Covalent organic frameworks with specific pyridine nitrogen sites, methods of preparation, and uses thereof

Abstract

The application belongs to the field of functional material preparation, and particularly relates to a covalent organic framework with specific pyridine nitrogen sites, a preparation method and application thereof in catalytic degradation of antibiotics and synchronous generation of hydrogen peroxide. The covalent organic framework TP-oBPy prepared by using 2,2'-bipyridine-6,6'-diamine as raw material has specific pyridine nitrogen sites, significantly improves photocatalytic activity, and enhances catalytic degradation efficiency of sulfadiazine. For a water solution containing 50 mg / L of sulfadiazine, 0.1 g / L of the covalent organic framework TP-oBPy of the application is added, and more than 98% of the sulfadiazine is catalytically degraded in 50 min. When the water body containing sulfadiazine is treated, more than 90% of the sulfadiazine can be catalytically degraded in 80 min, and the synchronous generation rate of hydrogen peroxide during photocatalytic degradation of sulfadiazine is as high as 6776 micromoles per gram per hour. ‑1 h ‑1 The covalent organic framework TP-oBPy prepared by the application has high application prospect in the fields of photocatalytic degradation of antibiotics and synthesis of hydrogen peroxide.

Description

Technical Field

[0001] This invention belongs to the field of functional material preparation, specifically relating to a covalent organic framework with a specific pyridine nitrogen site and its preparation method, and also relating to the application of the covalent organic framework in the catalytic degradation of antibiotics and the simultaneous generation of hydrogen peroxide. Background Technology

[0002] With the development of medical technology, the widespread use of antibiotics in clinical practice has become a key method for the prevention and treatment of infectious diseases. Sulfadiazine, in particular, has been widely used as a systemic antibiotic since the 1930s due to its high stability and resistance to biodegradation. However, its long-term use and resistance to traditional methods have led to its large accumulation in environmental water sources. Therefore, there is an urgent need to find an effective method to reduce its adverse environmental impact.

[0003] Covalent organic frameworks (COFs) are porous crystalline polymers formed by covalent bonds. They possess a highly ordered and periodic framework and exhibit excellent adsorption properties, making them widely used in the adsorption of pollutants in water bodies. For example, the magnetic fluorinated covalent organic framework material and its preparation method and application, published in CN113717337A, uses carboxylated Fe3O4 nanoparticles as the core and a core-shell structure formed by the condensation polymerization of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 2,3,5,6-tetrafluoro-p-dibenzaldehyde as the shell. The surface of the shell is urchin-like, exhibiting strong adsorption selectivity and high separation and enrichment efficiency for benzoylurea pesticides. For example, in the publication CN113976049A, a COF / CS aerogel and its preparation method and application are described. The COF / CS aerogel is composed of COF nanoparticles cross-linked together by 1,3,5-trialdehyde-2,4,6-phloroglucinol and a chitosan aerogel network. It has excellent porosity and adsorption performance and can adsorb and remove a variety of sulfonamide drugs in water. For example, CN116832791A discloses a novel magnetic covalent organic framework material, its preparation method, and its application. Fe3O4 nanoparticles are used as the core, and their surface is coated with silica formed by the hydrolysis of tetraethyl orthosilicate to obtain Fe3O4@SiO2. Then, PDE-TATP-COF, formed by the combination of 2,6-pyridinedicarboxaldehyde and 1,3,5-tris(4-aminophenyl)benzene, is used as the shell of the magnetic adsorption material to obtain a magnetic material Fe3O4@SiO2@PDE-TATP-COF with abundant benzene rings and nitrogen atoms. It has a large specific surface area and porosity, strong stability, and can extract and enrich various sulfonamide antibiotics from water samples.

[0004] As can be seen from the above, most of the currently synthesized covalent organic framework materials for antibiotic treatment remove pollutants such as antibiotics from water bodies through adsorption, but have not achieved true degradation and removal of antibiotics.

