Pyrenyl covalent organic framework material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photocatalytic degradation of antibiotics, and particularly relates to a pyrenyl covalent organic framework material as well as a preparation method and application thereof. According to the method, 1, 3, 6, 8-tetra (4-aminophenyl) pyrene and 2, 5-dihydroxy terephthalaldehyde are taken as raw materials and are synthesized through Schiff base condensation reaction in an anisole solvent and an acetic acid catalyst under the protection of nitrogen, and pyrenyl surface hydroxyl functionalization is realized. The pyrenyl covalent organic framework material has a pyrene ring and a hydroxyl functional group, is high in crystallinity, has the specific surface area of 1878m < 2 > / g and the band gap width of 1.90 eV, and can respond to visible light. Under a 300 W xenon lamp, the degradation rate of sulfadiazine with the concentration of 1 mg / L-10 mg / L within 90 minutes exceeds 99%, the degradation rate of sulfadiazine with the concentration of 15 mg / L reaches 82%, and the performance retention rate of sulfadiazine after 5 times of circulation exceeds 85%. The material is simple to prepare, has no metal toxicity, is suitable for treating organic pollutants in water, and provides a new choice for photocatalytic degradation of sulfadiazine.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic degradation of antibiotics, and particularly relates to a pyrene-based covalent organic framework material and a preparation method and application thereof. Background Art

[0002] In recent years, antibiotics have garnered widespread attention as an emerging class of organic pollutants. Sulfadiazine (SDZ), a key refractory pollutant in water, has emerged as a prominent example due to its widespread use in medicine and animal husbandry. These substances, often present at trace levels in natural water bodies, can disrupt the normal physiological functions of aquatic organisms, induce the development of drug-resistant genes in microorganisms, and potentially pose a threat to human health through the food chain. However, the extremely low concentrations of SDZ in aquatic environments make it difficult to effectively remove using traditional treatment technologies such as physical adsorption and biodegradation. Consequently, advanced oxidation processes are increasingly being used to remove SDZ residues from water.

[0003] Among numerous advanced oxidation processes, photocatalytic advanced oxidation processes (AOPs) using sunlight as energy input are considered the most sustainable, cost-effective, and promising advanced technology for removing antibiotics from aquatic environments. However, conventional metal semiconductor photocatalysts inevitably suffer from metal ion dissolution, which can lead to secondary contamination of the aquatic environment. Therefore, the development of efficient and green photocatalysts is crucial.

[0004] Against this backdrop, carbon-based photocatalysts have garnered widespread attention in the field of water purification due to their metal-free nature and excellent environmental compatibility. Among the numerous carbon-based photocatalysts, covalent organic frameworks (COFs) offer significant advantages over carbon-based semiconductor materials due to their customizable structures, predictable functional properties, and unique framework architecture. Furthermore, their ability to generate active species upon photoexcitation holds great potential for the degradation of sulfadiazine in aquatic environments.

[0005] However, the hydrophobicity of existing COFs in natural water environments and the extremely low concentration of sulfadiazine result in weak interfacial contact between COFs and sulfadiazine, which in turn limits the mass transfer of the active species and ultimately reduces the 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 application of the reaction process. Summary of the Invention

[0006] To address these issues, the present invention provides a pyrene-based covalent organic framework material, its preparation method, and its application. This invention utilizes surface hydroxyl functionalization to produce an imine-linked pyrene-based covalent organic framework material with excellent crystallinity and hydrophilicity. 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 enhance oxygen adsorption and electron transfer, improving interfacial contact with sulfadiazine, thereby exhibiting excellent photocatalytic performance.

[0007] To achieve the above object, the present invention adopts the following technical solutions: The first object of the present invention is to provide a pyrene-based covalent organic framework material, wherein the pyrene-based covalent organic framework material has the following structural units: .

[0008] A second object of the present invention is to provide a method for preparing a pyrene-based covalent organic framework material, comprising the following steps: Using 1,3,6,8-tetrakis(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-tetrakis(4-aminophenyl)pyrene to obtain a pyrene-based covalent organic framework material.

[0009] In a preferred embodiment of the present invention, the molar ratio of 1,3,6,8-tetrakis(4-aminophenyl)pyrene to 2,5-dihydroxyterephthalaldehyde is 1:2-5.

