Covalent Organic Framework Composite Nanofiber Electrochromic Film and Its Preparation and Application

Abstract

The present invention relates to a covalent organic framework composite nanofiber electrochromic film, a preparation method and an application thereof, including: preparing a polymer solution; adding tris(4-aminophenyl)amine into the polymer solution and stirring to obtain a mixed solution; performing electrospinning to obtain a composite nanofiber film; dissolving thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde and a catalyst in a solvent to obtain a reaction solution; immersing the nanofiber film in the reaction solution for reaction to obtain a crude product; washing and drying the crude product to obtain a covalent organic framework composite nanofiber electrochromic film. Compared with the prior art, in the nanofiber composite film prepared by the present invention, the covalent organic framework grows uniformly on the fiber surface, and there is no agglomeration or phase separation of the covalent organic framework; the mechanical properties of the covalent organic framework nanofilm are significantly improved, showing excellent flexibility; the covalent organic framework grows uniformly in the nanofiber film, making the fiber film have uniform color and high color saturation.

Description

Technical Field

[0001] The present invention relates to the field of nano-functional materials, and particularly to a covalent organic framework composite nanofiber electrochromic film and its preparation and application. Background Art

[0002] Covalent organic framework materials have the advantages of high specific surface area, small pore size, regular pore structure, easy regulation of structural properties, etc., and have gradually become a hot spot in the research of new functional materials. Covalent organic frameworks can be precisely prepared into various functional powder materials through solvothermal reactions by screening different monomers. Among many covalent organic framework materials, covalent organic frameworks with redox activity not only have outstanding electrical properties, but also have a unique ion intercalation / doping mechanism, excellent physical and chemical properties, and good light and thermal stability. Especially in different oxidation potential fields or external voltage environments, a series of reversible color changes can occur, making covalent organic frameworks with redox activity gradually attract attention in the field of optoelectronic materials research.

[0003] On the other hand, due to the special pore structure of covalent organic framework materials and their easily adjustable electrochemical and optical properties, they have attracted great attention in the field of new nano-functional materials and are becoming a hot field in the research of nanotechnology and materials science. However, due to the large cross-linking degree and high crystallinity of the molecular structure of covalent organic frameworks, there are strong intermolecular interlayer forces, resulting in poor solubility and film-forming properties, and the corresponding processing performance is also affected. The existing covalent organic framework nanofilm materials have low mechanical strength, are prone to interlayer peeling, and have poor use stability, which limits their wide application in technology. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned existing technologies and provide a covalent organic framework composite nanofiber electrochromic film and its preparation and application, so as to solve the problems of poor processing performance, low mechanical strength, and poor stability of the covalent organic framework composite nanofilm materials.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The first aspect of the present invention provides a preparation method of a covalent organic framework composite nanofiber electrochromic film, including the following steps:

[0007] S1: Dissolve the blended polymer in a solvent in a stirring kettle to obtain a polymer solution;

[0008] S2: Add tris(4-aminophenyl)amine to the polymer solution, stir and mix evenly to obtain a mixed solution;

[0009] S3: Electrospin the mixed solution to obtain a composite nanofiber film;

[0010] S4: Dissolve thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde and a catalyst in a solvent to obtain a reaction solution, where the mass fraction of thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde in the reaction solution is 0.01%-0.2%, and the mass fraction of the catalyst is 1%-3%;

[0011] S5: Immerse the nanofiber membrane in the reaction solution and react to obtain a crude product;

[0012] S6: Wash and dry the crude product to obtain a covalent organic framework composite nanofiber electrochromic membrane.

[0013] Further, in S1, the blended polymer is selected from one or a mixture of two or more of polyacrylonitrile, nylon 6, polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, polyacrylic acid, ethylene-vinyl alcohol copolymer, polylactic acid, and polymethyl methacrylate.

[0014] Further, in S1, the solvent is selected from one or a mixture of two or more of formic acid, acetic acid, water, isopropanol, perfluorooctanoic acid, hexafluoroisopropanol, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, and ethanol.

[0015] Further, in S1, the stirring speed is 200-800 rpm to obtain a polymer solution with a mass fraction of 8%-30%;

[0016] In S2, the stirring speed is 200-800 rpm to obtain a mixed solution with a mass fraction of tris(4-aminophenyl)amine of 8%-30%.

[0017] Further, in S3, the specific process of electrospinning is as follows:

[0018] Under the conditions of room temperature and a relative humidity of 20%-60%, input the mixed solution into the spinneret of an electrospinning device at a voltage of 10 kV-30 kV and a speed of 0.1-2 mL / h for electrospinning to obtain a composite nanofiber membrane, and the distance between the receiving device and the spinneret is 10-20 cm.

