Anionic porous organic material and application thereof in dye removal

Abstract

The invention discloses an anionic porous organic material and application thereof in dye removal, and belongs to the technical field of dye adsorption materials and membrane separation. The COFs-derived porous crystalline material disclosed by the invention shows remarkable advantages in the field of adsorption by virtue of an ultra-large specific surface area, excellent stability and an adjustable pore structure. Due to the characteristic of easy functionalization, the adsorption selectivity and capacity can be improved by modifying functional groups; the method is simple and ingenious in synthesis process, has huge potential in expanded production, and is considerable in adsorption capacity.

Description

Technical Field

[0001] This invention relates to an anionic porous organic material and its application in dye removal, belonging to the fields of dye adsorption materials and membrane separation technology. Background Technology

[0002] Organic dyes are structurally stable and difficult to degrade, which not only damages ecosystems but also poses a threat to human health.

[0003] Covalent organic frameworks (COFs) are a class of porous crystalline materials composed of organic units linked by strong covalent bonds, and have attracted widespread attention in the field of adsorption in recent years. Compared with traditional adsorbent materials, COFs exhibit significant advantages, including a large specific surface area, providing abundant adsorption sites, and excellent thermal and chemical stability. Furthermore, COFs possess tunable porosity and easily functionalized structures, allowing for the introduction of specific functional groups through modification, thereby improving adsorption selectivity and capacity, and demonstrating great application potential in adsorption separation. However, organic porous material powders suffer from drawbacks such as easy agglomeration and difficulty in recycling in practical applications, severely restricting their engineering applications.

[0004] The literature "Thiourea-Isocyanate-Based Covalent Organic Frameworks with Tunable Surface Charge and Surface Area for Methylene Blue and Methyl Orange Removal from Aqueous Media; doi.10.3390 / mi13060938" discloses a method of using alkali treatment to enhance the negative charge on the surface of thiourea-coated organic frameworks (TH COFs), directly improving the adsorption of molecular black (MB) dyes, achieving an MB adsorption capacity of 5.5 mg / g. While the TH COFs prepared by this method possess MB adsorption capacity, the adsorption amount is relatively poor.

[0005] The literature "Two-dimensional imide-based covalent organic frameworks for cationic dye adsorption: Synthesis, characterization, isotherm, kinetics, and thermodynamic analysis; doi.org / 10.1016 / j.hazadv.2025.100680" discloses the adsorption of rhodamine B using imide-linked COFs. However, these COFs have low specific surface area and crystallinity, poor cycling ability, and limited practical value. Furthermore, their adsorption capacity and adsorption equilibrium rate for dyes are slow, with an adsorption capacity of 192.54 mg·g⁻¹ for rhodamine B. -1 .

[0006] Therefore, it is of great importance to develop a highly efficient and environmentally friendly organic dye adsorption and separation material, which has extremely high practical and economic value. Summary of the Invention

[0007] To address the aforementioned issues, this invention provides a porous crystalline material derived from COFs, exhibiting significant advantages in adsorption due to its ultra-large specific surface area, excellent stability, and tunable pore structure. Its ease of functionalization allows for enhancement of adsorption selectivity and capacity through modification of functional groups. The synthesis process is simple and ingenious, with great potential for large-scale production and considerable adsorption capacity.

[0008] The first objective of this invention is to provide a method for preparing anionic porous polymer materials, comprising the steps of: (1) Mix 1,2,4,5-benzenetetracarboxylic acid, 1,3,5-tris(4-aminophenyl)benzene and benzoic acid, heat and react under vacuum, cool, grind, wash and dry to obtain PM-COF; (2) PM-COF and KOH solution were mixed, stirred, centrifuged, washed and dried at a ratio of 20~60 mg: 40~50 mL to obtain anionic porous polymer material; The concentration of the KOH solution is 0.2~1 M.

[0009] In one embodiment, PM-COF and KOH solution are used in a ratio of 20-30 mg: 40-50 mL.

