Electrospun in-situ synthesis of NH2-MOF-modified multifunctional air purification nanofiber membrane and its preparation method

Abstract

This invention provides an in-situ electrospinning synthesis method for NH2-MOF-modified multifunctional air-purifying nanofiber membranes. The method includes: S1, preparation of polylactic acid solution; S2, preparation of electrospun polylactic acid fibers; S3, preparation of MOF synthesis precursor solution; S4, preparation of the NH2-MOF-modified multifunctional nanofiber membrane: the electrospun polylactic acid fiber membrane obtained in S1 is immersed in the MOF synthesis precursor solution prepared in S3, and synthesized at a constant temperature in a microwave and ultrasonic environment. After synthesis, it is rinsed with deionized water and dried to obtain the NH2-MOF-modified multifunctional nanofiber membrane. The NH2-MOF-modified multifunctional nanofiber membrane prepared by this invention has advantages such as large specific surface area, strong filtration performance, low air resistance, and strong carbon fixation ability, which solidifies the application prospects of polylactic acid fiber materials in the fields of air filtration and carbon fixation.

Description

Technical Field

[0001] This invention relates to the field of highly efficient air filtration and carbon fixation fully degradable fiber membrane materials, specifically to an electrospinning in-situ synthesis of NH2-MOF multifunctional air purification nanofiber membrane and its preparation method. Background Technology

[0002] Particulate matter pollution and carbon dioxide emissions are major environmental problems facing the world today. These two issues are intertwined and pose a serious threat to human health and ecosystems. Particulate matter (such as PM2.5) 0.3 and PM 2.5 The main sources of particulate matter include industrial emissions, transportation, and agricultural activities. These particulate matter not only affect air quality but are also closely related to various health problems, such as respiratory and cardiovascular diseases, with particularly pronounced effects on children and the elderly. Meanwhile, carbon dioxide (CO2), as a major greenhouse gas, is emitted primarily from the burning of fossil fuels and industrial production, leading to global warming and climate change, which in turn triggers extreme weather events, ecological imbalances, and health risks. Although the direct health hazards of carbon dioxide are relatively small, its climate change effects may lead to declining air quality and resource shortages, indirectly impacting the human living environment. Therefore, addressing the problems of air particulate matter pollution and carbon dioxide emissions, and developing multifunctional nanofiber membranes with high-efficiency, low-resistivity particulate matter filtration and high-efficiency carbon sequestration properties, is of great significance.

[0003] Metal-organic frameworks (MOFs) are complex compounds that self-assemble through coordination bonds between organic ligands and metal ions. Compared to traditional materials, MOFs exhibit larger specific surface areas and higher porosity, and possess structural and functional diversity, thus showing broad application potential in filtration, gas adsorption and separation, and catalysis. Among them, the aminated zeolite imidazole ester framework-8 (NH2-ZIF-8) is a typical MOF material, possessing strong adsorption capacity, high porosity, large specific surface area, and excellent thermal stability. Combining NH2-ZIF-8 with filter materials can significantly improve their filtration performance.

[0004] On the other hand, polylactic acid (PLA), an ideal green material derived from plant-extracted starch, possesses excellent mechanical properties, biocompatibility, and non-toxicity, making it widely used in air filtration. PLA can degrade into carbon dioxide and water in nature and be reused by plants through photosynthesis, demonstrating its recyclability and sustainable development. Furthermore, the presence of chiral centers in the PLA molecular chain exhibits shear piezoelectricity, enabling the generation of voltage through mechanical action without the need for external electric field polarization. This method is simple, efficient, and easily scalable for industrial production. Therefore, combining NH2-ZIF-8 with PLA not only enhances the performance of filter materials but also fully leverages the sustainable advantages of PLA. Summary of the Invention

[0005] Purpose of the invention: To meet the demand for high-efficiency air purification, this invention first prepares a polylactic acid (PLA) fiber membrane with high bulkiness through electrospinning; then, NH2-ZIF-8 is synthesized in situ on the surface of the PLA fiber to obtain an NH2-MOF-modified multifunctional PLA nanofiber membrane. Due to the high bulkiness of the fiber membrane, the synthesis rate of NH2-ZIF-8 on the PLA fiber surface can be significantly improved, resulting in a fiber membrane with advantages such as large specific surface area, strong filtration performance, low air resistance, and strong carbon fixation ability. It is a high-performance air purification material with broad application prospects.

[0006] This invention provides an electrospinning in-situ synthesis of NH2-MOF-based multifunctional air-purifying nanofiber membranes and its preparation method. The method includes the following steps:

[0007] Step S1, Preparation of polylactic acid solution: Dissolve polylactic acid in a solvent to obtain a polylactic acid solution;

[0008] Step S2, preparation of electrospun polylactic acid fibers: The polylactic acid solution obtained in step S1 is electrospun and electrosprayed. The humidity around the Taylor cone is controlled by adjusting the electrospray and the polylactic acid nanofibers are collected on the collector to prepare a polylactic acid nanofiber membrane with high bulkiness.

