An electrochromic covalent organic framework fiber membrane and its preparation method

Abstract

This invention provides an electrochromic covalent organic framework fiber membrane and its preparation method, belonging to the field of fiber material technology. The preparation method includes the following steps: dissolving polyvinylidene fluoride, a polyamine compound, and polyethylene glycol in a mixed solvent to obtain a spinning solution; then electrospinning the spinning solution to obtain a precursor fiber membrane; and finally, performing an in-situ thermal synthesis reaction of the precursor fiber membrane in a solution containing a polyaldehyde compound and a catalyst to obtain the electrochromic covalent organic framework fiber membrane. The preparation method provided by this invention can obtain a covalent organic framework electrochromic fiber membrane material with a gradient porous structure throughout. It possesses micron-level pores formed by fiber entanglement, submicron-level pores in porous fibers, and intrinsic mesopores of the covalent organic framework. This gradient pore structure facilitates the simultaneous optimization of the electrolyte's permeation concentration and rate in the electrochromic material, allowing the electrolyte to fully contact the redox units of the material and improving the electrochromic performance.

Description

Technical Field

[0001] This invention relates to the field of fiber materials technology, and in particular to an electrochromic covalent organic framework fiber membrane and its preparation method. Background Technology

[0002] With the continuous development of high-tech reconnaissance systems, the visibility of weapons and individual soldiers on the battlefield has greatly increased, seriously threatening soldiers and national security. Flexible electrochromic materials are a type of material that urgently needs vigorous development in the fields of stealth, concealment, and deception, and have great application prospects in the military security field. However, current flexible electrochromic materials are mainly linear conductive polymers (such as polyaniline and polypyrrole), which have advantages such as rich color changes and short response time. However, due to the strong intermolecular forces and tight entanglement of linear conductive polymer molecular chains, it is not conducive to the penetration and ion intercalation / deintercalation process of electrolytes in practical applications, affecting the transport efficiency of charge carriers and electrolyte ions, thus limiting the application of their electrochromic properties.

[0003] Covalent organic frameworks (COFs) are a class of porous powder materials with low density, large specific surface area, and tunable size and structure. The porosity, high crystallinity, π-electron conjugation system, and ordered π-π stacking of COFs effectively promote electron conduction and ion transport. Furthermore, by screening redox-resistant multifunctional compounds as building blocks, COFs can be endowed with electrochromic properties. Due to the unique porous structure and abundant redox units of COFs, novel electrochromic materials prepared using COFs can effectively improve electron and ion transport efficiency, resulting in advantages over traditional linear polymer-based electrochromic materials, such as shorter color-changing time, higher coloring efficiency, and higher optical contrast. However, the intrinsic nanopore (<5nm) structure of COFs leads to high resistance to the insertion and extraction of electrolyte ions, which to some extent limits further improvement in their electrochromic performance. Summary of the Invention

[0004] In view of this, the present invention aims to provide an electrochromic covalent organic framework fiber membrane and its preparation method. The preparation method provided by the present invention can obtain a covalent organic framework electrochromic fiber membrane material with a gradient porous structure throughout. It has micron-sized pores formed by fiber entanglement, submicron pores of porous fibers, and intrinsic mesopores of the covalent organic framework. Such a gradient pore structure is beneficial to simultaneously optimizing the permeation concentration and rate of electrolyte in the electrochromic material, so as to enable the electrolyte to fully contact the redox unit of the material and improve the electrochromic performance.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One of the technical solutions of this invention is a method for preparing an electrochromic covalent organic framework fiber membrane, comprising the following steps:

[0007] Polyvinylidene fluoride, polyamine compounds and polyethylene glycol are dissolved in a mixed solvent to obtain a spinning solution, which is then electrospun to obtain a precursor fiber membrane.

[0008] The precursor fiber membrane was subjected to in-situ thermal synthesis in a solution containing polyaldehyde compounds and a catalyst to obtain an electrochromic covalent organic framework fiber membrane.

