Preparation of self-supporting graphene / COFs membrane and application of self-supporting graphene / COFs membrane in environmental water treatment

Abstract

The invention discloses preparation of a self-supporting graphene / COFs membrane and application of the self-supporting graphene / COFs membrane in environmental water treatment. A laser direct writing technology is adopted, a pattern of a spatial net structure is designed, graphene is printed on the two faces of a PI film, and the self-supporting graphene film is obtained. And growing COFs layers on both sides of the graphene film by taking the prepared graphene film as a carrier, TPA and TAPB as monomers, acetic acid as a catalyst and dimethyl sulfoxide as a solvent to obtain the graphene / COFs (G / COFs) composite film. The designed G / COFs composite membrane has a spatial mesoporous structure, and has efficient adsorption performance on organic pollutants and biomacromolecules in environmental water. The preparation method is simple, the preparation speed is high, the self-supporting property is good, the adsorbent can be repeatedly used, and the adsorbent has good adsorption performance. As a novel material, the G / COFs membrane composite material further promotes the development of the fields of filtration separation, conductivity, sensing, storage and the like.

Description

Technical Field

[0001] This invention belongs to the field of environmental water treatment technology, specifically relating to the preparation of a self-supporting graphene COFs membrane and its application in environmental water treatment. Background Technology

[0002] Covalent organic frameworks (COFs) are a class of novel porous crystalline materials with periodic pore structures formed by organic structural units linked by strong covalent bonds. Due to their high specific surface area, designable pore structure, excellent thermal / chemical stability, and abundant functional sites, COFs show broad application prospects in fields such as gas adsorption and separation, catalysis, sensing, energy storage, and drug delivery.

[0003] To translate the superior properties of COFs into practical membrane materials, existing technologies have mainly developed the following three strategies: (1) Co-blending membrane formation method: This method uses pre-synthesized COF powder as a functional filler, disperses it in a polymer solution (such as polyethersulfone, polyimide), and blends it into a membrane through non-solvent phase separation, interfacial polymerization and other techniques. Although this method is simple, the COF filler is prone to agglomeration and uneven distribution in the membrane, resulting in non-selective defects in the membrane structure. At the same time, the interfacial bonding force between the filler and the polymer matrix is ​​weak, and interfacial delamination is prone to occur after long-term use. In addition, the regular pores of COF are easily blocked by polymer, and its theoretical separation performance is difficult to be fully utilized.

[0004] (2) In-situ growth method: This method introduces active sites on the surface of a modified substrate, allowing COF monomers to polymerize and crystallize directly on the substrate, forming a separation layer through continuous growth. The film obtained by this method is continuous and has a strong bond with the substrate, but the process is complex, and the control of substrate pretreatment and reaction conditions (temperature, concentration, time) is extremely demanding, resulting in poor reproducibility. Internal stress is easily generated during the growth process, leading to film cracks, and it is difficult to achieve uniform growth on large-area or complex structure substrates.

[0005] (3) Layer-by-layer stacking method: This method first exfoliates the bulk COF crystals into two-dimensional nanosheets, and then assembles the nanosheets into a film layer by layer through vacuum filtration, spin coating, etc. This method can prepare ultrathin, high-throughput and highly oriented films with excellent performance. However, the large-scale and high-quality preparation of COF nanosheets is still a challenge. The nanosheets are mainly connected by weak van der Waals forces. The interlayer structure is unstable under high pressure or swelling environment, and is prone to recombination or destruction, resulting in a sharp decline in separation performance and insufficient long-term operational stability.

[0006] In summary, existing COFs thin film preparation technologies all have significant shortcomings: blending methods sacrifice performance and stability; in-situ growth methods are limited by process complexity and reproducibility; and layer-by-layer stacking methods face bottlenecks such as difficulty in nanosheet preparation and poor interlayer stability. Therefore, there is an urgent need in this field to develop a novel COFs composite membrane preparation method that is simple to process, has good reproducibility, and can produce membranes with strong interfacial bonding, stable structure, and can fully utilize the intrinsic sieving properties of COFs, in order to promote its large-scale industrial application.

