Preparation of covalent organic framework fiber membrane and application of covalent organic framework fiber membrane in catalytic degradation of antibiotics

Abstract

The invention relates to the field of photocatalytic water treatment of organic pollutants, in particular to preparation of a covalent organic framework fiber membrane and application of the covalent organic framework fiber membrane in catalytic degradation of antibiotics. The preparation process of the covalent organic framework fiber membrane comprises the following steps: uniformly dispersing the functional COF photocatalyst in a membrane casting agent and an organic solvent, uniformly stirring to obtain a spinning solution, applying the spinning solution to electrostatic spinning, and drying after the electrostatic spinning is finished to obtain the covalent organic framework fiber membrane. The covalent organic framework fiber membrane provided by the invention shows good performance of photocatalytic degradation of antibiotic pollution in a water environment, overcomes the problems of low degradation efficiency, difficult recovery and poor reutilization effect of a traditional photocatalyst, and can be used as a photocatalytic system without adding an additional oxidant. The method can be applied to antibiotic removal processes in various water environments, is simple to operate and high in feasibility, and has good environmental and social benefits.

Description

Technical Field

[0001] The invention relates to the field of photocatalytic water treatment of organic pollutants, and in particular to the preparation of covalent organic framework fiber membranes and the application of the same in catalytic degradation of antibiotics. Background Art

[0002] Antibiotics, as a class of compounds that can inhibit the proliferation of microorganisms, are widely used in the prevention and treatment of infectious diseases in humans and animals. As a result, a large number of antibiotics enter the environmental water bodies. Although the concentration level of antibiotics in natural water bodies is very low, most types of antibiotics are not easily degraded and are relatively stable in the water environment. Even if the concentration level of antibiotics is low, they may directly cause toxicity to aquatic organisms, such as causing phytoplankton poisoning, inhibiting the communication between microorganisms, and changing the structure of microbial communities. In addition, the long-term presence of antibiotic pollution in the environment induces the occurrence of drug-resistant bacteria, which ultimately harms human health during the process of biomagnification.

[0003] The use of photocatalytic oxygen activation degradation technology to remove antibiotic pollution in water environments is a relatively new water treatment method. In this process, dissolved oxygen in water is converted into active oxygen species to destroy antibiotic molecules, which are further converted into small molecules or mineralized. The photocatalytic oxygen activation degradation technology has mild reaction conditions, is green and environmentally friendly, and has no secondary pollution. Among them, covalent organic frameworks (COFs) are an emerging crystalline porous organic polymer with advantages such as large specific surface area, flexible and easy-to-regulate structure, controllable performance, and easy functionalization. They are often used as photocatalytic oxygen activation degradation technology for organic polluted water treatment.

[0004] However, there are still some shortcomings in the application of COF materials in the field of photocatalytic pollutant degradation, such as the difficulty in recycling photocatalytic materials after water treatment, the low reuse rate of materials, and the low photocatalytic degradation efficiency. Therefore, it is of great significance to develop a method for preparing covalent organic framework fiber membranes for photocatalytic removal of antibiotics in water.

[0005] In view of this, the present invention is proposed to solve the above technical problems. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a preparation method of a covalent organic framework fiber membrane and its application in catalytic degradation of antibiotics. The preparation method of the covalent organic framework fiber membrane is simple and easy, and the equipment used is cheap and simple. It can achieve large-scale sewage treatment and is suitable for industrial development. Multiple uses greatly save costs and improve degradation efficiency. In addition, the present invention focuses on practical application scenarios, explores the degradation of antibiotic pollutants in water under natural sunlight, and optimizes the conditions of the photocatalytic system.

