Hydrophilic heteroporous covalent organic frameworks, methods of making the same, and applications in photocatalytic degradation of organic pollutants

Abstract

The application discloses a kind of hydrophilic heteroporous covalent organic frameworks and preparation method and application in photocatalytic degradation organic pollutant, the hydrophilic heteroporous covalent organic framework is with 4 ',5 '-dual (4-formylphenyl)-3 ',6 '-dimethoxy-[1,1 ':2 ',1 "-triphenyl] 4,4 "-dimethyl formaldehyde and 4,4 '-(benzo [c] [1,2,5] thiazole-4,7-diyl) diphenylamine as raw material by condensation reaction after preparation.The hydrophilic heteroporous covalent organic framework of the application has the advantages of high catalytic activity, stable physical and chemical properties, good mass transfer effect, many active sites, etc., as a kind of excellent new photocatalyst, can be widely used in photocatalytic degradation of organic pollutants in water, and can realize the efficient removal of organic pollutants in water, high use value, good application prospect, for realizing the effective management of organic pollutant wastewater has important significance.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, and relates to a hydrophilic heteroporous covalent organic framework, its preparation method, and its application in the photocatalytic degradation of organic pollutants. Background Technology

[0002] Compared to the metal leaching risk of traditional metal-based catalysts, porous organic polymers have become a key focus of research in environmental photocatalytic materials due to their non-metallic properties, customizable chemical structures, and high specific surface area. However, the structural design of existing porous organic polymers faces key challenges. For example, micropores provide abundant active sites, but their narrow size increases mass transfer resistance; conversely, mesopores can enhance mass transfer, but at the cost of reduced active site density. This imbalance limits further improvements in photocatalytic performance. Therefore, obtaining a porous organic polymer with excellent photocatalytic performance is an urgent technical problem to be solved.

[0003] Covalent organic frameworks (COFs) are crystalline network materials composed of strong covalent bonds between symmetrical organic molecules. These materials possess advantages such as large specific surface area, low framework density, high porosity, controllable physicochemical properties, ease of functionalization, and diverse synthetic strategies. COFs have demonstrated excellent performance in numerous fields, including heterogeneous catalysis, energy storage, sensing, adsorption, membrane separation, and biotherapy, and have experienced rapid development in the last decade. Compared to COFs with uniform pore structures, COFs with heterogeneous pore structures (i.e., integrating different pore types within a single framework to construct heteroporous COFs) are structurally more complex, significantly increasing the design difficulty. Therefore, constructing heteroporous COFs is more challenging than constructing COFs with uniform pores. To date, there are almost no reports on the application of heteroporous COF materials in the photocatalytic degradation of organic pollutants, especially those utilizing hydrophilic heteroporous COFs. Therefore, finding a hydrophilic heteroporous covalent organic framework with high catalytic activity, stable physicochemical properties, good mass transfer effect, and many active sites is of great significance and urgent need for promoting the widespread application of covalent organic frameworks in the photocatalytic degradation of organic pollutants. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a hydrophilic heteroporous covalent organic framework with high catalytic activity, stable physicochemical properties, good mass transfer effect and many active sites, as well as its preparation method and application.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A hydrophilic, heteroporous, covalent organic framework, wherein the structure of the hydrophilic, heteroporous, covalent organic framework is composed of periodic structural units connected together, and the structure of the periodic structural units is as follows:

[0007]

[0008] The wavy lines in the formula represent omitted repeating structural units.

[0009] The above-mentioned hydrophilic heteroporous covalent organic framework is further improved in that the hydrophilic heteroporous covalent organic framework is prepared by condensation reaction of 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde and 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine.

[0010] In a further improvement of the aforementioned hydrophilic heteroporous covalent organic framework, the mass ratio of 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde to 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine is 1.1 to 1.5:1.

[0011] As a general technical concept, the present invention also provides a method for preparing a hydrophilic heteroporous covalent organic framework, wherein the method uses 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde and 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine as raw materials to prepare the hydrophilic heteroporous covalent organic framework through a condensation reaction.

[0012] In a further improvement to the above preparation method, the mass ratio of 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde and 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine is 1.1 to 1.5:1.