[0007] Graphene is a single-atom-layer two-dimensional spline... 2 Hybrid carbon nanosheets, due to their large specific surface area, high electron mobility, thermal conductivity, biocompatibility, ultra-low density, and mechanical flexibility, exhibit excellent optical, electrical, chemical, and physical properties. Therefore, graphene is considered an ideal fundamental material for constructing high-performance thin films. Currently, there are in-depth studies and applications of efficient graphene preparation methods, such as micromechanical exfoliation (HOPG), chemical vapor deposition (CVD), epitaxial growth, reduction of graphene oxide (GO), and organic synthesis. However, graphene film technology has long been hampered by the situation of "excellent laboratory demonstrations but difficult engineering scale-up," with its complex "preparation-transfer-processing" chain being the fundamental bottleneck restricting its industrialization.

[0008] The emergence of laser-induced graphene technology has provided a revolutionary approach to solving the challenges in its preparation. This technology uses a computer-controlled laser beam (such as a CO2 laser) to directly scan a specific carbon precursor (such as a polyimide film). Under the influence of laser radiation energy, a chemical reduction reaction is initiated, removing substances such as H2O and CO2 present in the olefin oxide, thereby transforming the polymer into porous graphene material in one step and in situ.

[0009] With industrial development and improved living standards, a series of activities inevitably generate a range of pollutants, among which wastewater treatment is a significant problem. Currently, COFs (Chemical Oxide Fibers) materials have attracted widespread attention for pollutant removal and have been successfully applied in water treatment, removing heavy metals and organic pollutants. Heavy metals, such as lead, mercury, chromium, and arsenic, are highly harmful to human health and difficult to decompose; COFs materials can remove them to a certain extent. Organic pollutants include pesticides, biotoxins, endocrine disruptors, recovered chlorinated antibacterial agents, pharmaceutical waste, and various aromatic hydrocarbons; COFs can effectively remove these organic pollutants through filtration. Summary of the Invention

[0010] The purpose of this invention is to provide a method for preparing a self-supporting graphene / COFs (G / COFs) membrane and its application in environmental water treatment.

[0011] This invention utilizes CAD design to create graphene patterns and employs laser direct-writing graphene technology to prepare graphene membranes. Using 1,3,5-tris(4-aminophenyl)benzene (TAPB) and terephthalaldehyde (TPA) as monomers, a self-supporting graphene membrane as a carrier, acetic acid as a catalyst, and dimethyl sulfoxide (DMSO) as a solvent, a layer of COFs material is grown on both the upper and lower surfaces of graphene (G). The prepared G / COFs material is then eluted and dried to obtain the G / COFs composite membrane. The G / COFs composite membrane exhibits excellent adsorption performance, is reusable, and saves production costs, thus addressing the economic benefits of reducing the industrial application of COFs in water treatment. This further advances the development of water treatment membranes that are simple to prepare, fast to produce, reusable, and structurally stable.

[0012] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a self-supporting graphene COFs film includes the following steps: 1) CAD drawing software was used to design the filter membrane pattern, and a laser direct writing instrument was used to print the graphene membrane on the polyimide (PI) membrane; 2) Using 1,3,5-tris(4-aminophenyl)benzene (TAPB) and terephthalaldehyde (TPA) as reactants, a self-supporting graphene film as a carrier, acetic acid as a catalyst, and dimethyl sulfoxide (DMSO) as a solvent, a COFs material is grown on the surface of graphene (G). The prepared G / COFs material is washed and dried to obtain the G / COFs composite film.

[0013] The graphene film designed and printed in step 1) above has the following dimensions: a circle with a radius of 7.0 mm is filled with regular hexagons with a line width of 0.14 mm and a radius of 0.5 mm.

[0014] The conditions for the laser direct writing instrument in step 1) above are: wavelength 450 nm, output power 5.5 W, laser relative intensity set to 60~90%, engraving relative depth 37~43%, double-sided laser direct writing is performed on the same position of the PI film to ensure that the regular hexagons on both sides are connected and densely interlaced, so as to make a self-supporting and filterable graphene film. The thickness of the PI film is greater than the laser printing depth and less than twice the laser printing depth.

[0015] Preferably, the laser printing conditions in step 1) above are: the laser is a laser direct writer, wavelength 450 nm, output power 5.5 W, laser relative intensity 90%, and engraving relative depth 41%.