[0010] In a preferred embodiment of the present invention, the temperature of the Schiff base condensation reaction is 120° C. to 140° C., and the time is 2 days to 5 days.

[0011] In a preferred embodiment of the present invention, the molar ratio of the catalyst to 1,3,6,8-tetrakis(4-aminophenyl)pyrene is 72-100:1, and the catalyst is acetic acid; the molar ratio of the solvent to 1,3,6,8-tetrakis(4-aminophenyl)pyrene is 368-500:1, and the solvent is anisole; and the protective gas is nitrogen.

[0012] In a preferred embodiment of the present invention, after the Schiff base condensation reaction is completed, the product obtained by the reaction is washed and dried in sequence, with N,N-dimethylformamide and methanol used for washing in sequence, and the drying temperature is 60° C. to 80° C. for 8 h to 12 h.

[0013] The third object of the present invention is to provide an application of the above-mentioned pyrene-based covalent organic framework material in the photocatalytic degradation of sulfadiazine.

[0014] In a preferred embodiment of the present invention, the pyrene-based covalent organic framework material is mixed with a solution to be treated containing sulfadiazine to form a mixed solution, and the mixed solution is irradiated with visible light.

[0015] In a preferred embodiment of the present invention, the mass volume ratio of the pyrene-based covalent organic framework material to the solution to be treated containing sulfadiazine is 1 mg:1 mL~10 mL; the concentration of sulfadiazine in the solution to be treated containing sulfadiazine is 1 mg / L~15 mg / L.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The pyrene-based covalent organic framework material provided by the present invention is constructed by functionalizing the surface of the pyrene-based covalent organic framework material with hydroxyl groups to obtain an imine-linked pyrene-based covalent organic framework material (PyTTA-COF-OH) with excellent crystallinity and hydrophilicity. The introduction of hydroxyl groups narrows the band gap, lowers the reaction barrier, enhances its light absorption capacity 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, and promotes electron transfer to the adsorbed oxygen, thereby improving interfacial contact with sulfadiazine, increasing carrier mobility, and promoting oxygen activation, exhibiting excellent photocatalytic performance.

[0017] 2. The present invention provides a method for preparing a pyrene-based covalent organic framework material. Using 1,3,6,8-tetrakis(4-aminophenyl)pyrene and 2,5-dihydroxyterephthalaldehyde as raw materials, a one-step synthesis method successfully constructed an imine-linked pyrene-based covalent organic framework material (PyTTA-COF-OH) with excellent crystallinity and hydrophilicity. By modifying the functional groups on the aldehyde monomers, the surface microenvironment of the COFs was adjusted, resulting in the synthesis of surface hydroxyl-functionalized PyTTA-COF-OH. This method is simple, easy to operate, and requires simple reaction conditions.

[0018] 3. The surface-hydroxylated PyTTA-COF-OH prepared in the present 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 actual water environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The XPS C 1s spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of the present invention are shown.

[0020] Figure 2 The XPS N 1s spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of the present invention are shown.

[0021] Figure 3 1 and 2. Fourier transform infrared spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of the present invention.

[0022] Figure 4 Graphs showing nitrogen adsorption-desorption curves of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of the present invention.

[0023] Figure 5 This is a scanning electron microscope image of the pyrene-based covalent organic framework material prepared in Comparative Example 1 of the present invention.

[0024] 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.

[0025] Figure 7 This is a high-resolution transmission electron micrograph of the pyrene-based covalent organic framework material prepared in Example 1 of the present invention.

[0026] Figure 8 The UV-visible diffuse reflectance spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of the present invention are shown.

[0027] Figure 9 2 is a band gap energy diagram of the pyrene-based covalent organic framework material prepared in Example 1 and Comparative Example 1 of the present invention.

[0028] Figure 10 This is a transient photocurrent response diagram of the pyrene-based covalent organic framework material prepared in Example 1 and Comparative Example 1 of the present invention.

[0029] Figure 11 These are photoluminescence spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of the present invention.

[0030] Figure 12 This is a time-resolved photoluminescence attenuation curve of the pyrene-based covalent organic framework material prepared in Example 1 and Comparative Example 1 of the present invention.

[0031] Figure 13 This is a diagram showing the photocatalytic degradation performance of the pyrene-based covalent organic framework material prepared in Example 1 of the present invention and Comparative Example 1.

