A MOF composite adsorbent for VOC adsorption and its preparation method

Abstract

This invention discloses a MOF composite adsorbent material for VOC adsorption and its preparation method, relating to the field of environmental protection materials technology. The MOF composite adsorbent material for VOC adsorption consists of graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel and KIT-6@polyacrylate core-shell composite emulsion. Attaching the KIT-6@polyacrylate core-shell composite to the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel provides additional mesoporous space, enhancing the adsorption capacity. The polyacrylate segments further enhance the affinity for nonpolar VOCs, achieving broad-spectrum and efficient adsorption performance. Furthermore, the polyacrylate layer constructs a hydrophobic barrier on the framework surface, inhibiting competitive adsorption of water molecules. Its physical adhesion also anchors KIT-6 particles and MOF crystals to the framework, reducing particle aggregation and detachment, and enhancing adsorption stability in humid environments.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection materials technology, specifically referring to a MOF composite adsorbent material for VOC adsorption and its preparation method. Background Technology

[0002] While the social economy is developing rapidly, a large amount of gaseous pollutants are emitted into the atmosphere. Among them, volatile organic compounds (VOCs) are a major category of pollutants, encompassing various organic compounds such as alkanes, aromatics, aldehydes, ketones, and esters. VOCs not only cause serious damage to the ecological environment but also pose a significant threat to human health. First, they are important precursors to the formation of smog and ozone, and can react with nitrogen oxides under sunlight to trigger photochemical smog. Second, most VOCs are irritating or toxic, and some (such as benzene) are even classified as carcinogens. Long-term exposure to high concentrations of VOCs can easily lead to "sick building syndrome." It is worth noting that in industries such as chemical and spraying, emitted VOCs (such as benzene and gasoline vapor) are actually recyclable resources that can be utilized through adsorption materials. Among many treatment technologies, adsorption has become one of the most commonly used VOC removal methods due to its high economic efficiency and simple operation.

[0003] The existing technology currently has the following main problems:

[0004] Conventional adsorption materials generally have poor adsorption performance and are not stable in humid environments, which further limits their adsorption and removal efficiency for VOCs. Summary of the Invention

[0005] In view of the above situation and to overcome the defects of the prior art, the present invention proposes a MOF composite adsorbent material for VOC adsorption, comprising the following components in parts by weight: 5-10 parts of graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel, and 10-40 parts of KIT-6@polyacrylate core-shell composite emulsion.

[0006] The graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel comprises the following components in parts by weight: 9-12 parts graphene oxide, 21-24 parts cerium-based metal-organic framework, and 64-70 parts aminated modified nanocellulose.

[0007] The preparation method of the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel specifically includes the following steps:

[0008] (1) Add hexadecyltrimethoxysilane to 300 mL of anhydrous ethanol to form a hexadecyltrimethoxysilanol solution for later use. Weigh 3.0-4.0 g of nanocellulose and add it to 70 mL of deionized water. Stir mechanically at 300-400 rpm for 20-30 min. Then, use a constant pressure dropping funnel to add it dropwise to the hexadecyltrimethoxysilanol solution at a rate of 1 drop / second. After the addition is complete, adjust the pH to 8.0-9.0 with ammonia water. Stir the reaction in a 40℃ water bath for 6-12 h. Centrifuge and wash the precipitate 3-5 times with ethanol, then wash it twice with deionized water. Then redisperse it in 200 mL of deionized water. Nanocellulose is used as a rigid The hydrophilic core provides the main framework and mechanical strength of the material. The hexadecyl long chain grafted by chemical bonds forms a dense hydrophobic layer on the surface of cellulose. This not only enhances the affinity of hydrophobic VOCs, making it easier for VOC molecules to be captured from the air and adsorbed onto the material surface, but also provides additional adsorption space for VOC molecules through the organic interface layer formed by the long-chain alkanes. At the same time, the hydrophobic modification treatment inhibits the competitive adsorption of water molecules on the hydrophilic sites of nanocellulose, improves the anti-swelling property of nanocellulose, and ensures that its three-dimensional porous structure remains stable in a humid environment, ensuring that the diffusion channels of VOC molecules are always unobstructed, resulting in a modified nanocellulose solution.

[0009] (2) Add graphene oxide to 50 mL of deionized water, sonicate for 60-90 min while cooling in an ice bath to form a graphene oxide dispersion. Under 200 W power ice bath sonication conditions, slowly add the modified nanocellulose solution described in step (1) to the graphene oxide dispersion and mix. After the addition is complete, continue sonication for 10-20 min and stir at room temperature for 2-4 h to form a composite dispersion. Then slowly add 0.6-0.8 mL of 3-aminopropyltriethoxysilane to the composite dispersion and react at room temperature for 4-6 h. Grafted hexadecyl long-chain nanocellulose serves as a spacer and reinforcing phase, interspersed between the graphene oxide sheets. After the ethoxy group at one end of propyltriethoxysilane is hydrolyzed, graphene oxide and modified nanocellulose are covalently linked together. This not only enhances the richness of the pore structure and facilitates the rapid diffusion and transport of VOC molecules, but also ensures that the pore structure is not easily swollen or disintegrated after absorbing water, thus maintaining the integrity of the pore structure in a humid environment. The large number of amino groups introduced on the material surface and inside the pores result in the simultaneous presence of hydrophobic alkyl chains and hydrophilic amino groups on the material surface, forming an amphiphilic surface. Through hydrophobic interaction sites, π-π stacking interactions, and chemisorption, the synergistic adsorption performance of hydrophobic and hydrophilic VOCs is improved, resulting in an aminated modified nanocellulose solution.

[0010] (3) Take 20 mL of the aminated modified nanocellulose solution described in step (2) and mix it with 20 mL of 0.5% bovine serum albumin solution. Under ice bath conditions, homogenize and emulsify at 8000-10000 rpm for 2-3 min. Slowly add 20 mL of n-hexane to form a preliminary emulsion and transfer it to a sealed container. Under ice bath conditions, ultrasonically emulsify and crosslink at 150 W power for 15-20 min. Then, slowly add 1.5-2.5 mL of 100 mmol / L cerium nitrate solution and 1.5 mL of 200 mmol / L trimesoyl alcohol solution. Stir the reaction at 100-200 rpm at room temperature for 2-3 h. Then, centrifuge at 3000-4000 rpm for 3-5 min, collect the intermediate emulsion layer, and pre-treat at -20℃. After freezing for 24 hours, the material was finally placed in a freeze dryer and freeze-dried at -60℃ for 36 hours. In this process, cerium-based metal-organic frameworks (MOFs) are grown in situ on the framework and pores of aminated modified cellulose nanofibers. The physical entanglement between the cellulose nanofibers provides a stable mechanical framework. The two work together to form an aerogel with a multi-level porous structure, which not only facilitates the diffusion of VOC molecules, but also significantly improves the adsorption capacity for complex VOC molecules through multiple adsorption centers such as hydrophobic, hydrophilic, π-π stacking interactions, and coordination unsaturated sites. Furthermore, the cerium-based MOF crystals partially fill the hydrophilic pores of the aerogel, further enhancing the adsorption stability of the material in a humid environment, resulting in a graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel.

[0011] Preferably, in step (1), the amount of hexadecyltrimethoxysilane added is 10.0-20.0g. The hexadecyl long chain has extremely low surface energy and strong hydrophobicity, which can enhance the affinity for hydrophobic VOCs and can also act as a hydrophobic layer to protect the skeleton structure of nanocellulose, so that it can maintain its original shape and stacking structure in a humid environment and the pores will not shrink or close due to water absorption.

[0012] Preferably, in step (2), the amount of graphene oxide added is 0.4-0.8g. The addition of graphene oxide will improve the adsorption mechanism from a single surface coverage to a spatial network capture. It can also form a strong π-π stacking effect with common aromatic VOCs, achieving specific and efficient capture of aromatic pollutants. At the same time, as a highly rigid two-dimensional framework, graphene oxide inhibits the swelling and pore collapse of the material after adsorbing water through physical barriers and pore support, ensuring the adsorption performance of the material in a humid environment.

