A catalytically active hierarchical porous material, its preparation method and application

Abstract

This invention discloses a hierarchical porous material with catalytic activity, its preparation method, and its application. A photosensitive resin is obtained by stirring and reacting a halogen-containing photopolymerizable ionic liquid monomer, a photopolymerizable monomer, a multifunctional crosslinking agent, a non-reactive porogen, a photoinitiator, and a light absorber. The photosensitive resin is then placed in a 3D printing device to print a preform. The preform is placed in a supercritical drying device, where liquid CO2 is used as the medium for extraction and displacement. Subsequently, the temperature and pressure are increased to above the supercritical point of CO2, and the hierarchical porous material with catalytic activity is obtained through supercritical drying. This invention introduces highly nucleophilic halide ion sites and utilizes photopolymerization 3D printing and polymerization-induced phase separation technology to construct a hierarchical porous material that combines macroscopically customized flow channels with microscopically interconnected pores. This material, as a catalyst, can achieve highly efficient catalysis of the cycloaddition reaction of CO2 and epoxides under mild conditions.

Description

Technical Field

[0001] This invention belongs to the field of porous materials and catalysis technology, specifically relating to a hierarchical porous material with catalytic activity, its preparation method, and its application. Background Technology

[0002] Converting carbon dioxide (CO2) into high-value-added chemicals is one of the important ways to mitigate the greenhouse effect and achieve carbon emission reduction targets. Among the many conversion pathways, CO2 reacts with epoxides to form cyclic carbonates through cycloaddition reactions. Due to its 100% atom economy and the wide range of applications of the products in lithium battery electrolytes, polar solvents, and polymer intermediates, it has become a research hotspot in industry and academia.

[0003] Traditional CO2 cycloaddition reactions typically rely on homogeneous catalysts, such as organic bases, metal salts, or simple ionic liquids. While homogeneous catalysts exhibit high activity, they face significant challenges in practical applications, including difficulties in catalyst recovery, product separation, and environmental pollution. To address these issues, heterogeneous catalytic materials have emerged. Polyionic liquids (PILs), due to their integration of the catalytically active sites of ionic liquids with the structural stability of polymers and their excellent CO2 capture capabilities, are considered the most promising heterogeneous catalyst supports. However, existing PIL catalytic materials still face three major bottlenecks in practical applications:

[0004] First, there is a contradiction between mass transfer resistance and active site utilization. Polyionic liquids prepared by traditional bulk polymerization are often dense solids, with the catalytically active sites deeply embedded in the polymer matrix. CO2 and viscous epoxy compounds have difficulty penetrating in, resulting in extremely low apparent activity. Although this phenomenon can be improved by introducing porous structures, traditional template-based pore-forming methods are complex and cumbersome, and it is difficult to precisely control the macroscopic shape, making them unsuitable for the needs of industrial continuous flow reactors.

[0005] Second, the singularity of the catalytic mechanism leads to stringent reaction conditions. The key step in cycloaddition reactions lies in the ring-opening of epoxides. Early polyionic liquid systems mainly relied on the electrostatic interaction or hydrogen bonding of cations to adsorb CO2, lacking strong nucleophiles that could effectively attack the epoxide ring. This meant that the reaction usually needed to be carried out under high pressure (>2.0 MPa) and high temperature (>140 °C), which not only consumed a lot of energy but also easily led to the decomposition of heat-sensitive products.

[0006] Third, the lack of macroscopic strength and interlayer bonding. With the development of 3D printing technology, it has become possible to construct complex-shaped polyionic liquid parts using photopolymerization technology. However, for highly customized polyionic liquids, how to achieve a balance between high printing accuracy and high porosity remains a pressing problem to be solved. Summary of the Invention

[0007] The purpose of this invention is to overcome the low utilization rate of active sites and harsh reaction conditions of existing polyionic liquid catalysts in CO2 cycloaddition reactions, and to provide a hierarchical porous material with bifunctional catalytic activity, its preparation method, and its applications. This material introduces highly nucleophilic halide ion sites and utilizes photopolymerization 3D printing and polymerization-induced phase separation technology to construct an integral catalyst that combines macroscopically customized flow channels with microscopically interconnected pores, achieving highly efficient catalysis of the CO2 cycloaddition reaction with epoxides under mild conditions.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing a hierarchical porous material with catalytic activity includes the following steps:

[0010] (1) Preparation of photosensitive resin: Place halogen-containing photopolymerizable ionic liquid monomer, photopolymerizable monomer, multifunctional crosslinking agent, non-reactive porogen, photoinitiator and photoabsorber in a light-proof container, and stir in the dark for 5 to 120 min at a temperature of 25 to 80 °C to obtain a uniform and transparent photosensitive resin.

