A carboxyl-functionalized hypercrosslinked polymer, its preparation method and application

Abstract

This invention belongs to the field of organic porous materials, specifically relating to a carboxyl-functionalized hypercrosslinked polymer, its preparation method, and its applications in CO2 capture and separation, H2 adsorption, and CH4 storage. This invention uses carboxyl-rich small organic molecules as monomers, dichloromethane as a solvent and external crosslinking agent, and anhydrous aluminum chloride as a catalyst to directly prepare a carboxyl-functionalized porous hypercrosslinked polymer under mild conditions via Friedel-Crafts alkylation. The resulting functionalized hypercrosslinked polymer exhibits high BET and Langmuir surface areas, good CO2 capture and separation performance, and excellent H2 adsorption and CH4 storage capabilities. By adjusting the length of the carboxylic acid branches, this invention can effectively alter the molecular structure of the monomers and facilitates the dual regulation of the porous structure and CO2 capture performance of the hypercrosslinked polymer.

Description

Technical Field

[0001] This invention belongs to the field of organic porous materials, and relates to a carboxyl-functionalized hypercrosslinked polymer, its preparation method, and its application. Background Technology

[0002] The ever-increasing concentration of CO2 in the atmosphere exacerbates extreme weather phenomena such as global glacial melting, ocean acidification, sea-level rise, floods, and tsunamis. Over the past few decades, a series of materials for efficient CO2 capture have flourished, including traditional solid porous materials such as zeolites, clays, activated carbon, carbon nanotubes, and metal oxides, as well as novel solid porous materials such as metal-organic frameworks, hypercrosslinked polymers, conjugated microporous polymers, covalent organic networks, self-contained microporous polymers, and aromatic ring framework networks. Among these, hypercrosslinked polymers can be prepared on a large scale through Friedel-Crafts reactions under mild conditions. Due to their wide availability of monomer sources, inexpensive catalysts, effective synthesis strategies, high BET specific surface area, narrow pore size and pore size distribution, good thermal stability, and diverse functional groups, hypercrosslinked polymers exhibit high CO2 adsorption performance and show excellent application prospects in the field of CO2 capture and separation.

[0003] Functionalized hypercrosslinked polymers, by modulating the interactions between the polymer framework and guest molecules, contribute to improved CO2 capture and separation performance, and have become a research focus in recent years. Based on this, functionalized monomers rich in different types and quantities of heteroatoms such as nitrogen, oxygen, sulfur, and silicon atoms, as well as various electron-donating functional groups such as phenyl, naphthyl, hydroxyl, and amino groups, have been directly used to weave high-performance functionalized hypercrosslinked polymers. For example, a high BET specific surface area of ​​1688 m²... 2 g -1The polycarbazole HC-PCz-8 can adsorb 15.6 wt% CO2 at 298 K / 1.00 bar. The nitrogen-rich pyrrole polymer Py-1 achieves a CO2 / N2 adsorption selectivity of approximately 117 at 273 K. However, for functionalized monomer molecules modified with electron-withdrawing groups, the electron-withdrawing groups in their structure reduce the molecular reactivity, hindering the preparation of functionalized hypercrosslinked polymers. Post-synthetic modification is an effective method to introduce a variety of electron-withdrawing groups, such as carboxyl, carbonyl, fluorine, and sulfonic acid groups, into the polymer material backbone. Through hydrogen bonding, electrostatic interactions, acid-base interactions, van der Waals interactions, dipole-dipole interactions, and dipole-quadipole interactions, the CO2 adsorption and separation performance of the material can be effectively improved. For example, using a post-synthetic fluorination strategy, the CO2 adsorption capacity of polymer SC-TPB at 298 K / 1.00 bar can be increased from 10.56 wt% to 13.20 wt%. Post-synthetic sulfonation modification can also improve the CO2 / N2 adsorption selectivity of polymer MeBP at 298 K from 10.6 to 12.4. It is worth noting that compared with directly using functionalized building blocks to weave functionalized hypercrosslinked polymer materials, post-synthetic modification methods typically involve a large number of precious metal catalysts, harmful reagents, harsh reaction conditions, energy waste, complex experimental procedures, and even serious pollution, making the weaving of ideal hypercrosslinked polymers more cumbersome and time-consuming. To better advance academic research and industrial applications, the simple and efficient preparation of functionalized hypercrosslinked polymers with electron-withdrawing group modification, high BET specific surface area, and hierarchical porous structure based on functionalized building blocks under mild conditions for efficient CO2 gas capture and separation has become an important issue that urgently needs to be addressed.

