A porous carbon-based getter composite and a method for producing the same

Abstract

The application discloses a kind of porous carbon-based getter composite material and preparation method thereof, belong to adsorbing material technical field, for solving in prior art, how to further improve the technical problem of porosity, adsorption rate and adsorption capacity of carbon-based getter composite material, specifically includes the following composition by weight parts: 55-65 parts iron modification nitrogen enrichment type zinc heterocyclic skeleton, 30-35 parts lignin phenol formaldehyde prepolymer and 8-10 parts palladium modification graphene oxide.The synergistic effect between the iron modification nitrogen enrichment type zinc heterocyclic skeleton, lignin phenol formaldehyde prepolymer and palladium modification graphene oxide prepared by the application can further improve the porosity, adsorption rate and adsorption capacity of the porous carbon-based getter composite material prepared.

Description

Technical Field

[0001] This invention relates to the field of adsorption materials technology, specifically to a porous carbon-based gas-absorbing composite material and its preparation method. Background Technology

[0002] As key functional materials in fields such as vacuum insulation, electronic packaging, and gas purification, the adsorption performance of getter materials directly determines the working efficiency and service life of devices. With the rapid development of related technologies, higher requirements are being placed on the porosity, adsorption rate, and adsorption capacity of getter materials.

[0003] Currently, porous carbon materials are widely used due to their high specific surface area and chemical stability. Traditional porous carbon materials are mostly prepared by using phenolic resin and pitch as carbon sources and undergoing high-temperature carbonization and activation. However, they suffer from problems such as difficulty in controlling pore distribution and limited active sites, which restricts performance improvement. Although metal-organic framework (MOF) derived porous carbon materials have advantages such as tunable structure and uniform pore size, especially zinc-based nitrogen-containing MOF materials, they are prone to structural collapse during carbonization and have a single active site. Therefore, the gas adsorption kinetics and capacity still need to be improved.

[0004] Lignin, as an abundant renewable biomass, possesses an aromatic ring structure and rich oxygen-containing functional groups. Introducing it into phenolic resins to prepare prepolymers can reduce the consumption of petroleum-based raw materials and regulate the carbonization process. However, the specific surface area and adsorption performance of lignin-based carbon materials prepared alone are insufficient to meet high-performance requirements. Graphene oxide, with its two-dimensional sheet structure and large specific surface area, is often used as a reinforcing component in composite carbon materials. Loading noble metal nanoparticles on its surface can enhance adsorption kinetics through catalytic dissociation. However, how to achieve uniform dispersion of graphene oxide with other carbon source components and fully leverage the synergistic effect among the components remains a technical challenge that urgently needs to be addressed in current research. Summary of the Invention

[0005] The purpose of this invention is to provide a porous carbon-based air-absorbing composite material and its preparation method, which solves the technical problem of how to further improve the porosity, adsorption rate and adsorption capacity of air-absorbing composite materials in the prior art.

[0006] The objective of this invention can be achieved through the following technical solution: a porous carbon-based air-absorbing composite material, comprising the following components by weight: 55-65 parts of iron-modified nitrogen-enriched zinc heterocyclic framework, 30-35 parts of lignin phenolic prepolymer and 8-10 parts of palladium-modified graphene oxide;

[0007] The iron-modified nitrogen-enriched zinc heterocyclic skeleton was prepared by coordination self-assembly of zinc nitrate hexahydrate, pyridine-3,5-dicarboxylic acid and 3-amino-1,2,4-triazole, followed by ion exchange and coordination modification with ferric nitrate nonahydrate.

[0008] The lignin-phenolic prepolymer is prepared by alkali lignin, phenol and formaldehyde through alkali-catalyzed hydroxymethylation and condensation polymerization reaction.

[0009] The palladium-modified graphene oxide is prepared by adsorbing and loading graphene oxide with palladium chloride, followed by reduction with ascorbic acid, so that palladium nanoparticles are loaded in situ onto the surface of graphene oxide.

[0010] Furthermore, the iron-modified nitrogen-enriched zinc heterocyclic framework is prepared by the following steps:

[0011] A1. Add zinc nitrate hexahydrate, pyridine-3,5-dicarboxylic acid, and 3-amino-1,2,4-triazole to a mixed solution containing N,N-dimethylformamide and deionized water. Stir until completely dissolved, then add triethylamine and continue stirring for 5-10 minutes. Transfer the mixed solution to a polytetrafluoroethylene-lined reactor and react at 80-90℃ for 60-72 hours. After the reaction is complete, allow it to cool naturally to room temperature, centrifuge, and wash the solid product 2-3 times with N,N-dimethylformamide and anhydrous ethanol, respectively. Then place it in a vacuum drying oven and dry at 60℃ to constant weight to obtain a three-dimensional zinc-based nitrogen-enriched porous lattice.

[0012] A2. A three-dimensional zinc-based nitrogen-enriched porous lattice was added to a reactor containing N,N-dimethylformamide. After ultrasonic dispersion for 20-30 min, an aqueous solution of ferric nitrate nonahydrate was added and stirred for 20-30 min. The mixed solution was then transferred to a polytetrafluoroethylene-lined reactor and reacted at 80-90℃ for 20-24 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature and then centrifuged. The solid product was washed 2-3 times with N,N-dimethylformamide and anhydrous ethanol, respectively, and then placed in a vacuum drying oven and dried at 60℃ to constant weight to obtain an iron-modified nitrogen-enriched zinc heterocyclic framework.

[0013] Further, in step A1, the ratio of zinc nitrate hexahydrate, pyridine-3,5-dicarboxylic acid, and 3-amino-1,2,4-triazole added to the solution containing N,N-dimethylformamide, deionized water, and triethylamine is 0.9 g:0.5 g:0.25 g:36-40 mL:3 mL:0.2 mL; in step A2, the ratio of the three-dimensional zinc-based nitrogen-enriched porous lattice, N,N-dimethylformamide, and ferric nitrate nonahydrate aqueous solution is 1 g:35-40 mL:8-10 mL, and the mass fraction of the ferric nitrate nonahydrate aqueous solution is 3%.

