Column [5] arene covalent organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a column [5] arene covalent organic framework material as well as a preparation method and application thereof, and belongs to the technical field of crystalline organic functional materials. The column [5] arene covalent organic framework material has a structure as shown in a formula I; the invention also discloses a preparation method of the column [5] arene covalent organic framework material and application of the column [5] arene covalent organic framework material in catalysis of addition reaction of CO2 and epoxide to prepare cyclic carbonate. The column [5] arene covalent organic framework material disclosed by the invention can be used as a general catalytic promoter to enhance the catalytic activity of an organic small-molecule catalyst in catalysis of addition reaction of CO2 and epoxide to prepare cyclic carbonate, and has high stability and easiness in separation and recovery.

Description

Technical Field

[0001] The present invention belongs to the technical field of crystalline organic functional materials, and particularly relates to a pillar[5]arene covalent organic framework material, a preparation method thereof, and an application thereof. Background Art

[0002] CO2 gas is a C1 resource with rich reserves, non-toxic and safe. Developing efficient adsorption, capture and catalytic conversion technologies for it not only helps to alleviate environmental problems such as climate change, but also is expected to provide an environmentally friendly green synthesis route for the sustainable development of the economy. However, the concentration of CO2 in the atmosphere is extremely low and its chemical properties are stable. As a gas reactant, its solubility in conventional organic solvents is limited. Usually, cumbersome and energy-consuming separation and purification pretreatment and harsh conditions such as high temperature, high pressure, and metal catalyst activation are required to realize its conversion and utilization. Therefore, developing new strategies and new catalytic systems for efficiently catalyzing the conversion of CO2 to prepare high-value-added chemicals under mild conditions is an urgent and difficult task, with important practical significance.

[0003] Among the numerous reactions currently involving the conversion and utilization of CO2, the cycloaddition reaction of CO2 with epoxides has a theoretical atom utilization rate of 100% due to the fact that the resulting cyclic carbonates or polycarbonate products can be widely used in energy fuels, pharmaceutical intermediates, organic solvents, and fine chemicals. It is a class of CO2 green conversion and utilization pathways with great application potential. However, in the CO2 cycloaddition reaction, due to the limited activity and selectivity of most catalysts, and often requiring harsh high-temperature and high-pressure conditions, it faces high energy consumption and operation safety problems in industrial practical applications. An ideal catalyst for catalyzing the CO2 cycloaddition reaction should have the following characteristics: 1) High reaction activity and selectivity at relatively low temperatures and atmospheric pressure, compatible with a wide range of reaction substrates; 2) Clear structure and strong modular designability, capable of elucidating the main reaction mechanisms involved; 3) Excellent stability and easy separation from reaction products, recyclable; 4) Easy to prepare on a large scale and relatively low cost; 5) Ideally, no use of metals and organic solvents, etc.

[0004] The results of literature research show that the catalysts currently reported for the efficient catalytic cycloaddition of CO2 to prepare cyclic carbonates or polycarbonates can be classified into two major categories: homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts are mainly represented by organic small molecule catalysts such as metal halides, Salen metal complexes, organic phosphonium salts, pyridinium salts, and imidazolium salts. They have high catalytic activity and clear molecular structures, which is conducive to in-depth study of their catalytic conversion mechanisms to guide the rational design of optimizing catalyst structures. However, homogeneous catalysts often require the use of large amounts of organic solvents, and the separation operations with products are widely complex and cumbersome, making it difficult to recover and recycle. Supported heterogeneous catalysts mainly include metal-organic framework materials (MOFs), covalent organic framework materials (COFs), porous organic polymer materials, etc. However, although the above heterogeneous catalysts are easier to separate and recover, their catalytic activities are usually unstable, the reaction conditions often involve high temperature and high pressure, the material structures are not clear, and the control of structural homogeneity is difficult, which is not conducive to functional modification and in-depth study of reaction mechanisms.

[0005] Therefore, how to design a new catalytic system that combines the high activity and high stability of homogeneous catalysts and the easy separation and recyclability of heterogeneous catalysts is one of the technical difficulties to be solved in this field currently. Summary of the Invention

[0006] The purpose of the present invention is to provide a pillar[5]arene covalent organic framework material, its preparation method and application. This pillar[5]arene covalent organic framework material can be used as a universal catalytic aid to enhance the catalytic activity of organic small molecule catalysts, and has high stability and easy separation and recyclability.

[0007] The technical solution adopted to achieve the above purpose is to provide a pillar[5]arene covalent organic framework material, which has a structure shown in Formula I: .