[0013] This invention also provides a method for preparing MOF composite adsorbent materials for VOC adsorption, specifically including the following steps:

[0014] S1. Place KIT-6 cubic mesoporous molecular sieves with pore size of 3-7 nm in a muffle furnace and calcine at 500-550℃ for 5-6 hours. Remove, cool to room temperature, grind, and make the sieve mesh size 100-200 mesh. After activation treatment, the three-dimensional cubic double helix pore structure of KIT-6 is fully exposed, and the pores are interconnected. This three-dimensional interconnected network provides the shortest diffusion path for VOC molecules from the material surface to the interior. Its huge surface area and pore volume become effective adsorption space. During the activation process, silanol condenses to form Si-O-Si bonds, making the pore wall structure more compact and further enhancing the stability of the framework. This ensures that the adsorption channels can remain unobstructed in a humid environment, thus obtaining activated KIT-6 cubic mesoporous molecular sieves.

[0015] S2. Add 1.0-1.2g sodium dodecyl sulfate, 0.2g sodium bicarbonate, and 60mL deionized water to a 500mL four-necked flask. Then add the activated KIT-6 cubic mesoporous molecular sieve described in step S1. Immediately place the flask in an ice-water bath and ultrasonically disperse for 30-60min. Then place the flask on a magnetic stirrer, purge with nitrogen, and stir at 150-170rpm for 0.5-1h at room temperature. Subsequently, place the flask in a 75℃ oil bath and simultaneously add the acrylate mixed monomers and 20g of 0.5% potassium persulfate aqueous solution using a constant pressure dropping funnel, controlling the monomer concentration at 0.5%. The potassium persulfate aqueous solution was added over 1.0-1.5 hours. After the addition was complete, the system was kept at a constant temperature for 5-6 hours, then cooled to room temperature. The solution was filtered through a 200-mesh filter cloth, and the filtrate was collected. The polyacrylate shell layer was wrapped around the surface of the activated KIT-6 cubic mesoporous molecular sieve. The adsorption performance was improved by introducing multiple chemical adsorption sites. At the same time, the polyacrylate layer on the surface acted as a physical barrier, slowing down or blocking the direct contact between water molecules and the silanol groups on the KIT-6 surface, thereby improving the adsorption stability of the material in a humid environment, resulting in a KIT-6@polyacrylate core-shell composite emulsion.

[0016] S3. Immerse the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel into the KIT-6@polyacrylate core-shell composite emulsion described in step S2, transfer it to a vacuum desiccator, maintain it under a vacuum of -0.1 MPa for 20-30 min, remove the vacuum, and place it on a shaker at 100-200 rpm for 1-2 h. Remove it, gently blot the surface liquid off the loaded aerogel with filter paper, pre-freeze it in a -20℃ freezer for 12-24 h, and then transfer it to a freeze dryer at -80℃. Freeze-drying for 48-72 hours resulted in the KIT-6@polyacrylate core-shell composite being attached to graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel, providing additional mesoporous space and enhancing adsorption capacity. The polyacrylate segments further enhanced the affinity for nonpolar or weakly polar VOCs, achieving broad-spectrum and efficient adsorption performance. Simultaneously, the constructed hydrophobic barrier layer suppressed the competitive adsorption of water molecules, enhancing structural stability under humid conditions, thus yielding a MOF composite adsorbent material for VOC adsorption.

[0017] Preferably, in step S1, the amount of KIT-6 cubic mesoporous molecular sieve added is 15.0-25.0g. KIT-6 has thick mesoporous pore walls and excellent hydrothermal and mechanical stability.

[0018] Preferably, in step S2, the acrylate mixed monomers are 2g methyl methacrylate, 3g butyl acrylate, and 0.5g acrylic acid. The ternary system of methyl methacrylate, butyl acrylate, and acrylic acid forms a polyacrylate layer after free radical copolymerization. This not only introduces adsorption sites for hydrogen bonding and acid-base interactions, but also anchors water molecules in local hydrophilic microregions through a microphase separation structure composed of hydrophobic and hydrophilic segments, preventing them from spreading on the material surface to form a continuous water film. This avoids non-selective blocking of all VOCs caused by water film coverage.

[0019] The beneficial effects achieved by this invention are as follows:

[0020] This invention provides additional mesoporous space by attaching a KIT-6@polyacrylate core-shell composite to a graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel, significantly improving adsorption capacity. The polyacrylate segments further enhance the affinity for nonpolar VOCs, achieving broad-spectrum and highly efficient adsorption performance. Furthermore, the polyacrylate layer constructs a hydrophobic barrier on the framework surface, inhibiting competitive adsorption of water molecules. Its physical adhesion also anchors KIT-6 particles and MOF crystals to the framework, reducing particle aggregation and detachment, and enhancing adsorption capacity in humid environments. Adsorption stability; In the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel, the cerium-based metal-organic framework (MOF) serves as a highly active adsorption site, growing in situ on the framework and pores of the aminated cellulose nanofibers. Simultaneously, the physical entanglement between the cellulose nanofibers provides a stable mechanical framework. The synergistic effect of these two elements forms an aerogel with a hierarchical porous structure, which not only facilitates the diffusion of VOC molecules but also significantly enhances the adsorption capacity for complex VOC molecules through multi-functional adsorption centers such as hydrophobic, hydrophilic, π-π stacking interactions, and coordination unsaturated sites. Furthermore, the in-situ grown cerium-based metal-organic framework (MOF) crystals can partially fill hydrophilic pores, reducing the overall water absorption rate of the material and further enhancing its adsorption stability in humid environments. In the KIT-6@polyacrylate core-shell composite emulsion, the polyacrylate shell layer coats the surface of the activated KIT-6 cubic mesoporous molecular sieve, optimizing the pore structure and diffusion path without clogging the internal pores. This introduces multiple chemisorption sites, improving adsorption performance. Simultaneously, the surface polyacrylate layer acts as a physical barrier, slowing down or blocking the direct contact between water molecules and the silanol groups on the KIT-6 surface. Furthermore, it can effectively bond KIT-6 particles together through film formation and form a flexible protective layer on the particle surface, greatly enhancing the overall mechanical strength and water resistance of the material, thereby improving the adsorption stability of the material in humid environments. This invention uses graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel and KIT-6@polyacrylate core-shell composite emulsion to prepare a MOF composite adsorbent material for VOC adsorption, which not only improves the adsorption performance of VOCs, but also improves the adsorption stability of the material in humid environments and optimizes the adsorption effect. Attached Figure Description

[0021] Figure 1 The graph shows the VOC removal rate results of Examples 1-4 and Comparative Examples 1-3 of this invention;

[0022] Figure 2 The results of humidity stability coefficients for Examples 1-4 and Comparative Examples 1-3 of the present invention are shown in the figure. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0025] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; unless otherwise specified, the experimental materials used in the following embodiments are all purchased from commercial channels.

[0026] Example 1

[0027] This embodiment proposes a MOF composite adsorbent material for VOC adsorption, comprising the following components in parts by weight: 7.5 parts of graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel and 25 parts of KIT-6@polyacrylate core-shell composite emulsion.

[0028] A graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel, comprising the following components in parts by weight: 10.5 parts graphene oxide, 22.5 parts cerium-based metal-organic framework, and 66 parts aminated cellulose nanofiber.

[0029] The preparation method of graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel includes the following steps:

[0030] (1) Add hexadecyltrimethoxysilane to 300 mL of anhydrous ethanol. The amount of hexadecyltrimethoxysilane added is 15.0 g. The long chain of hexadecyl has extremely low surface energy and strong hydrophobicity, which can enhance the affinity for hydrophobic VOCs. It can also act as a hydrophobic layer to protect the framework structure of nanocellulose, so that it can maintain its original shape and stacking structure in a humid environment. The pores will not shrink or close due to water absorption, forming a hexadecyltrimethoxysilanol solution for later use. Weigh 3.5 g of nanocellulose and add it to 70 mL of deionized water. Stir mechanically at 350 rpm for 25 min. Then, use a constant pressure dropping funnel to add it dropwise to the hexadecyltrimethoxysilanol solution at a rate of 1 drop / second. After the addition is completed, adjust the pH to 8.5 with ammonia water. Stir the reaction in a 40 °C water bath for 9 h. Centrifuge and collect the precipitate. The material was first washed four times with ethanol, then twice with deionized water, and then redispersed in 200 mL of deionized water. Nanocellulose, as a rigid hydrophilic core, provides the main framework and mechanical strength of the material. The hexadecyl long chain grafted by chemical bonds forms a dense hydrophobic layer on the surface of cellulose, which not only enhances the affinity of hydrophobic VOCs, making it easier for VOC molecules to be captured from the air and adsorbed onto the material surface, but also provides additional adsorption space for VOC molecules through the organic interface layer formed by the long-chain alkanes. At the same time, the hydrophobic modification treatment inhibits the competitive adsorption of water molecules on the hydrophilic sites of nanocellulose, improves the anti-swelling property of nanocellulose, and ensures that its three-dimensional porous structure remains stable in a humid environment, ensuring that the diffusion channels of VOC molecules are always unobstructed, thus obtaining a modified nanocellulose solution.