[0019] Further, in S4, the solvent is selected from one or a mixture of two or more of benzyl alcohol, mesitylene, chloroform, dichloromethane, trichloromethane, tetrahydrofuran, 1,4-epoxyhexane, and o-dichlorobenzene;

[0020] In S4, the catalyst is one or a mixture of two or more of formic acid, acetic acid, phosphoric acid, hydrochloric acid, and sulfuric acid.

[0021] Further, in S5, the reaction conditions are to react at 25 - 120 °C for 12 - 72 h;

[0022] In S6, the drying conditions are: drying at 25 - 80 °C for 1 - 24 h.

[0023] Further, in S6, the washing solvent is selected from one or a mixture of two or more of water, ethanol, methanol, benzyl alcohol, mesitylene, chloroform, dichloromethane, trichloromethane, tetrahydrofuran, 1,4 - epoxyhexane, and o - dichlorobenzene.

[0024] The second aspect of the present invention provides a covalent organic framework composite nanofiber electrochromic film obtained by the above - mentioned preparation method.

[0025] Further, in the prepared nano - composite fiber film, the covalent organic framework grows uniformly on the fiber surface, and there is no agglomeration or phase separation of the covalent organic framework; significantly improves the mechanical properties of the covalent organic framework nano - film, showing excellent flexibility; the covalent organic framework grows uniformly in the nanofiber film, making the fiber film have uniform color and high color saturation.

[0026] Further, based on the unique electrolyte ion intercalation - deintercalation behavior of the covalent organic framework, which leads to different oxidation state transitions, this fiber film can achieve a series of reversible color changes.

[0027] The third aspect of the present invention provides an application of the above - mentioned covalent organic framework composite nanofiber electrochromic film in electrochromic devices, or light - electricity energy switches, or optical sensors, or light information regulation devices, or information storage devices, or camouflage stealth materials.

[0028] Compared with the prior art, the present invention has the following technical advantages:

[0029] 1) By means of the solution blending electrospinning technology, the present invention realizes the homogeneous co - fibrillation of covalent organic framework monomers and blended polymers, and then through a solid - liquid interface reaction with a second monomer under the action of a catalyst, a covalent organic framework composite nanofiber material is obtained. In the nano - composite fiber film prepared by this method, the covalent organic framework grows uniformly on the fiber surface, and there is no agglomeration or phase separation of the covalent organic framework. Therefore, it significantly improves the mechanical properties of the covalent organic framework nano - film, showing excellent flexibility. The covalent organic framework grows uniformly in the nanofiber film, making the fiber film have uniform color and high color saturation. Based on the unique electrolyte ion intercalation - deintercalation behavior of the covalent organic framework, which leads to different oxidation state transitions, this fiber film can achieve a series of reversible color changes.

[0030] 2) The covalent organic framework composite nanofiber membrane provided by the present invention has excellent flexibility, solvent corrosion resistance, high temperature resistance, good film-forming property, and good adhesion to various substrates. At the same time, it has uniform color rendering and high color saturation, and can achieve a series of cyclic color changes under electric drive. It has broad application prospects in the fields of electrochromic devices, light-electric energy switches, optical sensors, optical information regulation, information storage, camouflage stealth, etc. Description of the Drawings

[0031] Figure 1 Optical photograph of the covalent organic framework composite nanofiber electrochromic membrane with polyacrylonitrile as the supporting polymer in Example 1.

[0032] Figure 2 Electron microscope photograph of the covalent organic framework composite nanofiber electrochromic membrane with polyacrylonitrile as the supporting polymer in Example 1.

[0033] Figure 3 Nitrogen adsorption isotherm and pore size distribution curve of the covalent organic framework composite nanofiber electrochromic membrane with polyacrylonitrile as the supporting polymer in Example 1.

[0034] Figure 4 Tensile fracture curve of the covalent organic framework composite nanofiber electrochromic membrane with polyacrylonitrile as the supporting polymer in Example 1. Detailed Description of the Invention

[0035] The present invention provides a preparation method for a covalent organic framework composite nanofiber electrochromic membrane, and the specific steps are as follows:

[0036] First step: At room temperature, dissolve the blended polymer in a solvent in a stirring kettle, with a stirring speed of 200 - 800 rpm, to obtain a polymer solution with a mass fraction of 8% - 30%.

[0037] Second step: At room temperature, add tris(4-aminophenyl)amine to the polymer solution obtained in the first step, with a stirring speed of 200 - 800 rpm, and mix evenly to obtain a mixed solution with a mass fraction of tris(4-aminophenyl)amine of 8% - 30%.

[0038] Third step: Under the conditions of room temperature and a relative humidity of 20% - 60%, input the mixed solution obtained in the second step onto the spinneret of an electrospinning device at a voltage of 10 kV - 30 kV and a speed of 0.1 - 2.0 mL / h for electrospinning to obtain a composite nanofiber membrane, and the distance between the receiving device and the spinneret is 10 - 20 cm.