[0005] Photocatalysis, as a sustainable energy utilization strategy, has shown considerable potential in addressing the energy crisis and environmental pollution, enabling the true degradation and removal of antibiotics. A large number of metal-based photocatalysts have emerged in the field of photocatalysis, such as titanium dioxide-based materials, iron-based materials, and metal-organic frameworks and their derivatives, aiming to degrade pollutants in water. For example, CN116769273A discloses a method and application for ligand-induced growth of MOFs / COFs composite materials, which prepared an NM88(D) / TABB-DMTP-COF composite material with excellent photo-Fenton degradation performance and stability. This material possesses excellent specific surface area, visible light absorption capacity, photogenerated carrier separation ability, and photocatalytic ability, exhibiting good catalytic degradation efficiency for sulfadiazine.

[0006] However, the aforementioned NM88(D) / TABB-DMTP-COF composite material contains the metallic element Fe (NM88's full name is NH2-MIL-88B(Fe)). Using metal-based materials in aquatic environments carries the risk of metal leaching, potentially leading to secondary pollution. This highlights the necessity of developing and applying metal-free photocatalysts based on green chemistry principles. Therefore, metal-free photocatalysts, especially carbon-based materials such as graphitic carbon nitride, are being synthesized extensively to promote the degradation of pollutants or the synthesis of high-value products. However, the efficiency of these carbon-based photocatalysts is often limited by high photogenerated carrier recombination rates and structural disorder, resulting in poor catalytic degradation effects on antibiotics. Summary of the Invention

[0007] To address the risks of secondary pollution caused by metal leaching and poor catalytic degradation of antibiotics in existing catalysts, this invention aims to provide a covalent organic framework with specific pyridine nitrogen sites, its preparation method, and its application in the catalytic degradation of sulfadiazine and the simultaneous synthesis of hydrogen peroxide. The covalent organic framework synthesized in this invention exhibits superior photocatalytic activity, capable of catalytically degrading over 98% of sulfadiazine within 50 minutes; and achieving a simultaneous hydrogen peroxide generation rate of up to 6776 μmol / g during the photocatalytic degradation of sulfadiazine. -1 h -1 .

[0008] Based on the above objectives, the technical solution adopted by the present invention is as follows:

[0009] In a first aspect, the present invention provides a covalent organic framework having specific pyridine nitrogen sites, prepared from 1,3,5-trialdehyde phloroglucinol and 2,2'-bipyridine-6,6'-diamine. The structure of the covalent organic framework is composed of periodic structural units connected together, and the structural formula of the periodic structural units is as follows:

[0010] Here, “~” represents the connection site between multiple periodic structural units, that is, each “~” indicates a “-NH” site that connects to another identical periodic structural unit mentioned above.

[0011] Compared to other covalent organic frameworks with pyridine nitrogen sites, the covalent organic framework prepared by this invention using 2,2'-bipyridine-6,6'-diamine as a raw material has specific pyridine nitrogen sites (pyridine nitrogen atoms and amino groups are in a relative ortho-ortho relationship), exhibits strong electron donor-acceptor interactions, significantly improves the separation and transport efficiency of photogenerated charges, and has excellent photocatalytic activity.

[0012] Preferably, the electrochemical impedance value of the covalent organic framework does not exceed 9 ohms.

[0013] Compared to other covalent organic frameworks with pyridine nitrogen sites, the covalent organic framework prepared in this invention has a higher transient photocurrent response value and a relatively smaller arc radius, indicating that the covalent organic framework of this invention has a higher electron-hole separation efficiency; it also shows a relatively low emission peak in the steady-state PL spectrum, further confirming that the covalent organic framework prepared in this invention is relatively better in the separation and transport of photogenerated electron-hole pairs.

[0014] Secondly, the present invention provides a method for preparing the above-mentioned covalent organic framework having specific pyridine nitrogen sites, comprising the following steps:

[0015] 1,3,5-trialdehyde phloroglucinol and 2,2'-bipyridine-6,6'-diamine were mixed and dispersed in a reaction medium at a molar ratio of 1:(1~2), and a catalyst was added to form a pre-reaction system. After degassing the pre-reaction system, a covalent organic framework with specific pyridine nitrogen sites was prepared by a constant-temperature sealed reaction.

[0016] Preferably, the molar ratio of 1,3,5-trialdehyde phloroglucinol and 2,2'-bipyridine-6,6'-diamine is 1:1.5.

[0017] Experiments revealed that when the ratio of 1,3,5-trialdehyde phloroglucinol to 2,2'-bipyridine-6,6'-diamine is within the above-mentioned range, the yield of the prepared covalent organic framework is relatively high, and it exhibits relatively good catalytic degradation efficiency for sulfadiazine, with a relatively high rate of simultaneous hydrogen peroxide generation.

