Preparation and application of amino acid grafted modified covalent organic framework composite material

Abstract

The invention relates to the technical field of air purification materials, and particularly discloses an amino acid grafted modified covalent organic framework composite material as well as a preparation method and application thereof. The composite material comprises a covalent organic framework matrix and amino acid grafted through covalent bonds, the covalent organic framework matrix has a porous crystal structure, and the amino acid is connected with the matrix through an amido bond or a carbon-nitrogen bond. The preparation method comprises the four main steps of covalent organic framework matrix synthesis, matrix activation, amino acid grafting and product purification. The composite material provided by the invention can be used for indoor air purification, formaldehyde removal of automotive trim and formaldehyde adsorption process in industrial waste gas treatment. The material has a high specific surface area and a rich porous structure, combines specific interaction of amino acid functional groups and formaldehyde molecules, and shows excellent formaldehyde adsorption capacity and selective adsorption performance. The preparation method disclosed by the invention is mild in process condition, and controllable adjustment of material performance is realized by accurately controlling grafting parameters.

Description

Technical Field

[0001] This application relates to the field of air purification materials technology, and more specifically, to the preparation and application of an amino acid grafted modified covalent organic framework composite material. Background Technology

[0002] Formaldehyde is a typical volatile organic pollutant with strong irritant properties. Long-term exposure can cause respiratory diseases, allergic reactions, and even induce cancer, posing a significant threat to human health. Automotive interior materials continuously release formaldehyde; the formaldehyde release period in new cars can be 1-3 years. The enclosed space inside a car leads to rapid formaldehyde accumulation, and the increased temperature inside the car after exposure to the summer sun further accelerates the formaldehyde release rate, becoming a core factor affecting in-vehicle air quality and harming the health of drivers and passengers. Therefore, developing efficient and stable formaldehyde adsorption materials suitable for the in-vehicle environment has become a key requirement in the automotive air purification field.

[0003] Currently used formaldehyde adsorption materials include activated carbon, molecular sieves, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and amino acids. However, all of these have significant limitations in automotive applications: activated carbon has low adsorption capacity and is prone to desorption at high temperatures and cannot be regenerated; molecular sieves have extremely low adsorption capacity, making it difficult to meet rapid purification needs; MOFs are prone to framework collapse in humid environments and have poor processing adaptability; amino acids tend to aggregate when used alone, have weak binding force with conventional carriers, and are prone to detachment; existing covalent organic frameworks lack active sites that strongly interact with formaldehyde, resulting in insufficient adsorption capacity and poor regeneration performance. These common shortcomings of existing materials make it difficult for them to simultaneously possess high adsorption capacity and excellent cycling stability in the complex environment of vehicles, thus failing to meet the core usage requirements of formaldehyde adsorption materials in automotive scenarios. Summary of the Invention

[0004] To address the problems of low adsorption capacity, poor selectivity, and insufficient stability in existing formaldehyde adsorption materials, this application provides a method for preparing and applying an amino acid-grafted modified covalent organic framework composite material.

[0005] In a first aspect, this application provides an amino acid-grafted modified covalent organic framework composite material, which adopts the following technical solution:

[0006] An amino acid-grafted modified covalent organic framework composite material comprises a covalent organic framework matrix and amino acids grafted onto the covalent organic framework matrix via covalent bonds; the covalent organic framework matrix has a porous crystal structure with a specific surface area of ​​1800-2500 m² / g, a pore size of 1.5-2.2 nm, and a surface active functional group density of ≥3.0 mmol / g; the amino acids are connected to the covalent organic framework matrix via amide bonds or carbon-nitrogen bonds formed by reductive amination, and the grafting amount of the amino acids is controlled by the molar ratio of amino acids to active functional groups in the covalent organic framework matrix.

[0007] By adopting the above technical solution, a covalent organic framework with a specific porous crystal structure is selected as the matrix material, and its high-density active functional groups are used to covalently graft amino acid molecules. When the matrix surface contains amino groups, amide bonds are used for connection, and when the matrix surface contains aldehyde groups, carbon-nitrogen bonds are formed through reductive amination. At the same time, the grafting density is controlled by precisely adjusting the molar ratio of amino acids to matrix active functional groups. This structural design allows amino acid molecules to be uniformly and stably fixed in the framework channels, which not only maintains the original high specific surface area of ​​the material, but also introduces active sites that can specifically interact with formaldehyde molecules, thereby constructing a composite adsorption material system with a regular pore structure and abundant interaction sites.

[0008] Preferably, the covalent organic framework matrix is ​​synthesized from a triazine cyclic monomer and an aromatic aldehyde monomer via a Schiff base reaction; the triazine cyclic monomer is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, and the aromatic aldehyde monomer is selected from terephthalaldehyde or biphenyl dicarboxaldehyde.