[0039] Step 4: Dissolve thiophene[3,2-b]thiophene-2,5-dicarbaldehyde and a catalyst in a solvent at room temperature, where the mass fraction of thiophene[3,2-b]thiophene-2,5-dicarbaldehyde is 0.01%-0.2%, and the mass fraction of the catalyst is 1%-3%.

[0040] Step 5: Immerse the nanofiber membrane obtained on the receiving device into the solution prepared in Step 4, and react at 25-120°C for 12-72 h;

[0041] Step 6: Wash with a solvent, and then dry at 25-80°C for 1-24 h to obtain a covalent organic framework composite nanofiber electrochromic membrane.

[0042] The blended polymer in the first step is one or a mixture of two or more of polyacrylonitrile, nylon 6, polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, polyacrylic acid, ethylene-vinyl alcohol copolymer, polylactic acid, and polymethyl methacrylate.

[0043] The solvent in the first step is one or a mixture of two or more of formic acid, acetic acid, water, isopropyl alcohol, perfluorooctanoic acid, hexafluoroisopropanol, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, and ethanol.

[0044] The solvent in the fourth step is one or a mixture of two or more of benzyl alcohol, mesitylene, chloroform, dichloromethane, trichloromethane, tetrahydrofuran, 1,4-epoxyhexane, and o-dichlorobenzene.

[0045] The catalyst in the fourth step is one or a mixture of two or more of formic acid, acetic acid, phosphoric acid, hydrochloric acid, and sulfuric acid.

[0046] The washing solvent in the sixth step is one or a mixture of two or more of water, ethanol, methanol, benzyl alcohol, mesitylene, chloroform, dichloromethane, trichloromethane, tetrahydrofuran, 1,4-epoxyhexane, and o-dichlorobenzene.

[0047] The present invention will be described in detail below with reference to specific embodiments. Features such as preparation means, materials, structures, equipment, or composition ratios that are not clearly stated in this technical solution are regarded as common technical features disclosed in the prior art.

[0048] The covalent organic framework monomers, blended polymers for spinning, and solvents in the following examples can be purchased from Aladdin Reagent (Shanghai) Co., Ltd.; the high-voltage power supply is the DW-P303-1ACD8 type produced by Tianjin Dongwen High-Voltage Power Supply Factory; the electrospinning device is purchased from Hangzhou Zhongxie Environmental Protection Technology Co., Ltd.

[0049] The specific surface area and porosity of the covalent organic framework composite nanofiber electrochromic film prepared in the following examples were measured by the ASAP 2000 specific surface and porosity analyzer of the American company McMurtrytik; the tensile breaking strength and bending test of the nanofiber membrane were measured by the Shengte Nanomembrane (single fiber) portable comprehensive strength tester, with the fiber membrane width of 5 mm, thickness of 0.2 mm, initial clamping distance of 4 mm, and tensile rate of 10 mm / min; the thermal stability of the nanofiber membrane was measured by the TGA2 of Mettler Toledo, Switzerland.

[0050] Example 1

[0051] At room temperature of 25°C, 0.8 g of polyacrylonitrile (molecular weight 150,000) was dissolved in 7.4 g of N,N-dimethylformamide in a stirring vessel at a speed of 800 rpm. After the polyacrylonitrile was completely dissolved, 0.8 g of tris(4-aminophenyl)amine was added to the solution and stirred at a speed of 500 rpm to obtain a blended spinning solution with a mass fraction of polyacrylonitrile of 8% and a mass fraction of tris(4-aminophenyl)amine of 8%.

[0052] At room temperature of 25°C and humidity of 60%, the blended spinning solution was input into the spinneret at a jet velocity of 1.0 mL / h, and the spinneret was connected to a 20 kV power supply for electrospinning to prepare tri(4-aminophenyl)amine / polyacrylonitrile blended nanofiber membrane; the spun fibers were deposited on a wax paper receiving device, and the distance between the receiving device and the spinneret was 15 cm.

[0053] After spinning is completed, the fiber membrane is immersed in a benzyl alcohol solution containing 0.08% thieno[3,2-b]thiophene-2,5-dicarboxaldehyde and 3% acetic acid as a catalyst, and reacted at room temperature for 72 hours; the fiber membrane after the reaction is completed is washed with benzyl alcohol, water, and ethanol in sequence, and then placed in a vacuum oven and dried at 60°C for 12 hours, and finally a red covalent organic framework / polyacrylonitrile blended nanofiber membrane (such as Figure 1 shown).

[0054] In the three-electrode cyclic voltammetry test, the covalent organic framework composite nanofiber membrane can undergo a reversible transformation between light red and dark red under the action of an applied voltage.

[0055] Figure 2 This is an electron microscope photograph of the covalent organic framework composite nanofiber electrochromic film using polyacrylonitrile as the supporting polymer in this embodiment. Figure 3 1 is the nitrogen adsorption isotherm and pore size distribution curve of the covalent organic framework composite nanofiber electrochromic film with polyacrylonitrile as the supporting polymer in this embodiment. Figure 4This is the tensile fracture curve of the covalent organic framework composite nanofiber electrochromic film with polyacrylonitrile as the supporting polymer in this implementation.