[0014] Furthermore, the preparation method of the lignin phenolic prepolymer is as follows: alkali lignin and phenol are added to a reaction vessel containing an aqueous ethanol solution and a concentrated ammonia solution. After stirring at 50-60°C until completely dissolved, an aqueous formaldehyde solution is added. After reacting at 50-60°C for 2-3 hours, the temperature is raised to 80-100°C and reacted for 5-6 hours. After the reaction is completed, the mixture is filtered, and the product is washed 3-4 times with deionized water. Then, it is transferred to a vacuum drying oven and dried at 80-90°C for 8-10 hours to obtain the lignin phenolic prepolymer.

[0015] Furthermore, the ratio of the amount of alkali lignin, phenol, ethanol aqueous solution, concentrated ammonia aqueous solution and formaldehyde aqueous solution is 8g:2-3g:70-80mL:7-8mL:7mL, the mass fraction of the ethanol aqueous solution is 50%, the mass fraction of the concentrated ammonia aqueous solution is 25%, and the mass fraction of the formaldehyde aqueous solution is 37%.

[0016] Furthermore, the preparation method of palladium-modified graphene oxide is as follows: hexadecyltrimethylammonium bromide and graphene oxide are added to a reaction vessel containing deionized water, ultrasonically dispersed for 40-60 min, palladium chloride aqueous solution is added, and sodium hydroxide solution is added dropwise to adjust the pH of the system to 10. Then, ascorbic acid aqueous solution is added, and the mixture is stirred at 60-70℃ for 3-4 h. After the reaction is completed, the mixture is filtered, and the filter cake is washed 2-3 times with deionized water and anhydrous ethanol, respectively. Then, it is transferred to a vacuum drying oven and dried at 70℃ to constant weight to obtain palladium-modified graphene oxide.

[0017] Furthermore, the ratio of the hexadecyltrimethylammonium bromide, graphene oxide, deionized water, palladium chloride aqueous solution, and ascorbic acid aqueous solution is 2.5g:1g:40-50mL:5-6mL:6-8mL, the mass fraction of the ascorbic acid aqueous solution is 2%, and the mass fraction of the sodium hydroxide solution is 4.8%; the palladium chloride aqueous solution is obtained by dissolving 0.05g of palladium chloride in 0.05mL of 37wt% concentrated hydrochloric acid and 5mL of deionized water.

[0018] One method for preparing a porous carbon-based air-getting composite material includes the following steps:

[0019] S1. Add lignin phenolic prepolymer, iron-modified nitrogen-enriched zinc heterocyclic framework and palladium-modified graphene oxide to a reaction vessel containing an aqueous ethanol solution, ultrasonically disperse for 20-30 min, and stir at 30-40℃ for 2-3 h to obtain precursor composite liquid.

[0020] S2. Add melamine ethanol dispersion to the precursor composite liquid, stir at 60-70℃ for 2-3 hours, then heat to 90-100℃ and react for 3-4 hours. Then evaporate and concentrate at 100-110℃ to a solid content of 50-60wt%, press into shape at 10-15MPa, and then transfer to a drying oven to dry at 100-120℃ for 7-8 hours to obtain the molded matrix.

[0021] S3. Transfer the molded matrix to a tube furnace and heat it to 500-600℃ at a rate of 3-5℃ / min under a nitrogen atmosphere. Hold the temperature for 1-2 hours, then continue heating to 800-900℃ and hold for 1-2 hours. Cool to room temperature, remove and crush the matrix, mix the powder evenly with KOH powder, and then transfer it to a tube furnace. Hold the mixture at 700-800℃ for 40-60 minutes, then wash it 2-3 times with hydrochloric acid solution for 20-30 minutes each time. Wash it with deionized water until the washing solution is neutral, transfer it to a drying oven, dry it at 120℃ to constant weight, and then anneal it at 400-500℃ to obtain a porous carbon-based gas-absorbing composite material.

[0022] Further, in step S1, the mass fraction of the ethanol aqueous solution is 50%, and the amount of the ethanol aqueous solution used is 800-1000 mL; in step S2, the mass fraction of the melamine ethanol dispersion is 10%, and the amount of the melamine ethanol dispersion used is 100 mL; in step S3, the amount of KOH powder used is 120 g, and the mass fraction of the hydrochloric acid solution is 6%.

[0023] The present invention has the following beneficial effects:

[0024] 1. The iron-modified nitrogen-enriched zinc heterocyclic framework of the present invention possesses a three-dimensional ordered porous lattice structure. Its zinc-containing metal nodes decompose and volatilize during high-temperature pyrolysis, serving as self-templates to construct initial pore channels in situ within a carbon matrix. Simultaneously, the abundant nitrogen coordination environment and iron species within the framework transform into nitrogen- and iron-containing active structural units during carbonization, participating in the construction and stabilization of pore walls. The lignin-phenolic prepolymer serves as a continuous carbon source, forming a continuous carbon framework network after high-temperature carbonization. The alternating copolymerization structure of lignin structural units and phenolic resin in its molecular chain ensures more uniform carbon layer growth during carbonization, providing a favorable reaction for subsequent chemical activation. The matrix, after activation and etching with potassium hydroxide, can generate a large number of hierarchical micropores and mesopores. Palladium-modified graphene oxide is interspersed between the carbon matrix in a two-dimensional sheet structure. The palladium nanoparticles loaded on its surface can act as physical barrier points to effectively inhibit the stacking and aggregation of carbon layers. At the same time, the oxygen-containing functional groups on the surface of graphene oxide form hydrogen bonds and π-π interactions with lignin phenolic prepolymer, which enhances interfacial bonding and guides the orderly growth of pore structures. The three work together to provide initial pore templates for the framework, form a continuous porous carbon matrix through resin carbonization, and separate and support the pore structure to prevent it from collapsing. Together, they construct a hierarchical porous carbon-based composite material with a high specific surface area.

[0025] 2. The iron-modified nitrogen-enriched zinc heterocyclic framework of the present invention forms an Fe-Nx coordination structure after pyrolysis. These iron-nitrogen co-doped active sites have strong chemical adsorption and catalytic activation effects on gas molecules, which can reduce the energy barrier of gas adsorption and accelerate the adsorption process. The palladium nanoparticles uniformly loaded on the surface of palladium-modified graphene oxide serve as highly active catalytic sites, which can produce a dissociation adsorption effect on gas molecules, significantly improving the adsorption kinetic rate of gas on the material surface. At the same time, the two-dimensional sheet structure of graphene oxide provides a planar channel for rapid diffusion of gas molecules. The nitrogen-doped carbon framework formed by the carbonization of lignin phenolic prepolymer forms a good conductive and mass transfer network with the above-mentioned active components. The hierarchical porous structure contains a multi-level channel system of macropores-mesopores-micropores, which provides a rapid transport path for gas molecules from the outer surface to the internal active sites, shortening the gas diffusion distance. The three work synergistically: palladium nanoparticles catalyze the dissociation and activation of gas molecules, iron-nitrogen active sites provide strong adsorption binding sites, and the hierarchical channel structure accelerates gas mass transfer and diffusion, together giving the composite material excellent initial adsorption rate and sustained adsorption kinetic performance.