[0009] By employing the above-described technical solution, and using 2,4,6-tris(4-aminophenyl)-1,3,5-triazine with a rigid triazine ring structure as the building unit, a covalent organic framework matrix is ​​constructed via a Schiff base reaction with linear aromatic aldehydes such as terephthalaldehyde or biphenyl dialdehyde. This choice is based on the fact that the symmetry and rigidity of the triazine ring facilitate the formation of a regular pore structure, while the linear characteristics of terephthalaldehyde and biphenyl dialdehyde can match the triazine ring building unit to form a stable framework system. This specific monomer combination ensures that the synthesized covalent organic framework matrix possesses high specific surface area, regular pore size distribution, and sufficient density of surface-active functional groups, providing ample and uniform anchoring sites for subsequent covalent grafting of amino acids.

[0010] Preferably, the amino acid is selected from lysine, glycine, or glutamic acid; the lysine contains two amino groups and one carboxyl group.

[0011] By employing the above technical solutions, lysine, with its multifunctional structure containing two amino groups and one carboxyl group, can form multi-site connections with covalent organic framework matrices. Glycine, with its minimal molecular size, facilitates high-density grafting within the framework channels. Glutamic acid, through its additional carboxyl group, provides more interaction sites. The selection of these specific amino acids, based on differences in their functional group types, molecular sizes, and spatial configurations, can adapt to various grafting environments and application requirements. By rationally utilizing the structural characteristics of various amino acids, precise control over the surface properties and pore environment of the composite material can be achieved.

[0012] Secondly, this application provides a method for preparing amino acid-grafted modified covalent organic framework composite materials, using the following technical solution:

[0013] An application of an amino acid-grafted modified covalent organic framework composite material for formaldehyde adsorption includes the following steps:

[0014] S1. Synthesis of covalent organic framework matrix: Triazine cyclic monomers and aromatic aldehyde monomers are dissolved in an organic solvent, an acid catalyst is added, and after ultrasonic mixing and freeze degassing, the mixture is heated at 100-130°C for 2-4 days to obtain a covalent organic framework matrix.

[0015] S2. Matrix activation: The covalent organic framework matrix is ​​dispersed in a polar solvent, an alkaline activator is added, and the mixture is stirred and activated at room temperature for 25-35 min. After centrifugation and drying, the activated covalent organic framework matrix is ​​obtained.

[0016] S3, Amino acid grafting: Dissolve the activated covalent organic framework matrix and amino acids in water or organic solvent, add a catalyst, adjust the pH to 7.0-8.0, and stir the reaction at 50-70°C for 6-12 hours.

[0017] S4. Product purification: The product after the grafting reaction was centrifuged, washed alternately with water and ethanol, and then dried under vacuum to obtain amino acid grafted modified covalent organic framework composite material.

[0018] By employing the above technical solution, using 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and terephthalaldehyde or biphenyl dicarboxaldehyde as building blocks, and in a mixed solvent system of mesitylene and 1,4-dioxane, with acetic acid as a catalyst, a homogeneous mixture is formed through ultrasonic dispersion. This mixture is then subjected to cryogenic degassing to remove dissolved oxygen, followed by thermal reaction under sealed conditions to form a covalent organic framework matrix with regular channels. Subsequently, the obtained matrix is ​​dispersed in anhydrous ethanol, and triethylamine is added for surface activation treatment to enhance the reactivity of the amino functional groups. Then… In an aqueous or organic phase system with a pH of 7.0-8.0, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide or sodium borohydride is added as a catalyst to induce amino acids such as lysine, glycine, or glutamic acid to undergo amidation or reductive amination reactions with the activated matrix. Finally, the solid product is obtained by centrifugation, and unreacted monomers and catalyst residues are removed by alternating washing with deionized water and anhydrous ethanol. Vacuum drying is then performed under specific temperature conditions to finally obtain an amino acid grafted modified composite material with a complete structure and controllable surface properties.

[0019] Preferably, in step S1, the molar ratio of the triazine cyclic monomer to the aromatic aldehyde monomer is 1:1.2 to 1:1.8; the organic solvent is a mixed solvent of mesitylene and 1,4-dioxane, with a volume ratio of 5:6 to 6:1; the acid catalyst is acetic acid, with a concentration of 4-7 mol / L, and the amount added is 10-20% of the total volume of the organic solvent.

[0020] By employing the above technical solution, and controlling the molar ratio of triazine cyclic monomers to aromatic aldehyde monomers within the range of 1:1.2 to 1:1.8, an appropriate excess of aldehyde functional groups in the reaction system is ensured, promoting the full participation of the amino groups of the triazine cyclic monomers in the condensation reaction. A mixed solvent system is composed of mesitylene and 1,4-dioxane in a volume ratio of 5:6 to 6:1. The high boiling point of mesitylene maintains the stability of the reaction temperature, while the good solubility of 1,4-dioxane ensures sufficient dispersion of the monomers. Acetic acid at a concentration of 4-7 mol / L is used as an acid catalyst, and its addition is controlled to 10-20% of the total volume of the organic solvent, promoting the forward shift of the Schiff base reaction equilibrium while avoiding excessive acidity that could lead to side reactions. The synergistic combination of these specific process parameters provides the necessary reaction environment and kinetic conditions for the orderly assembly of the covalent organic framework matrix.

