Collagen fiber-covalent organic framework composite membrane and preparation method thereof

Abstract

The invention belongs to the technical field of composite materials, and discloses a collagenous fiber-covalent organic framework composite membrane and a preparation method thereof. The collagenous fiber-covalent organic framework composite membrane comprises: a collagenous fiber substrate having a three-dimensional network porous structure; the covalent organic framework material is loaded on the surface and pore walls of the collagenous fiber substrate in a covalent bond connection mode, and the covalent organic framework material is formed by light elements through covalent bonds; and the silane coupling agent interface layer is in covalent bond connection with hydroxyl / carboxyl of the collagenous fiber and an end group functional group of the covalent organic framework material to form an organic-organic covalent bridging structure. According to the invention, the silane coupling agent forms Si-O-C or Si-N-C covalent bonds with hydroxyl / carboxyl of the collagenous fibers and terminal functional groups of COF respectively, so that a'collagenous fiber-silane-COF 'organic-organic covalent bridging structure is constructed, and interface defects caused by physical mixing are thoroughly eliminated; and the structural integrity and long-term stability of the composite membrane in the gas separation process are ensured.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to collagen fiber-covalent organic framework composite membranes and their preparation methods. Background Technology

[0002] With the widespread application of membrane separation technology in gas separation, water treatment and other fields, the development of novel membrane materials with high selectivity, high throughput and high stability has become a research hotspot. Currently, metal-organic frameworks (MOFs) have attracted attention as porous fillers for mixed matrix membranes, but their application in practical applications suffers from problems such as framework collapse due to metal node hydrolysis and metal ion leaching, which limit their application in humid gas environments.

[0003] Covalent organic frameworks (COFs) are crystalline porous materials formed by organic building blocks linked by covalent bonds, possessing characteristics such as high chemical stability and tunable structure. However, when COFs are composited with membrane substrates, achieving a robust interfacial bond between COFs and the substrate while maintaining the flexibility and permeability of the composite membrane remains a pressing technical challenge.

[0004] In existing technologies, collagen fibers are mainly used in traditional leather products or liquid phase separation membranes, and there are no reports of using them as a substrate to composite with COFs for gas separation membranes. Therefore, there is a need to develop a new method for preparing composite membranes to expand the application of COFs and collagen fibers in the field of membrane separation.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] To address the above issues, this invention provides a collagen fiber-covalent organic framework composite membrane and its preparation method. It utilizes abundant, low-cost, and biodegradable collagen fibers as a three-dimensional porous framework, firmly anchoring high-performance COFs onto the fiber network through effective interface engineering techniques. This results in a novel collagen fiber-COF composite membrane with superior performance. This not only opens up new avenues for the high-value utilization of waste collagen resources but also provides a novel solution to overcome the performance bottlenecks of traditional hybrid matrix membranes.

[0007] Compared with the prior art, the present invention has the following beneficial effects: This invention is the first to apply silane coupling agents to a pure organic-organic hybrid system. By forming Si-OC or Si-NC covalent bonds with the hydroxyl / carboxyl groups of collagen fibers and the terminal functional groups of COF, respectively, a "collagen fiber-silane-COF" organic-organic covalently bridged structure is constructed. This is fundamentally different from the existing technology where MOFs and substrates rely on coordination bonds (metal-oxygen / nitrogen bonds) or physical adsorption: covalent bonds have higher bond energy and stability, and are less susceptible to breakage due to humidity and pH. Simultaneously, the compatibility of the organic-organic interface is superior to that of the inorganic-organic interface, and the entropy increase effect promotes the stability of the interface layer. This bidirectional chemical bonding completely eliminates interface defects caused by physical mixing, ensuring the structural integrity and long-term stability of the composite membrane during gas separation.

[0008] Because COF is entirely composed of covalent bonds and has no metal nodes, the composite membrane of this invention fundamentally avoids the problems of metal node hydrolysis and metal ion leaching that easily occur in existing MOF-based membranes in humid gas environments. Simultaneously, the organic-organic covalent bridging layer is insensitive to water molecules and will not fail due to hydrolysis. Therefore, the composite membrane of this invention can operate stably for a long time in humid gas environments (such as flue gas, biogas, and humid natural gas) with a relative humidity of not less than 80%, maintaining high gas separation selectivity and permeation flux, which is difficult to achieve with existing MOF-collagen fiber composite membranes (relying on coordination bonds).

