Aromatic biguanide covalent organic framework material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of photocatalytic materials, and discloses an aromatic biguanide covalent organic framework material which is obtained by carrying out C-N coupling reaction on an organic framework material containing halogen atoms and an aromatic biguanide compound, wherein the molar ratio of the organic framework material containing halogen atoms to the aromatic biguanide compound is 1: (7.5-15). The covalent organic framework material rich in aromatic biguanidyl is constructed by adopting side chain engineering, drug micropollutants in a water body can be efficiently catalyzed under the irradiation of visible light, meanwhile, in-situ photocatalytic self-cleaning is realized, a degradation product can be effectively separated from pore channels and surfaces of the aromatic biguanidyl covalent organic framework material, active sites are released, and the photocatalytic self-cleaning effect is achieved. The steps of organic solvent elution and the like are avoided, and a certain reference effect is provided for design and development of efficient green photocatalysts.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalytic materials, and in particular to an aromatic biguanide-based covalent organic framework material and a preparation method and application thereof. Background Art

[0002] In recent years, the negative impact of exposure to emerging drug micropollutants on the ecological environment and human health has attracted widespread attention. Drug pollution represented by receptor blockers such as propranolol, antibiotics such as sulfamethoxazole, antihistamines such as loratadine, and antidepressants such as amitriptyline is frequent worldwide. Therefore, how to reduce the impact of micropollutants on the environment is a global problem that needs to be solved urgently. Compared with adsorption, membrane separation, biodegradation, electrochemistry and other technologies, photocatalysis has the advantages of directly utilizing solar energy, completely removing pollutants, and reducing secondary pollution. It has great potential in environmental remediation. Developing efficient and green catalysts combined with solar natural energy to degrade and mineralize pollutants in water is one of the ideal ways to solve water pollution.

[0003] As a nitrogen-rich organic strong base, biguanide is in a protonated state within a wide pH range. Its electron-rich conjugated structure has excellent performance in catalyzing organic reactions. However, due to its high polarity, it faces separation and purification difficulties in practical applications. Therefore, how to provide a photocatalytic material containing aromatic biguanide compounds that is easy to separate and recycle to efficiently catalyze the degradation of drug micropollutants is an urgent problem that technicians in this field need to solve. Summary of the invention

[0004] In view of this, the present invention provides an aromatic biguanide covalent organic framework material (Aryl-BIG-COF), in which aromatic biguanide compounds are embedded in the covalent organic framework material to prepare a heterogeneous catalyst. The catalyst is easy to recover and can also give full play to the application potential of aromatic biguanide compounds in water bodies. It can efficiently catalyze the degradation of pharmaceutical micropollutants in water bodies under visible light irradiation.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] On the one hand, the present invention provides an aromatic biguanide-based covalent organic framework material, which is obtained by a CN coupling reaction between an organic framework material containing a halogen atom and an aromatic biguanide compound;

[0007] Wherein, the molar ratio of the organic framework material containing halogen atoms to the aromatic biguanide compound is 1:7.5-15.

[0008] Preferably, the organic framework material containing halogen atoms is prepared from monomers containing halogen atoms and amino monomers by a solvothermal method.

[0009] Preferably, the halogen atom includes one or more of a bromine atom, a chlorine atom, and a fluorine atom.

[0010] Preferably, the aromatic biguanide compound includes one or more of metformin, phenformin, and 1,6-di-(N5-substituted phenyl-N1-biguanide) hexane hydrochloride.

[0011] On the other hand, the present invention also provides a method for preparing the aromatic biguanide-based covalent organic framework material described in any one of the above, comprising the following steps:

[0012] (1) mixing an organic framework material containing a halogen atom, an aromatic biguanide compound, a synthetic solvent and a catalyst and reacting the mixture to obtain an intermediate product;

[0013] (2) Drying the intermediate product to obtain an aromatic biguanide-based covalent organic framework material.

[0014] Preferably, the ratio of the total mass of the organic framework material containing halogen atoms and the aromatic biguanide compound to the mass of the synthesis solvent is 1:40-60.

[0015] Preferably, the synthetic solvent includes one or more of dimethyl sulfoxide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0016] Preferably, the catalyst comprises CuI and K 2 CO 3 .

[0017] Preferably, the molar ratio of the organic framework material containing halogen atoms to CuI is 1:1-2.

[0018] Preferably, the organic framework material containing halogen atoms and K 2 CO 3 The molar ratio is 1:20-30.

