Alkaline ionic covalent organic framework material and preparation method and application thereof

Abstract

The application discloses an alkali ion type covalent organic framework material and a preparation method and application thereof, wherein 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 1,4-diisocyanobenzene and 2-aminopyridine are used as building units, a covalent organic framework containing pyrimidine is obtained through a condensation reaction, and then a quaternary ammonium reaction and an ion exchange reaction are sequentially performed to obtain the alkali ion type covalent organic framework.The alkali ion type covalent organic framework material prepared by the application has rich alkali sites, developed pore structures and good chemical stability, exhibits good catalytic performance as a catalyst for one-pot preparation of dimethyl carbonate from CO2, an epoxide compound and methanol, and also shows good cycle stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional materials, in particular to a preparation method of an alkali ion type covalent organic framework material and application thereof. BACKGROUND

[0002] The high consumption of fossil energy has led to a continuous increase in atmospheric CO2, resulting in global warming and environmental problems. How to effectively reduce CO2 emissions has become a global challenge. Compared with CO2 capture and storage, converting it into value-added products has always been considered an effective way to reduce environmental pollution and achieve sustainable carbon utilization. In particular, the one-pot preparation of dimethyl carbonate (DMC) from CO2, epoxide and methanol can not only retain the high yield of indirect synthesis of CO2, but also omit the separation operation of the intermediate product cyclic carbonate, and has more advantages in CO2 activation and DMC synthesis compared with other processes. However, the existing catalysts for the one-pot preparation of dimethyl carbonate (DMC) from CO2, epoxide and methanol have poor catalytic performance, and the conversion rate of CO2 and the yield of the product are not high.

[0003] Covalent organic frameworks (COFs) are a new type of crystalline porous material with highly ordered two-dimensional or three-dimensional network structures, which have broad application prospects in the fields of adsorption, chemical sensing, heterogeneous catalysis, proton conduction and energy storage. The most significant advantage of COFs is that the building blocks are connected to each other through reversible covalent bonds, and the structure and function can be easily customized by changing the size and type of the building blocks, engineering the pore surface, and forming specific connections. Therefore, using COFs as catalysts for the one-pot preparation of dimethyl carbonate (DMC) from CO2, epoxide and methanol is expected to improve the conversion rate of CO2 and the yield of the product. However, in order to obtain excellent crystallinity, the reaction used to prepare COFs is usually required to have high thermodynamic reversibility, which will also result in poor stability of COFs, which are easily decomposed under acidic or basic conditions and cannot be used for the one-pot preparation of dimethyl carbonate from CO2, epoxide and methanol. SUMMARY

[0004] In order to solve the technical problems of the existing ordinary catalysts for CO2 and epoxide, which have low conversion rate of CO2 and low yield of product, and the existing COFs materials, which have poor stability and cannot be used for the one-pot preparation of dimethyl carbonate from CO2, epoxide and methanol, the present application provides an alkali ion type covalent organic framework material and a preparation method thereof, as well as the application thereof in the one-pot preparation of DMC from CO2, epoxide and methanol.

[0005] The technical scheme adopted by the present application is:

[0006] An alkali ion type covalent organic framework material, which is prepared by condensation reaction of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 1,4-diisocyanatobenzene and 2-aminopyridine as building units to obtain a covalent organic framework containing pyrimidine, and then by quaternary ammonium reaction and ion exchange reaction to obtain the alkali ion type covalent organic framework, and has the following structural formula:

[0007]

[0008] X is OH - , CO3 2- , HCO3 - or CH3COO - .

