Covalent organic framework, preparation method thereof and wastewater treatment method

Abstract

The invention relates to the technical field of organic framework materials, in particular to a covalent organic framework, a preparation method thereof and a wastewater treatment method. The preparation method of the covalent organic framework comprises the following steps: mixing tetra-(4-aminobenzene) ethylene, terephthalaldehyde, an acidity regulator and a solvent to obtain a mixed solution; carrying out solution stirring reaction on the mixed solution, and carrying out purification treatment to obtain a covalent organic framework; the stirring reaction temperature of the solution is 10-120 DEG C, and the stirring reaction time is 1-12 hours; the molar ratio of the tetra-(4-aminobenzene) ethylene to the acidic regulator is 1: (60-300). The method has the advantages that the operation is simple, the condition is mild, and large-scale synthesis is easy to realize, and the product has the characteristics of high crystallinity, high porosity, high stability and the like, so that the adsorption capacity of the organic dye can reach 2500mg / g or above, and the organic dye in wastewater can be basically adsorbed within 1min.

Description

Technical Field

[0001] This application relates to the technical field of organic framework materials, and in particular to a covalent organic framework, a method for its preparation, and a method for treating wastewater. Background Technology

[0002] Covalent organic frameworks (COFs) are crystalline porous organic polymers with well-defined two-dimensional or three-dimensional structures, using small organic molecules as structural units linked by strong covalent bonds. COFs possess characteristics such as high crystallinity, high porosity, and high stability, making them widely applicable as adsorbents in water treatment fields, such as seawater desalination, removal of heavy metal ions, and removal of organic pollutants.

[0003] Cofer oxides (COFs) can be synthesized through methods such as solvothermal synthesis, ionothermal synthesis, microwave heating synthesis, and interfacial synthesis. Among these, solvothermal synthesis is the primary method, but it typically requires high temperatures (120℃~150℃) and long reaction times (3-7 days), and is also quite cumbersome. Currently, a simpler method with lower reaction temperatures and shorter reaction times is lacking for synthesizing COFs with high crystallinity, high porosity, and high stability. Summary of the Invention

[0004] Therefore, it is necessary to provide a covalent organic framework, its preparation method, and a wastewater treatment method to address the current lack of a simple method for synthesizing COFs with high crystallinity, high porosity, and high stability with low reaction temperature and short reaction time.

[0005] The above-mentioned objective of this application is achieved through the following technical solution: In a first aspect, this application provides a method for preparing a covalent organic framework, comprising the following steps: A mixture of tetra-(4-aminophenyl)ethylene, terephthalaldehyde, an acid regulator, and a solvent is obtained. The mixture is subjected to solution stirring reaction and then purified to obtain the covalent organic framework; The temperature of the solution stirring reaction is 10 ℃~120 ℃, and the time is 1 h~12 h; The molar ratio of the tetra-(4-aminophenyl)ethylene to the acid modifier is 1:(60~300).

[0006] In one embodiment, the molar ratio of tetra-(4-aminophenyl)ethylene to terephthalaldehyde is 1:(1.5~2.5).

[0007] In one embodiment, the acidity regulator includes one or more of formic acid, acetic acid, propionic acid, butyric acid, and trifluoroacetic acid.

[0008] In one embodiment, the acid regulator is provided in the form of an acid solution, wherein the concentration of the acid regulator in the acid solution is 3 mol / L to 15 mol / L.

[0009] In one embodiment, the solvent includes water, tetrahydrofuran, dimethyl sulfoxide, 1,4-dioxane, cyclohexane, and N , N One or more of dimethylformamide.

[0010] In one embodiment, the purification process includes one or more of the following: filtration, washing, Soxhlet extraction, and drying.

[0011] In one embodiment, the yield of the covalent organic framework is 0.07 g to 3.1 g, with a yield of ≥60%.

[0012] In a second aspect, this application provides a covalent organic framework, which is prepared using the covalent organic framework preparation method described above.

[0013] In one embodiment, the BET specific surface area of ​​the covalent organic framework is ≥1800 m². 2 / g.

[0014] In one embodiment, the covalent organic framework has a first pore size of 2.4 nm to 2.5 nm and a second pore size of 0.5 nm to 0.6 nm.

[0015] In one embodiment, the thermal decomposition temperature of the covalent organic framework is ≥400 °C.

[0016] In one embodiment, the covalent organic framework remains structurally stable in solutions with pH values ​​of 3 to 12.

[0017] In one embodiment, the covalent organic framework has a maximum adsorption capacity for Congo red ≥2500 mg / g.

[0018] In one embodiment, an adsorption filtration experiment was conducted on a Congo red solution with a concentration of 800 mg / L using 5 mg of the covalent organic framework, and the Congo red removal rate reached over 99% within 1 minute.

[0019] A third aspect of this application provides a wastewater treatment method, comprising the following steps: The covalent organic framework described above was placed in wastewater containing organic dyes for adsorption treatment.