[0007] The present invention provides a method for preparing a covalent organic framework fiber membrane, comprising the following steps: (1) The organic ligand containing an aldehyde terminal group and the organic ligand containing a cyano terminal group are fully mixed, and o-dichlorobenzene, n-butanol and 1,8-diazacyclo[5,4,0]undecene-7 aqueous solution are added to mix, and the mixed solution is vacuum frozen and degassed for 3 times and then sealed in a bottle to undergo a Knoevenagel condensation reaction to obtain a functional COF photocatalyst; (2) The functional COF photocatalyst is uniformly dispersed in the casting agent and the organic solvent, and stirred at a speed of 400-600 r / min until the solution is uniform and free of particles, to obtain a spinning solution and use it for electrospinning. After the electrospinning is completed, it is dried to obtain a covalent organic framework fiber membrane; The casting agent is one of polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF); the organic ligand containing an aldehyde terminal group is one of 1,3,6,8-tetrakis(4-formylphenyl)pyrene, 5,5',5'',5'''-(pyrene-1,3,6,8-tetraphenyl)tetrapyridine aldehyde and N,N,N',N'-tetrakis(4-formylphenyl)-1,4-phenylenediamine; the organic ligand containing a cyano terminal group is one of 2,2-bipyridine-5,5-dicarbonitrile, terephthalonitrile and 4,4'-biphenyl dicarbonitrile.

[0008] Furthermore, in the spinning solution, the concentration of the functional COF photocatalyst is 5-15 wt%, and the concentration of the casting agent is 10-20 wt%.

[0009] Furthermore, the molar ratio of the organic ligand containing an aldehyde terminal group to the organic ligand containing a cyano terminal group is (1-3): (2-4).

[0010] Furthermore, the concentration of the 1,8-diazacyclo[5,4,0]undecene-7 aqueous solution is 1-5 mol / L, and the volume ratio of o-dichlorobenzene, n-butanol and the 1,8-diazacyclo[5,4,0]undecene-7 aqueous solution is (0.5-2):(0.5-2):(0.1-0.5).

[0011] Furthermore, the organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide and acetone.

[0012] Furthermore, the parameters of the electrospinning are high voltage 15-25 kV, low voltage 0.25 kV; roller receiving distance 30 cm, receiving speed 80-100 r / min; injection speed 0.2-0.5 mL / min; electrospinning machine translation speed 500 mm / min; during electrospinning, air humidity is controlled at 50-65%; 5-10 mL of spinning solution is used for each spinning; the drying temperature after the electrospinning is 60-70°C.

[0013] The present invention proposes the application of covalent organic framework fiber membrane in catalytic degradation of antibiotics. An aqueous solution containing antibiotic pollutants is added to a reaction pool, the covalent organic framework fiber membrane is fixed in the reaction pool, and a photocatalytic reaction is carried out under light conditions. During the reaction, samples are taken from the reaction pool to monitor the residual concentration of the pollutants.

[0014] Furthermore, the antibiotic is one or more of sulfamethoxazole, levofloxacin, norfloxacin, and tetracycline.

[0015] Furthermore, the lighting conditions are natural sunlight, 1000 W / m 2 , one of a xenon lamp and an LED lamp with λ>420 nm, wherein the photocatalytic reaction does not add any additional oxidant and only utilizes dissolved oxygen in the water body.

[0016] Furthermore, before the photocatalytic reaction, the adsorption process was carried out under light-free conditions for 15-30 min.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses an organic ligand containing an aldehyde terminal group and an organic ligand containing a cyano terminal group to carry out a Knoevenagel condensation reaction to prepare a functional COF photocatalyst, which is then mixed with a casting agent and an organic solvent to obtain a spinning solution, and finally electrospinning is performed to obtain a covalent organic framework fiber membrane with a flexible and adjustable structure and high photocatalytic efficiency, which is used for photocatalytic degradation of antibiotic pollutants, thereby improving the degradation efficiency of antibiotic pollutants and increasing the number of reuse times of the covalent organic framework fiber membrane.

[0018] 2. The present invention can regulate the structure and properties of COF materials by selecting different types of organic ligands. The organic ligands in the COF material contain a π conjugated system, which can absorb light of a specific wavelength and excite electrons to jump from the valence band to the conduction band to form electron-hole pairs. At the same time, the COF material has a highly ordered porous structure, which provides a large number of active sites, increases the contact area between light and the material, and improves the light absorption efficiency. The prepared nanofiber membrane has good mechanical strength, is easy to recover from water bodies, and is suitable for large-scale applications.