[0008] The beneficial effect of the present invention adopting the above technical solution is that the structure of the pillar[5]arene covalent organic framework material of the present invention contains a pillar[5]arene macrocycle and a pyridine structural unit, belonging to the structure of a novel crystalline pillar[5]arene macrocycle covalent organic framework material. This framework material has a unique ABC stacking model and pore size distribution, enabling it to effectively disperse and expose imidazolium salts, quaternary ammonium salts, and pyridinium salt catalysts through host-guest interactions and enhance their catalytic effects on the cycloaddition reaction of CO2 and epoxides. It belongs to a crystalline organic functional material and can be preferably used in the field of catalytic reactions.

[0009] The present invention also provides a preparation method of the above pillar[5]arene covalent organic framework material, including the following steps: Dissolve 4,4’,4’’-(pyridine-2,4,6-triyl) tribenzaldehyde and pillar[5]arene diamine monomer in a solvent, and carry out a condensation reaction under the action of a catalyst to obtain the pillar[5]arene covalent organic framework material shown in Formula I; its synthesis route is as follows: 。

[0010] Preferably, the solvent is a mixed solution of mesitylene and 1,4-dioxane; the catalyst is an aqueous acetic acid solution; the molar ratio of 4,4’,4’’-(pyridine-2,4,6-triyl) tribenzaldehyde to pillar[5]arene diamine monomer is (0.2~0.3):(0.3~0.4); the condensation reaction temperature is 100~130 °C, and the time is 68~74 h.

[0011] More preferably, the molar ratio of 4,4’,4’’-(pyridine-2,4,6-triyl) tribenzaldehyde to pillar[5]arene diamine monomer is 0.25:0.375; the condensation reaction temperature is 120 °C, and the time is 72 h.

[0012] More preferably, the volume ratio of mesitylene to 1,4-dioxane in the mixed solution is (8~9):(1~2); the molar concentration of the aqueous acetic acid solution is 5~7 M; the volume ratio of the mixed solution to the aqueous acetic acid solution is (40~60):1.

[0013] More preferably, the volume ratio of mesitylene to 1,4-dioxane in the mixed solution is 9:1; the molar concentration of the aqueous acetic acid solution is 6 M; the volume ratio of the mixed solution to the aqueous acetic acid solution is 50:1.

[0014] The present invention also provides the application of the above-mentioned pillar[5]arene covalent organic framework material in the catalytic addition reaction of CO2 and epoxide to prepare cyclic carbonate.

[0015] Preferably, the pillar[5]arene covalent organic framework material cooperates with a cationic organic catalyst to catalyze the addition reaction of CO2 and epoxide to prepare cyclic carbonate.

[0016] The beneficial effects of the present invention adopting the above technical solutions are as follows: The pillar[5]arene covalent organic framework material of the present invention can anchor cationic organic catalysts through pre-coded host-guest interactions, thereby generating separated ion pairs to enhance the CO2 cycloaddition reaction. The structure of the pillar[5]arene covalent organic framework material of the present invention adopts an ABC staggered stacking mode, has good CO2 adsorption performance, and can integrate common cationic organic catalysts, such as imidazolium salts, pyridinium salts, and ammonium salts, through the host-guest interaction of the electron-rich cavity of pillar[5]arene to assemble a plug-and-play catalytic system; compared with the corresponding homogeneous organic catalysts, it shows extraordinary efficiency and activity in the CO2 cycloaddition reaction, the yield is significantly improved, and there is no need to add additional metal or solvent. At the same time, the system formed by the pillar[5]arene covalent organic framework material and the cationic organic catalyst has high reactivity, and a low-concentration CO2 mixed gas can also be used for the efficient preparation of cyclic carbonates, and the pillar[5]arene covalent organic framework material has good stability and can be recycled; the prepared cyclic carbonate product has a high purity and can be separated by filtration and extraction.

[0017] More preferably, the cationic organic catalyst is an imidazolium salt, a quaternary ammonium salt or a pyridinium salt; the epoxide has a structure shown in Formula II or Formula III:

[0018] In the formula: Both R1 or R2 are haloalkyl, C 1-20 linear or branched alkyl, cycloalkyl, alkenyl, aryl or arylalkyl.

[0019] More preferably, the cationic organic catalyst is , , or .

[0020] More preferably, the specific structural formula of the epoxide is as follows: , , , , , , , , , or .

[0021] More preferably, the molar ratio of the pillar[5]arene unit to the cationic organic catalyst in the pillar[5]arene covalent organic framework material is 1:(1~2); the temperature of the addition reaction is 60~100 °C, and the time is 6~24 h.