[0020] This application has at least the following beneficial effects: This application synthesizes covalent organic frameworks using a simplified solution stirring method. This method has significantly lower reaction temperature, reaction time, and operational difficulty compared to traditional solvothermal synthesis methods, offering advantages such as simple operation, mild conditions, and ease of large-scale synthesis. Compared to traditional techniques, this application increases the amount of acid regulator, enabling it not only to act as a catalyst to promote the forward reaction but also to adjust the pH value of the reaction system during solution stirring. This improves the yield, efficiency, and crystallinity of the covalent organic framework, resulting in a more regular pore structure, superior specific surface area, and better stability. Consequently, it significantly enhances the adsorption performance for organic dyes, laying an industrial foundation for the application of two-dimensional COF materials in water treatment. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic flowchart of a method for preparing TAPE-COF in one embodiment; Figure 2 This is a synthetic route diagram of TAPE-COF in one embodiment; Figure 3 The PXRD time-monitored spectrum of the product of Example 1; Figure 4 The PXRD time-monitored spectrum of the product of Example 2; Figure 5 A photograph of the product of Example 3; Figure 6 The image shows a comparison of PXRD patterns of the products from Examples 1-3 and the product from Comparative Example 1. Figure 7 PXRD comparison images of the products of Example 1, Example 4 and Comparative Example 2; Figure 8 SEM image of the product of Example 1; Figure 9 SEM image of TAPE-COF prepared by the solvothermal synthesis method as reported in the literature; Figure 10 TEM image of the product of Example 1; Figure 11The following are FTIR chromatograms of the product and two reactants from Example 1; Figure 12 The TGA images of the product of Example 1 before and after activation are shown. Figure 13 The PXRD images of the product of Example 1 after soaking in solutions of different pH values ​​for 200 min are shown. Figure 14 The N2 adsorption-desorption isotherm of the product of Example 1; Figure 15 The image shows the Congo red adsorption isotherm of the product from Example 1. Figure 16 The diagram shows the Congo red cycling experiment of the product of Example 1; Figure 17 A comparative graph showing the adsorption and filtration effects of the product of Example 1, activated carbon, silica gel, molecular sieve, and COF-300 on Congo red. Figure 18 The graph shows a comparison of the effects of adsorption and filtration on the Congo red dye solution before treatment, and on the products of Examples 1-2 and Comparative Example 1. Figure 19 This is a comparison diagram of the adsorption and filtration of the mixed dye by the product of Example 1 before and after adsorption. Detailed Implementation

[0023] To facilitate understanding of this application, the following detailed description is provided in conjunction with specific embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0025] In this application, "and / or" means any and all combinations of one or more of the related listed items. "At least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two, three, etc., unless otherwise expressly and specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise expressly and specifically defined.

[0026] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all subranges to which they are included.

[0027] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0028] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0029] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0030] In this application, room temperature refers to indoor temperature, normal temperature, or general temperature. Generally, room temperature can be any of the following temperature ranges: 23 ℃ ± 2 ℃, 25 ℃ ± 5 ℃, or 20 ℃ ± 5 ℃.

[0031] One of the significant differences between two-dimensional (2D) and three-dimensional (3D) COF materials is the presence of a fixed porosity, which opens up a wide range of applications for 2D COF materials. Using tetrakis(4-aminophenyl)ethene (TAPE) and terephthalaldehyde (TPA) as structural building blocks, a 2D COF material—TAPE-based covalent organic framework, or TAPE-COF for short—can be constructed. TAPE-COF possesses both micropores and mesopores, resulting in different pore environments that provide diverse adsorption sites, potentially enabling the adsorption of a wider variety of organic dyes, thus making it stand out among 2D COFs.

[0032] Solvothermal synthesis via sealed tubes is currently the main method for synthesizing tape-cof. This traditional solvothermal synthesis method not only requires degassing via a refrigerated pump, making the operation cumbersome, but also necessitates a long reaction time at high temperatures (120°C, 4 days). Furthermore, this synthesis method is not suitable for large-scale synthesis, greatly limiting the practical application of the material.

[0033] Based on this, in the first aspect of this application, a method for preparing covalent organic frameworks is provided to overcome the shortcomings of traditional solvothermal synthesis methods, such as harsh reaction conditions, cumbersome operation, and difficulty in achieving large-scale synthesis, and to enable the product to exhibit characteristics such as high crystallinity, high porosity, and high stability.

[0034] Please see Figures 1-2 , Figure 1 This is a schematic flowchart illustrating the preparation method of a covalent organic framework in one embodiment. Figure 2 This is a synthetic route diagram for a covalent organic framework in one embodiment. For example... Figures 1-2 As shown, the method for preparing a covalent organic framework includes the following steps: S100: Mix tetra-(4-aminophenyl)ethylene (TAPE), terephthalaldehyde (TPA), acid regulator and solvent to obtain a mixed solution; S200: The mixture is subjected to solution stirring reaction and then purified to obtain a covalent organic framework, denoted as TAPE-COF; The temperature of the solution stirring reaction was 10 ℃~120 ℃, and the time was 1 h~12 h; The molar ratio of tetra-(4-aminophenyl)ethylene (TAPE) to acid modifier is 1:(60~300).