[0013] The above preparation method, further improved, includes the following steps:

[0014] S1. Mix 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde and 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine, and add an organic solvent and an acid catalyst sequentially to obtain a mixture;

[0015] S2. The mixture obtained in step S1 is subjected to a freezing-pumping-thawing cycle for degassing and then vacuum sealed.

[0016] S3. The mixture obtained in step S2 after being degassed by freezing-pumping-thawing cycles is subjected to a condensation reaction to obtain a hydrophilic heteroporous covalent organic framework.

[0017] In a further improvement to the above preparation method, in step S1, the ratio of 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde to the organic solvent and the acid catalyst is 32 mg: 1 mL: 0.2 mL; the organic solvent is a mixed solvent of 1,3,5-trimethylbenzene and 1,4-dioxane; the volume ratio of 1,3,5-trimethylbenzene and 1,4-dioxane is 1:1; and the acid catalyst is acetic acid.

[0018] In a further improvement to the above preparation method, in step S2, the number of cycles for freezing-pumping-thawing degassing is 3.

[0019] In a further improvement to the above preparation method, in step S3, the temperature of the condensation reaction is 120°C, and the time of the condensation reaction is 48h to 72h. After the condensation reaction, the following treatment is also included: washing, filtering, and drying the reaction product; the washing is performed by washing three times with tetrahydrofuran and acetone respectively; the filtration is performed using an organic filter membrane with a pore size of 0.22μm; the drying is carried out under vacuum conditions; the drying temperature is 80°C; and the drying time is 24h.

[0020] In a further improvement to the above preparation method, the hydrophilic porous covalent organic framework is composed of periodic structural units connected together, and the structure of the periodic structural units is as follows:

[0021]

[0022] The wavy lines in the formula represent omitted repeating structural units.

[0023] As a general technical concept, the present invention also provides the application of the above-mentioned hydrophilic heteroporous covalent organic framework or the hydrophilic heteroporous covalent organic framework prepared by the above-mentioned preparation method in the photocatalytic degradation of organic pollutants.

[0024] The above application is further improved by using a hydrophilic heteroporous covalent organic framework to photocatalytically degrade organic pollutants in water, including the following steps: mixing the hydrophilic heteroporous covalent organic framework with organic pollutant wastewater, stirring, and carrying out a photocatalytic reaction under light conditions to complete the photocatalytic degradation of organic pollutants in the wastewater; the amount of the hydrophilic heteroporous covalent organic framework added is 0.08g to 0.1g per liter of the organic pollutant wastewater.

[0025] In a further improvement to the above application, the initial concentration of organic pollutants in the organic pollutant wastewater is 5 mg / L to 10 mg / L; the organic pollutants in the organic pollutant wastewater are antibiotics; the antibiotics are quinolone antibiotics and / or tetracycline antibiotics; the quinolone antibiotics are at least one of ofloxacin and norfloxacin; the tetracycline antibiotics are tetracycline; the stirring is carried out in darkness, the stirring speed is 300 r / min to 400 r / min, and the stirring time is 0.5 h to 1 h; the light source used in the photocatalytic reaction is a xenon lamp and / or natural light; and the photocatalytic reaction time is 30 min to 60 min.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] (1) In view of the shortcomings of existing covalent organic framework photocatalysts, such as poor mass transfer effect, low active sites, poor charge separation efficiency and low conductivity, and the resulting poor degradation rate of organic pollutants in water, this invention creatively provides a hydrophilic heteroporous covalent organic framework. This hydrophilic heteroporous covalent organic framework has abundant mesopores and micropores, which can solve the imbalance limitation between mass transfer and reaction. It can not only improve the mass transfer effect, but also improve the reaction efficiency. More importantly, it introduces abundant methoxy groups to construct hydrophilic channels, which can enhance the surface hydrophilicity and promote its interaction with water molecules. It can not only generate a large number of free radicals on the surface, but also promote the effective contact between free radicals and organic pollutants in water, thereby further improving the reaction efficiency. Compared to hydrophobic heteroporous covalent organic frameworks (COF-C), the hydrophilic heteroporous covalent organic framework (COF-O) of this invention has the following advantages: (a) It has excellent absorption capacity in the visible light range and a more negative conduction band potential, which facilitates the generation of more superoxide radicals on the material surface, thereby improving the photocatalytic activity of the hydrophilic heteroporous covalent organic framework under natural sunlight irradiation; (b) The introduction of methoxy groups constructs hydrophilic channels, and the enhanced surface hydrophilicity of COF-O promotes its excellent interaction with water molecules, facilitating effective contact between surface-generated free radicals and new pollutants in the water; (c) It has abundant active sites and high mass transfer efficiency, resulting in a faster reaction rate. The hydrophilic heteroporous covalent organic framework of this invention has advantages such as high catalytic activity, stable physicochemical properties, good mass transfer effect, and numerous active sites. As a novel photocatalyst with excellent performance, it can be widely used for the photocatalytic degradation of organic pollutants in water, achieving efficient removal of organic pollutants from water bodies. It has high application value and promising prospects.