[0011] Furthermore, the weight parts of each raw material component of the photosensitive resin are as follows: 5-80 parts of halogen-containing photopolymerizable ionic liquid monomer, 0-60 parts of photopolymerizable monomer, 3-30 parts of multifunctional crosslinking agent, 15-70 parts of non-reactive porogen, 0.01-15 parts of photoinitiator, and 0-15 parts of light absorber.

[0012] Furthermore, the halogen-containing photopolymerizable ionic liquid monomer is at least one of a 1-vinyl type monomer 1 and an acrylate type monomer 1, with structural formulas shown in formulas (a) and (b), respectively, wherein R and R3 are alkyl segments, and X... - It consists of iodide ions, bromide ions, or chloride ions.

[0013]

[0014] Further, the photopolymerizable monomer (which may be an ionic liquid monomer or a nonionic liquid monomer) is at least one of 1-vinyl type monomer 2 (as shown in formula (c)), acrylate type 2 monomer (as shown in formula (d)), acrylate type 3 monomer (as shown in formula (e)), acrylamide or its derivative, and 4-acryloylmorpholine, wherein R, R1, and R2 are alkyl segments, and Z - It is one of nitrate ions, trifluoromethanesulfonylimide, tetrafluoroborate ions, and hexafluorophosphate ions.

[0015]

[0016] Further, the multifunctional crosslinking agent is at least one of the following: a difunctional acrylate monomer or its prepolymer, a trifunctional acrylate monomer or its prepolymer, or a tetrafunctional or higher acrylate monomer or its prepolymer. The structure of the difunctional acrylate monomer is shown in formula (f), wherein Y1 is selected from any one of alkylene, cycloalkylene, or aryl groups; or, Y1 is selected from any one of divalent organic groups containing an ether bond (-O-), an ester bond (-COO-), a urethane bond (-NHCOO-), or a carbonyl group.

[0017]

[0018] Preferably, the multifunctional crosslinking agent is at least one of 1,6-hexanediol diacrylate, ethylene glycol dimethacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, diethylene glycol diacrylate phthalate, tricyclodecanediethanol diacrylate, 1,4-butanediol diacrylate, 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate (such as PEG200DA, PEG400DA, PEG600DA), polypropylene glycol diacrylate, ethoxylated bisphenol A diacrylate, polytetramethylene glycol diacrylate, and ethoxylated 1,6-hexanediol diacrylate.

[0019] Further, the photoinitiator is selected from at least one of the following: diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), liquid form of TPO-L, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone (Irgacure 2959), 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651), benzophenone (BP), camphorquinone (CQ), Irgacure 184, Irgacure 2100, lithium phenyl-2,4,6-trimethylbenzoyl phosphite (LAP), and a vitamin B2 (riboflavin) and triethanolamine (TEOA) complex.

[0020] Furthermore, the light absorber is selected from light-absorbing dyes, which are used to reduce the characteristic penetration depth of the resin, reduce internal light scattering, and strictly limit the curing reaction to the vicinity of the focal plane, thereby significantly improving the Z-axis resolution of 3D printing.

[0021] Furthermore, the non-reactive porogen is selected from at least one of alcohols, ketones, esters, ethers, water, acetonitrile, and hexane; preferably at least one of ethanol, methanol, ethyl acetate, diethylene glycol dimethyl ether, and acetone.

[0022] (2) 3D printing molding and hierarchical porous construction

[0023] The photosensitive resin is placed in the material tank of the photopolymerization 3D printing equipment, and layer-by-layer curing and printing are performed according to the preset three-dimensional model with macroscopic flow channel characteristics. During the photoinitiated polymerization process, as the cross-linking density of the polymer network increases, the system undergoes polymerization-induced phase separation, and the porogen occupies in situ in the gaps of the polymer skeleton, resulting in a preform containing the porogen.

[0024] Furthermore, the 3D printing equipment is selected from one of the following: stereolithography (SLA), digital light processing (DLP), liquid crystal display mask (LCD), continuous liquid interface manufacturing (CLIP), two-photon polymerization (TPP), and volumetric additive manufacturing (VAM) equipment.

[0025] (3) Supercritical drying treatment

[0026] The preform is placed in a supercritical drying device and extracted and replaced with liquid CO2 as the medium. Then, the temperature and pressure are increased to above the supercritical point of CO2. By controlling the exhaust rate, the pore-forming agent and residual solvent are removed. Since the fluid has no surface tension in the supercritical state, the shrinkage and collapse of micropores during the drying process are effectively avoided. Finally, a hierarchical porous polyionic liquid material with macroscopic flow channels and micropores with catalytic activity is obtained.

