Catalyst for in-situ self-assembly of ionic liquid in covalent organic framework as well as preparation method and application of catalyst

Abstract

The invention relates to a catalyst for in-situ self-assembly of an ionic liquid in a covalent organic framework and a preparation method and application thereof, and is characterized in that an alkaline choline ionic liquid is encapsulated in a triazolyl covalent organic framework by using an in-situ self-assembly method, and the specific surface area of the catalyst [ChVOH] 10 (at) COF is 150-230m < 2 > / g; the [ChVOH] x (at) COF catalyst provided by the invention is simple in synthesis method, convenient to operate and mild in condition, and compared with the existing catalyst, the [ChVOH] x (at) COF catalyst does not need a co-catalyst such as TBAB, reduces the production cost, is convenient to recycle and is more beneficial to industrial production. The [ChVOH] 10 (at) COF catalyst provided by the invention is used for preparing dimethyl carbonate by one-pot step-by-step coupling of normal-pressure CO2, and has relatively high yield of cyclic allyl ester and dimethyl carbonate.

Description

Technical Field

[0001] The invention relates to an ionic liquid in-situ self-assembly in a covalent organic framework catalyst and a preparation method and application thereof, in particular to an application in catalyzing atmospheric pressure carbon dioxide one-pot step-by-step coupling to prepare dimethyl carbonate. Background Art

[0002] In order to solve the impact of greenhouse gases on the human living environment, the conversion of CO2 into valuable green chemicals has attracted much attention in recent years. In industry, CO2, as a non-toxic, abundant and low-cost C1 renewable resource, can replace toxic and harmful raw materials such as phosgene, isocyanate, carbon monoxide, and be converted into high-value-added chemicals such as methane, methanol, acetic acid, urea, organic carbonates, polycarbonates and polyurethanes. Among them, organic carbonates can be divided into cyclic carbonates and chain carbonates according to their molecular structure. Cyclic carbonates have the characteristics of high boiling point, stable structure, environmental protection and degradability, so they are widely used as chemicals such as lithium battery electrolytes, pharmaceutical intermediates and polycarbonate raw materials. Chain carbonates have better physical and chemical properties than cyclic carbonates and have a wider range of applications. For example, dimethyl carbonate (DMC) can be used in food flavoring agents, fuel additives, low-temperature electrolytes and other fields, and have great development potential from the perspective of environment and energy. However, the CO2 coupling reaction route requires the effective series connection of CO2 cycloaddition and CH3OH ester exchange reactions, which puts higher requirements on the design of the catalytic system. In order to overcome the high thermodynamic stability and kinetic inertness of CO2, harsh reaction conditions such as high temperature and high pressure are often required. To this end, the key issue is how to achieve the capture and conversion of CO2 under mild conditions. So far, many homogeneous and heterogeneous catalysts have been developed for the preparation of dimethyl carbonate from CO2, such as ionic liquids, polyionic liquids, metal halides, metal oxides, organic amine liquid bases, metal organic frameworks and covalent organic frameworks. However, most of the reported catalysts require harsh conditions with higher reaction conditions. For example, homogeneous co-catalysts such as tetrabutylammonium halide (TBAX, X = Br, Cl, I) or metal sites are added to the system to synergistically catalyze the conversion of CO2, but many additional costs are inevitably added.