[0056] In terms of specific data, the specific surface area of the prepared covalent organic framework composite nanofiber membrane was measured by a specific surface area analyzer to be 88.65 m 2 / g, and the average pore size was 4.93 nm; the breaking strength of the prepared covalent organic framework composite nanofiber membrane was measured by a single fiber tensile tester to be 62.2 kPa, and no obvious defects were found after bending 50 times; the thermal decomposition temperature of the prepared covalent organic framework composite nanofiber membrane was measured by thermogravimetric analysis to be 330 °C.

[0057] Example 2

[0058] At room temperature of 25 °C, 1.0 g of polyvinyl alcohol (molecular weight 200000) was stirred and dissolved in 8.0 g of dimethyl sulfoxide solvent in a stirring kettle at a rotation speed of 800 rpm. After the polyvinyl alcohol was completely dissolved, 1.0 g of tris(4-aminophenyl)amine was added to the solution and stirred at a rotation speed of 500 rpm to obtain a blend spinning solution with a polyvinyl alcohol mass fraction of 10% and a tris(4-aminophenyl)amine mass fraction of 10%.

[0059] At room temperature of 25 °C and humidity of 30%, the blend spinning solution was input into the spinneret at a jet velocity of 1.8 mL / h, and at the same time, the spinneret was connected to a 25 kV power supply for electrospinning to prepare a tris(4-aminophenyl)amine / polyvinyl alcohol blend nanofiber membrane; the spun fibers were deposited on a wax paper receiving device, and the distance between the receiving device and the spinneret was 15 cm.

[0060] After the electrospinning was completed, the fiber membrane was immersed in a dichloromethane solution containing 0.10% by mass of thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde and 3% acetic acid as a catalyst and reacted at room temperature for 72 h; the reacted fiber membrane was washed successively with dichloromethane and acetone, and then placed in a vacuum oven and dried at 80 °C for 24 h to finally obtain a red covalent organic framework / polyvinyl alcohol blend nanofiber membrane.

[0061] In the three-electrode cyclic voltammetry test, the covalent organic framework composite nanofiber membrane can undergo a reversible transformation between light red and dark red under the action of an applied voltage.

[0062] In terms of specific data, the specific surface area of the prepared covalent organic framework composite nanofiber membrane was measured by a specific surface area analyzer to be 76.25 m 2 / g, with an average pore size of 6.32 nm; the breaking strength of the prepared covalent organic framework composite nanofiber membrane tested by a single fiber tensile tester is 62.5 kPa, and no obvious defects are found after bending 50 times; the thermal decomposition temperature of the prepared covalent organic framework composite nanofiber membrane tested by thermogravimetric analysis is 356 °C.

[0063] Example 3

[0064] At room temperature of 25 °C, 1.5 g of nylon 6 (molecular weight 180,000) was stirred and dissolved in 7.0 g of formic acid in a stirring kettle at a rotation speed of 200 rpm. After nylon 6 was completely dissolved, 1.5 g of tris(4-aminophenyl)amine was added to the solution and stirred at a rotation speed of 500 rpm to obtain a blend spinning solution with a nylon 6 mass fraction of 15% and a tris(4-aminophenyl)amine mass fraction of 15%.

[0065] Under the conditions of room temperature of 25 °C and humidity of 50%, the blend spinning solution was input into the spinneret at a jet speed of 0.5 mL / h, and at the same time, the spinneret was connected to a 30 kV power supply for electrospinning to prepare a tris(4-aminophenyl)amine / nylon 6 blend nanofiber membrane; the spun fibers were deposited on a wax paper receiving device, and the distance between the receiving device and the spinneret was 15 cm; after the electrospinning was completed, the fiber membrane was immersed in a tetrahydrofuran solution containing 0.15% by mass of thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde and 1% acetic acid as a catalyst and reacted at room temperature for 72 h.

[0066] The reacted fiber membrane was washed successively with tetrahydrofuran, ethanol, and water, then placed in a vacuum oven and dried at 60 °C for 24 h, and finally a red covalent organic framework / nylon 6 blend nanofiber membrane could be obtained.

[0067] In the three-electrode cyclic voltammetry test, the covalent organic framework composite nanofiber membrane can undergo a reversible transformation between light red and dark red under the action of an applied voltage.

[0068] Specifically, the specific surface area of the prepared covalent organic framework composite nanofiber membrane tested by a specific surface area analyzer is 105.52 m 2 / g, with an average pore size of 5.32 nm; the breaking strength of the prepared covalent organic framework composite nanofiber membrane tested by a single fiber tensile tester is 52.6 kPa, and no obvious defects are found after bending 50 times; the thermal decomposition temperature of the prepared covalent organic framework composite nanofiber membrane tested by thermogravimetric analysis is 443 °C.