[0009] The two-dimensional COFs used in this invention (such as COF-5, TpPa-1, etc.) possess intrinsic flexibility (interlayer slippage, in-plane bending, modulus of approximately 1-5 GPa), forming a flexible gradient interface with the flexible collagen fiber substrate (modulus ~100 MPa), resulting in a smoother modulus transition. This "flexible-flexible" matching avoids the mechanical mismatch problem between rigid MOFs and flexible collagen fibers. During the variable pressure cycle of gas separation or the winding of membrane modules, the interface is less prone to shear cracks or peeling, ensuring the mechanical flexibility and durability of the composite membrane.

[0010] This invention employs a "wetting-filtration-in-situ coupling" preparation strategy. The entire process is completed under mild conditions ranging from room temperature to 120°C, eliminating the need for the high-temperature solvothermal conditions (typically >120°C organic solvent systems) required for MOF preparation. This not only avoids the damage to the triple helix structure of collagen fibers caused by high temperatures, preserving their natural porous network and flexibility, but also offers simple operation, mild conditions, and ease of large-scale production. Vacuum filtration achieves a uniform and dense arrangement of COFs on the collagen fiber surface, while in-situ silane coupling is completed instantly under moist conditions, eliminating the need for drying and subsequent processing, thus simplifying the process. Attached Figure Description

[0011] Figure 1CFM-TpPa-1 composite membrane prepared in Example 5: (a) appearance of the membrane; (b) SEM image of the membrane surface; Figure 2 CFM-TpPa-1 composite membrane prepared in Comparative Example 1: (a) appearance of the membrane; (b) SEM image of the membrane surface; Figure 3 Comparative Example 2: CFM-UiO-66-NH2 composite membrane: (a) appearance of the membrane; (b) SEM image of the membrane surface. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of protection of this invention. Any modifications or substitutions made to the methods, steps, or conditions of this invention without departing from the spirit and substance of this invention shall fall within the scope of protection of this invention.

[0013] The first embodiment of the present invention provides a collagen fiber-covalent organic framework composite membrane, comprising: Collagen fiber substrate with a three-dimensional network porous structure; A covalent organic framework material is loaded onto the surface and pore walls of the collagen fiber substrate via covalent bonds. The covalent organic framework material is composed of lightweight elements connected by covalent bonds. The silane coupling agent interface layer forms covalent bonds with the hydroxyl / carboxyl groups of collagen fibers and the end functional groups of the covalent organic framework material, respectively, to form an organic-organic covalent bridge structure.

[0014] The collagen fiber-covalent organic framework composite membrane provided in this invention is an organic-organic hybrid composite membrane constructed using natural collagen fibers as a three-dimensional porous framework, covalent organic framework (COF) materials as functional separation layers, and specific interface engineering techniques. The key method lies in introducing a silane coupling agent as a molecular adhesive to chemically bond the collagen fiber substrate to the COF functional material, thus constructing a "collagen fiber-silane-COF" organic-organic covalent bridging structure.

[0015] The silane coupling agent interface layer achieves a strong connection between collagen fibers and COF through bidirectional chemical bonding: (1) Bonding with collagen fibers: Collagen molecular chains are rich in hydroxyl groups (-OH, derived from hydroxyproline, serine, etc.) and carboxyl groups (-COOH, derived from aspartic acid, glutamic acid, etc.). The silanol group generated by the hydrolysis of the silane coupling agent (general formula YR-Si(OR')3) undergoes a dehydration condensation reaction with the -OH or -COOH on the surface of collagen fibers to form a stable Si-OC covalent bond (-Si-O-Collagen); (2) Bonding with COF: The silanol group can form a covalent bond with the defect sites on the surface of COF crystals (such as uncoordinated functional groups, suspended organic ligand functional groups, surface hydroxyl groups, etc.); at the same time, the organic functional groups (Y) of the silane coupling agent, such as amino (-NH2), epoxy group, etc., can react with specific sites of COF (such as aldehyde group, hydroxyl group) to form Si-NC or Si-OC covalent bonds.