[0009] The preparation method of the above alkali ion type covalent organic framework material comprises the following steps:

[0010] (1) Preparation of pyrimidine-based covalent organic framework: 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 1,4-diisocyanatobenzene and 2-aminopyridine are dissolved in a mixed solvent composed of ethanol and mesitylene to obtain solution A; p-toluenesulfonic acid is added to the obtained solution A, which is rapidly frozen in liquid nitrogen, vacuum sealed, and then placed in an oven for condensation reaction after being raised to room temperature; and the pyrimidine-based covalent organic framework is obtained after filtration, washing and vacuum drying;

[0011] (2) Preparation of brominated hydroxyethyl pyrimidine ion type covalent organic framework: the pyrimidine-based covalent organic framework prepared in step (1) is uniformly dispersed in ethanol to obtain solution B; 2-bromoethanol is added to the obtained solution B for quaternary ammonium reaction; and the brominated hydroxyethyl pyrimidine ion type covalent organic framework is obtained after filtration, washing and vacuum drying after the reaction is completed;

[0012] (3) Preparation of alkali ion type covalent organic framework: the brominated hydroxyethyl pyrimidine ion type covalent organic framework prepared in step (2) is uniformly dispersed in methanol to obtain solution C; an ion exchanger is added to the obtained solution C for ion exchange reaction to obtain the alkali ion type covalent organic framework.

[0013] Preferably, in step (1), the molar ratio of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 1,4-diisocyanatobenzene and 2-aminopyridine is 2:3-5:6-10; the molar ratio of toluenesulfonic acid to 2,4,6-tris(4-formylphenyl)-1,3,5-triazine is 2-4:5; the molar concentration of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine in the mixed solvent is 0.125-0.25 mmol / mL; and the volume ratio of ethanol to mesitylene is 1:2-5.

[0014] As preferably, in step (1), the temperature of the condensation reaction is 80-140 DEG C, and the time is 3-7 days.

[0015] As preferably, in step (2), the molar concentration of 2-bromoethanol in ethanol is 0.008-0.05 mmol / mL; and the mass concentration of the pyrimidine-based covalent organic framework in ethanol is 2-10 mg / mL.

[0016] As preferably, in step (2), the temperature of the quaternization reaction is 30-90 DEG C, and the time is 24-48 h.

[0017] As preferably, in step (3), the molar concentration of the ion exchanger in methanol is 0.01-0.06 mmol / mL; the mass concentration of the hydroxyethyl pyrimidine ionic covalent organic framework in methanol is 1.6-8 mg / mL; and the ion exchanger is sodium hydroxide, anhydrous sodium carbonate, anhydrous sodium bicarbonate or sodium acetate.

[0018] As preferably, in step (3), the temperature of the ion exchange reaction is 60-90 DEG C, and the time is 48-96 h.

[0019] The application method of the above-mentioned alkali ionic covalent organic framework material in one-pot synthesis of dimethyl carbonate from CO2, epoxide and methanol.

[0020] As preferably, the application method comprises adding the epoxide, the methanol and the alkali ionic covalent organic framework material into a high-pressure reaction kettle, wherein the molar ratio of the epoxide to the methanol is 1:5-15, the mass concentration of the alkali ionic covalent organic framework material in the epoxide is 2-5 mg / mmol, and then CO2 is introduced for the synthesis reaction, the reaction temperature is set to 100-140 DEG C, the reaction pressure is 5-15 bar, and the reaction time is 0.5-2 h.

[0021] The beneficial effects of the present application are as follows:

[0022] (1) The present application realizes the integration of functional group design and super stability in the synthesis of COFs by isonitrile chemical method. These pyrimidine-based COFs not only have super stability under alkaline conditions due to the universal existence of imidazole ring chains, but also facilitate the introduction of ionic liquids, providing more possibilities for the directional adjustment of materials. In addition, structural diversity can be further realized through pre-designed isonitrile or aldehyde monomers.

[0023] (2) The alkali ion type covalent organic framework material prepared by the method has rich alkali sites, developed pore structure and good thermal stability, exhibits good catalytic performance as a catalyst for one-pot preparation of dimethyl carbonate from CO2, epoxide and methanol, and good cycle stability, and can be recycled by simple filtration and drying, and the catalytic performance remains basically unchanged after 5 cycles. DETAILED DESCRIPTION

[0024] In order to make the object, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be clearly and completely described below in combination with a preferred embodiment.