[0021] Preferably, in step S2, the polar solvent is anhydrous ethanol, and the amount used is 40-60 mL per gram of covalent organic framework matrix; the alkaline activator is triethylamine, and the amount added is 0.4-0.6 mL per gram of covalent organic framework matrix.

[0022] By employing the above technical solution, using anhydrous ethanol as a polar solvent and controlling its dosage at 40-60 mL per gram of covalent organic framework matrix, the material can be fully dispersed and a uniform suspension system can be formed. Simultaneously, triethylamine is used as a basic activator, added at 0.4-0.6 mL per gram of matrix, and activation is carried out at room temperature. This specific ratio ensures that the functional groups on the surface of the covalent organic framework are adequately activated, avoiding aggregation caused by excessive activator and ensuring sufficient exposure of active sites required for subsequent grafting reactions, thus creating a suitable surface environment for the effective bonding of amino acid molecules.

[0023] Preferably, in step S3, the molar ratio of the amino acid to the active functional group in the activated covalent organic framework matrix is ​​1:1 to 1:3; the catalyst is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide or sodium borohydride, and the amount added is 0.05 g to 0.1 g per gram of activated covalent organic framework matrix.

[0024] By employing the above technical solution and controlling the molar ratio of amino acids to active functional groups in the activated covalent organic framework matrix to 1:1 to 1:3, both sufficient contact between amino acid molecules and the matrix surface is ensured, while avoiding aggregation caused by excess amino acids. 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is selected as the catalyst for the amidation reaction, or sodium borohydride is selected as the reducing agent for the reductive amination reaction, with the addition amount controlled to 0.05 g to 0.1 g per gram of activated matrix. This dosage range effectively promotes covalent bond formation while avoiding the adverse effects of catalyst residue on material properties. Through the synergistic control of the above specific parameters, uniform grafting and stable bonding of amino acid molecules on the surface of the covalent organic framework matrix are achieved.

[0025] Preferably, in step S3, when the surface of the covalent organic framework matrix contains amino groups, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is used as a catalyst to form amide bond grafting; when the surface of the covalent organic framework matrix contains aldehyde groups, sodium borohydride is used as a reducing agent to convert the Schiff base intermediate into carbon-nitrogen bond grafting.

[0026] By employing the above technical solutions, differentiated grafting strategies are used for covalent organic framework matrices with different surface functional groups. When the matrix surface is rich in amino groups, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is selected as a catalyst to activate the carboxyl groups of amino acid molecules to form active intermediates, which then undergo amidation reactions with the amino groups on the matrix surface to form stable amide bonds. When the matrix surface contains aldehyde groups, sodium borohydride is used as a reducing agent to allow the amino groups of amino acid molecules to first react with the aldehyde groups to form Schiff base intermediates, and then the unstable carbon-nitrogen double bonds are converted into stable carbon-nitrogen single bonds through a reduction reaction. This strategy of selecting appropriate grafting methods based on the characteristics of the matrix surface ensures the effective fixation and stable bonding of amino acid molecules on different types of covalent organic framework matrices.

[0027] Preferably, in step S4, the washing process includes washing with deionized water and ethanol alternately 3-5 times; the drying conditions are drying in a vacuum environment at 60-80°C for 8-24 hours.

[0028] By employing the above-mentioned technical solution, and using an alternating washing process of deionized water and ethanol three to five times, water-soluble impurities and inorganic salt residues are removed using deionized water, while organic solvent residues and unreacted amino acid molecules are effectively removed using ethanol. This alternating washing purification method achieves the stepwise removal of impurities of different polarities. Subsequently, drying is carried out in a vacuum environment at 60-80°C for 8-24 hours. This temperature range ensures sufficient evaporation of solvent molecules while preventing damage to the material's skeletal structure due to excessive temperature, and the vacuum environment effectively prevents oxidative deterioration of the material during the drying process. This systematic post-processing ensures that the final composite material possesses pure surface properties and a stable skeletal structure.

[0029] Secondly, this application provides an application of amino acid grafted modified covalent organic framework composite materials, employing the following technical solution:

[0030] An application of an amino acid-grafted modified covalent organic framework composite material, wherein the composite material can be used in formaldehyde adsorption processes in indoor air purification, formaldehyde removal from automotive interiors, or industrial waste gas treatment.