[0035] This application synthesizes covalent organic frameworks using a simplified solution stirring method. This method has significantly lower reaction temperature, reaction time, and operational difficulty compared to traditional solvothermal synthesis methods, offering advantages such as simple operation, mild conditions, and ease of large-scale synthesis. Compared to traditional techniques, this application increases the amount of acid regulator, enabling it not only to act as a catalyst to promote the forward reaction but also to adjust the pH value of the reaction system during solution stirring. This improves the yield, efficiency, and crystallinity of TAPE-COF, resulting in a more regular pore structure, superior specific surface area, and better stability. Consequently, it significantly enhances the adsorption performance for organic dyes, laying an industrial foundation for the application of two-dimensional COF materials in water treatment.

[0036] As an example, the temperature of the solution stirring reaction can be 10 ℃, 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃ or 120 ℃, and can be further selected as 50 ℃~80 ℃.

[0037] As an example, the reaction time for stirring the solution can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h or 12 h, and can be further selected as 4 h to 8 h.

[0038] As an example, the molar ratio of tape to acid regulator can be 1:60, 1:80, 1:100, 1:120, 1:140, 1:160, 1:180, 1:1:200, 1:210, 1:220, 1:230, 1:240, 1:250, 1:260, 1:270, 1:280, 1:290 or 1:300, and can be further selected as 1:(240~260).

[0039] Optionally, the molar ratio of tetra-(4-aminostyrene)ethylene (TAPE) to terephthalaldehyde (TPA) is 1:(1.5~2.5). As an example, the molar ratio of TAPE to TPA can be 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.4 or 1:2.5, and more preferably 1:(1.9~2.1).

[0040] Optionally, the acidity regulator includes one or more of formic acid, acetic acid, propionic acid, butyric acid, and trifluoroacetic acid, and is further optionally acetic acid.

[0041] Optionally, the acid regulator is provided in the form of an acid solution, with a concentration of 3 mol / L to 15 mol / L in the acid solution.

[0042] As an example, the concentration of the acid regulator in the acid solution can be 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, 14 mol / L or 15 mol / L, and can be further selected as 10 mol / L to 15 mol / L.

[0043] As examples, solvents include water, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), 1,4-dioxane, cyclohexane, and... N , NOne or more of dimethylformamide (DMF), and further optionally THF.

[0044] In this application, the reactants do not need to completely dissolve to form a homogeneous solution. As the reaction proceeds, the reactants are continuously transformed into products, while simultaneously dissolving to maintain the dynamic equilibrium of the reaction. When water is used as the solvent, the solution-stirred reaction is a heterogeneous reaction, actually occurring at the solid-liquid interface or emulsion interface. Vigorous stirring and heating can effectively promote collisions and rapid reactions between reactants. Furthermore, organic acids such as acetic acid can solubilize and activate the reactants, improving their dispersibility and reactivity in water, and promoting the dynamic equilibrium of the solution-stirred reaction.

[0045] Optionally, the purification process includes one or more of the following: filtration, washing, Soxhlet extraction, and drying.

[0046] Optionally, the purification process includes the following steps: after the solution is stirred and reacted, the solid product and the mother liquor are separated by vacuum filtration, and the solid product is repeatedly washed with solvent, then vacuum filtered and dried to obtain an orange-yellow powder product (TAPE-COF).

[0047] Optionally, before using TAPE-COF, the powdered product is placed in a Soxhlet extractor and extracted with solvent for 2 to 5 days, and finally heated and vacuumed at 80 to 120 °C for 8 to 16 hours.

[0048] As an example, the Soxhlet extraction time can be 2 days, 2.5 days, 3 days, 3.5 days, 4 days, 4.5 days, or 5 days, and more preferably 3 days; the drying temperature can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or 120°C, and more preferably 110°C; the drying time can be 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or 16 hours, and more preferably 12 hours.

[0049] Optionally, the yield of TAPE-COF is 0.07 g to 3.1 g, with a yield of ≥60%.

[0050] Traditional solvothermal synthesis methods typically involve placing reactants, solvents, and catalysts in a closed system within a Pyrex glass tube or high-pressure reactor. Limited by the size of the reaction apparatus and safety concerns, solvothermal synthesis is difficult to scale up, with yields mostly in the milligram range. This makes it unsuitable for large-scale industrial synthesis of tape-co-fi (TAPE-COF), significantly restricting the material's applications. In contrast, the simplified solution-stirring synthesis method provided in this application not only enables milligram-level synthesis but can also scale up the synthesis by tens of times to achieve gram-level synthesis, while maintaining high yield and purity, thus laying an industrial foundation for the material's application.

[0051] As an example, the yield of TAPE-COF can be 0.07 g, 0.08 g, 0.09 g, 0.1 g, 0.2 g, 0.5 g, 0.8 g, 1 g, 1.2 g, 1.5 g, 1.8 g, 2 g, 2.2 g, 2.4 g, 2.5 g, 2.8 g, 3 g, or 3.1 g.

[0052] As an example, the yield of TAPE-COF can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 92%.