[0028] (2) This invention also provides a method for preparing a hydrophilic heteroporous covalent organic framework. Using 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde and 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine as raw materials, a hydrophilic heteroporous covalent organic framework with high catalytic activity, stable physicochemical properties, good mass transfer effect, and numerous active sites can be prepared through a condensation reaction. Furthermore, by optimizing the amount of each raw material and the conditions of the condensation reaction, the nucleation and growth rates during the reaction process can be precisely controlled, thereby enabling the preparation of high-quality covalent organic framework crystals. In particular, even slight changes to the above conditions may result in the inability to obtain the corresponding hydrophilic heteroporous covalent organic framework structure.

[0029] (3) This invention also provides an application of a hydrophilic heteroporous covalent organic framework in the photocatalytic degradation of organic pollutants. Specifically, the hydrophilic heteroporous covalent organic framework is used to photocatalytically degrade organic pollutants in water, thereby achieving effective purification of organic pollutants in water. Taking ofloxacin as an example, the hydrophilic heteroporous covalent organic framework of this invention can achieve a 100% removal rate of ofloxacin within 45 minutes, and the photocatalytic degradation effect is very good. At the same time, the hydrophilic heteroporous covalent organic framework of this invention can achieve complete removal of pollutants within 45 to 60 minutes under different pH ranges, different ionic strengths and different actual water conditions, which is of great significance for the effective treatment of organic pollutant wastewater. Attached Figure Description

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0031] Figure 1 The images show the XRD patterns of the hydrophilic heteroporous covalent organic framework (COF-O) prepared in Example 1 of this invention and the hydrophobic heteroporous covalent organic framework (COF-C) prepared in Comparative Example 1.

[0032] Figure 2 The images show the UV-Vis diffuse reflectance of the hydrophilic heteroporous covalent organic framework (COF-O) prepared in Example 1 and the hydrophobic heteroporous covalent organic framework (COF-C) prepared in Comparative Example 1.

[0033] Figure 3 The conduction band potential diagrams are for the hydrophilic heteroporous covalent organic framework (COF-O) prepared in Example 1 of the present invention and the covalent organic framework (COF-C) prepared in Comparative Example 1.

[0034] Figure 4 The images show the water vapor adsorption of the hydrophilic heteroporous covalent organic framework (COF-O) prepared in Example 1 and the hydrophobic heteroporous covalent organic framework (COF-C) prepared in Comparative Example 1.

[0035] Figure 5 The diagram shows the degradation effect of hydrophilic porous covalent organic framework (COF-O) and hydrophobic porous covalent organic framework (COF-C) on ofloxacin in Example 2 of this invention.

[0036] Figure 6 The graph shows the degradation effect of hydrophilic porous covalent organic framework (COF-O) on ofloxacin under different pH conditions in Example 3 of this invention.

[0037] Figure 7The graph shows the degradation effect of hydrophilic porous covalent organic framework (COF-O) on ofloxacin under different ionic strengths in Example 4 of this invention.

