MOF composite catalytic material for removing VOCs as well as preparation method and application of MOF composite catalytic material

Abstract

The invention provides an MOF (Metal Organic Framework) composite catalytic material for removing VOCs (Volatile Organic Compounds) as well as a preparation method and application thereof. According to the MOF composite catalytic material for removing VOCs, modified cellulose is used as a three-dimensional structure carrier, MOF and a metal catalyst are firmly loaded in a cellulose network through an in-situ growth process, and a macroscopic composite catalytic material with hierarchical pores, high specific surface area and good mechanical stability is formed; the composite material shows excellent catalytic efficiency, cycling stability and recoverability in the fields of catalytic degradation of VOCs, air purification and the like, and has a good application prospect. The invention also provides a preparation method and application of the MOF composite catalytic material for removing VOCs.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of air purification materials, and particularly relates to a MOF composite catalytic material for removing VOCs and a preparation method and application thereof. BACKGROUND

[0002] Volatile organic compounds (VOCs) as a typical atmospheric pollutant are widely derived from industrial production, building decoration, transportation and other fields, which not only causes serious damage to the ecological environment, but also harms human health through respiratory, skin contact and other ways, and causes a series of problems such as respiratory diseases and nervous system damage, so efficient removal of VOCs has become an important issue in the field of environmental governance. Metal organic framework (MOF) materials have unique advantages in the fields of VOCs adsorption and catalytic degradation due to their ultra-high specific surface area, controllable pore structure and rich active sites, and have become a research hotspot in recent years.

[0003] However, most of the MOF materials currently exist in the form of micron or nanoscale powders. Although this form can maximize the specific surface area to ensure basic activity, it still faces many bottlenecks in actual engineering applications. On the one hand, ultra-fine powder MOF materials are difficult to realize efficient separation and recycling, leading to complex operation process, increased running cost and easy secondary pollution; on the other hand, they lack macroscopic structure and self-supporting characteristics, and cannot adapt to large-scale application scenarios such as fixed bed catalysis and air purifier filling, which greatly limits the technology transformation and industrialization promotion. To solve this problem, the existing technology adopts the idea of loading MOF on the carrier to construct a composite system, and carbon-based materials are often used as carriers due to their good chemical stability, but the surface active functional groups of such materials are scarce, and the interaction between MOF crystals is mostly physical adhesion or weak interaction, which is easy to cause MOF to fall off under the conditions of fluid impact, mechanical disturbance and the like, resulting in poor structural stability of the composite material, cycle performance decay, and the synergistic effect of the carrier and MOF cannot be fully played, so the catalytic degradation efficiency of VOCs is limited.

[0004] The prior art still has obvious deficiencies, some MOF derived catalytic materials have certain degradation capacity, but the preparation process is complex, the product is still a micro-nano powder, and separation and recovery are difficult; there is also a composite system in which MOF is grown in situ on a paper-based material, but its mechanism is mainly physical adsorption, lacks catalytic conversion capacity, is easy to saturate and difficult to regenerate, and the MOF itself has limitations in hydrothermal stability and mechanical strength, resulting in a single function of the composite material and insufficient durability, which is difficult to adapt to complex and variable or continuous operation air purification scenes. Therefore, developing a new MOF composite system with macroscopic morphology, excellent structural stability, easy recyclability and high catalytic activity, achieving an optimized balance between various properties, has become a key requirement for solving the technical bottleneck of efficient removal of VOCs and promoting the engineering application of MOF materials. SUMMARY

[0005] The present application aims to at least solve one of the above-mentioned technical problems in the prior art. To this end, the present application provides a MOF composite catalytic material for removing VOCs, which uses modified cellulose as a three-dimensional structure carrier, and firmly loads MOF and metal catalysts in the cellulose network through an in-situ growth process, forming a macroscopic composite catalytic material with multi-level pores, high specific surface area and good mechanical stability, which exhibits excellent catalytic efficiency, cycle stability and easy recyclability in the fields of VOCs catalytic degradation and air purification, and has good application prospects.

[0006] The present application also provides a preparation method of a MOF composite catalytic material for removing VOCs.

[0007] The present application also provides an air purification device.

[0008] The first aspect of the present application provides a MOF composite catalytic material for removing VOCs, comprising a modified cellulose three-dimensional network structure carrier, the modified cellulose three-dimensional network structure carrier being loaded with MOF and a metal catalyst, and the preparation raw material of the modified cellulose three-dimensional network structure carrier comprising cotton fiber, bamboo fiber, conifer pulp fiber, broadleaf wood pulp fiber, sugarcane residue fiber or straw fiber, and the metal catalyst comprising at least one of MnO2 and Co3O4.

[0009] The MOF composite catalytic material for removing VOCs of the present application has at least the following beneficial effects: The application takes natural cellulose (such as cotton fiber, bamboo fiber, etc.) as raw material, forms a micro-nano scale cellulose network rich in active functional groups (such as sulfonic acid group, phosphoric acid group, etc.) on the surface after modification. The network has a through multi-level pore structure with uniform pore distribution, while retaining the good mechanical toughness and structural plasticity of cellulose itself. The surface active functional groups provide a large number of chemical binding sites for MOF and metal catalysts, realizing the firm anchoring of active components; the three-dimensional network structure provides a smooth mass transfer channel for gas phase reactants (VOCs), while ensuring the mechanical stability of the whole material, solving the problems of easy agglomeration and difficult recycling of traditional powder MOF.