[0016] Through this bidirectional chemical bonding, the silane coupling agent establishes a robust covalent bridge between the collagen fibers and the COF, completely eliminating interfacial defects caused by physical mixing and ensuring the structural integrity and long-term stability of the composite membrane. This organic-organic covalent bridge structure is insensitive to water molecules and is not easily broken by humidity or pH, which is a fundamental difference from the coordination bonding between MOF and the substrate.

[0017] In some preferred embodiments, the amount of silane coupling agent is 0.5 to 10 parts by weight, based on 100 parts by weight of collagen fiber substrate. Too little dosage will result in insufficient interfacial bonding, while too much dosage may lead to silane self-polymerization or blockage of pores.

[0018] The silane coupling agent can be selected from aminosilanes, epoxysilanes, or vinylsilane coupling agents. Specifically, it can be selected from: γ-aminopropyltriethoxysilane (KH-550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602), bisaminosilane coupling agent OFS-6020, γ-glycidyl etheroxypropyltrimethoxysilane (KH-560), 3-glycidyl etheroxypropyltriethoxysilane (KH-561), or vinyltriethoxysilane (A-151). These silane coupling agents have the general formula YR-Si(OR')3, wherein the alkoxy group (-OR') can be hydrolyzed in an aqueous environment to generate a highly reactive silanol group (-Si-OH).

[0019] The resulting product is a flexible composite membrane with a multi-scale pore structure. The multi-level pores (ranging from micrometers to tens of micrometers) of the collagen fiber substrate provide low-resistance, rapid transport channels for fluids (gas or liquids), significantly improving the membrane's apparent permeation flux. The COF material anchored to the fiber surface utilizes its precise and uniform sub-nanometer micropores for accurate sieving. This composite membrane maintains the flexibility of natural collagen fibers while exhibiting excellent structural stability and gas separation performance, making it particularly suitable for gas separation processes in high-humidity environments.

[0020] The collagen fiber substrate used in this invention can be obtained by using acid-soaked raw hides as raw materials, tanning them to obtain leather blanks, and then squeezing out the water and splitting the hides to obtain a membrane material with a stable three-dimensional porous network structure.

[0021] The tanning method can employ conventional tanning processes in the art, including but not limited to inorganic tanning methods such as chrome tanning, aluminum tanning, titanium tanning, and zirconium tanning, or organic tanning methods such as aldehyde tanning and vegetable tanning, or a combination of multiple methods. The purpose of tanning is to stabilize the collagen fiber structure, improve its heat resistance and corrosion resistance, and give the resulting basement membrane a shrinkage temperature of 65~120℃.

[0022] The leather slicing process uses a slicing machine to slice the leather blank to a specified thickness, resulting in a collagen fiber substrate membrane with a thickness of 0.2–1.2 mm. This thickness range is set based on the following considerations: if the thickness is too small (<0.2 mm), the mechanical strength is insufficient to support the COF functional layer; if the thickness is too large (>1.2 mm), the mass transfer resistance increases significantly, hindering gas permeation. The collagen fiber substrate has a multi-level, three-dimensional network porous structure ranging from nanometers to micrometers. This structure provides a low-resistance, rapid transport channel for fluids (gas or liquid), greatly improving the membrane's apparent permeation flux.

[0023] The covalent organic framework (COF) material used in this invention is a crystalline porous material formed by organic building units connected by covalent bonds. Unlike metal-organic frameworks (MOF), COF is composed entirely of lightweight elements (such as C, H, O, N, B, etc.) connected by covalent bonds (such as CN, CO, BO, etc.) and does not contain metal nodes.

[0024] The COF material can be selected from covalent organic framework materials based on imine bonds, borate ester bonds, or triazine rings. Specifically, TpPa-1 (based on imine bonds), COF-300 (based on imine bonds), COF-5 (based on borate ester bonds), or TAPB-DMTP-COF (based on imine bonds) can be selected. These COF materials have extremely high specific surface area, permanent pore structure, and precisely controllable pore size, enabling precise sieving or specific adsorption in the composite membrane, and forming a multi-scale pore synergistic system with the rapid transport channels of the collagen fiber substrate.