[0022] The present invention has the following beneficial effects: (1) In the framework of the pillar [5] arene covalent organic framework material of the present invention, the framework structure of the pillar [5] arene covalent organic framework material contains a pillar [5] arene macrocycle and a pyridine unit, which can be used as a general co-catalyst to enhance the catalytic effect of the cationic organic catalyst in the catalytic CO2 cycloaddition reaction.

[0023] (2) The combination of the pillar [5] arene covalent organic framework material of the present invention and the cationic organic catalyst has high catalytic activity, is suitable for the catalytic conversion of low-concentration CO2, is easy to separate from the product, can be recycled, and has good stability. Description of the Drawings

[0024] Figure 1 is the Fourier transform infrared spectrum; among them, (a) is the Fourier transform infrared spectrum of the pillar [5] arene covalent organic framework material prepared in Example 1; (b) is the Fourier transform infrared spectrum of the covalent organic framework material prepared in Comparative Example 1; Figure 2 is the solid-state 13 13C NMR spectrum of the pillar [5] arene covalent organic framework material prepared in Example 1; Figure 3 is the X-ray diffraction pattern and three-dimensional stacking model structure diagram of the covalent organic framework material; among them, (a) is the XRD diffraction pattern of the pillar [5] arene covalent organic framework material prepared in Example 1; (b) is the XRD diffraction pattern of the covalent organic framework material prepared in Comparative Example 1; (c) is the three-dimensional stacking model structure diagram of the pillar [5] arene covalent organic framework material prepared in Example 1; (d) is the three-dimensional stacking model structure diagram of the covalent organic framework material prepared in Comparative Example 1; Figure 4 is the 77 K nitrogen isothermal adsorption test result diagram of the pillar [5] arene covalent organic framework material prepared in Example 1; among them, (a) is the 77 K nitrogen isothermal adsorption curve diagram; (b) is the pore size distribution result diagram; Figure 5 is the SEM image of the pillar [5] arene covalent organic framework material prepared in Example 1; Figure 6 is the TEM image of the pillar [5] arene covalent organic framework material prepared in Example 1; Figure 7 is the CO2 adsorption curve diagram of the pillar [5] arene covalent organic framework material prepared in Example 1; Figure 8 is the thermogravimetric analysis curve diagram of the pillar [5] arene covalent organic framework material prepared in Example 1; Figure 9Separation flowchart of cyclic carbonates prepared by the addition reaction of CO2 and epoxides catalyzed by the pillar[5]arene covalent organic framework material prepared in Example 1 and a cationic organic catalyst Figure 10 Catalytic performance diagrams of different catalysts under CO2 with different volume concentrations; among them, (a) is the catalytic performance diagram of different catalysts under CO2 with a volume concentration of 100%; (b) is the catalytic performance diagram of different catalysts under CO2 with a volume concentration of 15% Figure 11 Diagram of the recycling of the pillar[5]arene covalent organic framework material prepared in Example 1 and the evaluation results of its catalytic activity Detailed implementation manners

[0025] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. For those not specified in the examples, they are carried out under conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained by purchasing on the market

[0026] The features and performance of the present invention are further described in detail below in conjunction with the examples

[0027] Example 1 Pillar[5]arene covalent organic framework material and its preparation method A pillar[5]arene covalent organic framework material, denoted as P5-COF, has a structure shown in Formula I: .

[0028] The preparation method of the pillar[5]arene covalent organic framework material is also disclosed in this example, including the following steps: (1) Weigh 4,4’,4’’-(pyridine-2,4,6-triyl)tribenzaldehyde (100 mg, 0.250 mmol) and pillar[5]arene diamine monomer (325 mg, 0.375 mmol) into a 25 mL Schlenk reaction tube, add mesitylene / 1,4-dioxane (5.0 mL, 9 / 1, v / v) and 0.1 mL acetic acid aqueous solution (6 M). After fully mixing evenly under ultrasonic, freeze it under liquid nitrogen, evacuate and seal the reaction tube, and place it under stirring at 120 °C until light yellow microcrystals precipitate out in the solution. After reacting for 72 h, stop the reaction to obtain the reaction solution (2) After cooling the reaction solution to room temperature, it was filtered by suction to obtain light yellow microcrystals. Then, the microcrystals were washed 5 times with dichloromethane and diethyl ether, and the collected microcrystals were put into a filter paper and subjected to Soxhlet extraction and washing with tetrahydrofuran for 20 h until the color of the washing solution did not change. The obtained microcrystals were vacuum dried at 40 °C for 24 h to obtain the pillar[5]arene covalent organic framework material P5-COF (light yellow crystals, 398 mg, 94%).