[0027] Furthermore, based on the miscibility between the pore-forming agent and the CO2 medium, the specific process for step (3) is either treatment A or treatment B:

[0028] Treatment A (Direct Replacement Method): If the pore-forming agent (such as ethanol) is miscible with CO2, the above-mentioned preform is placed directly in a supercritical drying vessel, and liquid CO2 is introduced at -10~20°C and 1~10 MPa for solvent replacement for 3~10 h; then, the temperature is raised to 31~80 ℃ and the pressure is increased to 7.4~20 MPa to make the CO2 in the equipment reach a supercritical state; finally, the pressure is slowly released to atmospheric pressure at a depressurization rate of 0.01~0.1 MPa / min, and the sample is taken out.

[0029] Treatment B (Indirect Replacement Method): If the porogen has poor miscibility with CO2 (e.g., water, highly polar solvents), first immerse the preform in a transitional solvent miscible with CO2 (e.g., ethanol) for 10-36 hours, changing the solvent 1-3 times during this period. After the porogen in the preform is completely replaced, transfer it to a supercritical drying reactor and pass liquid CO2 through it at -10-20 °C and 1-10 MPa for solvent replacement for 3-10 hours. Then, raise the temperature to 31-80 °C and pressurize it to 7.4-20 MPa to bring the CO2 in the equipment to a supercritical state. Finally, slowly depressurize it to atmospheric pressure at a depressurization rate of 0.01-0.1 MPa / min and remove the sample.

[0030] This invention also provides the application of the aforementioned hierarchical porous polyionic liquid material with catalytic activity in the cycloaddition reaction of CO2 with epoxides:

[0031] A specific molar amount of epoxy compound and the prepared catalytically active hierarchical porous polyionic liquid material (as a solid-phase polyionic liquid catalyst) were placed together in a reaction vessel equipped with a reflux condenser. Under atmospheric pressure (0.1 MPa), high-purity CO2 gas was continuously introduced into the reaction system, magnetic stirring was activated, and the mixture was heated to 60–120 °C and reacted at a constant temperature for 6–12 hours. After the reaction was completed, the reaction solution was cooled to room temperature. Because the solid-phase polyionic liquid catalyst of this invention has a monolithic porous structure, efficient separation of the liquid-phase product (cyclic carbonate) from the solid-phase polyionic liquid catalyst can be achieved through simple centrifugation or filtration.

[0032] Furthermore, the epoxy compound is selected from at least one of epichlorohydrin, butyl glycidyl ether, allyl glycidyl ether, styrene oxide, 1,2-epoxyhexane, and glycidyl methacrylate.

[0033] Preferably, the solid-phase polyionic liquid catalyst obtained from the separation and recovery is washed several times alternately with anhydrous ethanol and deionized water to remove unreacted substrates and products adhering to the surface. It is then placed in a vacuum drying oven and dried under vacuum at 80–120 °C for 12–24 h. The dried catalyst is then directly added to the next cycloaddition reaction under the same conditions, and this process is repeated multiple times to examine the catalyst's cycle life and structural stability.

[0034] Product structure characterization and catalytic performance calculation. The chemical structure of the purified product was characterized using liquid nuclear magnetic resonance spectroscopy, with deuterated chloroform (CDCl3) as the test solvent. The catalytic performance indicators (conversion, selectivity, and yield) of the reaction were based on... 1 The integral area of ​​characteristic peaks in the H-NMR spectrum is calculated. The specific calculation formula is as follows:

[0035]

[0036]

[0037]

[0038] In the formula, C0 represents the molar concentration (mol / L) of the epoxide compound in the system at the initial reaction time (time 0); C t This represents the molar concentration (mol / L) of the residual epoxide in the system at time t during the reaction; C 环碳酸酯 This indicates the molar concentration (mol / L) of the cyclic carbonate product generated within a specified reaction time t.

[0039] This invention, employing the above technical solution, provides a hierarchical porous polyionic liquid material with bifunctional synergistic catalytic properties, which can serve as a solid-phase polyionic liquid catalyst. This invention precisely introduces strongly nucleophilic halide monomers into the polymer backbone and utilizes photopolymerization 3D printing technology combined with a polymerization-induced phase separation mechanism to construct a multi-level mass transfer network that combines macroscopically customized flow channels with microscopically interconnected pores. In this system, the cationic backbone of the polyionic liquid and the introduced halide anions constitute a highly efficient bifunctional catalytic center: the cationic or copolymeric components activate the epoxide compound through hydrogen bonding and provide CO2 adsorption sites, while the strongly nucleophilic halide ions effectively attack the epoxide ring, promoting its ring-opening. This synergistic catalytic effect significantly reduces the energy barrier of the cycloaddition reaction, enabling the material to achieve efficient conversion of epoxides under mild conditions of ambient pressure and relatively low temperature. Meanwhile, thanks to the monolithic structure formed by 3D printing and the hierarchical porous characteristics maintained by supercritical drying, this material not only solves the problem of the difficulty in recycling traditional powder catalysts, but also provides a monolithic catalytic material with precise and controllable structure, excellent catalytic performance and easy industrial recycling for the resource utilization of solid-phase polyionic liquid catalysts by significantly increasing the specific surface area and mass transfer rate.