[0019] Preferably, the reaction temperature in step (1) is 100-130° C., and the reaction time is 36-48 h.

[0020] Preferably, the drying is freeze drying, and the freeze drying temperature is -40°C and the time is 12-24 hours.

[0021] Preferably, before the drying, the method further comprises: washing the intermediate product.

[0022] Preferably, the solvent used for the washing is at least one of tetrahydrofuran and acetone.

[0023] Furthermore, the present invention also provides an application of the aromatic biguanide-based covalent organic framework material described in any one of the above items or the aromatic biguanide-based covalent organic framework material prepared by any one of the above preparation methods in photocatalytic degradation of pharmaceutical micropollutants.

[0024] The present invention provides an aromatic biguanide-based covalent organic framework material, which has the following beneficial effects compared with the prior art:

[0025] The present invention adopts side chain engineering to construct a covalent organic framework material rich in aromatic biguanide groups, which can efficiently catalyze drug micropollutants in water under visible light irradiation, and realize in-situ photocatalytic self-cleaning. The degradation products can effectively detach from the pores and surface of the aromatic biguanide covalent organic framework material, release the active sites, and avoid the steps of organic solvent elution, which has a certain reference role in the design and development of efficient green photocatalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0027] Figure 1 is a SEM image of Br-COF prepared in Example 1;

[0028] Figure 2 is a SEM image of Aryl-BIG-COF prepared in Example 1;

[0029] Figure 3 is the FTIR graph of Br-COF and Aryl-BIG-COF prepared in Example 1;

[0030] Figure 4 is a schematic diagram of photocatalytic degradation of propranolol by Br-COF and Aryl-BIG-COF in Application Example 1;

[0031] Figure 5 is a schematic diagram of the cycle of photocatalytic degradation of propranolol by Aryl-BIG-COF in Application Example 1;

[0032] Figure 6 is the XRD pattern of Br-COF and Aryl-BIG-COF prepared in Example 1;

[0033] Figure 7 This is the XPS graph of Aryl-BIG-COF prepared in Example 1. DETAILED DESCRIPTION

[0034] The present invention will be described below by specific examples, and it will be appreciated by those skilled in the art that the following specific examples are only for illustrative purposes, and do not limit the scope of the present invention in any way. In addition, in the following examples, unless otherwise specified, the reagents and equipment used are all commercially available. If in the following examples, specific treatment conditions and treatment methods are not clearly described, then conditions and methods known in the art can be used to process.

[0035] In one aspect of the present invention, the present invention provides an aromatic biguanide-based covalent organic framework material, which is obtained by a CN coupling reaction of an organic framework material containing halogen atoms and an aromatic biguanide compound in the presence of a cuprous iodide catalyst.

[0036] During the research process, it was found that the orientation of guanidine compounds is difficult to control. If they are directly reacted as monomers, it will lead to insufficient specific surface area and crystallinity of COFs. This side chain engineering can introduce functional groups while maintaining the high crystallinity and high specific surface area of ​​the original COF.

[0037] In the present invention, the molar ratio of the organic framework material containing halogen atoms to the aromatic biguanide compound is 1:7.5-15, for example, it can be 1:7.5, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, etc. By limiting the ratio of the organic framework material containing halogen atoms to the aromatic biguanide compound, the functional group abundance and morphological pore size of the aromatic biguanide-based covalent organic framework material can be regulated, and the specific ratio is proportional to the functional group abundance and inversely proportional to the pore size.

[0038] In the present invention, the organic framework material containing halogen atoms is prepared from monomers containing halogen atoms and amino monomers by a solvent thermal method; the halogen atoms include one or more of bromine atoms, chlorine atoms, and fluorine atoms.

[0039] In some embodiments of the present invention, the organic framework material containing halogen atoms is an organic framework material containing bromine atoms (Br-COF), and the process of preparing it by the solvothermal method is as follows: 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dibromoterephthalaldehyde are subjected to a condensation reaction by Schiff base to obtain Br-COF. The molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 2,5-dibromoterephthalaldehyde is 7:8.6, the reaction temperature is 100-150°C, and the reaction time is 72-96h.

[0040] The aromatic biguanide compounds include one or more of metformin, phenformin, and 1,6-di-(N5-substituted phenyl-N1-biguanide) hexane hydrochloride, for example, 1,4-phenylbiguanide, phenylbiguanide, phenethylbiguanide, and the like.

