A pyrene-based covalent organic framework material, and a preparation method and application thereof

Abstract

This invention belongs to the field of photocatalytic degradation of antibiotics, specifically relating to a pyrene-based covalent organic framework material, its preparation method, and its applications. Using 1,3,6,8-tetra(4-aminophenyl)pyrene and 2,5-dihydroxyterephthalaldehyde as raw materials, it is synthesized via a Schiff base condensation reaction under anisole solvent, acetic acid catalyst, and nitrogen protection, achieving hydroxyl functionalization of the pyrene group. The pyrene-based covalent organic framework material possesses both pyrene ring and hydroxyl functional groups, exhibits high crystallinity, and a specific surface area of ​​1878 m². 2 With a band gap of 1.90 eV, it is responsive to visible light. Under a 300W xenon lamp, it achieves a degradation rate of over 99% for sulfadiazine concentrations of 1 mg / L to 10 mg / L within 90 minutes, reaching 82% at 15 mg / L, and retains over 85% of its performance after 5 cycles. This material is simple to prepare, has no metal toxicity, and is suitable for the treatment of organic pollutants in water, providing a new option for the photocatalytic degradation of sulfadiazine.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic degradation of antibiotics, specifically relating to a pyrene-based covalent organic framework material, its preparation method, and its application. Background Technology

[0002] In recent years, antibiotics have attracted widespread attention as a new class of organic pollutants. Among them, sulfadiazine (SDZ) has become one of the typical recalcitrant pollutants in water bodies due to its widespread use in the pharmaceutical and livestock industries. These substances typically persist in natural water bodies at trace levels for extended periods, not only interfering with the normal physiological functions of aquatic organisms and inducing the development of drug-resistant genes in microorganisms, but also potentially posing a threat to human health through the food chain. However, the concentration of sulfadiazine in the aquatic environment is extremely low, making traditional treatment technologies such as physical adsorption and biodegradation ineffective in removing it. Therefore, advanced oxidation processes are increasingly being used to remove sulfadiazine residues from water bodies.

[0003] Among numerous advanced oxidation processes, photocatalytic advanced oxidation, which uses sunlight as its energy input, is considered the most sustainable, cost-effective, and promising technology for removing antibiotics from the aquatic environment. However, traditional metal-semiconductor photocatalysts inevitably suffer from metal ion leaching, which can lead to secondary pollution of the aquatic environment. Therefore, the development of efficient and green photocatalysts is particularly important.

[0004] Against this backdrop, carbon-based photocatalysts have attracted widespread attention in the field of water purification due to their non-metallic toxicity and good environmental compatibility. Among the many carbon-based photocatalysts, covalent organic frameworks (COFs) exhibit significant advantages over carbon-based semiconductor materials due to their customizable structure, predictable functional properties, and unique framework structure. Furthermore, the ability of COFs to generate active species under photoexcitation demonstrates their enormous application potential in the degradation of sulfadiazine in aquatic environments.

[0005] However, the hydrophobicity of existing COFs in natural aquatic environments and the extremely low concentration of sulfadiazine result in weak interfacial contact between COFs and sulfadiazine, leading to limited mass transfer of the active material and ultimately reducing degradation efficiency. Furthermore, the limited visible light response, severe carrier recombination, and low oxygen activation efficiency of existing COFs further limit the photocatalytic efficiency and practical applications of the reaction process. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a pyrene-based covalent organic framework material, its preparation method, and its applications. This invention prepares an imine-linked pyrene-based covalent organic framework material with good crystallinity and hydrophilicity through surface hydroxyl functionalization. The introduction of hydroxyl groups not only narrows the band gap, enhances visible light absorption and exciton dissociation, but also optimizes the molecular structure to improve oxygen adsorption and electron transfer, and improves interfacial contact with sulfadiazine, thereby exhibiting excellent photocatalytic performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The first objective of this invention is to provide a pyrene-based covalent organic framework material having the following structural units:

[0009] .

[0010] A second objective of this invention is to provide a method for preparing a pyrene-based covalent organic framework material, comprising the following steps:

[0011] Using 1,3,6,8-tetra(4-aminophenyl)pyrene and 2,5-dihydroxyterephthalaldehyde as raw materials, a Schiff base condensation reaction was carried out in a reaction system consisting of a catalyst and a solvent under a protective gas atmosphere to functionalize the surface hydroxyl groups of 1,3,6,8-tetra(4-aminophenyl)pyrene, thereby obtaining a pyrene-based covalent organic framework material.