[0069] Example 4

[0070] At room temperature of 25°C, 0.05 g of polyacrylamide (molecular weight 2,000,000) was stirred and dissolved in 8.85 g of a mixed solvent of acetic acid and formic acid (mass ratio 1:5) in a stirring kettle at a rotation speed of 500 rpm. After the polyacrylamide was completely dissolved, 1.0 g of tris(4-aminophenyl)amine was added to the solution and stirred at a rotation speed of 500 rpm to obtain a blend spinning solution with a polyacrylamide mass fraction of 0.5% and a tris(4-aminophenyl)amine mass fraction of 1.0%.

[0071] Under the conditions of room temperature of 25°C and humidity of 30%, the blend spinning solution was input into the spinneret at a jet velocity of 1.5 mL / h, and at the same time, the spinneret was connected to a 20 kV power supply for electrospinning to prepare a tris(4-aminophenyl)amine / polyacrylamide blend nanofiber membrane; the spun fibers were deposited on an aluminum foil receiving device, and the distance between the receiving device and the spinneret was 10 cm; after the electrospinning was completed, the fiber membrane was immersed in a benzyl alcohol solution containing 0.10% by mass of thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde and 3% acetic acid as a catalyst and reacted at room temperature for 72 h.

[0072] The reacted fiber membrane was washed successively with benzyl alcohol, water, and ethanol, then placed in a vacuum oven and dried at 40°C for 6 h, and finally a red covalent organic framework / polyacrylamide blend nanofiber membrane could be obtained.

[0073] In the three-electrode cyclic voltammetry test, the covalent organic framework composite nanofiber membrane can undergo a reversible transformation between light red and dark red under the action of an applied voltage.

[0074] Specifically, the specific surface area of the prepared covalent organic framework composite nanofiber membrane was measured to be 69.33 m 2 / g by a specific surface area analyzer, and the average pore diameter was 4.89 nm; the breaking strength of the prepared covalent organic framework composite nanofiber membrane was measured to be 55.7 kPa by a single fiber tensile tester, and no obvious defects were observed after bending 50 times; the thermal decomposition temperature of the prepared covalent organic framework composite nanofiber membrane was measured to be 380°C by thermogravimetric analysis.

[0075] Example 5

[0076] At room temperature of 25°C, 3.0 g of polyvinylpyrrolidone (molecular weight 40,000) was stirred and dissolved in 4.0 g of a mixed solvent of formic acid and tetrahydrofuran (mass ratio 10:1) in a stirring kettle at a rotation speed of 500 rpm. After the polyvinylpyrrolidone was completely dissolved, 3.0 g of tris(4-aminophenyl)amine was added to the solution and stirred at a rotation speed of 500 rpm to obtain a blend spinning solution with a polyvinylpyrrolidone mass fraction of 30% and a tris(4-aminophenyl)amine mass fraction of 30%.

[0077] Under the conditions of room temperature of 25 °C and humidity of 20%, the blend spinning solution was input into the spinneret at a jet velocity of 2.0 mL / h. At the same time, the spinneret was connected to a 25 kV power supply for electrospinning to prepare a tris(4-aminophenyl)amine / polyvinylpyrrolidone blend nanofiber membrane; the spun fibers were deposited on a non-woven receiving device, and the distance between the receiving device and the spinneret was 16 cm; after the electrospinning was completed, the fiber membrane was immersed in a chloroform solution containing 0.20% by mass of thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde and 3% acetic acid as a catalyst, and reacted at room temperature for 72 h.

[0078] The reacted fiber membrane was washed successively with chloroform, ethanol, and water, and then placed in a vacuum oven and dried at 60 °C for 24 h. Finally, a red covalent organic framework polyvinylpyrrolidone blend nanofiber membrane could be obtained.

[0079] In the three-electrode cyclic voltammetry test, the covalent organic framework composite nanofiber membrane could undergo a reversible transformation between light red and dark red under the action of an applied voltage.

[0080] Specifically, the specific surface area of the prepared covalent organic framework composite nanofiber membrane was measured to be 88.65 m 2 / g by a specific surface area analyzer, and the average pore size was 5.10 nm; the breaking strength of the prepared covalent organic framework composite nanofiber membrane was 49.0 kPa measured by a single fiber tensile tester, and no obvious defects were observed after bending 50 times; the thermal decomposition temperature of the prepared covalent organic framework composite nanofiber membrane was 426 °C measured by thermogravimetric analysis.