[0031] (2) Add graphene oxide to 50 mL of deionized water. The amount of graphene oxide added is 0.6 g. The addition of graphene oxide will improve the adsorption mechanism from a single surface coverage to a spatial network capture. It can also form a strong π-π stacking effect with common aromatic VOCs, so as to achieve specific and efficient capture of aromatic pollutants. At the same time, as a highly rigid two-dimensional framework, graphene oxide inhibits the swelling and pore collapse of the material after adsorbing water through physical barriers and pore support, thus ensuring the adsorption performance of the material in a humid environment. Ultrasonic dispersion for 75 min and ice bath cooling are used to form graphene oxide dispersion. Under the 200 W power ice bath ultrasonic condition, the modified nanocellulose solution described in step (1) is slowly added dropwise to the graphene oxide dispersion and mixed. After the addition is completed, ultrasonication is continued for 15 min, and stirring is carried out at room temperature for 3 h to form a composite dispersion. Then, the composite dispersion is added to the composite dispersion. 0.7 mL of 3-aminopropyltriethoxysilane was slowly added dropwise to the dispersion, and the reaction was carried out at room temperature for 5 h. Grafted hexadecyl long-chain nanocellulose served as a spacer and reinforcing phase, interspersed between the graphene oxide sheets. After the ethoxy group at one end of the 3-aminopropyltriethoxysilane was hydrolyzed, the graphene oxide and the modified nanocellulose were covalently linked together. This not only enhanced the richness of the pore structure and facilitated the rapid diffusion and transport of VOC molecules, but also ensured that the chemically cross-linked network was not easily swollen or disintegrated after absorbing water, thus ensuring the integrity of the pore structure in a humid environment. The large number of amino groups introduced on the material surface and inside the pores resulted in the simultaneous presence of hydrophobic alkyl chains and hydrophilic amino groups on the material surface, forming an amphiphilic surface. Through hydrophobic interaction sites, π-π stacking interactions, and chemisorption, the synergistic adsorption performance of hydrophobic and hydrophilic VOCs was improved, resulting in an aminated modified nanocellulose solution.

[0032] (3) Take 20 mL of the aminated modified nanocellulose solution described in step (2) and mix it with 20 mL of 0.5% bovine serum albumin solution. Under ice bath conditions, homogenize and emulsify at 9000 rpm for 2.5 min. Slowly add 20 mL of n-hexane to form a preliminary emulsion and transfer it to a sealed container. Under ice bath conditions, ultrasonically emulsify and crosslink at 150 W power for 17.5 min. Then, slowly add 2.0 mL of 100 mmol / L cerium nitrate solution and 1.5 mL of 200 mmol / L trimesoyl alcohol solution. Stir the reaction at 150 rpm at room temperature for 2.5 h. Then, centrifuge at 3500 rpm for 4 min, collect the intermediate emulsion layer, pre-freeze at -20℃ for 24 h, and finally place it in a freezer. The process involves freeze-drying at -60℃ for 36 hours using a dryer. In this process, cerium-based metal-organic frameworks (MOFs) are grown in situ on the framework and pores of aminated cellulose nanofibers. The physical entanglement between the cellulose nanofibers provides a stable mechanical framework. The two work synergistically to form an aerogel with a multi-level porous structure, which not only facilitates the diffusion of VOC molecules but also significantly enhances the adsorption capacity for complex VOC molecules through multiple adsorption centers such as hydrophobic, hydrophilic, π-π stacking interactions, and coordination unsaturated sites. Furthermore, the cerium-based MOF crystals partially fill the hydrophilic pores of the aerogel, further enhancing the adsorption stability of the material in humid environments, resulting in a graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel.

[0033] This embodiment provides a method for preparing MOF composite adsorbent material for VOC adsorption, specifically including the following steps:

[0034] S1. KIT-6 cubic mesoporous molecular sieve with a pore size of 5 nm was placed in a muffle furnace. The amount of KIT-6 cubic mesoporous molecular sieve added was 20.0 g. KIT-6 has thick mesoporous pore walls and excellent hydrothermal and mechanical stability. It was calcined at 525℃ for 5.5 h, taken out, cooled to room temperature, ground, and the sieve pore size was 150 mesh. After activation treatment, the three-dimensional cubic double helix pore structure of KIT-6 was fully exposed, and the pores were interconnected. This three-dimensional interconnected network provides the shortest diffusion path for VOC molecules from the material surface to the interior. Its huge surface area and pore volume become effective adsorption space. During the activation process, silanol condenses to form Si-O-Si bonds, making the pore wall structure more compact and further enhancing the stability of the framework. This ensures that the adsorption channels can remain unobstructed in a humid environment, thus obtaining activated KIT-6 cubic mesoporous molecular sieve.

[0035] S2. Add 1.1g sodium dodecyl sulfate, 0.2g sodium bicarbonate, and 60mL deionized water to a 500mL four-necked flask. Then add the activated KIT-6 cubic mesoporous molecular sieve described in step S1. Immediately place the flask in an ice-water bath and ultrasonically disperse for 45min. Then place the flask on a magnetic stirrer, purge with nitrogen, and stir at 160rpm for 0.75h at room temperature. Subsequently, place the flask in a 75℃ oil bath and simultaneously add acrylate mixed monomers and 20g of 0.5% potassium persulfate aqueous solution using a constant pressure dropping funnel. The acrylate mixed monomers are 2g methyl methacrylate, 3g butyl acrylate, and 0.5g acrylic acid. The ternary system of methyl methacrylate, butyl acrylate, and acrylic acid forms a polyacrylate layer after free radical copolymerization. This not only introduces adsorption sites for hydrogen bonding and acid-base interactions but also allows for the formation of hydrophobic and hydrophobic adsorption sites. The microphase separation structure composed of hydrophilic and aqueous segments anchors water molecules in local hydrophilic microregions, preventing them from spreading on the material surface to form a continuous water film. This avoids non-selective blocking of all VOCs caused by water film coverage. The monomer was added in 0.75 hours, and the potassium persulfate aqueous solution was added in 1.25 hours. After the addition was completed, the system was kept at a constant temperature for 5.5 hours, then cooled to room temperature, filtered with a 200-mesh filter cloth, and the filtrate was collected. The polyacrylate shell is wrapped around the surface of the activated KIT-6 cubic mesoporous molecular sieve, which improves the adsorption performance by introducing multiple chemical adsorption sites. At the same time, the polyacrylate layer on the surface acts as a physical barrier, slowing down or blocking the direct contact between water molecules and the silanol groups on the KIT-6 surface, thereby improving the adsorption stability of the material in a humid environment, resulting in a KIT-6@polyacrylate core-shell composite emulsion.

[0036] S3. Immerse the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel into the KIT-6@polyacrylate core-shell composite emulsion described in step S2, transfer it to a vacuum dryer, maintain it under a vacuum of -0.1 MPa for 25 min, remove the vacuum, and place it on a shaker to shake at 150 rpm for 1.5 h. Remove it, gently blot the surface liquid of the loaded aerogel with filter paper, pre-freeze it in a -20℃ freezer for 18 h, and then transfer it to a freeze dryer to freeze dry at -80℃ for 60 h. The KIT-6@polyacrylate core-shell composite adheres to the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel, providing additional mesoporous space and improving the adsorption capacity. The polyacrylate segments further enhance the affinity for non-polar or weakly polar VOCs, achieving broad-spectrum and efficient adsorption performance. At the same time, the constructed hydrophobic barrier layer inhibits the competitive adsorption of water molecules and enhances the structural stability under humid conditions, resulting in a MOF composite adsorbent material for VOC adsorption.

[0037] Example 2

[0038] This embodiment proposes a MOF composite adsorbent material for VOC adsorption, comprising the following components in parts by weight: 10 parts of graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel and 40 parts of KIT-6@polyacrylate core-shell composite emulsion.