[0032] Figure 14 This is a test chart of the cyclic stability of the pyrene-based covalent organic framework material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments and comparative examples of the present invention can be purchased from the market or prepared by existing methods.

[0035] The hydrophobicity of existing COFs in natural water environments and the extremely low concentration of sulfadiazine result in weak interfacial contact between COFs and sulfadiazine, which in turn causes limited mass transfer of active substances and ultimately reduces degradation efficiency. In addition, the limited visible light response, severe carrier recombination and low oxygen activation efficiency of existing COFs further limit the photocatalytic efficiency and practical application during the reaction process. Therefore, constructing covalent organic framework photocatalysts with good interfacial contact, strong visible light response, fast charge carrier separation and high oxygen activation efficiency is a potential development direction for sulfadiazine degradation in aqueous environments. Studies have shown that improving the hydrophilicity of the photocatalyst significantly promotes the mass transfer process, improves the utilization of photogenerated carriers, and enhances the interaction between the catalyst and sulfadiazine, thereby effectively improving the efficiency of photocatalytic degradation of antibiotics.

[0036] Based on this, the present invention provides a pyrene-based covalent organic framework material, which has the following structural units: .

[0037] In the present invention, the wavy line " ” indicates that the above-mentioned repeating structural units are omitted.

[0038] This study utilizes a synergistic strategy of surface microenvironment hydroxylation and π-conjugated structure expansion to functionalize the surface of a pyrene-based covalent organic framework (COF) with hydroxyl groups. This results in an imine-linked pyrene-based COF (PyTTA-COF-OH) with excellent crystallinity and hydrophilicity. The presence of hydroxyl groups further promotes exciton dissociation and oxygen adsorption, paving the way for the generation of reactive species. The pyrene monomer, with its unique large π-conjugated system, exhibits a broad absorption range and effectively absorbs visible light, thus constructing a COF photocatalyst. The introduction of hydroxyl groups narrows the band gap, lowers the reaction barrier, enhances its light absorption in the visible region, and promotes exciton dissociation and charge separation efficiency. Furthermore, the introduction of hydroxyl groups optimizes the molecular structure of PyTTA-COF-OH, enhances oxygen adsorption capacity, and promotes electron transfer to adsorbed oxygen, improving interfacial contact with sulfadiazine, increasing carrier mobility, and promoting oxygen activation, resulting in excellent photocatalytic performance. Therefore, the present invention adopts a synergistic strategy combining surface microenvironment hydroxylation regulation with π-conjugated structure expansion to simultaneously enhance hydrophilicity, light absorption capacity and carrier separation efficiency to achieve visible light photocatalytic degradation of sulfadiazine.

[0039] The present invention also provides a method for preparing a pyrene-based covalent organic framework material, comprising the following steps: using 1,3,6,8-tetrakis(4-aminophenyl)pyrene and 2,5-dihydroxyterephthalaldehyde as raw materials, carrying out a Schiff base condensation reaction in a reaction system consisting of a catalyst and a solvent and under a protective gas atmosphere, functionalizing the surface hydroxyl groups of 1,3,6,8-tetrakis(4-aminophenyl)pyrene to obtain a pyrene-based covalent organic framework material.

[0040] It is important to note that the core advantage of using 1,3,6,8-tetrakis(4-aminophenyl)pyrene (PyTTA) as the amino monomer lies in the synergistic effect of the conjugated structure of the pyrene ring and the amino functional group. The pyrene ring is a large π-conjugated system with strong UV-visible light absorption, forming efficient electron transport channels through π-π stacking. Its rigid planar structure forms a strong backbone through intramolecular covalent bonds and intermolecular π-π interactions, enabling the COF to maintain structural integrity in high temperatures and acidic environments. The high density of amino groups gives the COF framework a high connectivity density and rich mesoporous structure. The large conjugated system of the pyrene ring rapidly transfers photogenerated electrons, minimizing recombination with holes. The hydrophobic environment of the pyrene ring, combined with the amino and hydroxyl groups through π-π stacking and polar interactions, enables dual-mode adsorption of sulfadiazine. 2,5-Dihydroxyterephthalaldehyde is used as the aldehyde monomer, which contains two para-hydroxyl groups. It can condense with PyTTA amino groups through Schiff base reaction to introduce hydroxyl groups into the benzene ring sites of the COF framework, thereby realizing hydroxyl functionalization of the surface microenvironment.