[0009] The second technical solution of the present invention is an electrochromic covalent organic framework fiber membrane prepared by the above preparation method.

[0010] The present invention discloses the following technical effects:

[0011] This invention provides a method for preparing electrochromic covalent organic framework fiber membranes. The material prepared by this method not only has the characteristics of large specific surface area, stable structure, π-electron conjugation system, and multiple reaction sites of covalent organic frameworks, but also has a multi-level pore structure of micron-pores / submicron-pores / micro-mesoporosis, which allows the electrolyte to come into rapid and sufficient contact with the reaction units in the electrochromic COFs, effectively improving the electrochromic performance of the material.

[0012] The electrochromic covalent organic framework fiber membrane provided by this invention is a fiber-based electrochromic material that can be better applied to military camouflage and stealth clothing while maintaining excellent flexibility, breathability and macroscopic continuity. Attached Figure Description

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 The nitrogen adsorption-desorption isotherm and specific surface area diagram of the electrochromic covalent organic framework fiber membrane in Example 1 are shown.

[0015] Figure 2 This is a pore size distribution diagram of the electrochromic covalent organic framework fiber membrane in Example 1;

[0016] Figure 3 This is a scanning electron microscope (SEM) image of the electrochromic covalent organic framework fiber membrane in Example 1.

[0017] Figure 4 This is a cyclic voltammetry curve of the electrochromic covalent organic framework fiber membrane in Example 1;

[0018] Figure 5This is a color-changing optical photograph of the electrochromic covalent organic framework fiber membrane in Example 1. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0020] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0022] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0023] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0024] This invention provides a method for preparing an electrochromic covalent organic framework fiber membrane, comprising the following steps:

[0025] Polyvinylidene fluoride, polyamine compounds and polyethylene glycol are dissolved in a mixed solvent to obtain a spinning solution. The spinning solution is then electrospun to obtain a porous electrochromic covalent organic framework precursor fiber membrane (denoted as precursor fiber membrane).

[0026] The precursor fiber membrane was subjected to in-situ thermal synthesis in a solution containing polyaldehyde compounds and a catalyst to obtain an electrochromic covalent organic framework fiber membrane.

[0027] In some embodiments of the present invention, the molecular weight of the polyvinylidene fluoride is 400,000 to 900,000; and the molecular weight of the polyethylene glycol is 2,000 to 2,000,000.

[0028] The reason for selecting the molecular weights of polyvinylidene fluoride (PVDF) and polyethylene glycol (PEG) within the above-mentioned parameter range in this invention is as follows: the molecular weight of PVDF affects the fiber morphology and properties of electrospinning. If it is not within this range, it will lead to poor fiber uniformity and problems such as beading. The molecular weight of PEG affects the size and density of pores on the fiber and also affects the viscosity of the spinning solution. If it is not within this range, it will lead to failure of fiber pore formation.

[0029] In some embodiments of the present invention, the concentration of polyvinylidene fluoride in the spinning solution is 4-15 wt%.

[0030] In some embodiments of the present invention, the polyamine compound is at least one selected from tris(4-aminophenyl)amine, 1,3,6,8-tetra-(p-aminophenyl)pyrene, and 1,3,5-tris(4-aminophenyl)benzene; the mass ratio of polyvinylidene fluoride, the polyamine compound, and polyethylene glycol is 1:(0.1-1):(0.01-0.1).

[0031] In this invention, if the mass ratio of polyvinylidene fluoride, polyamine compounds, and polyethylene glycol is not within the above range, it will result in: (1) the inability to form a fiber morphology with a uniform diameter after electrospinning; and (2) insufficient phase separation of the spinning solution during jetting, resulting in non-porous fibers. Both of these situations will affect the microstructure of the final electrochromic covalent organic framework fiber membrane, thereby affecting its electrochromic properties.

[0032] In some embodiments of the present invention, the mixed solvent is a mixture of N,N-dimethylformamide and water in a volume ratio of 1:(0 to 0.1).

