Alkali ion type covalent organic framework material as well as preparation method and application thereof

Abstract

The invention discloses an alkali ion type covalent organic framework material as well as a preparation method and application thereof.The alkali ion type covalent organic framework material is prepared by taking 2, 4, 6-tri (4-formyl phenyl)-1, 3, 5-triazine, 1, 4-diisocyanobenzene and 2-aminopyridine as construction units, obtaining a pyrimidine-containing covalent organic framework through condensation reaction, and then sequentially carrying out quaternization reaction and ion exchange reaction to obtain the alkali ion type covalent organic framework material. The alkaline ionic covalent organic framework is obtained. The alkali ion type covalent organic framework material prepared by the invention has abundant alkaline sites, a developed pore structure and good chemical stability, shows good catalytic performance when being used as a catalyst for preparing dimethyl carbonate from CO2, an epoxy compound and methanol in a one-pot manner, and shows good cycle stability.

Description

Technical Field

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

[0002] The high consumption of fossil energy has led to a continuous increase in CO2 in the atmosphere, 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 method of preparing dimethyl carbonate (DMC) from CO2, epoxides and methanol in one pot can not only retain the high yield of the CO2 indirect synthesis method, but also omit the separation operation of the intermediate product cyclic carbonate. Compared with other processes, it has more advantages in CO2 activation and DMC synthesis. However, the catalytic performance of the existing catalysts used for the one-pot preparation of dimethyl carbonate (DMC) from CO2, epoxides and methanol is poor, and the CO2 conversion rate and product yield are not high.

[0003] Covalent organic frameworks (COFs) are a new type of crystalline porous material with a highly ordered two-dimensional or three-dimensional network structure. They have broad application prospects in adsorption, chemical sensing, heterogeneous catalysis, proton conduction, and energy storage. The most significant advantage of COFs is that they connect building blocks through reversible covalent bonds. Their structure and function can be easily customized by changing the size and type of building blocks, engineering the pore surface, and forming specific connections. Therefore, using them as catalysts for the one-pot preparation of dimethyl carbonate (DMC) from CO2, epoxides, and methanol is expected to improve CO2 conversion and product yield. However, to achieve excellent crystallinity, the reaction used to prepare COFs is usually required to have high thermodynamic reversibility. This also leads to poor stability of COFs and their easy decomposition under acidic and alkaline conditions, making them unsuitable for the one-pot preparation of DMC from CO2, epoxides, and methanol. Summary of the Invention

[0004] In order to solve the technical problems that the conversion rate of CO2 and the yield of products of existing common catalysts used for CO2 and epoxides are low, and the stability of existing COFs materials is poor and cannot be used for the one-pot preparation of dimethyl carbonate from CO2, epoxides and methanol, the present invention provides an alkali ion covalent organic framework material and a preparation method thereof, as well as its application in the one-pot preparation of DMC from CO2, epoxides and methanol.

[0005] The technical solution adopted in the present invention is:

[0006] An alkaline ionic covalent organic framework material is composed of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 1,4-diisocyanobenzene and 2-aminopyridine as building blocks. A pyrimidine-containing covalent organic framework is obtained through a condensation reaction. The alkaline ionic covalent organic framework is then obtained through a quaternization reaction and an ion exchange reaction. Its structural formula is as follows:

[0007]

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

[0009] The method for preparing the above-mentioned alkali ion type covalent organic framework material comprises the following steps:

[0010] (1) Preparation of a pyrimidine-based covalent organic framework: 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 1,4-diisocyanobenzene, and 2-aminopyridine are dissolved in a mixed solvent consisting of ethanol and mesitylene to obtain a solution A; p-toluenesulfonic acid is added to the obtained solution A, which is rapidly frozen in liquid nitrogen, sealed under vacuum, and then heated to room temperature and placed in an oven for condensation reaction. After the reaction is completed, the solution is filtered, washed, and vacuum-dried to obtain a pyrimidine-based covalent organic framework;