[0040] Specifically, the present invention has the following beneficial effects:

[0041] (1) This invention ingeniously introduces functionalized monomers containing halogens (such as bromide ions and iodide ions) into a polyionic liquid network. The cations of the polyionic liquid and the copolymer components containing hydrogen bond donors can effectively adsorb CO2 and activate epoxides; while the strongly nucleophilic halogen anions (such as Br₂) can effectively adsorb CO2 and activate epoxides. -It can efficiently attack carbon atoms in epoxides with relatively small steric hindrance, promoting ring opening. This dual-function synergistic effect of "adsorption-activation-nucleophilic ring opening" significantly reduces the activation energy of cycloaddition reactions, enabling the material of this invention to exhibit extremely high catalytic conversion and product selectivity under mild conditions (0.1 MPa at ambient pressure, 80~120 °C), significantly reducing the dependence on high-pressure equipment and energy consumption of traditional processes.

[0042] (2) This invention breaks through the limitations of traditional homogeneous catalysts and dense bulk heterogeneous catalysts. It utilizes photopolymerization 3D printing technology to precisely construct millimeter-scale macroscopic customized flow channels, and combines polymerization-induced phase separation (PIPS) and supercritical drying technology to generate interconnected micro- and nano-scale pores within the polymer framework. This hierarchical porous structure not only endows the material with a huge specific surface area, allowing the halogen nucleophilic sites buried deep within the polymer matrix to be fully exposed, but also provides unobstructed mass transfer channels for macromolecular epoxy compounds and carbon dioxide gas, completely solving the problems of low apparent activity and limited mass transfer in traditional heterogeneous catalysts.

[0043] (3) Unlike traditional homogeneous ionic liquid catalysts that are prone to loss, this invention uses a multifunctional crosslinking agent to firmly anchor the catalytic active center in a three-dimensional polymer network via covalent bonds. Photopolymerization 3D printing endows the material with excellent interlayer bonding and macroscopic mechanical strength, preventing it from pulverizing or collapsing during long-term liquid scouring and stirring. After the reaction, rapid separation of the solid-phase catalyst and liquid-phase product can be achieved simply through physical separation (such as dipping or filtration). After multiple cycle tests, this monolithic catalyst still maintains its initial catalytic activity and porous framework morphology, demonstrating excellent stability for industrial applications.

[0044] (4) Thanks to the high degree of freedom of digital light processing (DLP) or liquid crystal display (LCD) 3D printing technology, the catalytic material of the present invention can be freely designed and molded in one step into an integral catalytic component with a specific geometric topology (such as Gyroid minimal three-period curved surface lattice) according to the internal cavity size and hydrodynamic requirements of different industrial reactors. This feature completely avoids the engineering problems such as large bed pressure drop, channeling and blockage that are easily caused by traditional powder or particulate multiphase catalysts during loading, and provides an ideal catalytic material solution for the industrial continuous production of CO2 resource utilization. Attached Figure Description

[0045] Figure 1 This is the crude product obtained from the cycloaddition reaction in Example 1. 1 H nuclear magnetic resonance spectrum.

[0046] Figure 2 This is an electron microscope image of the porous structure inside the sample of Example 1.

[0047] Figure 3 This is the energy spectrum of the sample from Example 1.

[0048] Figure 4 The crude product obtained by the cycloaddition reaction of Example 1 is shown. 1 H nuclear magnetic resonance spectrum. Detailed Implementation

[0049] Example 1

[0050] (1) Preparation of photosensitive resin: Weigh 60 parts of halogen-containing photopolymerizable ionic liquid monomer (1-vinyl-3-butylimidazolium bromide), 15 parts of multifunctional crosslinking agent (polyethylene glycol diacrylate), 40 parts of non-reactive porogen (ethanol), 1.5 parts of photoinitiator (TPO), and 0.05 parts of light absorber (oligosyl green). Stir at 40°C in the dark for 40 min to obtain a green transparent homogeneous resin.

[0051] (2) 3D printing: A DLP printer was used to import the Gyroid (lattice constant 2mm) model. The single layer thickness was set to 50 μm and the exposure time for each layer was 2.5 s. A lattice preform with macroscopic open flow channels was printed.

[0052] (3) Supercritical drying treatment: The direct displacement method (Treatment A) was adopted, and the preform was placed in a supercritical drying vessel. Liquid CO2 was first introduced, and dynamic displacement was carried out at 3℃ and 8 MPa. The CO2 flow rate was controlled at 1.5 kg / h for 6 hours. This process aims to use the high solubility of liquid CO2 to completely displace the ethanol in the pores of the preform, avoiding capillary action in the subsequent drying process. The temperature inside the vessel was raised to 45℃ and the pressure was increased to 12 MPa to bring CO2 into a supercritical state. This state was maintained for 2 hours to ensure that the system reached homogeneous equilibrium. The pressure was then slowly released to atmospheric pressure at an extremely slow rate of 0.05 MPa / min, allowing CO2 to escape in gaseous form, thereby obtaining a hierarchical porous monolithic catalyst that maintains the integrity of the original microstructure.