[0016] In step 2) above, weigh 0.0265 g TAPB and 0.0150 g TPA (n(TAPB):n(TPA) = 2:3) into a 250 mL beaker, add 25 mL of dimethyl sulfoxide, and mix well to obtain a mixed solution. Place the self-supporting graphene membrane prepared in step 1) into the mixed solution, and seal the beaker tightly with a sealing membrane. Gently shake the beaker on a shaker for 30–70 min while slowly adding 1 mL of acetic acid dropwise (5–20 min). Remove the membrane and wash it 3–4 times with dimethyl sulfoxide and methanol, respectively. Dry the washed membrane at 35 °C.

[0017] Preferably, the conditions for preparing the G / COFs membrane in step 2) above are: slight oscillation on the oscillator for 50 min, and slow addition of 1 mL of acetic acid for 10 min.

[0018] An application of self-supporting G / COFs membranes in environmental water treatment includes the following steps: 1) Set up a membrane filtration device and place 1 to 5 layers of G / COFs membranes for filtration.

[0019] 2) Add the test solution to the membrane filtration device at a flow rate of 0.5~10 mL / min for filtration. Use an ELISA reader to detect the absorbance of the test solution before and after filtration, and calculate the adsorption amount and removal rate.

[0020] 3) Use eluent (methanol, sodium dodecyl sulfate) to elute the adsorbed self-supported G / COFs membrane, rinse with water after elution and dry for storage.

[0021] The membrane filtration device used in step 1) above consists of a self-supporting G / COFs membrane placed on a sand filter head, which is then fixed between the filter cup and the conical collection bottle using clamps. Membranes can be stacked in 1-5 layers for better removal efficiency.

[0022] The microplate reader used in step 2) above is a TECAN SPARK, and the adsorption capacity is calculated using: Q=

[0023] η =

[0024] Where Q is the adsorption capacity of organic pollutants and biomolecules per unit volume, and η is the removal rate of organic pollutants and biomolecules by the G / COFs membrane; C i and C f The concentrations of the original solution and the filtered solution are respectively; V is the volume of adsorbed organic pollutants and biomolecules; m is the mass of the G / COFs membrane used.

[0025] Step 3) above: Add the eluent dropwise to the membrane filtration device, use an enzyme-linked immunosorbent assay (ELISA) reader to detect the absorbance of the filtrate before and after elution, until complete elution, then wash with water and dry at 35°C for storage.

[0026] Organic pollutants in ambient water include triclosan and triclocarban. The detection wavelength is 280 nm, and the pollutant concentration is 10~50 mg / L. The removal rate can reach over 90%. A 10 mg / L NaOH solution is used to adjust the solution environment and promote the dissolution of pollutants. Elution is performed using 1~5 mL of methanol, and the solution can be reused 3~10 times.

[0027] The biomacromolecules in environmental water are heme-containing prosthetic proteins, including hemoglobin, cytochrome C, myoglobin, peroxidase, and other large molecular proteins. The detection wavelength is about 405 nm, the pollutant concentration is 0.5~2 mg / mL, and the removal rate can reach more than 95%. Elution is performed using 10~50 mL of 10% sodium dodecyl sulfate (SDS) at a temperature of 30~50℃. The SDS solution can be reused 3~10 times.

[0028] The significant advantages of this invention are: 1) Graphene and COFs work together to achieve super strong adsorption performance: The high specific surface area of ​​graphene provides a large number of adsorption sites for organic pollutants and biomacromolecules, while the precise pore structure and specific adsorption properties of the COFs layer enable selective adsorption of target substances. The two work together to greatly improve the adsorption efficiency and adsorption capacity of the composite membrane for target pollutants in environmental water, and have both broad-spectrum adsorption and selective targeting.

[0029] 2) Two-component synergistic enhancement of membrane structure stability and self-support: The graphene membrane itself has excellent self-supporting properties, providing a solid structural framework for the composite membrane. The COFs layer grown in situ on both sides forms a protective coating structure, effectively preventing the graphene layer from falling off or pulverizing in water treatment applications. At the same time, it further enhances the overall mechanical properties of the composite membrane. Its self-support and structural stability are significantly better than those of a single graphene membrane or COFs membrane.