[0012] In a preferred embodiment of the present invention, the molar ratio of 1,3,6,8-tetratetra(4-aminophenyl)pyrene to 2,5-dihydroxyterephthalaldehyde is 1:2~5.

[0013] In a preferred embodiment of the present invention, the Schiff base condensation reaction is carried out at a temperature of 120°C to 140°C for 2 days to 5 days.

[0014] In a preferred embodiment of the present invention, the molar ratio of catalyst to 1,3,6,8-tetra(4-aminophenyl)pyrene is 72~100:1, and the catalyst is acetic acid; the molar ratio of solvent to 1,3,6,8-tetra(4-aminophenyl)pyrene is 368~500:1, and the solvent is anisole; the protective gas is nitrogen.

[0015] In a preferred embodiment of the present invention, after the Schiff base condensation reaction is completed, the product obtained from the reaction is washed and dried sequentially. The washing is carried out sequentially with N,N-dimethylformamide and methanol, and the drying temperature is 60℃~80℃ for 8h~12h.

[0016] A third objective of this invention is to provide an application of the above-mentioned pyrene-based covalent organic framework material in the photocatalytic degradation of sulfadiazine.

[0017] In a preferred embodiment of the present invention, a pyrene-based covalent organic framework material is mixed with a sulfadiazine-containing solution to form a mixture, and the mixture is subjected to visible light irradiation treatment.

[0018] In a preferred embodiment of the present invention, the mass-to-volume ratio of the pyrene covalent organic framework material to the sulfadiazine-containing solution to be treated is 1 mg: 1 mL to 10 mL; the concentration of sulfadiazine in the sulfadiazine-containing solution to be treated is 1 mg / L to 15 mg / L.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. The pyrene-based covalent organic framework material provided by this invention is constructed by functionalizing the surface of a pyrene-based covalent organic framework material with hydroxyl groups, resulting in an imine-linked pyrene-based covalent organic framework material (PyTTA-COF-OH) with good crystallinity and hydrophilicity. The introduction of hydroxyl groups narrows the band gap, lowers the reaction barrier, enhances its light absorption in the visible light region, and promotes exciton dissociation and charge separation efficiency. Furthermore, the introduction of hydroxyl groups optimizes the molecular structure of PyTTA-COF-OH, enhances its oxygen adsorption capacity, promotes the transfer of electrons to adsorbed oxygen, improves interfacial contact with sulfadiazine, increases carrier mobility, and promotes oxygen activation, exhibiting excellent photocatalytic performance.

[0021] 2. The preparation method of pyrene-based covalent organic framework material provided by this invention. Using 1,3,6,8-tetra(4-aminophenyl)pyrene and 2,5-dihydroxyterephthalaldehyde as raw materials, a pyrene-based covalent organic framework material (PyTTA-COF-OH) with good crystallinity and hydrophilicity linked by imine bonds was successfully constructed through a one-step synthesis method. By changing the functional groups on the aldehyde monomer, the surface microenvironment of COFs was adjusted, thereby synthesizing PyTTA-COF-OH with surface hydroxyl functionalization. The method is simple, easy to operate, and requires simple reaction conditions.

[0022] 3. The surface-hydroxylated PyTTA-COF-OH prepared by this invention exhibits excellent photocatalytic performance, achieving a 99% sulfadiazine removal rate within a 90-minute reaction time, providing a new perspective for COFs-based photocatalytic materials for the efficient degradation of sulfadiazine in practical aquatic environments. Attached Figure Description

[0023] Figure 1 The XPS C1s spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention are shown.

[0024] Figure 2 The XPS N 1s spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention are shown.

[0025] Figure 3 The Fourier transform infrared spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention are shown.

[0026] Figure 4 The nitrogen adsorption-desorption curves are shown for the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention.

[0027] Figure 5 This is a scanning electron microscope image of the pyrene-based covalent organic framework material prepared in Comparative Example 1 of this invention.

[0028] Figure 6 This is a scanning electron microscope image of the pyrene-based covalent organic framework material prepared in Example 1 of the present invention.

[0029] Figure 7 This is a high-resolution transmission electron microscope image of the pyrene-based covalent organic framework material prepared in Example 1 of the present invention.

[0030] Figure 8 The images show the UV-Vis diffuse reflectance spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention.

[0031] Figure 9 The band gap energy diagrams are shown for the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention.

[0032] Figure 10 The transient photocurrent response diagrams are shown for the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention.

[0033] Figure 11 The photoluminescence spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention are shown.

[0034] Figure 12 The time-resolved photoluminescence decay curves of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention are shown.

[0035] Figure 13 The graph shows the photocatalytic degradation performance of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention.