[0053] (4) Catalytic application: 10 g of epichlorohydrin substrate and 1 g of the above-mentioned hierarchical porous monolithic catalyst were placed in a reaction flask, and high-purity CO2 was continuously introduced under atmospheric pressure. Magnetic stirring was turned on and the reaction was carried out at 100 °C for 10 h.

[0054] Result: As Figure 1 of 1 The H-NMR spectrum showed no absorption peak for epichlorohydrin at a chemical shift of 3.18 ppm, but a characteristic absorption peak for cyclochloropropene carbonate appeared at 4.89 ppm. The calculated conversion rate of epichlorohydrin was 99.9%, and the selectivity for cyclic carbonates was 99.9%.

[0055] Example 2

[0056] (1) Preparation of photosensitive resin: 50 parts of halogen-containing photopolymerizable ionic liquid monomer (1-vinyl-3-butylimidazolium bromide), 10 parts of photopolymerizable monomer (1-vinyl-3-butylimidazolium hexafluorophosphate), 10 parts of photopolymerizable monomer acrylamide, 12 parts of multifunctional crosslinking agent (PEG600DA), non-reactive porogen (15 parts of deionized water and 25 parts of ethanol), 2 parts of photoinitiator (LAP), and 0.01 parts of colorant. The above materials were magnetically stirred at 400 r / min for 40 min at 30 °C to obtain a transparent homogeneous resin.

[0057] (2) 3D printing: A DLP printer was used to import the honeycomb model. The single layer thickness was set to 50 μm and the exposure time for each layer was 2.5 s. A lattice preform with macroscopic open flow channels was printed.

[0058] (3) Supercritical drying treatment: The indirect replacement method (B treatment) is adopted. The initial embryo is first soaked in anhydrous ethanol for solvent exchange for 24 h. During this period, the ethanol is replaced every 8 h. After the water in the initial embryo is completely replaced, it is transferred to the supercritical drying kettle. The subsequent process parameters are the same as in Example 1 to obtain a hierarchical porous monolithic catalyst.

[0059] (4) Catalytic application: 8 g of butyl glycidyl ether substrate and 1 g of the above-mentioned hierarchical porous monolithic catalyst were placed in a reaction flask, and high-purity CO2 was continuously introduced under atmospheric pressure. The magnetic stirring was turned on and the reaction was carried out at 100 °C for 10 h.

[0060] Result: 1 ¹H-NMR characterization showed a substrate conversion of 92.5%, with a target product selectivity still greater than 99.9%. The lower conversion rate compared to Example 1 was mainly attributed to the dilution of active Br by the introduction of 1-vinyl-3-butylimidazolium hexafluorophosphate. - Concentration of PF6 - Anions are large and lack nucleophilicity; increased substrate molecule size leads to increased mass transfer resistance. This example illustrates the need to balance active site density and pore size for different substrates.

[0061] Example 3

[0062] (1) Preparation of photosensitive resin: 50 parts of halogen-containing photopolymerizable ionic liquid monomer (1-vinyl-3-butylimidazolium bromide), 10 parts of photopolymerizable monomer (1-vinyl-3-butylimidazolium hexafluorophosphate), 10 parts of photopolymerizable monomer 4-acryloylmorpholine, 12 parts of multifunctional crosslinking agent (PEG600DA), 15 parts of non-reactive porogen (15 parts of deionized water and 25 parts of ethanol), 2 parts of photoinitiator (LAP), and 0.01 parts of colorant. The above materials were magnetically stirred at 400 r / min for 40 min at 30 °C to obtain a transparent homogeneous resin.

[0063] (2) 3D printing: A DLP printer was used to import the honeycomb model. The single layer thickness was set to 50 μm and the exposure time for each layer was 2.5 s. A lattice preform with macroscopic open flow channels was printed.

[0064] (3) Supercritical drying treatment: The indirect replacement method (B treatment) is adopted. The initial embryo is first soaked in anhydrous ethanol for solvent exchange for 24 h. During this period, the ethanol is replaced every 8 h. After the water in the initial embryo is completely replaced, it is transferred to the supercritical drying kettle. The subsequent process parameters are the same as in Example 1 to obtain a hierarchical porous monolithic catalyst.

[0065] (4) Catalytic application: 8 g of butyl glycidyl ether substrate and 1 g of the above-mentioned hierarchical porous monolithic catalyst were placed in a reaction flask, and high-purity CO2 was continuously introduced under atmospheric pressure. The magnetic stirring was turned on and the reaction was carried out at 100 °C for 10 h.