[0011] (2) Preparation of a brominated hydroxyethyl pyrimidinium ionic covalent organic framework: uniformly dispersing the pyrimidinyl covalent organic framework prepared in step (1) in ethanol to obtain a solution B; adding 2-bromoethanol to the obtained solution B to carry out a quaternization reaction; after the reaction is completed, filtering, washing, and vacuum drying to obtain a brominated hydroxyethyl pyrimidinium ionic covalent organic framework;

[0012] (3) Preparation of an alkaline ionic covalent organic framework: The brominated hydroxyethyl pyrimidinium ionic covalent organic framework prepared in step (2) is uniformly dispersed in methanol to obtain a solution C; an ion exchange agent is added to the obtained solution C to carry out an ion exchange reaction to obtain an alkaline ionic covalent organic framework.

[0013] Preferably, in step (1), the molar ratio of 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 1,4-diisocyanobenzene 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 0.125~0.25mmol / mL; and the volume ratio of ethanol to mesitylene is 1:2~5.

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

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

[0016] Preferably, in step (2), the temperature of the quaternization reaction is 30 to 90° C., and the time is 24 to 48 hours.

[0017] Preferably, 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 hydroxyethyl pyrimidinium 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.

[0018] Preferably, in step (3), the temperature of the ion exchange reaction is 60 to 90° C., and the time is 48 to 96 hours.

[0019] The invention relates to an application method of the above-mentioned alkaline ion type covalent organic framework material in the one-pot synthesis of dimethyl carbonate from CO2, epoxy compounds and methanol.

[0020] Preferably, the above-mentioned application method includes adding an epoxy compound, methanol and an alkali ion covalent organic framework material into a high-pressure reactor, wherein the molar ratio of the epoxy compound to methanol is 1:5-15, and the mass concentration of the alkali ion covalent organic framework material in the epoxy compound is 2-5 mg / mmol, and then introducing CO2 for synthesis reaction, setting the reaction temperature to 100-140°C, the reaction pressure to 5-15 bar, and the reaction time to 0.5-2h.

[0021] Beneficial effects of the present invention:

[0022] (1) This invention integrates functional group design and ultrastability in COF synthesis using isonitrile chemistry. These pyrimidine-based COFs not only possess ultrastability under alkaline conditions due to the ubiquitous presence of imidazole rings, but also facilitate the introduction of ionic liquids, providing more possibilities for directional material regulation. Furthermore, structural diversity can be further achieved through the use of pre-designed isonitrile or aldehyde monomers.

[0023] (2) The alkaline ion covalent organic framework material prepared by the present invention has abundant alkaline sites, a developed pore structure and good thermal stability. It exhibits good catalytic performance as a catalyst for the one-pot preparation of dimethyl carbonate from CO2, epoxy compounds and methanol, and shows good cyclic stability. It 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 purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction 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) comprises the following specific steps:

[0029] (1) Preparation of 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-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, which was quickly frozen in liquid nitrogen and vacuumed, then sealed. After warming to room temperature, the solution was placed in an oven at 80°C for reaction for 3 days. After the reaction was completed, the solution was filtered, washed and vacuum-dried to obtain a pyrimidine-based covalent organic framework.

[0030] (2) Introduction of ionic liquid: 100 mg of the pyrimidine-based covalent organic framework prepared in step (1) was uniformly dispersed in 50 mL of ethanol, 0.4 mmol of 2-bromoethanol was added thereto, and quaternization reaction was carried out at 30° C. for 24 hours. After the reaction was completed, the mixture was filtered, washed, and vacuum-dried to obtain a brominated hydroxyethyl pyrimidinium ionic covalent organic framework.

[0031] (3) Ion exchange: 80 mg of the brominated hydroxyethyl pyrimidinium ionic covalent organic framework prepared in step (2) was uniformly dispersed in 50 mL of methanol, 0.5 mmol of sodium hydroxide was added thereto, and the mixture was heated to 60° C. and stirred for 48 hours. After filtration, washing, and drying, a hydroxide anion covalent organic framework material was obtained, which was designated 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 preparation method of the above-mentioned hydroxide anion type covalent organic framework material (PMCOF-OH-2) comprises the following specific steps:

[0036] (1) Preparation of pyrimidine-based covalent organic framework: 0.1 mmol of 2,4,6-tris(4-formylphenyl)-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, which was quickly frozen in liquid nitrogen and vacuumed, then sealed. After warming to room temperature, the solution was placed in an oven at 100°C for reaction for 5 days. After the reaction was completed, the solution was filtered, washed and vacuum-dried to obtain a pyrimidine-based covalent organic framework.