[0041] The Schiff base condensation reaction is the core reaction for preparing the pyrene-based covalent organic framework (PyTTA-COF-OH) of 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-Tetrakis(4-aminophenyl)pyrene provides the amino group, acting as a nucleophile. 2,5-Dihydroxyterephthalaldehyde provides the aldehyde group, with the aldehyde carbon atom serving as the electrophilic center. The specific reaction mechanism involves a nucleophilic addition reaction in the first step, in which the nitrogen atom of the amino group, carrying a lone pair of electrons, attacks the electrophilic carbon atom of the aldehyde group, forming a hemiaminal. In the second step, a dehydration reaction forms a carbon-nitrogen double bond (C=N) between the amino nitrogen atom and the aldehyde carbon atom, forming an imine bond (Schiff base) and simultaneously releasing a water molecule.

[0042] In some embodiments, the molar ratio of 1,3,6,8-tetrakis(4-aminophenyl)pyrene and 2,5-dihydroxyterephthalaldehyde is 1:2~5. When the above ratio is adopted, 2,5-dihydroxyterephthalaldehyde is in an excess state. The purpose of its excess is to promote the forward reaction and realize surface hydroxyl functionalization. First, as an aldehyde monomer of the reversible Schiff base condensation reaction, the excess can shift the reaction equilibrium toward the formation of an imine bond, improve the raw material conversion rate, and ensure that PyTTA fully reacts to generate more target products. Secondly, it contains two para-hydroxyl groups, and the excess can ensure that sufficient hydroxyl groups are directional introduced into the benzene ring site of the COF framework, realize the hydroxyl functionalization of the surface microenvironment, and improve the hydrophilicity, light absorption and other capabilities of the material and the performance of photocatalytic degradation of sulfadiazine.

[0043] In some embodiments, the Schiff base condensation reaction temperature is 120°C to 140°C, and the reaction time is 2 to 5 days. This temperature range provides sufficient activation energy for the two reactants to fully react in the Schiff base condensation reaction, forming an imine bond. If the temperature is below 120°C, the reaction rate may be too slow, resulting in low raw material conversion or even incomplete formation of the target framework structure. If the temperature is above 140°C, side reactions (such as excessive condensation or raw material decomposition) may occur, affecting product purity and crystallinity. Furthermore, this temperature range helps to control the crystallinity and hydrophilicity of the product. Therefore, 120°C to 140°C is the optimal temperature range for balancing reaction efficiency, product structure, and performance.

[0044] In some embodiments, the molar ratio of the catalyst to 1,3,6,8-tetrakis(4-aminophenyl)pyrene is 72-100:1, and the catalyst is acetic acid. Acetic acid is chosen as a catalyst primarily for its proton catalytic activity and polar solvent properties. The H⁺ released by acetic acid can effectively promote the Schiff base condensation reaction, lowering the activation energy and accelerating imine bond formation. The polarity of acetic acid enhances the solubility of PyTTA in anisole, ensuring reaction uniformity and preventing raw material agglomeration or incomplete localized reaction. Acetic acid is relatively weak and is less likely to cause imine bond hydrolysis or raw material decomposition at temperatures between 120°C and 140°C, thus ensuring framework stability. The molar ratio of acetic acid to PyTTA is 72-100:1, designed to ensure that the catalyst fully utilizes its proton catalytic activity, ensuring sufficient raw material dissolution and reaction uniformity, and balancing catalytic efficiency with product stability.

[0045] In some embodiments, the molar ratio of the solvent to 1,3,6,8-tetrakis(4-aminophenyl)pyrene is 368~500:1, and the solvent is anisole. Anisole is selected as a polar organic solvent for the following reasons: First, it has good solubility, and it has both hydrophobic and polar groups. It dissolves the conjugated structure of the pyrene monomer through π-π interaction, and disperses the aldehyde monomer through polar action, avoiding raw material agglomeration or uneven reaction. Second, the boiling point of 154°C is higher than the reaction temperature range (120°C~140°C), ensuring that it remains in liquid form during the reaction and maintaining system stability. Third, it can be removed by washing with N,N-dimethylformamide and methanol. It is low in toxicity, volatile, conforms to green chemical processes, and is convenient for industrial production.