[0081] Example 6

[0082] At room temperature of 25 °C, 1.0 g of polyacrylic acid (molecular weight 250,000) was stirred and dissolved in a mixed solvent of 8.0 g of hexafluoroisopropanol and perfluorooctanoic acid (mass ratio 3:1) in a stirring kettle at a rotation speed of 500 rpm. After the polyacrylic acid was completely dissolved, 1.0 g of tris(4-aminophenyl)amine was added to the solution and stirred at a rotation speed of 500 rpm to obtain a blend spinning solution with a mass fraction of polyacrylic acid of 10% and a mass fraction of tris(4-aminophenyl)amine of 10%.

[0083] Under the conditions of room temperature of 25 °C and humidity of 40%, the blend spinning solution was input into the spinneret at a jet velocity of 0.2 mL / h, and at the same time, the spinneret was connected to a 25 kV power supply for electrospinning to prepare a tris(4-aminophenyl)amine / polyacrylic acid blend nanofiber membrane; the spun fibers were deposited onto an aluminum foil receiving device, and the distance between the receiving device and the spinneret was 12 cm; after the electrospinning was completed, the fiber membrane was immersed in a mesitylene solution containing 0.10% by mass of thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde and 3% acetic acid as a catalyst, and reacted at room temperature for 72 h.

[0084] The fiber membrane after the reaction was washed successively with mesitylene, water, and ethanol, and then placed in a vacuum oven and dried at 80 °C for 2 h. Finally, a red covalent organic framework / polyacrylic acid blend nanofiber membrane could be obtained.

[0085] In the three-electrode cyclic voltammetry test, the covalent organic framework composite nanofiber membrane could undergo a reversible transformation between light red and dark red under the action of an applied voltage.

[0086] Specifically, the specific surface area of the prepared covalent organic framework composite nanofiber membrane was measured to be 59.88 m 2 / g by a specific surface area analyzer, and the average pore size was 6.23 nm; the breaking strength of the prepared covalent organic framework composite nanofiber membrane was 55.8 kPa measured by a single fiber tensile tester, and no obvious defects were observed after bending 50 times; the thermal decomposition temperature of the prepared covalent organic framework composite nanofiber membrane was 301 °C measured by thermogravimetric analysis.

[0087] Example 7

[0088] At 80 °C, 0.8 g of ethylene-vinyl alcohol copolymer (molecular weight 200,000) was stirred and dissolved in a mixed solvent of 7.6 g of water and isopropanol (mass ratio 3:7) in a stirred tank at a rotation speed of 500 rpm. After the ethylene-vinyl alcohol copolymer was completely dissolved, 1.6 g of tris(4-aminophenyl)amine was added to the solution and stirred at a rotation speed of 500 rpm to obtain a blend spinning solution with a mass fraction of ethylene-vinyl alcohol copolymer of 8% and a mass fraction of tris(4-aminophenyl)amine of 16%.

[0089] Under the conditions of room temperature of 25°C and humidity of 40%, the blend spinning solution was input into the spinneret at a jet velocity of 0.8 mL / h, and at the same time, the spinneret was connected to a 20 kV power supply for electrospinning to prepare a blend nanofiber membrane of tris(4-aminophenyl)amine / ethylene-vinyl alcohol copolymer; the spun fibers were deposited onto an aluminum foil receiving device, and the distance between the receiving device and the spinneret was 15 cm; after the electrospinning was completed, the fiber membrane was immersed in a dichloromethane solution containing 0.16% by mass of thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde and 3% acetic acid as a catalyst, and reacted at room temperature for 72 h.

[0090] The fiber membrane after the reaction was washed successively with dichloromethane, water, and ethanol, and then placed in a vacuum oven and dried at 80°C for 4 h. Finally, a red covalent organic framework ethylene-vinyl alcohol copolymer blend nanofiber membrane could be obtained.

[0091] In the three-electrode cyclic voltammetry test, the covalent organic framework composite nanofiber membrane could undergo a reversible transformation between light red and dark red under the action of an applied voltage.

[0092] Specifically, the specific surface area of the prepared covalent organic framework composite nanofiber membrane was measured by a specific surface area analyzer to be 78.44 m 2 / g, and the average pore size was 5.98 nm; the breaking strength of the prepared covalent organic framework composite nanofiber membrane was measured by a single fiber tensile tester to be 63.5 kPa, and no obvious defects were observed after bending 50 times; the thermal decomposition temperature of the prepared covalent organic framework composite nanofiber membrane was measured by thermogravimetric analysis to be 438°C.

[0093] Example 8

[0094] At room temperature of 25°C, 1.0 g of polylactic acid (molecular weight 150,000) was stirred and dissolved in 8.0 g of a mixed solvent of formic acid and hexafluoroisopropanol (mass ratio 4:1) in a stirring kettle at a rotation speed of 500 rpm. After the polylactic acid was completely dissolved, 1.0 g of tris(4-aminophenyl)amine was added to the solution, and stirring was carried out at a rotation speed of 500 rpm to obtain a blend spinning solution with a polylactic acid mass fraction of 10% and a tris(4-aminophenyl)amine mass fraction of 10%.