[0025] Example 1

[0026] A hydroxide anion type covalent organic framework material (PMCOF-OH-1) has the following structural formula (X is OH - ):

[0027]

[0028] The preparation method of the above-mentioned hydroxide anion type covalent organic framework material (PMCOF-OH-1) has the following specific steps:

[0029] (1) Preparation of a pyrimidine-based covalent organic framework: 0.05 mmol of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 0.075 mmol of 1,4-diisocyanatobenzene and 0.15 mmol of 2-aminopyridine are dissolved in a mixed solvent composed of 0.4 mL of ethanol and 0.8 mL of mesitylene, 0.02 mmol of p-toluenesulfonic acid is added to the obtained solution, the solution is quickly frozen in liquid nitrogen, vacuumized and sealed, then is placed in an oven at 80℃ for 3 days after being raised to room temperature, and then is filtered, washed and vacuum dried to obtain a pyrimidine-based covalent organic framework.

[0030] (2) Introduction of an ionic liquid: 100 mg of the pyrimidine-based covalent organic framework prepared in step (1) is uniformly dispersed in 50 mL of ethanol, 0.4 mmol of 2-bromoethanol is added thereto, and quaternary ammonium reaction is carried out at 30℃ for 24 hours, and then the reaction is ended, and the product is filtered, washed and vacuum dried to obtain a hydroxyethyl pyrimidine ionic type covalent organic framework.

[0031] (3) Ion exchange: 80 mg of the hydroxyethyl pyrimidine ionic type covalent organic framework prepared in step (2) is uniformly dispersed in 50 mL of methanol, 0.5 mmol of sodium hydroxide is added thereto, and stirring is carried out at 60℃ for 48 hours, and then the product is vacuum filtered, washed and dried to obtain a hydroxide anion type covalent organic framework material, which is denoted as PMCOF-OH-1.

[0032] Example 2

[0033] A hydroxide anion-type covalent organic framework material (PMCOF-OH-2) has the following structural formula (X is OH). - ):

[0034]

[0035] The specific steps for preparing the above-mentioned hydroxide anion-type covalent organic framework material (PMCOF-OH-2) are as follows:

[0036] (1) Preparation of pyrimidinyl covalent organic framework: 0.1 mmol of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, 0.25 mmol of 1,4-diisocyanophenyl and 0.5 mmol of 2-aminopyridine were dissolved in a mixed solvent consisting of 0.2 mL of ethanol and 1.0 mL of mesitylene. 0.08 mmol of p-toluenesulfonic acid was added to the resulting solution. The solution was then rapidly frozen in liquid nitrogen, vacuumed, sealed, and heated to room temperature before being placed in an oven at 100 °C for 5 days. After the reaction was completed, the solution was filtered, washed and vacuum dried to obtain the pyrimidinyl covalent organic framework.

[0037] (2) Introduction of ionic liquid: Take 100 mg of the pyrimidine covalent organic framework prepared in step (1) and disperse it evenly in 10 mL of ethanol. Add 0.5 mmol of 2-bromoethanol to it and quaternize it at 60 °C for 48 hours. After the reaction is completed, filter, wash and vacuum dry to obtain the brominated hydroxyethylpyrimidine ionic covalent organic framework.

[0038] (3) Ion exchange: Take 80 mg of the brominated hydroxyethyl pyrimidine ionic covalent organic framework prepared in step (2) and disperse it evenly in 10 mL of methanol. Add 0.6 mmol of sodium hydroxide to it, heat to 70 °C and stir for 72 hours. After filtration, washing and drying, the hydroxide anionic covalent organic framework material is obtained, which is denoted as PMCOF-OH-2.