[0030] 3) The preparation process is efficient and simple, and suitable for large-scale applications: The laser direct writing technology is used to form a self-supporting graphene film with a spatial network structure in one step. Combined with the in-situ growth method, COFs layers are constructed on both sides. The entire preparation process has few steps and is fast. It does not require complex substrate support and subsequent separation processes. Moreover, the raw materials are readily available and the reaction conditions are mild, which greatly reduces the preparation cost and has good potential for industrial scale-up.

[0031] 4) High reusability and promising multi-functional applications: Due to its excellent structural stability, the composite membrane can be recycled multiple times after adsorption saturation through simple desorption treatment, effectively improving the utilization efficiency of the material and reducing the application cost. At the same time, relying on the conductivity of graphene and the structural tunability of COFs, this composite membrane can not only be efficiently applied to the separation and adsorption field of environmental water treatment, but also extended to multiple fields such as conductivity, sensing, and material storage, realizing multiple uses of one material and a wide range of application scenarios. Attached Figure Description

[0032] Figure 1 Schematic diagram of a self-supporting G / COFs membrane and its separation and analysis of biomacromolecules in aqueous solution; Figure 2 Schematic diagram of G / COFs membrane filtration device; Figure 3 CAD design drawings for G / COFs membranes; Figure 4 Physical image of a laser-written graphene film; Figure 5 Photo of G / COFs composite membrane; Figure 6 Scanning electron microscope (SEM) image of graphene film; Figure 7 Scanning electron microscope (SEM) image of G / COFs membrane; Figure 8 Adsorption curves of G / COFs composite membrane, G, and Blank for TCS; Figure 9 Adsorption curves of G / COFs composite membrane, G, and Blank for hemoglobin; Figure 10 The elution effect of G / COFs composite membrane on TCS at different flow rates; Figure 11 Removal rate of TCS by G / COFs composite membrane at different flow rates; Figure 12 Removal rates of TCS for different volumes by G / COFs, G, and Blank; Figure 13 Elution curves of methanol for different concentrations of TCS; Figure 14 Adsorption curve of G / COFs composite membrane for TCS three-stage filtration; Figure 15 Removal rates of TCS by multilayer G / COFs membranes and G membranes. Detailed Implementation

[0033] To better understand the present invention, it will be further described below with reference to the accompanying drawings and embodiments, but this is not intended to limit the invention. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods.

[0034] Instrument: Nano Pro-Ⅲ laser printer (Tianjin Jiayin Nanotechnology Co., Ltd.); HY-4 Speed-Adjustable Multi-Purpose Oscillator (Jintan Yichen Instrument Manufacturing Co., Ltd.)

[0035] SPARK ELISA reader (TECAN) Self-supported graphene / COFs membranes and their separation and analysis of contaminants in aqueous solutions, such as... Figure 1 As shown: The specific process includes a) laser-written graphene film; b) preparation of G / COFs membrane; c) separation and analysis of pollutants in aqueous solution. The filtration device is as follows... Figure 2 As shown. Example 1

[0036] Using CAD drafting software, a hexagonal close-lay pattern with a line width of 0.14 mm and a radius of 0.5 mm was designed within a circle with a radius of 7.0 mm. Figure 3 Using a 450 nm laser direct writing instrument with an output power of 5.5 W, a printing laser relative intensity of 90%, and an engraving relative depth of 41%, a self-supporting graphene film was printed on both sides of a PI film (thickness 0.06 μm) at the same location. Figure 4 ). Example 2

[0037] Weigh 0.0265 g TAPB and 0.0150 g TPA (n(TAPB):n(TPA) = 2:3) into a 250 mL beaker, add 25 mL of dimethyl sulfoxide solvent, dissolve and mix well. Place the self-supporting graphene membrane prepared in Example 1 into the beaker, seal the mouth of the beaker with a sealing film, leaving a small hole. Place the beaker on a variable speed multi-purpose shaker and shake, while using a 100 µL pipette, slowly add 1 mL of acetic acid (approximately 10 min) into the beaker. Shake the reaction vigorously for 50 min, during which time photographs are taken to observe the growth of COFs. After 50 min, remove the graphene membrane after the reaction, wash it three times with dimethyl sulfoxide and methanol respectively, and then dry it in a 35 °C oven to obtain the G / COFs composite membrane. Figure 5 ). Example 3

[0038] The surface morphology of the graphene film prepared in Example 1 was characterized using scanning electron microscopy (SEM). Figure 6The figure shows the spatial network structure of graphene, indicating that the PI film was successfully induced into graphene material through laser direct writing technology. The macroporous / mesoporous structure of graphene endows the graphene material with an ultra-high specific surface area and excellent electron transfer rate, providing favorable conditions for the separation and analysis of biomacromolecules using graphene membranes in water treatment.