[0039] A graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel, comprising the following components in parts by weight: 12 parts graphene oxide, 24 parts cerium-based metal-organic framework, and 64 parts aminated modified cellulose nanofiber.

[0040] The preparation method of graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel includes the following steps:

[0041] (1) Add hexadecyltrimethoxysilane to 300 mL of anhydrous ethanol. The amount of hexadecyltrimethoxysilane added is 20.0 g. The long chain of hexadecyl has extremely low surface energy and strong hydrophobicity, which can enhance the affinity for hydrophobic VOCs. It can also act as a hydrophobic layer to protect the skeleton structure of nanocellulose, so that it can maintain its original shape and stacking structure in a humid environment. The pores will not shrink or close due to water absorption, forming a hexadecyltrimethoxysilanol solution for later use. Weigh 4.0 g of nanocellulose and add it to 70 mL of deionized water. Stir mechanically at 400 rpm for 30 min. Then, use a constant pressure dropping funnel to add it dropwise to the hexadecyltrimethoxysilanol solution at a rate of 1 drop / second. After the addition is completed, adjust the pH to 9.0 with ammonia water. Stir the reaction in a 40 °C water bath for 12 h. Centrifuge and precipitate. The material was first washed five times with ethanol, then twice with deionized water, and then redispersed in 200 mL of deionized water. Nanocellulose, as a rigid hydrophilic core, provides the main framework and mechanical strength of the material. The hexadecyl long chain grafted by chemical bonds forms a dense hydrophobic layer on the surface of cellulose, which not only enhances the affinity of hydrophobic VOCs, making it easier for VOC molecules to be captured from the air and adsorbed onto the material surface, but also provides additional adsorption space for VOC molecules through the organic interface layer formed by the long-chain alkanes. At the same time, the hydrophobic modification treatment inhibits the competitive adsorption of water molecules on the hydrophilic sites of nanocellulose, improves the anti-swelling property of nanocellulose, and makes its three-dimensional porous structure stable in a humid environment, ensuring that the diffusion channels of VOC molecules are always unobstructed, thus obtaining a modified nanocellulose solution.

[0042] (2) Add graphene oxide to 50 mL of deionized water. The amount of graphene oxide added is 0.8 g. The addition of graphene oxide improves the adsorption mechanism from a single surface coverage to a spatial network capture. It can also form a strong π-π stacking effect with common aromatic VOCs, achieving specific and efficient capture of aromatic pollutants. At the same time, as a highly rigid two-dimensional framework, graphene oxide inhibits the swelling and pore collapse of the material after adsorbing water through physical barriers and pore support, ensuring the adsorption performance of the material in a humid environment. Ultrasonic dispersion for 90 min and ice bath cooling are used to form a graphene oxide dispersion. Under 200 W power ice bath ultrasonic conditions, the modified nanocellulose solution described in step (1) is slowly added dropwise to the graphene oxide dispersion and mixed. After the addition is completed, ultrasonication is continued for 20 min, and stirring is carried out at room temperature for 4 h to form a composite dispersion. Then, the composite dispersion is added to the composite dispersion. 0.8 mL of 3-aminopropyltriethoxysilane was slowly added dropwise to the dispersion, and the reaction was carried out at room temperature for 6 h. Grafted hexadecyl long-chain nanocellulose served as a spacer and reinforcing phase, interspersed between the graphene oxide sheets. After the ethoxy group at one end of the 3-aminopropyltriethoxysilane was hydrolyzed, the graphene oxide and the modified nanocellulose were covalently linked together. This not only enhanced the richness of the pore structure and facilitated the rapid diffusion and transport of VOC molecules, but also ensured that the chemically cross-linked network was not easily swollen or disintegrated after absorbing water, thus ensuring the integrity of the pore structure in a humid environment. The large number of amino groups introduced on the material surface and inside the pores resulted in the simultaneous presence of hydrophobic alkyl chains and hydrophilic amino groups on the material surface, forming an amphiphilic surface. Through hydrophobic interaction sites, π-π stacking interactions, and chemisorption, the synergistic adsorption performance of hydrophobic and hydrophilic VOCs was improved, resulting in an aminated modified nanocellulose solution.

[0043] (3) Take 20 mL of the aminated modified nanocellulose solution described in step (2) and mix it with 20 mL of 0.5% bovine serum albumin solution. Under ice bath conditions, homogenize and emulsify at 10,000 rpm for 3 min. Slowly add 20 mL of n-hexane to form a preliminary emulsion and transfer it to a sealed container. Under ice bath conditions, ultrasonically emulsify and crosslink at 150 W power for 20 min. Then, slowly add 2.5 mL of 100 mmol / L cerium nitrate solution and 1.5 mL of 200 mmol / L trimesoyl alcohol solution. Stir the reaction at 200 rpm for 3 h at room temperature. Then, centrifuge at 4000 rpm for 5 min, collect the intermediate emulsion layer, pre-freeze at -20℃ for 24 h, and finally freeze-dry. The process involves freeze-drying at -60℃ for 36 hours. In this process, cerium-based metal-organic frameworks (MOFs) are grown in situ on the framework and pores of aminated cellulose nanofibers. The physical entanglement between the cellulose nanofibers provides a stable mechanical framework. The two work synergistically to form an aerogel with a multi-level porous structure, which not only facilitates the diffusion of VOC molecules but also significantly enhances the adsorption capacity for complex VOC molecules through multiple adsorption centers such as hydrophobic, hydrophilic, π-π stacking interactions, and coordination unsaturated sites. Furthermore, the cerium-based MOF crystals partially fill the hydrophilic pores of the aerogel, further enhancing the adsorption stability of the material in humid environments, resulting in a graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel.

[0044] This embodiment provides a method for preparing MOF composite adsorbent material for VOC adsorption, specifically including the following steps:

[0045] S1. KIT-6 cubic mesoporous molecular sieve with a pore size of 7 nm was placed in a muffle furnace. The amount of KIT-6 cubic mesoporous molecular sieve added was 25.0 g. KIT-6 has thick mesoporous pore walls and excellent hydrothermal and mechanical stability. It was calcined at 550℃ for 6 h, taken out, cooled to room temperature, ground, and the sieve mesh size was 200 mesh. After activation treatment, the three-dimensional cubic double helix pore structure of KIT-6 was fully exposed, and the pores were interconnected. This three-dimensional interconnected network provides the shortest diffusion path for VOC molecules from the material surface to the interior. Its huge surface area and pore volume become effective adsorption space. During the activation process, silanol condenses to form Si-O-Si bonds, making the pore wall structure more compact and further enhancing the stability of the framework. This ensures that the adsorption channels can remain unobstructed in a humid environment, thus obtaining activated KIT-6 cubic mesoporous molecular sieve.

[0046] S2. Add 1.2g sodium dodecyl sulfate, 0.2g sodium bicarbonate, and 60mL deionized water to a 500mL four-necked flask. Then add the activated KIT-6 cubic mesoporous molecular sieve described in step S1. Immediately place the flask in an ice-water bath and ultrasonically disperse for 60min. Then place the four-necked flask on a magnetic stirrer, purge with nitrogen, and stir at 170rpm for 1h at room temperature. Subsequently, place the flask in a 75℃ oil bath and simultaneously add acrylate mixed monomers and 20g of 0.5% potassium persulfate aqueous solution using a constant pressure dropping funnel. The acrylate mixed monomers are 2g methyl methacrylate, 3g butyl acrylate, and 0.5g acrylic acid. The ternary system of methyl methacrylate, butyl acrylate, and acrylic acid forms a polyacrylate layer after free radical copolymerization. This not only introduces adsorption sites for hydrogen bonding and acid-base interactions, but also allows for... The microphase separation structure composed of hydrophobic and hydrophilic segments anchors water molecules in local hydrophilic microregions, preventing them from spreading on the material surface to form a continuous water film. This avoids non-selective blocking of all VOCs caused by water film coverage. The monomer was added over 1 hour, and the potassium persulfate aqueous solution was added over 1.5 hours. After the addition was completed, the system was kept at a constant temperature for 6 hours, then cooled to room temperature, filtered using a 200-mesh filter cloth, and the filtrate was collected. The polyacrylate shell is wrapped around the surface of the activated KIT-6 cubic mesoporous molecular sieve, which improves the adsorption performance by introducing multiple chemical adsorption sites. At the same time, the polyacrylate layer on the surface acts as a physical barrier, slowing down or blocking the direct contact between water molecules and the silanol groups on the KIT-6 surface, thereby improving the adsorption stability of the material in a humid environment, resulting in a KIT-6@polyacrylate core-shell composite emulsion.