[0041] In another aspect of the present invention, the present invention provides a method for preparing an aromatic biguanide-based covalent organic framework material, comprising the following steps:

[0042] Step S100: mixing an organic framework material containing halogen atoms, an aromatic biguanide compound, a synthesis solvent and a catalyst, and reacting the mixture to obtain an intermediate product.

[0043] In this step, the selection of the organic framework material containing halogen atoms, the aromatic biguanide compound, and the synthetic solvent and the relationship between the addition amounts thereof have been described in detail in the above content and will not be repeated here.

[0044] In the present invention, the total mass ratio of the organic framework material containing halogen atoms and the aromatic biguanide compound to the mass ratio of the synthetic solvent is 1:40-60, for example, 1:40, 1:45, 1:50, 1:55, 1:60, etc. By limiting the ratio of the synthetic solvent to the raw material,

[0045] In the present invention, the synthesis solvent includes one or more of dimethyl sulfoxide, N,N-dimethylacetamide, and N-methylpyrrolidone, preferably dimethyl sulfoxide. By adding the synthesis solvent, the reaction can be more complete and the yield of the aromatic biguanide-based covalent organic framework material can be increased.

[0046] In the present invention, the catalyst comprises CuI and K 2 CO 3 The molar ratio of the organic framework material containing halogen atoms to CuI is 1:1-2, for example, 1:1, 1:1.5, 1:2, etc.; the organic framework material containing halogen atoms to K 2 CO 3 The molar ratio is 1:20-30, for example, 1:20, 1:25, 1:30, etc. Potassium carbonate is used as an acid binding agent and cuprous iodide is used as a catalyst. If the amount of potassium carbonate added is too large, the structure of the organic framework material containing halogen atoms will be destroyed.

[0047] In the present invention, the reaction is a reflux reaction, the reaction temperature is 100-130°C, for example, 100°C, 110°C, 120°C, 130°C, etc.; the reaction time is 36-48h, for example, 36h, 38h, 40h, 42h, 44h, 46h, 48h, etc. By heating the reflux reaction, the organic framework material containing halogen atoms and the aromatic biguanide compound can be promoted to undergo a sufficient CN coupling reaction.

[0048] In some embodiments of the present invention, the aromatic biguanide compound is 1,4-phenylenediguanide, and the preparation method thereof is as follows: phenylenediamine and dicyandiamide are heated to reflux in a hydrochloric acid solution, and after the reaction is completed, rotary evaporation is performed, and hot ethanol is used for grinding and filtering to obtain lavender powder 1,4-phenylenediguanide. The molar ratio of phenylenediamine to dicyandiamide is 1:2, the concentration of the hydrochloric acid solution is 1-3 mol / L, the molar ratio of the sum of the added amounts of phenylenediamine and dicyandiamide to the added amount of hydrochloric acid is 1:6-8, the heating reflux temperature is 100°C, and the time is 3h.

[0049] It should be noted that the above specific embodiment of the present invention is only an example of an organic framework material and an aromatic biguanide compound containing halogen atoms, and the organic framework material and the aromatic biguanide compound containing halogen atoms in the present invention are not limited to Br-COF and 1,4-phenylenediguanide, respectively. In addition, the organic framework material and the aromatic biguanide compound containing halogen atoms can be prepared by themselves according to conventional methods or purchased on the market.

[0050] Step S200: Cool the intermediate product, filter it under reduced pressure, wash it, and dry it to obtain an aromatic biguanide-based covalent organic framework material.

[0051] In this step, the cooling is natural cooling to room temperature, the decompression is vacuum filtration, and the filtration is solid-liquid separation. There is no special limitation on the specific filtration method.

[0052] In the present invention, the washing is performed by using one or more of tetrahydrofuran, acetone, water, ethanol, etc., and the number of washings is 2-8 times, preferably 4-8 times, for example, 4 times, 5 times, 6 times, 7 times, 8 times. By washing, impurities in the precipitate obtained after solid-liquid separation can be removed, thereby improving the purity of the product.

[0053] In the present invention, the drying is freeze drying, the freeze drying temperature is -40°C, and the time is 12-24 hours, for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc. It should be noted that in this process, small fluctuations in vacuum degree and freeze drying temperature will basically not affect the drying effect, and can be appropriately adjusted according to conventional operations.