[0039] The surface morphology of the G / COFs prepared in Example 2 was characterized using scanning electron microscopy (SEM). Figure 7 The figure shows that the surface of G / COFs has a dense mesoporous structure with a diameter of approximately 2-5 µm. A relatively dense mesoporous structure is also observed inside the cross-section of the G / COF membrane. COFs coated on graphene provide a high specific surface area and tunable pore size, enabling the selective separation and analysis of biomolecules. Example 4

[0040] Accurately weigh 25 mg of triclosan into a 1000 mL volumetric flask. Dissolve 10 mg of NaOH granules in a small amount of deionized water in a 50 mL beaker, then use a glass rod to transfer the solution into the 1000 mL volumetric flask. Shake the solution thoroughly for a period of time (the NaOH should be washed three times with deionized water and transferred into the volumetric flask). Make up to volume with deionized water. Sonicate the solution for 30 minutes until the triclosan (TCS) solid powder is completely dissolved. Accurately weigh 10 mg of NaOH, dissolve it in a 50 mL beaker, and transfer the NaOH solution into a 1000 mL volumetric flask using a glass rod. Shake thoroughly and mix well; then make up to volume with deionized water.

[0041] 100µL of triclosan stock solution was pipetted into a UV-Vis microplate and its absorbance was measured. The absorbance (A) of the highest peak was recorded. (The stock solution was sonicated for about 3 minutes before each measurement.) 100µL of NaOH stock solution was pipetted into a UV-Vis microplate and its absorbance at 290nm was measured and recorded. The aqueous filter membrane was placed flat on the prepared vacuum filtration flask, and the G / COFs composite membrane prepared in Example 2 was weighed and placed on it, and clamped. (The G / COFs need to be dried in a drying oven (37℃) for a period of time before each measurement.) 1mL of triclosan stock solution was pipetted into a 1000µL pipette and vacuum filtered. The flow rate was set to 1mL / min. After the solution was dried, it was poured into a 4mL vial. Use a 100µL pipette to draw 100µL of liquid from the vial and place it in a UV microplate to measure its absorbance. Record the absorbance (A) value of the highest peak for each measurement. Before the next measurement, the liquid in the filtration flask should be shaken dry. Repeat this operation 2-3 times to complete the adsorption determination of triclosan on the G / COFs composite membrane, and calculate the adsorption amount and removal rate of TCS. Example 5

[0042] Following the operating conditions of Example 4, without changing the amount of NaOH, 10 mg / L, 25 mg / L, and 50 mg / L TCS solutions were prepared respectively. Under three different conditions—blank membrane, graphene membrane, and G / COFs membrane—1 mL of TCS solution was added dropwise each time, and the amount of TCS adsorbed after each addition was recorded. The results are as follows: Figure 8 As shown, at different concentrations, the adsorption effect of the G / COFs composite membrane on TCS is consistently superior to that of G and Blank. This is because G / COFs possess a unique, dense mesoporous structure, allowing for the sufficient adsorption of TCS biomolecules. In the future, it will play a crucial role in the treatment of organic pollution in aquatic environments. Example 6

[0043] Prepare a 0.1 mg / mL hemoglobin aqueous solution. Use a 100 µL pipette to draw 100 µL of the hemoglobin aqueous solution and place it in a UV-Vis microplate to measure its absorbance. Record the absorbance (A) value of the highest peak for each measurement. Place the aqueous filter membrane flat on the prepared vacuum filtration flask, weigh the G / COFs composite membrane prepared in Example 2, place it on top, and clamp it securely. (The G / COFs need to be dried in a drying oven (37°C) for a period of time before each measurement). Use a pipette to draw 2 mL of the hemoglobin aqueous solution and perform vacuum filtration. Set the flow rate to 1 mL / min, and after the solution is dried, pour it into a 4 mL vial. Use a 100 µL pipette to draw 100 µL of the liquid from the vial and place it in a UV-Vis microplate to measure its absorbance. Record the absorbance (A) value of the highest peak for each measurement to complete the adsorption determination of hemoglobin by the G / COFs composite membrane. Example 7