[0026] 3. The iron-nitrogen co-doped carbon structure formed by the pyrolysis of the iron-modified nitrogen-enriched zinc heterocyclic framework of the present invention has strong interactions between its Fe-Nx active sites and nitrogen-containing functional groups and gas molecules through chemisorption, increasing the adsorption binding energy and adsorption capacity of a single site. The palladium nanoparticles on the surface of palladium-modified graphene oxide not only have catalytic activation effects, but also provide additional adsorption sites through metal-gas interactions. Their high dispersion ensures the full exposure and utilization of active sites. The high specific surface area carbon matrix formed by carbonization and activation of lignin phenolic prepolymer has abundant microporous structure, providing a large physical adsorption space for gas molecules. At the same time, the nitrogen atoms doped in the carbon framework can change the electronic structure of the carbon material and enhance the adsorption affinity for gas molecules. The three work synergistically. The iron-nitrogen active sites and palladium active sites provide multiple chemisorption centers, the high specific surface area integral graded pore structure provides sufficient physical adsorption space, and the nitrogen-doped carbon framework further enhances the interaction between gas and material. Multiple adsorption mechanisms work synergistically to enable the composite material to exhibit excellent gas adsorption capacity within a certain period of time. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In this application, the alkali lignin is selected from Hubei Maidehao Biotechnology Co., Ltd., and the model is MDH.

[0029] In this application, the graphene oxide is selected from Henan Liugong Graphite Co., Ltd., with a specification of 1000 mesh, model number LG-1401, and grade lgsm;

[0030] In this application, ZIF-8 was selected from Xi'an Qiyue Biotechnology Co., Ltd., CAS number 59061-53-9, with a pore size of 0.34 nm and a pore volume of 0.66 cm³ at 1.1 nm. 3 / g, specific surface area BET is 1500 m 2 / g;

[0031] In this application, the phenolic resin is selected from Jinan Dahui Chemical Technology Co., Ltd., with CAS number 9003-35-4, grade number 2123, and model number 2123.

[0032] Example 1

[0033] This embodiment provides a method for preparing an iron-modified nitrogen-enriched zinc heterocyclic framework, comprising the following steps:

[0034] Step i: Preparation of a three-dimensional zinc-based nitrogen-enriched porous lattice

[0035] Weigh out 90g of zinc nitrate hexahydrate, 50g of pyridine-3,5-dicarboxylic acid, and 25g of 3-amino-1,2,4-triazole and add them to a mixed solution containing 3600mL of N,N-dimethylformamide and 300mL of deionized water. Stir until completely dissolved, then add 20mL of triethylamine and continue stirring for 5min. Transfer the mixed solution to a polytetrafluoroethylene-lined reactor and react at 80℃ for 60h. After the reaction is complete, allow it to cool naturally to room temperature, centrifuge, and wash the solid product twice with N,N-dimethylformamide and anhydrous ethanol, respectively. Then place it in a vacuum drying oven and dry it at 60℃ to constant weight to obtain a three-dimensional zinc-based nitrogen-enriched porous lattice.

[0036] Step ii: Preparation of iron-modified nitrogen-enriched zinc heterocyclic framework

[0037] Weigh 50g of three-dimensional zinc-based nitrogen-enriched porous lattice and add it to a reactor containing 1750mL of N,N-dimethylformamide. After ultrasonic dispersion for 20min, add 40mL of 3wt% ferric nitrate nonahydrate aqueous solution and stir for 20min. Transfer the mixed solution to a polytetrafluoroethylene-lined reactor and react at 80℃ for 20h. After the reaction is completed, allow it to cool naturally to room temperature, centrifuge, and wash the solid product twice with N,N-dimethylformamide and anhydrous ethanol, respectively. Then place it in a vacuum drying oven and dry it at 60℃ to constant weight to obtain an iron-modified nitrogen-enriched zinc heterocyclic framework.

[0038] Reaction mechanism for preparing iron-modified nitrogen-enriched zinc heterocyclic framework:

[0039] Zinc nitrate hexahydrate, pyridine-3,5-dicarboxylic acid, and 3-amino-1,2,4-triazole were added to a mixed solvent of N,N-dimethylformamide and deionized water. Triethylamine promoted the deprotonation of the carboxylic acid ligands, causing the generated carboxylate anion to coordinate with zinc ions via Zn-O coordination. Simultaneously, the nitrogen-containing coordination sites in 3-amino-1,2,4-triazole formed Zn-N bonds with zinc ions. A three-dimensional zinc-based nitrogen-enriched porous lattice was constructed through multidentate ligand bridging and self-assembly of metal nodes. Subsequently... The obtained lattice was dispersed in N,N-dimethylformamide, and an aqueous solution of ferric nitrate nonahydrate was added to allow iron ions to fully diffuse into the material channels. Through coordination with carboxylic acid oxygen, triazole nitrogen, and amino nitrogen sites, Fe-O / Fe-N bonds were formed. At the same time, some zinc ion / iron ion metal node exchange occurred, realizing the uniform introduction of iron species into the zinc-based framework. Finally, an iron-modified nitrogen-enriched zinc heterocyclic framework with Zn / Fe synergistic coordination structure and rich nitrogen coordination environment was constructed.

[0040] Example 2

[0041] This embodiment provides a method for preparing an iron-modified nitrogen-enriched zinc heterocyclic framework, comprising the following steps:

[0042] Step i: Preparation of a three-dimensional zinc-based nitrogen-enriched porous lattice

[0043] Weigh out 90g of zinc nitrate hexahydrate, 50g of pyridine-3,5-dicarboxylic acid, and 25g of 3-amino-1,2,4-triazole and add them to a mixed solution containing 3800mL of N,N-dimethylformamide and 300mL of deionized water. Stir until completely dissolved, then add 20mL of triethylamine and continue stirring for 8 minutes. Transfer the mixed solution to a polytetrafluoroethylene-lined reactor and react at 85℃ for 66 hours. After the reaction is complete, allow it to cool naturally to room temperature, centrifuge, and wash the solid product twice with N,N-dimethylformamide and anhydrous ethanol, respectively. Then place it in a vacuum drying oven and dry it at 60℃ to constant weight to obtain a three-dimensional zinc-based nitrogen-enriched porous lattice.