[0047] S3. Immerse the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel in the KIT-6@polyacrylate core-shell composite emulsion described in step S2, transfer it to a vacuum dryer, maintain it under a vacuum of -0.1 MPa for 30 min, remove the vacuum, and place it on a shaker to shake at 200 rpm for 2 h. Remove it, gently blot the surface liquid of the loaded aerogel with filter paper, pre-freeze it in a -20℃ freezer for 24 h, and then transfer it to a freeze dryer to freeze dry at -80℃ for 48-72 h. The KIT-6@polyacrylate core-shell composite adheres to the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel, providing additional mesoporous space and improving the adsorption capacity. The polyacrylate segments further enhance the affinity for non-polar or weakly polar VOCs, achieving broad-spectrum and efficient adsorption performance. At the same time, the constructed hydrophobic barrier layer inhibits the competitive adsorption of water molecules and enhances the structural stability under humid conditions, resulting in a MOF composite adsorbent material for VOC adsorption.

[0048] Example 3

[0049] This embodiment proposes a MOF composite adsorbent material for VOC adsorption, comprising the following components in parts by weight: 5 parts of graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel and 10 parts of KIT-6@polyacrylate core-shell composite emulsion.

[0050] A graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel, comprising the following components in parts by weight: 9 parts graphene oxide, 21 parts cerium-based metal-organic framework, and 70 parts aminated modified cellulose nanofiber.

[0051] The preparation method of graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel includes the following steps:

[0052] (1) Add hexadecyltrimethoxysilane to 300 mL of anhydrous ethanol. The amount of hexadecyltrimethoxysilane added is 10.0 g. The long chain of hexadecyl has extremely low surface energy and strong hydrophobicity, which can enhance the affinity for hydrophobic VOCs. It can also act as a hydrophobic layer to protect the framework structure of nanocellulose, so that it can maintain its original shape and stacking structure in a humid environment. The pores will not shrink or close due to water absorption, forming a hexadecyltrimethoxysilanol solution for later use. Weigh 3.0 g of nanocellulose and add it to 70 mL of deionized water. Stir mechanically at 300 rpm for 20 min. Then, use a constant pressure dropping funnel to add it dropwise to the hexadecyltrimethoxysilanol solution at a rate of 1 drop / second. After the addition is completed, adjust the pH to 8.0 with ammonia water. Stir the reaction in a 40℃ water bath for 6 h. Centrifuge and collect the precipitate. The material was first washed three times with ethanol, then twice with deionized water, and then redispersed in 200 mL of deionized water. Nanocellulose, as a rigid hydrophilic core, provides the main framework and mechanical strength of the material. The hexadecyl long chain grafted by chemical bonds forms a dense hydrophobic layer on the surface of cellulose, which not only enhances the affinity of hydrophobic VOCs, making it easier for VOC molecules to be captured from the air and adsorbed onto the surface of the material, but also provides additional adsorption space for VOC molecules through the organic interface layer formed by the long-chain alkanes. At the same time, the hydrophobic modification treatment inhibits the competitive adsorption of water molecules on the hydrophilic sites of nanocellulose, improves the anti-swelling property of nanocellulose, and makes its three-dimensional porous structure stable in a humid environment, ensuring that the diffusion channels of VOC molecules are always unobstructed, thus obtaining a modified nanocellulose solution.

[0053] (2) Add graphene oxide to 50 mL of deionized water. The amount of graphene oxide added is 0.4 g. The addition of graphene oxide will improve the adsorption mechanism from a single surface coverage to a spatial network capture. It can also form a strong π-π stacking effect with common aromatic VOCs, so as to achieve specific and efficient capture of aromatic pollutants. At the same time, as a highly rigid two-dimensional framework, graphene oxide inhibits the swelling and pore collapse of the material after adsorbing water through physical barriers and pore support, thus ensuring the adsorption performance of the material in a humid environment. Ultrasonic dispersion for 60 min and ice bath cooling are used to form graphene oxide dispersion. Under the 200 W power ice bath ultrasonic conditions, the modified nanocellulose solution described in step (1) is slowly added dropwise to the graphene oxide dispersion and mixed. After the addition is completed, ultrasonication is continued for 10 min, and stirring is carried out at room temperature for 2 h to form a composite dispersion. Then, the composite dispersion is added to the composite dispersion. 0.6 mL of 3-aminopropyltriethoxysilane was slowly added dropwise to the dispersion, and the reaction was carried out at room temperature for 4 h. Grafted hexadecyl long-chain nanocellulose served as a spacer and reinforcing phase, interspersed between the graphene oxide sheets. After the ethoxy group at one end of the 3-aminopropyltriethoxysilane was hydrolyzed, the graphene oxide and the modified nanocellulose were covalently linked together. This not only enhanced the richness of the pore structure and facilitated the rapid diffusion and transport of VOC molecules, but also ensured that the chemically cross-linked network was not easily swollen or disintegrated after absorbing water, thus ensuring the integrity of the pore structure in a humid environment. The large number of amino groups introduced on the material surface and inside the pores resulted in the simultaneous presence of hydrophobic alkyl chains and hydrophilic amino groups on the material surface, forming an amphiphilic surface. Through hydrophobic interaction sites, π-π stacking interactions, and chemisorption, the synergistic adsorption performance of hydrophobic and hydrophilic VOCs was improved, resulting in an aminated modified nanocellulose solution.

[0054] (3) Take 20 mL of the aminated modified nanocellulose solution described in step (2) and mix it with 20 mL of 0.5% bovine serum albumin solution. Under ice bath conditions, homogenize and emulsify at 8000 rpm for 2 min. Slowly add 20 mL of n-hexane to form a preliminary emulsion and transfer it to a sealed container. Under ice bath conditions, ultrasonically emulsify and crosslink at 150 W power for 15 min. Then, slowly add 1.5 mL of 100 mmol / L cerium nitrate solution and 1.5 mL of 200 mmol / L trimesoyl alcohol solution. Stir at 100 rpm for 2 h at room temperature. Then, centrifuge at 3000 rpm for 3 min, collect the intermediate emulsion layer, pre-freeze at -20℃ for 24 h, and finally put it into a freeze dryer. In this process, cerium-based metal-organic frameworks (MOFs) are freeze-dried at -60℃ for 36 hours. In this process, cerium-based metal-organic frameworks (MOFs) are grown in situ on the framework and pores of aminated cellulose nanofibers. The physical entanglement between the cellulose nanofibers provides a stable mechanical framework. The two work synergistically to form an aerogel with a multi-level porous structure, which not only facilitates the diffusion of VOC molecules, but also significantly improves the adsorption capacity for complex VOC molecules through multiple adsorption centers such as hydrophobic, hydrophilic, π-π stacking interactions, and coordination unsaturated sites. Furthermore, the cerium-based MOF crystals partially fill the hydrophilic pores of the aerogel, further enhancing the adsorption stability of the material in humid environments, resulting in a graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel.

[0055] This embodiment provides a method for preparing MOF composite adsorbent material for VOC adsorption, specifically including the following steps:

[0056] S1. KIT-6 cubic mesoporous molecular sieve with a pore size of 3 nm was placed in a muffle furnace. The amount of KIT-6 cubic mesoporous molecular sieve added was 15.0 g. KIT-6 has thick mesoporous pore walls and excellent hydrothermal and mechanical stability. It was calcined at 500℃ for 5 h, taken out, cooled to room temperature, ground, and the sieve mesh size was 100 mesh. After activation treatment, the three-dimensional cubic double helix pore structure of KIT-6 was fully exposed, and the pores were interconnected. This three-dimensional interconnected network provides the shortest diffusion path for VOC molecules from the material surface to the interior. Its huge surface area and pore volume become effective adsorption space. During the activation process, silanol condenses to form Si-O-Si bonds, making the pore wall structure more compact and further enhancing the stability of the framework. This ensures that the adsorption channels can remain unobstructed in a humid environment, thus obtaining activated KIT-6 cubic mesoporous molecular sieve.