[0010] In one embodiment, in step (1), the molar ratio of 1,2,4,5-benzenetetracarboxylic acid, 1,3,5-tris(4-aminophenyl)benzene and benzoic acid is 0.8~1.5:0.8~1.5:4~6; Optionally, the molar ratio of 1,2,4,5-benzenetetracarboxylic acid, 1,3,5-tris(4-aminophenyl)benzene and benzoic acid is 1~1.2:1~1.5:4~6.

[0011] In one embodiment, in step (1), the heating reaction is carried out at 180~200°C for 4~6 days; Optionally, the reaction is carried out at 200°C for 120 h.

[0012] In one embodiment, in step (1), the drying is vacuum drying at a temperature of 50~60 °C.

[0013] In one embodiment, in step (2), the drying is vacuum drying at a temperature of 70~80 °C.

[0014] A second objective of this invention is to provide anionic porous polymer materials prepared by any of the methods described above.

[0015] A third objective of this invention is to provide a cationic dye removal product containing the aforementioned anionic porous polymer material.

[0016] Optionally, the cationic dyes include, but are not limited to, methylene blue, crystal violet, safranin O, and malachite green. The fourth objective of this invention is to provide a method for preparing nanocomposite films, which are prepared by electrospinning using the above-mentioned anionic porous polymer material.

[0017] In one embodiment, the electrospinning parameters are a spinning fineness of 200~600 nm and a feed rate of 1.2~2.0 mL h. -1 The receiving distance is 12~18 cm, and the voltage is 15~20V. Optionally, the electrospinning parameters are: a spinning fineness of 300–400 nm and a feed rate of 1.5–1.8 mL / h. -1 The receiving distance is 14~16 cm, and the voltage is 16~18 kV.

[0018] In one embodiment, the method for preparing the nanocomposite thin film is as follows: 0.8–1.2 mg of polyacrylonitrile (PAN) was uniformly dispersed in 8–12 mL of dimethylformamide (DMF). After forming a homogeneous and transparent solution by magnetic stirring at room temperature for 4–8 h, AM-POP material was quantitatively added and stirred continuously until completely dispersed to obtain AM-POP@PAN spinning solution. The spinning solution was loaded into a 10 mL syringe, and the feed rate was set to 1.5–1.8 mL / h. -1The receiving distance is 14~16 cm, and spinning is carried out under the conditions of 16~18 kV voltage, 30% humidity and room temperature. After electrospinning, the resulting film is dried in an oven at 50-60°C for 12-14 hours to remove residual solvent, and finally a nanocomposite film is obtained.

[0019] The fifth objective of this invention is to provide a nanocomposite thin film prepared by the above-described method.

[0020] The sixth object of the present invention is to provide the application of the above-mentioned anionic porous polymer material or the above-mentioned nanocomposite film in dye adsorption.

[0021] In one embodiment, the dye is a cationic dye; Optionally, the cationic dyes include, but are not limited to, methylene blue, crystal violet, safranin O, and malachite green.

[0022] The seventh objective of this invention is to provide a method for simultaneously improving the dye adsorption performance, pH tolerance, and salt ion tolerance of porous polymer materials, comprising the following steps: (1) Mix 1,2,4,5-benzenetetracarboxylic acid, 1,3,5-tris(4-aminophenyl)benzene and benzoic acid, heat and react under vacuum, cool, grind, wash and dry to obtain PM-COF; (2) PM-COF and KOH solution were mixed, stirred, centrifuged, washed and dried at a ratio of 20~60 mg: 40~50 mL to obtain anionic porous polymer material; The concentration of the KOH solution is 0.2~1 M.

[0023] In one embodiment, PM-COF and KOH solution are used in a ratio of 20-30 mg: 40-50 mL.