[0010] The MOF crystals are uniformly dispersed in the cellulose three-dimensional network without obvious agglomeration, and have ultra-high specific surface area and controllable pore structure, which form a synergy with the multi-level pores of the cellulose network, further expanding the specific surface area of the composite material, providing sufficient active sites for VOCs adsorption and catalysis. The MOF and the modified cellulose realize strong interfacial bonding through coordination bond and other chemical actions, rather than physical adhesion, which significantly improves the structural stability of the composite material under fluid impact or mechanical disturbance, avoiding the performance degradation caused by MOF shedding.

[0011] The MOF composite catalytic material for removing VOCs synchronously introduces metal catalyst and organic ligand into the reaction system, and the metal catalyst is uniformly dispersed on the surface of the cellulose network and the MOF crystals during the in-situ growth of the MOF, forming a synergistic catalytic structure of MOF and metal catalyst.

[0012] The MOF composite catalytic material for removing VOCs has small catalyst particle size and uniform dispersion without aggregation, which forms a close interfacial contact with the MOF crystals and the cellulose carrier, which is beneficial to the synergistic performance of electron transfer and catalytic reaction.

[0013] The MOF composite catalytic material for removing VOCs has a certain particle size of macroscopic material (non-micro-nano powder), retains the structural toughness of the cellulose network, is easy to recycle and reuse, and can be adapted to fixed bed catalysis, air purifier device filling and other engineering application scenarios. The multi-level pores (through pores of the cellulose network and micropores / mesopores of the MOF) ensure efficient diffusion and adsorption of VOC molecules; the strong interfacial bonding of the carrier, MOF and catalyst structure realizes the adsorption and catalysis synergy, enriches VOCs through the adsorption of MOF and cellulose, and efficiently degrades VOCs through the catalytic activity of the metal catalyst, while improving the cycle stability of the material.

[0014] In summary, the structure of the composite material is an integrated composite system in which the modified cellulose three-dimensional network is a support skeleton, the MOF is an adsorption and catalytic active core, and the metal catalyst is a catalytic enhancement additive. Through the structure synergy of multiple components and the strong combination of interfaces, an optimized balance between macroscopic morphology, structural stability, and catalytic activity is achieved.

[0015] According to some embodiments of the present application, the MOF is grown in situ on the modified cellulose three-dimensional network structure carrier.

[0016] The metal salt (such as zinc nitrate, cobalt nitrate, etc.) can be first pre-coordinated with the active groups on the surface of the modified cellulose through a room temperature step-by-step assembly process, and then reacted with an organic ligand to form MOF crystals (such as ZIF-8, ZIF-67, etc.) in situ inside and on the surface of the cellulose network.

[0017] According to some embodiments of the present application, the metal catalyst includes at least one of MnO2 and Co3O4.

[0018] The second aspect of the present application provides a method for preparing the VOC-removing MOF composite catalytic material of the first aspect of the present application, including the following steps: S1: mechanically crushing a cellulose raw material to obtain cellulose powder, dispersing the cellulose powder in a solvent, adding a chemical modification reagent to perform esterification, filtering and washing after the reaction is completed, and obtaining the modified cellulose three-dimensional network structure carrier; S2: dispersing the modified cellulose three-dimensional network structure carrier to form a dispersion liquid, adding a metal salt solution to the dispersion liquid, pre-coordinating under stirring at room temperature, then adding a mixed solution containing a metal catalyst and an organic ligand, continuing to stir and react, allowing the metal catalyst to grow in situ on the surface of the modified cellulose three-dimensional network structure carrier, filtering, washing, and drying after the reaction is completed, and obtaining a precursor material; S3: calcining the precursor material to obtain the VOC-removing MOF composite catalytic material.

[0019] The present application is a combination process of mechanical crushing + chemical esterification modification. On the one hand, the cellulose raw material is processed into a powder form to increase the specific surface area to improve the subsequent reaction contact efficiency. On the other hand, the esterification reaction introduces a large number of active functional groups (such as sulfonic acid groups, phosphoric acid groups, etc.) on the surface of cellulose, successfully constructing a modified cellulose three-dimensional network structure carrier. The carrier not only retains the advantages of natural cellulose such as green renewable and strong mechanical toughness, but also provides a large number of firm chemical binding sites for MOF and metal catalysts through surface active functional groups, solving the defects of traditional carriers (such as carbon-based materials) such as insufficient surface activity and only physical adhesion with MOF, and improving the interface bonding strength and structural stability of the composite material from the source. At the same time, the three-dimensional network structure has through channels, which provides structural support for subsequent VOC mass transfer and active site exposure.