[0025] Based on 100 parts by weight of the collagen fiber substrate, the amount of the covalent organic framework material is 0.001 to 1 part by weight. If the amount of covalent organic framework material is too low, the separation selectivity will be insufficient; if the amount is too high, it may cause pore blockage and affect the permeation flux.

[0026] The second embodiment of the present invention provides a method for preparing a collagen fiber-covalent organic framework composite membrane, comprising the following steps: The covalent organic framework material was dispersed in a mixed solvent of ethanol and water to obtain a dispersion. The collagen fiber substrate was immersed in the dispersion, and the solvent was removed by vacuum filtration. Without a drying step, the silane coupling agent is added immediately while the mixture is still moist, and the mixture is cured after reacting at room temperature.

[0027] The preparation method of this invention adopts a mild preparation strategy of "immersion-filtration-in-situ coupling", and achieves the synergistic effect of physical anchoring and chemical bonding through time sequence control.

[0028] Specifically, firstly, the COF dispersion is uniformly compacted into the collagen fiber network using the hydrodynamic action of vacuum filtration to form a physical anchor. Then, in a moist state without drying, a silane coupling agent is immediately added to carry out an in-situ reaction. The residual solvent promotes the hydrolysis and uniform diffusion of silane, allowing the silane coupling agent to undergo a condensation reaction with both collagen fibers and COF to form a covalent bridging layer. Finally, the crosslinking of COF and the collagen fiber basement membrane is completed by curing at medium to low temperatures (50~120 ℃).

[0029] This method avoids the high-temperature solvothermal conditions required for MOF preparation, achieving robust chemical anchoring of COF on flexible bio-substrates while maintaining the integrity of the natural triple helix structure and porous network of collagen fibers. The entire process is simple to operate, operates under mild conditions, is easy to scale up, and requires no drying or reprocessing, thus simplifying the process flow.

[0030] In some preferred embodiments, 0.001 to 1 part by weight (based on 100 parts by weight of collagen fiber substrate) of COF material is dispersed in 5 to 500 parts by weight of solvent system, and a uniform and stable dispersion is obtained by ultrasonic treatment (power 100 to 500 W, time 10 to 60 min) or high-speed stirring (speed 500 to 2000 rpm, time 30 to 120 min).

[0031] In some preferred embodiments, the solvent system is a mixture of anhydrous ethanol and deionized water, with a volume ratio of 1:10 to 10:1. This ratio range is selected based on the hydrophilicity / hydrophobicity of the COF material: for COFs with strong hydrophilicity (such as those containing a large number of hydroxyl groups), the water ratio can be appropriately increased (e.g., 1:10); for COFs with strong hydrophobicity, the ethanol ratio can be appropriately increased (e.g., 10:1). The choice of solvent must ensure that the COF maintains a stable crystal structure while also facilitating the subsequent hydrolysis reaction of the silane coupling agent.

[0032] In some preferred embodiments, the wetting time is controlled within 30 to 240 minutes. This time range ensures that the dispersion can fully penetrate into the pores inside the collagen fiber substrate, achieving a uniform distribution of COF in the three-dimensional network. Too short a wetting time results in insufficient penetration, while too long a time reduces efficiency.

[0033] The vacuum filtration not only removes solvent quickly, but also uses fluid dynamics to uniformly and densely compact and fix COF particles on the surface and pore walls of the collagen fiber network, forming a preliminary physical anchoring structure. This avoids the agglomeration problem in traditional blending methods and achieves efficient and orderly arrangement of functional fillers.

[0034] In this embodiment of the invention, after vacuum filtration, the silane coupling agent solution is added directly to the composite membrane in a moist state without a drying step. Conventional processes typically involve drying after filtration, but this invention discovers that adding the silane coupling agent immediately in a moist state with residual solvent can utilize the residual solvent to promote the hydrolysis and uniform diffusion of silane, while simultaneously preventing the aggregation or detachment of COF particles during the drying process.