[0044] Step ii: Preparation of iron-modified nitrogen-enriched zinc heterocyclic framework

[0045] Weigh 50g of three-dimensional zinc-based nitrogen-enriched porous lattice and add it to a reactor containing 1875mL of N,N-dimethylformamide. After ultrasonic dispersion for 25min, add 45mL of 3wt% ferric nitrate nonahydrate aqueous solution and stir for 25min. Transfer the mixed solution to a polytetrafluoroethylene-lined reactor and react at 85℃ for 22h. After the reaction is completed, allow it to cool naturally to room temperature, centrifuge, and wash the solid product twice with N,N-dimethylformamide and anhydrous ethanol, respectively. Then place it in a vacuum drying oven and dry it at 60℃ to constant weight to obtain an iron-modified nitrogen-enriched zinc heterocyclic framework.

[0046] Example 3

[0047] This embodiment provides a method for preparing an iron-modified nitrogen-enriched zinc heterocyclic framework, comprising the following steps:

[0048] Step i: Preparation of a three-dimensional zinc-based nitrogen-enriched porous lattice

[0049] Weigh out 90g of zinc nitrate hexahydrate, 50g of pyridine-3,5-dicarboxylic acid, and 25g of 3-amino-1,2,4-triazole and add them to a mixed solution containing 4000mL of N,N-dimethylformamide and 300mL of deionized water. Stir until completely dissolved, then add 20mL of triethylamine and continue stirring for 10min. Transfer the mixed solution to a polytetrafluoroethylene-lined reactor and react at 90℃ for 72h. After the reaction is complete, allow it to cool naturally to room temperature, centrifuge, and wash the solid product three times with N,N-dimethylformamide and anhydrous ethanol, respectively. Then place it in a vacuum drying oven and dry it at 60℃ to constant weight to obtain a three-dimensional zinc-based nitrogen-enriched porous lattice.

[0050] Step ii: Preparation of iron-modified nitrogen-enriched zinc heterocyclic framework

[0051] Weigh 50g of three-dimensional zinc-based nitrogen-enriched porous lattice and add it to a reactor containing 2000mL of N,N-dimethylformamide. After ultrasonic dispersion for 30min, add 50mL of 3wt% ferric nitrate nonahydrate aqueous solution and stir for 30min. Transfer the mixed solution to a polytetrafluoroethylene-lined reactor and react at 90℃ for 24h. After the reaction is completed, allow it to cool naturally to room temperature, centrifuge, and wash the solid product three times with N,N-dimethylformamide and anhydrous ethanol, respectively. Then place it in a vacuum drying oven and dry it at 60℃ to constant weight to obtain an iron-modified nitrogen-enriched zinc heterocyclic framework.

[0052] Example 4

[0053] This embodiment provides a method for preparing a porous carbon-based air-getting composite material, including the following steps:

[0054] Step (1): Preparation of lignin-phenolic prepolymer

[0055] Weigh 80g of alkali lignin and 20g of phenol and add them to a reaction vessel containing 700mL of 50wt% ethanol aqueous solution and 70mL of 25wt% concentrated ammonia aqueous solution. Stir at 50℃ until completely dissolved, then add 70mL of 37wt% formaldehyde aqueous solution. React at 50℃ for 2 hours, then raise the temperature to 80℃ and react for 5 hours. After the reaction is complete, filter, wash the product three times with deionized water, transfer it to a vacuum drying oven, and dry at 80℃ for 8 hours to obtain lignin phenolic prepolymer.

[0056] Reaction mechanism for preparing lignin phenolic prepolymers:

[0057] Under alkaline conditions provided by a mixed solvent of ethanol and water and concentrated ammonia, phenol and alkali lignin are first activated by alkali, causing the reactive phenolic sites in phenol and lignin to form highly reactive phenolate structures. Then, after the addition of formaldehyde, the system preferentially undergoes hydroxymethylation, introducing hydroxymethyl groups into the ortho and para positions of the aromatic ring of phenol and into the phenolic structural units with free reactive sites in lignin, generating hydroxymethylphenol and hydroxymethylated lignin intermediates. Subsequently, the above intermediates undergo further condensation polymerization, forming methylene bridges between hydroxymethyl groups and the active sites of the aromatic ring, and methylene ether bridges between some hydroxymethyl groups, thereby gradually incorporating the lignin structural units into the phenolic resin network. After washing and vacuum drying, a lignin-modified phenolic prepolymer containing methyl alcohol groups, methylene bridges, and methylene ether bridges is obtained.

[0058] Step 2: Preparation of palladium-modified graphene oxide

[0059] Weigh out 0.5 g of palladium chloride and dissolve it in 0.5 mL of 37 wt% concentrated hydrochloric acid and 50 mL of deionized water to obtain an aqueous solution of palladium chloride.

[0060] Weigh 25g of hexadecyltrimethylammonium bromide and 10g of graphene oxide and add them to a reaction vessel containing 400mL of deionized water. After ultrasonic dispersion for 40min, add 50mL of palladium chloride aqueous solution and add 4.8wt% sodium hydroxide solution dropwise to adjust the pH of the system to 10. Then add 60mL of 2wt% ascorbic acid aqueous solution and stir at 60℃ for 3h. After the reaction is completed, filter and wash the filter cake twice with deionized water and anhydrous ethanol, respectively. Then transfer it to a vacuum drying oven and dry it at 70℃ to constant weight to obtain palladium-modified graphene oxide.

[0061] Reaction mechanism for preparing palladium-modified graphene oxide:

[0062] In the preparation process, oxygen-containing functional groups such as hydroxyl, epoxy, carboxyl and carbonyl groups on the surface of graphene oxide first serve as adsorption and anchoring sites for palladium precursors. Hexadecyltrimethylammonium bromide acts as a cationic surfactant to improve the dispersibility of graphene oxide in the aqueous phase and plays a stabilizing and confining role in the subsequent nucleation and growth of palladium nanoparticles. Palladium chloride forms chlorine-coordinated Pd(II) species in acidic aqueous solution. After adding sodium hydroxide to adjust the system to alkalinity, Pd(II) undergoes hydroxylation coordination transformation and is further enriched on the surface of graphene oxide. Subsequently, ascorbic acid acts as a mild reducing agent to reduce the adsorbed Pd(II) on the surface to Pd(0) in situ, so that metallic palladium preferentially nucleates on the surface of graphene oxide sheets and grows in a controlled manner. Finally, a palladium-modified graphene oxide composite material with Pd nanoparticles uniformly anchored on the surface of graphene oxide sheets is obtained.