[0019] 3. The covalent organic framework fiber membrane of the present invention is universal for the treatment of antibiotic pollution in water bodies. It can also achieve good antibiotic degradation efficiency under natural light conditions and has good degradation effects on different typical and commonly used antibiotics. At the same time, the fiber membrane has good chemical stability and no risk of leaching in water bodies. There is no need to add other oxidants. It only uses dissolved oxygen in water and there is no secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure shows the degradation effect of the covalent organic framework fiber membrane of the present invention on different antibiotic pollutants.

[0021] Figure 2 This is the tetracycline degradation effect of the covalent organic framework fiber membrane of the present invention after repeated use.

[0022] Figure 3 This is a SEM image of the functional COF photocatalyst of Example 1 of the present invention.

[0023] Figure 4 This is a SEM image of the covalent organic framework fiber membrane of Example 1 of the present invention.

[0024] Figure 5 This is a graph showing the time variation of the water contact angle of the covalent organic framework fiber membrane of Example 1 of the present invention.

[0025] Figure 6 This is a graph showing the time variation of the water contact angle of the covalent organic framework fiber membrane of Example 3 of the present invention.

[0026] Figure 7 This is a graph showing the degradation activity of the covalent organic framework fiber membrane of Examples 1-3 of the present invention toward tetracycline. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The present invention provides a method for preparing a covalent organic framework fiber membrane and an application of the same in catalyzing the degradation of antibiotics, which are described in detail below.

[0029] The present invention provides a method for preparing a covalent organic framework fiber membrane, including the preparation of a functional COF photocatalyst (hereinafter referred to as COF photocatalyst) and an electrospinning covalent organic framework fiber membrane (hereinafter referred to as nanofiber membrane or COF nanofiber membrane), comprising the following steps: (a) Preparation of functional COF photocatalyst: Weigh the aldehyde organic ligand 1,3,6,8-tetrakis(4-formylphenyl)pyrene and the cyano organic ligand 2,2-bipyridine-5,5-dicarbonitrile in a glass bottle, add the organic solvents o-dichlorobenzene and n-butanol, and fully ultrasonicate to make them uniformly dispersed. After ultrasonic treatment, add an alkaline solution to catalyze the reaction process. The glass bottle is vacuum frozen and degassed by three liquid nitrogen freeze-thaws to prevent the formation of other by-products caused by excessive oxidation reactions. The sealed glass bottle is placed in an oven for Knoevenagel condensation reaction. After the reaction is completed, the solid product is filtered and washed with tetrahydrofuran until the washing liquid is colorless, and then dried to obtain the functional COF photocatalyst.

[0030] The ratio of 1,3,6,8-tetrakis(4-formylphenyl)pyrene, 2,2-bipyridine-5,5-dicarbonitrile, o-dichlorobenzene, n-butanol and alkaline solution is 29.6 mg: 23 mg: 1 mL: 1 mL: 0.2 mL. The alkaline solution is a potassium hydroxide solution and an aqueous solution of 1,8-diazacyclo[5,4,0]undecene-7. The ultrasonic time is 5-10 min, the condensation reaction temperature is 120 °C, and the reaction time is 72 h. The product drying temperature is 60 °C and the drying time is 2 h.

[0031] (b) Electrospinning covalent organic framework fiber membrane: The functional COF photocatalyst is stirred and evenly mixed with a casting agent and an organic solvent, and the obtained uniform spinning solution is used for electrospinning. After the electrospinning is completed, the covalent organic framework fiber membrane is obtained by drying.