[0031] By adopting the above technical solutions, the composite material can be processed into different forms to suit various application scenarios: For indoor air purification, the material can be loaded onto honeycomb ceramic or non-woven fabric substrates to form filter modules, which can then be installed in the air duct system of air purification equipment; for the formaldehyde removal needs of automotive interiors, the material can be mixed with a polymer carrier to form a coating slurry, which can then be sprayed onto the surfaces of interior components such as dashboards and seat backs; in industrial waste gas treatment, the material can be filled into fixed-bed adsorption towers to form adsorption units with a certain bed height. These applications fully utilize the specific interaction between the amino acid functional groups in the material and formaldehyde molecules, as well as the high loading capacity brought by the large specific surface area of ​​the covalent organic framework. At the same time, its stable chemical structure ensures long-term reliability under different working conditions.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. This application adopts a technical solution of grafting amino acids onto a covalent organic framework matrix with a specific porous crystal structure and surface functional group density via covalent bonds. Due to the covalent bonding method, the amino acid molecules are stably immobilized on the material framework. At the same time, the ordered pore structure of the matrix provides an ideal diffusion path for formaldehyde molecules, resulting in a significant technical effect of high adsorption capacity and excellent cycle stability in the formaldehyde adsorption application.

[0034] 2. In this application, triazine ring monomers and specific aromatic aldehyde monomers are preferably used to construct a covalent organic framework matrix. Due to the electron-rich properties of the triazine ring and the synergistic effect of the aromatic aldehyde, the chemical activity of the material surface is enhanced. At the same time, the selected amino acids such as lysine have multiple active functional groups, which results in the material having a stronger chemical adsorption capacity for formaldehyde molecules and a wider range of environmental adaptability.

[0035] 3. The method of this application achieves effective control of the amount of amino acid grafting by precisely controlling the matrix activation conditions and the material ratio, reaction pH and temperature parameters in the amino acid grafting process. At the same time, the stepwise purification process is used to ensure the purity of the product. Therefore, the preparation effect of the composite material with regular structure, stable performance and good batch consistency is obtained. Attached Figure Description

[0036] Figure 1 This is a flowchart of a method for preparing an amino acid grafted modified covalent organic framework composite material provided in this application;

[0037] Figure 2 This is a flowchart illustrating the synthesis route of COF in the field of air purification materials technology (TAPT-TPA) provided in this application.

[0038] Figure 3This is a schematic diagram illustrating the reaction principle between amino acids and formaldehyde provided in this application. Detailed Implementation

[0039] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0040] Technical concept:

[0041] In practical applications such as automotive applications, formaldehyde adsorption materials often struggle to balance high adsorption performance with long-term stability. The core reason lies in the unreasonable design of the carrier structure and the inappropriate combination of active components and the carrier. Existing carriers such as activated carbon and molecular sieves lack regular and suitable porous structures, failing to provide sufficient adsorption sites and diffusion channels. Materials in the fields of MOFs and COFs (unmodified air purification materials) either lack sufficient skeletal stability or lack chemically active sites that strongly interact with formaldehyde. Amino acid-based active components and conventional carriers are often physically mixed or weakly bonded, leading to easy aggregation and detachment, resulting in low utilization of active sites. Furthermore, designs based solely on physical adsorption or single chemical adsorption cannot achieve synergistic optimization of adsorption capacity and stability.

[0042] This technical solution addresses the aforementioned issues through precise design of core technologies: a covalent organic framework with specific surface area, pore size, and surface-active functional group density is selected as the matrix. Its regular porous structure and sufficient active sites provide a dual basis for physical adsorption and amino acid grafting. Amide bonds or carbon-nitrogen bonds formed by reductive amination are used to achieve covalent bonding between amino acids and the matrix, preventing amino acid aggregation and detachment. The grafting amount is controlled by adjusting the molar ratio of amino acids to matrix active functional groups, precisely matching the synergistic ratio of chemically active sites to physical adsorption sites. Ultimately, the synergistic effect of physical and chemical adsorption overcomes the deficiencies of existing technologies in carrier structure, component binding, and adsorption mechanisms.

[0043] The following are the main raw materials and reagents used in the examples and comparative examples, and their sources and specifications are as follows; unless otherwise specified, all reagents are commercially available analytical grade or higher products:

[0044] 1, 2, 4, 6 Air purification material technology field - Air purification material technology field three Air purification material technology field (4 Air purification material technology field - Air purification material technology field aminophenyl) - 1, 3, 5 Air purification material technology field - Air purification material technology field triazine was purchased from Shanghai Yuanye Biotechnology Co., Ltd., item number: S94010;

[0045] 2. Terephthalaldehyde was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S30211;

[0046] 3. Biphenyl dimethylformaldehyde was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S39077;

[0047] 4. In the field of air purification materials technology, lysine was purchased from Chengdu Baishixing Technology Industry Co., Ltd., with a purity of 99%.

[0048] 5. Glycine was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S20159;

[0049] 6. In the field of air purification materials technology, glutamic acid was purchased from Shaanxi Chenming Biotechnology Co., Ltd., item number: 122401;

[0050] 7. Mesitylene was purchased from Shandong Jiuan Chemical Co., Ltd., CAS: 108-67-8;

[0051] 8.1,4 Air Purification Materials Technology Field - Dioxane was purchased from Shandong Yinglang Chemical Co., Ltd., purity: 99%;

[0052] 9. N,N Air Purification Material Technology Field - Dimethylformamide was purchased from Yangzhou Phoenix Island Chemical Co., Ltd., item number: 007;

[0053] 10. Triethylamine was purchased from Shandong Mingyu Supply Chain Management Co., Ltd., CAS: 121-44-8;

[0054] 11. 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide was purchased from Shanghai Yuanye Biotechnology Co., Ltd., item number: S30054.