[0003] Ionic liquids (ILs) are salts composed of organic cations and organic or inorganic anions. Molten salts that are in liquid state below 100°C. As "green solvents", ILs have structural designability, strong solubility properties, and good chemical and thermal stability. They have been widely used and studied in surface processing, development of microelectronic devices, processing of fine chemicals, and research on new materials. At the same time, they have shown great advantages in the reaction of CO2 to carbonate. In the reaction system, ILs are difficult to separate as homogeneous catalysts, which will lead to the decomposition of the catalyst or the formation of by-products. Therefore, in the reaction system, the easy separation of the catalyst is also an advantage that cannot be ignored. Covalent organic frameworks (COFs) have many advantages such as the designability of organic monomers, the orderliness and regularity of crystalline materials, and the diversity of covalent bond forms. In addition, compared with other porous materials, COFs have the advantages of low density, high porosity, large specific surface area, good stability, easy modification and functionalization. Most importantly, some COFs can be reused continuously and maintain good CO2 capture performance, so they are expected to be used in CO2 adsorption and conversion in practice. COFs can be used as carriers to load ILs, which can overcome the complex modification of COFs' alkaline active sites. Therefore, it is imperative for ionic liquids to effectively construct alkaline functional sites for the functional design of covalent organic framework materials and structural framework modification. Ionic liquids are used to prepare ILs-COFs composites by physical impregnation, but ionic liquids are easily dissolved from the host COF, resulting in decreased activity and poor stability of the catalyst material. In addition, ILs are organically connected before or after the synthesis of COFs, and complex synthesis steps are often required or it is difficult to prepare active groups during the preparation process. Therefore, the preparation of ILs and COFs composite catalysts is still very challenging. To this end, ILs-COFs composite catalysts are developed in a simple way, which have good catalytic activity and stability. Summary of the invention

[0004] The purpose of the present invention is to improve the problems and shortcomings of the prior art and provide a catalyst for in-situ self-assembly of an alkaline ionic liquid in a triazole covalent organic framework. Another purpose of the present invention is to provide a method for preparing the above catalyst. Another purpose of the present invention is to provide an application of the above catalyst.

[0005] The technical solution of the present invention is: a catalyst for in-situ self-assembly of an ionic liquid in a covalent organic framework [ChVOH] x @COF, characterized by encapsulating alkaline choline ionic liquid in a triazole covalent organic framework by in situ self-assembly, the catalyst [ChVOH] 10 @COF has a specific surface area of ​​150 to 230 m2 / g; among them, alkaline choline ionic liquid ([ChH + ][ - O2Mv + ][OH - ]) and the structures of the triazole-based covalent organic framework are shown in Formulas 1 and 2, respectively;

[0006]

[0007] Formula 1: Alkaline choline ionic liquid ([ChH + ][ - O2Mv + ][OH - ])Structure diagram

[0008]

[0009] Formula 2: Structural diagram of triazole covalent organic framework (TT-COF).

[0010] The present invention provides a catalyst for preparing the above-mentioned [ChVOH] x @COF's method, the specific steps are as follows:

[0011] (1) Ionic liquids [ChH + ][ - O2Mv + ][OH - Preparation of ]: Dissolve bromoacetic acid and N-vinyl imidazole in an organic solution, heat to react, cool, add alkali solution and choline chloride, react, wash, and dry to obtain [ChH + ][ - O2Mv + ][OH - ];

[0012] (2)[ChVOH] x Preparation of @COF catalyst: 1,3,5-triformylphloroglucinol, 3,5-diamino-1,2,4-triazole and [ChH + ][ - O2Mv + ][OH - ] was dissolved in the mixed solution, ultrasonicated, frozen, thawed, degassed, heated for reaction, washed, and dried to obtain [ChVOH] x @COF.

[0013] Preferably, in step (1), the mass ratio of N-vinylimidazole, bromoacetic acid, choline chloride and alkali solution is 1:(1.3-1.5):(1.3-1.5):(0.8-1.5).

[0014] Preferably, in step (1), the organic solution A is ethanol or acetonitrile; the alkali solution is KOH or NaOH; the heating reaction temperature is 70-90° C., and the heating reaction time is 20-30 h.