[0046] In some embodiments, the protective gas is nitrogen. As an inert gas, nitrogen can remove oxygen from the reaction system, protect the stability of the easily oxidized functional groups, isolate moisture from the air, ensure the dryness of the reaction system, promote the forward reaction, and improve product yield and structural integrity.

[0047] In some embodiments, the reaction system is ultrasonicated prior to the Schiff base condensation reaction at a power of 100 kW to 400 kW for 15 to 30 minutes. The purpose of ultrasonicating the reaction system is to ensure thorough mixing of the raw materials to form a homogeneous reaction system, thereby avoiding localized excessive concentration or agglomeration due to uneven dispersion of the raw materials. This ensures efficient Schiff base condensation reaction and enhances the crystallinity and structural integrity of the product.

[0048] In some embodiments, after the Schiff base condensation reaction is completed, the product obtained by the reaction is washed and dried in sequence. The washing is carried out using N,N-dimethylformamide and methanol in sequence. The drying temperature is 60° C. to 80° C. and the drying time is 8 h to 12 h.

[0049] Finally, the present 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 solution to be treated containing sulfadiazine to form a mixed solution, and the mixed solution is subjected to light treatment.

[0050] In some embodiments, the mass volume ratio of the pyrene-based covalent organic framework material to the solution to be treated containing sulfadiazine is 1 mg: 1 mL~10 mL; the concentration of sulfadiazine in the solution to be treated containing sulfadiazine is 1 mg / L~15 mg / L. The reason for adopting the above range for the concentration of sulfadiazine is that when it is in the range of 1 mg / L to 10 mg / L, the degradation rate of sulfadiazine by PyTTA-COF-OH exceeds 99%, and the degradation effect is excellent. When the concentration is as high as 15 mg / L, although the degradation rate drops to 82%, it still maintains a high removal efficiency, indicating that PyTTA-COF-OH still has certain applicability in high-concentration pollution scenarios, and shows the potential for treating water bodies contaminated with sulfadiazine at different concentrations.

[0051] In some embodiments, the visible light irradiation treatment is preferably performed using a xenon lamp. The wavelength is 420 nm to 780 nm, covering the visible light range, and is intended to demonstrate that PyTTA-COF-OH is a visible light photocatalyst; the power density is 0.1 W / cm 2 ~3W / cm 2 The power density corresponds to the power of the xenon lamp used. The treatment time ranges from 30 to 90 minutes. Under these conditions, the material can efficiently activate the photocatalytic reaction, achieving rapid degradation of sulfadiazine.

[0052] The surface-hydroxylated PyTTA-COF-OH prepared in this invention exhibits excellent photocatalytic performance, achieving a 99% sulfadiazine removal rate within a 90-minute reaction time. This invention provides a new perspective on COF-based photocatalytic materials for the efficient degradation of sulfadiazine in real water environments.

[0053] The following is further described through specific examples.

[0054] Example 1 A method for preparing a pyrene-based covalent organic framework material comprises the following steps: S1. Weigh 28.3 mg of 1,3,6,8-tetrakis(4-aminophenyl)pyrene (equivalent to 50 μmol), 16.6 mg of 2,5-dihydroxyterephthalaldehyde (equivalent to 100 μmol), and 2 mL of anisole solvent and add them sequentially to a glass pressure tube. Ultrasonicate at 100 kW for 15 minutes to mix thoroughly. Then, add 0.3 mL of 12 M acetic acid solution to obtain a mixed solution.

[0055] S2. Pour nitrogen into the glass pressure tube to ensure that the tube is full of nitrogen, then seal it and heat it in an oven at 120°C for 3 days.

[0056] S3. After the reaction is completed, the mixture is cooled to room temperature, and the precipitate formed in the glass pressure tube is washed three times with N,N-dimethylformamide and methanol in a cycle. The resulting powder is then dried in a vacuum oven at 80°C for 12 hours to obtain a pyrene-based covalent organic framework material, named PyTTA-COF-OH. The structural formula of the pyrene-based covalent organic framework material is shown below:

[0057] .