[0024] In one embodiment, in step (1), the molar ratio of 1,2,4,5-benzenetetracarboxylic acid, 1,3,5-tris(4-aminophenyl)benzene and benzoic acid is 0.8~1.5:0.8~1.5:4~6; Optionally, the molar ratio of 1,2,4,5-benzenetetracarboxylic acid, 1,3,5-tris(4-aminophenyl)benzene and benzoic acid is 1~1.2:1~1.5:4~6.

[0025] In one embodiment, in step (1), the heating reaction is carried out at 180~200°C for 4~6 days; Optionally, the reaction is carried out at 200°C for 120 h.

[0026] In one embodiment, in step (1), the drying is vacuum drying at a temperature of 50~60 °C.

[0027] In one embodiment, in step (2), the drying is vacuum drying at a temperature of 70~80 °C.

[0028] Beneficial effects of the present invention (1) The COFs-derived AM-POP anionic porous organic polymer prepared in this invention has a large surface area and abundant pore structure, and has anionic active sites, which have excellent adsorption effect on cationic dyes.

[0029] (2) The porous anionic organic polymer material AM-POP provided by this invention can process up to 1061.7 mg g of the cationic dye methylene blue. -1 The treatment yield of the cationic dye crystal violet can reach 1142.3 mg g. -1 The treatment capacity for safranin O and malachite green can reach 980.4 mg g. -1 1047.5 mg g -1 .

[0030] (3) The anionic porous polymer AM-POP provided by the present invention still maintains excellent separation and regeneration application capabilities after multiple cycles of recycling.

[0031] (4) This invention constructs a functionalized electrospun composite membrane system based on porous polymers. Addressing the engineering bottleneck of powder materials' tendency to agglomerate and difficulty in recycling, anionic AM-POP is dispersed in a polyacrylonitrile spinning matrix. By combining this with electrospinning technology, a PAN-AM-X composite membrane with a three-dimensional network topology is prepared. The composite membrane achieves highly efficient selective retention of cationic dyes while maintaining excellent water flux characteristics. Furthermore, the mechanical strength and chemical stability of the flexible membrane material effectively prevent the loss of powder materials. It can be regenerated through an immersion washing process, significantly reducing operating costs and providing a new approach for the engineering application of porous materials. Attached Figure Description

[0032] Figure 1 This is a SEM image of the highly efficient adsorbent for removing cationic dyes prepared in Example 1.

[0033] Figure 2 This is a SEM image of the anionic porous organic polymer composite membrane for separating cationic dyes prepared in Example 3.

[0034] Figure 3 This is the isothermal adsorption curve of the adsorption amount of the highly efficient adsorbent for removing cationic dyes prepared in Example 1.

[0035] Figure 4This is a diagram showing the selective adsorption results of different dyes by the adsorbent prepared in Example 1.

[0036] Figure 5 This is a graph showing the dye removal rate of the cationic dye adsorbent prepared in Example 1 under different pH and ionic strength conditions.

[0037] Figure 6 This is a graph showing the change in dye separation capability of the AM-POP-X composite nanofiber membrane prepared in Example 4 with the amount of POP added.

[0038] Figure 7 This is a comparison of the removal rates of different organic dye aqueous solutions when the AM-POP-X composite nanofiber membrane prepared in Example 4 is filtered. Detailed Implementation

[0039] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0040] The anionic porous organic polymer material prepared by the preparation method of this invention is also within the scope of protection of this invention.

[0041] Furthermore, the present invention discloses a dye adsorbent comprising the above-mentioned AM-POP porous polymer material.

[0042] The aforementioned dye adsorbents are also within the scope of protection of this invention.

[0043] The application of the aforementioned multifunctional AM-POP material or the aforementioned dye adsorbent in the adsorption of dyes is also within the scope of protection of this invention.

[0044] Specifically, the application of the aforementioned anionic porous organic materials or dye adsorbents in the adsorption of cationic dyes is also within the scope of protection of this invention.

[0045] Specifically, the application of anionic porous organic materials or the aforementioned dye adsorbents in the adsorption of cationic dyes involves adjusting the dye concentration gradient in dye-containing water bodies and using sodium chloride to adjust the ionic strength of the dye-containing water. Adsorption experiments were conducted at 20℃~45℃ by adding the aforementioned porous anionic polymer AM-POP material to the dye-containing water under different experimental conditions.