[0015] Preferably, in step (2), 1,3,5-triformylphloroglucinol, 3,5-diamino-1,2,4-triazole and [ChH + ][ - O2Mv + ][OH - ] is in a mass ratio of (5.5-6.5):3:(1-10); the mixed solution is a mixture of 1,4-dioxane, dimethylacetamide, acetic acid solution and mesitylene in a volume ratio of (2.5-3.2):1:(0.5-1.5):(2.5-3.5), wherein the concentration of the acetic acid solution is 3-12M; the heating reaction temperature is 110-140°C, and the heating reaction time is 2-4 days.

[0016] The catalyst [ChVOH] of the present invention x The application of @COF in the one-pot step-by-step coupling of atmospheric carbon dioxide to prepare dimethyl carbonate, the specific steps are: adding the above-prepared catalyst [ChVOH] in the reactor in sequence x @COF and propylene oxide, after using CO2 to replace the air in the kettle, pressurize and heat to the reaction temperature to start the reaction. After the reaction is completed, quickly cool and exhaust. Add methanol to the system, heat to the reaction temperature to start the reaction. After the reaction is completed, use centrifuge to separate the catalyst.

[0017] Preferably, during the CO2 addition process, the catalyst [ChVOH] x @The mass ratio of COF to propylene oxide is 1:(12-16), the reaction temperature is 80-90°C, the reaction time is 8-12h, and the carbon dioxide pressure is 0.08-0.13MPa; the mass ratio of propylene oxide to methanol is 1:(8-11); after adding methanol, the reaction temperature is 140-150°C, and the reaction time is 2-3h.

[0018] Beneficial effects:

[0019] (1) [ChVOH] provided by the present invention x @COF catalyst has the advantages of simple synthesis, convenient operation, mild conditions, etc. The in situ self-assembly method is used to prepare [ChVOH] with rich basic sites. x @COF porous nanowire materials, [ChVOH] x @COF has a specific surface area of ​​150 to 230 m 2 / g, rich pore structure, and the catalyst can be recycled 3 to 7 times.

[0020] (2) [ChVOH] provided by the present invention x @COF catalyst is a heterogeneous composite catalyst of covalent organic framework material modified by ionic liquid. Compared with existing catalysts, it does not require a co-catalyst such as TBAB, reduces production costs, is easy to recycle, and is more conducive to industrial production.

[0021] (3) [ChVOH] provided by the present invention 10 @COF catalyst is used for one-pot step-by-step coupling of atmospheric CO2 to prepare dimethyl carbonate, with a high cyclic propylene ester yield of 43.1% and a dimethyl carbonate yield of 56.7%, which are better than the reaction conditions reported in the existing literature. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 [ChVOH] prepared in Example 1 10 FT-IR graphs of TT-COF prepared in @COF and comparative example 1 and the corresponding monomers.

[0023] Figure 2 [ChVOH] prepared in Example 1 10 @SEM image of COF.

[0024] Figure 3 [ChVOH] prepared in Example 1 10 @Chart of N2 adsorption-desorption of COF.

[0025] Figure 4 [ChVOH] prepared in Example 1 10 @COF thermogravimetric diagram.

[0026] Figure 5 [ChVOH] prepared in Examples 1 to 5 x @Catalytic performance diagram of COF (x=10, 5, 15, 30, 50).

[0027] Figure 6 [ChVOH] prepared in Example 1 10 @COF and TT-COF prepared in Comparative Example 1,

[0028] [H + ][ - O2Mv + ][OH - ] and [ChH + ][ - O2Mv + ][OH - ]+TT-COF catalytic performance diagram. DETAILED DESCRIPTION

[0029] The present invention is described in more detail below using comparative examples and examples. These comparative examples and examples are only descriptions of the best comparison and implementation methods of the present invention, and do not limit the scope of protection of the present invention in any way.

[0030] Example 1

[0031] Step 1: In a flask, dissolve 283 mg of N-vinyl imidazole in 10 mL of ethanol, add 420 mg of bromoacetic acid, and react at 80 °C for 24 h under N2 protection. Cool, add 400 mg of KOH aqueous solution, add 420 mg of choline chloride, and react at room temperature. Wash with ethyl acetate several times, and vacuum dry at 60 °C for 24 h to obtain the ionic liquid [ChH + ][ - O2Mv + ][OH - ].