[0053] In a second aspect, this application provides a covalent organic framework, which is prepared using the covalent organic framework preparation method described above.

[0054] Optionally, the BET specific surface area of ​​Tape-COF is ≥1800 m². 2 / g.

[0055] Optionally, TAPE-COF has a first pore size and a second pore size, wherein the first pore size is 2.4 nm to 2.5 nm and the second pore size is 0.5 nm to 0.6 nm.

[0056] Optionally, the thermal decomposition temperature of TAPE-COF is ≥400 ℃.

[0057] Optionally, TAPE-COF remains structurally stable in solutions with pH values ​​of 3 to 12.

[0058] Optionally, the maximum adsorption capacity of TAPE-COF for Congo red is ≥2500 mg / g; Optionally, an adsorption filtration experiment was conducted using 5 mg of TAPE-COF on a Congo red solution with a concentration of 800 mg / L, and the Congo red removal rate reached over 99% within 1 minute.

[0059] A third aspect of this application provides a wastewater treatment method, comprising the following steps: The covalent organic framework described above was placed in wastewater containing organic dyes for adsorption treatment.

[0060] Alternatively, the organic dyes include one or more of Congo Red, Crystal Violet, Brilliant Green, Soap Yellow, Basic Fuchs Red, Reactive Brilliant Blue, Methylene Orange, and Methylene Blue.

[0061] Optionally, the organic dye content in the wastewater is 10 mg / L to 800 mg / L, for example, 10 mg / L, 20 mg / L, 50 mg / L, 80 mg / L, 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, 500 mg / L, 600 mg / L, 700 mg / L or 800 mg / L.

[0062] Optionally, the dosage of TAPE-COF is 1.5 mg / mL to 6.25 mg / mL, such as 1.5 mg / mL, 2 mg / mL, 2.5 mg / mL, 3 mg / mL, 3.5 mg / mL, 4 mg / mL, 4.5 mg / mL, 5 mg / mL, 5.5 mg / mL, 6 mg / mL or 6.25 mg / mL.

[0063] Optionally, the adsorption treatment includes the following steps: placing TAPE-COF in wastewater containing organic dyes and then subjecting it to ultrasonic treatment; or dispersing TAPE-COF in wastewater containing organic dyes by ultrasonication and then subjecting it to static adsorption treatment.

[0064] Optionally, the removal rate of organic dyes in wastewater is ≥96.5%.

[0065] The following detailed description, along with specific embodiments and comparative examples, further illustrates the process. Unless otherwise specified, all raw materials and instruments used in these embodiments and comparative examples are commercially available. Unless otherwise specified, all processes involved are conventionally chosen by those skilled in the art. The sources of some raw materials are as follows: Table 1. Reagents used in the synthesis and characterization of TAPE-COF Example 1 This embodiment uses a simple solution stirring method to synthesize TAPE-COF, and the preparation method is as follows: Accurately weigh 75.9 mg (0.194 mmol) tetra-(4-aminophenyl)ethylene (TAPE) and 52.0 mg (0.388 mmol) terephthalaldehyde (TPA) and place them in a clean 50 mL round-bottom flask. Add 10 mL of tetrahydrofuran (THF) and dissolve completely. Place the flask on a preheated 65 °C stirring table, then add 4 mL of acetic acid solution (AcOH, 12 mol / L, 48 mmol) as an acidity regulator. Maintain the reaction under reflux with stirring for 9 h. After the reaction is complete, separate the solid product and mother liquor by vacuum filtration. Wash the solid product repeatedly with THF, filter and dry to obtain an orange-yellow powder product (TAPE-COF). Before adsorption treatment, place the powder product in a Soxhlet extractor and extract with THF for 3 days. Finally, heat at 100 °C under vacuum for 12 h (yield: 74.3 mg; yield: 65.2%, calculated based on reactant TAPE).

[0066] Example 2 This embodiment is basically the same as embodiment 1, except that the temperature of the heating stirring table is set to 25 ℃.

[0067] Example 3 This embodiment uses a simple solution stirring method to synthesize TAPE-COF, and the preparation method is as follows: Accurately weigh 2.277 g (5.8 mmol) tetra-(4-aminophenyl)ethylene (TAPE) and 1.560 g (11.6 mmol) terephthalaldehyde (TPA) and place them in a clean 1000 mL round-bottom flask. Add 300 mL of tetrahydrofuran (THF) and dissolve completely. Place the flask on a preheated 65 °C stirring table, then add 120 mL of acetic acid solution (AcOH, 12 mol / L, 1440 mmol) as an acidity regulator. Maintain the reaction under reflux with stirring for 9 h. After the reaction is complete, separate the solid product and mother liquor by vacuum filtration. Wash the solid product repeatedly with THF, filter and dry to obtain an orange-yellow powder product (TAPE-COF). Before adsorption treatment, place the powder product in a Soxhlet extractor and extract with THF for 3 days. Finally, heat at 100 °C under vacuum for 12 h (yield: 3.14 g; yield: 92%, calculated based on reactant TAPE).