[0039] Example 3

[0040] A bicarbonate ionic covalent organic framework (PMCOF-HCO3-1) has the following structural formula (X is HCO3). - ):

[0041]

[0042] The specific steps for preparing the above-mentioned bicarbonate ionic covalent organic framework (PMCOF-HCO3-1) are as follows:

[0043] (1) Preparation of pyrimidinyl covalent organic framework: 0.05 mmol of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, 0.075 mmol of 1,4-diisocyanobenzene and 0.15 mmol of 2-aminopyridine were dissolved in a mixed solvent consisting of 0.4 mL of ethanol and 0.8 mL of mesitylene. 0.02 mmol of p-toluenesulfonic acid was added to the resulting solution. The solution was then rapidly frozen in liquid nitrogen, vacuumed, sealed, and heated to room temperature before being placed in an oven at 120 °C for 6 days. After the reaction was completed, the solution was filtered, washed and vacuum dried to obtain the pyrimidinyl covalent organic framework.

[0044] (2) Introduction of ionic liquid: Take 100 mg of the pyrimidine covalent organic framework prepared in step (1) and disperse it evenly in 50 mL of ethanol. Add 0.4 mmol of 2-bromoethanol to it and quaternize it at 80 °C for 24 hours. After the reaction is completed, filter, wash and vacuum dry to obtain the brominated hydroxyethylpyrimidine ionic covalent organic framework.

[0045] (3) Ion exchange: Take 80 mg of the brominated hydroxyethyl pyrimidine ionic covalent organic framework prepared in step (2) and disperse it evenly in 10 mL of methanol. Add 0.5 mmol of anhydrous sodium bicarbonate to it, heat to 80 °C and stir for 96 hours. After filtration, washing and drying, the bicarbonate ionic covalent organic framework is obtained and is denoted as PMCOF-HCO3-1.

[0046] Example 4

[0047] A bicarbonate ionic covalent organic framework (PMCOF-HCO3-2) has the following structural formula (X is HCO3). - ):

[0048]

[0049] The specific steps for preparing the above-mentioned bicarbonate anionic covalent organic framework (PMCOF-HCO3-2) are as follows:

[0050] (1) Preparation of pyrimidinyl covalent organic framework: 0.1 mmol of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, 0.25 mmol of 1,4-diisocyanobenzene and 0.5 mmol of 2-aminopyridine were dissolved in a mixed solvent consisting of 0.2 mL of ethanol and 1.0 mL of mesitylene. 0.08 mmol of p-toluenesulfonic acid was added to the resulting solution. The solution was then rapidly frozen in liquid nitrogen, vacuumed, sealed, and heated to room temperature before being placed in an oven at 140 °C for 7 days. After the reaction was completed, the solution was filtered, washed and vacuum dried to obtain the pyrimidinyl covalent organic framework.

[0051] (2) Introduction of ionic liquid: Take 100 mg of the pyrimidine covalent organic framework prepared in step (1) and disperse it evenly in 10 mL of ethanol. Add 0.5 mmol of 2-bromoethanol to it and quaternize it at 90 °C for 48 hours. After the reaction is completed, filter, wash and vacuum dry to obtain the brominated hydroxyethylpyrimidine ionic covalent organic framework.

[0052] (3) Ion exchange: Take 80 mg of the brominated hydroxyethyl pyrimidine ionic covalent organic framework prepared in step (2) and disperse it evenly in 10 mL of methanol. Add 0.6 mmol of anhydrous sodium bicarbonate to it, heat to 90 °C and stir for 96 hours. After filtration, washing and drying, the bicarbonate anionic covalent organic framework is obtained, which is denoted as PMCOF-HCO3-2.

[0053] Example 5

[0054] An acetate anionic covalent organic framework (PMCOF-Ac-1) has the following structural formula (X is CH3COO). - ):

[0055]

[0056] The specific steps for preparing the above-mentioned acetate anionic covalent organic framework (PMCOF-Ac-1) are as follows:

[0057] (1) Preparation of pyrimidinyl covalent organic framework: 0.05 mmol of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, 0.075 mmol of 1,4-diisocyanobenzene and 0.15 mmol of 2-aminopyridine were dissolved in a mixed solvent consisting of 0.4 mL of ethanol and 0.8 mL of mesitylene. 0.02 mmol of p-toluenesulfonic acid was added to the resulting solution. The solution was then rapidly frozen in liquid nitrogen, vacuumed, sealed, and heated to room temperature before being placed in an oven at 80 °C for 3 days. After the reaction was completed, the solution was filtered, washed and vacuum dried to obtain the pyrimidinyl covalent organic framework.