[0033] In this invention, if the volume ratio of N,N-dimethylformamide to water is not within the above range, it will affect the pore size of the precursor fiber membrane, causing it to deviate from the optimal pore size and affecting the transport rate of electrolyte ions.

[0034] In some embodiments of the present invention, the parameters of the electrospinning are: voltage 15-30kV, liquid supply rate 0.2-5.0mL / min, receiving distance 10-40cm, roller speed 30-80r / min, spinning temperature 20-28℃, spinning humidity 50-80%, and the material for receiving the fiber membrane is tin foil, aluminum foil, or conductive carbon cloth.

[0035] In this invention, if the electrospinning parameters are not within the above range, the spinning solution will not be able to break through the surface tension of the spinning solution under the action of charge, and will not be able to form Taylor cones and continuously spray out filaments, so that the material cannot form a nanofiber morphology with uniform diameter; or reasonable moisture-induced phase separation cannot occur, so that the fibers obtained by electrospinning do not have a suitable porous structure.

[0036] In some embodiments of the present invention, the polyaldehyde compound is at least one selected from thieno[3,2-b]thieno-2,5-dicarboxaldehyde, benzo[C][1,2,5]thiadiazole-4,7-dicarboxaldehyde, 2,6-naphthiadicarboxaldehyde, tris(4-formylphenyl)amine, and trialdehyde-resorcinol; the concentration of the polyaldehyde compound in the solution is 1.0 to 5.0 mM.

[0037] In some embodiments of the present invention, the catalyst is formic acid, acetic acid or toluenesulfonic acid; the concentration of the catalyst in the solution is 20-40 mM.

[0038] In some embodiments of the present invention, the solvent used to dissolve the polyaldehyde compound and the catalyst is at least one selected from methanol, ethanol, 1,4-dioxane, mesitylene, benzyl alcohol, and chloroform.

[0039] In some embodiments of the present invention, the reaction temperature of the in-situ thermal synthesis reaction is 25–120°C, and the reaction time is 3–72 h.

[0040] In some embodiments of the present invention, after the in-situ thermal synthesis reaction is completed, the process further includes washing and drying steps; the solvent used for washing is at least one of methanol, ethanol, 1,4-dioxane, mesitylene, benzyl alcohol, chloroform, and water; the drying temperature is 80°C and the time is 12 hours.

[0041] The present invention also provides an electrochromic covalent organic framework fiber membrane prepared by the preparation method described in the above technical solution.

[0042] The electrochromic covalent organic framework fiber membrane provided by this invention possesses a gradient porous structure with micron-sized pores, submicron-sized pores, and mesopores. This gradient porous structure facilitates the simultaneous optimization of the electrolyte's permeation concentration and rate within the electrochromic material, ensuring sufficient contact between the electrolyte and the material's redox units and enhancing electrochromic performance. Compared to electrochromic films prepared using existing technologies, the material of this invention exhibits higher specific surface area, larger gradient porosity, structural stability, more reaction sites, and higher ion insertion / extraction efficiency, achieving superior electrochromic performance.

[0043] The mechanism of this invention is as follows:

[0044] The electrochromic covalent organic framework fiber membrane provided by this invention possesses a volumetric gradient porosity, which requires meeting two conditions: first, the stable and uniform preparation of the volumetric porous electrochromic covalent organic framework precursor fiber membrane. This is achieved by adding polyethylene glycol of a certain molecular weight and water to induce controllable phase separation during charged jetting and stretching orientation processes in the electrospinning solution, resulting in a precursor fiber membrane with a volumetric submicron porous structure. The fiber has an average diameter of 1.8 μm, an average surface pore size of 350 ± 200 nm, and a surface pore density of 9 ± 3 pores / μm. 2 The chemical composition of the spinning solution determines the critical conditions for phase separation in the system. The morphology of the final fiber is highly dependent on the electrospinning parameters, and the porous morphology of the fiber significantly affects the electrochromic properties of the final material. Secondly, sufficient and uniform in-situ synthesis of electrochromic covalent organic frameworks on a porous precursor fiber membrane is crucial. This requires that the polyamine compounds in the precursor fiber and the polyaldehyde compounds in the solution have a considerable diffusion rate within the reaction system to synthesize sufficient electrochromic covalent organic frameworks in-situ within the submicron porous precursor fiber. Non-ideal solvent systems will result in covalent organic framework particles being synthesized in the reaction solution, physically adhering to the fiber surface, or insufficient covalent organic framework films adhering to the fiber surface. Both of these situations will affect the electrochromic properties of the final fiber membrane.