[0004] Designing and constructing the monomer molecular structure is often a necessary step in preparing ideal hypercrosslinked polymers. Carboxyl groups, as polar electron-withdrawing groups, can effectively disperse CO2 molecules and exhibit good CO2 solubility. Furthermore, the quadrupole nature of CO2 molecules can significantly enhance the interaction between carboxyl groups and CO2 molecules, thus helping to improve the CO2 adsorption performance of carboxyl-based materials. Based on this, carboxyl groups can be considered a suitable potential electron-withdrawing group for functionalizing hypercrosslinked polymers. Meanwhile, theoretical simulations show that introducing electron-rich groups into the monomer molecules can improve their reactivity and facilitate the preparation of porous organic materials. Fluorene and its derivatives possess numerous reactive sites and electron-rich properties, actively participating in polymerization reactions and finding wide applications in optoelectronic devices, organic semiconductor photocatalysis, environmental monitoring, and biodiagnostics. They can serve as suitable electron-donating counterparts for electron-withdrawing groups. Therefore, it is easy to infer that a good combination of carboxyl groups and fluorene derivatives will help achieve an electronic balance between the electron-withdrawing and electron-donating ends within the monomer molecules, thereby facilitating the direct preparation of functionalized hypercrosslinked polymers modified with electron-withdrawing groups, aiming to achieve efficient CO2 gas capture and separation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a series of novel hypercrosslinked polymers with electron-withdrawing functionalization, high specific surface area, and diverse structures, prepared from carboxyl-rich organic small molecules. These polymers are then applied to the efficient capture and separation of CO2 gas, H2 adsorption, and CH4 storage. The invention also demonstrates the feasibility of directly weaving various carboxyl-functionalized hypercrosslinked polymers with high BET specific surface area and good gas adsorption performance based on commonly used Friedel-Crafts alkylation reactions and suitable building monomers.

[0006] Based on this, the present invention provides a simple, efficient and direct one-step preparation strategy for carboxyl-functionalized hypercrosslinked microporous organic polymers and their applications in CO2 gas adsorption and separation, H2 adsorption and CH4 storage, especially the study on the influence of carboxylic acid side chains of different lengths and structures in the monomers on the porosity and CO2 gas adsorption performance of the hypercrosslinked organic polymers based on them.

[0007] Specifically, under anhydrous aluminum chloride catalysis, inexpensive and readily available carboxyl organic small molecules are used to weave novel functionalized hypercrosslinked organic polymers through Friedel-Crafts alkylation under mild conditions. Compared with traditional post-synthetic modification methods, which suffer from low yields, complex operations, harsh reaction conditions, poor safety, and often involve flammable and explosive hazardous chemicals or reagents with high toxicity, this method offers advantages such as mild reaction conditions, high yields, simple operation, good safety, and ease of large-scale production when preparing electron-withdrawing functionalized hypercrosslinked polymers.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A carboxyl-functionalized hypercrosslinked polymer, wherein the hypercrosslinked polymer is woven from small organic molecules rich in carboxyl functional groups as building monomers via Friedel-Crafts alkylation reaction, and its general structural formula is:

[0010]

[0011] Where R = -CH2COOH, -CH2OCONHCH2COOH or -CH2O(CONHCH2)4COOH, and n is the degree of polymerization;

[0012] For soluble polymers, the degree of polymerization "n" can usually be determined relatively easily. However, in this invention, the hypercrosslinked polymer is mainly prepared using dichloromethane as the external crosslinking agent. Under mild conditions, it is formed by bridging 9-fluoreneacetic acid, N-fluorenemethoxycarbonyl-glycine, or N-fluorenemethoxycarbonyl-glycylglycine molecules with carbon-carbon single bonds and then condensing a small molecule of hydrogen chloride. Because carbon-carbon single bonds have high bond energies and are not easily broken, the woven hypercrosslinked organic polymer cannot dissolve in any common organic solvents, including those with good solubility such as benzene, toluene, chloroform, ethyl acetate, tetrahydrofuran, dimethyl sulfoxide, N-methylpyrrolidone, 1,2-dichloroethane, N,N-dimethylformamide, and N,N-dimethylacetamide, as clearly documented in relevant literature. Therefore, based on current chemical characterization methods and testing instruments, it is not possible to accurately give any value or range for the degree of polymerization "n".