[0018] Preferably, the reaction medium is a mixture of 1,4-dioxane and mesitylene, wherein the volume ratio of 1,4-dioxane to mesitylene in the mixture is 1:(0.5-2).

[0019] The reaction medium formulated according to the compound ratio of the present invention has good solubility for the reaction raw materials 1,3,5-trialdehyde phloroglucinol and 2,2'-bipyridine-6,6'-diamine, which facilitates the smooth progress of the synthesis reaction. The synthesis yield of the product is relatively high, and the synthesized product exhibits relatively good catalytic degradation efficiency for sulfadiazine, with a relatively high rate of simultaneous hydrogen peroxide generation.

[0020] Preferably, the catalyst is a 3-9 mol / L aqueous solution of acetic acid; the volume ratio of the catalyst to the reaction medium is 1:(9.5-10.5).

[0021] Preferably, the reaction temperature of the constant-temperature sealed reaction is 100℃~140℃, and the reaction time is 48~72h.

[0022] Preferably, the process after the constant temperature and sealed reaction also includes a cleaning and drying process. The cleaning process involves extracting the reaction product with tetrahydrofuran for 12–48 hours. The drying process involves drying the extracted reaction product at 60–100°C for 12–48 hours.

[0023] Thirdly, the present invention provides the application of the above-mentioned covalent organic framework with specific pyridine nitrogen sites in the catalytic degradation of sulfadiazine and the simultaneous synthesis of hydrogen peroxide.

[0024] The optimal pyridine nitrogen position determines that the covalent organic framework TP-oBPy prepared in this invention exhibits relatively optimal photogenerated carrier separation efficiency compared to other COFs. Upon excitation by visible light, TP-oBPy generates photogenerated holes and electrons. On one hand, sulfadiazine acts as a hole trap, consuming photogenerated holes to promote the separation of photogenerated electrons, thereby generating a large number of superoxide radicals. On the other hand, sulfadiazine is partially degraded by the oxidation of holes. The photogenerated electrons combine with oxygen to generate a large number of superoxide radicals, which can be further converted into hydrogen peroxide or used to attack sulfadiazine. This gives TP-oBPy of this invention excellent performance in photocatalytic degradation of antibiotics and simultaneous generation of H2O2.

[0025] Preferably, a covalent organic framework with specific pyridine nitrogen sites is added to the solution containing sulfadiazine. After adsorption equilibrium is reached under dark conditions, the water is irradiated with visible light to photocatalytically degrade sulfadiazine and simultaneously synthesize hydrogen peroxide.

[0026] Experiments showed that the covalent organic framework prepared in this invention catalyzed the degradation of over 98% of sulfadiazine within 50 minutes; the simultaneous hydrogen peroxide generation rate during the catalytic degradation of sulfadiazine was 6776 μmol / g. -1 h -1 It has high application prospects in the fields of antibiotic degradation and H2O2 synthesis.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) The covalent organic framework TP-oBPy prepared by the present invention using 2,2'-bipyridine-6,6'-diamine as raw material has specific pyridine nitrogen sites. Compared with other covalent organic frameworks with pyridine nitrogen sites, the covalent organic framework TP-oBPy provided by the present invention has significant differences in charge density inside the covalent organic framework through the regulation of specific pyridine nitrogen sites, thereby establishing a high-strength electron donor-acceptor interaction in TP-oBPy, promoting the separation of photogenerated carriers, improving the utilization efficiency of photogenerated electrons, and having stronger photoresponse ability. It significantly improves the separation and transport efficiency of photogenerated charges, and further exhibits stronger photocatalytic degradation performance and the ability to simultaneously generate hydrogen peroxide.