[0037] (2) Introduction of ionic liquid: 100 mg of the pyrimidine-based covalent organic framework prepared in step (1) was uniformly dispersed in 10 mL of ethanol, 0.5 mmol of 2-bromoethanol was added thereto, and quaternization reaction was carried out at 60° C. for 48 hours. After the reaction was completed, the mixture was filtered, washed, and vacuum-dried to obtain a brominated hydroxyethyl pyrimidinium ionic covalent organic framework.

[0038] (3) Ion exchange: 80 mg of the brominated hydroxyethyl pyrimidinium ionic covalent organic framework prepared in step (2) was uniformly dispersed in 10 mL of methanol, 0.6 mmol of sodium hydroxide was added thereto, and the mixture was heated to 70° C. and stirred for 72 hours. After filtration, washing, and drying, a hydroxide anion covalent organic framework material was obtained, which was designated as PMCOF-OH-2.

[0039] Example 3

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

[0041]

[0042] The preparation method of the above-mentioned bicarbonate ion type covalent organic framework (PMCOF-HCO3-1) comprises the following specific steps:

[0043] (1) Preparation of 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-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, which was quickly frozen in liquid nitrogen and vacuumed, then sealed. After warming to room temperature, the solution was placed in an oven at 120°C for reaction for 6 days. After the reaction was completed, the solution was filtered, washed and vacuum-dried to obtain a pyrimidine-based covalent organic framework.

[0044] (2) Introduction of ionic liquid: 100 mg of the pyrimidine-based covalent organic framework prepared in step (1) was uniformly dispersed in 50 mL of ethanol, 0.4 mmol of 2-bromoethanol was added thereto, and quaternization reaction was carried out at 80° C. for 24 hours. After the reaction was completed, the mixture was filtered, washed, and vacuum-dried to obtain a brominated hydroxyethyl pyrimidinium ionic covalent organic framework.

[0045] (3) Ion exchange: 80 mg of the brominated hydroxyethylpyrimidinium ionic covalent organic framework prepared in step (2) was uniformly dispersed in 10 mL of methanol, 0.5 mmol of anhydrous sodium bicarbonate was added thereto, and the mixture was heated to 80° C. and stirred for 96 hours. After filtration, washing, and drying, a bicarbonate ionic covalent organic framework was obtained, which was designated as PMCOF-HCO3-1.

[0046] Example 4

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

[0048]

[0049] The preparation method of the above-mentioned bicarbonate anion type covalent organic framework (PMCOF-HCO3-2) comprises the following specific steps:

[0050] (1) Preparation of pyrimidine-based covalent organic framework: 0.1 mmol of 2,4,6-tris(4-formylphenyl)-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, which was quickly frozen in liquid nitrogen and vacuumed, then sealed. After warming to room temperature, the solution was placed in an oven at 140°C for reaction for 7 days. After the reaction was completed, the solution was filtered, washed and vacuum-dried to obtain a pyrimidine-based covalent organic framework.

[0051] (2) Introduction of ionic liquid: 100 mg of the pyrimidine-based covalent organic framework prepared in step (1) was uniformly dispersed in 10 mL of ethanol, 0.5 mmol of 2-bromoethanol was added thereto, and quaternization reaction was carried out at 90° C. for 48 hours. After the reaction was completed, the mixture was filtered, washed, and vacuum-dried to obtain a brominated hydroxyethyl pyrimidinium ionic covalent organic framework.