[0066] Result: 1 ¹H-NMR characterization showed a substrate conversion of 91.3%, with a target product selectivity still greater than 99.9%. The lower conversion rate compared to Example 1 was mainly attributed to the dilution of active Br by the introduction of 1-vinyl-3-butylimidazolium hexafluorophosphate. - Concentration of PF6 - Anions are large and lack nucleophilicity; increased substrate molecule size leads to increased mass transfer resistance. This example illustrates the need to balance active site density and pore size for different substrates.

[0067] Example 4

[0068] Preparation of photosensitive resin: Weigh 70 parts of halogen-containing photopolymerizable ionic liquid monomer (1-vinyl-3-butylimidazolium iodide with stronger nucleophilicity), 10 parts of photopolymerizable monomer (dipropylene glycol diacrylate), 35 parts of non-reactive porogen (acetone), and 1.2 parts of photoinitiator (TPO). Stir magnetically at 400 r / min for 40 min at 30 ℃ to obtain a transparent homogeneous resin.

[0069] 3D printing and supercritical drying: The model selected is the Kelvin lattice structure, and the printing parameters and drying process are as described in Example 1.

[0070] Catalytic application: 10 g of epichlorohydrin substrate and 1 g of the hierarchical porous monolithic catalyst prepared in this example were placed in a reaction flask, and high-purity CO2 was continuously introduced under atmospheric pressure. The magnetic stirrer was turned on and the reaction was carried out at 80°C for 10 h.

[0071] result: 1 ¹H-NMR characterization showed that the substrate yield was 96.1% and the selectivity was >99.9% after the reaction. Even at low temperatures, highly efficient catalysis was achieved due to the extremely strong nucleophilic attack capability of I⁻, demonstrating the decisive influence of the intrinsic activity of the active site on the reaction conditions.

[0072] Example 5

[0073] (1) Preparation of photosensitive resin: Weigh 50 parts of halogen-containing photopolymerizable ionic liquid monomer (1-vinyl-3-butylimidazolium bromide), 10 parts of photopolymerizable monomer (-isopropylacrylamide), 15 parts of multifunctional crosslinking agent (dipropylene glycol diacrylate), 40 parts of non-reactive porogen (ethanol), 1.5 parts of photoinitiator (TPO), and 0.05 parts of light absorber (olisen green). Stir at 40℃ in the dark for 40 min to obtain a green transparent homogeneous resin.

[0074] (2) 3D printing: A DLP printer was used to import the Gyroid (lattice constant 2mm) model. The single layer thickness was set to 50 μm and the exposure time for each layer was 2.5 s. A lattice preform with macroscopic open flow channels was printed.

[0075] (3) Supercritical drying treatment: The direct displacement method (Treatment A) was adopted, and the preform was placed in a supercritical drying vessel. Liquid CO2 was first introduced, and dynamic displacement was carried out at 3℃ and 8 MPa. The CO2 flow rate was controlled at 1.5 kg / h for 6 hours. This process aims to use the high solubility of liquid CO2 to completely displace the ethanol in the pores of the preform, avoiding capillary action in the subsequent drying process. The temperature inside the vessel was raised to 45℃ and the pressure was increased to 12 MPa to bring CO2 into a supercritical state. This state was maintained for 2 hours to ensure that the system reached homogeneous equilibrium. The pressure was then slowly released to atmospheric pressure at an extremely slow rate of 0.05 MPa / min, allowing CO2 to escape in gaseous form, thereby obtaining a hierarchical porous monolithic catalyst that maintains the integrity of the original microstructure.

[0076] (4) Catalytic application: 10 g of epichlorohydrin substrate and 1 g of the above-mentioned hierarchical porous monolithic catalyst were placed in a reaction flask, and high-purity CO2 was continuously introduced under atmospheric pressure. Magnetic stirring was turned on and the reaction was carried out at 100 °C for 10 h.

[0077] Result: As Figure 1 of 1 The H-NMR spectrum showed no absorption peak for epichlorohydrin at a chemical shift of 3.18 ppm, but a characteristic absorption peak for cyclochloropropene carbonate appeared at 4.89 ppm. The calculated conversion rate of epichlorohydrin was 98.8%, and the selectivity for cyclic carbonates was 99.9%.

[0078] Example 6

[0079] Evaluation of the mechanical stability and cycle life of the material: A three-step washing method was used to regenerate the catalyst. First, the hierarchical porous monolithic catalyst from Example 1, after catalytic reaction, was placed in anhydrous ethanol and washed three times with magnetic stirring for 20 minutes each time to fully dissolve and remove residual cyclic carbonate products in the pores. Then, the catalyst was rinsed with deionized water to remove any trace salts or other impurities. Finally, the washed catalyst was placed in a vacuum drying oven and dried at 100°C for 24 hours to completely remove moisture and restore its active sites.