[0038] Figure 8 This is a diagram showing the degradation effect of the hydrophilic porous covalent organic framework (COF-O) on ofloxacin in actual water in Example 5 of the present invention. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0040] In the following embodiments of the present invention, unless otherwise specified, the materials and instruments used are commercially available, the equipment used is conventional equipment, and the data obtained are the average values ​​of more than three repeated experiments.

[0041] Example 1

[0042] A hydrophilic heteroporous covalent organic framework is disclosed, wherein the structure of the hydrophilic heteroporous covalent organic framework is composed of periodic structural units connected together, wherein the structure of the periodic structural units is as follows:

[0043]

[0044] The wavy lines in the formula represent omitted repeating structural units.

[0045] A method for preparing the hydrophilic porous covalent organic framework in this embodiment specifically involves using 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde (commercially available) and 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine (commercially available) as raw materials through a condensation reaction to obtain the hydrophilic porous covalent organic framework, including the following steps:

[0046] (1) Weigh 32 mg of 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde and 28 mg of 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine and mix them in a vacuum tube. Add 0.5 mL of 1,3,5-trimethylbenzene and 0.5 mL of 1,4-dioxane, sonicate for 15 min, mix well, add 0.2 mL of acetic acid, sonicate for 3 min, mix well, and obtain the mixture.

[0047] (2) The mixture in step (1) is subjected to a freezing-pumping-thawing cycle for degassing. Specifically, the mixture is frozen using liquid nitrogen, and the gas in the frozen mixture is extracted by an oil pump and then thawed. This process is repeated 3 times, with vacuum sealing and heating at 120°C for 72 hours. After completion, the reaction product is taken out and cooled.

[0048] (3) The reaction product in step (2) was washed three times with tetrahydrofuran and acetone (10 mL each time), filtered with an organic filter membrane with a pore size of 0.22 μm, and then dried at 80 °C for 24 h under vacuum to obtain a hydrophilic heteroporous covalent organic framework, denoted as COF-O.

[0049] Comparative Example 1

[0050] A hydrophobic heteroporous covalent organic framework (COF-C) is composed of periodic structural units, wherein the structure of the periodic structural units is as follows:

[0051]

[0052] The wavy lines in the formula represent omitted repeating structural units.

[0053] The preparation method of the hydrophobic heteroporous covalent organic framework (COF-C) in Comparative Example 1 includes the following steps:

[0054] (1) 32 mg of 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde and 26 mg of 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine were mixed in a vacuum tube, 0.5 mL of 1,3,5-trimethylbenzene and 0.5 mL of 1,4-dioxane were added, and the mixture was sonicated for 15 min to obtain a homogeneous mixture. 0.2 mL of acetic acid was added, and the mixture was sonicated for 3 min to obtain a homogeneous mixture.

[0055] (2) The mixture in step (1) is subjected to three cycles of freezing-pumping-thawing degassing. Specifically, the mixture is frozen using liquid nitrogen, the gas in the frozen mixture is extracted by an oil pump, and then thawing is performed. This process is repeated three times, with vacuum sealing and heating at 120°C for 72 hours. After completion, the reaction product is taken out and cooled.

[0056] (3) The reaction product in step (2) was washed three times with tetrahydrofuran and acetone (10 mL each time), filtered with an organic filter membrane with a pore size of 0.22 μm, and then dried at 80 °C for 24 h under vacuum to obtain a hydrophobic heteroporous covalent organic framework, denoted as COF-C.

[0057] Performance testing

[0058] (1) XRD detection

[0059] The covalent organic frameworks prepared in Example 1 and Comparative Example 1 were subjected to powder XRD analysis, as shown below. Figure 1 As shown. Figure 1 The images show the XRD patterns of the hydrophilic porous covalent organic framework (COF-O) prepared in Example 1 and the hydrophobic porous covalent organic framework (COF-C) prepared in Comparative Example 1. Figure 1 It can be seen that these two covalent organic framework materials have similar characteristic peaks. The strong diffraction peak of 2θ = 3.17° corresponds to the (100) crystal plane, which is consistent with the crystal structure of COFs materials, indicating that the main body of these two materials is a covalent organic framework.