[0052] (3) Ion exchange: 80 mg of the brominated hydroxyethylpyrimidinium ionic covalent organic framework prepared in step (2) was uniformly dispersed in 10 mL of methanol, 0.6 mmol of anhydrous sodium bicarbonate was added thereto, and the mixture was heated to 90° C. and stirred for 96 hours. After filtration, washing, and drying, a bicarbonate anionic covalent organic framework was obtained, which was designated as PMCOF-HCO3-2.

[0053] Example 5

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

[0055]

[0056] The preparation method of the above-mentioned acetate anion type covalent organic framework (PMCOF-Ac-1) comprises the following specific steps:

[0057] (1) Preparation of 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-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, which was quickly frozen in liquid nitrogen and vacuumed, then sealed. After warming to room temperature, the solution was placed in an oven at 80°C for reaction for 3 days. After the reaction was completed, the solution was filtered, washed and vacuum-dried to obtain a pyrimidine-based covalent organic framework.

[0058] (2) Introduction of ionic liquid: 100 mg of the pyrimidine-based covalent organic framework prepared in step (1) was uniformly dispersed in 50 mL of ethanol, 0.4 mmol of 2-bromoethanol was added thereto, and quaternization reaction was carried out at 30° C. for 48 hours. After the reaction was completed, the mixture was filtered, washed, and vacuum-dried to obtain a brominated hydroxyethyl pyrimidinium ionic covalent organic framework.

[0059] (3) Ion exchange: 80 mg of the brominated hydroxyethylpyrimidinium ionic covalent organic framework prepared in step (2) was uniformly dispersed in 10 mL of methanol, 0.5 mmol of anhydrous sodium acetate was added thereto, and the mixture was heated to 90° C. and stirred for 48 hours. After filtration, washing, and drying, an acetate anionic covalent organic framework was obtained, which was designated as PMCOF-Ac-1.

[0060] Example 6

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

[0062]

[0063] The preparation method of the above-mentioned acetate anion type covalent organic framework (PMCOF-Ac-2) comprises the following specific steps:

[0064] (1) Preparation of pyrimidine-based covalent organic framework: 0.1 mmol of 2,4,6-tris(4-formylphenyl)-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, which was quickly frozen in liquid nitrogen and vacuumed, then sealed. After warming to room temperature, the solution was placed in an oven at 100°C for reaction for 5 days. After the reaction was completed, the solution was filtered, washed and vacuum-dried to obtain a pyrimidine-based covalent organic framework.

[0065] (2) Introduction of ionic liquid: 100 mg of the pyrimidine-based covalent organic framework prepared in step (1) was uniformly dispersed in 10 mL of ethanol, 0.5 mmol of 2-bromoethanol was added thereto, and quaternization reaction was carried out at 60° C. for 48 hours. After the reaction was completed, the mixture was filtered, washed, and vacuum-dried to obtain a brominated hydroxyethyl pyrimidinium ionic covalent organic framework.

[0066] (3) Ion exchange: 80 mg of the brominated hydroxyethylpyrimidinium ionic covalent organic framework prepared in step (2) was uniformly dispersed in 10 mL of methanol, 0.6 mmol of anhydrous sodium acetate was added thereto, and the mixture was heated to 70° C. and stirred for 72 hours. After filtration, washing, and drying, an acetate anionic covalent organic framework was obtained, which was designated as PMCOF-Ac-2.

[0067] Example 7

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

[0069]

[0070] The preparation method of the carbonate anion type covalent organic framework (PMCOF-CO3-1) comprises the following specific steps:

[0071] (1) Preparation of 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-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, which was quickly frozen in liquid nitrogen and vacuumed, then sealed. After warming to room temperature, the solution was placed in an oven at 120°C for reaction for 6 days. After the reaction was completed, the solution was filtered, washed and vacuum-dried to obtain a pyrimidine-based covalent organic framework.

[0072] (2) Introduction of ionic liquid: 100 mg of the pyrimidine-based covalent organic framework prepared in step (1) was uniformly dispersed in 50 mL of ethanol, 0.4 mmol of 2-bromoethanol was added thereto, and quaternization reaction was carried out at 80° C. for 24 hours. After the reaction was completed, the mixture was filtered, washed, and vacuum-dried to obtain a brominated hydroxyethyl pyrimidinium ionic covalent organic framework.