[0029] The synthesis route is as follows: 。

[0030] Comparative Example 1 Covalent Organic Framework Material and Its Preparation Method A covalent organic framework material, denoted as TP-COF, has the structure shown in Formula IV: 。

[0031] In this comparative example, the preparation method of the covalent organic framework material is also disclosed, including the following steps: (1) Weigh 4,4’,4’’-(pyridine-2,4,6-triyl)tribenzaldehyde (260 mg, 0.660 mmol) and the terphenyl diamine monomer (260 mg, 0.100 mmol) into a 25 mL Schlenk reaction tube, add mesitylene / 1,4-dioxane (5.0 mL, 9 / 1, v / v) and 0.1 mL of acetic acid aqueous solution (6 M). After thoroughly mixing evenly under ultrasound, it was frozen in liquid nitrogen, evacuated, and then the reaction tube was sealed and placed in a stirring reaction at 120 °C until yellow microcrystals precipitated out in the solution. After reacting for 72 h, the reaction was stopped to obtain the reaction solution; (2) After cooling the reaction solution to room temperature, it was filtered by suction to obtain light yellow microcrystals. Then, the microcrystals were washed 5 times with dichloromethane and diethyl ether, and the collected microcrystals were put into a filter paper and subjected to Soxhlet extraction and washing with tetrahydrofuran for 20 h until the color of the washing solution did not change. The obtained microcrystals were vacuum dried at 40 °C for 24 h to obtain the covalent organic framework material TP-COF (yellow crystals, 348 mg, 67%).

[0032] The synthesis route is as follows: 。

[0033] Experimental Example 1 Structural Characterization of Materials 1 Fourier Transform Infrared Spectroscopy and Carbon Spectrum Tests of P5-COF The column [5] arene covalent organic framework material P5-COF and the reaction raw material monomer column [5] arene diamine monomer P5 and 4,4’,4’’-(pyridine-2,4,6-triyl) tribenzaldehyde Py were comparatively analyzed using Fourier transform infrared spectroscopy (FT-IR), and the covalent organic framework material TP-COF and the reaction raw material monomer terphenyl diamine monomer TP and 4,4’,4’’-(pyridine-2,4,6-triyl) tribenzaldehyde Py were comparatively analyzed. The results are as Figure 1 shown.

[0034] The solid-state 13 13C NMR of the column [5] arene covalent organic framework material P5-COF in the solid state was analyzed. The results are as Figure 2 shown.

[0035] As can be seen from Figure 1 , in the FT-IR of P5-COF, the characteristic N-H vibration peak of the P5 amino group (-NH2) did not appear at 3446 cm -1 and 3361 cm -1 . In addition, the peak at 1699 cm -1 related to the C=O stretching vibration of the aldehyde group (-CHO) of the Py monomer also disappeared, indicating that the two monomers had been completely converted. The newly generated peak at 1599 cm -1 could be assigned to the stretching vibration peak of the imine linking group -C=N, indicating that imine polymerization had occurred successfully; Figure 1 In Figure (a) of Figure 2 combined with the solid-state 13 13C NMR spectrum, it can be seen that the column [5] arene covalent organic framework material P5-COF was successfully synthesized. In the FT-IR of TP-COF, it was also found that the characteristic N-H vibration peak of the TP amino group (-NH2) and the peak related to the C=O stretching vibration of the aldehyde group (-CHO) of the Py monomer did not appear, indicating that the two monomers had been completely converted. At the same time, the stretching vibration peak of the imine linking group -C=N was generated, indicating that the covalent organic framework material TP-COF was successfully synthesized ( Figure 1 Figure (b) in

[0036] 2 XRD diffraction test of P5-COF and TP-COF The column [5] arene covalent organic framework material P5-COF prepared in Example 1 and the covalent organic framework material TP-COF prepared in Comparative Example 1 were subjected to XRD diffraction test. The results are as Figure 3 shown.

[0037] As can be seen from Figure 3 , in the small-angle region (2~10 o)(It) has a series of diffraction peaks, indicating that the material is a crystalline material; according to the symmetries of monomers P5 and Py, three types of stacking models of framework structures AA, AB, and ABC were constructed. It was found that the strongest diffraction peak 2θ in the small-angle region of the framework material is basically consistent with the diffraction peak position of the ABC stacking model, indicating that the framework adopts the ABC stacking model, which is completely different from the existing AA stacking model; Using Materials Studio 2023 to refine and simulate the experimental results, it is obtained that P5-COF belongs to the P31 symmetry group, and the unit cell parameters are a = 50.2 Å, b = 50.2 Å, c = 29.9 Å, α = 90 o , β = 90 o , γ = 120 o , and the diffraction peaks of powder X-ray diffraction at 2θ of 3.57°, 7.05°, 9.20° and 10.41° respectively correspond to the diffraction of crystal planes (110), (220), (222) and (330). Since there is no large-volume pillar [5]arene structure in the skeleton structure of TP-COF, the XRD diffraction experimental results show that it adopts the AA stacking mode. After refinement and simulation, it is obtained that TP-COF belongs to the PM symmetry group, and the unit cell parameters are a = 52.2 Å, b = 3.5 Å, c = 51.9 Å, α = 90 o , β = 60 o , γ = 90 o .