[0095] Under the conditions of room temperature of 25 °C and humidity of 40%, the blend spinning solution was input into the spinneret at a jet velocity of 2.0 mL / h, and at the same time, the spinneret was connected to a 25 kV power supply for electrospinning to prepare a tris(4-aminophenyl)amine / polylactic acid blend nanofiber membrane; the spun fibers were deposited on an aluminum foil receiving device, and the distance between the receiving device and the spinneret was 8 cm; after the electrospinning was completed, the fiber membrane was immersed in a dichloromethane solution containing 0.10% by mass of thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde and 3% acetic acid as a catalyst, and reacted at room temperature for 72 h.

[0096] The reacted fiber membrane was washed successively with dichloromethane, ethanol, and water, and then placed in a vacuum oven and dried at 80 °C for 2 h. Finally, a red covalent organic framework-polylactic acid blend nanofiber membrane could be obtained.

[0097] In the three-electrode cyclic voltammetry test, the covalent organic framework composite nanofiber membrane could undergo a reversible transformation between light red and dark red under the action of an applied voltage.

[0098] Specifically, the specific surface area of the prepared covalent organic framework composite nanofiber membrane was measured to be 69.55 m 2 / g by a specific surface area analyzer, and the average pore size was 6.02 nm; the breaking strength of the prepared covalent organic framework composite nanofiber membrane was 62.8 kPa measured by a single fiber tensile tester, and no obvious defects were found after bending 50 times; the thermal decomposition temperature of the prepared covalent organic framework composite nanofiber membrane was 345 °C measured by thermogravimetric analysis.

[0099] Example 9

[0100] At room temperature of 25 °C, 1.5 g of polymethyl methacrylate (molecular weight 700000) was stirred and dissolved in 7.0 g of a formic acid and ethanol mixed solvent (mass ratio 9:1) in a stirring kettle at a rotation speed of 800 rpm. After the polymethyl methacrylate was completely dissolved, 1.5 g of tris(4-aminophenyl)amine was added to the solution, and stirring was carried out at a rotation speed of 500 rpm to obtain a blend spinning solution with a mass fraction of polymethyl methacrylate of 15% and a mass fraction of tris(4-aminophenyl)amine of 15%.

[0101] Under the conditions of room temperature of 25 °C and humidity of 60%, the blend spinning solution was input into the spinneret at a jet velocity of 4.0 mL / h, and at the same time, the spinneret was connected to a 30 kV power supply for electrospinning to prepare a tris(4-aminophenyl)amine / polymethyl methacrylate blend nanofiber membrane; the spun fibers were deposited on an aluminum foil receiving device, and the distance between the receiving device and the spinneret was 20 cm; after the electrospinning was completed, the fiber membrane was immersed in a benzyl alcohol solution containing 0.15% by mass of thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde and 3% acetic acid as a catalyst, and reacted at room temperature for 72 h.

[0102] The fiber membrane after the reaction was washed successively with benzyl alcohol, water, and ethanol, and then placed in a vacuum oven and dried at 80 °C for 2 h. Finally, a red covalent organic framework-polymethyl methacrylate blend nanofiber membrane could be obtained.

[0103] In the three-electrode cyclic voltammetry test, the covalent organic framework composite nanofiber membrane could undergo a reversible transformation between light red and dark red under the action of an applied voltage.

[0104] Specifically, the specific surface area of the prepared covalent organic framework composite nanofiber membrane was measured to be 98.66 m 2 / g by a specific surface area analyzer, and the average pore diameter was 5.68 nm; the breaking strength of the prepared covalent organic framework composite nanofiber membrane was 60.9 kPa measured by a single fiber tensile tester, and no obvious defects were found after bending 50 times; the thermal decomposition temperature of the prepared covalent organic framework composite nanofiber membrane was 388 °C measured by thermogravimetric analysis.

[0105] The structure of the covalent organic framework in the above examples is only a special case. Monomers that can be used to construct electrochromic covalent organic framework composite nanofiber membranes also include: 1,3,6,8-tetra-(p-aminophenyl)pyrene, 1,3,5-tris(4-aminophenyl)benzene, N,N,N',N'-tetra(p-aminophenyl)terephthalenediamine, p-phenylenediamine, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, benzo[c][1,2,5]thiadiazole-4,7-dicarboxaldehyde, 2,6-naphthalenedicarboxaldehyde, 2,5-dialdehyde pyridine, etc.

[0106] Comparative Example 1

[0107] CN101967279A discloses a preparation method of a reversible color-changing film of polyaniline composite nanofibers, which is characterized in that the specific steps are as follows: at room temperature, dissolve the pristine polyaniline raw material in a stirring kettle to obtain a polyaniline solution with a mass fraction of 0.2%-15%; at room temperature, add the blended polymer into the polyaniline solution and mix evenly to obtain a solution with a mass fraction of the blended polymer of 0.5%-30%; at room temperature and a relative humidity of 20%-60%, input the solution into the spinneret of an electrospinning device at a flow rate of 0.1-4 mL / h to carry out electrospinning to prepare nanofibers; dry the nanofiber film obtained on the receiving device at 25-80 °C for 1-12 h to obtain the reversible color-changing film of polyaniline composite nanofibers.