[0036] Figure 14 This is a cycle stability test diagram of the pyrene-based covalent organic framework material prepared in Example 1 of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments and comparative examples of this invention can be purchased from the market or prepared by existing methods.

[0039] Existing covalent organic framework (COF) photocatalysts exhibit hydrophobicity and extremely low sulfadiazine concentrations in natural aquatic environments, resulting in weak interfacial contact between COFs and sulfadiazine. This limits mass transfer of the active substance and ultimately reduces degradation efficiency. Furthermore, the limited visible light response, severe carrier recombination, and low oxygen activation efficiency of existing COFs further restrict photocatalytic efficiency and practical applications. Therefore, constructing covalent organic framework photocatalysts with good interfacial contact, strong visible light response, rapid charge carrier separation, and high oxygen activation efficiency represents a potential direction for the degradation of sulfadiazine in aquatic environments. Studies have shown that improving the hydrophilicity of photocatalysts significantly promotes the mass transfer process, improves the utilization rate of photogenerated carriers, and enhances the interaction between the catalyst and sulfadiazine, thereby effectively improving the efficiency of photocatalytic degradation of antibiotics.

[0040] Based on this, the present invention provides a pyrene-based covalent organic framework material, which has the following structural units:

[0041] .

[0042] In this invention, a wavy line is used. "" indicates that the above repeated structural units have been omitted.

[0043] This invention employs a synergistic strategy of surface microenvironment hydroxylation regulation and π-conjugated structure expansion. By functionalizing pyrene-based covalent organic framework materials with hydroxyl groups, a pyrene-based covalent organic framework material (PyTTA-COF-OH) with good crystallinity and hydrophilicity and imine bond linkages is constructed. The presence of hydroxyl functional groups further promotes exciton dissociation and oxygen adsorption, bridging the generation of reactive species. The pyrene monomer, with its unique large π-conjugated system, exhibits a wide light absorption range and can effectively absorb visible light, thus constructing a covalent organic framework photocatalyst. The introduction of hydroxyl groups narrows the band gap, lowers the reaction barrier, and enhances its light absorption capacity in the visible light region, while simultaneously promoting exciton dissociation and charge separation efficiency. Furthermore, the introduction of hydroxyl groups optimizes the molecular structure of PyTTA-COF-OH, enhances its oxygen adsorption capacity, promotes the transfer of electrons to adsorbed oxygen, improves interfacial contact with sulfadiazine, increases carrier mobility, and promotes oxygen activation, exhibiting excellent photocatalytic performance. Therefore, this invention combines a synergistic strategy of regulating surface microenvironment hydroxylation with π-conjugated structure expansion to simultaneously enhance hydrophilicity, light absorption capacity, and carrier separation efficiency, thereby achieving visible light photocatalytic degradation of sulfadiazine.

[0044] This invention also provides a method for preparing a pyrene-based covalent organic framework material, comprising the following steps: using 1,3,6,8-tetra(4-aminophenyl)pyrene and 2,5-dihydroxyterephthalaldehyde as raw materials, a Schiff base condensation reaction is carried out in a reaction system consisting of a catalyst and a solvent under a protective gas atmosphere to functionalize the surface hydroxyl groups of 1,3,6,8-tetra(4-aminophenyl)pyrene to obtain a pyrene-based covalent organic framework material.

[0045] It should be noted that the core advantage of using 1,3,6,8-tetra(4-aminophenyl)pyrene (PyTTA) as the amino monomer stems from the synergistic effect of the pyrene ring conjugated structure and the amino functional groups. The pyrene ring is a large π-conjugated system with strong UV-Vis absorption characteristics, and can form efficient electron transport channels through π-π stacking. Its rigid planar structure forms a robust framework through intramolecular covalent bonds and intermolecular π-π interactions, allowing the COF to maintain structural integrity in high-temperature and acidic environments. The high-density distribution of amino groups gives the COF framework a high connection density and abundant mesoporous structure. The large conjugated system of the pyrene ring can rapidly transfer photogenerated electrons, reducing recombination with holes. The hydrophobic environment of the pyrene ring and the amino and hydroxyl groups achieve dual-mode adsorption of sulfadiazine through π-π stacking and polar interactions, respectively. 2,5-Dihydroxyterephthalaldehyde was used as the aldehyde monomer. It contains two para-hydroxyl groups and can be directionally introduced into the benzene ring site of the COF framework through Schiff base reaction with PyTTA amino group, thereby realizing the hydroxyl functionalization of the surface microenvironment.