[0013] The present invention also provides a method for preparing the above-mentioned carboxyl-functionalized hypercrosslinked polymer. Under Lewis acid catalyst conditions (preferably anhydrous aluminum chloride), a carboxyl-rich organic small molecule is selected as the building monomer, and an organic solvent is used as both the solvent and the external crosslinking agent. The carboxyl-functionalized hypercrosslinked polymer is synthesized through a Friedel-Crafts alkylation reaction.

[0014] Furthermore, the carboxyl-rich organic small molecule is 9-fluorenacetic acid, N-fluorenmethoxycarbonyl-glycine, or N-fluorenmethoxycarbonyl-glycylglycylglycine.

[0015] Furthermore, the specific steps of the preparation method are as follows:

[0016] In a nitrogen atmosphere, carboxyl-rich small organic molecules are dissolved in an organic solvent (preferably dichloromethane). After thorough stirring, a Lewis acid catalyst is immediately added, and the reaction is carried out at 20°C for 4 hours. Then, the temperature is raised to 30°C for 8 hours, then to 40°C for 12 hours, then to 60°C for 12 hours, and finally to 80°C for 24 hours. After the reaction is completed, the reaction is quenched (preferably with HCl-H2O at a volume ratio of 2:1). The precipitate is filtered, washed, and then extracted with anhydrous ethanol using a Soxhlet extractor for 48 hours. Finally, the precipitate is dried to constant weight in a vacuum drying oven at 70°C to obtain a carboxyl-functionalized hypercrosslinked polymer.

[0017] Furthermore, the present invention also provides the application of the above-mentioned carboxyl-functionalized hypercrosslinked polymers in CO2 capture and separation, H2 adsorption and CH4 storage.

[0018] Furthermore, to strongly demonstrate that introducing electron-withdrawing carboxyl groups into the building monomers not only helps improve the porosity of the woven polymer but also enhances its gas adsorption performance and CO2 adsorption heat, this invention also provides a hypercrosslinked organic polymer prepared using fluorene as the polymerizing monomer and employing a synthesis method similar to that of the three carboxyl-functionalized polymer materials. The invention includes the N2 adsorption-desorption curves at 77.3 K / 1.00 bar, pore size and pore size distribution, CO2 gas adsorption performance at 273.15 K / 1.00 bar and 298.15 K / 1.00 bar, and the CO2 adsorption heat Q obtained based on the CO2 gas adsorption curves at 273.15 K / 1.00 bar and 298.15 K / 1.00 bar. st .

[0019] This invention was completed with the support of the National Natural Science Foundation of China (Youth Project, No. 22005349), the Hubei Provincial Natural Science Foundation (General Project, No. 2023AFB840), the Fundamental Research Funds for the Central Universities (No. CZQ23003), industry-funded projects (No. HZY23115, HZY23116, HZY23117, HZY23118, HZY23119, HZY23120), and the Fundamental Research Funds for the Central Universities (No. CZQ21009).

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] 1. This invention enables the direct and efficient preparation of carboxyl-functionalized hypercrosslinked polymers based on carboxylated small organic molecules with different structures and a simple one-step Friedel-Crafts alkylation reaction under mild conditions. Moreover, the polymer materials are inexpensive and easy to mass-produce, possessing significant theoretical research and industrial application value.

[0022] 2. The carboxyl-functionalized hypercrosslinked polymer prepared by this invention has a high BET specific surface area, narrow pore size and pore size distribution, hierarchical pore structure, and microporous structure that is particularly helpful in improving CO2 adsorption performance. It also has good CO2 capture, H2 adsorption, CH4 storage performance and CO2 / N2 separation performance. Furthermore, its porosity and CO2 adsorption performance can be dually regulated by adjusting the length of the carboxyl branch chain, i.e., regulating the molecular structure of the monomer. Attached Figure Description

[0023] Figure 1This is a schematic diagram illustrating the synthesis of the carboxyl-functionalized hypercrosslinked polymer of the present invention. As shown in the figure, using carboxyl-rich fluorene derivatives such as 9-fluoreneacetic acid (FAA), N-fluorenemethoxycarbonyl-glycine (FCG), and N-fluorenemethoxycarbonyl-glycylglycine (FGG) as building monomers, a series of novel carboxyl-functionalized hypercrosslinked polymers can be woven based on Friedel-Crafts alkylation reactions under mild conditions.