[0063] Step 3: Preparation of precursor composite liquid

[0064] Weigh out 55 parts by weight of the iron-modified nitrogen-enriched zinc heterocyclic framework prepared in Example 1, 30 parts of lignin phenolic prepolymer and 8 parts of palladium-modified graphene oxide and add them to a reaction vessel containing 800 mL of 50 wt% ethanol aqueous solution. After ultrasonic dispersion for 20 min, stir at 30 °C for 2 h to obtain the precursor composite solution.

[0065] Step 4: Prepare the molding substrate

[0066] 100 mL of 10 wt% melamine ethanol dispersion was added to the precursor composite solution. After stirring at 60 °C for 2 h, the temperature was raised to 90 °C and reacted for 3 h. The mixture was then evaporated and concentrated at 100 °C to a solid content of 50 wt%, and pressed into shape at 10 MPa. The mixture was then transferred to a drying oven and dried at 100 °C for 7 h to obtain the molded matrix.

[0067] Reaction mechanism for preparing the molded matrix:

[0068] The lignin-phenolic prepolymer serves as a continuous binder phase, uniformly wetting and dispersing the iron-modified nitrogen-enriched zinc heterocyclic framework and palladium-modified graphene oxide. The oxygen-containing functional groups and aromatic lamellar structures on the surface of the palladium-modified graphene oxide form hydrogen bonds and π-π interactions with the lignin-phenolic prepolymer, thereby enhancing interfacial bonding. Upon addition of melamine dispersion, melamine, as a high-nitrogen polyamino component, embeds itself into the precursor system and promotes system homogenization through interactions with the polar groups on the prepolymer and graphene oxide surfaces. Simultaneously, it partially co-condenses with residual active hydroxymethyl groups in the prepolymer. Subsequently, under heating conditions, the lignin-phenolic prepolymer continues to undergo condensation reactions centered on hydroxymethyl groups, gradually forming methylene bridges and methylene ether bridges, continuously increasing the system's molecular weight and crosslinking degree. As ethanol and water evaporate and the system's solid content increases, the resin network's coating and bridging effect on each dispersed phase is further enhanced. During pressing and drying, densification and structural fixation are achieved, ultimately yielding a molded matrix with a certain mechanical strength.

[0069] Step 5: Preparation of porous carbon-based air-getter composite materials

[0070] The molded matrix was transferred to a tube furnace and heated to 500°C at a rate of 3°C / min under a nitrogen atmosphere. After holding at this temperature for 1 hour, the temperature was further increased to 800°C and held for 1 hour. After cooling to room temperature, the matrix was removed, pulverized, and the powder was uniformly mixed with 120g of KOH powder. The mixture was then transferred to a tube furnace and held at 700°C for 40 minutes. The matrix was then washed twice with a 6wt% hydrochloric acid solution for 20 minutes each time, followed by washing with deionized water until the washing solution was neutral. The matrix was then transferred to a drying oven and dried at 120°C to constant weight. Finally, it was annealed at 400°C to obtain a porous carbon-based gas-absorbing composite material.

[0071] Reaction mechanism for preparing porous carbon-based air-getter composites:

[0072] The molding matrix first undergoes pre-carbonization and high-temperature reconstruction under a nitrogen atmosphere. The lignin phenolic prepolymer forms a carbon skeleton through dehydration, bond breaking, and aromatization carbonization. After melamine pyrolysis, nitrogen-containing sites are introduced into the carbon skeleton. The iron-modified nitrogen-enriched zinc heterocyclic skeleton provides an active structural source for the coexistence of Fe and N during pyrolysis. Initial pores are formed due to the decomposition of the zinc skeleton and the volatilization of zinc species. Subsequently, the pre-carbonized powder is chemically activated after being mixed with KOH. KOH and its transformed species such as K, K2CO3, and K2O undergo oxidation-reduction, vaporization etching, and interlayer intercalation with the carbon skeleton, which continuously etches the carbon skeleton and forms a large number of micropores and some mesopores, further opening the original channels. Then, after immersion in hydrochloric acid, the residual potassium salts, metal oxides, and other acid-soluble inorganic components are removed, and the pore structure is further released and connected. Finally, after annealing, the unstable functional groups on the material surface are further eliminated, and the structure of the carbon skeleton and active sites tends to be stable, ultimately obtaining a porous carbon-based gas-absorbing composite material.

[0073] Example 5

[0074] This embodiment provides a method for preparing a porous carbon-based air-getting composite material, including the following steps:

[0075] Step (1): Preparation of lignin-phenolic prepolymer

[0076] Weigh 80g of alkali lignin and 25g of phenol and add them to a reaction vessel containing 750mL of 50wt% ethanol aqueous solution and 75mL of 25wt% concentrated ammonia aqueous solution. Stir at 55℃ until completely dissolved, then add 70mL of 37wt% formaldehyde aqueous solution. React at 55℃ for 2.5h, then raise the temperature to 90℃ and react for 5.5h. After the reaction is complete, filter, wash the product three times with deionized water, transfer it to a vacuum drying oven, and dry at 85℃ for 9h to obtain lignin phenolic prepolymer.

[0077] Step 2: Preparation of palladium-modified graphene oxide

[0078] Weigh out 0.5 g of palladium chloride and dissolve it in 0.5 mL of 37 wt% concentrated hydrochloric acid and 50 mL of deionized water to obtain an aqueous solution of palladium chloride.

[0079] Weigh 25g of hexadecyltrimethylammonium bromide and 10g of graphene oxide and add them to a reaction vessel containing 450mL of deionized water. After ultrasonic dispersion for 50min, add 55mL of palladium chloride aqueous solution and add 4.8wt% sodium hydroxide solution dropwise to adjust the pH of the system to 10. Then add 70mL of 2wt% ascorbic acid aqueous solution and stir at 65℃ for 3.5h. After the reaction is complete, filter and wash the filter cake twice with deionized water and anhydrous ethanol, respectively. Then transfer it to a vacuum drying oven and dry it at 70℃ to constant weight to obtain palladium-modified graphene oxide.