[0032] The casting agent is one of polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF), and the organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide and acetone. The concentration of COF photocatalyst is 5-15wt%, and the concentration of casting agent is 10-20 wt%. The stirring speed is 400-600 r / min. The parameters of electrospinning are high voltage 15-25 kV and low voltage 0.25 kV. The roller receiving distance is 30 cm, and the receiving speed is 80-100 r / min. The injection speed is 0.2-0.5 mL / min. The translation speed of the electrospinning machine is 500 mm / min. During electrospinning, the air humidity is controlled at 50-65%. The spinning solution required for each spinning is 5-10mL. The drying temperature of the nanofiber membrane is 60-70 ℃, and the drying time is 2 h.

[0033] The covalent organic framework fiber membrane prepared by the present invention shows outstanding efficiency in the degradation of antibiotic pollution. The specific steps are as follows: adding an aqueous solution containing antibiotic pollutants into a reaction pool, fixing the covalent organic framework fiber membrane in the reaction pool, and taking samples from the reaction pool at certain time intervals under light conditions to detect the residual concentration of the pollutants.

[0034] The initial concentration of antibiotic contaminants was 10-20 ppm. The antibiotic was one of sulfamethoxazole, levofloxacin, norfloxacin, and tetracycline. The lighting conditions were natural sunlight, 1000 W / m 2 , a xenon lamp with λ>420 nm, or a LED lamp. The sampling time is 0, 2, 5, 10, 15, 30, 45, and 60 min. It should be noted that no additional oxidant is required during the photocatalytic reaction.

[0035] Example 1: This example is an exemplary method for preparing a covalent organic framework fiber membrane, which includes: 29.6 mg of 1,3,6,8-tetrakis(4-formylphenyl)pyrene and 23 mg of 2,2-bipyridine-5,5-dicarbonitrile were weighed and placed in a glass bottle, 1 mL of o-dichlorobenzene and 1 mL of n-butanol were added, and ultrasonic treatment was performed for 5 min to make them evenly dispersed. After ultrasonic treatment, 0.2 mL of 5 mol / L 1,8-diazacyclo[5,4,0]undecene-7 aqueous solution was added to catalyze the reaction. The glass bottle was vacuum frozen and degassed by three liquid nitrogen freeze-thaws to prevent excessive oxidation reactions from causing the formation of other by-products. The sealed glass bottle was placed in an oven at 120 °C for 72 h. In the oven, 1,3,6,8-tetrakis(4-formylphenyl)pyrene and 2,2-bipyridine-5,5-dicarbonitrile formed a covalent organic framework through the Knoevenagel condensation reaction. After the reaction, the solid product in the glass bottle was obtained by suction filtration, washed with tetrahydrofuran until the washing liquid was colorless, and dried in an oven at 60 °C to obtain a COF photocatalyst, recorded as COF-1. 5 wt% of COF photocatalyst and 12 wt% of polyacrylonitrile were added to a beaker, and then 20 mL of N,N-dimethylformamide was added, and stirred at 400 r / min for 12 h to make the spinning solution evenly dispersed. After that, electrospinning was carried out, and the high voltage was set to 25 KV and the low voltage was set to 0.25 kV; the roller receiving distance was 30 cm, the receiving speed was 80 r / min; the injection speed was 0.2 mL / min; and the translation speed was 0.5 cm / min. During electrospinning, the air humidity was controlled at 50-65%. 10 mL of spinning solution was extracted to obtain 24*32 cm 2 After spinning, the fiber membrane was dried in an oven at 60 °C for 2 h and was recorded as PAN / COF-1.

[0036] Photocatalytic degradation experiment of tetracycline in water by covalent organic framework fiber membrane: 11*11 cm fiber membrane was cut and fixed in an acrylic reaction tank. 100 mL of 10 ppm tetracycline solution was added to the reaction tank. 2, under the irradiation of a xenon lamp with λ>420nm, 1 mL of sample was taken from the reaction pool after 0, 2, 5, 10, 15, 30, 45, and 60 min, and the residual tetracycline concentration was detected by high performance liquid chromatography.