[0046] The Schiff base condensation reaction is the core reaction for preparing the pyrene-based covalent organic framework material (PyTTA-COF-OH) in this invention. Its mechanism involves the dehydration condensation of an amino group (-NH2) with an aldehyde group (-CHO) to form an imine bond (-C=N-). 1,3,6,8-Tetra(4-aminophenyl)pyrene provides the amino group as a nucleophile. 2,5-Dihydroxyterephthalaldehyde provides the aldehyde group, with the carbon atom of the aldehyde group serving as the electrophilic center. Specifically, the reaction mechanism is as follows: First, a nucleophilic addition reaction occurs, where the nitrogen atom of the amino group, carrying a lone pair of electrons, attacks the electrophilic carbon atom of the aldehyde group, forming a hemiacetal. Second, a dehydration reaction occurs, where the nitrogen atom of the amino group forms a carbon-nitrogen double bond (C=N) with the carbon atom of the aldehyde group, generating an imine bond (Schiff base) and releasing water molecules simultaneously.

[0047] In some embodiments, the molar ratio of 1,3,6,8-tetra(4-aminophenyl)pyrene to 2,5-dihydroxyterephthalaldehyde is 1:2 to 5. When using this ratio, 2,5-dihydroxyterephthalaldehyde is in excess. This excess is intended to promote the forward reaction and achieve surface hydroxyl functionalization. First, as an aldehyde monomer in the reversible Schiff base condensation reaction, excess 2,5-dihydroxyterephthalaldehyde shifts the reaction equilibrium towards the formation of imine bonds, increasing the conversion rate of the reactants and ensuring that PyTTA reacts fully to generate more of the target product. Second, containing two para-hydroxyl groups, excess 2,5-dihydroxyterephthalaldehyde ensures sufficient hydroxyl groups are introduced into the benzene ring sites of the COF framework, achieving hydroxyl functionalization of the surface microenvironment and improving the material's hydrophilicity, light absorption, and photocatalytic degradation performance of sulfadiazine.

[0048] In some embodiments, the Schiff base condensation reaction is carried out at a temperature of 120°C to 140°C for 2 to 5 days. This temperature range provides sufficient activation energy to allow the two reactants to fully react and undergo the Schiff base condensation reaction, forming imine bonds. If the temperature is below 120°C, the reaction rate may be too slow, resulting in low conversion of the reactants or even failure to fully form the target framework structure. If the temperature is above 140°C, side reactions (such as over-condensation or reactant decomposition) may occur, affecting the purity and crystallinity of the product. In addition, this temperature range helps to control the crystallinity and hydrophilicity of the product. Therefore, 120°C to 140°C is the optimized temperature range for balancing reaction efficiency, product structure, and properties.

[0049] In some embodiments, the molar ratio of catalyst to 1,3,6,8-tetra(4-aminophenyl)pyrene is 72-100:1, and the catalyst is acetic acid. Acetic acid is chosen as the catalyst primarily due to its proton catalytic activity and polar solvent properties. The H⁺ released from the dissociation of acetic acid can effectively promote the Schiff base condensation reaction, lower the activation energy, and accelerate the formation of imine bonds. The polarity of acetic acid enhances the solubility of PyTTA in anisole, ensuring reaction homogeneity and preventing feedstock agglomeration or incomplete local reactions. Acetic acid is a weak acid and is less likely to cause imine bond hydrolysis or feedstock decomposition at 120-140°C, ensuring the stability of the framework structure. The molar ratio of acetic acid to PyTTA is 72-100:1, which aims to ensure that the catalyst fully exerts its proton catalytic activity, guarantees sufficient dissolution of feedstock and reaction homogeneity, and balances catalytic efficiency and product stability.

[0050] In some embodiments, the molar ratio of solvent to 1,3,6,8-tetra(4-aminophenyl)pyrene is 368~500:1, and the solvent is anisole. Anisole is chosen as a polar organic solvent for the following reasons: First, it has good solubility, possessing both hydrophobic and polar groups. It dissolves the conjugated structure of the pyrene monomer through π-π interactions and disperses the aldehyde monomer through polar interactions, avoiding raw material agglomeration or uneven reaction. Second, its boiling point of 154℃ is higher than the reaction temperature range (120℃~140℃), ensuring that it remains liquid during the reaction and maintaining system stability. Third, it can be removed by washing with N,N-dimethylformamide and methanol, is low in toxicity, and is volatile, conforming to green chemistry processes and facilitating industrial production.

[0051] In some embodiments, the protective gas is nitrogen. As an inert gas, nitrogen can remove oxygen from the reaction system, protect the stability of easily oxidized functional groups, and at the same time isolate moisture in the air, ensuring the reaction system is dry, promoting the forward reaction, and improving product yield and structural integrity.