[0032] Step 2: In a Pyrex tube, 30 mg of 1,3,5-triformylphloroglucinol, 15 mg of 3,5-diamino-1,2,4-triazole and 10 mg of [ChH + ][ - O2Mv + ][OH - ] was dissolved in a mixed solvent (2.66 mL, 1,4-dioxane / dimethylacetamide / 6M acetic acid / mesitylene = 3 / 1 / 1 / 3, volume ratio), ultrasonicated for 30 min, frozen, thawed, and degassed at 77 K for three cycles, and then sealed at 120 ° C for 4 days. After the reaction was completed and cooled to room temperature, it was washed with DMF, methanol, and acetone in turn, and then vacuum dried at 80 ° C overnight to obtain [ChVOH] 10 @COF.

[0033] [ChVOH] 10 @ FT-IR characterization of COF catalyst Figure 1 As shown in the FT-IR graph, it can be seen that the contraction vibrations of C=C, C=N, and CN are at 1598 cm -1 、1400cm -1 、1241cm -1 appears, indicating successful synthesis. + ][ - O2Mv + ][OH - The incorporation of ] does not cause structural changes in COF. Catalyst [ChVOH] 10 @COF SEM characterization Figure 2 As shown, it can be seen from SEM that the prepared [ChVOH] 10The morphology of the @COF catalyst is a uniform nanowire structure. From the N2 adsorption-desorption experiment, Figure 3 As shown, [ChVOH] 10 @COF specific surface area is 170.2614m 2 / g, [ChVOH] 10 @COF catalyst has a type II isotherm curve. Under higher pressure, the adsorption amount of nitrogen increases significantly, and it is a typical mesoporous material. Figure 4 The thermogravimetric analysis curve shows that [ChVOH] 10 @COF thermal stability. The mass reduction between the initial temperature and 150°C is due to the removal of water and organic solvents by volatilization. The mass reduction in the range of 170-270°C is attributed to [ChH + ][ - O2Mv + ][OH - ] decomposition. At 310℃, [ChVOH] 10 @COF is just beginning to collapse and decompose.

[0034] Weigh 580 mg of propylene oxide, 45 mg of [ChVOH] 10 @COF catalyst, add it to the autoclave, replace the air in the autoclave with carbon dioxide 3 times, fill the autoclave with carbon dioxide until the pressure is 0.1MPa, adjust the stirring speed to 300r / min, raise the temperature to 80℃, start the reaction, react for 10h, cool it quickly after the reaction, add 4.8g methanol to the system, raise the temperature to 140℃, react for 2h, separate the catalyst by centrifugation after the reaction. Gas chromatography analysis of the liquid obtained by the reaction shows that the yield of cyclic propylene ester is 43.1%, the selectivity of cyclic propylene ester is 99%, the conversion rate of dimethyl carbonate is 99%, and the yield of dimethyl carbonate is 56.7%.

[0035] Comparative Example 1

[0036] Step 1: In a flask, dissolve 283 mg of N-vinyl imidazole in 10 mL of acetonitrile, add 396 mg of bromoacetic acid, and react at 80 °C for 24 h under N2 protection. Cool, add 393 mg of KOH, add 400 mg of choline chloride, and react at room temperature. Wash with ethyl acetate several times, and vacuum dry at 60 °C for 24 h to obtain the ionic liquid [ChH + ][ - O2Mv + ][OH - ].

[0037] Step 2: The preparation method of TT-COF is consistent with the published paper (XUE Q, WANG P, CHENG L, et al. Triazole-based COF tightly hugging ionic liquids through interactions of hydrogenbonds for enhanced atmospheric CO2 conversion [J]. Sep Purif Technol, 2025, 352.).