[0055] Example 1

[0056] This embodiment provides an amino acid-grafted modified covalent organic framework composite material and its preparation method, the specific steps of which are as follows:

[0057] S1. Synthesis of covalent organic framework matrix: 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and terephthalaldehyde were dissolved in an organic solvent, an acid catalyst was added, and after ultrasonic mixing and freeze degassing, the mixture was heated at 115°C for 3 days to obtain a covalent organic framework matrix.

[0058] The molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to terephthalaldehyde is 1:1.5; the organic solvent is a mixture of mesitylene and 1,4-dioxane in a volume ratio of 5.5:1; the acid catalyst is acetic acid at a concentration of 5.5 mol / L, and the amount added is 15% of the total volume of the organic solvent.

[0059] S2. Matrix activation: The covalent organic framework matrix is ​​dispersed in a polar solvent, an alkaline activator is added, and the mixture is stirred and activated at room temperature for 30 min. After centrifugation and drying, the activated covalent organic framework matrix is ​​obtained.

[0060] The polar solvent is anhydrous ethanol, used at a rate of 50 mL per gram of covalent organic framework matrix; the basic activator is triethylamine, added at a rate of 0.5 mL per gram of covalent organic framework matrix.

[0061] S3, Amino acid grafting: The activated covalent organic framework matrix and lysine were dissolved in deionized water, a catalyst was added, the pH was adjusted to 7.5, and the reaction was stirred at 60°C for 9 hours.

[0062] The molar ratio of lysine to active functional groups in the activated covalent organic framework matrix is ​​1:2; the catalyst is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and the addition amount is 0.075g per gram of activated covalent organic framework matrix.

[0063] When the surface of the covalent organic framework matrix contains amino groups, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is used as a catalyst to form amide bond grafting.

[0064] S4. Product purification: The grafted product was centrifuged, washed alternately with water and ethanol, and then dried under vacuum to obtain an amino acid grafted modified covalent organic framework composite material.

[0065] The washing process includes washing with deionized water and ethanol alternately four times; the drying conditions are drying in a vacuum environment at 70°C for 16 hours.

[0066] Example 2

[0067] This embodiment provides an amino acid-grafted modified covalent organic framework composite material and its preparation method, the specific steps of which are as follows:

[0068] S1. Synthesis of covalent organic framework matrix: 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and biphenyl dicarboxaldehyde were dissolved in an organic solvent, an acid catalyst was added, and after ultrasonic mixing and freeze degassing, the mixture was heated at 100°C for 2 days to obtain a covalent organic framework matrix.

[0069] The molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to biphenyl dicarboxaldehyde is 1:1.2; the organic solvent is a mixture of mesitylene and 1,4-dioxane in a volume ratio of 5:1; the acid catalyst is acetic acid at a concentration of 4 mol / L, and the amount added is 10% of the total volume of the organic solvent.

[0070] S2. Matrix activation: The covalent organic framework matrix is ​​dispersed in a polar solvent, an alkaline activator is added, and the mixture is stirred and activated at room temperature for 25 min. After centrifugation and drying, the activated covalent organic framework matrix is ​​obtained.

[0071] The polar solvent is anhydrous ethanol, used at a rate of 40 mL per gram of covalent organic framework matrix; the basic activator is triethylamine, added at a rate of 0.4 mL per gram of covalent organic framework matrix.

[0072] S3, Amino acid grafting: The activated covalent organic framework matrix and glycine were dissolved in N,N-dimethylformamide, a catalyst was added, the pH was adjusted to 7.0, and the reaction was stirred at 50°C for 6 hours.

[0073] Wherein: the molar ratio of glycine to the active functional groups in the activated covalent organic framework matrix is ​​1:1; the catalyst is sodium borohydride, and the addition amount is 0.05g per gram of activated covalent organic framework matrix;

[0074] When the surface of the covalent organic framework matrix contains aldehyde groups, sodium borohydride is used as a reducing agent to convert the Schiff base intermediate into carbon-nitrogen bond grafts.

[0075] S4. Product purification: The grafted product was centrifuged, washed alternately with water and ethanol, and then dried under vacuum to obtain an amino acid grafted modified covalent organic framework composite material.

[0076] The washing process includes three alternating washes with deionized water and ethanol; the drying conditions are drying in a vacuum environment at 60°C for 8 hours.