[0108] Compared with CN101967279A, in terms of material preparation, the present invention is different from the method of physically blending to prepare a color-changing nanofiber film. The present invention uses an in-situ polymerization method to in-situ grow a covalently organic framework with electrochromic function on the surface of the supporting polymer, so that the final nanofiber film has higher color saturation and better color uniformity (as Figure 1 shown). In terms of the color-changing mechanism and performance of the material, the present invention is characterized in that the high specific surface area and mesoporous structure of the covalently organic framework electrochromic nanofiber film can effectively enhance the contact between the material and electrolyte ions, thereby optimizing the electrochromic performance of the fiber film. The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. Those skilled in the art can obviously make various modifications to these embodiments easily and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A preparation method of a covalent organic framework composite nanofiber electrochromic film, characterized in that, It includes the following steps: S1: Dissolve the blended polymer in a solvent in a stirring kettle to obtain a polymer solution; S2: Add tris(4-aminophenyl)amine to the polymer solution, stir and mix evenly to obtain a mixed solution; S3: Electrospin the mixed solution to obtain a composite nanofiber membrane; S4: Dissolve thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde and a catalyst in a solvent to obtain a reaction solution, where the mass fraction of thiophene[3,2-b]thiophene-2,5-dicarboxaldehyde in the reaction solution is 0.01%-0.2%, and the mass fraction of the catalyst is 1%-3%; S5: Immerse the nanofiber membrane in the reaction solution and react to obtain a crude product; S6: Wash and dry the crude product to obtain a covalent organic framework composite nanofiber electrochromic membrane.

2. The preparation method of a covalent organic framework composite nanofiber electrochromic film according to claim 1, characterized in that, In S1, the blended polymer is selected from one or a mixture of two or more of polyacrylonitrile, nylon 6, polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, polyacrylic acid, ethylene-vinyl alcohol copolymer, polylactic acid, and polymethyl methacrylate.

3. The preparation method of a covalent organic framework composite nanofiber electrochromic film according to claim 1, characterized in that, In S1, the solvent is selected from one or a mixture of two or more of formic acid, acetic acid, water, isopropyl alcohol, perfluorooctanoic acid, hexafluoroisopropanol, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, and ethanol.

4. The preparation method of a covalent organic framework composite nanofiber electrochromic film according to claim 1, characterized in that, In S1, the stirring speed is 200-800 rpm to obtain a polymer solution with a mass fraction of 8%-30%; In S2, the stirring speed is 200-800 rpm to obtain a mixed solution with a mass fraction of tris(4-aminophenyl)amine of 8%-30%.

5. The preparation method of a covalent organic framework composite nanofiber electrochromic film according to claim 1, characterized in that, In S3, the specific process of electrospinning is as follows: Under the conditions of room temperature and a relative humidity of 20%-60%, input the mixed solution onto the spinneret of an electrospinning device at a voltage of 10 kV-30 kV at a speed of 0.1-2 mL / h for electrospinning to obtain a composite nanofiber membrane, and make the distance between the receiving device and the spinneret be 10-20 cm.

6. The preparation method of a covalent organic framework composite nanofiber electrochromic film according to claim 1, characterized in that, In S4, the solvent is selected from one or a mixture of two or more of benzyl alcohol, mesitylene, chloroform, dichloromethane, trichloromethane, tetrahydrofuran, 1,4-epoxyhexane, and o-dichlorobenzene; In S4, the catalyst is one or a mixture of two or more of formic acid, acetic acid, phosphoric acid, hydrochloric acid, and sulfuric acid.

7. The preparation method of a covalent organic framework composite nanofiber electrochromic film according to claim 1, characterized in that, In S5, the reaction conditions are to react at 25-120 °C for 12-72 h; In S6, the drying conditions are: drying at 25-80 °C for 1-24 h.

8. The preparation method of a covalently organic framework composite nanofiber electrochromic film according to claim 1, characterized in that In S6, the washing solvent is selected from one or a mixture of two or more of water, ethanol, methanol, benzyl alcohol, mesitylene, chloroform, dichloromethane, trichloromethane, tetrahydrofuran, 1,4-epoxyhexane, and o-dichlorobenzene.

9. A covalent organic framework composite nanofiber electrochromic membrane obtained by the preparation method according to any one of claims 1 to 8.

10. Application of the covalent organic framework composite nanofiber electrochromic membrane according to claim 9 in the preparation of electrochromic devices, light-electric energy switches, optical sensors, optical information regulation devices, information storage devices, or camouflage stealth materials.

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