[0035] In some preferred embodiments, the silane coupling agent solution is typically in ethanol / water as a solvent, with a mass concentration of 1% to 10%. The impregnation reaction is carried out at room temperature (20 to 30 °C) for 0.5 to 4 hours. The choice of room temperature is to avoid damage to the collagen fiber structure caused by high temperature, while ensuring that the silane coupling agent has sufficient time to fully contact and react with the collagen fibers and COF.

[0036] In some preferred embodiments, the curing is carried out at 50~120 °C for 0.5~6 h.

[0037] In some preferred embodiments, based on 100 parts by weight of collagen fiber substrate, the covalent organic framework material comprises 0.001 to 1 part by weight, preferably 0.01 to 0.5 parts by weight; the solvent system comprises 5 to 500 parts by weight, preferably 50 to 200 parts by weight; and the silane coupling agent comprises 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight. These proportions ensure appropriate loading of the COF onto the collagen fiber substrate and that the silane coupling agent adequately modifies the interface without clogging the pores.

[0038] The preparation and properties of collagen fiber-covalent organic framework composite membranes are described in detail below through several specific examples.

[0039] Example 1 (1) Preparation of collagen fiber basement membrane: using acid-treated cowhide as raw material, glutaraldehyde tanning was carried out using conventional glutaraldehyde process to obtain glutaraldehyde tanned leather with a shrinkage temperature of 85 ℃; after squeezing out water, its thickness was adjusted to 0.6±0.05 mm to obtain a flexible and porous collagen fiber basement membrane, denoted as CFM; (2) Preparation of organic framework material dispersion: 0.005 parts of TpPa-1 nanocrystals were uniformly mixed and dispersed with 50 parts of anhydrous ethanol / deionized water mixed solvent with a volume ratio of 1:10. (3) Composite and interface modification: Take 100 parts of CFM, immerse it in the above TpPa-1 dispersion, let it stand at room temperature for 60 min, and then perform vacuum filtration until there is no obvious liquid dripping; use 50 mL of ethanol solution containing 0.5 parts of diaminosilane coupling agent (OFS-6020) to fully and uniformly wet the entire membrane and keep it moist at room temperature for 1 h; (4) Cross-linking and curing: The impregnated composite film is heated and cured at 95 °C for 1.5 h; after cooling, a high-strength CFM-TpPa-1 composite film is obtained.

[0040] Example 2 (1) Preparation of collagen fiber basement membrane: using acid-treated sheepskin as raw material, biomass-derived aldehyde tanning process was adopted to obtain biomass-derived aldehyde tanned leather with a shrinkage temperature of 80 ℃; after squeezing out water, its thickness was adjusted to 0.2±0.05 mm to obtain a flexible and porous collagen fiber basement membrane, denoted as CFM. (2) Preparation of organic framework material dispersion: 0.2 parts of COF-300 nanocrystals were uniformly mixed and dispersed with 200 parts of anhydrous ethanol / deionized water mixed solvent with a volume ratio of 9:2; (3) Composite and interface modification: Take 100 parts of CFM, immerse it in the above COF-300 dispersion, let it stand at room temperature for 150 min, and then perform vacuum filtration until there is no obvious liquid dripping; use 50 mL of ethanol solution containing 3 parts of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602) to fully and uniformly wet the entire membrane and keep it moist at room temperature for 2.5 h; (4) Cross-linking and curing: The impregnated composite film is heated and cured at 70 °C for 4 h; after cooling, a high-strength CFM-COF-300 composite film is obtained.