[0058] Example 2 A method for preparing a pyrene-based covalent organic framework material comprises the following steps: S1. Weigh 28.3 mg of 1,3,6,8-tetrakis(4-aminophenyl)pyrene (equivalent to 50 μmol), 24.9 mg of 2,5-dihydroxyterephthalaldehyde (equivalent to 150 μmol), and 2 mL of anisole solvent, and add them sequentially to a glass pressure tube. Ultrasonicate at 100 kW for 15 minutes to mix them evenly. Then, add 0.3 mL of 12 M acetic acid solution to obtain a mixed solution.

[0059] S2. Pour nitrogen into the glass pressure tube to ensure that the tube is full of nitrogen, then seal it and heat it in an oven at 120°C for 3 days.

[0060] S3. After the reaction is completed, the mixture is cooled to room temperature, and the precipitate formed in the glass pressure tube is washed three times with N,N-dimethylformamide and methanol in a cycle. The resulting powder is then dried in a vacuum oven at 80°C for 12 hours to obtain a pyrene-based covalent organic framework material. The structural formula of the pyrene-based covalent organic framework material is shown below:

[0061] .

[0062] Example 3 A method for preparing a pyrene-based covalent organic framework material comprises the following steps: S1. Weigh 28.3 mg of 1,3,6,8-tetrakis(4-aminophenyl)pyrene (equivalent to 50 μmol), 41.5 mg of 2,5-dihydroxyterephthalaldehyde (equivalent to 250 μmol), and 2 mL of anisole solvent and add them sequentially to a glass pressure tube. Ultrasonicate at 100 kW for 15 minutes to mix thoroughly. Then, add 0.3 mL of 12 M acetic acid solution to obtain a mixed solution.

[0063] S2. Pour nitrogen into the glass pressure tube to ensure that the tube is full of nitrogen, then seal it and heat it in an oven at 120°C for 3 days.

[0064] S3. After the reaction is completed, the mixture is cooled to room temperature, and the precipitate formed in the glass pressure tube is washed three times with N,N-dimethylformamide and methanol in a cycle. The resulting powder is then dried in a vacuum oven at 80°C for 12 hours to obtain a pyrene-based covalent organic framework material. The structural formula of the pyrene-based covalent organic framework material is shown below:

[0065] .

[0066] Example 4 A method for preparing a pyrene-based covalent organic framework material comprises the following steps: S1. Weigh 28.3 mg of 1,3,6,8-tetrakis(4-aminophenyl)pyrene (equivalent to 50 μmol), 16.6 mg of 2,5-dihydroxyterephthalaldehyde (equivalent to 100 μmol), and 2 mL of anisole solvent and add them sequentially to a glass pressure tube. Ultrasonicate at 100 kW for 15 minutes to mix thoroughly. Then, add 0.3 mL of 12 M acetic acid solution to obtain a mixed solution.

[0067] S2. Nitrogen was introduced into the glass pressure tube to ensure that the tube was filled with nitrogen, then the tube was sealed and heated in an oven at 120°C for 5 days.

[0068] S3. After the reaction is completed, the mixture is cooled to room temperature, and the precipitate formed in the glass pressure tube is washed three times with N,N-dimethylformamide and methanol in a cycle. The resulting powder is then dried in a vacuum oven at 80°C for 12 hours to obtain a pyrene-based covalent organic framework material. The structural formula of the pyrene-based covalent organic framework material is shown below:

[0069] .

[0070] Comparative Example 1 A method for preparing a pyrene-based covalent organic framework material comprises the following steps: S1. Accurately weigh 28.3 mg of 1,3,6,8-tetrakis(4-aminophenyl)pyrene (equivalent to 50 μmol), 13.4 mg of terephthalaldehyde (equivalent to 100 μmol), and 2 mL of anisole solvent and add them sequentially to a glass pressure tube. Ultrasonicate at 100 kW for 15 minutes to mix thoroughly. Then, add 0.3 mL of 12 M acetic acid solution to obtain a mixed solution.

[0071] S2. Pour nitrogen into the glass pressure tube to ensure that the tube is full of nitrogen, then seal it and heat it in an oven at 120°C for 3 days.

[0072] S3. After the reaction is completed, the mixture is cooled to room temperature, and the precipitate formed in the glass pressure tube is washed three times with N,N-dimethylformamide and methanol in a cycle. The obtained powder is then dried in a vacuum oven at 80°C for 12 h to obtain a pyrene-based covalent organic framework material, named PyTTA-COF-H.