[0024] Figure 2 The infrared spectra of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 are shown. As can be seen from the figures, at 3100 cm⁻¹... -1 Up to 3000cm -1 The absorption peaks within this range are attributed to the CH stretching vibration on the benzene ring. (1600 cm⁻¹) -1 and 1443cm -1 The nearby absorption peak is attributed to the C=C stretching vibration on the benzene ring. (1627 cm⁻¹) -1 1520cm -1 and 1349cm -1 The nearby absorption peak is attributed to the -CO-NH- stretching vibration. (1730 cm⁻¹) -1 The nearby absorption peak is attributed to the C=O stretching vibration in the carboxyl group. 2920 cm⁻¹ -1 The nearby absorption peaks are attributed to the CH stretching vibration in the methylene group, indicating that novel carboxyl-functionalized hypercrosslinked polymers with diverse structures have been successfully synthesized by bridging fluorene derivatives with different structures with methylene groups.

[0025] Figure 3 The figures show the solid-state carbon spectra of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3. As can be seen from the figures, the carbon signals in the solid-state carbon spectra are mainly located at 130 ppm and 36 ppm. Specifically, the carbon signals near 130 ppm belong to unsubstituted carbon atoms in the monomer molecule, and the carbon signals near 36 ppm belong to carbon atoms in the methylene group. This strongly demonstrates that a series of carboxyl-functionalized hypercrosslinked polymers have been successfully fabricated using dichloromethane as the external crosslinking agent and three fluorene derivatives with different structures as building monomers.

[0026] Figure 4 Scanning electron microscopy (SEM) images of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3, wherein... Figure 4 (a) is polymer 1. Figure 4 (b) is polymer 2 and Figure 4 (c) is polymer 3. Scanning electron microscopy images show that the surface of the obtained carboxyl-functionalized hypercrosslinked polymer is relatively rough and is composed of irregularly stacked blocky solids of varying sizes.

[0027] Figure 5 Transmission electron microscopy (TEM) images of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3, wherein... Figure 5(a) is polymer 1. Figure 5 (b) is polymer 2 and Figure 5 (c) is polymer 3. Transmission electron microscopy images show that the obtained carboxyl-functionalized hypercrosslinked polymers are all amorphous structures.

[0028] Figure 6 Thermogravimetric curves of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 are shown in the figure. As can be seen from the figure, under a nitrogen atmosphere, with a heating rate of 10°C per hour from room temperature to 800°C, the temperatures at which the three functionalized hypercrosslinked polymers lost 5% of their mass were approximately 291°C, 299°C, and 229°C, respectively, and the temperatures at which they lost 10% of their mass were approximately 359°C, 345°C, and 272°C. When the temperature reached 800°C, the residual mass of the three polymer materials was approximately 1.75%, 4.55%, and 1.86% of their initial mass, respectively. Significant mass loss of the polymers only occurred at higher temperatures, indicating that the woven carboxyl-functionalized hypercrosslinked polymers possess good thermal stability.

[0029] Figure 7 (a) Nitrogen adsorption-desorption curves of carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 at 77.3 K / 1.00 bar. Figure 7 (b) The pore size and pore size distribution of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 are shown, with polymer 3, polymer 2, and polymer 1 from top to bottom. Figure 7 (a) It can be seen that the relatively steep nitrogen adsorption curve at lower pressures (P / P0 < 0.001) indicates the presence of abundant micropores in the polymer structure. The relatively obvious hysteresis loop between the nitrogen adsorption and desorption curves in the medium-pressure region indicates the presence of mesopores in the polymer structure. Figure 7 (b) It is known that the functionalized hypercrosslinked polymer structure has micropores with a size not exceeding 2 nm, including micropores with a pore size not exceeding 0.7 nm and mesopores with a size between 2 and 10 nm.

[0030] Figure 8 (a) CO2 adsorption-desorption curves of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 at 273.15 K / 1.00 bar. Figure 8 (b) CO2 adsorption-desorption curves of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 at 298.15 K / 1.00 bar. Figure 8 (c) shows the CO2 adsorption rate curves of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 under the conditions of 273.15 K / 0-1.00 bar. Figure 8 (d) shows the CO2 adsorption rate curves of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 under the conditions of 298.15 K / 0-1.00 bar. Figure 8(e) shows the CO2 adsorption heat curves of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3. Figure 8 (f) H2 adsorption-desorption curves of carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 at 77.3 K / 1.00 bar.

[0031] Figure 9 (a) N2 adsorption-desorption curves of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 at 273.15 K / 0.3 bar. Figure 9 (b) N2 adsorption-desorption curves of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 at 298.15 K / 0.3 bar. Figure 9 (c) CH4 adsorption-desorption curves of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 at 273.15 K / 1.00 bar. Figure 9 (d) CH4 adsorption-desorption curves of carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 at 298.15 K / 1.00 bar.