[0046] Specifically, the dyes mentioned are cationic dyes, including two common cationic dyes: methylene blue and crystal violet.

[0047] Furthermore, specifically, the application of the aforementioned anionic porous organic matter or dye adsorbent in the adsorption of cationic dyes is carried out according to the following steps: Based on the experimental objective, the dye concentration, ionic strength, and pH of the water body are adjusted. Then, the aforementioned anionic porous organic matter or dye adsorbent is added, and adsorption is performed for 30 minutes to 72 hours on a magnetic stirrer at a speed of 500-800 rpm. After adsorption, the water body is filtered through a syringe filter equipped with a 0.45 μm microporous MCE membrane to remove the adsorbent, thereby completing the dye removal process from the water body. The treated water body is obtained, wherein the pH adjustment is performed using a hydrochloric acid aqueous solution or a potassium hydroxide aqueous solution. More preferably, a 1M concentration hydrochloric acid aqueous solution or a 1M concentration potassium hydroxide solution is used for adjustment.

[0048] Raw materials used in the examples: 1,2,4,5-Benzenetetracarboxylic acid was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. 1,3,5-Tris(4-aminophenyl)benzene was purchased from: Shanghai Maclean Biochemical Technology Co., Ltd. Benzoic acid was purchased from: Shanghai Aladdin Biochemical Technology Co., Ltd. The dp-TH COF was prepared according to the reference "Thiourea-Isocyanate-Based Covalent Organic Frameworks with Tunable Surface Charge and Surface Area for Methylene Blue and Methyl Orange Removal from Aqueous Media; doi.org / 10.3390 / mi13060938"; Imide-based COF reference "Two-dimensional imide-based covalent organic frameworks for cationic dye adsorption: Synthesis, characterization, isotherm, kinetics, and thermodynamic analysis; doi.org / 10.1016 / j.hazadv.2025.100680".

[0049] Example 1: Preparation of anionic porous polymer materials 1. Preparation of anionic porous polymer materials, the steps are as follows: (1) Add 1,2,4,5-benzenetetracarboxylic acid (38.1 mg, 0.15 mmol), 1,3,5-tris(4-aminophenyl)benzene (35.4 mg, 0.1 mmol) and benzoic acid (73.3 mg, 0.6 mmol) to the reaction tube. (2) After the reaction tube is evacuated and sealed, it is reacted at 200°C for 5 days. After cooling to room temperature, the crude product is collected, ground into a uniform powder, washed with acetone, and then dried under vacuum at 60°C to obtain orange powder PM-COF. (3) Immerse 20 mg PM-COF in 50 mL of 1M KOH solution and stir for 1 h. After centrifugation to collect the solid, wash with water and dry under vacuum at 80 °C to obtain AM-POP.

[0050] 2. Structural characterization PM-COF and AM-POP were observed using scanning electron microscopy, and the results are as follows: Figure 1 As shown, the results indicate that PM-COF is stacked layer by layer in a two-dimensional extended pattern with a fish-scale-like dense arrangement, exhibiting serrated or wavy folds; after hydrolysis, it becomes a three-dimensional cluster of AM-POP, with a visible spiral-like entangled micromorphology and uneven nanoscale protrusions on the surface, and the adsorption sites are densely distributed in the pore network.

[0051] Comparative Example 1: No alkali treatment used Based on Example 1, step (3) was omitted, and orange powder PM-COF was obtained.

[0052] Comparative Example 2: Changing the concentration of alkali treatment 1. Based on Example 1, the concentration of KOH solution in step (3) was changed to 2 M, and the remaining steps were the same as in Example 1, to prepare anionic porous polymer material.

[0053] 2. Based on Example 1, the concentration of KOH solution in step (3) was changed to 0.2 M, and the remaining steps were the same as in Example 1, to prepare anionic porous polymer material.