[0080] Step 3: Preparation of precursor composite liquid

[0081] Weigh out 60 parts by weight of the iron-modified nitrogen-enriched zinc heterocyclic framework prepared in Example 2, 32 parts of lignin phenolic prepolymer and 9 parts of palladium-modified graphene oxide, and add them to a reactor containing 900 mL of 50 wt% ethanol aqueous solution. After ultrasonic dispersion for 25 min, stir at 35 °C for 2.5 h to obtain the precursor composite solution.

[0082] Step 4: Prepare the molding substrate

[0083] 100 mL of 10 wt% melamine ethanol dispersion was added to the precursor composite solution. After stirring at 65 °C for 2.5 h, the temperature was raised to 95 °C and reacted for 3.5 h. The mixture was then evaporated and concentrated at 105 °C to a solid content of 55 wt%. The mixture was then pressed into shape at 12 MPa and transferred to a drying oven. It was then dried at 110 °C for 7.5 h to obtain the molded matrix.

[0084] Step 5: Preparation of porous carbon-based air-getter composite materials

[0085] The molded matrix was transferred to a tube furnace and heated to 550°C at a rate of 4°C / min under a nitrogen atmosphere. After holding at this temperature for 1.5 hours, the temperature was further increased to 850°C and held for another 1.5 hours. The matrix was then cooled to room temperature, removed, and pulverized. The powder was then uniformly mixed with 120g of KOH powder and transferred back to the tube furnace. The mixture was held at 750°C for 50 minutes and then rinsed twice with a 6wt% hydrochloric acid solution for 25 minutes each time. The mixture was then washed with deionized water until the washing solution was neutral. The matrix was then transferred to a drying oven and dried at 120°C to constant weight. Finally, it was annealed at 450°C to obtain a porous carbon-based gas-absorbing composite material.

[0086] Example 6

[0087] This embodiment provides a method for preparing a porous carbon-based air-getting composite material, including the following steps:

[0088] Step (1): Preparation of lignin-phenolic prepolymer

[0089] Weigh 80g of alkali lignin and 30g of phenol and add them to a reaction vessel containing 800mL of 50wt% ethanol aqueous solution and 80mL of 25wt% concentrated ammonia aqueous solution. Stir at 60℃ until completely dissolved, then add 70mL of 37wt% formaldehyde aqueous solution. React at 60℃ for 3h, then raise the temperature to 100℃ and react for 6h. After the reaction is complete, filter, wash the product 4 times with deionized water, transfer it to a vacuum drying oven, and dry at 90℃ for 10h to obtain lignin phenolic prepolymer.

[0090] Step 2: Preparation of palladium-modified graphene oxide

[0091] Weigh out 0.5 g of palladium chloride and dissolve it in 0.5 mL of 37 wt% concentrated hydrochloric acid and 50 mL of deionized water to obtain an aqueous solution of palladium chloride.

[0092] Weigh 25g of hexadecyltrimethylammonium bromide and 10g of graphene oxide and add them to a reaction vessel containing 500mL of deionized water. After ultrasonic dispersion for 60min, add 60mL of palladium chloride aqueous solution and add 4.8wt% sodium hydroxide solution dropwise to adjust the pH of the system to 10. Then add 80mL of 2wt% ascorbic acid aqueous solution and stir at 70℃ for 4h. After the reaction is completed, filter and wash the filter cake three times with deionized water and anhydrous ethanol, respectively. Then transfer it to a vacuum drying oven and dry it at 70℃ to constant weight to obtain palladium-modified graphene oxide.

[0093] Step 3: Preparation of precursor composite liquid

[0094] Weigh out 65 parts by weight of the iron-modified nitrogen-enriched zinc heterocyclic framework prepared in Example 3, 35 parts of lignin phenolic prepolymer and 10 parts of palladium-modified graphene oxide, and add them to a reactor containing 1000 mL of 50 wt% ethanol aqueous solution. After ultrasonic dispersion for 30 min, stir at 40 °C for 3 h to obtain the precursor composite solution.

[0095] Step 4: Prepare the molding substrate

[0096] 100 mL of 10 wt% melamine ethanol dispersion was added to the precursor composite solution. After stirring at 70 °C for 3 h, the temperature was raised to 100 °C and reacted for 4 h. The mixture was then evaporated and concentrated at 110 °C to a solid content of 60 wt%, and pressed into shape at 15 MPa. The mixture was then transferred to a drying oven and dried at 120 °C for 8 h to obtain the molded matrix.

[0097] Step 5: Preparation of porous carbon-based air-getter composite materials

[0098] The molded matrix was transferred to a tube furnace and heated to 600℃ at a rate of 5℃ / min under a nitrogen atmosphere and held for 2 hours. Then, the temperature was increased to 900℃ and held for 2 hours. After cooling to room temperature, the matrix was removed, pulverized, and the powder was mixed evenly with 120g of KOH powder. The mixture was then transferred to a tube furnace and held at 800℃ for 60 minutes. The matrix was then washed three times with a 6wt% hydrochloric acid solution for 30 minutes each time, followed by washing with deionized water until the washing solution was neutral. The matrix was then transferred to a drying oven and dried at 120℃ to constant weight. Finally, it was annealed at 500℃ to obtain a porous carbon-based gas-absorbing composite material.

[0099] Comparative Example 1

[0100] The difference between this comparative example and Example 6 is that step ii is omitted, and the three-dimensional zinc-based nitrogen-enriched porous lattice prepared in step i is used to replace the iron-modified nitrogen-enriched zinc heterocyclic framework in step (3).

[0101] Comparative Example 2

[0102] The difference between this comparative example and Example 6 is that steps i and i are omitted, and the iron-modified nitrogen-enriched zinc heterocyclic skeleton in step (3) is replaced with commercially available ZIF-8.

[0103] Comparative Example 3

[0104] The difference between this comparative example and Example 6 is that step (1) is omitted, and the lignin phenolic prepolymer in step (3) is replaced with commercially available phenolic resin.

[0105] Example 4

[0106] The difference between this comparative example and Example 6 is that step (2) is omitted, and the graphene oxide in step (2) is used instead of the palladium-modified graphene oxide in step (3).