[0032] Figure 10 a, 10c, and 10e are the CO2 (●), N2 (▼), and CH4 (◆) adsorption curves of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 at 273.15 K / 0.3 bar. The CO2 / N2 and CO2 / CH4 adsorption selectivities were calculated using the Henry's Law initial slope method, where (a) represents polymer 1, (c) represents polymer 2, and (e) represents polymer 3. Figure 10 b, 10d, and 10f are CO2 (●), N2 (▼), and CH4 (◆) adsorption curves of the carboxyl-functionalized hypercrosslinked polymers prepared in Examples 1-3 at 298.15 K / 0.3 bar. The CO2 / N2 and CO2 / CH4 adsorption selectivity were calculated using the Henry's Law initial slope method. (b) represents polymer 1, (d) represents polymer 2, and (f) represents polymer 3.

[0033] Figure 11 (a) Nitrogen adsorption-desorption curves of the fluorene-based hypercrosslinked polymer prepared in Example 4 at 77.3 K / 1.00 bar. Figure 11 (b) The pore size and pore size distribution of the fluorene-based hypercrosslinked polymer prepared in Example 4.

[0034] Figure 12 (a) CO2 adsorption-desorption curves of the fluorene-based hypercrosslinked polymer prepared in Example 4 at 273.15 K / 1.00 bar. Figure 12 (b) CO2 adsorption-desorption curves of the fluorene-based hypercrosslinked polymer prepared in Example 4 at 298.15 K / 1.00 bar.

[0035] Figure 13The CO2 adsorption heat curve of the fluorene-based hypercrosslinked polymer prepared in Example 4 is shown. Detailed Implementation

[0036] The inventors will now provide a clear and complete description of the technical solutions of the present invention in conjunction with the embodiments and accompanying drawings. The described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0037] This invention uses infrared spectroscopy and solid-state carbon spectroscopy to determine the structural composition of carboxyl-functionalized hypercrosslinked polymers, elemental analysis to determine the elemental composition of carboxyl-functionalized hypercrosslinked polymers, thermogravimetric analysis to determine the thermal stability of carboxyl-functionalized hypercrosslinked polymers, scanning electron microscopy to observe the surface morphology of carboxyl-functionalized hypercrosslinked polymers, transmission electron microscopy to observe the internal pore structure of carboxyl-functionalized hypercrosslinked polymers, and a specific surface area and pore size analyzer to determine the specific surface area, pore size, pore size distribution, and CO2, N2, H2, and CH4 adsorption performance of carboxyl-functionalized hypercrosslinked polymers. Based on the measured CO2, N2, H2, and CH4 adsorption curves, the CO2 / N2 and CO2 / CH4 adsorption selectivity at temperatures of 273.15 K and 298.15 K can be calculated.

[0038] The instruments used to characterize the product structure in the following examples are as follows: VERTEX 70 spectrometer, solid-state infrared spectrometer. 13 C10 spectrometer (WB 400MHz Bruker Avance II spectrometer), elemental analyzer (Vario Micro cube Elemental Analyzer), scanning electron microscope (FEI Sirion 200field-emission scanning electron microscope), transmission electron microscope (Tecnai G2 F30microscope), thermogravimetric analyzer (Perkin Elmer Instrument Pyris1 TGA), surface area analyzer (Micromeritics ASAP2460 surface area and porosity analyzer), adsorption curves for CO2, N2, H2 and CH4 (Micromeritics ASAP2020 surface area and porosity analyzer).

[0039] In the following embodiments, when weighing the corresponding mass of the building blocks, the weighing was carried out accurately based on the required molar amount and taking into account the purity of the purchased product.

[0040] Example 1:

[0041] The specific synthetic steps of a 9-fluoreneacetic acid-functionalized hypercrosslinked polymer are as follows:

[0042] Under a nitrogen atmosphere, 2.0 mmol of 9-fluoreneacetic acid (0.457 g) was added to a 100 mL single-necked flask containing 8 mL of dichloromethane and stirred thoroughly for 30 minutes. Immediately afterwards, 16 mmol of anhydrous aluminum chloride (2.136 g) was added. The mixture was reacted at 20 °C for 4 hours with vigorous stirring, then at 30 °C for 8 hours, then at 40 °C for 12 hours, then at 60 °C for 12 hours, and finally at 80 °C for 24 hours. After the reaction was complete, the mixture was quenched with 20 mL of HCl-H₂O (v / v = 2:1, using a mixture of 37 wt% concentrated hydrochloric acid and water at a volume ratio of 2:1, the same below), and the precipitate was filtered. The precipitate was then washed twice, successively with deionized water and anhydrous ethanol, and then extracted with anhydrous ethanol using a Soxhlet extract for 48 hours. Finally, the precipitate was dried in a vacuum drying oven at 70 °C for 48 hours to constant weight. The resulting polymer was a brown solid with a yield of approximately 120%, and was designated as Polymer 1. 13 C NMR (400MHz): 130ppm, 36ppm.