[0029] (2) The covalent organic framework TP-oBPy prepared in this invention can act as a hole trap for sulfadiazine in photocatalysis, promoting the effective separation of photogenerated electrons. This allows more photogenerated electrons to participate in the synthesis of H2O2 and the formation of highly active free radical species for the degradation of sulfadiazine. In the photocatalytic system, it can also continue to catalyze the in-situ generated H2O2 to be converted into highly oxidizing free radicals that attack sulfadiazine, forming an effective dual-system promotion and recycling, which significantly improves the catalytic degradation efficiency of sulfadiazine. The catalytic degradation rate constant for sulfadiazine is (10.642±0.649)×10 -2 min -1 The method is superior to other reported catalysts. For an aqueous solution containing 50 mg / L sulfadiazine, adding 0.1 g / L of the covalent organic framework TP-oBPy prepared in this invention resulted in the catalytic degradation of over 98% of the sulfadiazine within 50 min. Furthermore, when treated in actual water bodies containing sulfadiazine, the catalytic degradation of over 90% of the sulfadiazine was achieved within 80 min. The covalent organic framework TP-oBPy prepared in this invention has high application prospects in the photocatalytic degradation of antibiotics.

[0030] (3) H2O2, as an environmentally friendly oxidant, is widely used in water environment remediation. However, traditional H2O2 synthesis methods (such as the anthraquinone method) still suffer from high energy consumption and low efficiency. The covalent organic framework of this invention, with specific pyridine nitrogen sites, generates a large amount of hydrogen peroxide simultaneously with the catalytic degradation of antibiotics. The simultaneous generation rate of hydrogen peroxide is as high as 6776 μmolg. - 1 h -1 The covalent organic framework TP-oBPy prepared by this invention has high application prospects in the fields of photocatalytic degradation of antibiotics and hydrogen peroxide synthesis. Attached Figure Description

[0031] Figure 1The synthesis path diagrams are for Example 1, Comparative Example 1, and Comparative Example 2;

[0032] Figure 2 The FT-IR spectra of Example 1, Comparative Example 1, and Comparative Example 2 are shown below.

[0033] Figure 3 The transient photocurrent response spectra of Example 1, Comparative Example 1, and Comparative Example 2 are shown.

[0034] Figure 4 Electrochemical impedance spectroscopy for Example 1, Comparative Example 1, and Comparative Example 2;

[0035] Figure 5 Steady-state PL spectra of Example 1, Comparative Example 1, and Comparative Example 2;

[0036] Figure 6 The graph shows the degradation curves of sulfadiazine and the simultaneous generation rate of H2O2 for Examples 1, 1, and 2.

[0037] Figure 7 The graph shows the degradation curves of sulfadiazine at different concentrations and the bar graph of the simultaneous generation rate of H2O2 in Example 1.

[0038] Figure 8 The graph shows the degradation curve of sulfadiazine in real water and the bar graph of the simultaneous generation rate of H2O2 in Example 1. Detailed Implementation

[0039] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Unless otherwise specified, the experimental methods used in the embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.

[0040] Example 1

[0041] This embodiment provides a covalent organic framework (TP-oBPy) with a specific pyridine nitrogen site, and its synthetic route is as follows: Figure 1 As shown, the specific preparation method includes the following steps:

[0042] 0.1 mmol (21.1 mg) of 1,3,5-trialdehyde phloroglucinol and 0.15 mmol (27.9 mg) of 2,2'-bipyridine-6,6'-diamine were added to a 10 mL Pyrex tube. 1 mL of a mixed solvent, consisting of 1,4-dioxane and mesitylene at a 1:1 volume ratio, was added to the Pyrex tube. The tube was sonicated for 15 minutes to ensure homogeneity of the reactants. 0.1 mL of an aqueous acetic acid solution (6 mol / L) was rapidly added to the Pyrex tube, and the tube was sonicated again to obtain a homogeneous dispersion. The Pyrex tube was then rapidly frozen at 77 K (liquid nitrogen bath) and degassed using a three-cycle freeze-pump-thaw cycle. The degassed Pyrex tube was sealed and heated at 120 °C for 72 hours. The reaction product was washed with tetrahydrofuran by Soxhlet extraction for 24 hours. Finally, the washed product was vacuum dried at 80 °C for 24 hours to obtain TP-oBPy.

[0043] The structure of TP-oBPy is represented by Formula I, which contains multiple repeating periodic structural units. The chemical structures of the periodic structural units are as follows:

[0044] In a periodic structural unit, “~” indicates an omitted identical periodic structural unit; that is, other identical periodic structural units are connected by the “-NH” site at the “~”.