[0054] Furthermore, the present invention also provides an application of an aromatic biguanide-based covalent organic framework material as described in any one of the above items or an aromatic biguanide-based covalent organic framework material prepared by any one of the above preparation methods in photocatalytic degradation of pharmaceutical micropollutants, wherein the pharmaceutical micropollutants may be one or more of propranolol, bisphenol A, norfloxacin, tetracycline, etc.

[0055] The technical solution of the present invention is described in detail below through specific embodiments.

[0056] Example 1

[0057] (1) Br-COF was synthesized by a hot solvent method through Schiff base condensation of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dibromoterephthalaldehyde; wherein the molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 2,5-dibromoterephthalaldehyde was 7:8.6, the reaction temperature was 120°C, and the reaction time was 72h;

[0058] (2) Phenylenediamine and dicyandiamide were heated to reflux at 100°C for 3 h in 50 mL 1 mol / L HCl at a molar ratio of 1:2. After the reaction was completed, the mixture was evaporated under reduced pressure to an oily state and then immediately added with hot ethanol and quickly ground until crystals precipitated. The mixture was filtered while hot, washed twice with ethanol, and then recrystallized with water-acetone to obtain a pale purple powder 1,4-phenylenediguanide;

[0059] (3) Br-COF and 1,4-phenylbiguanide were mixed in a molar ratio of 1:8 and added to 50 ml of dimethyl sulfoxide solvent. CuI and K 2 CO 3 , under nitrogen protection, reflux reaction at 110 ° C for 48 hours. After the reaction, it was cooled to room temperature and filtered under reduced pressure. The precipitate was washed three times with water and ethanol respectively, and freeze-dried at -40 ° C for 12 hours to obtain Aryl-BIG-COF; the molar ratio of Br-COF to CuI was 1:1.5, and the molar ratio of Br-COF to K 2 CO 3 The molar ratio is 1:25;

[0060] like Figure 1 , 2 3 are the SEM images of Br-COF and Aryl-BIG-COF prepared in this example, and the FTIR images of Br-COF and Aryl-BIG-COF, respectively.

[0061] Depend on Figure 1 and Figure 2Comparison shows that the SEM image of Aryl-BIG-COF obtained after the introduction of aromatic biguanide groups changes from the original fiber shape to a coral shape with tighter pores compared with Br-COF; Figure 3 1590cm in the FTIR spectrum of Br-COF -1 and 613cm- 1 The stretching vibration peaks of C=N and the bending vibration peaks of C-Br formed by the condensation of the aldehyde group of 2,5-dibromobenzene-1,4-dicarboxaldehyde and the amino group of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, respectively, the bending vibration peak of C-Br in the infrared spectrum of Aryl-BIG-COF disappears, and the peak at 3315 cm -1 、3185cm -1 and 1385cm -1 In the biguanide structure, -NH 2 The characteristic stretching vibration peaks of -NH-, -CN- prove that 1,4-phenylbiguanide successfully reacts with -Br in Br-COF and enters the COF framework in the form of a side chain.

[0062] Example 2

[0063] (1) Br-COF was synthesized by a hot solvent method from 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dibromoterephthalaldehyde via Schiff base condensation, wherein the molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 2,5-dibromoterephthalaldehyde was 7:8.6, the reaction temperature was 150°C, and the reaction time was 96 h;

[0064] (2) Phenylenediamine and dicyandiamide were heated to reflux at 100°C for 3 h in 50 mL 2 mol / L HCl at a molar ratio of 1:2. After the reaction was completed, the mixture was evaporated under reduced pressure to an oily state and then immediately added with hot ethanol and quickly ground until crystals precipitated. The mixture was filtered while hot, washed twice with ethanol, and then recrystallized with water-acetone to obtain lavender powder 1,4-phenylenediguanide;

[0065] (3) Br-COF and 1,4-phenylbiguanide were mixed in a molar ratio of 1:10 and added to 50 ml of dimethyl sulfoxide solvent. CuI and K 2 CO 3 , under nitrogen protection, reflux reaction at 110℃ for 48h. After the reaction, cool to room temperature and filter under reduced pressure. The precipitate is washed three times with water and ethanol respectively. After freeze-drying at -40℃ for 12h, Aryl-BIG-COF is obtained. The molar ratio of Br-COF to CuI is 1:1.5, and the molar ratio of Br-COF to K 2 CO 3 The molar ratio is 1:25.