[0073] Since the pyrene-based covalent organic framework materials prepared in Examples 1 to 4 have similar structures and substantially the same properties, the pyrene-based covalent organic framework material prepared in Example 1 is taken as an example for further description, and the results are analyzed as follows.

[0074] Figure 1 The XPS C 1s spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of the present invention are shown in FIG. 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, which is mainly due to the successful introduction of hydroxyl groups in the surface microenvironment of PyTTA-COF-OH. The C1s spectrum of PyTTA-COF-H is divided into four peaks corresponding to CC / C=C at 284.8 eV, CN=C at 285.7 eV, C=O at 288.1 eV, and π-π* vibration at 291.2 eV. Compared with PyTTA-COF-H, the C1s spectrum of PyTTA-COF-OH further shows a new peak at 286.3 eV corresponding to CO, which proves the successful introduction of hydroxyl units.

[0075] Figure 2 The XPS N 1s spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of the present invention are shown in FIG. 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), representing the nitrogen atom in the imine bond and the unreacted amino group, respectively, proving that both monomers in PyTTA-COF-OH and PyTTA-COF-H successfully formed imine bonds.

[0076] Figure 3 The following is a Fourier transform infrared spectrum of the pyrene-based covalent organic framework material prepared in Example 1 and Comparative Example 1 of the present invention. Figure 3 It can be seen that the FTIR spectra of PyTTA-COF-H and PyTTA-COF-OH both showed a peak around 1670 cm -1 These peaks belong to the imine bond (-C=N-). This indicates that the imine linkage was successfully formed through the Schiff base reaction.

[0077] Figure 4The nitrogen adsorption-desorption diagram of the pyrene-based covalent organic framework material prepared in Example 1 and Comparative Example 1 of the present invention is shown. Figure 4 It can be seen that PyTTA-COF-H and PyTTA-COF-OH show typical type IV isotherms, and there are significant hysteresis loops in the adsorption-desorption isotherms, indicating that there are mesopores in PyTTA-COF-H and PyTTA-COF-OH. The BET specific surface areas of PyTTA-COF-H and PyTTA-COF-OH are 1639m 2 / g and 1878m 2 / g. This shows that the specific surface area of PyTTA-COF-OH is more conducive to the adsorption of oxygen. Figure 4 The figure in the upper left corner is the calculation 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 geometric structure.

[0078] Figure 5 This is a scanning electron microscope image of the pyrene-based covalent organic framework material prepared in Comparative Example 1 of the present invention. Figure 5 It can be seen that the PyTTA-COF-H prepared in Comparative Example 1 exhibits a typical microstructure of stacked spheres of uniform size.

[0079] 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. Figure 6 It can be seen that after the introduction of hydroxyl surface sites, the PyTTA-COF-OH prepared in Example 1 exhibits a stacked particle morphology with smaller particle size. This indicates that the hydroxyl-rich surface microenvironment of PyTTA-COF-OH enhances the hydrogen bonding interaction between molecules.

[0080] Figure 7 This is a high-resolution transmission electron micrograph of the pyrene-based covalent organic framework material prepared in Example 1 of the present invention. Figure 7 It can be seen that the PyTTA-COF-OH prepared in Example 1 exhibits a similar irregular layered stacking structure and shows clear lattice fringes, which indicates that PyTTA-COF-OH has excellent crystallinity.

[0081] Figure 8 The UV-visible diffuse reflectance spectra of the pyrene-based covalent organic framework materials prepared in Example 1 and Comparative Example 1 of the present invention are shown in FIG. Figure 8It can be seen that the spectral coverage of PyTTA-COF-OH is significantly extended to 600 nm to 800 nm compared with PyTTA-COF-H due to the insertion of hydroxyl groups, which indicates that PyTTA-COF-OH has stronger visible light harvesting performance.

[0082] Figure 9 The band gap energy diagram of the pyrene-based covalent organic framework material prepared in Example 1 and Comparative Example 1 of the present invention. Figure 9 It can be seen that the band gap energies of PyTTA-COF-H and PyTTA-COF-OH are calculated by the Kubeka-Munk function equation to be 2.21 eV and 1.90 eV, respectively, indicating that PyTTA-COF-OH has a smaller band gap width.