[0038] 77 K Nitrogen Isothermal Adsorption Test of P5-COF The 77 K nitrogen isothermal adsorption experiment test was carried out on the pillar [5]arene covalent organic framework material P5-COF prepared in Example 1. The specific steps are as follows: Accurately weigh 100 mg of purified P5-COF, heat it up to 120 °C at a rate of 10 °C / min in a degassing station under a vacuum of 5~10 mmHg column for 120 min, and then test the isothermal adsorption curve of the material for nitrogen at 77 K on a Micromeritics ASAP 2020 PLUS gas sorption analyzer. The results are as Figure 4 shown.

[0039] As can be seen from Figure 4 , the specific surface area of P5-COF is 214 m 2 / g. The relatively small specific surface area may be caused by the periodic pore size in the northern part being blocked due to the ABC three-layer staggered stacking. Using non-local density functional theory to simulate and calculate the pore size of the structure, it is obtained that the pore size distribution of this framework structure is between 1.78 nm and 4.77 nm, corresponding to the pore size separated by ABC stacking and the pore size of the undivided periodic arrangement of the structure respectively.

[0040] Scanning Electron Microscopy and Transmission Electron Microscopy Tests of P5-COF The pillar[5]arene covalent organic framework material P5-COF prepared in Example 1 was subjected to scanning electron microscopy and transmission electron microscopy tests, and the results are as Figures 5 - 6 shown.

[0041] As can be seen from Figure 5 , the scanning electron microscopy (SEM) test shows that P5-COF has a uniform spherical morphology, and the elemental distribution analysis shows that C, N, and O elements are uniformly distributed throughout the microstructure. And Figure 6 the transmission electron microscopy (TEM) can directly observe the successful formation of the crystalline nanosheet structure, and regular lattice fringes can be found in the high-resolution TEM image, with a lattice spacing of about 0.43 nm.

[0042] 5 CO2 Adsorption Tests of P5-COF The pillar[5]arene covalent organic framework material P5-COF prepared in Example 1 was subjected to CO2 adsorption tests under standard atmospheric pressure and different temperature conditions (298 K and 195 K). The specific steps are as follows: Accurately weigh 100 mg of purified P5-COF, heat it to 120 °C at a rate of 10 °C / min in a degassing station under a vacuum of 5-10 mmHg for 120 min, and then test the isothermal adsorption curves of the material for CO2 at 195 K and 298 K on a Micromeritics ASAP 2020 PLUS gas adsorption instrument. The results are as Figure 7 shown.

[0043] Figure 7 The results show that the CO2 adsorption capacities of P5-COF at 195 K and 298 K are 94 cm 3 / g and 11 cm 3 / g respectively, and it has good CO2 adsorption performance, which is due to the fact that the P5-COF structure contains a large number of periodically arranged pyridine units as Lewis base sites.

[0044] 6 Thermal Stability Tests of P5-COF The thermal stability of the pillar[5]arene covalent organic framework material P5-COF prepared in Example 1 was tested by thermogravimetric analysis (TGA), and the results are as Figure 8 shown. As can be seen from Figure 8 , the thermal decomposition temperature of P5-COF is as high as 388 °C, indicating good thermal stability.

[0045] Experimental Example 2 Influence of Reaction Conditions of the Material Catalyzed CO2 and Epoxide Addition Reaction on the Catalytic Effect The pillar[5]arene covalent organic framework material P5-COF prepared in Example 1 and the covalent organic framework material TP-COF prepared in Comparative Example 1 were used as catalytic aids, respectively, to synergistically catalyze the addition reaction of CO2 and epoxide with a cationic organic catalyst to prepare cyclic carbonate. The specific process was as follows: The cationic organic catalyst Cat. 1, the catalytic aid (P5-COF or TP-COF), and 5 mmol of epichlorohydrin were added to a 10 mL Schlenk tube. After evacuating the air in the Schlenk tube under liquid nitrogen freezing, CO2 with a volume concentration of 100% (1 atm at normal pressure) was introduced into the reaction mixture, and the reaction mixture was stirred; after the reaction was completed, the insoluble catalyst was removed by filtration, the filtrate was extracted and separated with CDCl3 / H2O, the organic phase was collected and dried over anhydrous Na2SO4, and 1,1,2,2-tetrachloroethane was used as an internal standard. 1 1H NMR was used to analyze and quantify the conversion rate of epichlorohydrin and the yield of the corresponding cyclic carbonate. The synthesis route was as follows: ; among them, the cationic organic catalyst Cat. 1 was . The catalytic effects under different reaction conditions are shown in Table 1.