[0052] In some embodiments, the reaction system needs to be sonicated before the Schiff base condensation reaction. The sonication power is 100kW~400kW, and the sonication time is 15min~30min. The purpose of sonicating the reaction system is to ensure that the raw materials are fully mixed to form a homogeneous reaction system, and to avoid local high concentrations or agglomeration due to uneven dispersion of raw materials. This ensures that the Schiff base condensation reaction proceeds efficiently and improves the crystallinity and structural integrity of the product.

[0053] In some embodiments, after the Schiff base condensation reaction is completed, the product obtained from the reaction is washed and dried sequentially. The washing is performed sequentially using N,N-dimethylformamide and methanol, and the drying temperature is 60℃~80℃ for 8h~12h.

[0054] Finally, this invention provides an application of the above-mentioned pyrene-based covalent organic framework material in the photocatalytic degradation of sulfadiazine. Specifically, the pyrene-based covalent organic framework material is mixed with a sulfadiazine-containing solution to form a mixture, which is then subjected to phototreatment.

[0055] In some embodiments, the mass-to-volume ratio of the pyrene-based covalent organic framework material to the sulfadiazine-containing solution to be treated is 1 mg: 1 mL to 10 mL; the concentration of sulfadiazine in the solution to be treated is 1 mg / L to 15 mg / L. The reason for using this concentration range for sulfadiazine is that when the concentration is in the range of 1 mg / L to 10 mg / L, PyTTA-COF-OH exhibits a degradation rate exceeding 99% for sulfadiazine, demonstrating excellent degradation performance. While the degradation rate decreases to 82% at a concentration as high as 15 mg / L, it still maintains a high removal efficiency, indicating that PyTTA-COF-OH remains applicable in high-concentration pollution scenarios and demonstrates its potential for treating water bodies contaminated with different concentrations of sulfadiazine.

[0056] In some embodiments, the visible light irradiation treatment is preferably performed using a xenon lamp. Its wavelength is 420 nm to 780 nm, covering the visible light range, intended to demonstrate that PyTTA-COF-OH is a visible light photocatalyst; the power density is 0.1 W / cm². 2 ~3W / cm 2 The power density corresponds to the power of the xenon lamp used. The treatment time is 30-90 minutes. Under these conditions, the material can efficiently activate the photocatalytic reaction, achieving rapid degradation of sulfadiazine.

[0057] The surface-hydroxylated PyTTA-COF-OH prepared by this invention exhibits excellent photocatalytic performance, achieving a 99% removal rate of sulfadiazine within a 90-minute reaction time. This invention provides a new perspective for COFs-based photocatalytic materials for the efficient degradation of sulfadiazine in practical aquatic environments.

[0058] The following specific examples will provide further explanation.

[0059] Example 1

[0060] A method for preparing a pyrene-based covalent organic framework material includes the following steps:

[0061] S1. Weigh 28.3 mg (equivalent to 50 μmol) of 1,3,6,8-tetratetra(4-aminophenyl)pyrene, 16.6 mg (equivalent to 100 μmol) of 2,5-dihydroxyterephthalaldehyde, and 2 mL of anisole solvent, and add them sequentially to a glass pressure-resistant tube. Sonicate the mixture for 15 min at 100 kW to ensure homogeneity. Then add 0.3 mL of 12 M acetic acid solution to obtain a mixed solution.

[0062] S2. Pour nitrogen into the glass pressure tube to ensure it is full of nitrogen, then seal it and heat it in an oven at 120°C for 3 days.

[0063] S3. After the reaction is complete, cool to room temperature and wash the precipitate formed in the glass pressure tube three times in a cycle with N,N-dimethylformamide and methanol. Then, dry the obtained powder in a vacuum oven at 80°C for 12 hours to obtain the pyrene-based covalent organic framework material, named PyTTA-COF-OH. The structural formula of the pyrene-based covalent organic framework material is shown below:

[0064] .

[0065] Example 2

[0066] A method for preparing a pyrene-based covalent organic framework material includes the following steps:

[0067] S1. Weigh 28.3 mg (equivalent to 50 μmol) of 1,3,6,8-tetratetra(4-aminophenyl)pyrene, 24.9 mg (equivalent to 150 μmol) of 2,5-dihydroxyterephthalaldehyde, and 2 mL of anisole solvent, and add them sequentially to a glass pressure-resistant tube. Sonicate the mixture for 15 min at 100 kW to ensure homogeneity. Then add 0.3 mL of 12 M acetic acid solution to obtain a mixed solution.