[0045] Comparative Example 1

[0046] This comparative example provides a covalent organic framework (TP-pBPy), the synthetic route of which is as follows: Figure 1 As shown, the specific preparation method includes the following steps:

[0047] 0.1 mmol (21.1 mg) of 1,3,5-trialdehyde phloroglucinol and 0.15 mmol (27.9 mg) of 2,2'-bipyridine-4,4'-diamine were added to a 10 mL Pyrex tube. 1 mL of a mixed solvent (1,4-dioxane:trimethylbenzene = 1:1) was added to the Pyrex tube, and the mixture was sonicated for 15 minutes to ensure homogeneity. 0.1 mL of an aqueous acetic acid solution (6 mol / L) was rapidly added to the Pyrex tube, and the mixture was sonicated again to obtain a homogeneous dispersion. The Pyrex tube was then rapidly frozen at 77 K (liquid nitrogen bath) and degassed using a three-cycle freeze-pump-thaw cycle. The degassed Pyrex tube was sealed and heated at 120 °C for 72 hours. The reaction product was washed with tetrahydrofuran by Soxhlet extraction for 24 hours, and finally, the washed product was vacuum dried at 80 °C for 24 hours to obtain TP-pBPy.

[0048] The structure of TP-pBPy is represented by Formula II, which contains multiple repeating periodic structural units. The chemical structures of the periodic structural units are as follows:

[0049] The "~" in a periodic structural unit indicates an omitted identical periodic structural unit.

[0050] The difference between this comparative example and Example 1 lies in the different structures of the raw materials and products. This comparative example uses 2,2'-bipyridine-4,4'-diamine as one of the raw materials, which is different from 2,2'-bipyridine-6,6'-diamine in Example 1. As a result, the pyridine nitrogen sites in the covalent organic framework prepared are different.

[0051] Comparative Example 2

[0052] This comparative example provides a covalent organic framework (TP-mBPy), the synthetic route of which is as follows: Figure 1 As shown, the specific preparation method includes the following steps:

[0053] 0.1 mmol (21.1 mg) of 1,3,5-trialdehyde phloroglucinol and 0.15 mmol (27.9 mg) of 2,2'-bipyridine-5,5'-diamine were added to a 10 mL Pyrex tube. 1 mL of a mixed solvent (N,N-dimethylacetamide: o-dichlorobenzene = 3:1) was added to the Pyrex tube, and the mixture was sonicated for 15 minutes to ensure homogeneity. 0.1 mL of an aqueous acetic acid solution (6 mol / L) was rapidly added, and the mixture was sonicated again to obtain a homogeneous dispersion. The Pyrex tube was then rapidly frozen at 77 K (liquid nitrogen bath) and degassed using a three-cycle freeze-pump-thaw cycle. The Pyrex tube was sealed and heated at 120 °C for 72 hours. Soxhlet extraction with tetrahydrofuran was performed for 24 hours, and the final product was dried under vacuum at 80 °C for 24 hours to obtain TP-mBPy.

[0054] The structure of TP-TP-mBPy is represented by Formula III, which contains multiple repeating periodic structural units. The chemical structures of the periodic structural units are as follows:

[0055] The "~" in a periodic structural unit indicates that the same periodic structural unit is omitted.

[0056] The difference between this comparative example and Example 1 lies in the different structures of the raw materials and products. This comparative example uses 2,2'-bipyridine-5,5'-diamine as one of the raw materials, which is different from 2,2'-bipyridine-6,6'-diamine in Example 1. As a result, the pyridine nitrogen sites in the final covalent organic framework are different.

[0057] Performance testing

[0058] (1) Fourier transform infrared spectroscopy detection

[0059] The covalent organic frameworks prepared in Example 1, Comparative Example 1, and Comparative Example 2 were detected by Fourier transform infrared spectroscopy. Figure 2 As shown, in Example 1, TP-oBPy, in Comparative Example 1, TP-pBPy, and in Comparative Example 2, TP-mBPy all exhibit C=O(1602cm). -1 C = C(1557cm) -1 ) and CN (1258cm -1 The characteristic stretching vibrations of TP-oBPy and TP-pBPy were observed, which proved that Schiff base reaction and enol-ketone tautomerism occurred during the synthesis process, confirming the successful preparation of TP-oBPy, TP-pBPy and TP-mBPy.

