above embodiments are merely examples for clear explanation and are not limitations on the implementation methods. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing an imine-based covalent organic framework material containing an imidazolyl ionic liquid, characterized in that: The following steps are involved: (1) Aniline compounds, phthalaldehyde compounds, pyridinedicarboxaldehyde compounds, organic solvents, and acetic acid are added to a Pyrex tube in sequence; after ultrasonic treatment for 30 min, three freeze-pump-thaw operations are performed to achieve vacuum and oxygen-free conditions in the reaction system; the degassed Pyrex tube is placed in an oven and heated for reaction; after the reaction is completed, the oven is closed and the tube is allowed to cool naturally to room temperature; the crude product is washed with a solvent for multiple times until the filtrate is colorless; the washed product is placed in an oven and dried to obtain an imine covalent organic framework; (2) dissolving 1-methylimidazole and dibromoalkane in an organic solvent, heating in an oil bath, and reflux stirring. After the reaction is completed, removing the organic solvent by a rotary evaporator, and washing thoroughly with a solvent, then dissolving with ethanol, and drying in an oven to obtain an imidazole-based ionic liquid; (3) Dissolving an imine covalent organic framework, an imidazolyl ionic liquid, and anhydrous potassium carbonate in an organic solvent, heating under reflux and stirring in a N2 environment, collecting the precipitate after the reaction is completed, washing it with a solvent for multiple times until the filtrate is colorless, and drying the product in an oven to finally obtain an imine covalent organic framework material containing an imidazolyl ionic liquid.

2. The method according to claim 1, characterized in that: The aniline compound in step (1) is 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine; the phthalaldehyde compound is 2,5-dihydroxy-1,4-phthalaldehyde; and the pyridinedicarboxaldehyde compound is 2,2'-bipyridine-5,5'-dicarboxaldehyde.

3. The method according to claim 1, characterized in that: In step (1), the molar ratio of the aniline compound, the phthalaldehyde compound and the pyridinedicarboxaldehyde compound is 1:(0.1-1):(0.1-1).

4. The method according to claim 1, characterized in that The organic solvent in step (1) is one or more of 1,4-dioxane, mesitylene, o-dichlorobenzene, and n-butanol; The reaction temperature is 100°C-150°C, and the reaction time is 2-4 days; The crude product is washed with tetrahydrofuran and acetone in sequence, and the number of washing times is 2-5 times; The drying temperature in the oven is 70-90°C and the drying time is 12-20 h.

5. The method according to claim 1, characterized in that The dibromoalkane in step (2) is one of dibromomethane, 1,2-dibromoethane, 1,3-dibromopropane, 1,4-dibromobutane and 1,5-dibromopentane.

6. The method according to claim 1, characterized in that In step (2), the molar ratio of 1-methylimidazole to dibromoalkane is 1:(1-3).

7. The method according to claim 1, characterized in that The organic solvent in step (2) is acetonitrile; The reaction temperature is 60-80°C and the reaction time is 1-2 days; The washing solvent is ethyl acetate, and the number of washings is 4-7 times; The drying temperature is 70-90°C, and the drying time is 12-20 h.

8. The method according to claim 1, characterized in that The organic solvent in step (3) is N,N - dimethylformamide; The reaction temperature is 100-130°C and the reaction time is 1-3 days; The washing solvents are water and acetone, respectively, and the washing times are 4-7 times; The drying temperature is 70-90°C, and the drying time is 12-20 h.

9. An imine-based covalent organic framework material containing an imidazolyl ionic liquid prepared by the method according to any one of claims 1 to 8.

10. Use of the imine covalent organic framework material containing imidazolyl ionic liquid as claimed in claim 9 in catalyzing the reaction of carbon dioxide and propylene oxide to synthesize propylene carbonate, characterized in that: The specific operation includes: adding propylene oxide and imine covalent organic framework materials containing imidazolyl ionic liquid into a high-pressure reactor, charging 1.0-3.0 MPa of CO2, setting the reaction temperature to 110-170°C, reacting for 5-9 hours under stirring, and obtaining propylene carbonate.

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