[0054] Comparative Example 3: Using other COF materials 1. Based on Example 1, other imide COF materials were used to replace PM-COF, and the remaining steps were the same as in Example 1 to prepare porous polymer materials.

[0055] 2. Based on Example 1, alkaline hydrolyzed COF (dp-TH COF) material was used to replace PM-COF, and the remaining steps were the same as in Example 1 to prepare a porous polymer material.

[0056] Example 2: Dye Removal Performance Testing The porous polymer materials prepared in Example 1 (AM-POP) and Comparative Examples 1-3 were tested for performance, as follows: Prepare cationic dye solutions of methylene blue (20–400 mg / L) and crystal violet (20–400 mg / L) respectively. Take 10 mL of each solution and add it to a small glass bottle. Adjust the pH to between 2.0 and 11.0 using 1M hydrochloric acid solution or 1M potassium hydroxide solution. Test the adsorption capacity under different pH conditions.

[0057] Add 1 mg of porous polymer material to the prepared dye aqueous solution, use a polytetrafluoroethylene stir bar, set the electromagnetic stirring table speed between 500 rpm and 800 rpm, and stir for 30 min to 72 h in the dark at room temperature (25 ℃). After reaching adsorption equilibrium for 72 h, filter with a syringe filter equipped with a 0.45 μm microporous MCE membrane to remove the adsorbent and obtain a clear liquid.

[0058] Take the supernatant and use a UV-Vis spectrophotometer to determine the concentration of methylene blue at the maximum absorption wavelength of 664 nm and the concentration of crystal violet at the maximum absorption wavelength of 590 nm.

[0059] (1) Dye removal rate Calculate the removal rate (R) and equilibrium adsorption capacity (Qe) of organic dyes by COF using the following formulas, where C0 and C... e (mg·L) -1 ) represent the initial concentration and equilibrium concentration of the dye solution, respectively; V (mL) is the volume of the dye solution; and m (g) is the mass of the adsorbent sample.

[0060] R(%) = × 100% Q e =

[0061] The results are shown in Table 1. The removal efficiencies of 1 mg of anionic porous organic matter on the dyes in aqueous solutions of 50 mg / L methylene blue and 70 mg / L crystal violet reached 94.7% and 89.6%, respectively.

[0062] Table 1 Dye Removal Rate

[0063] (2) Maximum adsorption capacity Different concentration gradients (25, 50, 75, 100, 200, 300, 400, 500 mol L⁻¹) of various dyes (methylene blue, crystal violet, safranin O, malachite green) were prepared. 2 mg of AM-POP powder was dispersed in 20 mL of the solution and stirred at room temperature (25 °C) for 72 h under light-protected conditions. A small amount of the solution was then filtered through a 0.45 μm microporous MCE membrane to obtain a clear solution. The concentration of the organic dye in the filtrate was calibrated using a UV-Vis spectrophotometer to obtain the curve of its maximum adsorption capacity.

[0064] The results are as follows Figure 3 As shown in Table 2, AM-POP achieved a maximum adsorption capacity of 1061.7 mg g for methylene blue, crystal violet, safranin O, and malachite green, respectively. -1 1142.3 mg g -1 980.4 mg g -1 1047.5 mg g -1 .

[0065] Table 2 Maximum Adsorption Capacity

[0066] (3) Adsorption selectivity 1 mg of AM-POP powder was dispersed in the following dye aqueous solutions (5 mL, 40 mg g each). -1 The solutions were prepared in two ways: 10 mL of a binary dye aqueous solution consisting of MB (methylene blue) and MO (methyl orange); and 10 mL of a binary dye aqueous solution consisting of MO and crystal violet (CV). The solutions were stirred under light-protected conditions, and samples were taken at time points of 3, 5, 10, 30, 60, and 120 min. The samples were filtered through a 0.45 μm microporous MCE membrane to obtain a clear solution. The concentrations of MO, CV, and MB in the filtrate were determined using a UV-Vis spectrophotometer.