[0077] Example 3

[0078] This embodiment provides an amino acid-grafted modified covalent organic framework composite material and its preparation method, the specific steps of which are as follows:

[0079] S1. Synthesis of covalent organic framework matrix: 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and terephthalaldehyde were dissolved in an organic solvent, an acid catalyst was added, and after ultrasonic mixing and freeze degassing, the mixture was heated at 130°C for 4 days to obtain a covalent organic framework matrix.

[0080] The molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to terephthalaldehyde is 1:1.8; the organic solvent is a mixture of mesitylene and 1,4-dioxane in a volume ratio of 6:1; the acid catalyst is acetic acid at a concentration of 7 mol / L, and the amount added is 20% of the total volume of the organic solvent.

[0081] S2. Matrix activation: The covalent organic framework matrix is ​​dispersed in a polar solvent, an alkaline activator is added, and the mixture is stirred and activated at room temperature for 35 min. After centrifugation and drying, the activated covalent organic framework matrix is ​​obtained.

[0082] The polar solvent is anhydrous ethanol, used at a rate of 60 mL per gram of covalent organic framework matrix; the basic activator is triethylamine, added at a rate of 0.6 mL per gram of covalent organic framework matrix.

[0083] S3, Amino acid grafting: The activated covalent organic framework matrix and glutamic acid were dissolved in deionized water, a catalyst was added, the pH was adjusted to 8.0, and the reaction was stirred at 70°C for 12 hours.

[0084] The molar ratio of glutamic acid to the active functional groups in the activated covalent organic framework matrix is ​​1:3; the catalyst is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and the addition amount is 0.1g per gram of activated covalent organic framework matrix.

[0085] When the surface of the covalent organic framework matrix contains amino groups, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is used as a catalyst to form amide bond grafting.

[0086] S4. Product purification: The grafted product was centrifuged, washed alternately with water and ethanol, and then dried under vacuum to obtain an amino acid grafted modified covalent organic framework composite material.

[0087] The washing process includes five alternating washes with deionized water and ethanol; the drying conditions are drying in a vacuum environment at 80°C for 24 hours.

[0088] The amino acid grafted modified covalent organic framework composite materials prepared in Examples 1-3 above were used in the formaldehyde adsorption process of indoor air purification, formaldehyde removal from automotive interiors and industrial waste gas treatment, respectively, and all showed excellent formaldehyde adsorption performance.

[0089] Comparative Example 1

[0090] The only difference between this comparative example and Example 1 is that the amino acid grafting step S3 and the related activation step S2 were omitted, and the performance test was performed directly using the unmodified TAPT-TPACOF matrix material.

[0091] Comparative Example 2

[0092] The only difference between this comparative example and Example 1 is that commercially available coal-based activated carbon is used as the comparative material, which does not contain any covalent organic framework structure or amino acid functional groups.

[0093] Comparative Example 3

[0094] The only difference between this comparative example and Example 1 is that the amino acid is combined with the COF matrix through physical mixing, rather than covalent grafting. Specifically, lysine and TAPT-TPACOF are simply stirred and mixed in an aqueous solution and then dried, without undergoing an amide grafting reaction catalyzed by EDC.

[0095] Comparative Example 4

[0096] The only difference between this comparative example and Example 1 is that silica is used instead of the covalent organic framework as the carrier material, while other preparation conditions remain unchanged.

[0097] I. Formaldehyde Static Adsorption Capacity Test

[0098] According to GB / T18883-2022 standard, tests were conducted in a constant temperature and humidity environment of 23℃ and 50% relative humidity. 0.1g of each of the amino acid grafted modified covalent organic framework composite materials prepared in Examples 1, 2, and 3, as well as commercially available coal-based activated carbon (Comparative Example 1), unmodified TAPT-TPACOF matrix (Comparative Example 2), amino acid physically mixed COF material (Comparative Example 3), and silica-loaded amino acid material (Comparative Example 4) were placed in seven 500mL sealed glass containers. Formaldehyde standard gas was injected into each container to achieve an initial formaldehyde concentration of 1.0mg / m³. Gas samples were collected from each container every 15 minutes using a borosilicate glass absorption tube. The absorbance of each sample was measured at 630nm using phenol reagent spectrophotometry, and the remaining formaldehyde concentration was calculated. Monitoring continued until the adsorption of each material reached equilibrium. The static adsorption capacity and adsorption equilibrium time of each material were recorded to compare the basic formaldehyde adsorption capacity and adsorption rate advantages of different materials.

[0099] II. Dynamic Formaldehyde Purification Efficiency Test

[0100] Referring to the GB / T18883-2022 standard and simulating actual vehicle and indoor use scenarios, a 1m³ environmental test chamber was used for testing. The temperature inside the test chamber was controlled at 23℃, the relative humidity at 50%, the air exchange rate at 1.0±0.05 times / h, and the air circulation velocity at 0.3m / s. 0.5g of each of the composite materials of Examples 1-3 and Comparative Examples 1-4 were evenly laid on the sample rack inside the test chamber. Formaldehyde standard gas was injected into the chamber to make the initial formaldehyde concentration reach 1.0mg / m³. Gas samples were collected from each test chamber at 5min, 15min, 30min, and 60min after the start of the test using a multi-channel gas sampling interface. The formaldehyde concentration at each time point was analyzed using GC-MS, and the formaldehyde removal rate of each material at different time points was calculated. The ability of each material to reduce the formaldehyde concentration in the chamber to below the national standard limit within 30min was compared to reflect the formaldehyde purification efficiency advantage of the materials in a real dynamic environment.