[0068] Example 4 This embodiment uses a simple solution stirring method to synthesize TAPE-COF, and the preparation method is as follows: Accurately weigh 75.9 mg (0.194 mmol) tetra-(4-aminophenyl)ethylene (TAPE) and 52.0 mg (0.388 mmol) terephthalaldehyde (TPA) and place them in a clean 50 mL round-bottom flask. Add 10 mL of tetrahydrofuran (THF) and dissolve completely. Place the flask on a preheated 65 °C stirring table, then add 4 mL of acetic acid solution (AcOH, 3 mol / L, 12 mmol) as an acidity regulator. Maintain the reaction under reflux with stirring for 9 h. After the reaction is complete, separate the solid product and mother liquor by vacuum filtration. Wash the solid product repeatedly with THF, filter and dry to obtain an orange-yellow powder product (TAPE-COF).

[0069] Example 5 This embodiment is basically the same as Embodiment 1, except that formic acid is used as the acid regulator.

[0070] Example 6 This embodiment is basically the same as Example 1, except that the solvent used is dimethyl sulfoxide.

[0071] Comparative Example 1 This comparative example uses a traditional solvothermal method to prepare TAPE-COF, and the preparation method is as follows: Accurately weigh 60 mg (0.15 mmol) tetra-(4-aminophenyl)ethylene (TAPE) and 41 mg (0.3 mmol) terephthalaldehyde (TPA), place them in a clean Pyrex glass tube, add 2 mL of 1,4-dioxane, and after complete dissolution, add 0.2 mL of acetic acid solution (AcOH, 6 mol / L, 1.2 mmol) as a catalyst. After freezing in a liquid nitrogen bath, degas for 10 min, then purge with nitrogen for 10 min, repeating this cycle twice. After sealing, place the glass tube in a preheated 120 °C oven for 4 days. After the reaction, separate the solid product and mother liquor by vacuum filtration, repeatedly wash the solid product with tetrahydrofuran, filter and dry to obtain an orange-yellow powder product (TAPE-COF). Before adsorption treatment, place the powder product in a Soxhlet extractor and extract with tetrahydrofuran for 3 days, finally heating at 100 °C under vacuum for 12 h.

[0072] Comparative Example 2 This comparative example uses a simple solution stirring method to synthesize TAPE-COF, and the preparation method is as follows: Accurately weigh 75.9 mg (0.194 mmol) tetra-(4-aminophenyl)ethylene (TAPE) and 52.0 mg (0.388 mmol) terephthalaldehyde (TPA) and place them in a clean 50 mL round-bottom flask. Add 10 mL of tetrahydrofuran (THF) and dissolve completely. Place the flask on a preheated 65 °C stirring table, then add 0.25 mL of acetic acid solution (AcOH, 6 mol / L, 1.5 mmol) as an acidity regulator. Maintain the reaction under reflux with stirring for 9 h. After the reaction is complete, separate the solid product and mother liquor by vacuum filtration. Wash the solid product repeatedly with THF, filter and dry to obtain an orange-yellow powder.

[0073] Test case 1. Powder X-ray diffraction (PXRD): To determine the time required for the synthesis of TAPE-COF using a simplified solution stirring method, PXRD characterization was employed to monitor the crystallinity of the products obtained in Examples 1 and 2 at different reaction times. A Rigaku MiniFlex 600 X-ray diffractometer (Cu Kα) was used. λ Data were collected at 1.5418 Å, with the 2θ range set to 2.2°–30°, a step size of 0.02°, and a scan rate of 10° / min. Results are shown in […]. Figure 3 and Figure 4 .like Figure 3 As shown, in Example 1, a crystalline product formed after reacting at 65 °C for 1 h. Figure 4 As shown, in Example 2, the reaction was carried out directly at room temperature, and a product with good crystallinity could also be obtained by extending the reaction time.

[0074] Example 3 scaled up the reaction by 30 times (single synthesis >3 g, calculated based on reactant TAPE), and the resulting product is as follows: Figure 5 As shown in the figure. The PXRD spectrum was compared with that of Comparative Example 1, which was obtained by the conventional solvothermal method after 4 days of reaction. The results are as follows. Figure 6 As shown, the product synthesized on a large scale still has good crystallinity, proving that the simple solution stirring method provided in this application has good reproducibility and is suitable for large-scale synthesis.

[0075] In Example 1, the molar ratio of tape to acetic acid was approximately 1:247; in Example 4, the amount of acetic acid was reduced, and the molar ratio of tape to acetic acid was approximately 1:62; in Comparative Example 2, the amount of acetic acid was further reduced, and the molar ratio of tape to acetic acid was approximately 1:8. The products from Examples 1, 4, and 2 were subjected to PXRD testing, and the results are as follows: Figure 7As shown, the products of Examples 1 and 4 still have good crystallinity, while the product of Comparative Example 2 does not have a crystalline state. This demonstrates that, under conditions where the molar ratio of TAPE to acetic acid is comparable, the traditional solvothermal method can synthesize a crystalline product within a 4-day reaction time, while the simple solution stirring method cannot synthesize a crystalline product within a 9-hour reaction time. Therefore, controlling the molar ratio of TAPE to acid regulator at 1:(60~300) is key to the rapid synthesis of highly crystalline TAPE-COF using the simple solution stirring method.