[0067] The results are as follows Figure 4 As shown, the results indicate that, thanks to the interaction between cations and anions, POP's removal efficiency for cationic dyes is significantly higher than that for anionic dyes. During the 10-minute adsorption period, the MB peak decreased to disappear, while the MO peak only decreased by 3.4%, indicating that AM-POP possesses excellent selective adsorption capacity for cationic dyes and is suitable for the selective removal of dyes with different charges in complex aqueous environments.

[0068] The adsorption capacity of AM-POP for organic dyes of different ionic types in aqueous solutions of binary mixed dyes was investigated. The initial concentrations of the aqueous solutions of MO and O II were set at 50 mg / L. -1After 4 hours of POP treatment, their removal rates were only 3.5% and 4%, respectively, and the solution color did not change significantly, confirming that AM-POP has excellent adsorption selectivity for cationic dyes.

[0069] (4) Effects of pH and ionic strength of dye water on AM-POP adsorption capacity Use 0.1 mol L -1 HCl and 0.1 mol L -1 Adjust with 100 mg L of NaOH. -1 The pH values ​​of the dye aqueous solutions were 1, 3, 5, 7, and 9. 2 mg of AM-POP powder was dispersed in 20 mL of solution and stirred for 72 h under light-protected conditions. A small amount of solution was taken and filtered through a 0.45 μm microporous MCE membrane to obtain a clear solution. The concentration of the organic dye in the filtrate was calibrated using a UV-Vis spectrophotometer to observe the influence mechanism of electrostatic interactions on the adsorption process.

[0070] To an initial concentration of 70 mg L -1 Methylene blue dye aqueous solution and initial concentration of 50 mg / L -1 Different amounts of NaCl powder were added to the aqueous solution of crystal violet dye to adjust the NaCl concentration in the solution. + The concentrations were 0.01, 0.1, 0.5, and 1 mol L. -1 1 mg of COF was dispersed in 10 mL of solution and stirred for 30 min in the dark. A small amount of solution was then filtered through a 0.45 μm microporous MCE membrane to obtain a clear solution. The concentration of organic dye in the filtrate was determined using a UV-Vis spectrophotometer to investigate the effect of ionic strength on the adsorption effect.

[0071] like Figure 5 As shown, changes in the pH of the aqueous solution affect the charge state and electrostatic interaction strength of the adsorbent and adsorbate, thereby affecting the interaction force between the two adsorbents.

[0072] MB aqueous solutions with pH values ​​varying from 3 to 13 were treated with POP (initial concentration 100 mg / L). -1 The pH was adjusted using HCl and KOH solutions. As the solution pH increased, the adsorption performance of AM-POP for MB improved, indicating that in a weakly alkaline environment, OH... - This facilitates the activation of adsorption sites on POP. These results are consistent with the Zeta potential measurements, which show that the Zeta potential of AM-POP decreases continuously while remaining negative as pH increases, reaching a minimum negative value of -43.34 mV and a maximum adsorption capacity of 985.1 mg g at pH = 11. -1Therefore, it can be inferred that AM-POP has a good adsorption effect on positively charged substances over a relatively wide pH range close to alkalinity.

[0073] In Na + The initial concentration was 0.01 to 1 mol L. -1 In aqueous solutions of the dyes, the removal efficiency of AM-POP for MB and CV cationic dyes remained relatively stable. Only minor fluctuations were observed with increasing ion concentration, indicating that the effect of ionic strength on the adsorption capacity of AM-POP for cationic dyes is negligible.

[0074] (5) Adsorption and regeneration Sodium nitrate was mixed with water in a 1:3 ratio and sonicated to dissolve completely. An equal volume of anhydrous ethanol was then added and sonicated thoroughly to prepare a sodium nitrate ethanol solution for elution.