[0101] III. Combined Test of Recycling and High Humidity Stability

[0102] Referring to the relevant testing requirements of GB / T18883-2022 standard, a high humidity stability test was first conducted. The composite materials of Examples 1-3 and the materials of Comparative Examples 1-4 were placed in an environmental chamber at 23°C and 80% relative humidity for 72 hours for static treatment. After treatment, the static adsorption capacity of each material was measured using the same method as the formaldehyde static adsorption capacity test, and the capacity retention rate after high humidity treatment was calculated. Subsequently, a cyclic regeneration test was conducted. Each material after high humidity treatment was placed in a vacuum environment at 120°C for 2 hours for desorption to complete one regeneration. This regeneration process was repeated 5 times. After each regeneration, the adsorption capacity of each material was measured using the same static adsorption capacity test method. The capacity data after each regeneration was recorded, and the capacity retention rate after 5 cycles was calculated. By comparing the capacity changes before and after high humidity treatment and the performance degradation after multiple regenerations, the environmental adaptability and long-term cyclic stability of each material were comprehensively compared.

[0103] The basic formaldehyde adsorption performance test data are shown in Table 1.

[0104] Table 1:

[0105] Material type Static adsorption capacity (mg / g) Adsorption equilibrium time (min) Active site exposure rate (%) Example 1 420 45 85 Example 2 380 55 82 Example 3 450 40 88 Comparative Example 1 110 180 - Comparative Example 2 185 120 40 Comparative Example 3 210 100 38 Comparative Example 4 95 160 35

[0106] The test data for dynamic purification and selective adsorption performance are shown in Table 2.

[0107] Table 2:

[0108] Material type Dynamic formaldehyde concentration (mg / m³) over 30 minutes Dynamic 30-minute formaldehyde removal rate (%) Formaldehyde selectivity (%) Example 1 0.08 92 92 Example 2 0.10 90 90 Example 3 0.07 93 94 Comparative Example 1 0.65 35 52 Comparative Example 2 0.35 65 68 Comparative Example 3 0.28 72 70 Comparative Example 4 0.70 30 55

[0109] The high humidity stability test data are shown in Table 3.

[0110] Table 3:

[0111] Material type Static adsorption capacity (mg / g) after high humidity treatment Capacity retention rate (%) after high humidity treatment Example 1 390 93 Example 2 345 91 Example 3 425 94 Comparative Example 1 55 50 Comparative Example 2 115 62 Comparative Example 3 126 60 Comparative Example 4 48 51

[0112] The test data for recycling performance and structural stability are shown in Table 4.

[0113] Table 4:

[0114] Material type Static adsorption capacity after one regeneration (mg / g) Static adsorption capacity (mg / g) after 3 regenerations Static adsorption capacity (mg / g) after 5 regenerations Capacity retention rate (%) after 5 regenerations Amino acid shedding rate (%) after vibration test Example 1 410 405 400 95 <1 Example 2 370 360 350 93 <1 Example 3 440 435 430 96 <1 Comparative Example 1 95 75 65 59 - Comparative Example 2 165 145 135 73 - Comparative Example 3 180 150 95 45 12 Comparative Example 4 75 60 40 40 15

[0115] Combining Examples 1-3 and Comparative Example 1 with Tables 1-4, it can be seen that the original covalent organic framework material without amino acid grafting modification has significant deficiencies in formaldehyde adsorption performance. This fully demonstrates that introducing amino acid molecules into the material framework through chemical grafting can effectively increase the active adsorption sites on the material surface, significantly improving the formaldehyde molecule capture capacity. Simultaneously, the chemical grafting structure also ensures the stability of the material during recycling, avoiding the loss of active components during regeneration.

[0116] Based on Examples 1-3 and Comparative Example 2, and referring to Tables 1 to 4, it can be seen that traditional porous materials such as activated carbon are far inferior to amino acid-grafted modified covalent organic framework materials in formaldehyde adsorption performance. This indicates that the highly ordered pore structure of the covalent organic framework material itself provides an ideal diffusion path for formaldehyde molecules, while its functionalizable characteristics allow amino acids to be uniformly distributed and stably immobilized, thereby achieving a synergistic effect of physical and chemical adsorption, a characteristic not possessed by traditional adsorption materials.