[0046] Table 1 Catalytic effects under different reaction conditions

[0047] It can be seen from Items 1-5 in Table 1 that P5-COF can be used as a catalytic aid in combination with Cat. 1 to efficiently catalyze the target reaction. When the dosage of Cat. 1 is 1-fold equivalent of the molar number of pillar[5]arene in the P5-COF structure, the yield is 87%; when the dosage of Cat. 1 is 2-fold equivalent of the molar number of pillar[5]arene in the P5-COF structure, it is the optimal, and the yield reaches 99%. Only using Cat. 1 to catalyze the reaction has a yield of only 78% under the same conditions. Using TP-COF without the pillar[5]arene structural unit for catalysis cannot achieve the optimal effect, indicating the importance of the pillar[5]arene structural unit. It can be seen from Item 1 and Items 6-10 in Table 1 that the optimal reaction temperature is 80 °C, and the reaction time requires 12 h to complete the target reaction.

[0048] At the same time, as Figure 9 shown, during the separation process of the cyclic carbonate product prepared in Item 2 of Table 1, it was found that the product only needed a simple filtration and extraction in one step to obtain a cyclic carbonate product with a purity > 98%, without column chromatography separation, and had the characteristics of convenient operation and easy separation.

[0049] Experimental Example 3: Study on the Substrate Expansion of the Cycloaddition Reaction of CO2 and Epoxides Catalyzed by P5-COF and Imidazolium Salt Cationic Organic Catalysts The column [5] arene covalent organic framework material P5-COF prepared in Example 1 was used in combination with an imidazolium salt cationic organic catalyst to catalyze the addition reaction of CO2 and epoxides to prepare cyclic carbonates. The specific process is as follows: The imidazolium salt cationic organic catalyst Cat. 1 (0.36 mol%), 10 mg of P5-COF, and 5 mmol of epoxide were added to a 10 mL Schlenk tube. After evacuating the air in the Schlenk tube under liquid nitrogen freezing, CO2 with a volume concentration of 100% (atmospheric pressure, 1 atm) was introduced into the reaction mixture, and the reaction mixture was stirred; after the reaction was completed, the insoluble catalyst was removed by filtration, the filtrate was extracted and separated with CDCl3 / H2O, the organic phase was collected and dried over anhydrous Na2SO4, and 1,1,2,2-tetrachloroethane was used as an internal standard, and 1 1H NMR was used to analyze and quantify the yields of the corresponding cyclic carbonates of different epoxides; The synthesis route is as follows: or ; among them, the imidazolium salt cationic organic catalyst Cat. 1 is . The results of the reaction substrates, products, and catalytic effects are shown in Table 2.

[0050] Table 2 Catalytic Effects of P5-COF on Different Reaction Substrates

[0051] Table 2 investigated the generality of the catalytic auxiliary in the preparation of synthetically important cyclic carbonates. It can be seen from Table 2 that under the optimized reaction conditions, all epoxides can participate in the cycloaddition reaction of pure CO2 at 80 °C or 100 °C within 12 h or 24 h; in items 1-9 in Table 2, the epoxides have relatively high or medium reaction activities, and excellent yields (95% - 99%) can be obtained under the co-catalysis of P5-COF and Cat.1. At the same time, to test the catalytic limit of the combined action of P5-COF and Cat. 1, two substrates with high difficulty, item 10 (resorcinol diglycidyl ether diepoxide) and item 9 (cyclohexene oxide), were selected for the reaction. The results showed that although the reaction time was extended to 24 h at 100 °C and the yields were relatively low (66% and 21% respectively), which may be due to steric hindrance and electronic substituent effects, the catalysis of high-difficulty substrates could still be achieved.