[0083] Figure 10 The transient photocurrent response diagram of the pyrene-based covalent organic framework material prepared in Example 1 and Comparative Example 1 of the present 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 surface microenvironment hydroxylation improves the carrier separation efficiency.

[0084] Figure 11 The photoluminescence spectra of the pyrene-based covalent organic framework prepared in Example 1 and Comparative Example 1 of the present invention are shown in FIG. 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 - ) and holes (h + ) has a higher recombination rate than PyTTA-COF-H.

[0085] 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 the present invention are shown in FIG. Figure 12 It can be seen that according to the fluorescence decay fitting, the average fluorescence lifetime of PyTTA-COF-OH is 5.01ns, which is much higher than 0.47ns of PyTTA-COF-H, indicating that PyTTA-COF-OH exhibits a higher non-radiative decay transition rate and stronger charge transfer ability under photoexcitation.

[0086] 10 mg of each of the PyTTA-COF-OH prepared in Example 1 and the PyTTA-COF-H prepared in Comparative Example 1 were weighed and mixed with 100 mL of a solution to be treated containing sulfadiazine, wherein the concentration of sulfadiazine in the solution to be treated was 10 mg / L. The mixture was then uniformly dispersed by ultrasonication and transferred to a photocatalytic reactor for reaction under a 300 W xenon lamp using visible light for 90 min. Figure 13 The photocatalytic degradation performance diagram of the pyrene-based covalent organic framework material prepared in Example 1 and Comparative Example 1 of the present invention is shown in FIG. Figure 13 The photooxidative activity of PyTTA-COF-OH towards sulfadiazine was significantly enhanced under visible light irradiation, with a degradation rate of up to 99% within 90 minutes. This indicates that the presence of hydroxyl groups effectively enhances the photocatalytic activity of pyrene-based covalent organic frameworks.

[0087] Figure 14 This is a test chart of the cyclic stability of the pyrene-based covalent organic framework material prepared in Example 1 of the present invention. Figure 14 It can be seen that after five consecutive cycles, the photocatalytic degradation performance of PyTTA-COF-OH for sulfadiazine was only slightly weakened, which indicates that PyTTA-COF-OH has good stability in the visible light catalytic degradation system of sulfadiazine.

[0088] It should be noted that when the present invention relates to numerical ranges, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the attached protection scope is intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0089] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the present invention and its equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A pyrene-based covalent organic framework material, characterized in that: Pyrene-based covalent organic framework materials have the following structural units: 。 2. A method for preparing the pyrene-based covalent organic framework material according to claim 1, characterized in that: The following steps are involved: Using 1,3,6,8-tetrakis(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-tetrakis(4-aminophenyl)pyrene to obtain a pyrene-based covalent organic framework material.

3. The method for preparing a pyrene-based covalent organic framework material according to claim 2, wherein: The molar ratio of 1,3,6,8-tetrakis(4-aminophenyl)pyrene to 2,5-dihydroxyterephthalaldehyde is 1:2-5.

4. The method for preparing a pyrene-based covalent organic framework material according to claim 2, wherein: The temperature of the Schiff base condensation reaction is 120°C~140°C, and the time is 2d~5d.

5. The method for preparing a pyrene-based covalent organic framework material according to claim 2, wherein: The molar ratio of the catalyst to 1,3,6,8-tetrakis(4-aminophenyl)pyrene is 72-100:1, and the catalyst is acetic acid; the molar ratio of the solvent to 1,3,6,8-tetrakis(4-aminophenyl)pyrene is 368-500:1, and the solvent is anisole; and the protective gas is nitrogen.

6. The method for preparing a pyrene-based covalent organic framework material according to claim 2, wherein: After the Schiff base condensation reaction is completed, the product obtained by the reaction is washed and dried in sequence. The washing is carried out using N,N-dimethylformamide and methanol in sequence. The drying temperature is 60° C. to 80° C. and the drying time is 8 h to 12 h.

7. Use of the pyrene-based covalent organic framework material according to claim 1 in photocatalytic degradation of sulfadiazine.

8. Use of the pyrene-based covalent organic framework material in photocatalytic degradation of sulfadiazine according to claim 7, characterized in that: The pyrene-based covalent organic framework material is mixed with a solution to be treated containing sulfadiazine to form a mixed solution, and the mixed solution is irradiated with visible light.

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

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