[0117] As can be seen from Examples 1-3 and Comparative Example 3, and in conjunction with Tables 1 to 4, simple physical mixing methods cannot achieve the modification effect of chemical grafting. When amino acid molecules are bound to the material through physical mixing, they are easily detached and lost during recycling, leading to a rapid decline in adsorption performance. This confirms the unique advantage of covalent bonding in immobilizing active components, ensuring a strong connection between amino acid molecules and the material backbone, thereby maintaining the stability of the material during long-term use.

[0118] As can be seen from Examples 1-3 and Comparative Example 4, and in conjunction with Tables 1 to 4, the choice of support material has a decisive impact on the performance of the final product. Compared with traditional supports such as silica, covalent organic framework materials, due to their designable pore structure and abundant surface functional groups, provide a more ideal immobilization platform for amino acids. This not only improves the availability of active sites but also enhances the overall structural stability of the material, enabling it to maintain excellent adsorption performance even under harsh operating environments.

[0119] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An amino acid-grafted modified covalent organic framework composite material, characterized in that: The amino acid grafted and modified covalent organic framework composite material comprises a covalent organic framework matrix and amino acids grafted on the covalent organic framework matrix by covalent bonds; the covalent organic framework matrix has a porous crystal structure, a specific surface area of 1800-2500 m² / g, a pore size of 1.5-2.2 nm, and a surface active functional group density of ≥3.0 mmol / g; the amino acids are connected to the covalent organic framework matrix by amide bonds or carbon-nitrogen bonds formed by reductive amination, and the grafting amount of the amino acids is controlled by the molar ratio of the amino acids to the active functional groups in the covalent organic framework matrix.

2. The amino acid grafted covalent organic framework composite material of claim 1, wherein: The covalent organic framework matrix is synthesized by Schiff base reaction of a triazine ring monomer and an aromatic aldehyde monomer; the triazine ring monomer is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, and the aromatic aldehyde monomer is selected from p-phenylenedimethylal or biphenyldimethylal.

3. The amino acid grafted covalent organic framework composite of claim 1, wherein: The amino acid is selected from lysine, glycine or glutamic acid; the lysine contains two amino groups and one carboxyl group.

4. A method for preparing an amino acid-grafted modified covalent organic framework composite material, characterized in that, The amino acid grafted and modified covalent organic framework composite material comprises the following steps: S1, covalent organic framework matrix synthesis: dissolving a triazine ring monomer and an aromatic aldehyde monomer in an organic solvent, adding an acid catalyst, ultrasonic mixing, freeze-drying treatment, and then heating at 100-130 °C for 2-4 days to obtain a covalent organic framework matrix; S2, matrix activation: dispersing the covalent organic framework matrix in a polar solvent, adding a basic activator, stirring at room temperature for 25-35 min, and then centrifuging and drying to obtain an activated covalent organic framework matrix; S3, amino acid grafting: dissolving the activated covalent organic framework matrix and amino acids in water or an organic solvent, adding a catalyst, adjusting the pH to 7.0-8.0, and stirring at 50-70 °C for 6-12 h; S4, product purification: centrifuging the product after the grafting reaction, washing with water and ethanol alternately, and then drying under vacuum to obtain the amino acid grafted and modified covalent organic framework composite material.

5. The method of claim 4, wherein the method further comprises: In step S1, the molar ratio of the triazine ring monomer to the aromatic aldehyde monomer is 1:1.2 to 1:1.8; the organic solvent is a mixed solvent of mesitylene and 1,4-dioxane with a volume ratio of 5:6 to 6:1; and the acid catalyst is acetic acid with a concentration of 4-7 mol / L and an addition amount of 10-20% of the total volume of the organic solvent.

6. The method of claim 4, wherein the method further comprises: In step S2, the polar solvent is anhydrous ethanol with an amount of 40-60 mL per gram of the covalent organic framework matrix; and the basic activator is triethylamine with an addition amount of 0.4-0.6 mL per gram of the covalent organic framework matrix.

7. The method of claim 4, wherein the method further comprises: In step S3, the molar ratio of the amino acid to the active functional groups in the activated covalent organic framework matrix is 1:1 to 1:3; and the catalyst is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide or sodium borohydride with an addition amount of 0.05 g to 0.1 g per gram of the activated covalent organic framework matrix.

8. The method of claim 4, wherein the method further comprises: In step S3, when the surface of the covalent organic framework matrix contains amino groups, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide is used as a catalyst to form amide bond grafting; when the surface of the covalent organic framework matrix contains aldehyde groups, sodium borohydride is used as a reducing agent to convert Schiff base intermediates into carbon-nitrogen bond grafting.

9. The method of claim 4, wherein the method further comprises: In step S4, the washing process includes alternating washing with deionized water and ethanol for 3-5 times; the drying conditions are 8-24 h of drying in a vacuum environment at 60-80°C.

10. Use of an amino acid-grafted modified covalent organic framework composite material, characterized in that An amino acid grafted modified covalent organic framework composite material according to any one of claims 1-3, wherein the composite material is used for indoor air purification, formaldehyde removal of automotive interiors, or formaldehyde adsorption in industrial waste gas treatment.

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