[0045] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0046] Unless otherwise specified, all raw materials and reagents used in the examples can be obtained through commercial channels.

[0047] Example 1

[0048] This embodiment provides an electrochromic covalent organic framework fiber membrane, and the preparation method steps are as follows:

[0049] Step 1: Polyvinylidene fluoride (molecular weight: 400,000, 1.2 g), polyethylene glycol (molecular weight: 2,000,000, 0.08 g), and tris(4-aminophenyl)amine (0.36 g) were mixed in a mixed solvent (10 mL) of DMF and deionized water, wherein the volume ratio of DMF to deionized water was 1:0.06; the above mixture was stirred at 90 °C for 8 h to obtain a spinning solution; the spinning solution was used to prepare an electrochromic covalent organic framework precursor fiber membrane (denoted as precursor fiber membrane) by electrospinning; the electrospinning parameters were: voltage 22.5 kV, liquid supply rate 1.5 mL / h, receiving distance 15 cm, roller speed 30 r / min, the material for receiving the fiber membrane was aluminum foil, the spinning temperature was 25 ± 1 °C, and the spinning humidity was 56 ± 2%.

[0050] Step 2: Tris(4-formylphenyl)amine (5.2 mg) and acetic acid (3 M, 0.3 mL) were mixed and dissolved in mesitylene / ethanol (1:1 v / v, 30 mL) to obtain a polyaldehyde compound reaction solution; the precursor fiber membrane (20 mg) prepared in Step 1 was immersed in the polyaldehyde compound reaction solution and reacted at 120 °C for 24 h; the reacted fiber membrane was washed sequentially with DMF, water and ethanol, and then dried at 80 °C for 12 h to obtain an electrochromic covalent organic framework fiber membrane. This material has a whole-body gradient porous structure and exhibits a reversible color change from reddish-brown to dark green in the voltage range of -2.5 to 2.5 V, with a color change response time of 4.8 s.

[0051] The specific surface area of ​​the obtained electrochromic covalent organic framework fiber membrane is 289.90 m². 2 / g( Figure 1 ), pore size distribution as Figure 2 As shown. Figure 3 Scanning electron microscope (SEM) images of electrochromic covalent organic framework fiber membranes at different magnifications are shown (where (a) is 10 μm and (b) is 3 μm), and the fibers exhibit a gradient porous structure throughout; Figure 4 Cyclic voltammetry curves of electrochromic covalent organic framework fiber membranes were displayed. Figure 5 The photochromic optical images of the electrochromic covalent organic framework fiber membrane are shown.

[0052] Comparative Example 1

[0053] This comparative example provides an electrochromic covalent organic framework fiber membrane, and the preparation method is as follows:

[0054] Step 1: Polyvinylidene fluoride (molecular weight: 400,000, 1.2 g) and tris(4-aminophenyl)amine (0.36 g) were mixed in DMF (10 mL) and stirred at 90 °C for 8 h to obtain a spinning solution; the spinning solution was used to prepare an electrochromic covalent organic framework precursor fiber membrane (denoted as precursor fiber membrane) by electrospinning; the electrospinning parameters were: voltage 22.5 kV, liquid supply rate 2.5 mL / h, receiving distance 15 cm, roller speed 30 r / min, the material for receiving the fiber membrane was aluminum foil, the spinning temperature was 25 ± 1 °C, and the humidity was 56 ± 2%.