[0060] (2) Transient photocurrent response spectrum detection

[0061] The transient photocurrent response spectra of the covalent organic frameworks prepared in Example 1, Comparative Example 1, and Comparative Example 2 were analyzed, and the results are as follows: Figure 3 As shown, under visible light irradiation, TP-oBPy in Example 1 exhibits a significantly higher transient photocurrent response compared to TP-pBPy in Comparative Example 1 and TP-mBPy in Comparative Example 2, indicating that TP-oBPy in Example 1 achieves more efficient electron-hole separation.

[0062] (3) Electrochemical impedance spectroscopy detection

[0063] Electrochemical impedance spectroscopy was performed on the covalent organic frameworks prepared in Example 1, Comparative Example 1, and Comparative Example 2. The results are as follows: Figure 4 As shown, compared with TP-pBPy in Comparative Example 1 and TP-mBPy in Comparative Example 2, TP-oBPy in Example 1 exhibits the smallest arc radius, indicating that the charge transfer resistance is lower and more conducive to electron-hole separation.

[0064] (4) Steady-state PL spectrum detection

[0065] Steady-state PL spectra of the covalent organic frameworks prepared in Example 1, Comparative Example 1, and Comparative Example 2 were analyzed. Figure 5 As shown, TP-pBPy in Comparative Example 1 and TP-mBPy in Comparative Example 2 have obvious emission peaks, while TP-oBPy in Example 1 shows a relatively low emission peak, proving that TP-oBPy in Example 1 has the lowest photogenerated carrier recombination rate and performs best in the separation and transport of photogenerated electron-hole pairs.

[0066] Application Example 1

[0067] 50 mL of sulfadiazine solution (50 mg / L) was added to a cylindrical quartz photocatalytic reactor. TP-oBPy from Example 1, TP-pBPy from Comparative Example 1, and TP-mBPy from Comparative Example 2 (all at a concentration of 0.1 g / L) were added to the reaction system. The mixture was stirred in the dark for 30 minutes to reach adsorption equilibrium of sulfadiazine, followed by 80 minutes of visible light irradiation. Samples were taken at predetermined time intervals and filtered through a 0.22 μm membrane filter. The residual concentration of sulfadiazine in the suspension was determined by high performance liquid chromatography, and the concentration of hydrogen peroxide generated simultaneously was determined by iodometric titration.

[0068] The degradation rates of sulfadiazine under different treatments are as follows: Figure 6 As shown in Figure a, compared to Comparative Examples 2 and 3, the TP-oBPy prepared in Example 1 can achieve over 98% photocatalytic degradation of sulfadiazine within 50 minutes, demonstrating superior catalytic degradation efficiency compared to Comparative Examples 2 and 3. The catalytic degradation rate constant of sulfadiazine by TP-oBPy prepared in Example 1 is (10.642 ± 0.649) × 10⁻⁶. -2 min -1 It outperforms other reported catalysts in catalytic degradation efficiency of sulfadiazine.

[0069] The rates of simultaneous hydrogen peroxide generation for different treatments at 60 min are as follows: Figure 6 As shown in b, the rate of simultaneous hydrogen peroxide generation during the catalytic degradation of sulfadiazine by TP-oBPy prepared in Example 1 was significantly better than that in Comparative Examples 1 and 2. During the catalytic degradation process of TP-oBPy prepared in Example 1, the simultaneous hydrogen peroxide generation rate reached 6776 μmol g. -1 h -1 It was 1.87 times that of Comparative Example 1 and 2.3 times that of Comparative Example 2, showing the best photocatalytic effect.

[0070] Application Example 2

[0071] 50 mL of sulfadiazine solutions of different concentrations (50 mg / L, 75 mg / L, and 100 mg / L) were added to a cylindrical quartz photocatalytic reactor. TP-oBPy (0.1 g / L in each case) from Example 1 was added to the reaction system. The system was stirred in the dark for 30 minutes to reach adsorption equilibrium of sulfadiazine, followed by 80 minutes of visible light irradiation. Samples were taken at predetermined time intervals and filtered through a 0.22 μm membrane filter. The residual concentration of sulfadiazine in the suspension was determined by high performance liquid chromatography, and the concentration of hydrogen peroxide generated simultaneously was determined by iodometric titration.