[0020] Further, the present application adopts a pre-arrangement at room temperature + step-by-step assembly in-situ growth process, which does not require harsh conditions such as high temperature and high pressure, significantly reduces energy consumption and process complexity, and avoids the destruction of the material structure caused by high temperature. First, the metal salt is pre-arranged with the surface active groups of the modified cellulose to provide precise nucleation sites for MOF growth, and then the metal catalyst and organic ligand are introduced to react, ensuring that the MOF and metal catalyst grow uniformly on the surface and inside of the cellulose three-dimensional network and are closely loaded, effectively avoiding the agglomeration of active components. This process realizes the synergistic integration of the carrier-MOF-metal catalyst, which not only guarantees the high specific surface area and pore characteristics of the MOF, but also allows the metal catalyst and the MOF to form a close interface contact, laying a structural foundation for their synergistic catalysis of VOCs. At the same time, the room temperature operation makes the process easier to scale up.

[0021] It is easy to understand that the entire preparation process from carrier modification to in-situ loading to calcination molding is interlocking and synergistically optimized: the modification process of S1 provides a structural premise for the precise loading of S2, the step-by-step assembly of S2 ensures the strong combination of active components and the carrier, and the calcination treatment of S3 further optimizes the pore structure of the material, improves the mechanical stability and utilization rate of the catalytic active sites. Ultimately, the MOF composite catalytic material prepared by this method has the macroscopic structural toughness of the cellulose carrier (easy to recycle and adaptable to engineering application scenarios), the high specific surface area and adsorption performance of the MOF, and the high catalytic activity of the metal catalyst, realizing the synergistic effect of adsorption-catalysis and significantly improving the VOCs removal efficiency. At the same time, the process is simple and convenient to operate, and the drying and calcination conditions are mild and controllable, and the product is easy to separate and purify, solving the practical bottleneck of traditional powder MOF, which is difficult to recycle and easy to cause secondary pollution, and reducing the cost of industrial application.

[0022] The method has good universality for the selection of key components, and the cellulose raw material can be selected from cotton fiber, bamboo fiber, straw fiber and various natural biomasses, and the solvent, chemical modification reagent, metal salt, metal catalyst and organic ligand can be flexibly adjusted within the limited range of the application (such as zinc nitrate / cobalt, MnO2 / Co3O4, etc. can be selected as the metal salt and the catalyst). By adjusting the proportion of each component, the reaction time, the calcination parameters and the like, the growth morphology, the pore size distribution and the active site density of the MOF can be precisely controlled, so as to adapt to the removal requirements of different types of VOCs, to provide a wide space for material function customization, and to further expand the application potential of the material in different scenes such as air purification and industrial waste gas treatment.

[0023] According to some embodiments of the application, in step S1, the mechanical crushing treatment comprises at least one of crushing, shearing, grinding, and ball milling.

[0024] According to some embodiments of the application, in step S1, the solvent comprises at least one of water, methanol, ethanol, and N,N-dimethylformamide.

[0025] According to some embodiments of the application, in step S1, the chemical modification reagent comprises at least one of sulfuric acid, phosphoric acid, nitric acid, and sulfamic acid.

[0026] According to some embodiments of the application, the esterification reaction comprises a sulfate esterification, a phosphate esterification, or a nitrate esterification reaction.

[0027] According to some embodiments of the application, the reaction time of the esterification reaction is 0.5-6h.

[0028] According to some embodiments of the application, the reaction time of the esterification reaction is any one of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, such as 2h, or a range value formed by any two, such as 1h-3h.

[0029] According to some embodiments of the application, the solid-liquid ratio of the esterification reaction system is 1:(5-20)g / mL.

[0030] According to some embodiments of the present application, the solid-liquid ratio of the esterification reaction system is any one of 1:5 g / mL, 1:6 g / mL, 1:7 g / mL, 1:8 g / mL, 1:9 g / mL, 1:10 g / mL, 1:11 g / mL, 1:12 g / mL, 1:13 g / mL, 1:14 g / mL, 1:15 g / mL, 1:16 g / mL, 1:17 g / mL, 1:18 g / mL, 1:19 g / mL, 1:20 g / mL, such as 1:10 g / mL, or a range value formed by any two of them, such as 1:8 g / mL~1:12 g / mL.

[0031] According to some embodiments of the present application, in the esterification reaction, the mass ratio of the chemical modification reagent to the cellulose powder is (1~10):1.

[0032] According to some embodiments of the present application, in the esterification reaction, the mass ratio of the chemical modification reagent to the cellulose powder is any one of 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, such as 5:1, or a range value formed by any two of them, such as 3:1~7:1.

[0033] According to some embodiments of the present application, in step S1, the washing includes at least one of suction filtration washing, centrifugal washing, filter bag washing or stainless steel filter screen washing.

[0034] According to some embodiments of the present application, in step S1, the washing solvent includes at least one of water, methanol and ethanol.

[0035] According to some embodiments of the present application, in step S2, the defibrillation dispersion includes one of mechanical stirring and high-speed shearing dispersion.

[0036] According to some embodiments of the present application, the solvent for defibrillation dispersion includes at least one of water, methanol and DMF.

[0037] According to some embodiments of the present application, the metal salt solution includes a zinc nitrate solution or a cobalt nitrate solution.