[0068] S2. Pour nitrogen into the glass pressure tube to ensure it is full of nitrogen, then seal it and heat it in an oven at 120°C for 3 days.

[0069] S3. After the reaction is complete, cool to room temperature and wash the precipitate formed in the glass pressure tube three times in a cycle with N,N-dimethylformamide and methanol. Then, dry the obtained powder in a vacuum oven at 80°C for 12 hours to obtain the pyrene-based covalent organic framework material. The structural formula of the pyrene-based covalent organic framework material is shown below:

[0070] .

[0071] Example 3

[0072] A method for preparing a pyrene-based covalent organic framework material includes the following steps:

[0073] S1. Weigh 28.3 mg (equivalent to 50 μmol) of 1,3,6,8-tetratetra(4-aminophenyl)pyrene, 41.5 mg (equivalent to 250 μmol) of 2,5-dihydroxyterephthalaldehyde, and 2 mL of anisole solvent, and add them sequentially to a glass pressure-resistant tube. Sonicate the mixture for 15 min at 100 kW to ensure homogeneity. Then add 0.3 mL of 12 M acetic acid solution to obtain a mixed solution.

[0074] S2. Pour nitrogen into the glass pressure tube to ensure it is full of nitrogen, then seal it and heat it in an oven at 120°C for 3 days.

[0075] S3. After the reaction is complete, cool to room temperature and wash the precipitate formed in the glass pressure tube three times in a cycle with N,N-dimethylformamide and methanol. Then, dry the obtained powder in a vacuum oven at 80°C for 12 hours to obtain the pyrene-based covalent organic framework material. The structural formula of the pyrene-based covalent organic framework material is shown below:

[0076] .

[0077] Example 4

[0078] A method for preparing a pyrene-based covalent organic framework material includes the following steps:

[0079] S1. Weigh 28.3 mg (equivalent to 50 μmol) of 1,3,6,8-tetratetra(4-aminophenyl)pyrene, 16.6 mg (equivalent to 100 μmol) of 2,5-dihydroxyterephthalaldehyde, and 2 mL of anisole solvent, and add them sequentially to a glass pressure-resistant tube. Sonicate the mixture for 15 min at 100 kW to ensure homogeneity. Then add 0.3 mL of 12 M acetic acid solution to obtain a mixed solution.

[0080] S2. Pour nitrogen into the glass pressure tube to ensure it is full of nitrogen, then seal it and heat it in an oven at 120°C for 5 days.

[0081] S3. After the reaction is complete, cool to room temperature and wash the precipitate formed in the glass pressure tube three times in a cycle with N,N-dimethylformamide and methanol. Then, dry the obtained powder in a vacuum oven at 80°C for 12 hours to obtain the pyrene-based covalent organic framework material. The structural formula of the pyrene-based covalent organic framework material is shown below:

[0082] .

[0083] Comparative Example 1

[0084] A method for preparing a pyrene-based covalent organic framework material includes the following steps:

[0085] S1. Accurately weigh 28.3 mg (equivalent to 50 μmol) of 1,3,6,8-tetratetra(4-aminophenyl)pyrene, 13.4 mg (equivalent to 100 μmol) of terephthalaldehyde, and 2 mL of anisole solvent, and add them sequentially to a glass pressure-resistant tube. Sonicate the mixture for 15 min at 100 kW until homogeneous. Then add 0.3 mL of 12 M acetic acid solution to obtain a mixed solution.

[0086] S2. Pour nitrogen into the glass pressure tube to ensure it is full of nitrogen, then seal it and heat it in an oven at 120°C for 3 days.

[0087] S3. After the reaction is complete, cool to room temperature and wash the precipitate formed in the glass pressure tube three times in a cycle with N,N-dimethylformamide and methanol. Then dry the obtained powder in a vacuum oven at 80°C for 12 hours to obtain the pyrene-based covalent organic framework material, named PyTTA-COF-H.

[0088] Since the pyrene-based covalent organic framework materials prepared in Examples 1 to 4 have similar structures and basically the same properties, the pyrene-based covalent organic framework material prepared in Example 1 will be used as an example for further explanation, and the results are analyzed as follows.

[0089] Figure 1 The images show the XPS C1s spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention. Figure 1 It can be seen that the intensity of the O1s peak in PyTTA-COF-OH is significantly enhanced compared to PyTTA-COF-H. This is mainly due to the successful introduction of hydroxyl groups into the surface microenvironment of PyTTA-COF-OH. The C1s spectrum of PyTTA-COF-H consists of four peaks, corresponding to the CC / C=C vibration at 284.8 eV, the CN=C vibration at 285.7 eV, the C=O vibration at 288.1 eV, and the π-π* vibration at 291.2 eV. Compared to PyTTA-COF-H, the C1s spectrum of PyTTA-COF-OH further shows a new peak at 286.3 eV, corresponding to CO, which confirms the successful introduction of the hydroxyl unit.