[0043] The structural formula of the carboxyl-functionalized hypercrosslinked polymer 1 obtained in this embodiment is:

[0044]

[0045] Example 2:

[0046] The specific synthetic steps of an N-fluorenemethoxycarbonyl-glycine-functionalized hypercrosslinked polymer are as follows:

[0047] Under a nitrogen atmosphere, 2.0 mmol of N-fluorenemethoxycarbonyl-glycine (0.606 g) was added to a 100 mL single-necked flask containing 8 mL of dichloromethane and stirred thoroughly for 30 minutes. Immediately afterwards, 16 mmol of anhydrous aluminum chloride (2.136 g) was added. The mixture was reacted at 20 °C for 4 hours with vigorous stirring, then at 30 °C for 8 hours, then at 40 °C for 12 hours, then at 60 °C for 12 hours, and finally at 80 °C for 24 hours. After the reaction was complete, the mixture was quenched with 20 mL of HCl-H₂O (v / v = 2:1), filtered to obtain a precipitate, washed twice each with deionized water and anhydrous ethanol, then extracted with anhydrous ethanol using a Soxhlet extracter for 48 hours, and finally dried in a vacuum oven at 70 °C for 48 hours to constant weight. The resulting polymer was a brown solid with a yield of approximately 125%, denoted as Polymer 2. 13C NMR (400MHz): 130ppm, 36ppm.

[0048] The structural formula of the carboxyl-functionalized hypercrosslinked polymer 2 obtained in this embodiment is:

[0049]

[0050] Example 3:

[0051] The specific synthetic steps of an N-fluorenemethoxycarbonyl-glycylglycylglycylglycine functionalized hypercrosslinked polymer are as follows:

[0052] Under a nitrogen atmosphere, 2.0 mmol of N-fluorenylmethoxycarbonyl-glycylglycylglycine (0.966 g) was added to a 100 mL single-necked flask containing 8 mL of dichloromethane and stirred thoroughly for 30 minutes. Immediately afterwards, 16 mmol of anhydrous aluminum chloride (2.136 g) was added. The mixture was reacted at 20 °C for 4 hours with vigorous stirring, then at 30 °C for 8 hours, then at 40 °C for 12 hours, then at 60 °C for 12 hours, and finally at 80 °C for 24 hours. After the reaction was complete, the mixture was quenched with 20 mL of HCl-H₂O (v / v = 2:1), filtered to obtain a precipitate, washed twice each with deionized water and anhydrous ethanol, then extracted with anhydrous ethanol using a Soxhlet extract for 48 hours, and finally dried in a vacuum oven at 70 °C for 48 hours to constant weight. The resulting polymer was a black solid with a yield of approximately 135%, and was designated as Polymer 3. 13 C NMR (400MHz): 130ppm, 36ppm.

[0053] The structural formula of the carboxyl-functionalized hypercrosslinked polymer 3 obtained in this embodiment is:

[0054]

[0055] Example 4:

[0056] The specific synthesis steps of a fluorene-based hypercrosslinked polymer are as follows:

[0057] Under a nitrogen atmosphere, 2.0 mmol of fluorene (0.339 g) was added to a 100 mL single-necked flask containing 8 mL of dichloromethane and stirred thoroughly for 30 minutes. Immediately afterwards, 16 mmol of anhydrous aluminum chloride (2.136 g) was added. The mixture was reacted at 20 °C for 4 hours with vigorous stirring, then at 30 °C for 8 hours, then at 40 °C for 12 hours, then at 60 °C for 12 hours, and finally at 80 °C for 24 hours. After the reaction was complete, the mixture was quenched with 20 mL of HCl-H₂O (v / v = 2:1), filtered to obtain a precipitate, washed twice each with deionized water and anhydrous ethanol, then extracted with anhydrous ethanol using a Soxhlet extract for 48 hours, and finally dried in a vacuum oven at 70 °C for 48 hours to constant weight. The resulting polymer was a black solid with a yield of approximately 138%.