[0009] Step S3: Preparation of MOF synthesis precursor solution: Dissolve zinc salt, 2-methylimidazole and aminoimidazole in solvent respectively, then slowly add the zinc salt solution to the mixed solution of 2-methylimidazole and aminoimidazole, and mix evenly by stirring to obtain MOF synthesis precursor solution.

[0010] Step S4, Preparation of NH2-MOF multifunctional nanofiber membrane: The polylactic acid nanofiber membrane obtained in step S2 is immersed in the MOF synthesis precursor solution prepared in step S3, and synthesized at a constant temperature in a microwave-assisted environment. At the same time, it is treated by ultrasound to ensure that the synthesized MOF material has uniform size. After the synthesis is completed, it is rinsed with deionized water and dried to obtain the NH2-MOF multifunctional nanofiber membrane.

[0011] In step S1, the solvent is at least one of dimethylformamide, dichloromethane, chloroform, acetone, hexafluoroisopropanol, and ethyl acetate, and the mass ratio of polylactic acid to solvent is 1:20 to 1:4, and the dissolution temperature is 5 to 60°C.

[0012] In step S2, the output voltage of electrospinning is 8–40 kV, the solution consumption rate is 0.2–3 mL / h, the spinning winding speed is 10–1000 rpm, the receiving distance is 5–28 cm, the spinning temperature is 10–45 °C, the humidity is 40%–80%, the average diameter of polylactic acid nanofibers is 100–1000 nm, and the thickness of the fiber membrane is 400–1000 μm.

[0013] In step S2, the electrostatic spraying technology uses an electrospraying solution, which is selected from at least one of deionized water, ethanol, methanol, ethylene glycol, and glycerol. The consumption rate of the electrospraying solution is 1-5 mL / h.

[0014] In step S3, the zinc salt is at least one of zinc nitrate, zinc acetate, zinc sulfate, zinc chloride, and zinc gluconate, and the amino imidazole is at least one of 2-aminobenzimidazole, 2-aminoimidazolium, 1-3-aminopropylimidazolium, and 4-aminoimidazolium.

[0015] In step S3, the solvent is at least one of deionized water, anhydrous ethanol, methanol, ethylene glycol, isopropanol, dimethyl thionamide, and dimethylformamide; the mass ratio of 2-methylimidazole to zinc salt is 1:1 to 8:1; the mass ratio of aminoimidazole to zinc salt is 1:1 to 4:1; and the mass ratio of zinc salt to solvent is 1:1000 to 1:100.

[0016] In step S3, the zinc salt solution is slowly added to the mixed solution of 2-methylimidazole and aminoimidazole at a rate of 5-100 mL / min, with a stirring speed of 50-500 rpm and a stirring time of 10-30 min.

[0017] In step S4, the microwave output power used is 100-1000W, the synthesis temperature is 30-100℃, the ultrasonic power is 100-500W, the ultrasonic frequency is 0.5-20KHz, the ultrasonic power adjustable range is 20%-100%, the synthesis time is 2-80min, the stirring speed is 0-600rpm, and the average particle size of the MOF material is 10-990nm.

[0018] In step S4, the drying method used is one of atmospheric pressure drying, vacuum drying, freeze drying, vacuum drying, and microwave drying.

[0019] This invention also provides an electrospinning in-situ synthesis of NH2-MOF multifunctional air-purifying nanofiber membrane, prepared using the method described above.

[0020] The electrospun in-situ synthesized NH2-MOF multifunctional air-purifying nanofiber membrane provided by this invention has significant advantages in particulate matter filtration and carbon fixation. Firstly, supported by its high specific surface area and nanoporous structure, this material can effectively capture fine particulate matter (such as PM2.5) in the air. 0.3 and PM 2.5 This nanofiber membrane enhances the particulate matter removal efficiency of air purification equipment and is suitable for applications requiring high-efficiency particulate filtration, such as air purifiers, ventilation systems, and personal protective masks. Furthermore, due to the excellent adsorption capacity of the NH2-MOF structure for greenhouse gases such as CO2, this nanofiber membrane also exhibits outstanding carbon sequestration effects, enabling it to capture and adsorb CO2, reducing industrial emissions and carbon pollution in the environment. This material has broad application potential in air filtration and greenhouse gas emission reduction, providing innovative technological solutions for improving air quality and controlling carbon emissions in industrial, residential, and transportation environments.