[0072] The degradation rates of sulfadiazine under different treatments are as follows: Figure 7As shown in Figure a, for sulfadiazine solutions with concentrations of 50 mg / L, 75 mg / L, and 100 mg / L, TP-oBPy can achieve highly efficient degradation of 98.96%, 96.20%, and 89.45% of sulfadiazine, respectively, within 80 minutes, while simultaneously generating at least 4830 μmolg g of sulfadiazine. -1 h -1 The H2O2 exhibits excellent concentration adaptability.

[0073] Application Example 3

[0074] 50 mL of sulfadiazine solutions (50 mg / L) prepared from ultrapure water (UW), tap water (TW), actual sewage inflow (ASI), and actual sewage effluent (ASE), respectively, were added to a cylindrical quartz photocatalytic reactor. TP-oBPy (0.1 g / L) from Example 1 was added to the reaction system. The mixture was stirred in the dark for 30 minutes to reach adsorption equilibrium of sulfadiazine, followed by 80 minutes of visible light irradiation. Samples were taken at predetermined time intervals and filtered through a 0.22 μm membrane filter. The residual concentration of sulfadiazine in the suspension was determined by high-performance liquid chromatography (HPLC), and the concentration of hydrogen peroxide generated simultaneously was determined by iodometric titration.

[0075] Photocatalytic experiments of sulfadiazine were conducted using TP-oBPy in different types of water. The results of the degradation rate of sulfadiazine and the simultaneous generation rate of hydrogen peroxide are as follows: Figure 8 As shown, the degradation effect of sulfadiazine in wastewater effluent after 80 minutes is comparable to that in ultrapure water. The wastewater influent (ASI) has a certain impact on photocatalysis, mainly because the high concentration of organic matter in the actual water consumes the active species of the system. However, more than 90% of the sulfadiazine is still degraded within 80 minutes. The treatment effect of the sulfadiazine solution prepared from the wastewater influent is comparable to that of the sulfadiazine in tap water. The above results prove that TP-oBPy is feasible in actual wastewater treatment and has high application prospects.

[0076] Example 2

[0077] The purpose of this embodiment is to analyze the effect of the ratio of the raw materials 1,3,5-trialdehyde phloroglucinol and 2,2'-bipyridine-6,6'-diamine on the performance of the final TP-oBPy and its degradation effect on sulfadiazine. The specific experimental methods are as follows:

[0078] 1,3,5-Trialdehyde-resorcinol and 2,2'-bipyridine-6,6'-diamine were added to a 10 mL Pyrex tube. 1 mL of a mixed solvent, consisting of 1,4-dioxane and mesitylene at a 1:1 volume ratio, was added to the Pyrex tube. The tube was sonicated for 15 minutes to ensure homogeneity of the reactants. 0.1 mL of an aqueous acetic acid solution (6 mol / L) was rapidly added to the Pyrex tube, and the tube was sonicated again to obtain a homogeneous dispersion. The Pyrex tube was then rapidly frozen at 77 K (liquid nitrogen bath) and degassed using a three-cycle freeze-pump-thaw cycle. The degassed Pyrex tube was sealed and heated at 120 °C for 72 hours. The reaction product was washed with tetrahydrofuran by Soxhlet extraction for 24 hours. Finally, the washed product was vacuum dried at 80 °C for 24 hours to obtain TP-oBPy. The amounts of 1,3,5-trialdehyde phloroglucinol and 2,2'-bipyridine-6,6'-diamine added are shown in Table 1. In addition, the prepared product was subjected to sulfadiazine catalytic degradation experiments according to the method described in Application Example 1. The degradation rate of sulfadiazine and the synchronous synthesis rate of hydrogen peroxide after 80 min of treatment are recorded in Table 1.

[0079] Table 1. Amount of raw materials, degradation rate of sulfadiazine by the products, and simultaneous synthesis rate of hydrogen peroxide.

[0080]

[0081]

[0082] As shown in Table 1, the product prepared by 1,3,5-trialdehyde phloroglucinol and 2,2'-bipyridine-6,6'-diamine in a molar ratio of 1:(1-2) exhibits better catalytic degradation efficiency for sulfadiazine, especially when the ratio of the two is 1:1.5, the product prepared has the best catalytic degradation efficiency for sulfadiazine.