[0090] Figure 2 The images show the XPS N 1s spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention. Figure 2 It can be seen that the resolved components of the N 1s spectra of the two COFs are attributed to -C=N (399.1 eV) and -NH2 (400.4 eV), which represent the nitrogen atom and unreacted amino group in the imine bond, respectively, proving that both monomers in PyTTA-COF-OH and PyTTA-COF-H successfully formed imine bonds.

[0091] Figure 3 These are the Fourier transform infrared spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention. Figure 3 It can be seen that ~1670 cm⁻¹ appears in the Fourier transform infrared spectra of both PyTTA-COF-H and PyTTA-COF-OH. -1The peaks at these locations belong to imine bonds (-C=N-). This indicates that imine linkages were successfully formed via the Schiff base reaction.

[0092] Figure 4 The accompanying diagram shows the nitrogen adsorption-desorption process of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention. Figure 4 It can be seen that PyTTA-COF-H and PyTTA-COF-OH exhibit typical Type IV isotherms, and significant hysteresis loops are present in the adsorption-desorption isotherms, indicating the presence of mesopores in PyTTA-COF-H and PyTTA-COF-OH. The BET specific surface areas of PyTTA-COF-H and PyTTA-COF-OH are 1639 m² and 1639 m², respectively. 2 / g and 1878m 2 / g. This indicates that the specific surface area of ​​PyTTA-COF-OH is more conducive to oxygen adsorption. Figure 4 The figure in the upper left corner shows the calculations of the nonlocal density functional theory (NLDFT) model. The actual pore sizes of PyTTA-COF-H and PyTTA-COF-OH are 2.23 nm and 2.19 nm, respectively, which are consistent with the predicted pore sizes of the overlapping AA geometry.

[0093] Figure 5 This is a scanning electron microscope image of the pyrene-based covalent organic framework material prepared in Comparative Example 1 of this invention. Figure 5 It can be seen that the PyTTA-COF-H prepared in Comparative Example 1 exhibits a typical microstructure of uniformly sized spherical stacks.

[0094] Figure 6 This is a scanning electron microscope image of the pyrene-based covalent organic framework material prepared in Example 1 of this invention. Figure 6 It can be seen that the PyTTA-COF-OH prepared in Example 1 exhibits a stacked particle morphology with small particle size after the introduction of hydroxyl surface sites. This indicates that the hydroxyl-rich surface microenvironment in PyTTA-COF-OH enhances the intermolecular hydrogen bonding interactions.

[0095] Figure 7 This is a high-resolution transmission electron microscope image of the pyrene-based covalent organic framework material prepared in Example 1 of this invention. Figure 7 It can be seen that the PyTTA-COF-OH prepared in Example 1 exhibits a similar irregular layered stacked structure and all show clear lattice stripes, which indicates that PyTTA-COF-OH has excellent crystallinity.

[0096] Figure 8 The images show the UV-Vis diffuse reflectance spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention. Figure 8It can be seen that, compared with PyTTA-COF-H, the spectral coverage of PyTTA-COF-OH is significantly extended to 600 nm to 800 nm, which is due to the insertion of hydroxyl groups. This indicates that PyTTA-COF-OH has stronger visible light capture performance.

[0097] Figure 9 This is a bandgap energy diagram of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention. Figure 9 It can be seen that, calculated using the Kubekah-Munk function equation, the band gap energies of PyTTA-COF-H and PyTTA-COF-OH are 2.21 eV and 1.90 eV, respectively, indicating that PyTTA-COF-OH has a smaller band gap width.

[0098] Figure 10 The transient photocurrent response diagrams are shown for the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention. Figure 10 It can be seen that the transient photocurrent intensity of PyTTA-COF-OH is higher than that of PyTTA-COF-H, indicating that the modulation strategy of hydroxylation of the surface microenvironment improves the carrier separation efficiency.

[0099] Figure 11 The images show the photoluminescence spectra of the pyrene-based covalent organic frameworks prepared in Example 1 and Comparative Example 1 of this invention. Figure 11 It can be seen that the photoluminescence intensity of PyTTA-COF-OH is significantly lower than that of PyTTA-COF-H. This indicates that the electrons (e) in PyTTA-COF-OH... - ) and holes (h + The recombination rate of ) is higher than that of PyTTA-COF-H.