[0041] Example 3 (1) Preparation of collagen fiber basement membrane: using acid-treated cowhide as raw material, aluminum-tanned leather was prepared by conventional aluminum-tanning process with a shrinkage temperature of 115 ℃; after squeezing out water, its thickness was adjusted to 1.2±0.05 mm to obtain a flexible and porous collagen fiber basement membrane, denoted as CFM. (2) Preparation of organic framework material dispersion: 0.6 parts of TAPB-DMTP-COF nanocrystals were uniformly mixed and dispersed with 300 parts of anhydrous ethanol / deionized water mixed solvent with a volume ratio of 5:6. (3) Composite and interface modification: Take 100 parts of CFM and immerse it in the above TAPB-DMTP-COF dispersion. Let it stand at room temperature for 210 min and then vacuum filter until there is no obvious liquid dripping. Use 50 mL of ethanol solution containing 4 parts of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602) to fully and uniformly wet the entire membrane and keep it moist at room temperature for 2 h. (4) Crosslinking and curing: Take out the impregnated composite film and heat it at 110 °C for 2 h; after cooling, a high-strength CFM-TAPB-DMTP-COF composite film is obtained.

[0042] Example 4 (1) Preparation of collagen fiber basement membrane: using acid-treated cowhide as raw material, chrome tanning process was adopted to obtain chrome tanned leather with a shrinkage temperature of 110 ℃; after squeezing out water, its thickness was adjusted to 1.0±0.05 mm to obtain a flexible and porous collagen fiber basement membrane, denoted as CFM; (2) Preparation of organic framework material dispersion: 0.4 parts of COF-5 nanocrystals were uniformly mixed and dispersed with 200 parts of anhydrous ethanol / deionized water mixed solvent with a volume ratio of 9:2; (3) Composite and interface modification: Take 100 parts of CFM, immerse it in the above COF-5 dispersion, let it stand at room temperature for 120 min, and then perform vacuum filtration until there is no obvious liquid dripping; use 50 mL of ethanol solution containing 1 part of vinyltriethoxysilane (A-151) to fully and uniformly wet the entire membrane and keep it moist at room temperature for 2 h. (4) Cross-linking and curing: The impregnated composite film is heated in a forced-air oven at 110 °C for 1 h; after cooling, a high-strength CFM-COF-5 composite film is obtained.

[0043] Example 5 (1) Preparation of collagen fiber basement membrane: using acid-treated cowhide as raw material, chrome tanning process was adopted to obtain chrome tanned leather with a shrinkage temperature of 115 ℃; after squeezing out water, its thickness was adjusted to 0.2±0.05 mm to obtain a flexible and porous collagen fiber basement membrane, denoted as CFM; (2) Preparation of organic framework material dispersion: 0.2 parts of TpPa-1 nanocrystals were mixed with 20 parts of anhydrous ethanol / deionized water mixed solvent with a volume ratio of 10:1 and dispersed evenly. (3) Composite and interface modification: Take 100 parts of CFM, immerse it in the above TpPa-1 dispersion, let it stand at room temperature for 120 min, and then perform vacuum filtration until there is no obvious liquid dripping; use 50 mL of ethanol solution containing 2 parts of γ-aminopropyltriethoxysilane (KH-550) to fully and uniformly wet the entire membrane and keep it moist at room temperature for 1 h; (4) Crosslinking and curing: Take out the impregnated composite film, lay it flat on a polytetrafluoroethylene plate, and heat it in a 120 ℃ oven for 0.5 h; after cooling, a high-strength CFM-TpPa-1 composite film is obtained.

[0044] The surface of the high-strength CFM-TpPa-1 composite film prepared in this example was treated by a scraping method. No obvious TpPa-1 nanoparticles were observed to be scraped off the CFM, confirming that the silane coupling agent successfully chemically bonded CFM and TpPa-1 together. Figure 1 a).

[0045] Scanning electron microscopy (SEM) revealed that TpPa-1 nanoparticles were uniformly and densely coated on the surface of collagen fibers, with no obvious aggregation observed. Figure 1 b).

[0046] Comparative Example 1 The only difference from Example 5 is that no silane coupling agent is added in step (3). Testing showed that TpPa-1 was difficult to bind firmly to the surface of the collagen fiber basement membrane. Figure 2 a), and the TpPa-1 nanoparticles are unevenly distributed among the fibers, exhibiting aggregation ( Figure 2 b).

[0047] Comparative Example 2 The only difference from Example 5 is that the organic framework used is the MOF material UiO-66-NH2. Testing and observation showed that UiO-66-NH2 can firmly bind to the surface of the collagen fiber basement membrane. Figure 3 a) The distribution among fibers is relatively uniform overall, but it is insufficient in filling large voids and defects. Figure 3 b).