[0052] Experimental Example 4: Analysis of the Catalytic Performance of P5-COF in Improving the Cycloaddition Reaction of CO2 and Epoxides Catalyzed by Different Cationic Organic Catalysts The pillar[5]arene covalent organic framework material P5-COF prepared in Example 1 and the covalent organic framework material TP-COF prepared in Comparative Example 1 were respectively synergistically combined with a cationic organic catalyst, or the cationic organic catalyst alone was used to catalyze the addition reaction of CO2 and epoxide to prepare cyclic carbonate. The specific process is as follows: Add the cationic organic catalysts Cat. 1-4 (0.36 mol%), 10 mg of P5-COF and 5 mmol of epichlorohydrin into a 10 mL Schlenk tube. After evacuating the air in the Schlenk tube under liquid nitrogen freezing, introduce CO2 with different volume concentrations (atmospheric pressure, 1 atm) into the reaction mixture, and stir the reaction mixture at 80 °C for 12 h; after the reaction is completed, filter to remove the insoluble catalyst, extract and separate the filtrate with CDCl3 / H2O, collect the organic phase, dry it with anhydrous Na2SO4, and use 1 1H NMR to analyze and quantify the conversion rate of epichlorohydrin and the yield of the corresponding cyclic carbonate; The synthesis route is as follows: ; among them, the imidazolium salt cationic organic catalyst Cat. 1 is 、the imidazolium salt cationic organic catalyst Cat. 2 is 、the quaternary ammonium salt cationic organic catalyst Cat. 3 is 、the pyridinium salt cationic organic catalyst Cat. 4 is . The results are as Figure 10 shown.

[0053] It can be seen from Figure 10 that P5-COF has a good activity enhancement effect on the three types of cationic organic catalysts, namely imidazolium salts, quaternary ammonium salts and pyridinium salts, and can be used as a general catalytic assistant for the cationic organic catalytic CO2 cycloaddition reaction. Figure 10 Figure (a) in it shows the catalytic results of the reaction of pure CO2 gas (volume concentration of 100%) with epichlorohydrin. If only Cat. 1-4 are used, the reaction yields are distributed in the range of 70% - 85%. When adding the auxiliary agent TP-COF (without pillar[5]arene unit in the structure, Comparative Example 1), the yields are slightly improved and distributed in the range of 85% - 89%; this may be due to the promotion of mass transfer by the periodic framework structure; when adding P5-COF as the auxiliary agent, the yields are increased to 96% - 99%; from Figure 10As can be seen from Figure (b) in the middle, the promotion effect and law of the P5-COF additive of the present invention are more obvious in the catalytic results of the reaction of low-concentration CO2 gas with epichlorohydrin; when the P5-COF additive is not used or the TP-COF additive is used, the yield distributions are 36% - 59% and 44% - 68% respectively, and when an equivalent amount of P5-COF is used as the additive, the yield distribution is 90% - 95%.

[0054] Experimental Example 5 Substrate Expansion Study on the Cycloaddition Reaction of P5-COF and Pyridinium Cationic Organic Catalyst Catalyzing 15% CO2 by Volume with Epoxides The pillar[5]arene covalent organic framework material P5-COF prepared in Example 1 was used in combination with a pyridinium cationic organic catalyst to catalyze the addition reaction of 15% CO2 by volume with epoxides to prepare cyclic carbonates. The specific process is as follows: The pyridinium cationic organic catalyst Cat. 4 (0.36 mol%), 10 mg of P5-COF, and 5 mmol of epoxide were added to a 10 mL Schlenk tube. After evacuating the air in the Schlenk tube under liquid nitrogen freezing, a CO2 gas with a volume concentration of 15% (CO2 / N2 = 15 / 85, v / v, 1 atm) was introduced into the reaction mixture, and the reaction mixture was stirred; after the reaction was completed, the insoluble catalyst was removed by filtration, the filtrate was extracted and separated with CDCl3 / H2O, the organic phase was collected and dried over anhydrous Na2SO4, and 1,1,2,2-tetrachloroethane was used as the internal standard. 1 1H NMR was used to analyze and quantify the yields of the corresponding cyclic carbonates of different epoxides. The synthesis route is as follows: ; among them, the pyridinium cationic organic catalyst Cat. 4 is . The results of the reaction substrates, products, and catalytic effects are shown in Table 3.

[0055] Table 3 Catalytic Effects of P5-COF on Different Reaction Substrates

[0056] From the results in Table 3, it can be seen that the crystalline pillar[5]arene covalent organic framework material P5-COF prepared in the present invention has universality in enhancing the activity of catalysts with host-guest recognition ability, and is also applicable to simulated syngas with a CO2 concentration as low as 15% by volume, showing high activity in combination with small molecule catalysts.