[0057] S2. Add 1.0g sodium dodecyl sulfate, 0.2g sodium bicarbonate, and 60mL deionized water to a 500mL four-necked flask. Then add the activated KIT-6 cubic mesoporous molecular sieve described in step S1. Immediately place the flask in an ice-water bath and ultrasonically disperse for 30min. Then place the flask on a magnetic stirrer, purge with nitrogen, and stir at 150rpm for 0.5h at room temperature. Subsequently, place the flask in a 75℃ oil bath and simultaneously add acrylate mixed monomers and 20g of 0.5% potassium persulfate aqueous solution using a constant pressure dropping funnel. The acrylate mixed monomers are 2g methyl methacrylate, 3g butyl acrylate, and 0.5g acrylic acid. The ternary system of methyl methacrylate, butyl acrylate, and acrylic acid forms a polyacrylate layer after free radical copolymerization. This not only introduces adsorption sites for hydrogen bonding and acid-base interactions, but also... The microphase separation structure composed of hydrophobic and hydrophilic segments anchors water molecules in local hydrophilic microregions, preventing them from spreading on the material surface to form a continuous water film. This avoids non-selective blocking of all VOCs caused by water film coverage. The monomer was added over 0.5 hours, and the potassium persulfate aqueous solution was added over 1.0 hour. After the addition was completed, the system was kept at a constant temperature for 5 hours, then cooled to room temperature, filtered using a 200-mesh filter cloth, and the filtrate was collected. The polyacrylate shell is wrapped around the surface of the activated KIT-6 cubic mesoporous molecular sieve, which improves the adsorption performance by introducing multiple chemical adsorption sites. At the same time, the polyacrylate layer on the surface acts as a physical barrier, slowing down or blocking the direct contact between water molecules and the silanol groups on the KIT-6 surface, thereby improving the adsorption stability of the material in a humid environment, resulting in a KIT-6@polyacrylate core-shell composite emulsion.

[0058] S3. Immerse the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel in the KIT-6@polyacrylate core-shell composite emulsion described in step S2, transfer it to a vacuum dryer, maintain it under a vacuum of -0.1 MPa for 20 min, remove the vacuum, and place it on a shaker to shake at 100 rpm for 1 h. Remove it, gently blot the surface liquid of the loaded aerogel with filter paper, pre-freeze it in a -20℃ freezer for 12 h, and then transfer it to a freeze dryer to freeze dry at -80℃ for 48 h. The KIT-6@polyacrylate core-shell composite adheres to the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel, providing additional mesoporous space and improving the adsorption capacity. The polyacrylate segments further enhance the affinity for nonpolar or weakly polar VOCs, achieving broad-spectrum and efficient adsorption performance. At the same time, the constructed hydrophobic barrier layer inhibits the competitive adsorption of water molecules and enhances the structural stability under humid conditions, resulting in a MOF composite adsorbent material for VOC adsorption.

[0059] Example 4

[0060] This embodiment proposes a MOF composite adsorbent material for VOC adsorption, comprising the following components in parts by weight: 10 parts of graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel and 10 parts of KIT-6@polyacrylate core-shell composite emulsion.

[0061] A graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel, comprising the following components in parts by weight: 12 parts graphene oxide, 24 parts cerium-based metal-organic framework, and 64 parts aminated modified cellulose nanofiber.

[0062] The preparation method of graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel includes the following steps:

[0063] (1) Add hexadecyltrimethoxysilane to 300 mL of anhydrous ethanol. The amount of hexadecyltrimethoxysilane added is 20.0 g. The long chain of hexadecyl has extremely low surface energy and strong hydrophobicity, which can enhance the affinity for hydrophobic VOCs. It can also act as a hydrophobic layer to protect the skeleton structure of nanocellulose, so that it can maintain its original shape and stacking structure in a humid environment. The pores will not shrink or close due to water absorption, forming a hexadecyltrimethoxysilanol solution for later use. Weigh 4.0 g of nanocellulose and add it to 70 mL of deionized water. Stir mechanically at 400 rpm for 30 min. Then, use a constant pressure dropping funnel to add it dropwise to the hexadecyltrimethoxysilanol solution at a rate of 1 drop / second. After the addition is completed, adjust the pH to 9.0 with ammonia water. Stir the reaction in a 40 °C water bath for 12 h. Centrifuge and precipitate. The material was first washed five times with ethanol, then twice with deionized water, and then redispersed in 200 mL of deionized water. Nanocellulose, as a rigid hydrophilic core, provides the main framework and mechanical strength of the material. The hexadecyl long chain grafted by chemical bonds forms a dense hydrophobic layer on the surface of cellulose, which not only enhances the affinity of hydrophobic VOCs, making it easier for VOC molecules to be captured from the air and adsorbed onto the material surface, but also provides additional adsorption space for VOC molecules through the organic interface layer formed by the long-chain alkanes. At the same time, the hydrophobic modification treatment inhibits the competitive adsorption of water molecules on the hydrophilic sites of nanocellulose, improves the anti-swelling property of nanocellulose, and makes its three-dimensional porous structure stable in a humid environment, ensuring that the diffusion channels of VOC molecules are always unobstructed, thus obtaining a modified nanocellulose solution.

[0064] (2) Add graphene oxide to 50 mL of deionized water. The amount of graphene oxide added is 0.8 g. The addition of graphene oxide improves the adsorption mechanism from a single surface coverage to a spatial network capture. It can also form a strong π-π stacking effect with common aromatic VOCs, achieving specific and efficient capture of aromatic pollutants. At the same time, as a highly rigid two-dimensional framework, graphene oxide inhibits the swelling and pore collapse of the material after adsorbing water through physical barriers and pore support, ensuring the adsorption performance of the material in a humid environment. Ultrasonic dispersion for 90 min and ice bath cooling are used to form a graphene oxide dispersion. Under 200 W power ice bath ultrasonic conditions, the modified nanocellulose solution described in step (1) is slowly added dropwise to the graphene oxide dispersion and mixed. After the addition is completed, ultrasonication is continued for 20 min, and stirring is carried out at room temperature for 4 h to form a composite dispersion. Then, the composite dispersion is added to the composite dispersion. 0.8 mL of 3-aminopropyltriethoxysilane was slowly added dropwise to the dispersion, and the reaction was carried out at room temperature for 6 h. Grafted hexadecyl long-chain nanocellulose served as a spacer and reinforcing phase, interspersed between the graphene oxide sheets. After the ethoxy group at one end of the 3-aminopropyltriethoxysilane was hydrolyzed, the graphene oxide and the modified nanocellulose were covalently linked together. This not only enhanced the richness of the pore structure and facilitated the rapid diffusion and transport of VOC molecules, but also ensured that the chemically cross-linked network was not easily swollen or disintegrated after absorbing water, thus ensuring the integrity of the pore structure in a humid environment. The large number of amino groups introduced on the material surface and inside the pores resulted in the simultaneous presence of hydrophobic alkyl chains and hydrophilic amino groups on the material surface, forming an amphiphilic surface. Through hydrophobic interaction sites, π-π stacking interactions, and chemisorption, the synergistic adsorption performance of hydrophobic and hydrophilic VOCs was improved, resulting in an aminated modified nanocellulose solution.

[0065] (3) Take 20 mL of the aminated modified nanocellulose solution described in step (2) and mix it with 20 mL of 0.5% bovine serum albumin solution. Under ice bath conditions, homogenize and emulsify at 10,000 rpm for 3 min. Slowly add 20 mL of n-hexane to form a preliminary emulsion and transfer it to a sealed container. Under ice bath conditions, ultrasonically emulsify and crosslink at 150 W power for 20 min. Then, slowly add 2.5 mL of 100 mmol / L cerium nitrate solution and 1.5 mL of 200 mmol / L trimesoyl alcohol solution. Stir the reaction at 200 rpm for 3 h at room temperature. Then, centrifuge at 4000 rpm for 5 min, collect the intermediate emulsion layer, pre-freeze at -20℃ for 24 h, and finally freeze-dry. The process involves freeze-drying at -60℃ for 36 hours. In this process, cerium-based metal-organic frameworks (MOFs) are grown in situ on the framework and pores of aminated cellulose nanofibers. The physical entanglement between the cellulose nanofibers provides a stable mechanical framework. The two work synergistically to form an aerogel with a multi-level porous structure, which not only facilitates the diffusion of VOC molecules but also significantly enhances the adsorption capacity for complex VOC molecules through multiple adsorption centers such as hydrophobic, hydrophilic, π-π stacking interactions, and coordination unsaturated sites. Furthermore, the cerium-based MOF crystals partially fill the hydrophilic pores of the aerogel, further enhancing the adsorption stability of the material in humid environments, resulting in a graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel.