[0038] Step 3: Mix 30 mg of TT-COF and 10 mg of [ChH + ][ - O2Mv + ][OH - ] and grind together until completely uniform to obtain physically mixed TT-COF+IL.

[0039] FT-IR characterization of TT-COF catalyst Figure 1 As shown in the FT-IR graph of TT-COF, it can be seen that the characteristic peaks of the monomers required for the synthesis of TT-COF disappear, and the contraction vibrations of the synthesized C=C, C=N, and CN are at 1598 cm -1 、1400cm -1 and 1241cm -1 appeared, revealing the successful synthesis of COF.

[0040] [ChVOH] x @COF is a catalyst that catalyzes the one-pot step-by-step coupling of carbon dioxide at atmospheric pressure to prepare dimethyl carbonate.

[0041] Weigh 567 mg propylene oxide and 43 mg catalyst (test [ChH + ][ - O2Mv + ][OH - ], TT-COF and TT-COF+IL), added to the autoclave, carbon dioxide replaced the air in the autoclave 3 times, filled the autoclave with carbon dioxide until the pressure was 0.12MPa, adjusted the stirring speed to 300r / min, raised the temperature to 81°C, started the reaction, reacted for 11h, cooled rapidly after the reaction, added 4.85g methanol to the system, raised the temperature to 142°C, reacted for 2.2h, and separated the catalyst by centrifugation after the reaction. The liquid obtained by the reaction was analyzed by gas chromatography, [ChH + ][ - O2Mv + ][OH -]Catalytic results: the yield of cyclic propylene ester is 61.6%, the selectivity of cyclic propylene ester is 99%, the conversion rate of dimethyl carbonate is 99%, and the yield of dimethyl carbonate is 37.9%; TT-COF catalytic results: the yield of cyclic propylene ester is 58.9%, the selectivity of cyclic propylene ester is 99%, the conversion rate of dimethyl carbonate is 30.4%, and the yield of dimethyl carbonate is trace; TT-COF+IL catalytic results: the yield of cyclic propylene ester is 64.2%, the selectivity of cyclic propylene ester is 99%, the conversion rate of dimethyl carbonate is 99%, and the yield of dimethyl carbonate is 34.9%.

[0042] [ChVOH] prepared in Example 1 10 @COF and TT-COF prepared in Comparative Example 1, [ChH + ][ - O2Mv + ][OH - ] and [ChH + ][ - O2Mv + ][OH - The catalytic performance of ]+TT-COF is shown in the figure Figure 6 shown.

[0043] Example 2

[0044] Step 1: In a flask, dissolve 280 mg of N-vinyl imidazole in 10 mL of acetonitrile, add 410 mg of bromoacetic acid, and react at 70 °C for 24 h under N2 protection. Cool, add 420 mg of KOH, add 405 mg of choline chloride, and react at room temperature for 12 h. Wash with ethyl acetate several times, and vacuum dry at 60 °C for 24 h to obtain the ionic liquid [ChH + ][ - O2Mv + ][OH - ].

[0045] Step 2: In a Pyrex tube, 32 mg of 1,3,5-triformylphloroglucinol, 15 mg of 3,5-diamino-1,2,4-triazole, and 5 mg of [ChH + ][ - O2Mv + ][OH -] was dissolved in a mixed solvent (2.66 mL, 1,4-dioxane / dimethylacetamide / 12 M acetic acid / mesitylene = 3.2 / 1 / 0.6 / 3.2, volume ratio), ultrasonicated for 30 min, frozen, thawed, and degassed at 77 K for three cycles, and then sealed at 130 ° C for 4 days. After the reaction was completed and cooled to room temperature, it was washed with DMF, methanol, and acetone in sequence, and then vacuum dried at 80 ° C overnight to obtain [ChVOH]5@COF.