[0060] (2) Ultraviolet-visible diffuse reflectance detection

[0061] The covalent organic frameworks prepared in Example 1 and Comparative Example 1 were subjected to UV-Vis diffuse reflectance detection, such as... Figure 2 As shown. Figure 2 The images show the UV-Vis diffuse reflectance spectra of the hydrophilic porous covalent organic framework (COF-O) prepared in Example 1 and the hydrophobic porous covalent organic framework (COF-C) prepared in Comparative Example 1. Figure 2 It is known that both of these covalent organic framework materials have a light absorption range of about 400-600nm and excellent light absorption performance in visible light (λ>420nm), and have the potential to practically utilize solar energy. Figure 3 The conduction band potential diagrams are for the hydrophilic heteroporous covalent organic framework (COF-O) prepared in Example 1 of the present invention and the covalent organic framework (COF-C) prepared in Comparative Example 1. Figure 3 In the study, the conduction band (CB) positions of COF-O and COF-C were determined. Compared with the reversible hydrogen electrode (RHE), they showed potentials of -0.50 and -0.45 eV, respectively. It can be seen that COF-O has a more negative potential, indicating that COF-O can more effectively utilize electrons to generate superoxide radicals (-0.30 eV).

[0062] (3) Water vapor adsorption test

[0063] Water vapor adsorption tests were performed on the covalent organic frameworks prepared in Example 1 and Comparative Example 1. Figure 4 As shown. Figure 4 This is a water vapor adsorption diagram of the hydrophilic heteroporous covalent organic framework (COF-O) prepared in Example 1 and the hydrophobic heteroporous covalent organic framework (COF-C) prepared in Comparative Example 1. Figure 4It can be seen that, compared with COF-C in Comparative Example 1, the COF-O prepared in Example 1 exhibits excellent water absorption capacity (88cm³) at P / P0 = 0.4. 3 / g, equivalent to 71mg / g), compared to COF-C (5cm 3 The adsorption capacity of COF-O increased by 14.2 times (p / g, 4 mg / g). The adsorption capacity of COF-O increased with increasing relative pressure, reaching a maximum of 225 cm⁻¹ at P / P₀ = 1.0. 3 / g (181mg / g). The enhanced surface hydrophilicity of COF-O promotes excellent water interactions, increases the collision frequency between reactants and target pollutants, and improves local reaction kinetics.

[0064] As can be seen from the above results, the hydrophilic heteroporous covalent organic framework of the present invention has abundant mesopores and micropores, which can solve the imbalance limitation between mass transfer and reaction. It can not only improve the mass transfer effect, but also improve the reaction efficiency. More importantly, the introduction of abundant methoxy groups constructs hydrophilic channels, which can enhance the surface hydrophilicity and promote its interaction with water molecules. It can not only generate a large number of free radicals on the surface, but also promote the effective contact between free radicals and organic pollutants in water, thereby further improving the reaction efficiency.

[0065] Example 2

[0066] The application of a hydrophilic heteroporous covalent organic framework in the photocatalytic degradation of organic pollutants, specifically, utilizing the hydrophilic heteroporous covalent organic framework to photocatalytically degrade organic pollutants in water, includes the following steps:

[0067] Weigh 6 mg of the hydrophilic porous covalent organic framework (COF-O) prepared in Example 1 and add it to 60 mL of an organic pollutant (ofloxacin) solution with a concentration of 5 mg / L. Stir magnetically for 1 h in the dark at a speed of 400 r / min to reach adsorption equilibrium. Then turn on the light source and irradiate under simulated sunlight (visible light with λ≥420 nm) for 60 min to carry out photocatalytic reaction and complete the degradation of organic pollutants in the water.

[0068] Control group 1: The hydrophobic porous covalent organic framework (COF-C) prepared in Comparative Example 1 was used instead of the hydrophilic porous covalent organic framework (COF-O), and other conditions were the same.

[0069] During the magnetic stirring and photocatalysis process, 1 mL of sample was taken every 10 min and filtered through a 0.22 μm filter. The filtrate was then analyzed by liquid chromatography to determine the concentration of ofloxacin after adsorption and after light irradiation, thereby obtaining the adsorption effect of COF-O and COF-C on ofloxacin and the photocatalytic degradation effect.