[0038] According to some embodiments of the present application, in step S2, the organic ligand includes dimethyl imidazole.

[0039] According to some embodiments of the present application, in step S2, the pre-ligand stirring time is 1~24 h.

[0040] According to some embodiments of the present application, in step S2, the pre-locating stirring time is any one of 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, such as 10h, or a range value formed by any two, such as 6h-12h.

[0041] According to some embodiments of the present application, the molar ratio of the modified cellulose three-dimensional network structure carrier, metal salt solution, organic ligand, and metal catalyst is 1:(1-10):(1-10):(0.1-5).

[0042] According to some embodiments of the present application, the molar ratio of the modified cellulose three-dimensional network structure carrier, metal salt solution, organic ligand, and metal catalyst is any one of 1:1:1:0.1, 1:2:2:0.5, 1:3:3:1, 1:4:4:1.5, 1:5:5:2, 1:6:6:2.5, 1:7:7:3, 1:8:8:3.5, 1:9:9:4, 1:10:10:5, such as 1:5:5:2, or a range value formed by any two, such as 1:3:3:1-1:7:7:3.

[0043] According to some embodiments of the present application, in step S2, the time for continuing stirring reaction is 1-6h.

[0044] According to some embodiments of the present application, in step S2, the time for continuing stirring reaction is any one of 1h, 2h, 3h, 4h, 5h, 6h, such as 3h, or a range value formed by any two, such as 2h-4h.

[0045] According to some embodiments of the present application, in step S2, the drying condition is vacuum drying at 80℃ for 3-12h.

[0046] According to some embodiments of the present application, in step S2, the drying condition is vacuum drying at 80℃ for any one of 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, such as 6h, or a range value formed by any two, such as 5h-9h.

[0047] According to some embodiments of the present application, in step S3, the calcination temperature is 200-500℃.

[0048] According to some embodiments of the present application, in step S3, the calcination temperature is any one of 200℃, 220℃, 240℃, 260℃, 280℃, 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, such as 350℃, or a range value formed by any two, such as 300℃-400℃.

[0049] According to some embodiments of the present application, in step S3, the calcination time is 2-12h.

[0050] According to some embodiments of the present application, in step S3, the calcination time is any one of 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, such as 6h, or a range value formed by any two, such as 4h-8h.

[0051] According to some embodiments of the present application, in step S3, the calcination is also subjected to mechanical treatment, the mechanical treatment includes at least one of crushing, shearing, grinding, disc milling or ball milling, and the treatment time is 1-10min.

[0052] According to some embodiments of the present application, in step S3, the calcination is also subjected to mechanical treatment, the mechanical treatment includes at least one of crushing, shearing, grinding, disc milling or ball milling, and the treatment time is any one of 1min, 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min, such as 5min, or a range value formed by any two, such as 3min-7min.

[0053] The third aspect of the present application provides an air purification device, which comprises the MOF composite catalytic material for removing VOCs of the present application.

[0054] The air purification device of the present application has the following advantages: the core material is a modified cellulose three-dimensional network, the MOF and the metal catalyst are firmly loaded through an in-situ growth process, the multi-stage pore structure formed can ensure efficient mass transfer and adsorption enrichment of VOCs molecules, and the synergistic catalytic effect of the MOF and the metal catalyst can realize efficient degradation of VOCs, the removal rate of VOCs can reach 96% within 30 minutes, and the purification efficiency is excellent; at the same time, the material has the structural toughness and good mechanical stability of cellulose, the macroscopic form makes it easy to recycle and reuse, and the material avoids the disadvantages of difficult separation and secondary pollution of traditional powder MOF materials, and meets the long-term stable operation requirement of the device; and the material preparation process is mild and the raw materials are green and renewable, so that the device can realize efficient air purification function, environmental protection and engineering practicability, and can be widely applied to indoor air treatment, industrial waste gas purification and other scenes, and provides a durable, efficient and environmentally friendly air purification solution for users. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 A real object diagram of the amino sulfonic acid modified cellulose loaded ZIF-8 (SC@ZIF-8) prepared in Example 2.

[0056] Figure 2 A real object diagram of the composite material SC@ZIF-8 / MnO2 formed after further loading of MnO2 in Example 2. DETAILED DESCRIPTION

[0057] The concept and technical effects of the present application will be described in detail below in combination with examples, so as to fully understand the purpose, features and effects of the present application. Obviously, the described examples are only part of the examples of the present application, but not all examples, and other examples obtained by those skilled in the art without creative labor based on the examples of the present application are within the scope of protection of the present application.

[0058] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are contained in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0059] Unless otherwise specified, "room temperature" in the present application means 25℃±5℃.

[0060] Unless otherwise specified, "about" in the present disclosure means an allowable error of ±2%.

[0061] Unless otherwise specified, the examples were performed under conventional conditions or under the conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used were conventional products that can be obtained commercially.