[0083] Example 3

[0084] The purpose of this embodiment is to analyze the influence of the reaction medium on the performance of the prepared product during the preparation of covalent organic frameworks. The specific experimental method is as follows:

[0085] 0.1 mmol (21.1 mg) of 1,3,5-trialdehyde phloroglucinol and 0.15 mmol (27.9 mg) of 2,2'-bipyridine-6,6'-diamine were added to a 10 mL Pyrex tube. 1 mL of a mixed solvent (as shown in Table 2) was added to the Pyrex tube. The tube was sonicated for 15 minutes to ensure homogeneous mixing of the reactants. 0.1 mL of an aqueous acetic acid solution (6 mol / L) was rapidly added to the Pyrex tube, and the tube was sonicated again to obtain a homogeneous dispersion. The Pyrex tube was then rapidly frozen at 77 K (liquid nitrogen bath) and degassed using a three-cycle freeze-pump-thaw cycle. The degassed Pyrex tube was sealed and heated at 120 °C for 72 hours. The reaction product was washed with tetrahydrofuran by Soxhlet extraction for 24 hours. Finally, the washed product was vacuum dried at 80 °C for 24 hours to obtain TP-oBPy. The composition of the mixed solvent is shown in Table 2. The prepared product was subjected to sulfadiazine catalytic degradation experiments according to the method described in Application Example 1. The degradation rate of sulfadiazine and the synchronous synthesis rate of H2O2 after 80 min of treatment were recorded in Table 2.

[0086] Table 2. Composition of the mixed solvent and the degradation rate of sulfadiazine by the products.

[0087]

[0088] As shown in Table 2, when the reaction medium consists of 1,4-dioxane and mesitylene in a volume ratio of 1:(0.5-2), the prepared reaction product has a relatively good catalytic degradation efficiency for sulfadiazine. In particular, when the volume ratio of the two is 1:1, the prepared reaction product has the best catalytic degradation effect on sulfadiazine.

Claims

1. A covalent organic framework having specific pyridine nitrogen sites, characterized in that, The covalent organic framework is prepared from 1,3,5-trialdehyde phloroglucinol and 2,2'-bipyridine-6,6'-diamine. The structure of the covalent organic framework is composed of periodic structural units, and the structural formula of the periodic structural units is as follows: Wherein, "~" represents the connection point between multiple periodic structural units.

2. A method for preparing a covalent organic framework having a specific pyridine nitrogen site as described in claim 1, characterized in that, Includes the following steps: 1,3,5-trialdehyde phloroglucinol and 2,2'-bipyridine-6,6'-diamine were mixed and dispersed in a reaction medium at a molar ratio of 1:(1~2), and a catalyst was added to form a pre-reaction system. After degassing the pre-reaction system, a covalent organic framework with specific pyridine nitrogen sites was prepared by a constant-temperature sealed reaction.

3. The preparation method according to claim 2, characterized in that, The molar ratio of 1,3,5-trialdehyde phloroglucinol and 2,2'-bipyridine-6,6'-diamine is 1:1.

5.

4. The preparation method according to claim 2, characterized in that, The reaction medium is a mixture of 1,4-dioxane and mesitylene, wherein the volume ratio of 1,4-dioxane to mesitylene in the mixture is 1:(0.5-2).

5. The preparation method according to claim 2, characterized in that, The catalyst is a 3-9 mol / L aqueous solution of acetic acid; the volume ratio of the catalyst to the reaction medium is 1:(9.5-10.5).

6. The preparation method according to claim 2, characterized in that, The constant temperature sealed reaction has a reaction temperature of 100℃~140℃ and a reaction time of 48~72h.

7. The preparation method according to claim 2, characterized in that, The constant-temperature sealed reaction also includes a cleaning and drying process. The cleaning process involves extracting the reaction product with tetrahydrofuran for 12–48 hours. The drying process involves drying the extracted reaction product at 60–100°C for 12–48 hours.

8. The application of the covalent organic framework with a specific pyridine nitrogen site as described in claim 1 in the catalytic degradation of sulfadiazine and the simultaneous synthesis of hydrogen peroxide.

9. The application according to claim 8, characterized in that, The covalent organic framework with specific pyridine nitrogen sites was introduced into the solution containing sulfadiazine. After adsorption equilibrium was reached under dark conditions, the water was irradiated with visible light to photocatalytically degrade sulfadiazine and simultaneously synthesize hydrogen peroxide.

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