[0070] Figure 5 This image shows the degradation effect of ofloxacin on the hydrophilic porous covalent organic framework (COF-O) and the hydrophobic porous covalent organic framework (COF-C) in Example 2 of this invention. Figure 5 It can be seen that after 1 hour of dark reaction adsorption and 60 minutes of light irradiation, the removal rates of ofloxacin by COF-O and COF-C were 100% and 30%, respectively, and the rate constant of COF-O was 17.86 × 10⁻⁶. -2 min -1 Compared to hydrophobic COF-C (0.77×10⁻⁶), it has a lower hydrophobicity. -2 min -1 The efficiency is 23.3 times higher than that of the hydrophilic heteroporous covalent organic framework (COF-O). This is because the presence of hydrophilicity in the hydrophilic heteroporous covalent organic framework (COF-O) increases the mass transfer of pollutants within the pores, provides more active sites, promotes the collision frequency between reactants and target pollutants, and improves local reaction kinetics. This also shows that the hydrophilic heteroporous covalent organic framework of the present invention has good hydrophilicity, negative conductivity potential, high free radical concentration, high charge separation efficiency, and good photocatalytic degradation effect, while the hydrophobic heteroporous covalent organic framework (COF-C) does not have the above advantages.

[0071] Example 3:

[0072] The photocatalytic degradation effect of hydrophilic porous covalent organic frameworks (COF-O) on organic pollutants under different pH conditions was investigated. The specific experimental methods are as follows:

[0073] Five portions of the hydrophilic porous covalent organic framework (COF-O) prepared in Example 1, each 6 mg, were weighed and added to organic pollutant (ofloxacin) solutions with pH values ​​of 3, 5, 7, 9, and 11 (the solution volume was 60 mL and the concentration was 5 mg / L). The solutions were magnetically stirred for 1 h in the dark at a speed of 400 r / min to reach adsorption equilibrium. Then, the light source was turned on and the solutions were irradiated under simulated sunlight (visible light with λ≥420 nm) for 60 min to carry out photocatalytic reaction, thus completing the degradation of organic pollutants in the water.

[0074] During the magnetic stirring and photocatalysis process, 1 mL of sample was taken every 10 min and filtered through a 0.22 μm filter. The filtrate was then analyzed by liquid chromatography to determine the concentration of ofloxacin after adsorption and after light irradiation, thereby obtaining the adsorption effect of COF-O on ofloxacin and the photocatalytic degradation effect.

[0075] Figure 6 This image shows the degradation effect of the hydrophilic porous covalent organic framework (COF-O) on ofloxacin under different pH conditions in Example 3 of this invention. Figure 6It is known that within 45-60 minutes, the hydrophilic porous covalent organic framework (COF-O) of this invention achieves nearly 100% removal rate of ofloxacin at pH values ​​of 3, 5, 7, 9, and 11. pH value affects the charge of the material and the form in which new pollutants exist. Different pH values, based on the Zeta potential of COF-O, result in different surface charge properties, thus affecting the mutual adsorption of ofloxacin on the COF-O surface. Combined with... Figure 6 The results show that the hydrophilic heteroporous covalent organic framework (COF-O) prepared by this invention has excellent degradation performance under pH conditions of 3 to 11, which indicates that the hydrophilic heteroporous covalent organic framework (COF-O) of this invention has strong stability and excellent adaptability.

[0076] Example 4:

[0077] The photocatalytic degradation effect of hydrophilic heteroporous covalent organic frameworks (COF-O) on organic pollutants under different ionic strength conditions was investigated. The specific experimental methods are as follows:

[0078] Four portions of the hydrophilic porous covalent organic framework (COF-O) prepared in Example 1, each 6 mg, were weighed and added to solutions of organic pollutants (ofloxacin) containing 0, 10 mM, 20 mM, 30 mM, and 50 mM NaCl, respectively (the solution volume was 60 mL and the concentration was 5 mg / L). The solutions were magnetically stirred at 400 r / min for 1 h in the dark to reach adsorption equilibrium. Then, the light source was turned on and the solutions were irradiated under simulated sunlight (visible light with λ ≥ 420 nm) for 60 min to carry out photocatalytic reaction, thus completing the degradation of organic pollutants in the water.