[0075] AM-POP (10 mg) that had reached adsorption equilibrium was dispersed in 20 mL of eluent (sodium nitrate ethanol solution) and stirred for 3 h. The eluent was then replaced and the process continued. The washed POP was recovered by centrifugation, filtered and washed with water, and the AM-POP material was collected and vacuum dried at 80°C for 12 h.

[0076] The regenerated AM-POP powder was collected and subjected to a continuous cyclic test to remove cationic dyes. At 25°C, 1 mg of AM-POP powder was added to 10 mL of MB and CV dye aqueous solutions (initial dye concentrations were 70 mg / L). -1 and 50 mg L -1 The dye was stirred for 60 minutes, and the dye removal efficiency was determined by ultraviolet absorption spectroscopy.

[0077] Table 3. Adsorption efficiency of AM-POP material for two cationic dyes at different cycle numbers

[0078] The results are shown in Table 3. After 5 cycles, AM-POP exhibited excellent repeatability. In the 5th reuse for MB and CV, its removal performance reached 97.8% and 96.1% respectively, with virtually no decrease. The active sites on the material surface were not significantly lost after cycling. Combined with the hydrophilic properties of AM-POP, it shows great potential in practical applications of dye adsorption in aqueous solutions.

[0079] Example 3: Preparation of nanofiber composite membrane This embodiment prepared a series of POP / polymer composite fiber membranes by optimizing the functional design of AM-POP and spinning process parameters such as voltage and blending ratio. The selective separation mechanism of these membranes for typical cationic dyes was systematically studied, as follows: 1. Preparation of fiber composite membranes by electrospinning 1 mg of polyacrylonitrile (PAN) was uniformly dispersed in 8 mL of dimethylformamide (DMF). After forming a homogeneous and transparent solution by magnetic stirring at room temperature for 6 h, 0~100 mg of AM-POP material was quantitatively added and stirred continuously until completely dispersed to obtain AM-POP@PAN spinning solution.

[0080] The spinning solution was loaded into a 10 mL syringe, and the feed rate was set to 1.5 mL / h. -1 The receiving distance was 15 cm, and spinning was carried out under conditions of 17 kV voltage, 30% humidity and room temperature. After electrospinning, the resulting membrane was placed in a 60°C oven for 12 hours to remove residual solvent, and finally a PAN-AM-X composite membrane was obtained (X represents the amount of AM-POP added).

[0081] 2. Characterization of fiber composite membranes Scanning electron microscope images of PAN-AM-0 and PAN-AM-80 are shown below. Figure 2 As shown, the results indicate that the fibers exhibit a continuous, smooth, narrow, and uniform topological morphology. With an average spinning fineness of 364 nm, POP particles encapsulated by liquid droplets can be observed on the fibers. This encapsulation method ensures that the membrane material does not lose a large amount of POP particles during solution flow, thus guaranteeing the functional preservation of the composite membrane.

[0082] The results show that the organic porous composite membrane exhibits excellent selective separation and adsorption performance for cationic dyes and can be efficiently reused.

[0083] Example 4: Dye separation performance test of PAN-AM-X composite membrane The composite membrane was installed in the sand core filter device (filter cup-filter head assembly). After confirming airtightness, 20 mL of an organic dye aqueous solution of a certain concentration was added to the filter cup, and a vacuum pump was used to drive the process. After the dye solution separation process was completed, the dye concentration in the obtained filtrate was calibrated using a UV-Vis spectrophotometer, and the water flux parameters were recorded simultaneously.

[0084] Based on the above, MB dye was prepared at concentrations of 10, 20, 30, and 40 mg / g. -1 The gradient initial concentration was used to observe the effect of different concentrations on the separation efficiency.

[0085] Furthermore, a binary dye separation experiment was conducted: two dye aqueous solutions were prepared (10 mL each, 20 mg g each). -1A 20 mL binary mixed dye solution (MB and MO) was used to construct a sand core filter. 20 mL of the binary mixed dye aqueous solution was added to the filter cup, and a vacuum pump was used to drive the filter. After the dye solution separation process was completed, the concentrations of the two dyes in the resulting filtrate were calibrated using a UV-Vis spectrophotometer to determine the dye separation performance.