[0107] Performance testing:

[0108] Referring to standard GB / T 25497-2010 "Test Method for Gas Absorption and Desorption Performance of Getters", the initial gas absorption rate, gas absorption rate after 30 min, and gas absorption capacity within 120 min of the porous carbon-based getter composite materials prepared in Examples 4-6 and Comparative Examples 1-4 were determined.

[0109] Referring to standard GB / T 19587-2017 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method", the specific surface area per unit mass of porous carbon-based gas-absorbing composite materials prepared in Examples 4-6 and Comparative Examples 1-4 was determined. The specific test results are shown in Table 1 below:

[0110] Table 1 - Performance Test Data of Samples

[0111]

[0112] Data Analysis:

[0113] Comparative analysis of the data in Table 1 above shows that the porous carbon-based air-getting composite material prepared in this invention has an initial air-getting rate of 2.35 cm⁻¹. 3 ·s -1 ·cm 2 The inspiratory rate over 30 minutes was 2.11 cm. 3 ·s -1 ·cm 2 The inspiratory capacity at 120 min was 9123 Pa·mL·g. -1 The specific surface area is 3056 m² / g;

[0114] Comparative Example 1, by omitting the iron modification step and directly using a three-dimensional zinc-based nitrogen-enriched porous lattice to replace the iron-modified nitrogen-enriched zinc heterocyclic framework, lacked the introduction of iron species into the framework, thus failing to form Fe-Nx coordination active sites and losing the synergistic catalytic adsorption effect of iron and nitrogen. Simultaneously, the regulatory effect of iron ion exchange and coordination modification on the pore structure also disappeared, resulting in a significant decrease in both the porosity and adsorption activity of the material. Compared to Example 6, the specific surface area of ​​Comparative Example 1 decreased from 3056 m² / g to 2344 m² / g, and the initial uptake rate decreased from 2.35 cm⁻¹. 3 ·s -1 ·cm 2 Reduced to 1.64cm 3 ·s -1 ·cm 2 The inspiratory rate decreased from 2.11 cm in 30 minutes. 3 ·s -1 ·cm 2 It dropped to 1.43cm 3 ·s -1 ·cm 2 The inspiratory capacity increased from 9123 Pa·mL·g in 120 minutes. -1 Reduced to 7231 Pa·mL·g -1 ;

[0115] Comparative Example 2 used commercially available ZIF-8 instead of the self-made iron-modified nitrogen-enriched zinc heterocyclic framework of this invention, resulting in a simplified nitrogen coordination environment for the framework. It lacked various nitrogen-containing coordination sites such as pyridine nitrogen, triazole nitrogen, and amino nitrogen. Simultaneously, it completely lacked the iron-modifying component, making it impossible to form an Fe-Nx active structure. Furthermore, the pore structure and pyrolysis behavior of ZIF-8 differed significantly from the framework of this invention, making it difficult to form a hierarchical porous structure during carbonization. This led to a comprehensive decrease in the specific surface area and adsorption performance of the material. Compared to Example 6, the specific surface area of ​​Comparative Example 2 decreased from 3056 m² / g to 1918 m² / g, and the initial uptake rate decreased from 2.35 cm⁻¹. 3 ·s -1 ·cm 2 Reduced to 1.48cm 3 ·s -1 ·cm 2 The inspiratory rate decreased from 2.11 cm in 30 minutes. 3 ·s -1 ·cm 2 Reduced to 1.25cm 3 ·s -1 ·cm 2 The inspiratory capacity increased from 9123 Pa·mL·g in 120 minutes. -1 Reduced to 6547 Pa·mL·g -1 ;

[0116] Comparative Example 3, by using commercially available phenolic resin instead of lignin-based phenolic prepolymer, resulted in the lack of lignin structural units in the carbon source component. This led to decreased uniformity of carbon layer growth during carbonization, and the absence of abundant functional groups from lignin. Consequently, the hydrogen bonds and π-π interactions between the resin and the iron-modified nitrogen-rich zinc heterocyclic framework and palladium-modified graphene oxide were weakened, resulting in decreased interfacial bonding. This, in turn, affected the orderly development of the pore structure and the synergistic effect among the components during activation. Compared to Example 6, the specific surface area of ​​Comparative Example 3 decreased from 3056 m² / g to 2152 m² / g, and the initial uptake rate decreased from 2.35 cm⁻¹. 3 ·s -1 ·cm 2 Reduced to 1.25cm 3 ·s -1 ·cm 2 The inspiratory rate decreased from 2.11 cm in 30 minutes. 3 ·s -1 ·cm 2 It dropped to 1.08cm 3 ·s -1 ·cm 2 The inspiratory capacity increased from 9123 Pa·mL·g in 120 minutes. -1 Reduced to 7034 Pa·mL·g -1 ;

[0117] Comparative Example 4, by using pure graphene oxide instead of palladium-modified graphene oxide, lacked the catalytic dissociation and adsorption effect of palladium nanoparticles, thus failing to produce a catalytic activation effect on gas molecules. This resulted in a significant decrease in gas adsorption kinetics. Simultaneously, the effect of palladium nanoparticles as physical barriers to inhibit carbon layer stacking and aggregation also disappeared, and the lack of additional chemisorption centers provided by palladium active sites led to a significant reduction in both adsorption rate and adsorption capacity. Compared to Example 6, the specific surface area of ​​Comparative Example 4 decreased from 3056 m² / g to 2564 m² / g, and the initial gas inhalation rate decreased from 2.35 cm⁻¹. 3 ·s -1 ·cm 2 It dropped to 1.02cm 3 ·s -1 ·cm 2 The inspiratory rate decreased from 2.11 cm in 30 minutes. 3 ·s -1 ·cm 2 Reduced to 0.88cm 3 ·s -1 ·cm 2 The inspiratory capacity increased from 9123 Pa·mL·g in 120 minutes. -1 Reduced to 7586 Pa·mL·g -1 .

[0118] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A porous carbon-based air-getting composite material, characterized in that, It comprises the following components by weight: 55-65 parts iron-modified nitrogen-enriched zinc heterocyclic framework, 30-35 parts lignin phenolic prepolymer and 8-10 parts palladium-modified graphene oxide; The iron-modified nitrogen-enriched zinc heterocyclic skeleton was prepared by coordination self-assembly of zinc nitrate hexahydrate, pyridine-3,5-dicarboxylic acid and 3-amino-1,2,4-triazole, followed by ion exchange and coordination modification with ferric nitrate nonahydrate. The lignin-phenolic prepolymer is prepared by alkali lignin, phenol and formaldehyde through alkali-catalyzed hydroxymethylation and condensation polymerization reaction. The palladium-modified graphene oxide is prepared by adsorbing and loading graphene oxide with palladium chloride, followed by reduction with ascorbic acid, so that palladium nanoparticles are loaded in situ onto the surface of graphene oxide.