[0044] Under the experimental conditions of Example 6, 0.05 mg / mL, 0.1 mg / mL, and 0.5 mg / mL hemoglobin aqueous solutions were prepared respectively. Under three different operating conditions—blank membrane, graphene membrane, and G / COFs membrane—1 mL of hemoglobin aqueous solution was added dropwise each time, and the amount of hemoglobin adsorbed after each addition was recorded. The results are as follows: Figure 9 As shown, at different concentrations, the adsorption effect of the G / COFs composite membrane on hemoglobin is always better than that of G and Blank. This indicates that G / COFs can efficiently adsorb biomacromolecules in aqueous solution. Example 8

[0045] To investigate the effect of flow rate on the adsorption performance of the membrane material prepared in Example 2 and to determine the optimal operating flow rate, adsorption experiments were conducted under the same experimental conditions as in Example 4, with only the feed flow rate adjusted. Absorbance measurements revealed differences in the full wavelength scan (200-700 nm) at three flow rates: low (0.625 mL / min), medium (1 mL / min), and high (10 mL / min). The results are as follows: Figure 10 As shown, the peak height of the TCS stock solution and the peak height of the eluted TCS solution were largest under low-speed elution, indicating that the elution effect was best under low-speed elution. Under medium-speed elution, the peak heights of the TCS stock solution and the eluent remained significantly separated, maintaining good elution performance. However, the elution effect was poor during high-speed elution. This is because the increased flow rate of the fluid (TCS solution) meant that some TCS stock solution was not fully adsorbed and eluted by the G / COFs composite membrane, resulting in a small amount of unadsorbed TCS stock solution flowing into the filter cup, affecting the elution and removal efficiency. The TCS removal rate of the G / COFs composite membrane at different flow rates was calculated, and the results are shown below. Figure 11 As shown, the removal rate and elution effect of the G / COFs composite membrane are closely related to the flow rate, with the elution effect and removal rate being optimal at lower flow rates; and the relationship between their removal rates at different flow rates resembles a step shape. Example 9

[0046] To investigate the relationship between the removal capacity of G / COFs membranes for biomacromolecules under different concentrations and volumes of filtered liquid, the adsorption capacity was measured under the operating conditions of Example 4. This was done by adding (1, 5, 10 mL) 10 mg / L TCS solution, (1, 5, 10 mL) 25 mg / L TCS solution, and (50 mg / L TCS solution) (1, 5, 10 mL). The removal rate was characterized by the adsorption capacity under these three conditions. Furthermore, by investigating the TCS removal rates of the G / COFs composite membrane, G, and Blank at different concentrations within the same volume, the intrinsic relationship between them was revealed. Figure 12As shown, at the same concentration, the G / COFs composite membrane exhibited the highest removal rate after adding 1 mL of TCS solution. After methanol elution, washing, and drying for reuse, the adsorption rate of the G / COFs composite membrane decreased for high-concentration TCS solutions when 5-10 mL of TCS solution was added. The adsorption rate for intermediate-concentration (25 mg / L) TCS solutions remained essentially unchanged, while the adsorption rate for low-concentration TCS solutions showed an increasing trend. This is because at high concentrations, the G / COFs composite membrane gradually becomes saturated, making it difficult to adsorb more TCS. However, under medium and low concentration conditions, the G / COFs composite membrane has not reached adsorption saturation, and TCS can still be adsorbed, thus its adsorption rate remains unchanged or increases. Furthermore, the experiment also demonstrated that at any concentration, the removal rate of the G / COFs composite membrane is higher than that of G and Blank, especially at high concentrations. Example 10