[0086] The results are as follows Figure 6 As shown, the results indicate that, comparing the separation efficiency and water flux of PAN-AM-0 to PAN-AM-100, a regular performance evolution of the composite membrane system can be observed with increasing POP loading. At 100 mg, the MB removal rate is 35.4%, and the water flux generally shows a decreasing trend, from a peak of 7393 L / h. -1 m -2 Reduced to 5093 L h -1 m -2 Based on optimization considerations of separation efficiency and material cost, the composite membrane PAN-AM-80 (with a removal rate of 34.1% and a water flux of 6548 L / h) was selected. -1 m -2 () were the main experimental subjects.

[0087] The effects of different amounts of AM-POP-X on the separation of cationic and anionic dyes are shown in the following results. Figure 7 As shown, the AN-AM-0 membrane has a very low ability to separate organic dyes, confirming that the basic electrospun membrane itself does not have a significant dye separation capability (see...). Figure 4-7 (a)).

[0088] PAN-AM-80 exhibits high separation efficiency for cationic dyes, achieving removal rates of 69.3% for MB and 47.6% for CV. However, it shows almost no removal capacity for anionic dyes MO and O II, with no statistically significant difference in performance compared to the blank membrane. This phenomenon is highly consistent with the specific adsorption characteristics of AM-POP crystals for cationic dyes.

[0089] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing anionic porous polymer materials, characterized in that, Including the following steps: (1) Mix 1,2,4,5-benzenetetracarboxylic acid, 1,3,5-tris(4-aminophenyl)benzene and benzoic acid, heat and react under vacuum, cool, grind, wash and dry to obtain PM-COF; (2) PM-COF and KOH solution were mixed, stirred, centrifuged, washed and dried at a ratio of 20~60 mg: 40~50 mL to obtain anionic porous polymer material; The concentration of the KOH solution is 0.5~1 M.

2. The method according to claim 1, characterized in that, In step (1), the molar ratio of 1,2,4,5-benzenetetracarboxylic acid, 1,3,5-tris(4-aminophenyl)benzene and benzoic acid is 0.8~1.5:0.8~1.5:4~6.

3. The method according to claim 1, characterized in that, In step (1), the heating reaction is carried out at 180~200℃ for 4~6 days.

4. The anionic porous polymer material prepared by the method according to any one of claims 1 to 3.

5. A cationic dye removal product, characterized in that, The product contains the anionic porous polymer material as described in claim 4; The cationic dyes include, but are not limited to, methylene blue, crystal violet, safranin O, and malachite green.

6. A method for preparing nanocomposite thin films, characterized in that, The anionic porous polymer material according to claim 4 was prepared by electrospinning.

7. The method according to claim 6, characterized in that, The electrospinning parameters are: a spinning fineness of 200~600 nm and a feed rate of 1.2~2.0 mL / h. -1 The receiving distance is 12~18 cm, and the voltage is 15~20V.

8. The nanocomposite film prepared by the method of claim 6 or 7.

9. The application of the anionic porous polymer material of claim 4 or the nanocomposite film of claim 8 in dye adsorption, characterized in that, The dye is a cationic dye; The cationic dyes include, but are not limited to, methylene blue, crystal violet, safranin O, and malachite green.

10. A method for simultaneously improving the dye adsorption performance, pH tolerance, and salt ion tolerance of porous polymer materials, characterized in that, Including the following steps: (1) Mix 1,2,4,5-benzenetetracarboxylic acid, 1,3,5-tris(4-aminophenyl)benzene and benzoic acid, heat and react under vacuum, cool, grind, wash and dry to obtain PM-COF; (2) PM-COF and KOH solution were mixed, stirred, centrifuged, washed and dried at a ratio of 20~60 mg: 40~50 mL to obtain anionic porous polymer material; The concentration of the KOH solution is 0.2~1 M.

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