[0076] 2. Scanning electron microscope (SEM) and transmission electron microscope (TEM) The product from Example 1 was ultrasonically dispersed in THF, then dropped onto a silicon wafer and gold-plated. The resulting product was then tested using a Zeiss Gemini 300 field emission scanning electron microscope. The results are shown in [Figure number missing]. Figure 8 .like Figure 8 As shown, the product exhibits a regular granular shape, rather than the two-dimensional sheet-like shape of products from the traditional solvothermal method (e.g., Figure 9 (As shown), this may be attributed to continuous stirring during the reaction process.

[0077] The product of Example 1 was ultrasonically dispersed in THF, dropped onto a Cu mesh, and after the THF had completely evaporated, it was tested using a JEM-F200 transmission electron microscope. The results are shown in [Figure number missing]. Figure 10 .like Figure 10 As shown, the ordered lattice fringes further confirm the high crystallinity of TAPE-COF.

[0078] 3. Fourier Transform Infrared Spectroscopy (FTIR) Fourier transform infrared (FTIR) spectra of the product and two reactants in Example 1 were obtained using a Thermo IR200 Fourier transform infrared spectrometer via the KBr pellet method, with a wavenumber range of 4000 cm⁻¹. -1 ~400 cm -1 .from Figure 11 The presence of the characteristic peak of C=N in the product, but the absence of the characteristic peaks of NH and C=O, indicates that the reaction proceeded completely.

[0079] 4. Thermogravimetric analysis (TGA) The product of Example 1 and its activated product were subjected to TGA testing using a TA TGA550 instrument. The activation conditions were heating at 100 °C under vacuum for 12 h. The testing conditions were: heating from 25 °C to 800 °C in a N2 atmosphere at a heating rate of 10 °C / min. The results are shown in [Figure number missing]. Figure 12 .like Figure 12 As shown, the product does not exhibit significant weight loss below 450 °C, indicating that the product has excellent thermal stability.

[0080] 5. Acid-base stability 10 mg of the product from Example 1 was added to 10 mL of HCl solutions with pH values ​​of 2, 3, and 5; deionized water with pH value of 7; and NaOH solutions with pH values ​​of 9, 11, and 13, respectively, and soaked for 200 min. The solid was then separated from the solution by vacuum filtration. The solid was then heated under vacuum at 100 °C for 3 h, and PXRD tests were performed (test conditions were the same as in step 1). The results are shown in [Figure 1]. Figure 13 .like Figure 13 As shown, the product of Example 1 can maintain its crystalline state in the pH range of 3 to 12, that is, it can maintain good stability under strong alkaline conditions of pH 12 and also maintain stability under acidic conditions of pH 3.

[0081] Nitrogen adsorption-desorption isotherms and pore size distribution at 6-77 K The 77 K nitrogen adsorption-desorption isotherm of the product of Example 1 was measured using a BSD-PM2 adsorption instrument, as shown below. Figure 14 As shown. Compared with the product of Comparative Example 1, the product of Example 1 has a lower relative pressure ( P / P When the value of 0) is 0.8, the nitrogen adsorption capacity is higher, and the BET specific surface area of ​​the product in Example 1 is calculated to be 1809 m². 2 / g, compared to the product of Comparative Example 1 (specific surface area of ​​1771 m²). 2 (g) has a larger specific surface area, which is more advantageous for applications in adsorption performance.

[0082] 7. Dye adsorption performance As shown in Table 2, the applicant selected six dyes with different sizes and charges, including two anionic dyes: Congo Red and Soap Yellow; two cationic dyes: Brilliant Green and Crystal Violet; and two nonionic dyes: Basic Fuchs Red and Reactive Brilliant Blue.

[0083] Table 2. Reagents used in the dye adsorption performance section (1) Removal rate of a certain concentration of dye over a certain period of time: First, prepare an aqueous solution of dye with a concentration of 16 mg / L. The specific procedure is as follows: accurately weigh 4.0 mg of dye, dissolve it in deionized water in a clean beaker, transfer it to a 250 mL volumetric flask after it is fully dissolved, add deionized water to the mark, shake well, and then transfer it to a brown bottle for later use.

[0084] Add 6.25 mL of a 16 mg / L dye solution and 3.75 mL of deionized water to a 10 mL brown glass bottle to obtain a 10 mg / L dye solution. Measure its absorbance. A 0. Add 15.0 mg of accurately weighed Tape-COF to the dye solution, seal the glass bottle tightly, and sonicate in an ultrasonic cleaner for 5 min. Immediately transfer the solution to a centrifuge tube and centrifuge at 9500 rpm for 5 min to remove a large amount of solid. Take the supernatant and centrifuge at 9500 rpm for 15 min to obtain a solution free of suspended matter. Finally, measure its absorbance. A t , and by 1 C t / C The removal rates of each dye were calculated, and the results are shown in Table 3. C 0、 C t These represent the concentrations of the dye solution before and after adsorption, according to Beer-Lambert's law. A =K bc It can be seen that for the same dye solution C t / C 0= A t / A 0.