[0058] (2) Introduction of ionic liquid: Take 100 mg of the pyrimidine covalent organic framework prepared in step (1) and disperse it evenly in 50 mL of ethanol. Add 0.4 mmol of 2-bromoethanol to it and quaternize it at 30 °C for 48 hours. After the reaction is completed, filter, wash and vacuum dry to obtain the brominated hydroxyethylpyrimidine ionic covalent organic framework.

[0059] (3) Ion exchange: Take 80 mg of the brominated hydroxyethyl pyrimidine ionic covalent organic framework prepared in step (2) and disperse it evenly in 10 mL of methanol. Add 0.5 mmol of anhydrous sodium acetate to it, heat to 90 °C and stir for 48 hours. After filtration, washing and drying, the acetate anionic covalent organic framework is obtained, which is denoted as PMCOF-Ac-1.

[0060] Example 6

[0061] An acetate anionic covalent organic framework (PMCOF-Ac-2) has the following structural formula (X is CH3COO). - ):

[0062]

[0063] The specific steps for preparing the above-mentioned acetate anionic covalent organic framework (PMCOF-Ac-2) are as follows:

[0064] (1) Preparation of pyrimidinyl covalent organic framework: 0.1 mmol of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, 0.25 mmol of 1,4-diisocyanophenyl and 0.5 mmol of 2-aminopyridine were dissolved in a mixed solvent consisting of 0.2 mL of ethanol and 1.0 mL of mesitylene. 0.08 mmol of p-toluenesulfonic acid was added to the resulting solution. The solution was then rapidly frozen in liquid nitrogen, vacuumed, sealed, and heated to room temperature before being placed in an oven at 100 °C for 5 days. After the reaction was completed, the solution was filtered, washed and vacuum dried to obtain the pyrimidinyl covalent organic framework.

[0065] (2) Introduction of ionic liquid: Take 100 mg of the pyrimidine covalent organic framework prepared in step (1) and disperse it evenly in 10 mL of ethanol. Add 0.5 mmol of 2-bromoethanol to it and quaternize it at 60 °C for 48 hours. After the reaction is completed, filter, wash and vacuum dry to obtain the brominated hydroxyethylpyrimidine ionic covalent organic framework.

[0066] (3) Ion exchange: Take 80 mg of the brominated hydroxyethylpyrimidine ionic covalent organic framework prepared in step (2) and disperse it evenly in 10 mL of methanol. Add 0.6 mmol of anhydrous sodium acetate to it, heat to 70 °C and stir for 72 hours. After filtration, washing and drying, the acetate anionic covalent organic framework is obtained, which is denoted as PMCOF-Ac-2.

[0067] Example 7

[0068] A carbonate anionic covalent organic framework (PMCOF-CO3-1) has the following structural formula (X is CO3). 2- ):

[0069]

[0070] The specific steps for preparing the above-mentioned carbonate anionic covalent organic framework (PMCOF-CO3-1) are as follows:

[0071] (1) Preparation of pyrimidinyl covalent organic framework: 0.05 mmol of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, 0.075 mmol of 1,4-diisocyanobenzene and 0.15 mmol of 2-aminopyridine were dissolved in a mixed solvent consisting of 0.4 mL of ethanol and 0.8 mL of mesitylene. 0.02 mmol of p-toluenesulfonic acid was added to the resulting solution. The solution was then rapidly frozen in liquid nitrogen, vacuumed, sealed, and heated to room temperature before being placed in an oven at 120 °C for 6 days. After the reaction was completed, the solution was filtered, washed and vacuum dried to obtain the pyrimidinyl covalent organic framework.