[0066] Example 3

[0067] (1) Br-COF was synthesized by Schiff base condensation of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dibromoterephthalaldehyde using a hot solvent method, wherein the molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 2,5-dibromoterephthalaldehyde was 7:8.6, the reaction temperature was 150°C, and the reaction time was 96 h.

[0068] (2) Phenylenediamine and dicyandiamide were heated to reflux at 100°C for 3 h in 50 mL 2 mol / L HCl at a molar ratio of 1:2. After the reaction was completed, the mixture was evaporated under reduced pressure to an oily state and then immediately added with hot ethanol and quickly ground until crystals precipitated. The mixture was filtered while hot, washed twice with ethanol, and then recrystallized with water-acetone to obtain lavender powder 1,4-phenylenediguanide;

[0069] (3) Br-COF and 1,4-phenylbiguanide were mixed in a molar ratio of 1:15 and added to 50 ml of dimethyl sulfoxide solvent. CuI and K 2 CO 3 , under nitrogen protection, reflux reaction at 110℃ for 36h. After the reaction, cool to room temperature and filter under reduced pressure. The precipitate is washed three times with water and ethanol respectively. After freeze-drying at -40℃ for 24h, Aryl-BIG-COF is obtained. The molar ratio of Br-COF to CuI is 1:2, and the molar ratio of Br-COF to K 2 CO 3 The molar ratio is 1:25.

[0070] Example 4

[0071] Example 4 is basically the same as Example 1, except that Br-COF is replaced by Cl-COF. The preparation method of Cl-COF is as follows:

[0072] Cl-COF was synthesized by Schiff base condensation of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,5-dichloroterephthalaldehyde using a hot solvent method; wherein the molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to 2,5-dichloroterephthalaldehyde was 7:8.6, the reaction temperature was 120°C, and the reaction time was 72h.

[0073] Example 5

[0074] Example 5 is substantially the same as Example 1, except that 1,4-phenylenediguanide is replaced by phenethylbiguanide (purchased from the market).

[0075] Application Example 1

[0076] Photocatalytic experiment: The Br-COF and Aryl-BIG-COF prepared in Example 1 were respectively put into a constant temperature reaction system with a propranolol concentration of 20 ppm. The experimental system was first stirred in the dark for 30 minutes, and samples were taken every 5 minutes. After reaching the adsorption-desorption equilibrium, a 300 W xenon lamp was used as the light source, and the incident wavelength was 420-780 nm. Samples were taken every 5 minutes. After filtration, high performance liquid chromatography was used for sample injection and detection. The concentration change of propranolol during the adsorption and catalytic process was determined according to the standard curve established based on the series of standard solutions.

[0077] like Figure 4 As shown, it is a schematic diagram of the catalytic degradation of propranolol under visible light by Br-COF and Aryl-BIG-COF prepared in Example 1. It can be seen from the figure that under the action of Aryl-BIG-COF, propranolol is completely removed after 40 minutes of light catalysis, and the adsorption and catalytic performance are significantly enhanced compared with Br-COF, indicating that the embedding of aromatic biguanide groups realizes the effective adsorption and capture of propranolol molecules, and also realizes the effective absorption of visible light through electronic structure regulation, thereby improving the efficient catalytic degradation effect, which enables the pollutant molecules to be efficiently removed.

[0078] After the photocatalytic reaction of Aryl-BIG-COF was completed (one cycle was 1 h), high concentrations of pollutants were directly added to the reaction system before each cycle experiment began. The concentration of the pollutant substrate was adjusted to the starting concentration (20 ppm) and the next round of experiments was started with the same experimental conditions as before.

[0079] like Figure 5 As shown, the removal rate of propranolol after 6 in-situ cycle experiments of Aryl-BIG-COF prepared in Example 1 under visible light is shown. The results show that the overall removal rate of propranolol can still reach 90.4% after 6 cycles. This shows that Aryl-BIG-COF can achieve in-situ self-cleaning under visible light, and the degradation products can effectively detach from the pores and surface of Aryl-BIG-COF to release active sites. The reduction of interlayer spacing and pore size caused by the introduction of aromatic biguanide groups in the prepared Aryl-BIG-COF is conducive to the release of degradation products, avoiding steps such as organic solvent elution, and providing a certain reference for the design concept of green COF catalysts.

[0080] Application Example 2

[0081] The present invention conducts photocatalytic experiments on tetracycline, bisphenol A and norfloxacin, all of which have an initial concentration of 20 ppm, respectively, and the experimental conditions are the same as those in Application Example 1.