[0062] Example 1 A supported solid composite material was prepared according to the following steps: (1) 60 g of sulfamic acid was weighed and added to 1 L of DMF in a 1 L round-bottom flask, and heated in a 90°C water bath for a period of time until the solution in the flask became white and turbid. 30 g of cotton fiber (absolute dry mass) was added to the above-mentioned round-bottom flask and kept at 90°C for 2 h. After the reaction was completed, the sample was washed with deionized water three times, and then replaced with methanol three times. Then the sample was treated with a cell disrupter for 5 minutes to obtain sulfamic acid modified micro-nano cellulose (SCMNFs).

[0063] (2) 30 g of the above-mentioned SCMNFs was dispersed in 400 mL of methanol and stirred at room temperature at low speed (100-200 rpm). 8.91 g of zinc nitrate hexahydrate was dissolved in 50 mL of methanol and slowly dropped along the wall of a glass cup into the fiber dispersion solution for reaction for 24 h to allow chelation of the fiber with metal ions. 4.926 g of 2-methylimidazole was dissolved in 50 mL of methanol and slowly poured into the above-mentioned solution for further reaction for 4 h. After the reaction was completed, the sample was washed with methanol three times, and then washed with deionized water three times, and finally dried at 60°C under vacuum for 48 h to obtain SCMNFs@ZIF-8 composite material.

[0064] Example 2 A supported solid composite material was prepared according to the following steps: (1) 60 g of sulfamic acid was weighed and added to 1 L of DMF in a 1 L round-bottom flask, and heated in a 90°C water bath for a period of time until the solution in the flask became white and turbid. 30 g of cotton fiber (absolute dry mass) was added to the above-mentioned round-bottom flask and kept at 90°C for 2 h. After the reaction was completed, the sample was washed with deionized water three times, and then replaced with methanol three times. Then the sample was treated with a cell disrupter for 5 minutes to obtain sulfamic acid modified micro-nano cellulose (SCMNFs).

[0065] (2) The above SCMNFs 30 g were dispersed in 400 mL of methanol and stirred at room temperature at low speed (100-200 rpm). 8.91 g of zinc nitrate hexahydrate was dissolved in 50 mL of methanol, and the solution was slowly dropped along the wall of a glass cup into the fiber dispersion solution to react for 24 h to allow the fiber to chelate with metal ions. 4.926 g of 2-methylimidazole and 3 g of MnO2 catalyst powder were dissolved in 50 mL of methanol, and the solution was slowly poured into the above solution and continued to react for 4 h. After the reaction was completed, the sample was washed with methanol three times, washed with deionized water three times, and finally dried at 60°C under vacuum for 48 h to obtain the SCMNFs@ZIF-8 / MnO2 composite material.

[0066] Example 3 A supported solid composite material was prepared, and the specific steps were as follows: (1) 60 g of sulfamic acid was weighed and added to 1 L of DMF in a 1 L round-bottom flask, and heated in a 90°C water bath for a period of time until the solution in the flask became white and turbid. 30 g of cotton fiber (absolute dry mass) was added to the above-mentioned round-bottom flask, and kept at 90°C for 2 h. After the reaction was completed, the sample was washed with deionized water three times, and then replaced with methanol three times. Then the sample was treated with a cell disruptor for 5 minutes to obtain sulfamic acid modified micro-nano cellulose (SCMNFs).

[0067] (2) The above SCMNFs 30 g were dispersed in 400 mL of methanol and stirred at room temperature at low speed (100-200 rpm). 8.91 g of zinc nitrate hexahydrate was dissolved in 50 mL of methanol, and the solution was slowly dropped along the wall of a glass cup into the fiber dispersion solution to react for 24 h to allow the fiber to chelate with metal ions. 4.926 g of 2-methylimidazole and 3 g of MnO2 catalyst powder were dissolved in 50 mL of methanol, and the solution was slowly poured into the above solution and continued to react for 4 h. After the reaction was completed, the sample was washed with methanol three times, washed with deionized water three times, and finally dried at 60°C under vacuum for 48 h to obtain the SCMNFs@ZIF-8 / MnO2 composite material.

[0068] Example 4 A supported solid composite material was prepared, and the specific steps were as follows: (1) 60 g of sulfamic acid was weighed and added to 1 L of DMF in a 1 L round-bottom flask, and heated in a 90°C water bath for a period of time until the solution in the flask became white and turbid. 30 g of cotton fiber (absolute dry mass) was added to the above-mentioned round-bottom flask, and kept at 90°C for 2 h. After the reaction was completed, the sample was washed with deionized water three times, and then replaced with methanol three times. Then the sample was treated with a cell disruptor for 5 minutes to obtain sulfamic acid modified micro-nano cellulose (SCMNFs).

[0069] (2) The above SCMNFs 30 g were dispersed in 400 mL of methanol and stirred at room temperature at low speed (100-200 rpm). 8.91 g of zinc nitrate hexahydrate was dissolved in 50 mL of methanol, and the solution was slowly dropped along the wall of a glass cup into the fiber dispersion solution, and the fiber was allowed to react with metal ions for 24 h to form a chelate. 4.926 g of 2-methylimidazole, 1.5 g of Co3O4 catalyst powder, and 1.5 g of MnO2 catalyst powder were dissolved in 50 mL of methanol, and the solution was slowly poured into the above solution and continued to react for 4 h. After the reaction was completed, the product was washed with methanol three times and then with deionized water three times, and finally dried at 60°C under vacuum for 48 h to obtain the SCMNFs@ZIF-8 / Co3O4 / MnO2 composite material.