[0073] (3) Ion exchange: 80 mg of the brominated hydroxyethyl pyrimidinium ionic covalent organic framework prepared in step (2) was uniformly dispersed in 10 mL of methanol, 0.5 mmol of anhydrous sodium carbonate was added thereto, and the mixture was heated to 80° C. and stirred for 96 hours. After filtration, washing, and drying, a carbonate anionic covalent organic framework was obtained, which was designated as PMCOF-CO3-1.

[0074] Example 8

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

[0076]

[0077] The preparation method of the above-mentioned carbonate anion type covalent organic framework (PMCOF-CO3-2) comprises the following specific steps:

[0078] (1) Preparation of pyrimidine-based covalent organic framework: 0.1 mmol of 2,4,6-tris(4-formylphenyl)-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, which was quickly frozen in liquid nitrogen and vacuumed, then sealed. After warming to room temperature, the solution was placed in an oven at 140°C for reaction for 7 days. After the reaction was completed, the solution was filtered, washed and vacuum-dried to obtain a pyrimidine-based covalent organic framework.

[0079] (2) Introduction of ionic liquid: 100 mg of the pyrimidine-based covalent organic framework prepared in step (1) was uniformly dispersed in 10 mL of ethanol, 0.5 mmol of 2-bromoethanol was added thereto, and quaternization reaction was carried out at 90° C. for 48 hours. After the reaction was completed, the mixture was filtered, washed, and vacuum-dried to obtain a brominated hydroxyethyl pyrimidinium ionic covalent organic framework.

[0080] (3) Ion exchange: 80 mg of the brominated hydroxyethylpyrimidinium ionic covalent organic framework prepared in step (2) was uniformly dispersed in 10 mL of methanol, 0.6 mmol of anhydrous sodium carbonate was added thereto, and the mixture was heated to 90° C. and stirred for 96 hours. After filtration, washing, and drying, a carbonate anionic covalent organic framework was obtained, which was designated 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 to a 50 mL high-pressure reactor with magnetic stirring. The closed reactor was purged with high-purity CO2 3-5 times to remove all 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, and the obtained product was filtered and the clear liquid was analyzed by gas chromatography. The measured epoxide conversion rate was 81%, and the DMC yield 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 to a 50 mL high-pressure reactor with magnetic stirring. The closed reactor was purged with high-purity CO2 3-5 times to remove all 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, and the obtained product was filtered and the clear liquid was analyzed by gas chromatography. The measured results showed that the conversion rate of epoxy compound was 82% and the yield of DMC was 47%.

[0087] Application Example 3

[0088] 15 mmol of epichlorohydrin, 200 mmol of methanol, and 60 mg of the PMCOF-HCO3-1 catalyst prepared in Example 3 were added to a 50 mL high-pressure reactor with magnetic stirring. The closed reactor was purged with high-purity CO2 3-5 times to remove all 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, and the obtained product was filtered and the clear liquid was analyzed by gas chromatography. The measured results showed that the conversion rate of epoxy compound was 95% and the yield of DMC was 56%.

[0090] Application Example 4

[0091] 15 mmol of glycidol, 225 mmol of 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 closed reactor was purged with high-purity CO2 3-5 times to remove all 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, and the obtained product was filtered and the clear liquid was analyzed by gas chromatography. The measured results showed that the conversion rate of epoxy compound 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 to a 50 mL high-pressure reactor with magnetic stirring. The closed reactor was purged with high-purity CO2 3-5 times to remove all 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, and the obtained product was filtered and the clear liquid was analyzed by gas chromatography. The measured results showed that the conversion rate of epoxy compound 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 to a 50 mL high-pressure reactor with magnetic stirring. The closed reactor was purged with high-purity CO2 3-5 times to remove all 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, and the obtained product was filtered and the clear liquid was analyzed by gas chromatography. The measured results showed that the conversion rate of epoxy compound was 83% and the yield of DMC was 48%.