2. The porous carbon-based air-absorbing composite material according to claim 1, characterized in that, The iron-modified nitrogen-enriched zinc heterocyclic framework was prepared by the following steps: A1. Add zinc nitrate hexahydrate, pyridine-3,5-dicarboxylic acid, and 3-amino-1,2,4-triazole to a mixed solution containing N,N-dimethylformamide and deionized water. Stir until completely dissolved, then add triethylamine and continue stirring for 5-10 minutes. Transfer the mixed solution to a polytetrafluoroethylene-lined reactor and react at 80-90℃ for 60-72 hours. After post-treatment, a three-dimensional zinc-based nitrogen-enriched porous lattice is obtained. A2. A three-dimensional zinc-based nitrogen-enriched porous lattice was added to a reactor containing N,N-dimethylformamide. After ultrasonic dispersion for 20-30 min, an aqueous solution of ferric nitrate nonahydrate was added and stirred for 20-30 min. The mixed solution was then transferred to a polytetrafluoroethylene-lined reactor and reacted at 80-90℃ for 20-24 h. After post-treatment, an iron-modified nitrogen-enriched zinc heterocyclic framework was obtained.

3. The porous carbon-based air-absorbing composite material according to claim 2, characterized in that, In step A1, the ratio of zinc nitrate hexahydrate, pyridine-3,5-dicarboxylic acid, and 3-amino-1,2,4-triazole added to a solution containing N,N-dimethylformamide, deionized water, and triethylamine is 0.9 g:0.5 g:0.25 g:36-40 mL:3 mL:0.2 mL; in step A2, the ratio of the three-dimensional zinc-based nitrogen-enriched porous lattice, N,N-dimethylformamide, and ferric nitrate nonahydrate aqueous solution is 1 g:35-40 mL:8-10 mL, and the mass fraction of the ferric nitrate nonahydrate aqueous solution is 3%.

4. The porous carbon-based air-absorbing composite material according to claim 1, characterized in that, The preparation method of the lignin phenolic prepolymer is as follows: alkali lignin and phenol are added to a reaction vessel containing an aqueous ethanol solution and a concentrated ammonia solution. After stirring at 50-60°C until completely dissolved, an aqueous formaldehyde solution is added. After reacting at 50-60°C for 2-3 hours, the temperature is raised to 80-100°C and reacted for 5-6 hours. After post-treatment, the lignin phenolic prepolymer is obtained.

5. The porous carbon-based air-absorbing composite material according to claim 4, characterized in that, The ratio of the amount of alkali lignin, phenol, aqueous ethanol solution, aqueous concentrated ammonia solution and aqueous formaldehyde solution is 8g:2-3g:70-80mL:7-8mL:7mL, wherein the mass fraction of the aqueous ethanol solution is 50%, the mass fraction of the aqueous concentrated ammonia solution is 25%, and the mass fraction of the aqueous formaldehyde solution is 37%.

6. The porous carbon-based air-absorbing composite material according to claim 1, characterized in that, The method for preparing palladium-modified graphene oxide is as follows: hexadecyltrimethylammonium bromide and graphene oxide are added to a reaction vessel containing deionized water and ultrasonically dispersed for 40-60 min. Then, an aqueous solution of palladium chloride is added, and sodium hydroxide solution is added dropwise to adjust the pH of the system to 10. Subsequently, an aqueous solution of ascorbic acid is added, and the mixture is stirred at 60-70℃ for 3-4 h. After post-treatment, palladium-modified graphene oxide is obtained.

7. The porous carbon-based air-absorbing composite material according to claim 6, characterized in that, The ratio of hexadecyltrimethylammonium bromide, graphene oxide, deionized water, palladium chloride aqueous solution, and ascorbic acid aqueous solution is 2.5g:1g:40-50mL:5-6mL:6-8mL, the mass fraction of the ascorbic acid aqueous solution is 2%, and the mass fraction of the sodium hydroxide solution is 4.8%. The palladium chloride aqueous solution is obtained by dissolving 0.05g of palladium chloride in 0.05mL of 37wt% concentrated hydrochloric acid and 5mL of deionized water.

8. A method for preparing a porous carbon-based air-getting composite material according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Add lignin phenolic prepolymer, iron-modified nitrogen-enriched zinc heterocyclic framework and palladium-modified graphene oxide to a reaction vessel containing an aqueous ethanol solution, ultrasonically disperse for 20-30 min, and stir at 30-40℃ for 2-3 h to obtain precursor composite liquid. S2. Add melamine ethanol dispersion to the precursor composite liquid, stir at 60-70℃ for 2-3 hours, then heat to 90-100℃ and react for 3-4 hours. Then evaporate and concentrate at 100-110℃ to a solid content of 50-60wt%, press into shape at 10-15MPa, and then transfer to a drying oven to dry at 100-120℃ for 7-8 hours to obtain the molded matrix. S3. Transfer the molded matrix to a tube furnace and heat it to 500-600℃ at a rate of 3-5℃ / min under a nitrogen atmosphere. Hold the temperature for 1-2 hours, then continue heating to 800-900℃ and hold for 1-2 hours. Cool to room temperature, remove and crush the matrix, mix the powder evenly with KOH powder, and then transfer it to a tube furnace. Hold the mixture at 700-800℃ for 40-60 minutes, then wash it 2-3 times with hydrochloric acid solution for 20-30 minutes each time. Wash it with deionized water until the washing solution is neutral, transfer it to a drying oven, dry it at 120℃ to constant weight, and then anneal it at 400-500℃ to obtain a porous carbon-based gas-absorbing composite material.

9. The method for preparing a porous carbon-based air-absorbing composite material according to claim 8, characterized in that, In step S1, the ethanol aqueous solution has a mass fraction of 50% and the amount of ethanol aqueous solution used is 800-1000 mL; in step S2, the melamine ethanol dispersion has a mass fraction of 10% and the amount of melamine ethanol dispersion used is 100 mL; in step S3, the amount of KOH powder used is 120 g and the mass fraction of hydrochloric acid solution is 6%.

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