[0070] Example 5 A MOF composite catalytic material for removing VOCs was prepared. Specifically, the SCMNFs@ZIF-8 / MnO2 composite material obtained in Example 2 was calcined in a muffle furnace at 500°C for 6 h, and after cooling, the product was crushed into C@ZIF-8 / MnO2 powder.

[0071] Example 6 A MOF composite catalytic material for removing VOCs was prepared. Specifically, the SCMNFs@ZIF-8 / Co3O4 composite material obtained in Example 3 was calcined in a muffle furnace at 500°C for 6 h, and after cooling, the product was crushed into C@ZIF-8 / Co3O4 powder.

[0072] Example 7 A MOF composite catalytic material for removing VOCs was prepared. Specifically, the SCMNFs@ZIF-8 / Co3O4 / MnO2 composite material obtained in Example 4 was calcined in a muffle furnace at 500°C for 6 h, and after cooling, the product was crushed into C@ZIF-8 / Co3O4 / MnO2 powder.

[0073] Example 8 A MOF composite catalytic material for removing VOCs was prepared. The specific preparation steps are as follows: (1) 60 g of sulfamic acid and 1 L of DMF were weighed into a 1 L round-bottom flask, and heated in a 90°C water bath for a period of time until the solution in the flask became white and turbid. 30 g of cotton fiber (absolute dry mass) was added to the above round-bottom flask, and maintained at 90°C for 2 h. After the reaction was completed, the product was washed with deionized water three times, and then replaced with methanol three times. Then, the sample was treated with a cell disrupter for 5 minutes to obtain sulfamic acid-modified micro-nano cellulose (SCMNFs).

[0074] (2) The SCMNFs 30 g were dispersed in 400 mL of methanol and stirred at room temperature at low speed (100-200 rpm). 8.91 g of zinc nitrate hexahydrate was dissolved in 50 mL of methanol, and the solution was slowly dropped along the wall of a glass cup into the fiber dispersion liquid to react for 24 h to allow the fiber to chelate with metal ions. 4.926 g of 2-methylimidazole and 3 g of MnO2 catalyst powder were dissolved in 50 mL of methanol, and the solution was slowly poured into the above solution and continued to react for 4 h. After the reaction was completed, the sample was washed with methanol three times, washed with deionized water three times, and finally dried at 60°C under vacuum for 48 h to obtain the PCMNFs@ZIF-8 / MnO2 composite material.

[0075] Example 9 A MOF composite catalytic material for removing VOCs was prepared, and the specific preparation steps were as follows: (1) 30 g of cotton fiber (absolute dry mass) was added to the round-bottom flask, treated with 45% phosphoric acid at 35°C for 2 hours, and then washed to neutral. The sample was then replaced with methanol three times with deionized water, and then treated with a cell wall crusher for 5 minutes to obtain phosphoric acid modified micro-nano cellulose (PCMNFs).

[0076] (2) The above PCMNFs 30 g were dispersed in 400 mL of methanol and stirred at room temperature at low speed (100-200 rpm). 8.91 g of zinc nitrate hexahydrate was dissolved in 50 mL of methanol, and the solution was slowly dropped along the wall of a glass cup into the fiber dispersion liquid to react for 24 h to allow the fiber to chelate with metal ions. 4.926 g of 2-methylimidazole and 3 g of MnO2 catalyst powder were dissolved in 50 mL of methanol, and the solution was slowly poured into the above solution and continued to react for 4 h. After the reaction was completed, the sample was washed with methanol three times, washed with deionized water three times, and finally dried at 60°C under vacuum for 48 h to obtain the PCMNFs@ZIF-8 / MnO2 composite material.

[0077] Example 10 A MOF composite catalytic material for removing VOCs was prepared, and the specific preparation steps were as follows: (1) 30 g of cotton fiber (absolute dry mass) was added to the round-bottom flask, treated with 45% phosphoric acid at 35°C for 2 hours, and then washed to neutral. The sample was then replaced with methanol three times with deionized water, and then treated with a cell wall crusher for 5 minutes to obtain phosphoric acid modified micro-nano cellulose (PCMNFs).

[0078] (2) The above NCMNFs 30 g were dispersed in 400 mL of methanol and stirred at room temperature at low speed (100-200 rpm). 8.91 g of zinc nitrate hexahydrate was dissolved in 50 mL of methanol, and the solution was slowly dropped along the wall of a glass cup into the fiber dispersion solution to react for 24 h to allow the fiber to chelate with metal ions. 4.926 g of 2-methylimidazole and 3 g of MnO2 catalyst powder were dissolved in 50 mL of methanol, and the solution was slowly poured into the above solution and continued to react for 4 h. After the reaction was completed, the solution was washed with methanol three times and then with deionized water three times, and finally dried at 60°C under vacuum for 48 h to obtain the NCMNFs@ZIF-8 / MnO2 composite material.