[0079] During the magnetic stirring and photocatalysis process, 1 mL of sample was taken every 10 min and filtered through a 0.22 μm filter. The filtrate was then analyzed by liquid chromatography to determine the concentration of ofloxacin after adsorption and after light irradiation, thereby obtaining the adsorption effect of COF-O on ofloxacin and the photocatalytic degradation effect.

[0080] Figure 7 This image shows the degradation effect of the hydrophilic porous covalent organic framework (COF-O) on ofloxacin under different ionic strengths in Example 4 of this invention. Figure 7 It is known that within 45-60 minutes, the hydrophilic porous covalent organic framework (COF-O) of this invention achieves nearly 100% removal rate of new pollutants in NaCl solutions (0-50 mM) of varying concentrations. Under high salinity conditions, chloride ions will coat the active sites on the material surface, competitively scavenging reactive oxygen species and affecting the material's degradation efficiency. Combined with... Figure 7The results show that the hydrophilic porous covalent organic framework (COF-O) of the present invention can effectively remove ofloxacin (OFL) from solution in 0-50 mM NaCl, which indicates that the hydrophilic porous covalent organic framework (COF-O) of the present invention has abundant active sites and excellent adaptability.

[0081] Example 5:

[0082] The photocatalytic degradation effect of a hydrophilic heteroporous covalent organic framework (COF-O) on an organic pollutant (ofloxacin) in actual water bodies was investigated. The specific experimental methods are as follows:

[0083] Five portions of the hydrophilic porous covalent organic framework (COF-O) prepared in Example 1, each weighing 6 mg, were added to four portions of organic pollutant (ofloxacin) solutions (60 mL, 5 mg / L) prepared from pure water, tap water, lake water, secondary treated water from constructed wetlands (W2), and tertiary treated water from constructed wetlands (W3), respectively. The mixtures were thoroughly mixed and dispersed, and the mixture was magnetically stirred at 400 r / min for 1 h in the dark to reach adsorption equilibrium. Then, a photocatalytic reaction was carried out under light irradiation for 60 min to complete the degradation of the organic pollutant.

[0084] During the magnetic stirring and photocatalysis process, 1 mL of sample was taken every 10 min and filtered through a 0.22 μm filter. The filtrate was then analyzed by liquid chromatography to determine the concentration of ofloxacin after adsorption and after light irradiation, thereby obtaining the adsorption effect of COF-O on ofloxacin and the photocatalytic degradation effect.

[0085] Figure 8 This image shows the degradation effect of the hydrophilic porous covalent organic framework (COF-O) on ofloxacin in actual water in Example 5 of this invention. Figure 8 It can be seen that, compared with laboratory pure water conditions, and in actual water bodies including tap water, lake water, river water, and secondary and tertiary treated water from constructed wetlands, the prepared hydrophilic heteroporous covalent organic framework (COF-O) achieved a 100% removal rate of ofloxacin within 45 minutes. Combined with... Figure 6 and Figure 7 The results show that the hydrophilic heteroporous covalent organic framework (COF-O) prepared in this invention can resist the interference caused by different pH and ionic strengths. Therefore, natural organic matter, ions, and other substances contained in actual water bodies do not inhibit the photocatalytic performance of the hydrophilic heteroporous covalent organic framework. The above results prove that the hydrophilic heteroporous covalent organic framework COF-O of this invention is feasible in actual wastewater treatment and has high application prospects.