[0099] Application Example 7

[0100] 15 mmol of epichlorohydrin, 200 mmol of methanol, and 60 mg of the PMCOF-CO3-1 catalyst prepared in Example 7 were added to a 50 mL high-pressure reactor with magnetic stirring. The closed reactor was purged with high-purity CO2 3-5 times to remove all 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, and the obtained product was filtered and the clear liquid was analyzed by gas chromatography. The measured results showed that the conversion rate of epoxy compound was 93% and the yield of DMC was 57%.

[0102] Application Example 8

[0103] 15 mmol of glycidol, 225 mmol of methanol, and 75 mg of the PMCOF-CO3-2 catalyst prepared in Example 8 were added to a 50 mL high-pressure reactor with magnetic stirring. The closed reactor was purged with high-purity CO2 3-5 times to remove all 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, and the obtained product was filtered and the clear liquid was analyzed by gas chromatography. The measured epoxide conversion rate was 94%, and the DMC yield was 60%.

[0105] Table 1 Comparison of process conditions and reaction results of application examples 1-8

[0106]

[0107] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also within the scope of protection of the present invention.

Claims

1. An alkali ion type covalent organic framework material, characterized in that: 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 1,4-diisocyanobenzene and 2-aminopyridine are used as building units, and a pyrimidine-containing covalent organic framework is obtained through a condensation reaction, and then a basic ionic covalent organic framework is obtained through a quaternization reaction and an ion exchange reaction. The structural formula is as follows: X is OH - 、CO3 2- 、HCO3 - or CH3COO - .

2. A method for preparing an alkali ion type covalent organic framework material as claimed in claim 1, characterized in that: The following steps are involved: (1) Preparation of pyrimidine-based covalent organic framework: 2,4,6-tris(4-formylphenyl)-1,3,5-triazine, 1,4-diisocyanobenzene and 2-aminopyridine are dissolved in a mixed solvent consisting of ethanol and mesitylene to obtain solution A; p-toluenesulfonic acid is added to the obtained solution A, and the solution is rapidly frozen in liquid nitrogen, sealed by vacuum, and placed in an oven after warming to room temperature for condensation reaction. After the reaction is completed, the solution is filtered, washed and vacuum dried to obtain a pyrimidine-based covalent organic framework; (2) Preparation of brominated hydroxyethyl pyrimidinium ionic covalent organic framework: uniformly dispersing the pyrimidinyl covalent organic framework prepared in step (1) in ethanol to obtain solution B; adding 2-bromoethanol to the obtained solution B for quaternization reaction, and filtering, washing and vacuum drying after the reaction to obtain brominated hydroxyethyl pyrimidinium ionic covalent organic framework; (3) Preparation of an alkaline ionic covalent organic framework: The brominated hydroxyethylpyrimidinium ionic covalent organic framework prepared in step (2) is uniformly dispersed in methanol to obtain a solution C; an ion exchanger is added to the obtained solution C to carry out an ion exchange reaction to obtain an alkaline 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-formylphenyl)-1,3,5-triazine, 1,4-diisocyanobenzene 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.

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 temperature is 80 to 140° C. and the reaction time is 3 to 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; and the mass concentration of the pyrimidine-based 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 to 90° C. and the time is 24 to 48 hours.

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 0.01-0.06 mmol / mL; the mass concentration of the brominated hydroxyethyl pyrimidinium 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.

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 to 90° C. and the time is 48 to 96 hours.

9. A method for using the alkaline ion type covalent organic framework material according to claim 1 in the one-pot synthesis of dimethyl carbonate from CO2, epoxy compounds and methanol.

10. The application method according to claim 9, characterized in that: include: Add epoxy compound, methanol and alkali ion type covalent organic framework material into a high-pressure reactor together, wherein the molar ratio of epoxy compound to methanol is 1:5-15, and the mass concentration of alkali ion type covalent organic framework material in epoxy compound is 2-5 mg / mmol, and then introduce CO2 for synthesis reaction, set the reaction temperature to 100-140°C, the reaction pressure to 5-15 bar, and the reaction time to 0.5-2h.

Images