[0079] Comparative Example 1 A method for preparing a MOF composite catalytic material, and the specific preparation steps are as follows: 30 g of cotton fibers (absolute dry mass) were ground into micro-nano cellulose (CMNFs), added to a round-bottom flask, and dispersed in 400 mL of methanol and stirred at room temperature at low speed (100-200 rpm). 8.91 g of zinc nitrate hexahydrate was dissolved in 50 mL of methanol, and the solution was slowly dropped along the wall of a glass cup into the fiber dispersion solution to react for 24 h to allow the fiber to chelate with metal ions. 4.926 g of 2-methylimidazole was dissolved in 50 mL of methanol, and the solution was slowly poured into the above solution and continued to react for 4 h. After the reaction was completed, the solution was washed with methanol three times and then with deionized water three times, and finally dried at 60°C under vacuum for 48 h to obtain the CMNFs@ZIF-8 composite material.

[0080] Comparative Example 2 A method for preparing a MOF composite catalytic material, and the specific preparation steps are as follows: 30 g of carbon fibers were ground into micro-nano carbon fibers, added to a round-bottom flask, and dispersed in 400 mL of methanol and stirred at room temperature at low speed (100-200 rpm). 8.91 g of zinc nitrate hexahydrate was dissolved in 50 mL of methanol, and the solution was slowly dropped along the wall of a glass cup into the carbon fiber dispersion solution to react for 24 h to allow the fiber to chelate with metal ions. 4.926 g of 2-methylimidazole was dissolved in 50 mL of methanol, and the solution was slowly poured into the above solution and continued to react for 4 h. After the reaction was completed, the solution was washed with methanol three times and then with deionized water three times, and finally dried at 60°C under vacuum for 48 h to obtain the C@ZIF-8 composite material.

[0081] Comparative Example 3 A method for preparing a MOF composite catalytic material, and the specific preparation steps are as follows: 30 g of carbon fibers were ground into micro-nano carbon fibers, added to 3 g of MnO2 and stirred to obtain a C@MnO2 composite material.

[0082] Comparative Example 4 A preparation method of a MOF composite catalytic material, and the specific preparation steps are as follows: 30g of carbon fiber is weighed and crushed into micro-nano carbon fiber, 3g of Co3O4 is added and stirred and mixed to obtain a C@Co3O4 composite material.

[0083] Comparative example 5 A preparation method of a MOF composite catalytic material, and the specific preparation steps are as follows: 30g of carbon fiber is weighed and crushed into micro-nano carbon fiber, 1.5g of Co3O4 and 1.5g of MnO2 are added and stirred and mixed to obtain a C@MnO2 / Co3O4 composite material.

[0084] Performance test Instrument equipment: (1) Test cabin (self-made, volume 3 m³, meeting the requirements of GB / T 18801-2022 Formaldehyde CCM test).

[0085] (2) Laoying 2020 air sampler (Qingdao Laoshan Applied Technology Institute).

[0086] (3) T6 new century ultraviolet visible spectrophotometer (Beijing Puran General Instrument Co., Ltd.) Test conditions: The experiment is carried out in a closed test cabin, and the initial concentration of formaldehyde in the cabin is controlled in the range of 0.8-1.2 ppm. According to the relevant provisions of the national standards GB / T 18801-2022 "Air purifier" and GB / T 18204.2-2014 "Public place health test method Part 2: Chemical pollutants", 5 sampling points are uniformly selected in the cabin space for gas collection and analysis to evaluate the formaldehyde purification performance of the material.

[0087] Table 1 VOCs test results of different MOF composite catalytic materials

[0088] As can be seen from the table, the MOF composite catalytic material prepared by the application has significant advantages in efficient removal of VOCs. As can be seen from examples 1-10, the formaldehyde removal rate of the MOF composite catalytic material is between 60%-96% within 30 minutes, showing good formaldehyde removal performance.

[0089] As can be seen from examples 2 and 8, different MOF types have a significant impact on formaldehyde removal performance, among which the ZIF-8 / MnO2 combination performs best, while the ZIF-67 / MnO2 system has relatively low removal efficiency, indicating that the ZIF-8 / MnO2 system has more developed pore structure, stronger interface synergistic effect and higher electron transfer efficiency, which can fully exert the catalytic activity.

[0090] As can be seen from Example 1 and Comparative Example 1, the sulfamic acid modification of cellulose helps to improve the formaldehyde removal performance of the material, and the modified cellulose introduces polar functional groups, which is beneficial to the adsorption and enrichment of formaldehyde molecules.

[0091] As can be seen from Examples 2-4 and Examples 5-7, the high-temperature short-time treatment of the muffle furnace helps to improve the structural stability and pore structure of the material, thereby increasing the number of active sites.

[0092] As can be seen from Comparative Example 1 and Comparative Example 2, different types of fibers have a certain influence on the formaldehyde removal efficiency. In summary, the sulfamic acid cellulose / MOF composite material exhibits considerable application prospects in the field of formaldehyde purification through the synergistic effect of multiple components and structure regulation.

[0093] Figure 1 A physical picture of the sulfamic acid modified cellulose loaded with ZIF-8 (SC@ZIF-8) prepared for Example 2.