[0080] Reusability: The recovered catalyst was reintroduced into the cycloaddition reaction of epichlorohydrin while keeping all reaction parameters unchanged (the same as in Example 1), and the cycle experiment was repeated 5 times.

[0081] Results: First cycle: 98.7% yield; Third cycle: 97.9% yield; Fifth cycle: 96.4% yield.

[0082] Analysis: After 5 cycles, the catalytic conversion rate remained above 96%, and the catalyst maintained its complete macroscopic morphology without any visible breakage, swelling, or pulverization. This experiment fully demonstrates that the cross-linked network constructed by photopolymerization 3D printing possesses excellent mechanical strength, while the hierarchical porous structure formed by supercritical drying maintained good structural stability during repeated stirring and washing, ensuring the catalyst has excellent reusability potential.

[0083] Comparative Example 1

[0084] Preparation and formulation: To verify the key role of halide anions, the 1-vinyl-3-butylimidazolium bromide in Example 1 was replaced with the same molar amount of 1-vinyl-3-butylimidazolium hexafluorophosphate. Due to PF6... - The anions are large and have dispersed charges, lacking the nucleophilicity required to attack the epoxy ring. All other components, printing, and drying conditions are identical.

[0085] Catalytic application: 10 g of epichlorohydrin substrate and 1 g of catalyst prepared in Comparative Example 1 were placed in a reaction flask, and high-purity CO2 was continuously introduced under atmospheric pressure. Magnetic stirring was turned on and the reaction was carried out at 100 °C for 10 h.

[0086] Result: As Figure 4 As shown, in the crude product 1 The 1H NMR spectrum showed the absorption peak of epichlorohydrin, and compared with Example 1, the conversion rate of Comparative Example 1 decreased significantly to 84.5%. This comparative experiment confirmed that Br - Halogen anions are key active centers for achieving efficient ring-opening catalysis. While the simple polyionic liquid cationic framework has a certain adsorption and enrichment effect on CO2, it cannot independently complete the efficient nucleophilic attack and ring-opening catalytic transformation of the epoxy ring.

[0087] Comparative Example 2

[0088] Preparation and formulation: The photosensitive resin components and 3D printing process were completely consistent with those in Example 1. However, after obtaining the preform, instead of supercritical drying, it was directly dried in an 80°C vacuum drying oven to constant weight.

[0089] Results: The dried material underwent severe volume shrinkage (up to 45%), and SEM observation revealed that its internal microporous structure almost completely disappeared, presenting as a dense mass. Under the same conditions, the conversion rate of epichlorohydrin dropped sharply to 35.8%.

[0090] Analysis: The surface tension generated by solvent evaporation during conventional drying leads to the collapse of micro- and nano-pores, resulting in most active sites being enclosed in a dense polymer matrix, demonstrating the necessity of supercritical drying in constructing hierarchical porous mass transfer networks.

[0091] Comparative Example 3

[0092] Formulation and preparation: Using the resin formulation of Example 1, instead of 3D printing, the resin was poured into a mold and solidified into a large solid block. Then, it was mechanically crushed, ground, and sieved to obtain fine powder particles of about 200 mesh.

[0093] Results: Due to the lack of macroscopic open channels provided by 3D printing, powdered materials are prone to agglomeration in viscous epoxy liquids. Under the same conditions, the conversion rate of ECH reaction after 8 h was only 68.2%. Moreover, high-speed centrifugation (10000 r / min) was required for separation and recovery after the reaction.

[0094] Analysis: This study demonstrates that 3D-printed custom macroscopic flow channels can significantly reduce fluid mass transfer resistance, increase apparent reaction rates, and greatly simplify solid-liquid separation and recycling processes due to their monolithic structure.

Claims

1. A method for preparing a hierarchical porous material with catalytic activity, characterized in that, Includes the following steps (1) Preparation of photosensitive resin: Place halogen-containing photopolymerizable ionic liquid monomer, photopolymerizable monomer, multifunctional crosslinking agent, non-reactive porogen, photoinitiator and photoabsorber in a light-proof container, and stir in the dark for 5 to 120 min at 25 to 80 °C to obtain photosensitive resin. The halogen-containing photopolymerizable ionic liquid monomer is at least one of a 1-vinyl type monomer 1 and an acrylate type monomer 1, with structural formulas shown in formulas (a) and (b), respectively, wherein R and R3 are alkyl segments, and X - It consists of iodide ions, bromide ions, or chloride ions; ； The photopolymerizable monomer is at least one of 1-vinyl monomer 2, acrylate monomer 2 or acrylate monomer 3, acrylamide or its derivative, and 4-acryloylmorpholine, wherein the structural formulas of 1-vinyl monomer 2, acrylate monomer 2, and acrylate monomer 3 are shown in formulas (c), (d), and (e), respectively, where R, R1, and R2 are alkyl segments, and Z... - It is one of nitrate ions, trifluoromethanesulfonylimide, tetrafluoroborate ions, and hexafluorophosphate ions; ； (2) 3D printing molding: The photosensitive resin is placed in the material tank of the photocuring 3D printing equipment and cured and printed to obtain a printing preform containing a pore-forming agent; (3) Supercritical drying treatment: The printed preform is placed in a supercritical drying device and extracted and replaced with liquid CO2 as a medium. Then the temperature and pressure are increased to above the supercritical point of CO2. The pore-forming agent and residual solvent are removed by supercritical drying treatment to obtain a hierarchical porous material with catalytic activity.