[0057] Experimental Example 6 Recycling of P5-COF and Evaluation of Its Catalytic Activity The cyclic recycling and catalytic activity evaluation of the pillar[5]arene covalent organic framework material P5-COF prepared in Example 1 were carried out as follows: After the reaction was completed, the reaction solution was cooled to room temperature, centrifuged at 2000 r / min for 3 min, and then filtered to remove P5-COF. The removed P5-COF was ultrasonically washed with dichloromethane and methanol for 15 min, filtered and collected, and then activated at 45 °C under vacuum for 12 h to be reused. The catalytic efficiency results of the target compound after 10 times of reuse are as Figure 11 shown.

[0058] As can be seen Figure 11 from it, the pillar[5]arene covalent organic framework material prepared in the present invention can be recycled at least 10 times without obvious decrease in activity, and has good stability.

[0059] From the above analysis, it can be seen that the pillar[5]arene covalent organic framework material of the present invention acts mainly through the following two mechanisms: (1) Host-guest interaction "anchors" small molecule organic small molecule catalysts cations in the confined framework pores, enhancing the nucleophilicity of anions-cations (such as Br - ); (2) A dense ABC three-layer stacking structure is formed, and the pyridine units in the structure promote the reversible adsorption and molecular mass transfer of CO2 gas, realizing the improvement and enhancement of the catalytic performance of traditional organic small molecule catalysts, including imidazolium salts, quaternary ammonium salts, and pyridinium salts. This crystalline pillar[5]arene covalent organic framework material not only has universality for improving the activity of catalysts with host-guest recognition ability, but also is applicable to CO2 simulated syngas with a volume concentration as low as 15%. After the reaction is completed, a cyclic carbonate product with a purity > 98% can be separated by a simple filtration and extraction in one step, without cumbersome separation and purification means such as column chromatography. The recovered covalent organic framework material has no obvious attenuation in catalytic performance after 10 catalytic cycles.

[0060] The present invention has been described according to the above embodiments. It should be understood that the above embodiments do not limit the present invention in any form. All technical solutions obtained by using equivalent replacement or equivalent transformation fall within the scope of the present invention.

Claims

1. A pillar[5]arene covalent organic framework material, characterized in that: The pillar [5] aromatic covalent organic framework material has a structure as shown in Formula I: 。 2. The method for preparing the pillar[5]arene covalent organic framework material according to claim 1, characterized in that: The following steps are involved: 4,4',4''-(pyridine-2,4,6-triyl) tribenzaldehyde and column[5]arene diamine monomer are dissolved in a solvent and subjected to condensation reaction under the action of a catalyst to obtain a column[5]arene covalent organic framework material as shown in Formula I. The synthesis route is as follows: 。 3. The method for preparing the pillar [5] aromatic covalent organic framework material according to claim 2, characterized in that: The solvent is a mixed solution of mesitylene and 1,4-dioxane; the catalyst is an aqueous solution of acetic acid; the molar ratio of the 4,4',4''-(pyridine-2,4,6-triyl)tribenzaldehyde and column [5] aromatic diamine monomer is (0.2-0.3):(0.3-0.4); the condensation reaction temperature is 100-130°C, and the reaction time is 68-74 h.

4. The method for preparing the pillar [5] aromatic covalent organic framework material according to claim 3, characterized in that: The volume ratio of mesitylene to 1,4-dioxane in the mixed solution is (8-9):(1-2); the molar concentration of the acetic acid aqueous solution is 5-7 M; and the volume ratio of the mixed solution to the acetic acid aqueous solution is (40-60):

1.

5. Use of the pillar [5] aromatic covalent organic framework material according to claim 1 in catalyzing the addition reaction of CO2 and epoxide to prepare cyclic carbonate.

6. The use according to claim 5, characterized in that The pillar[5]arene covalent organic framework material cooperates with a cationic organic catalyst to catalyze the addition reaction of CO2 and epoxide to prepare cyclic carbonate.

7. The use according to claim 6, characterized in that The cationic organic catalyst is an imidazole salt, a quaternary ammonium salt or a pyridinium salt; the epoxide has a structure as shown in Formula II or Formula III: Where: R1 or R2 are both halogenated alkyl, C 1-20 Straight-chain or branched alkyl, cycloalkyl, alkenyl, aromatic or arylalkyl.

8. The use according to claim 7, characterized in that The cationic organic catalyst is , , or .

9. The use according to claim 7, characterized in that The specific structural formula of the epoxide is as follows: , , , , , , , , , or .

10. The use according to claim 6, characterized in that The molar ratio of the column [5] aromatic unit to the cationic organic catalyst in the column [5] aromatic covalent organic framework material is 1: (1-2); the temperature of the addition reaction is 60-100° C., and the time is 6-24 h.

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