[0094] Figure 2 A physical picture of the composite material SC@ZIF-8 / MnO2 formed after further loading of MnO2 for Example 2.

[0095] As can be seen from Figure 1 and Figure 2 , after the growth of ZIF-8, the modified cellulose substrate still maintains the original macroscopic morphology and structural integrity, indicating that the in-situ loading process of MOF does not damage the overall morphology of the cellulose carrier. After the introduction of MnO2, the color of the composite material is obviously deepened from light color to dark brown, which directly reflects the successful introduction of MnO2 and its uniform distribution in the composite system, indicating that through the step-by-step loading process, the effective combination of metal oxide catalysts on the cellulose-MOF composite carrier can be achieved.

[0096] The present application obtains a modified cellulose substrate with rich active groups and uniform structure by mechanical and chemical modification of natural cellulose. This not only provides a large number of binding sites for subsequent MOF loading, but also enhances the interfacial compatibility between the substrate and the functional components, laying a key foundation for building a stable composite system. Further, the present application adopts a room temperature step-by-step synthesis strategy, first coordinates metal ions with cellulose, and then introduces organic ligands and catalysts for in-situ assembly. This process has mild conditions, low energy consumption and simple operation, and at the same time realizes the uniform growth of MOF structure on the cellulose substrate and the precise loading of active components, ensuring the controllability of the structure and function of the composite material.

[0097] The finally obtained MOF composite catalytic material has the three-dimensional network toughness of cellulose and the high specific surface area and multi-stage channel characteristics of the MOF material. The multi-scale composite structure is beneficial to the mass transfer and diffusion of reactants and exposes more active sites, so that the intrinsic performance of the material is significantly improved. The prepared material combines the green characteristics of biomass and the functionality of MOF, and shows great application potential in the fields of catalysis, adsorption separation, energy storage and conversion and the like. The method also provides a valuable synthesis idea for the development of other biomass-based functional composite materials.

[0098] The application has been described in detail above in combination with the embodiments, but the application is not limited to the above-described embodiments, and various changes can be made within the knowledge range of those skilled in the art without departing from the purpose of the application.

Claims

1. A MOF composite catalytic material for removing VOCs, characterized in that, The invention includes a modified cellulose three-dimensional network structure carrier on which MOF and a metal catalyst are loaded. The raw materials for preparing the modified cellulose three-dimensional network structure carrier include cotton fiber, bamboo fiber, softwood pulp fiber, hardwood pulp fiber, bagasse fiber or straw fiber. The metal catalyst includes at least one of MnO2 and Co3O4.

2. The MOF composite catalytic material for VOCs removal according to claim 1, characterized in that, The MOF is grown in situ on the modified cellulose three-dimensional network structure carrier.

3. A method for preparing the MOF composite catalytic material for VOCs removal as described in claim 1 or 2, characterized in that, Includes the following steps: S1: The cellulose raw material is mechanically crushed to obtain cellulose powder. The cellulose powder is dispersed in a solvent, and a chemical modifying agent is added to carry out an esterification reaction. After the reaction is completed, the mixture is filtered and washed to obtain the modified cellulose three-dimensional network structure carrier. S2: The modified cellulose three-dimensional network structure carrier is disintegrated and dispersed to form a dispersion. A metal salt solution is added to the dispersion and pre-coordinated by stirring at room temperature. Then, a mixed solution containing a metal catalyst and an organic ligand is added and the reaction is continued by stirring, so that the metal catalyst and MOF grow in situ on the surface of the modified cellulose three-dimensional network structure carrier. After the reaction is completed, the precursor material is obtained by filtration, washing and drying. S3: The precursor material is calcined to obtain the MOF composite catalyst material for removing VOCs.

4. The method according to claim 3, characterized in that, In step S1, the solvent includes at least one of water, methanol, ethanol, and N,N-dimethylformamide.

5. The method according to claim 3, characterized in that, The esterification reaction includes sulfation, phosphoric acid esterification or nitrate esterification; and / or, the reaction time of the esterification reaction is 0.5-6 h; and / or, the solid-liquid ratio of the esterification reaction system is 1:(5~20) g / mL; and / or, in the esterification reaction, the mass ratio of the chemical modifying agent to cellulose powder is (1~10):

1.

6. The method according to claim 3, characterized in that, In step S2, the disintegration dispersion includes one of mechanical stirring and high-speed shear dispersion; and / or, the solvent for the disintegration dispersion includes at least one of water, methanol and DMF.

7. The method according to claim 3, characterized in that, The metal salt solution includes a zinc nitrate solution or a cobalt nitrate solution; and / or, in step S2, the organic ligand includes dimethylimidazole.

8. The method according to claim 3, characterized in that, In step S2, the stirring time for the pre-matching is 1~24h.

9. The method according to claim 3, characterized in that, The molar ratio of the modified cellulose three-dimensional network structure carrier, metal salt solution, organic ligand, and metal catalyst is 1:(1~10):(1~10):(0.1~5).

10. An air purification device, characterized in that, The air purification device includes the MOF composite catalytic material for removing VOCs as described in claim 1 or 2.

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