2. The method for preparing a hierarchical porous material with catalytic activity according to claim 1, characterized in that, The weight parts of each raw material component of the photosensitive resin are as follows: 5-80 parts of halogen-containing photopolymerizable ionic liquid monomer, 0-60 parts of photopolymerizable monomer, 3-30 parts of multifunctional crosslinking agent, 15-70 parts of non-reactive porogen, 0.01-15 parts of photoinitiator, and 0-15 parts of light absorber.

3. The method for preparing a hierarchical porous material with catalytic activity according to claim 1, characterized in that, The multifunctional crosslinking agent is at least one of the following: a difunctional acrylate monomer or its prepolymer, a trifunctional acrylate monomer or its prepolymer, or a tetrafunctional or higher acrylate monomer or its prepolymer.

4. The method for preparing a hierarchical porous material with catalytic activity according to claim 3, characterized in that, The multifunctional crosslinking agent is at least one of the following: 1,6-hexanediol diacrylate, ethylene glycol dimethacrylate, tripropylene glycol diacrylate, dipropylene glycol diacrylate, neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, diethylene glycol diacrylate phthalate, tricyclodecanediethanol diacrylate, 1,4-butanediol diacrylate, 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, ethoxylated bisphenol A diacrylate, polytetramethylene glycol diacrylate, and ethoxylated 1,6-hexanediol diacrylate.

5. The method for preparing a hierarchical porous material with catalytic activity according to claim 1, characterized in that, The non-reactive porogen is selected from at least one of alcohols, ketones, esters, ethers, water, acetonitrile, and hexane; the light absorber is selected from light-absorbing dyes; the photoinitiator is selected from at least one of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, liquid form of TPO-L, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, 2,2-dimethoxy-2-phenylacetophenone, benzophenone, camphorquinone, Irgacure 184, Irgacure 2100, lithium phenyl-2,4,6-trimethylbenzoyl phosphite, and a complex of vitamin B2 and triethanolamine.

6. The method for preparing a hierarchical porous material with catalytic activity according to claim 1, characterized in that, The 3D printing equipment is selected from one of the following: stereolithography, digital light processing, liquid crystal display mask, continuous liquid interface manufacturing, two-photon polymerization, and volumetric additive manufacturing equipment.

7. The method for preparing a hierarchical porous material with catalytic activity according to claim 1, characterized in that, Based on the miscibility between the pore-forming agent and the CO2 medium, the specific process for step (3) is either treatment A or treatment B: Treatment A: If the pore-forming agent and CO2 are miscible, place the above-mentioned preform directly into a supercritical drying vessel and pass liquid CO2 through it at -10~20°C and 1~10 MPa for solvent replacement for 3~10 h; then, raise the temperature to 31~80 ℃ and pressurize it to 7.4~20 MPa to bring the CO2 in the equipment to a supercritical state; finally, slowly depressurize it to atmospheric pressure at a depressurization rate of 0.01~0.1 MPa / min and take out the sample. Treatment B: If the porogen has poor miscibility with CO2, first immerse the preform in a transitional solvent miscible with CO2 for 10-36 hours, changing the solvent 1-3 times during this period. After the porogen in the preform is completely replaced, transfer it to a supercritical drying reactor and pass liquid CO2 through it at -10-20 °C and 1-10 MPa for solvent replacement for 3-10 hours. Then, raise the temperature to 31-80 °C and pressurize it to 7.4-20 MPa to bring the CO2 in the equipment to a supercritical state. Finally, slowly depressurize it to atmospheric pressure at a depressurization rate of 0.01-0.1 MPa / min and remove the sample.

8. A hierarchical porous material with catalytic activity obtained by the preparation method according to any one of claims 1 to 7.

9. The application of the hierarchical porous material with catalytic activity as described in claim 8 in the cycloaddition reaction of CO2 with epoxides.

10. The application according to claim 9, characterized in that, The epoxy compound is at least one of epichlorohydrin, butyl glycidyl ether, allyl glycidyl ether, styrene oxide, 1,2-epoxyhexane, and glycidyl methacrylate.

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