[0048] The performance of the collagen fiber-organic framework composite membranes prepared in Example 5 and Comparative Examples 1-2 was tested: tensile strength and elongation at break were tested using a servo-controlled computer system tensile testing machine (AI7000-S, High-speed Rail Testing Instruments (Dongguan) Co., Ltd.); the fixation firmness of the organic framework material was observed using the scratch photography method; the CO2 / N2 separation efficiency at 80% RH was tested using a multi-component competitive adsorption analyzer (BSD-MAB&M, Bestar Instruments) (conditions: 30.0 ℃, 0.1 MPa). The test results are shown in Table 1.

[0049] Table 1. Performance comparison of collagen fiber-organic framework composite membranes obtained from different embodiments. .

[0050] The above embodiments are merely specific application examples of the present invention. Those skilled in the art can make reasonable adjustments and changes to the selection of raw materials (different tanning methods, different types of MOFs / COFs) and process parameters (concentration, time, temperature, etc.) based on the core ideas of the present invention, and these should not depart from the scope of protection claimed by the present invention.

Claims

1. A collagen fiber-covalent organic framework composite membrane, characterized in that, include: Collagen fiber substrate with a three-dimensional network porous structure; A covalent organic framework material is loaded onto the surface and pore walls of the collagen fiber substrate via covalent bonds. The covalent organic framework material is composed of lightweight elements connected by covalent bonds. The silane coupling agent interface layer forms covalent bonds with the hydroxyl / carboxyl groups of collagen fibers and the end functional groups of the covalent organic framework material, respectively, to form an organic-organic covalent bridge structure.

2. The collagen fiber-covalent organic framework composite membrane as described in claim 1, characterized in that, The thickness of the collagen fiber substrate is 0.2~1.2 mm, and based on 100 parts by weight of the collagen fiber substrate, the amount of the covalent organic framework material is 0.001~1 parts by weight.

3. The collagen fiber-covalent organic framework composite membrane as described in claim 1, characterized in that, The covalent organic framework material is at least one of the covalent organic framework materials constructed based on imine bonds, borate ester bonds, or triazine rings.

4. The collagen fiber-covalent organic framework composite membrane as described in claim 3, characterized in that, The covalent organic framework is selected from, but is not limited to, TpPa-1, COF-300, COF-5, or TAPB-DMTP-COF.

5. The collagen fiber-covalent organic framework composite membrane as described in claim 1, characterized in that, The silane coupling agent is an aminosilane, epoxysilane, or vinylsilane coupling agent, preferably γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, bisaminosilane coupling agent OFS-6020, γ-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, or vinyltriethoxysilane.

6. The collagen fiber-covalent organic framework composite membrane as described in claim 1 or 5, characterized in that, The silane coupling agent is connected to the covalent organic framework material via Si-NC or Si-OC covalent bonds, and to the collagen fibers via Si-OC covalent bonds.

7. The method for preparing the collagen fiber-covalent organic framework composite membrane according to any one of claims 1-6, characterized in that, Includes the following steps: The covalent organic framework material was dispersed in a mixed solvent of ethanol and water to obtain a dispersion. The collagen fiber substrate was immersed in the dispersion, and the solvent was removed by vacuum filtration. Without a drying step, the silane coupling agent is added immediately while the mixture is still moist, and the mixture is cured after reacting at room temperature.

8. The preparation method according to claim 7, characterized in that, Based on 100 parts by weight of the collagen fiber substrate, the amount of the covalent organic framework material is 0.001 to 1 part by weight, the amount of the mixed solvent of ethanol and water is 5 to 500 parts by weight, and the amount of the silane coupling agent is 0.5 to 10 parts by weight.

9. The preparation method according to claim 7 or 8, characterized in that, In the ethanol-water mixture, the volume ratio of ethanol to water is 1:10 to 10:

1.

10. The preparation method according to claim 7, characterized in that, The impregnation time is 30~240 min, the room temperature reaction time is 0.5~4 h, the curing time is 0.5~6 h, and the temperature is 50~120 ℃.

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