[0082] The experimental results showed that Aryl-BIG-COF removed 97.70% of tetracycline within 60 min, 97.36% of bisphenol A within 120 min, and 91.79% of norfloxacin within 150 min.

[0083] In summary, the present invention uses aromatic biguanide as a functional side chain and embeds it into a COF matrix to prepare a heterogeneous catalyst. The successful introduction of the aromatic biguanide side chain is confirmed by characterization methods such as XRD, FT-IR and XPS, and the high crystallinity of the original COF is maintained. The prepared photocatalytic material can efficiently remove drug micropollutants in water by fixed-point capture and enhanced catalysis under visible light. -1 At the dosage of 1.577 mg / g, compared with Br-COF, the adsorption capacity of propranolol on Aryl-BIG-COF increased from 6.89 mg / g to 31.68 mg / g, and the pseudo-first-order rate constant of photocatalytic degradation increased from 0.013 min -1 Improved to 0.089min -1 After 6 cycles of in-situ regeneration, the removal rate of drug micropollutants can still reach more than 90%, which means that while the active groups introduced by side chain engineering can enhance the directional capture of pollutant molecules, the electronic band structure of COFs can also be effectively regulated by regulating the transmission of electrons through the conjugated structure, thereby improving the separation efficiency of electrons and holes, and realizing the dual-function enhancement of COFs to efficiently remove pollutants.

[0084] The embodiments of the present invention have been shown and described above. It can be understood that the above embodiments are exemplary and cannot be construed as limitations on the present invention. A person skilled in the art can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. An aromatic biguanide-based covalent organic framework material, characterized in that: It is obtained by CN coupling reaction between organic framework materials containing halogen atoms and aromatic biguanide compounds; Wherein, the molar ratio of the organic framework material containing halogen atoms to the aromatic biguanide compound is 1:7.5-15.

2. The aromatic biguanide-based covalent organic framework material according to claim 1, characterized in that: The organic framework material containing halogen atoms is prepared from monomers containing halogen atoms and amino monomers by a solvothermal method; The halogen atom includes one or more of a bromine atom, a chlorine atom, and a fluorine atom.

3. The aromatic biguanide-based covalent organic framework material according to claim 1, characterized in that: The aromatic biguanide compound includes one or more of metformin, phenformin, and 1,6-di-(N5-substituted phenyl-N1-biguanide) hexane hydrochloride.

4. A method for preparing the aromatic biguanide-based covalent organic framework material according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) mixing an organic framework material containing a halogen atom, an aromatic biguanide compound, a synthetic solvent and a catalyst and reacting the mixture to obtain an intermediate product; (2) Drying the intermediate product to obtain an aromatic biguanide-based covalent organic framework material.

5. The method for preparing the aromatic biguanide-based covalent organic framework material according to claim 4, characterized in that: The ratio of the total mass of the organic framework material containing halogen atoms and the aromatic biguanide compound to the mass of the synthetic solvent is 1:40-60; The synthetic solvent includes one or more of dimethyl sulfoxide, N,N-dimethylacetamide and N-methylpyrrolidone.

6. The method for preparing the aromatic biguanide-based covalent organic framework material according to claim 4, characterized in that: The catalyst comprises CuI and K2CO3; The molar ratio of the organic framework material containing halogen atoms to CuI is 1:1-2, and the molar ratio of the organic framework material containing halogen atoms to K2CO3 is 1:20-30.

7. The method for preparing an aromatic biguanide-based covalent organic framework material according to claim 4, characterized in that: The reaction temperature in step (1) is 100-130° C., and the reaction time is 36-48 h.

8. The method for preparing an aromatic biguanide-based covalent organic framework material according to claim 4, characterized in that: The drying is freeze drying, the freeze drying temperature is -40°C, and the time is 12-24h.

9. The method for preparing an aromatic biguanide-based covalent organic framework material according to any one of claims 4 to 8, characterized in that: Before the drying, the intermediate product is also washed; The washing solvent is at least one of tetrahydrofuran, acetone, water and ethanol.

10. Use of the aromatic biguanide-based covalent organic framework material according to any one of claims 1 to 3 or the aromatic biguanide-based covalent organic framework material prepared by the preparation method according to any one of claims 4 to 9 in photocatalytic degradation of pharmaceutical micropollutants.

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