[0072] (2) Introduction of ionic liquid: Take 100 mg of the pyrimidine covalent organic framework prepared in step (1) and disperse it evenly in 50 mL of ethanol. Add 0.4 mmol of 2-bromoethanol to it and quaternize it at 80 °C for 24 hours. After the reaction is completed, filter, wash and vacuum dry to obtain the brominated hydroxyethylpyrimidine ionic covalent organic framework.

[0073] (3) Ion exchange: Take 80 mg of the brominated hydroxyethyl pyrimidine ionic covalent organic framework prepared in step (2) and disperse it evenly in 10 mL of methanol. Add 0.5 mmol of anhydrous sodium carbonate to it, heat to 80 °C and stir for 96 hours. After filtration, washing and drying, the carbonate anionic covalent organic framework is obtained, which is denoted as PMCOF-CO3-1.

[0074] Example 8

[0075] A carbonate anionic covalent organic framework (PMCOF-CO3-2) has the following structural formula (X is CO3). 2- ):

[0076]

[0077] The specific steps for preparing the above-mentioned carbonate anionic covalent organic framework (PMCOF-CO3-2) are as follows:

[0078] (1) Preparation of pyrimidinyl covalent organic framework: 0.1 mmol of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, 0.25 mmol of 1,4-diisocyanobenzene and 0.5 mmol of 2-aminopyridine were dissolved in a mixed solvent consisting of 0.2 mL of ethanol and 1.0 mL of mesitylene. 0.08 mmol of p-toluenesulfonic acid was added to the resulting solution. The solution was then rapidly frozen in liquid nitrogen, vacuumed, sealed, and heated to room temperature before being placed in an oven at 140 °C for 7 days. After the reaction was completed, the solution was filtered, washed and vacuum dried to obtain the pyrimidinyl covalent organic framework.

[0079] (2) Introduction of ionic liquid: Take 100 mg of the pyrimidine covalent organic framework prepared in step (1) and disperse it evenly in 10 mL of ethanol. Add 0.5 mmol of 2-bromoethanol to it and quaternize it at 90 °C for 48 hours. After the reaction is completed, filter, wash and vacuum dry to obtain the brominated hydroxyethylpyrimidine ionic covalent organic framework.

[0080] (3) Ion exchange: Take 80 mg of the brominated hydroxyethyl pyrimidine ionic covalent organic framework prepared in step (2) and disperse it evenly in 10 mL of methanol. Add 0.6 mmol of anhydrous sodium carbonate to it, heat to 90 °C and stir for 96 hours. After filtration, washing and drying, the carbonate anionic covalent organic framework is obtained, which is denoted as PMCOF-CO3-2.

[0081] Application Example 1

[0082] 15 mmol of styrene oxide, 75 mmol of methanol and 30 mg of the PMCOF-OH-1 catalyst prepared in Example 1 were added together into a 50 mL high-pressure reactor with magnetic stirring. The sealed reactor was purged with high-purity CO2 3-5 times to remove air, and then reacted at 100 °C and 5 bar CO2 for 0.5 h.

[0083] After the reaction was completed, n-butanol was added as an internal standard. The resulting product was filtered and the supernatant was analyzed by gas chromatography. The conversion rate of the epoxide was 81%, and the yield of DMC was 43%.

[0084] Application Example 2

[0085] 15 mmol of 1,2-epoxydodecane, 150 mmol of methanol and 45 mg of the PMCOF-OH-2 catalyst prepared in Example 2 were added together into a 50 mL high-pressure reactor with magnetic stirring. The sealed reactor was purged with high-purity CO2 3-5 times to remove air, and then reacted at 140 °C and 15 bar CO2 for 1 h.

[0086] After the reaction was completed, n-butanol was added as an internal standard. The resulting product was filtered and the supernatant was analyzed by gas chromatography. The conversion rate of the epoxide was found to be 82%, and the yield of DMC was 47%.