[0037] Example 2: This example is another exemplary method for preparing a covalent organic framework fiber membrane. The difference from Example 1 is that the added ligand is different, which includes: 29.8 mg of 5,5',5'',5'''-(pyrene-1,3,6,8-tetraphenyl) tetrapyridine aldehyde and 22.8 mg of 4,4'-biphenyl dinitrile were weighed and placed in a glass bottle, 1 mL of o-dichlorobenzene and 1 mL of n-butanol were added, and ultrasonic treatment was performed for 5 min to make them uniformly dispersed. After ultrasonic treatment, 0.2 mL of 5 mol / L 1,8-diazacyclo[5,4,0]undecene-7 aqueous solution was added to catalyze the reaction. The glass bottle was vacuum frozen and degassed by three liquid nitrogen freeze-thaws to prevent excessive oxidation reactions from causing the formation of other by-products. The sealed glass bottle was placed in an oven at 120 °C for 72 h to form a covalent organic framework through the Knoevenagel condensation reaction. After the reaction, the solid product in the glass bottle was obtained by suction filtration, washed with tetrahydrofuran until the washing liquid was colorless, and placed in an oven at 60 °C to dry to obtain a COF photocatalyst, which was recorded as COF-2. 5 wt% COF photocatalyst and 12 wt% polyacrylonitrile were added to a beaker, and then 20 mL of N,N-dimethylformamide was added. The mixture was stirred at 400 r / min for 12 h to make the spinning solution evenly dispersed. Then, electrospinning was performed, with the high voltage set to 25 KV and the low voltage set to 0.25 kV; the roller receiving distance was 30 cm, the receiving speed was 80 r / min; the injection speed was 0.2 mL / min; and the translation speed was 0.5 cm / min. During electrospinning, the air humidity was controlled at 50-65%. 10 mL of spinning solution was extracted to obtain 24*32 cm 2 After spinning, the fiber membrane was dried in an oven at 60 °C for 2 h and was recorded as PAN / COF-2.

[0038] Photocatalytic degradation experiment of tetracycline in water by covalent organic framework fiber membrane: 11*11 cm fiber membrane was cut and fixed in an acrylic reaction tank. 100 mL of 10 ppm tetracycline solution was added to the reaction tank. 2 , under the irradiation of a xenon lamp with λ>420nm, 1 mL of sample was taken from the reaction pool after 0, 2, 5, 10, 15, 30, 45, and 60 min, and the residual tetracycline concentration was detected by high performance liquid chromatography.

[0039] Example 3: This example is another exemplary method for preparing a covalent organic framework fiber membrane. The difference from Example 1 is that the casting agent used is different, which includes: 29.8 mg of 5,5',5'',5'''-(pyrene-1,3,6,8-tetraphenyl) tetrapyridine aldehyde and 22.8 mg of 4,4'-biphenyl dinitrile were weighed and placed in a glass bottle, 1 mL of o-dichlorobenzene and 1 mL of n-butanol were added, and ultrasonic treatment was performed for 5 min to make them uniformly dispersed. After ultrasonic treatment, 0.2 mL of 5 mol / L 1,8-diazacyclo[5,4,0]undecene-7 aqueous solution was added to catalyze the reaction. The glass bottle was vacuum frozen and degassed by three liquid nitrogen freeze-thaws to prevent excessive oxidation reactions from causing the formation of other by-products. The sealed glass bottle was placed in an oven at 120 °C for 72 h to form a covalent organic framework through the Knoevenagel condensation reaction. After the reaction, the solid product in the glass bottle was obtained by suction filtration, washed with tetrahydrofuran until the washing liquid was colorless, and dried in an oven at 60 °C to obtain a COF photocatalyst, which was recorded as COF-1. 5 wt% COF photocatalyst and 12 wt% polyvinylidene fluoride were added to a beaker, and then 20 mL of N,N-diethylacetamide was added. The mixture was stirred at 400 r / min for 12 hours to make the spinning solution evenly dispersed. Then, electrospinning was performed, with the high voltage set to 25 KV and the low voltage set to 0.25 kV; the roller receiving distance was 30 cm, the receiving speed was 80 r / min; the injection speed was 0.2 mL / min; and the translation speed was 0.5 cm / min. During electrospinning, the air humidity was controlled at 50-65%. 10 mL of spinning solution was extracted to obtain 24*32 cm 2 After spinning, the fiber membrane was dried in an oven at 60 °C for 2 h and was recorded as PVDF / COF-1.