[0085] As shown in Table 3, the product of Example 1, after 5 minutes of ultrasonic treatment, achieved an adsorption rate of over 96.5% for all six dyes. This is because the internal surface of the pores of TAPE-COF has both positive and negative charges, providing corresponding adsorption sites for various dyes with different charge distributions. Therefore, it exhibits good adsorption effects on all six dyes. It can be inferred that TAPE-COF likely achieves adsorption of dyes with different charges through electrostatic interactions.

[0086] Table 3. Absorbance and adsorption rate of six dyes at their characteristic wavelengths before and after adsorption. (2) Adsorption isotherm of Congo red Adsorption isotherm experiments were conducted using Congo red (CR) dye. First, a standard curve for CR was plotted: CR solutions with concentrations of 64 mg / L, 48 mg / L, 32 mg / L, 16 mg / L, 8 mg / L, 4 mg / L, and 2 mg / L were prepared, and their absorbance was measured. The absorbance at a wavelength of 496.5 nm was selected to plot the standard curve for CR.

[0087] CR aqueous solutions with concentrations of 1500 mg / L, 900 mg / L, 800 mg / L, 700 mg / L, 600 mg / L, 500 mg / L, 400 mg / L, 300 mg / L, 200 mg / L, and 100 mg / L were prepared. Tape-COF (300 mg / L) prepared in Example 1 was added to each solution, and the solutions were sonicated for 5 min to ensure complete dispersion of the powder. The solutions were then left to stand in the dark for 72 h. After thorough centrifugation, the suspended solid particles were removed, and the absorbance was measured. For solutions with an equilibrium concentration exceeding 128 mg / L after adsorption, dilution was required before absorbance measurement.

[0088] Using the standard concentration formula for CR, the concentrations of each solution after equilibrium are calculated. Q t =( C 0 C e ) V / m COF The adsorption capacity corresponding to each equilibrium concentration was calculated. Among them, C 0 indicates the initial concentration of the dye before adsorption (mg / L). C e express t The remaining concentration of dye at any given time (mg / L). V Indicates the volume (mL) of the dye solution. m COF This indicates the mass (mg) of Tape-COF added. Q t express t The adsorption amount at time t. The adsorption isotherm was fitted using the Langmuir isotherm adsorption model with the concentration at adsorption equilibrium as the x-axis and the adsorption amount as the y-axis. The results are shown in [Figure number missing]. Figure 15 ,from Figure 15 The maximum adsorption amount obtained by fitting Q m =2592.4 mg / g.

[0089] (3) Adsorption cycle experiment of Congo red The following adsorption cycle experiment was conducted using CR dye: a 128 mg / L CR solution was diluted to an 80 mg / L solution for later use, and its absorbance was measured. A0. Accurately pipette 10 mL of 80 mg / L CR solution into a small brown glass bottle, add 15.0 mg of the product from Example 1, seal tightly and sonicate for 5 min. Immediately transfer to a centrifuge tube, centrifuge at 9500 rpm for 5 min to remove a large amount of solid, aspirate the clearer supernatant, and centrifuge again at 9500 rpm for 15 min to obtain a solution free of suspended matter. Finally, measure its absorbance. A 1. Wash the solid powder with anhydrous ethanol until the effluent is colorless, then wash with deionized water, and finally heat under vacuum at 100 °C for 12 h for the next cycle. A n / A 0 represents the removal rate (where...) n =1, 2, 3, 4, 5 (representing the number of cycles), calculate the dye removal rate for each cycle, and obtain the dye removal rate for different number of cycles by plotting the number of cycles on the x-axis and the removal rate on the y-axis. The results are shown in […]. Figure 16 .Depend on Figure 16 It can be seen that the dye removal rate reached over 99% in all 5 cycles. Furthermore, PXRD analysis of the product after 5 cycles demonstrated that the product of Example 1 maintained good crystallinity even after 5 cycles of dye adsorption. Therefore, the product of Example 1 exhibits excellent cyclic adsorption performance, maintaining good crystallinity and high dye adsorption efficiency even after multiple adsorption cycles.

[0090] (4) Adsorption and filtration experiment of Congo red The following dye adsorption and filtration experiment was conducted using CR dye: Prepare an 800 mg / L CR solution for later use. Fill the bottom of a 1 mL syringe with cotton, add 5 mg of accurately weighed adsorbent, compact the solution, and then add 0.8 mL of the 800 mg / L CR solution. Under external pressure, the dye solution will flow out in about 1 minute.

[0091] Please see Figure 17 The adsorbents from left to right are, in order, the product of Example 1, activated carbon, silica gel, type 3A molecular sieve, and COF-300. Figure 17 As shown, the effluent of the CR dye solution with a concentration of 800 mg / L after being adsorbed by the product of Example 1 for about 1 minute was colorless, indicating that the dye was completely adsorbed. However, the effluent after being adsorbed by other adsorbents for about 1 minute was still a darker color, indicating that the dye was not completely removed. This shows that the product of Example 1 has a significantly higher adsorption rate than traditional adsorbents.