[0087] Application Example 3

[0088] 15 mmol epichlorohydrin, 200 mmol methanol and 60 mg of the PMCOF-HCO3-1 catalyst prepared in Example 3 were added together into a 50 mL high-pressure reactor with magnetic stirring. The sealed reactor was purged with high-purity CO2 3-5 times to remove air, and then reacted at 100 °C and 5 bar CO2 for 1.5 h.

[0089] After the reaction was completed, n-butanol was added as an internal standard. The resulting product was filtered and the supernatant was analyzed by gas chromatography. The conversion rate of the epoxide was 95% and the yield of DMC was 56%.

[0090] Application Example 4

[0091] 15 mmol glycidyl ether, 225 mmol methanol and 75 mg of the PMCOF-HCO3-2 catalyst prepared in Example 4 were added together into a 50 mL high-pressure reactor with magnetic stirring. The sealed reactor was purged with high-purity CO2 3-5 times to remove air, and then reacted at 140 °C and 15 bar CO2 for 2 h.

[0092] After the reaction was completed, n-butanol was added as an internal standard. The resulting product was filtered and the supernatant was analyzed by gas chromatography. The conversion rate of the epoxide was 97% and the yield of DMC was 59%.

[0093] Application Example 5

[0094] 15 mmol of styrene oxide, 75 mmol of methanol and 30 mg of the PMCOF-Ac-1 catalyst prepared in Example 5 were added together into a 50 mL high-pressure reactor with magnetic stirring. The sealed reactor was purged with high-purity CO2 3-5 times to remove air, and then reacted at 100 °C and 5 bar CO2 for 0.5 h.

[0095] After the reaction was completed, n-butanol was added as an internal standard. The resulting product was filtered and the supernatant was analyzed by gas chromatography. The conversion rate of the epoxide was 79%, and the yield of DMC was 42%.

[0096] Application Example 6

[0097] 15 mmol of 1,2-epoxydodecane, 150 mmol of methanol and 45 mg of the PMCOF-Ac-2 catalyst prepared in Example 6 were added together into a 50 mL high-pressure reactor with magnetic stirring. The sealed reactor was purged with high-purity CO2 3-5 times to remove air, and then reacted at 140 °C and 15 bar CO2 for 1 h.

[0098] After the reaction was completed, n-butanol was added as an internal standard. The resulting product was filtered and the supernatant was analyzed by gas chromatography. The conversion rate of the epoxide was 83% and the yield of DMC was 48%.

[0099] Application Example 7

[0100] 15 mmol epichlorohydrin, 200 mmol methanol and 60 mg of the PMCOF-CO3-1 catalyst prepared in Example 7 were added together into a 50 mL high-pressure reactor with magnetic stirring. The sealed reactor was purged with high-purity CO2 3-5 times to remove air, and then reacted at 100 °C and 5 bar CO2 for 1.5 h.

[0101] After the reaction was completed, n-butanol was added as an internal standard. The resulting product was filtered and the supernatant was analyzed by gas chromatography. The conversion rate of the epoxide was 93% and the yield of DMC was 57%.

[0102] Application Example 8

[0103] 15 mmol glycidyl ether, 225 mmol methanol and 75 mg of the PMCOF-CO3-2 catalyst prepared in Example 8 were added together into a 50 mL high-pressure reactor with magnetic stirring. The sealed reactor was purged with high-purity CO2 3-5 times to remove air, and then reacted at 140 °C and 15 bar CO2 for 2 h.

[0104] After the reaction was completed, n-butanol was added as an internal standard. The resulting product was filtered and the supernatant was analyzed by gas chromatography. The conversion rate of the epoxide was 94%, and the yield of DMC was 60%.

[0105] Table 1 Comparison of process conditions and reaction results in Application Examples 1-8

[0106]

[0107] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also within the protection scope of the present invention.

Claims

1. A base ion-type covalent organic framework material, characterized in that, A pyrimidine-containing covalent organic framework was obtained through a condensation reaction using 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, 1,4-diisocyanophenyl, and 2-aminopyridine as building blocks. This framework was then followed by quaternization and ion exchange reactions to yield a basic ionic covalent organic framework, the structure of which is shown below: X is OH - CO3 2- HCO3 - or CH3COO - .