[0046] [ChVOH] x @COF is a catalyst that catalyzes the one-pot step-by-step coupling of atmospheric pressure carbon dioxide to prepare dimethyl carbonate.

[0047] 580 mg of propylene oxide and 45 mg of [ChVOH]5@COF catalyst were weighed in sequence and added to a high-pressure reactor. The air in the reactor was replaced by carbon dioxide three times. Carbon dioxide was charged into the reactor until the pressure was 0.13 MPa. The stirring speed was adjusted to 300 r / min, and the temperature was raised to 80°C. The reaction was started and the reaction lasted for 10 hours. After the reaction was completed, the system was cooled rapidly, 4.81 g of methanol was added to the system, the temperature was raised to 145°C, and the reaction lasted for 2.1 hours. After the reaction was completed, the catalyst was separated by centrifugation. The liquid obtained by the reaction was analyzed by gas chromatography. The yield of cyclic propylene ester was 61.1%, the selectivity of cyclic propylene ester was 99%, the conversion rate of dimethyl carbonate was 99%, and the yield of dimethyl carbonate was 39.7%.

[0048] Example 3

[0049] Step 1: In a flask, dissolve 290 mg of N-vinyl imidazole in 10 mL of ethanol, add 380 mg of bromoacetic acid, and react at 75 °C for 30 h under N2 protection. Cool, add 435 mg of NaOH, add 406 mg of choline chloride, and react at room temperature. Wash with ethyl acetate several times, and vacuum dry at 60 °C for 24 h to obtain the ionic liquid [ChH + ][ - O2Mv + ][OH - ].

[0050] Step 2: In a Pyrex tube, 33 mg of 1,3,5-triformylphloroglucinol, 17 mg of 3,5-diamino-1,2,4-triazole, and 15 mg of [ChH + ][ - O2Mv + ][OH -] was dissolved in a mixed solvent (2.0 mL, 1,4-dioxane / dimethylacetamide / 6M acetic acid / mesitylene = 2.5 / 1 / 1 / 2.5, volume ratio), ultrasonicated for 30 min, frozen, thawed, and degassed at 77 K for three cycles, and then sealed at 120 ° C for 3 days. After the reaction was completed and cooled to room temperature, it was washed with DMF, methanol, and acetone in turn, and then vacuum dried at 80 ° C overnight to obtain [ChVOH] 15 @COF.

[0051] [ChVOH] x @COF is a catalyst that catalyzes the one-pot step-by-step coupling of carbon dioxide at atmospheric pressure to prepare dimethyl carbonate.

[0052] Weigh 581 mg of propylene oxide, 40 mg of [ChVOH] 15 @COF catalyst, add it to the autoclave, replace the air in the autoclave with carbon dioxide 3 times, fill the autoclave with carbon dioxide until the pressure is 0.09MPa, adjust the stirring speed to 300r / min, raise the temperature to 80℃, start the reaction, react for 12h, cool quickly after the reaction, add 4850mg methanol to the system, raise the temperature to 140℃, react for 2.5h, separate the catalyst by centrifugation after the reaction. Gas chromatography analysis of the liquid obtained by the reaction shows that the yield of cyclic propylene ester is 48.2%, the selectivity of cyclic propylene ester is 99%, the conversion rate of dimethyl carbonate is 99%, and the yield of dimethyl carbonate is 51.2%.

[0053] Example 4

[0054] Step 1: In a flask, dissolve 290 mg of N-vinyl imidazole in 10 mL of ethanol, add 435 mg of bromoacetic acid, and react at 85 °C for 30 h under N2 protection. Cool, add 310 mg of NaOH, add 435 mg of choline chloride, and react at room temperature. Wash with ethyl acetate several times, and vacuum dry at 60 °C for 24 h to obtain the ionic liquid [ChH + ][ - O2Mv + ][OH - ].