[0086] The results above show that, compared with the hydrophobic heteroporous covalent organic framework (COF-C), the hydrophilic heteroporous covalent organic framework (COF-O) of this invention has the following advantages: (a) It has excellent absorption capacity in the visible light range and a more negative conduction band potential, which facilitates the generation of more superoxide radicals on the material surface, thereby improving the photocatalytic activity of the hydrophilic heteroporous covalent organic framework under natural sunlight irradiation; (b) The introduction of methoxy groups constructs hydrophilic channels, and the enhanced surface hydrophilicity of COF-O promotes its excellent interaction with water molecules, facilitating effective contact between surface-generated free radicals and new pollutants in the water; (c) It has abundant active sites and high mass transfer efficiency, resulting in a faster reaction rate. Therefore, the hydrophilic heteroporous covalent organic framework of this invention has advantages such as high catalytic activity, stable physicochemical properties, good mass transfer effect, and numerous active sites. As a novel photocatalyst with excellent performance, it can be widely used for photocatalytic degradation of organic pollutants in water, and can achieve efficient removal of organic pollutants from water, demonstrating high application value and promising prospects.

[0087] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A hydrophilic, heteroporous, covalent organic framework, characterized in that, The structure of the hydrophilic heteroporous covalent organic framework is composed of periodic structural units connected together, and the structure of the periodic structural units is as follows: The wavy lines in the formula represent omitted repeating structural units.

2. A method for preparing the hydrophilic porous covalent organic framework as described in claim 1, characterized in that, The preparation method uses 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde and 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine as raw materials to prepare a hydrophilic heteroporous covalent organic framework through a condensation reaction.

3. The preparation method according to claim 2, characterized in that, The mass ratio of 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde to 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine is 1:1.1 to 1.

5.

4. The preparation method according to claim 3, characterized in that, Includes the following steps: S1. Mix 4',5'-bis(4-formylphenyl)-3',6'-dimethoxy-[1,1':2',1"-terphenyl]-4,4"-dicarboxaldehyde and 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine, and add an organic solvent and an acid catalyst sequentially to obtain a mixture; S2. The mixture obtained in step S1 is subjected to a freezing-pumping-thawing cycle for degassing and then vacuum sealed. S3. The mixture obtained in step S2 after freezing-pumping-thawing cycle degassing is subjected to a condensation reaction to obtain a hydrophilic heteroporous covalent organic framework.

5. The preparation method according to claim 4, characterized in that, In step S1, the organic solvent is a mixed solvent of 1,3,5-trimethylbenzene and 1,4-dioxane; the volume ratio of 1,3,5-trimethylbenzene and 1,4-dioxane is 1:1; and the acid catalyst is acetic acid. In step S2, the number of cycles for the freezing-pumping-thawing degassing cycle is 3. In step S3, the condensation reaction temperature is 120°C, and the condensation reaction time is 48h to 72h. After the condensation reaction, the following treatment is also included: washing, filtering, and drying the reaction product. The washing is performed by washing three times with tetrahydrofuran and acetone respectively. The filtration is performed using an organic filter membrane with a pore size of 0.22μm. The drying is carried out under vacuum conditions, the drying temperature is 80°C, and the drying time is 24h.

6. The application of a hydrophilic heteroporous covalent organic framework as described in claim 1 or a hydrophilic heteroporous covalent organic framework prepared by any one of claims 2 to 5 in the photocatalytic degradation of organic pollutants.

7. The application according to claim 6, characterized in that, The photocatalytic degradation of organic pollutants in water using a hydrophilic heteroporous covalent organic framework includes the following steps: mixing the hydrophilic heteroporous covalent organic framework with organic pollutant wastewater, stirring, and carrying out a photocatalytic reaction under light conditions to complete the photocatalytic degradation of organic pollutants in the wastewater; the amount of the hydrophilic heteroporous covalent organic framework added is 0.08 g to 0.1 g per liter of the organic pollutant wastewater.

8. The application according to claim 7, characterized in that, The initial concentration of organic pollutants in the wastewater is 5 mg / L to 10 mg / L; the organic pollutants in the wastewater are antibiotics; the antibiotics are quinolone antibiotics and / or tetracycline antibiotics; the quinolone antibiotics are at least one of ofloxacin and norfloxacin; the tetracycline antibiotics are tetracyclines; the stirring is carried out in the dark, the stirring speed is 300 r / min to 400 r / min, and the stirring time is 0.5 h to 1 h; the light source used in the photocatalytic reaction is a xenon lamp and / or natural light; the photocatalytic reaction time is 30 min to 60 min.

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