[0055] Step 2: Tris(4-formylphenyl)amine (5.2 mg) and acetic acid (3 M, 0.3 mL) were mixed and dissolved in mesitylene / ethanol (1:1 v / v, 30 mL) to obtain a polyaldehyde compound reaction solution; the precursor fiber membrane (20 mg) prepared in Step 1 was immersed in the polyaldehyde compound reaction solution and reacted at 120 °C for 24 h; the reacted fiber membrane was washed sequentially with DMF, water and ethanol, and then dried at 80 °C for 12 h to obtain an electrochromic covalent organic framework fiber membrane. This material has only a mesoporous structure and exhibits a reversible color change from reddish brown to dark brown in the voltage range of -2.5 to 2.5 V, with a color change response time of 19.1 s.

[0056] The resulting electrochromic covalent organic framework fiber membrane has a specific surface area of ​​50.6 m². 2 / g.

[0057] Example 2

[0058] This embodiment provides an electrochromic covalent organic framework fiber membrane, and the preparation method steps are as follows:

[0059] Step 1: Polyvinylidene fluoride (molecular weight: 400,000, 1.2 g), polyethylene glycol (molecular weight: 2,000,000, 0.08 g), and 1,3,5-tris(4-aminophenyl)benzene (0.36 g) were mixed in a mixed solvent (10 mL) of DMF and deionized water, wherein the volume ratio of DMF to deionized water was 50:3. The mixture was stirred at 90 °C for 8 h to obtain a spinning solution. The spinning solution was used to prepare an electrochromic covalent organic framework precursor fiber membrane (denoted as precursor fiber membrane) by electrospinning. The electrospinning parameters were: voltage 22.5 kV, liquid supply rate 1.5 mL / h, receiving distance 15 cm, roller speed 30 r / min, receiving material of fiber membrane was aluminum foil, spinning temperature was 25 ± 1 °C, and humidity was 56 ± 2%.

[0060] S2: Trialdehyde phloroglucinol (5.2 mg) and acetic acid (3 M, 0.3 mL) were mixed and dissolved in mesitylene / ethanol (1:1 v / v, 30 mL) to obtain a polyaldehyde compound reaction solution; the precursor fiber membrane (20 mg) prepared in step 1 was immersed in the polyaldehyde compound reaction solution and reacted at 120 °C for 24 h; the reacted fiber membrane was washed sequentially with DMF, water and ethanol, and then dried at 80 °C for 12 h to obtain an electrochromic covalent organic framework fiber membrane. This material has a whole-body gradient porous structure and exhibits a reversible color change from orange to brick red in the voltage range of -3 to 3 V, with a color change response time of 12.3 s.

[0061] The resulting electrochromic covalent organic framework fiber membrane has a specific surface area of ​​260.1 m².2 / g.

[0062] Comparative Example 2

[0063] This comparative example provides an electrochromic covalent organic framework fiber membrane, and the preparation method is as follows:

[0064] Step 1: Polyvinylidene fluoride (molecular weight: 400,000, 1.2 g) and 1,3,5-tris(4-aminophenyl)benzene (0.36 g) were mixed in DMF (10 mL). The mixture was stirred at 90 °C for 8 h to obtain a spinning solution. Electrochromic covalent organic framework precursor fiber membranes (denoted as precursor fiber membranes) were prepared by electrospinning of the spinning solution. The electrospinning parameters were: voltage 22.5 kV, liquid supply rate 1.5 mL / h, receiving distance 15 cm, roller speed 30 r / min, aluminum foil paper as the receiving material for the fiber membrane, spinning temperature 25 ± 1 °C, and humidity 56 ± 2%.