[0100] Figure 12 This is a time-resolved photoluminescence decay curve of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention. Figure 12 According to the fluorescence decay fitting, the average fluorescence lifetime of PyTTA-COF-OH is 5.01 ns, which is much higher than that of PyTTA-COF-H (0.47 ns). This indicates that PyTTA-COF-OH exhibits a higher nonradiative decay transition rate and stronger charge transfer capability under photoexcitation.

[0101] 10 mg of PyTTA-COF-OH prepared in Example 1 and 10 mg of PyTTA-COF-H prepared in Comparative Example 1 were weighed and mixed with 100 mL of a sulfadiazine-containing solution to be treated. The concentration of sulfadiazine in the solution to be treated was 10 mg / L. After being ultrasonically dispersed evenly, the mixture was transferred to a photocatalytic reactor and reacted under visible light irradiation for 90 min under a 300 W xenon lamp. Figure 13 This image shows the photocatalytic degradation performance of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of this invention. Figure 13 It was found that PyTTA-COF-OH exhibited significantly enhanced photooxidation activity of sulfadiazine under visible light irradiation, with a degradation rate as high as 99% within 90 minutes. This indicates that the presence of hydroxyl groups effectively enhances the photocatalytic activity of the pyrene-based covalent organic framework material.

[0102] Figure 14 This is a cycle stability test diagram of the pyrene-based covalent organic framework material prepared in Example 1 of this invention. Figure 14 It can be seen that after five consecutive cycles, the photocatalytic degradation performance of PyTTA-COF-OH on sulfadiazine only weakened slightly, which indicates that PyTTA-COF-OH has good stability in the visible light photocatalytic degradation system of sulfadiazine.

[0103] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0104] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. The application of a pyrene-based covalent organic framework material in the photocatalytic degradation of sulfadiazine, characterized in that, Pyrene-based covalent organic framework materials have the following structural units: 。 2. The application of the pyrene-based covalent organic framework material according to claim 1 in the photocatalytic degradation of sulfadiazine, characterized in that, A method for preparing pyrene-based covalent organic framework materials includes the following steps: Using 1,3,6,8-tetra(4-aminophenyl)pyrene and 2,5-dihydroxyterephthalaldehyde as raw materials, a Schiff base condensation reaction was carried out in a reaction system consisting of a catalyst and a solvent under a protective gas atmosphere to functionalize the surface hydroxyl groups of 1,3,6,8-tetra(4-aminophenyl)pyrene, thereby obtaining a pyrene-based covalent organic framework material.

3. The application of the pyrene-based covalent organic framework material according to claim 2 in the photocatalytic degradation of sulfadiazine, characterized in that, The molar ratio of 1,3,6,8-tetra(4-aminophenyl)pyrene to 2,5-dihydroxyterephthalaldehyde is 1:2~5.

4. The application of the pyrene-based covalent organic framework material according to claim 2 in the photocatalytic degradation of sulfadiazine, characterized in that, The Schiff base condensation reaction takes place at a temperature of 120℃ to 140℃ for 2 to 5 days.

5. The application of the pyrene-based covalent organic framework material according to claim 2 in the photocatalytic degradation of sulfadiazine, characterized in that, The molar ratio of catalyst to 1,3,6,8-tetra(4-aminophenyl)pyrene is 72~100:1, and the catalyst is acetic acid; the molar ratio of solvent to 1,3,6,8-tetra(4-aminophenyl)pyrene is 368~500:1, and the solvent is anisole; the protective gas is nitrogen.

6. The application of the pyrene-based covalent organic framework material according to claim 2 in the photocatalytic degradation of sulfadiazine, characterized in that, After the Schiff base condensation reaction is completed, the product obtained from the reaction is washed and dried sequentially. The washing is carried out with N,N-dimethylformamide and methanol in sequence, and the drying temperature is 60℃~80℃ for 8h~12h.

7. The application of the pyrene-based covalent organic framework material according to claim 1 in the photocatalytic degradation of sulfadiazine, characterized in that, The pyrene-based covalent organic framework material was mixed with a sulfadiazine-containing solution to form a mixture, which was then subjected to visible light irradiation.

8. The application of the pyrene-based covalent organic framework material according to claim 1 in the photocatalytic degradation of sulfadiazine, characterized in that, The mass-to-volume ratio of the pyrene covalent organic framework material to the sulfadiazine-containing solution to be treated is 1 mg: 1 mL to 10 mL; the concentration of sulfadiazine in the sulfadiazine-containing solution to be treated is 1 mg / L to 15 mg / L.

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