[0055] Step 2: In a Pyrex tube, 40 mg of 1,3,5-triformylphloroglucinol, 20 mg of 3,5-diamino-1,2,4-triazole and 32 mg of [ChH + ][ - O2Mv + ][OH -] was dissolved in a mixed solvent (2.83 mL, 1,4-dioxane / dimethylacetamide / 3M acetic acid / mesitylene = 3 / 1 / 1.5 / 3, volume ratio), ultrasonicated for 30 min, frozen, thawed, and degassed at 77 K for three cycles, and then sealed at 120 ° C for 4 days. After the reaction was completed and cooled to room temperature, it was washed with DMF, methanol, and acetone in turn, and then vacuum dried at 80 ° C overnight to obtain [ChVOH] 30 @COF.

[0056] [ChVOH] x @COF is a catalyst that catalyzes the one-pot step-by-step coupling of carbon dioxide at atmospheric pressure to prepare dimethyl carbonate.

[0057] Weigh 590 mg of propylene oxide, 48 mg of [ChVOH] 30 @COF catalyst was added to a high-pressure reactor, and the air in the reactor was replaced by carbon dioxide for 3 times. The reactor was filled with carbon dioxide until the pressure was 0.11MPa, and the stirring speed was adjusted to 300r / min. The temperature was raised to 80°C, and the reaction was started. The reaction lasted for 10 hours. After the reaction was completed, the system was cooled quickly, and 4.806g of methanol was added to the system. The temperature was raised to 140°C, and the reaction lasted for 2 hours. After the reaction was completed, the catalyst was separated by centrifugation. The liquid obtained by the reaction was analyzed by gas chromatography, and the yield of cyclic propylene ester was 48.6%, the selectivity of cyclic propylene ester was 99%, the conversion rate of dimethyl carbonate was 99%, and the yield of dimethyl carbonate was 51.3%.

[0058] Example 5

[0059] Step 1: In a flask, dissolve 285 mg of N-vinyl imidazole in 10 mL of acetonitrile, add 375 mg of bromoacetic acid, and react at 70 °C for 24 h under N2 protection. Cool, add 390 mg of KOH, add 380 mg of choline chloride, and react at room temperature for 12 h. Wash with ethyl acetate several times, and vacuum dry at 60 °C for 24 h to obtain the ionic liquid [ChH + ][ - O2Mv + ][OH - ].

[0060] Step 2: In a Pyrex tube, 32 mg of 1,3,5-triformylphloroglucinol, 15 mg of 3,5-diamino-1,2,4-triazole, and 50 mg of [ChH + ][ - O2Mv + ][OH -] was dissolved in a mixed solvent (2.66 mL, 1,4-dioxane / dimethylacetamide / 6M acetic acid / mesitylene = 3 / 1 / 1 / 3, volume ratio), ultrasonicated for 30 min, frozen, thawed, and degassed at 77 K for three cycles, and then sealed at 120 ° C for 3 days. After the reaction was completed and cooled to room temperature, it was washed with DMF, methanol, and acetone in turn, and then vacuum dried at 80 ° C overnight to obtain [ChVOH] 50 @COF.

[0061] [ChVOH] x @COF is a catalyst that catalyzes the one-pot step-by-step coupling of carbon dioxide at atmospheric pressure to prepare dimethyl carbonate.

[0062] Weigh 575 mg of propylene oxide, 45 mg of [ChVOH] 50 @COF catalyst, add it to the autoclave, replace the air in the autoclave with carbon dioxide 3 times, fill the autoclave with carbon dioxide until the pressure is 0.12MPa, adjust the stirring speed to 300r / min, raise the temperature to 85℃, start the reaction, react for 10h, cool it quickly after the reaction, add 5.75g methanol to the system, raise the temperature to 150℃, react for 2h, separate the catalyst by centrifugation after the reaction. Gas chromatography analysis of the liquid obtained by the reaction shows that the yield of cyclic propylene ester is 46.9%, the selectivity of cyclic propylene ester is 99%, the conversion rate of dimethyl carbonate is 99%, and the yield of dimethyl carbonate is 52.8%.