2. A method for preparing a base ion-type covalent organic framework material as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of pyrimidinyl covalent organic framework: 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, 1,4-diisocyanophenyl and 2-aminopyridine were dissolved in a mixed solvent composed of ethanol and mesitylene to obtain solution A; p-toluenesulfonic acid was added to the obtained solution A, and the solution was rapidly frozen in liquid nitrogen, sealed under vacuum, and then placed in an oven for condensation reaction after being heated to room temperature. After the reaction was completed, the solution was filtered, washed and vacuum dried to obtain pyrimidinyl covalent organic framework. (2) Preparation of ionic covalent organic framework of hydroxyethyl pyrimidine bromide: The pyrimidine covalent organic framework prepared in step (1) is uniformly dispersed in ethanol to obtain solution B; 2-bromoethanol is added to the obtained solution B to carry out quaternization reaction. After the reaction is completed, the solution is filtered, washed and vacuum dried to obtain ionic covalent organic framework of hydroxyethyl pyrimidine bromide. (3) Preparation of basic ionic covalent organic framework: The brominated hydroxyethyl pyrimidine ionic covalent organic framework prepared in step (2) is uniformly dispersed in methanol to obtain solution C; an ion exchanger is added to the obtained solution C to carry out an ion exchange reaction to obtain a basic ionic covalent organic framework.

3. The method for preparing an alkali ion-type covalent organic framework material according to claim 2, characterized in that, In step (1), the molar ratio of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine, 1,4-diisocyanophenyl and 2-aminopyridine is 2:3-5:6-10; the molar ratio of toluenesulfonic acid to 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine is 2-4:5; the molar concentration of 2,4,6-tris(4-aldehydephenyl)-1,3,5-triazine in the mixed solvent is 0.125-0.25 mmol / mL; and the volume ratio of ethanol to mesitylene is 1:2-5.

4. The method for preparing an alkali ion-type covalent organic framework material according to claim 2, characterized in that, In step (1), the condensation reaction is carried out at a temperature of 80–140°C for 3–7 days.

5. The method for preparing an alkali ion-type covalent organic framework material according to claim 2, characterized in that, In step (2), the molar concentration of 2-bromoethanol in ethanol is 0.008–0.05 mmol / mL; the mass concentration of the pyrimidinyl covalent organic framework in ethanol is 2–10 mg / mL.

6. The method for preparing an alkali ion-type covalent organic framework material according to claim 2, characterized in that, In step (2), the temperature of the quaternization reaction is 30–90°C and the time is 24–48 h.

7. The method for preparing an alkali ion-type covalent organic framework material according to claim 2, characterized in that, In step (3), the molar concentration of the ion exchanger in methanol is 0.01 to 0.06 mmol / mL; the mass concentration of the brominated hydroxyethylpyrimidine ionic covalent organic framework in methanol is 1.6 to 8 mg / mL; and the ion exchanger is sodium hydroxide, anhydrous sodium carbonate, anhydrous sodium bicarbonate, or sodium acetate.

8. The method for preparing an alkali ion-type covalent organic framework material according to claim 2, characterized in that, In step (3), the temperature of the ion exchange reaction is 60–90°C and the time is 48–96 h.

9. The method for using the alkali ion type covalent organic framework material as described in claim 1 in the one-pot synthesis of dimethyl carbonate from CO2, epoxides and methanol.

10. The application method according to claim 9, characterized in that, include: An epoxy compound, methanol, and a base ion-type covalent organic framework material were added together into a high-pressure reactor. The molar ratio of the epoxy compound to methanol was 1:5–15, and the mass concentration of the base ion-type covalent organic framework material in the epoxy compound was 2–5 mg / mmol. CO2 was then introduced to carry out the synthesis reaction. The reaction temperature was set at 100–140 °C, the reaction pressure at 5–15 bar, and the reaction time at 0.5–2 h.

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