[0058] The structural formula of the fluorene-based hypercrosslinked polymer obtained in this embodiment is:

[0059]

[0060] The yields of the polymers listed above are theoretical yields, calculated using the following formula:

[0061]

[0062] Wherein, m1(g) represents the mass of the polymer obtained after drying at 70°C for 48 hours in a vacuum drying oven, and m2(g) represents the mass of the building monomers 9-fluoreneacetic acid (FAA), N-fluorenemethoxycarbonyl-glycine (FCG) or N-fluorenemethoxycarbonyl-glycylglycine (FGG), and fluorene used.

[0063] Table 1 Elemental analysis of the building monomers and three polymers

[0064]

[0065] As shown in the table, compared to the C, H, O, and N element contents in the building blocks, the C and H element contents in the three corresponding polymers all increased, while the O and N element contents all decreased. This is mainly because the polymerization reaction uses dichloromethane as an external crosslinking agent, introducing methylene groups to bridge the monomer molecules to synthesize the polymer. Since methylene groups only contain C and H elements and not O and N elements, introducing a large number of methylene groups into the polymer framework structure leads to an increase in the C and H element contents and a decrease in the O and N element contents.

[0066] Because the polymer is insoluble, elemental analysis is used for detection. The content of different elements in the monomer molecule is a theoretical value, and its calculation formula is as follows:

[0067]

[0068] Where Mr(M) represents the relative molecular mass of the monomer molecule, n represents the number of atoms of one element in the monomer molecule, and Ar(N) represents the relative atomic mass of the corresponding element atom.

[0069] Table 2. Pore structure properties of novel carboxyl-functionalized hypercrosslinked polymers

[0070]

[0071] Table 3. CO2 and H2 adsorption properties and CO2 adsorption heat of novel carboxyl-functionalized hypercrosslinked polymers

[0072]

[0073] CO2 adsorption capacity. c The H2 adsorption at 77.3 K / 1.00 bar was determined using a Micromeritics ASAP 2020M analyzer. d The heat of CO2 adsorption was determined using a Micromeritics ASAP2020M analyzer based on the CO2 adsorption isotherms of polymer samples at 273.15 K and 298.15 K.

[0074]

[0075] Table 5. CO2 adsorption rate of polymer 2 at 273.15 K

[0076]

[0077]

[0078] Table 6. CO2 adsorption rate of polymer 3 at 273.15 K

[0079]

[0080]

[0081] Table 7 CO2 adsorption rate of polymer 1 at 298.15 K

[0082]

[0083]

[0084] Table 8. CO2 adsorption rate of polymer 2 at 298.15 K

[0085]

[0086] Table 9. CO2 adsorption rate of polymer 3 at 298.15 K

[0087]

[0088]

[0089] The CO2 adsorption rate is K(g·g) -1 min -1 ).

[0090] Table 10. N2 and CH4 adsorption properties of carboxyl-functionalized novel hypercrosslinked polymers

[0091]

[0092]

[0093] Table 11. CO2 / N2 and CO2 / CH4 adsorption selectivity of novel carboxyl-functionalized hypercrosslinked polymers

[0094]

[0095] Table 12 Porosity parameters and CO2 adsorption performance of fluorene-based hypercrosslinked polymers

[0096]