[0040] Photocatalytic degradation experiment of tetracycline in water by covalent organic framework fiber membrane: 11*11 cm fiber membrane was cut and fixed in an acrylic reaction tank. 100 mL of 10 ppm tetracycline solution was added to the reaction tank. 2 , under the irradiation of a xenon lamp with λ>420nm, 1 mL of sample was taken from the reaction pool after 0, 2, 5, 10, 15, 30, 45, and 60 min, and the residual tetracycline concentration was detected by high performance liquid chromatography.

[0041] like Figure 3 As shown, it can be clearly observed that the COF photocatalyst prepared in Example 1 is a rod-like structure with a complete morphology and high crystallinity. Figure 4 As shown, the fiber structure of the membrane can be clearly observed, and there is no bulk material structure on the surface of the covalent organic framework fiber membrane of Example 1, indicating that COF is evenly dispersed in the nanofiber membrane.

[0042] like Figure 5 As shown, it can be seen that the COF nanofiber membrane of Example 1 completely absorbs the water droplets within 200 ms, indicating that it has good water absorption performance and provides convenient conditions for full contact and reaction with antibiotic wastewater.

[0043] Figure 6 This is a graph showing the change in water contact angle of the covalent organic framework fiber membrane of Example 3. As time goes by, PVDF / COF-1 hardly absorbs water, indicating that the nanofiber membrane is highly hydrophobic, which may be related to its low photocatalytic efficiency.

[0044] Figure 7 3 is a graph showing the degradation activity of the covalent organic framework fiber membranes of Examples 1-3 for tetracycline, wherein the covalent organic framework fiber membrane in Example 1 has good degradation activity for tetracycline and achieves complete removal within 10 minutes.

[0045] Verification Example 1: Degradation effect on different antibiotic pollutants; Tetracycline (TC), levofloxacin (LVX), acid orange 7 (AO7), and phenol (Phenol) of the same concentration were used as antibiotic pollutants, respectively. The covalent organic framework fiber membrane of Example 1 was used to carry out covalent organic framework fiber membrane-catalyzed degradation of antibiotics with reference to Example 1. Samples were taken from each reaction pool at different time points to detect the residual concentrations of different antibiotic pollutants.

[0046] from Figure 1 It can be seen that the covalent organic framework fiber membrane of Example 1 has a good degradation effect on several different typical commonly used antibiotics, indicating that the covalent organic framework fiber membrane of the present invention is universal in the treatment of antibiotic pollution in water bodies.

[0047] Verification Example 2: Tetracycline degradation effect after repeated use; Tetracycline (TC) was used as the antibiotic pollutant. The covalent organic framework fiber membrane of Example 1 was used. Under the condition of natural light, the covalent organic framework fiber membrane was used to catalyze the degradation of antibiotics with reference to Example 1. The covalent organic framework fiber membrane was regenerated after each use and used again in the tetracycline degradation experiment. The degradation efficiency after repeated use was recorded.

[0048] from Figure 2 It can be seen that the tetracycline removal rate of the covalent organic framework fiber membrane of Example 1 reaches 100% within 90 min, and a good antibiotic degradation efficiency can be achieved under natural light conditions. In the continuous flow reaction, the covalent organic framework fiber membrane of the present invention can treat 60 L·m of antibiotic wastewater. -2 ·day -1 , providing support for practical industrial applications.