[0066] This embodiment provides a method for preparing MOF composite adsorbent material for VOC adsorption, specifically including the following steps:

[0067] S1. KIT-6 cubic mesoporous molecular sieve with a pore size of 7 nm was placed in a muffle furnace. The amount of KIT-6 cubic mesoporous molecular sieve added was 25.0 g. KIT-6 has thick mesoporous pore walls and excellent hydrothermal and mechanical stability. It was calcined at 550℃ for 6 h, taken out, cooled to room temperature, ground, and the sieve mesh size was 200 mesh. After activation treatment, the three-dimensional cubic double helix pore structure of KIT-6 was fully exposed, and the pores were interconnected. This three-dimensional interconnected network provides the shortest diffusion path for VOC molecules from the material surface to the interior. Its huge surface area and pore volume become effective adsorption space. During the activation process, silanol condenses to form Si-O-Si bonds, making the pore wall structure more compact and further enhancing the stability of the framework. This ensures that the adsorption channels can remain unobstructed in a humid environment, thus obtaining activated KIT-6 cubic mesoporous molecular sieve.

[0068] S2. Add 1.0g sodium dodecyl sulfate, 0.2g sodium bicarbonate, and 60mL deionized water to a 500mL four-necked flask. Then add the activated KIT-6 cubic mesoporous molecular sieve described in step S1. Immediately place the flask in an ice-water bath and ultrasonically disperse for 60min. Then place the four-necked flask on a magnetic stirrer, purge with nitrogen, and stir at 170rpm for 1h at room temperature. Subsequently, place the flask in a 75℃ oil bath and simultaneously add acrylate mixed monomers and 20g of 0.5% potassium persulfate aqueous solution using a constant pressure dropping funnel. The acrylate mixed monomers are 2g methyl methacrylate, 3g butyl acrylate, and 0.5g acrylic acid. The ternary system of methyl methacrylate, butyl acrylate, and acrylic acid forms a polyacrylate layer after free radical copolymerization. This not only introduces adsorption sites for hydrogen bonding and acid-base interactions, but also allows for... The microphase separation structure composed of hydrophobic and hydrophilic segments anchors water molecules in local hydrophilic microregions, preventing them from spreading on the material surface to form a continuous water film. This avoids non-selective blocking of all VOCs caused by water film coverage. The monomer was added over 1 hour, and the potassium persulfate aqueous solution was added over 1.5 hours. After the addition was completed, the system was kept at a constant temperature for 6 hours, then cooled to room temperature, filtered using a 200-mesh filter cloth, and the filtrate was collected. The polyacrylate shell is wrapped around the surface of the activated KIT-6 cubic mesoporous molecular sieve, which improves the adsorption performance by introducing multiple chemical adsorption sites. At the same time, the polyacrylate layer on the surface acts as a physical barrier, slowing down or blocking the direct contact between water molecules and the silanol groups on the KIT-6 surface, thereby improving the adsorption stability of the material in a humid environment, resulting in a KIT-6@polyacrylate core-shell composite emulsion.

[0069] S3. Immerse the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel in the KIT-6@polyacrylate core-shell composite emulsion described in step S2, transfer it to a vacuum dryer, maintain it under a vacuum of -0.1 MPa for 30 min, break the vacuum, and then place it on a shaker and shake it at 200 rpm for 2 h. Remove it, gently blot the surface liquid of the loaded aerogel with filter paper, pre-freeze it in a -20℃ freezer for 24 h, and then transfer it to a freeze dryer and freeze-dry it at -80℃ for 72 h. The KIT-6@polyacrylate core-shell composite adheres to the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel, providing additional mesoporous space and improving the adsorption capacity. The polyacrylate segments further enhance the affinity for non-polar or weakly polar VOCs, achieving broad-spectrum and efficient adsorption performance. At the same time, the constructed hydrophobic barrier layer inhibits the competitive adsorption of water molecules and enhances the structural stability under humid conditions, thus obtaining a MOF composite adsorbent material for VOC adsorption.

[0070] Comparative Example 1

[0071] This comparative example provides a MOF composite adsorbent material for VOC adsorption, which differs from Example 1 in that the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel does not contain hexadecyltrimethoxysilane; the preparation method of the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel does not include step (1); the preparation method of the MOF composite adsorbent material for VOC adsorption is the same as that of Example 1.

[0072] Comparative Example 2

[0073] This comparative example provides a MOF composite adsorbent material for VOC adsorption, which differs from Example 1 in that the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel does not contain graphene oxide; graphene oxide is not added in step (2) of the preparation method of the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel; and the preparation method of the MOF composite adsorbent material for VOC adsorption is the same as that of Example 1.

[0074] Comparative Example 3

[0075] This comparative example provides a MOF composite adsorbent material for VOC adsorption, which differs from Example 1 in that the KIT-6@polyacrylate core-shell composite emulsion does not contain polyacrylate; the preparation method of the graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel is the same as in Example 1; and the acrylate mixed monomers are not added in step S2 of the preparation method of the MOF composite adsorbent material for VOC adsorption.

[0076] Experimental Example 1

[0077] Adsorption experiment

[0078] Test samples: MOF composite adsorbent materials for VOC adsorption prepared in Examples 1-4 and Comparative Examples 1-3.

[0079] Test method: In a sealed, atmospheric pressure, 25℃ constant temperature glass chamber (without additional humidification, the humidity inside the chamber is controlled at 25±2%RH), inject standard gases of benzene and formaldehyde using a micro-syringe. Run the built-in fan for 5-10 minutes to achieve a stable initial concentration C0 (50ppm benzene and 20ppm formaldehyde). Then, suspend a 1g test sample in the chamber. After 2 hours, measure the concentrations C1 of benzene and formaldehyde in the environment. Calculate the VOC removal rate (%) using the following formula:

[0080] VOC removal rate (%) = (C0-C1) / C0×100%.

[0081] Figure 1The figures show the VOC removal rates of Examples 1-4 and Comparative Examples 1-3. As shown, the removal rates of benzene and formaldehyde in Examples 1-4 were 90-95% and 85-90%, respectively, indicating strong adsorption and effective VOC removal. The removal rates of benzene and formaldehyde in Comparative Examples 1-3 were 56-82% and 67-80%, respectively, indicating moderate adsorption and ineffective VOC removal. The graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel in Comparative Example 1 did not contain hexadecyltrimethoxysilane, lacking the hexadecyl hydrophobic chain. Relying solely on the π-π stacking of graphene oxide and the limited hydrophobic segments of polyacrylate, benzene adsorption decreased significantly, while the hydrophilic sites remained intact, resulting in minimal impact on formaldehyde adsorption. The adsorption capacity of the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel in Comparative Example 2 is generally poor, and it cannot effectively remove VOCs. The graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel in Comparative Example 2 does not contain graphene oxide, resulting in the loss of π-π stacking. It relies solely on the hydrophobic interaction of hexadecyl and polyacrylate to adsorb benzene molecules, which is not conducive to enhancing the richness of the pore structure and restricts the diffusion and transport of formaldehyde, leading to generally poor adsorption capacity and ineffective removal of VOCs. The KIT-6@polyacrylate core-shell composite emulsion in Comparative Example 3 does not contain polyacrylate, but the adsorption of benzene by hexadecyl and graphene oxide still exists. The absence of the polyacrylate shell increases the shedding of MOF and KIT-6, which is not conducive to the adsorption of formaldehyde, resulting in generally poor adsorption capacity and ineffective removal of VOCs.

[0082] Experimental Example 2

[0083] Stability test

[0084] Test samples: MOF composite adsorbent materials for VOC adsorption prepared in Examples 1-4 and Comparative Examples 1-3.