[0097] The above research results indicate that this invention directly prepares novel functionalized hypercrosslinked polymers with permanent microporous structures based on small organic molecules of carboxylic acids with different structures. Among them, the functionalized polymer based on N-fluorenemethoxycarbonyl-glycylglycylglycylglycine weaving has a BET specific surface area and Langmuir specific surface area as high as 1947 m². 2 ·g -1 and 2268m 2 ·g -1 Micropore area 1517m² 2 ·g -1 The largest micropore volume is 0.59 cm³. 3 ·g -1 Hole volume 0.88cm 3 ·g -1The CO2 adsorption capacity at 273.15 K / 1.00 bar was 20.03 wt%, the H2 adsorption capacity at 77.3 K / 1.00 bar was 2.05 wt%, and the CH4 adsorption capacity at 273.15 K / 1.00 bar was 2.10 wt%. Due to the abundance of carboxyl functional groups in the polymer structure, the polymer prepared based on N-fluorenemethoxycarbonyl-glycine showed CO2 / N2 and CO2 / CH4 separation performances at 273.15 K, calculated theoretically using Henry's Law initial slope method, as high as 33.17 and 6.29, respectively. Furthermore, by employing a side-chain engineering strategy and controlling the molecular structure of the monomers, the porosity and CO2 adsorption performance of the functionalized hypercrosslinked polymer can be effectively controlled. Moreover, with the increase of the length of the carboxyl branches (-CH2COOH, -CH2OCONHCH2COOH, -CH2O(CONHCH2)4COOH), the porosity and CO2 adsorption performance of the obtained functionalized hypercrosslinked polymer can be effectively improved. This is mainly because the chemical and packing structures of the building blocks are closely related to the porous structure of the polymer material; slight changes in the chemical and packing structures of the monomers can significantly affect the porosity of the polymer. For 9-fluoreneacetic acid, N-fluorenemethoxycarbonyl-glycine, and N-fluorenemethoxycarbonyl-glycylglycine, it is easy to see that these three monomers have similar molecular structures, differing primarily in their different carboxylic acid branches. Since carboxylic acid branches lack reactive sites, increasing the length of the carboxylic acid branches, while increasing the flexibility of the monomer molecule, is detrimental to improving the rigidity, BET specific surface area, and porosity of the polymer. As the length of the carboxylated branches increases, the conjugated electron-withdrawing effect of the carboxyl group on the fluorene group gradually weakens, and correspondingly, the electron-rich properties of the fluorene group gradually increase. Studies have shown that increasing the electron-rich properties of the building blocks is beneficial for weaving organic porous materials. From 9-fluoreneacetic acid to N-fluorenemethoxycarbonyl-glycine and N-fluorenemethoxycarbonyl-glycylglycylglycine, the electro-rich properties of the fluorene group in their structures gradually increase. This helps to continuously improve the porosity of the polymer by increasing the reactivity of the building monomers and the crosslinking density during polymerization, and by using external crosslinking agents to break down the chains of different polymer chains into smaller pores. Meanwhile, related studies have also strongly demonstrated that the pore structure parameters of polymers, such as BET specific surface area, pore size, pore size distribution, micropore volume, and pore volume, are closely related to their CO2 adsorption performance. Improving the pore structure parameters of polymers helps to enhance their CO2 adsorption performance. Therefore, by regulating the structure of carboxylated small organic molecules, the porosity and CO2 adsorption performance of the resulting polymer can be dually regulated. Furthermore, with the increase of the length of the carboxylated branched chains from 9-fluoreneacetic acid to N-fluorenemethoxycarbonyl-glycine and N-fluorenemethoxycarbonyl-glycylglycine, the porosity and CO2 adsorption performance of the resulting polymer can be gradually improved.

Claims

1. A carboxyl-functionalized hypercrosslinked polymer, wherein the hypercrosslinked polymer is prepared by Friedel-Crafts alkylation reaction using small organic molecules rich in carboxyl functional groups as building blocks, and its general structural formula is: in, R = -CH2COOH, -CH2OCONHCH2COOH or -CH2O(CONHCH2)4COOH, where n is the degree of polymerization.

2. A method for preparing the carboxyl-functionalized hypercrosslinked polymer of claim 1, specifically comprising: under Lewis acid catalyst conditions, selecting carboxyl-rich small organic molecules as building monomers, and using an organic solvent as both solvent and external crosslinking agent, and synthesizing the carboxyl-functionalized hypercrosslinked polymer through a Friedel-Crafts alkylation reaction; The carboxyl-rich organic small molecule is 9-fluorenacetic acid, N-fluorenmethoxycarbonyl-glycine or N-fluorenmethoxycarbonyl-glycylglycylglycine; The organic solvent is dichloromethane.

3. The preparation method according to claim 2, characterized in that, The specific steps are as follows: In a nitrogen atmosphere, carboxyl-rich small organic molecules were dissolved in an organic solvent and stirred thoroughly. Immediately after stirring, a Lewis acid catalyst was added, and the reaction was carried out at 20°C for 4 hours. Then, the temperature was raised to 30°C for 8 hours, then to 40°C for 12 hours, then to 60°C for 12 hours, and finally to 80°C for 24 hours. After the reaction was completed, the reaction was quenched, the precipitate was filtered, washed, and then extracted with anhydrous ethanol using a Soxhlet extractor for 48 hours. Finally, the product was dried in a vacuum drying oven at 70°C to constant weight to obtain a carboxyl-functionalized hypercrosslinked polymer.

4. The application of the carboxyl-functionalized hypercrosslinked polymer of claim 1 in CO2 capture and separation, H2 adsorption and CH4 storage.

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