[0063] [ChVOH] prepared in Examples 1 to 5 above x The catalytic performance of @COF (x = 10, 5, 15, 30, 50) is shown in the figure Figure 5 shown.

[0064] The experimental results of the application example are shown in Table 1.

[0065] Table 1. Application example experimental results

[0066]

[0067]

Claims

1. An ionic liquid in situ self-assembly catalyst on a covalent organic framework [ChVOH] x @COF, characterized by The alkaline choline ionic liquid was encapsulated in a triazole-based covalent organic framework by in situ self-assembly, and the catalyst [ChVOH] 10 @COF has a specific surface area of ​​150 to 230 m 2 / g; among them, alkaline choline ionic liquid ([ChH + ][ - O2Mv + ][OH - ]) and the structures of the triazole-based covalent organic framework are shown in Formulas 1 and 2, respectively; 2. A method for preparing the catalyst [ChVOH] as claimed in claim 1 x @COF's method, the specific steps are as follows: (1) Ionic liquids [ChH + ][ - O2Mv + ][OH - Preparation of ]: Dissolve bromoacetic acid and N-vinyl imidazole in an organic solution, heat to react, cool, add alkali solution and choline chloride, react, wash, and dry to obtain [ChH + ][ - O2Mv + ][OH - ]; (2)[ChVOH] x Preparation of @COF catalyst: 1,3,5-triformylphloroglucinol, 3,5-diamino-1,2,4-triazole and [ChH + ][ - O2Mv + ][OH - ] was dissolved in the mixed solution, ultrasonicated, frozen, thawed, degassed, heated for reaction, washed, and dried to obtain [ChVOH] x @COF.

3. The method according to claim 2, characterized in that In step (1), the mass ratio of N-vinylimidazole, bromoacetic acid, choline chloride and alkali solution is 1:(1.3-1.5):(1.3-1.5):(0.8-1.5).

4. The method according to claim 2, characterized in that: In step (1), the organic solution A is ethanol or acetonitrile; the alkali solution is KOH or NaOH; the heating reaction temperature is 70-90° C., and the heating reaction time is 20-30 hours.

5. The method according to claim 2, characterized in that In step (2), 1,3,5-triformylphloroglucinol, 3,5-diamino-1,2,4-triazole and [ChH + ][ - O2Mv + ][OH - ] is in a mass ratio of (5.5-6.5):3:(1-10); the mixed solution is a mixture of 1,4-dioxane, dimethylacetamide, acetic acid solution and mesitylene in a volume ratio of (2.5-3.2):1:(0.5-1.5):(2.5-3.5), wherein the concentration of the acetic acid solution is 3-12M; the heating reaction temperature is 110-140°C, and the heating reaction time is 2-4 days.

6. The catalyst according to claim 1 [ChVOH] x Application of @COF in the one-pot step-by-step coupling of atmospheric pressure carbon dioxide to prepare dimethyl carbonate.

7. The use according to claim 6, wherein the specific steps are: adding the above-prepared catalyst [ChVOH] x @COF and propylene oxide, after using CO2 to replace the air in the kettle, pressurize and heat to the reaction temperature to start the reaction. After the reaction is completed, quickly cool and exhaust. Add methanol to the system, heat to the reaction temperature to start the reaction. After the reaction is completed, use centrifuge to separate the catalyst.

8. The use according to claim 7, characterized in that: During the addition of CO2, the catalyst [ChVOH] x @The mass ratio of COF to propylene oxide is 1:(12-16), the reaction temperature is 80-90°C, the reaction time is 8-12h, and the carbon dioxide pressure is 0.08-0.13MPa; the mass ratio of propylene oxide to methanol is 1:(8-11); after adding methanol, the reaction temperature is 140-150°C, and the reaction time is 2-3h.

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