[0049] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing a covalent organic framework fiber membrane, characterized in that: The following steps are involved: (1) The organic ligand containing an aldehyde terminal group and the organic ligand containing a cyano terminal group are fully mixed, and o-dichlorobenzene, n-butanol and 1,8-diazacyclo[5,4,0]undecene-7 aqueous solution are added to mix, and the mixed solution is vacuum frozen and degassed for 3 times and then sealed in a bottle to undergo a Knoevenagel condensation reaction to obtain a functional COF photocatalyst; (2) The functional COF photocatalyst is uniformly dispersed in the casting agent and the organic solvent, and stirred at a speed of 400-600 r / min until the solution is uniform and free of particles, to obtain a spinning solution and use it for electrospinning. After the electrospinning is completed, it is dried to obtain a covalent organic framework fiber membrane; The casting agent is one of polyacrylonitrile and polyvinylidene fluoride; the organic ligand containing an aldehyde terminal group is one of 1,3,6,8-tetrakis(4-formylphenyl)pyrene, 5,5',5'',5'''-(pyrene-1,3,6,8-tetraphenyl)tetrapyridine aldehyde and N,N,N',N'-tetrakis(4-formylphenyl)-1,4-phenylenediamine; the organic ligand containing a cyano terminal group is one of 2,2-bipyridine-5,5-dicarbonitrile, terephthalonitrile and 4,4'-biphenyl dicarbonitrile.

2. The method for preparing the covalent organic framework fiber membrane according to claim 1, characterized in that: In the spinning solution, the concentration of the functional COF photocatalyst is 5-15 wt %, and the concentration of the casting agent is 10-20 wt %.

3. The method for preparing the covalent organic framework fiber membrane according to claim 1, characterized in that: The molar ratio of the organic ligand containing an aldehyde terminal group to the organic ligand containing a cyano terminal group is (1-3): (2-4).

4. The method for preparing a covalent organic framework fiber membrane according to claim 1, characterized in that: The concentration of the 1,8-diazacyclo[5,4,0]undecene-7 aqueous solution is 1-5 mol / L, and the volume ratio of o-dichlorobenzene, n-butanol and the 1,8-diazacyclo[5,4,0]undecene-7 aqueous solution is (0.5-2):(0.5-2):(0.1-0.5).

5. The method for preparing the covalent organic framework fiber membrane according to claim 1, characterized in that: The organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide and acetone.

6. The preparation of the covalent organic framework fiber membrane according to claim 1, characterized in that: The parameters of the electrospinning are high voltage 15-25 kV, low voltage 0.25 kV; roller receiving distance 30 cm, receiving speed 80-100 r / min; injection speed 0.2-0.5 mL / min; electrospinning machine translation speed 500 mm / min; during electrospinning, air humidity is controlled at 50-65%; 5-10 mL of spinning solution is used for each spinning; and the drying temperature after the electrospinning is 60-70°C.

7. Application of the covalent organic framework fiber membrane prepared by the preparation method according to any one of claims 1 to 6 for catalytic degradation of antibiotics, characterized in that: An aqueous solution containing antibiotic pollutants is added to the reaction pool, the covalent organic framework fiber membrane is fixed in the reaction pool, and a photocatalytic reaction is carried out under light conditions. During the reaction, samples are taken from the reaction pool to monitor the residual concentration of the pollutants.

8. The use of the covalent organic framework fiber membrane for catalytic degradation of antibiotics according to claim 7, characterized in that: The antibiotic is one or more of sulfamethoxazole, levofloxacin, norfloxacin and tetracycline.

9. The use of the covalent organic framework fiber membrane for catalytic degradation of antibiotics according to claim 7, characterized in that: The lighting conditions are natural sunlight, 1000 W / m 2 , one of a xenon lamp and an LED lamp with λ> 420 nm, wherein the photocatalytic reaction does not add any additional oxidant and only utilizes dissolved oxygen in the water body.

10. The use of the covalent organic framework fiber membrane for catalytic degradation of antibiotics according to claim 7, characterized in that: Before the photocatalytic reaction, the adsorption process was carried out under light-free conditions for 15-30 min.

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