[0092] Please see Figure 18From left to right, the images show the CR solution before adsorption, and the CR solutions after adsorption and filtration of the products from Example 1, Example 2, and Comparative Example 1, respectively. Figure 18 As shown, the effluent from the CR dye solutions with a concentration of 800 mg / L after being adsorbed by the products of Examples 1 and 2 for about 1 minute was colorless, indicating that the dye was completely adsorbed. However, the effluent from the product of Comparative Example 1 after being adsorbed for about 1 minute was still a darker color, indicating that the dye was not completely removed. This shows that the products of Examples 1 and 2 have a significantly higher adsorption rate than the products prepared by the solvothermal synthesis method.

[0093] (5) Mixed dye filtration and adsorption experiment Prepare CR, RB19, and BG1 solutions with a concentration of 800 mg / L respectively. Take 1 mL of each of the 800 mg / L CR, RB19, and BG1 solutions and mix them to obtain a mixed dye solution with a concentration of 800 mg / L. Take 0.8 mL of this solution for filtration and adsorption experiments, following the same steps as the adsorption and filtration experiment in step (4). The results are shown in [Figure number missing]. Figure 19 , Figure 19 Figures (a) and (b) show the mixed dye solution before and after filtration and adsorption, respectively. Figure 19 As shown, the effluent after the mixed dye was adsorbed by the product of Example 1 for about 1.5 min was colorless, so the product of Example 1 can also achieve efficient adsorption in the adsorption of mixed dye.

[0094] In summary, this application employs a simple solution stirring method, where the reaction is carried out at 10 ℃ to 120 ℃ for 1 h to 12 h, to obtain TAPE-COF with high crystallinity, high porosity, and high stability. Furthermore, compared to products obtained by traditional solvothermal synthesis methods, the product obtained by the simple solution stirring method has a larger BET specific surface area, thus exhibiting superior adsorption performance, such as higher dye removal rate, faster dye adsorption rate, and higher maximum adsorption capacity.

[0095] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0096] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A method for preparing a covalent organic framework, characterized in that, Includes the following steps: A mixture of tetra-(4-aminophenyl)ethylene, terephthalaldehyde, an acid regulator, and a solvent is obtained. The mixture is subjected to solution stirring reaction and then purified to obtain the covalent organic framework; The temperature of the solution stirring reaction is 10 ℃~120 ℃, and the time is 1 h~12 h; The molar ratio of the tetra-(4-aminophenyl)ethylene to the acid modifier is 1:(60~300).

2. The method for preparing a covalent organic framework as described in claim 1, characterized in that, The molar ratio of tetra-(4-aminophenyl)ethylene to terephthalaldehyde is 1:(1.5~2.5).

3. The method for preparing a covalent organic framework as described in claim 2, characterized in that, The acidity regulator includes one or more of formic acid, acetic acid, propionic acid, butyric acid, and trifluoroacetic acid.

4. The method for preparing a covalent organic framework as described in claim 3, characterized in that, The acid regulator is provided in the form of an acid solution, and the concentration of the acid regulator in the acid solution is 3 mol / L to 15 mol / L.

5. The method for preparing a covalent organic framework as described in claim 1, characterized in that, The solvents include water, tetrahydrofuran, dimethyl sulfoxide, 1,4-dioxane, cyclohexane, and... N , N One or more of dimethylformamide.

6. The method for preparing a covalent organic framework as described in claim 1, characterized in that, The purification process includes one or more of the following: filtration, washing, Soxhlet extraction, and drying.

7. The method for preparing a covalent organic framework according to any one of claims 1 to 6, characterized in that, The yield of the covalent organic framework is 0.07 g to 3.1 g, with a yield of ≥60%.

8. A covalent organic framework, characterized in that, It is prepared by the method described in any one of claims 1 to 7 for the preparation of covalent organic frameworks.

9. The covalent organic framework as described in claim 8, characterized in that, One or more of the following conditions must be met: (1) The BET specific surface area of ​​the covalent organic framework is ≥1800 m². 2 / g; (2) The covalent organic framework has a first pore size and a second pore size, wherein the first pore size is 2.4 nm to 2.5 nm and the second pore size is 0.5 nm to 0.6 nm; (3) The thermal decomposition temperature of the covalent organic framework is ≥400 ℃; (5) The covalent organic framework remains structurally stable in solutions with pH values ​​of 3 to 12; (6) The maximum adsorption capacity of the covalent organic framework for Congo red is ≥2500 mg / g; (7) Using 5 mg of the covalent organic framework described above, an adsorption filtration experiment was conducted on a Congo red solution with a concentration of 800 mg / L. The Congo red removal rate reached over 99% within 1 min.

10. A method for treating wastewater, characterized in that, Includes the following steps: The covalent organic framework as described in claim 8 or 9 is placed in wastewater containing organic dyes for adsorption treatment.

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