[0065] Step 2: Dissolve 5.2 mg of trialdehyde phloroglucinol and acetic acid (3 M, 0.3 mL) in a mixture of mesitylene / ethanol (1:1 v / v, 30 mL) to obtain a polyaldehyde compound reaction solution. Immerse the precursor fiber membrane (20 mg) obtained in Step 1 in the polyaldehyde compound reaction solution and react at 120 °C for 24 h. Wash the reacted fiber membrane sequentially with DMF, water, and ethanol, and then dry it at 80 °C for 12 h to obtain an electrochromic covalent organic framework fiber membrane. This material has only a mesoporous structure and exhibits a reversible color change from orange-yellow to brick-red in the voltage range of -3 to 3 V, with a color change response time of 28.9 s.

[0066] The specific surface area of ​​the obtained electrochromic covalent organic framework fiber membrane is 79.8 m². 2 / g.

[0067] Summary of the electrochromic properties of the electrochromic covalent organic framework fiber membranes of Examples 1-2 and Comparative Examples 1-2 (Table 1).

[0068] Table 1

[0069] Color change Drive voltage Response time Example 1 Reddish-brown to dark green -2.5～2.5V 4.8s Comparative Example 1 Reddish brown to dark brown -2.5～2.5V 19.1s Example 2 Orange-brick red -3～3V 12.3s Comparative Example 2 Orange-brick red -3～3V 28.9s

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an electrochromic covalent organic framework fiber membrane, characterized in that, Includes the following steps: Polyvinylidene fluoride, polyamine compounds and polyethylene glycol are dissolved in a mixed solvent to obtain a spinning solution, which is then electrospun to obtain a precursor fiber membrane. The precursor fiber membrane was subjected to in-situ thermal synthesis in a solution containing polyaldehyde compounds and a catalyst to obtain an electrochromic covalent organic framework fiber membrane. The molecular weight of the polyvinylidene fluoride is 400,000 to 900,000; the molecular weight of the polyethylene glycol is 2,000 to 2,000,000. The mass ratio of polyvinylidene fluoride, polyamine compound and polyethylene glycol is 1:(0.1~1):(0.01~0.1).

2. The method for preparing the electrochromic covalent organic framework fiber membrane according to claim 1, characterized in that, The polyamine compound is at least one selected from tris(4-aminophenyl)amine, 1,3,6,8-tetra-(p-aminophenyl)pyrene, and 1,3,5-tris(4-aminophenyl)benzene.

3. The method for preparing an electrochromic covalent organic framework fiber membrane according to claim 1, characterized in that, The mixed solvent is a mixture of N,N-dimethylformamide and water in a volume ratio of 1:(0 to 0.1).

4. The method for preparing the electrochromic covalent organic framework fiber membrane according to claim 1, characterized in that, The parameters for electrospinning are: voltage 15-30kV, liquid supply rate 0.2-5.0mL / min, receiving distance 10-40cm, drum speed 30-80r / min, spinning temperature 20-28℃, and spinning humidity 50-80%.

5. The method for preparing an electrochromic covalent organic framework fiber membrane according to claim 1, characterized in that, The polyaldehyde compound is at least one selected from thieno[3,2-b]thieno-2,5-dicarboxaldehyde, benzo[C][1,2,5]thiadiazole-4,7-dicarboxaldehyde, 2,6-naphthiadicarboxaldehyde, tris(4-formylphenyl)amine, and trialdehyde-resorcinol; the concentration of the polyaldehyde compound in the solution is 1.0–5.0 mM.

6. The method for preparing an electrochromic covalent organic framework fiber membrane according to claim 1, characterized in that, The catalyst is formic acid, acetic acid, or toluenesulfonic acid; the concentration of the catalyst in the solution is 20–40 mM.

7. The method for preparing an electrochromic covalent organic framework fiber membrane according to claim 1, characterized in that, The solvent used to dissolve the polyaldehyde compound and the catalyst is at least one of methanol, ethanol, 1,4-dioxane, mesitylene, benzyl alcohol, and chloroform.

8. The method for preparing an electrochromic covalent organic framework fiber membrane according to claim 1, characterized in that, The in-situ thermal synthesis reaction is carried out at a temperature of 25–120°C for 3–72 h.

9. An electrochromic covalent organic framework fiber membrane prepared by any one of claims 1-8.

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