[0085] Test Method: In a sealed, atmospheric pressure, 30L, 25℃ constant-temperature glass chamber, the relative humidity was first adjusted to 80%±2RH by injecting water vapor and turning on the fan, and stabilized for 10-15 minutes. Then, hydrophilic formaldehyde standard gas was injected using a micro-syringe, and the built-in small fan was turned on for 5-10 minutes to reach a stable initial concentration C0 (20ppm formaldehyde). A 1g test sample was then suspended in the chamber. After 2 hours, the formaldehyde concentration C1 in the environment was measured. The removal rate (%) under humid conditions was first obtained, and then combined with the removal rate data under dry conditions from Experiment 1, the humidity stability coefficient (%) was calculated according to the following formula. The higher the humidity stability coefficient, the smaller the loss of adsorption performance under humid conditions, indicating better adsorption stability.

[0086] Humidity stability coefficient (%) = Removal rate under humid conditions / Removal rate under dry conditions × 100%.

[0087] Figure 2 The figures show the humidity stability coefficients of Examples 1-4 and Comparative Examples 1-3. As shown, the humidity stability coefficients of Examples 1-4 are 89-94%, indicating good adsorption stability under humid conditions. The humidity stability coefficients of Comparative Examples 1-3 are 46-79%, indicating average or poor adsorption stability under humid conditions. The graphene oxide / cerium-based metal-organic framework@amino-modified cellulose nanofiber composite aerogel of Comparative Example 1 does not contain hexadecyltrimethoxysilane, lacking a hexadecyl hydrophobic barrier. Water easily contacts the amino groups and the hydrophilic sites of the MOF, leading to poor adsorption stability under humid conditions. The adsorption stability is poor. The graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel in Comparative Example 2 does not contain graphene oxide, so it cannot serve as a high-rigidity two-dimensional skeleton to enhance the physical barrier and pore support, resulting in poor adsorption stability in humid environments. The KIT-6@polyacrylate core-shell composite emulsion in Comparative Example 3 does not contain polyacrylate, so it lacks the physical shielding and adhesion of polyacrylate. KIT-6 and MOF are easy to detach, resulting in a discontinuous hydrophobic network and severe competitive adsorption of water, leading to poor adsorption stability in humid environments.

[0088] The above experimental results show that the adsorption and stability of Examples 1-4 of the present invention are significantly better than those of Comparative Examples 1-3. Among them, Example 1, which uses graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel and KIT-6@polyacrylate core-shell composite emulsion, has stronger adsorption and better stability. Attaching the KIT-6@polyacrylate core-shell composite to the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel provides additional mesoporous space, significantly improving the adsorption capacity. The polyacrylate segments further enhance the affinity for nonpolar VOCs, achieving broad-spectrum and efficient adsorption performance. In addition, the polyacrylate layer constructs a hydrophobic barrier on the framework surface, inhibiting the competitive adsorption of water molecules. Its physical adhesion can also anchor KIT-6 particles and MOF crystals to the framework, reducing particle aggregation and shedding, and enhancing adsorption stability in humid environments.

[0089] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

[0090] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A MOF composite adsorbent material for VOC adsorption, characterized in that: The MOF composite adsorbent material for VOC adsorption comprises the following components in parts by weight: 5-10 parts of graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel, and 10-40 parts of KIT-6@polyacrylate core-shell composite emulsion; the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel comprises the following components in parts by weight: 9-12 parts of graphene oxide, 21-24 parts of cerium-based metal-organic framework, and 64-70 parts of aminated cellulose nanofiber. The preparation method of the MOF composite adsorbent material for VOC adsorption specifically includes the following steps: S1. Place the KIT-6 cubic mesoporous molecular sieve with a pore size of 3-7 nm in a muffle furnace and calcine it at 500-550℃ for 5-6 hours. Remove it, cool it to room temperature, grind it, and make the sieve pore size 100-200 mesh to obtain the activated KIT-6 cubic mesoporous molecular sieve. S2. Add 1.0-1.2g sodium dodecyl sulfate, 0.2g sodium bicarbonate, and 60mL deionized water to a 500mL four-necked flask. Then add the activated KIT-6 cubic mesoporous molecular sieve described in step S1. Immediately place the flask in an ice-water bath and ultrasonically disperse for 30-60min. Then place the four-necked flask on a magnetic stirrer, purge with nitrogen, and stir at 150-170rpm for 0.5-1h at room temperature. Subsequently, place the flask in a 75℃ oil bath and simultaneously add acrylate mixed monomers and 20g of 0.5% potassium persulfate aqueous solution using a constant pressure dropping funnel. Control the monomers to be added over 0.5-1h and the potassium persulfate aqueous solution to be added over 1.0-1.5h. After the addition is complete, continue to keep the system at the temperature for 5-6h. Then cool to room temperature, filter using a 200-mesh filter cloth, collect the filtrate, and obtain KIT-6@polyacrylate core-shell composite emulsion. S3. Immerse the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel in the KIT-6@polyacrylate core-shell composite emulsion described in step S2, transfer it to a vacuum dryer, maintain it under a vacuum of -0.1MPa for 20-30 minutes, remove the vacuum, place it on a shaker, and shake it at 100-200rpm for 1-2 hours. Take it out, gently absorb the surface liquid of the loaded aerogel with filter paper, place it in a -20℃ freezer for 12-24 hours, and then transfer it to a freeze dryer to freeze dry at -80℃ for 48-72 hours to obtain the MOF composite adsorbent material for VOC adsorption. The preparation method of the graphene oxide / cerium-based metal-organic framework@aminated cellulose nanofiber composite aerogel specifically includes the following steps: (1) Add hexadecyltrimethoxysilane to 300mL of anhydrous ethanol to form a hexadecyltrimethoxysilanol solution for later use. Weigh 3.0-4.0g of nanocellulose and add it to 70mL of deionized water. Stir mechanically at 300-400rpm for 20-30min. Then, use a constant pressure dropping funnel to add it dropwise to the hexadecyltrimethoxysilanol solution at a rate of 1 drop / second. After the addition is complete, adjust the pH value to 8.0-9.0 with ammonia water. Stir the reaction in a 40℃ water bath for 6-12h. Centrifuge and wash the precipitate with ethanol 3-5 times, then wash it with deionized water 2 times. Then redisperse it in 200mL of deionized water to obtain a modified nanocellulose solution. (2) Add graphene oxide to 50 mL of deionized water, sonicate for 60-90 min while cooling in an ice bath to form a graphene oxide dispersion. Under 200 W power ice bath sonication, slowly add the modified nanocellulose solution described in step (1) to the graphene oxide dispersion and mix. After the addition is complete, continue sonication for 10-20 min and stir at room temperature for 2-4 h to form a composite dispersion. Then slowly add 0.6-0.8 mL of 3-aminopropyltriethoxysilane to the composite dispersion and react at room temperature for 4-6 h to obtain an aminated modified nanocellulose solution. (3) Take 20 mL of the aminated modified cellulose nanofiber solution described in step (2) and mix it with 20 mL of bovine serum albumin solution with a mass fraction of 0.5%. Under ice bath conditions, homogenize and emulsify at 8000-10000 rpm for 2-3 min. Slowly add 20 mL of n-hexane to form a preliminary emulsion and transfer it to a sealed container. Under ice bath conditions, use 150 W power to ultrasonically emulsify and crosslink for 15-20 min. Then, slowly add 1.5-2.5 mL of 100 mmol / L cerium nitrate solution and 1.5 mL of 200 mmol / L trimesoyl alcohol solution. Stir the reaction at 100-200 rpm at room temperature for 2-3 h. Then, centrifuge at 3000-4000 rpm for 3-5 min, collect the intermediate emulsion layer, pre-freeze at -20℃ for 24 h, and finally put it into a freeze dryer and freeze-dry at -60℃ for 36 h to obtain graphene oxide / cerium-based metal-organic framework@aminated modified cellulose nanofiber composite aerogel.

2. The MOF composite adsorbent material for VOC adsorption according to claim 1, characterized in that: In step S1, the amount of KIT-6 cubic mesoporous molecular sieve added is 15.0-25.0g.

3. The MOF composite adsorbent material for VOC adsorption according to claim 2, characterized in that: In step S2, the acrylate mixed monomers are 2g methyl methacrylate, 3g butyl acrylate and 0.5g acrylic acid.

4. The MOF composite adsorbent material for VOC adsorption according to claim 3, characterized in that: In step (1), the amount of hexadecyltrimethoxysilane added is 10.0-20.0g.

5. The MOF composite adsorbent material for VOC adsorption according to claim 4, characterized in that: In step (2), the amount of graphene oxide added is 0.4-0.8g.

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