[0047] To investigate the recycling of the membrane material prepared in Example 2, after performing TCS adsorption processes at different concentrations in Example 4, 1 mL of methanol was sequentially added to the G / COFs composite membranes with different TCS adsorption concentrations for elution, and the change in TCS adsorption amount as a function of the added methanol volume was analyzed. Figure 13 As shown, the elution effect of TCS was very significant after adding 1-2 mL of methanol. The elution gradually leveled off within the next 3-5 mL, and the elution rate reached over 90% for all three TCS concentrations after the final addition of 5 mL of methanol. Furthermore, it was demonstrated that the higher the TCS concentration within the methanol volume range of 1-4 mL, the more pronounced the elution effect. After being eluted with methanol, the G / COFs composite membrane can be recycled and still maintain good adsorption performance, significantly reducing time and material costs. This demonstrates unparalleled advantages and benefits compared to other similar materials capable of separating organic pollutants in aquatic environments. Example 11

[0048] To investigate the reusability of the membrane material prepared in Example 2, the G / COFs membrane was subjected to repeated filtration operations at a TCS concentration of 50 mg / mL, following the procedure described in Example 4. The results are as follows... Figure 14 As shown, the G / COFs composite membrane maintained good adsorption performance (adsorption capacity of 470-648 μg) even after three repeated experiments, demonstrating good reproducibility. Furthermore, it maintained good adsorption performance even after multiple reuses, exhibiting excellent reliability. Example 12

[0049] To investigate the optimization of the filtration effect of the membrane material prepared in Example 2, multilayer G / COFs membrane overlap filtration was performed at a TCS concentration of 25 mg / mL, following the procedure in Example 4. The results are as follows... Figure 15As shown, the removal rate increases significantly with the increase in the number of layers, and the removal effect of the G / COFs composite membrane is about 40% higher than that of the graphene membrane. In the three-layer G / COFs composite membrane, the removal rate can also reach a high value of nearly 75%, which indicates its great development potential and will play a significant role in the field of separation.

[0050] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a self-supporting graphene / COFs film, characterized in that: Includes the following steps: 1) A graphene film was printed on a PI film using a laser direct writing instrument; 2) Using 1,3,5-tris(4-aminophenyl)benzene (TAPB) and terephthalaldehyde (TPA) as reaction monomers, the self-supporting graphene film prepared in step 1) is used as a carrier, acetic acid is used as a catalyst, and dimethyl sulfoxide (DMSO) is used as a solvent to grow a layer of COFs material on the graphene surface. After elution and drying, the self-supporting graphene / COFs film is obtained.

2. The preparation method according to claim 1, characterized in that: Step 1) The morphology and size of the printed graphene film are designed as follows: a circle with a radius of 7.0 mm is filled with regular hexagons with a line width of 0.14 mm and a radius of 0.5 mm.

3. The preparation method according to claim 1, characterized in that: The conditions for the laser direct writing instrument in step 1) are: wavelength 450 nm, output power 5.5 W, laser relative intensity set to 60~90%, engraving relative depth 37~43%, double-sided laser direct writing is performed on the same position of the PI film to ensure that the regular hexagons on both sides are connected and densely interlaced, thus producing a self-supporting and filterable graphene film.

4. The preparation method according to claim 1, characterized in that: In step 2), TAPB and TPA are added to dimethyl sulfoxide in a molar ratio of 2:3 and mixed to obtain a mixed solution. The self-supporting graphene film is placed in the mixed solution, and acetic acid is slowly added dropwise under shaking conditions. After the reaction is completed, the film is taken out, washed with dimethyl sulfoxide and methanol, and dried at 35 °C to obtain the final product.

5. The preparation method according to claim 4, characterized in that: The acetic acid was added slowly over a period of 5 to 20 minutes, and the reaction time was 30 to 70 minutes.

6. A self-supporting graphene / COFs membrane prepared by the preparation method according to any one of claims 1-5.

7. The application of the self-supporting graphene / COFs membrane according to claim 6 in the separation and adsorption of organic pollutants and biomacromolecules in environmental water.

8. The application according to claim 7, characterized in that, The filtration process involves stacking 1 to 5 layers of graphene / COFs membranes.

9. The application according to claim 7, characterized in that, Organic pollutants in ambient water include triclosan and triclocarban.

10. The application according to claim 7, characterized in that, Biomacromolecules in environmental water are heme-containing prosthetic proteins, including hemoglobin, cytochrome C, myoglobin, and peroxidase.

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