[0021] Beneficial Effects: The present invention provides an electrospinning in-situ synthesis method for NH2-MOF-modified multifunctional air-purifying nanofiber membranes. This method involves preparing polylactic acid nanofibers with high bulkiness and then directly synthesizing NH2-ZIF-8 on the surface of each nanofiber in the bulky fiber membrane using a microwave-assisted in-situ synthesis method, thereby obtaining a fully loaded NH2-MOF-modified multifunctional air-purifying nanofiber membrane. The specific surface area of ​​this nanofiber membrane is 300-500 m² / g. 2 / g, at a gas flow rate of 32L / min, for PM 2.5 Its filtration efficiency is 99%–99.9%, effective against PM2.5. 0.3The filtration efficiency is 98%–99.9%, the air resistance is less than 40 Pa, and the carbon fixation rate can reach 90%–95%. The preparation method is simple and the conditions are controllable. The prepared multifunctional air purification nanofiber membrane has significant characteristics such as large specific surface area, strong filtration performance, low air resistance, and strong carbon fixation ability, which effectively extends the application of biodegradable materials in air filtration and CO2 capture. Attached Figure Description

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0023] Figure 1 This is a flowchart of the method of the present invention.

[0024] Figure 2 This is a schematic diagram of the morphology of the NH2-MOF-modified multifunctional nanofiber membrane prepared in Example 1, observed by SEM.

[0025] Figure 3 This is a schematic diagram of the morphology of the NH2-MOF-modified multifunctional nanofiber membrane prepared in Example 2, observed by SEM.

[0026] Figure 4 This is a schematic diagram of the morphology of the NH2-MOF-modified multifunctional nanofiber membrane prepared in Example 3, observed by SEM. Detailed Implementation

[0027] Example 1

[0028] like Figure 1 As shown, this embodiment provides a method for preparing an electrospinning in-situ synthesized NH2-MOF multifunctional air purification nanofiber membrane, including the following steps:

[0029] S11. Preparation of polylactic acid solution: At 30℃, 1g of polylactic acid is completely dissolved in 10mL of chloroform to prepare a polylactic acid solution;

[0030] S12. Preparation of electrospun polylactic acid (PLA) fibers: 1.5 mL of the PLA solution prepared in S11 was placed in a syringe. Under the conditions of a set output voltage of 20 kV, a solution feed rate of 1 mL / h, a fiber winding speed of 100 rpm, a spinning temperature of 30℃, and a humidity of 70%, deionized water was sprayed out at a feed rate of 2 mL / h to form a mist environment around the PLA Taylor cone. High-loft PLA nanofiber membranes were then spun into a high-loft PLA nanofiber membrane with an average fiber diameter of 400 nm and a membrane thickness of 800 μm.

[0031] S13. Preparation of MOF synthesis precursor solution: First, dissolve 0.5g of zinc nitrate in 100mL of water. Then, dissolve 1g of 2-methylimidazole and 2g of 2-aminobenzimidazole in 100mL of water. Add the zinc nitrate solution to the mixed solution of 2-methylimidazole and 2-aminobenzimidazole at a rate of 50mL / min and stir at 400rpm for 20min to obtain the MOF synthesis precursor solution.

[0032] Preparation of S14 NH2-MOF-based multifunctional nanofiber membrane: The electrospun polylactic acid fiber membrane obtained in S12 was immersed in the MOF synthesis precursor solution prepared in S13, and then placed in a microwave-assisted environment for in-situ synthesis. The microwave output power was 500W, the synthesis temperature was 60℃, and the membrane was subjected to ultrasonic treatment with an ultrasonic power of 250W, an ultrasonic frequency of 10KHz, and an ultrasonic power adjustment of 50%. The synthesis time was set to 30min, the stirring speed was 200rpm, and after the reaction was completed, the membrane was rinsed with deionized water and dried to obtain the NH2-MOF-based multifunctional nanofiber membrane. The average size of the synthesized NH2-MOF material was 100nm.

[0033] Example 2

[0034] This embodiment provides a method for preparing an electrospun in-situ synthesized NH2-MOF multifunctional air purification nanofiber membrane, including the following steps:

[0035] S21. Preparation of polylactic acid solution: At 60℃, 2.5g of polylactic acid is completely dissolved in 10mL of acetone to prepare a polylactic acid solution.

[0036] S22. Preparation of electrospun polylactic acid (PLA) fibers: 0.6 mL of the PLA solution prepared in S21 was placed in a syringe. Under the conditions of a set output voltage of 40 kV, a solution feed rate of 0.2 mL / h, a fiber winding speed of 1000 rpm, a spinning temperature of 10℃, and a humidity of 80%, ethanol was sprayed out at a feed rate of 5 mL / h to form a mist environment around the PLA Taylor cone. High-loft PLA nanofiber membranes were then spun into a high-loft PLA nanofiber membrane with an average fiber diameter of 800 nm and a membrane thickness of 400 μm.

[0037] S23. Preparation of MOF synthesis precursor solution: First, dissolve 0.2g of zinc chloride in 100mL of water. Then, dissolve 1.6g of 2-methylimidazole and 0.2g of 2-aminoimidazole in 100mL of anhydrous ethanol. Add the zinc chloride solution to the mixed solution of 2-methylimidazole and 2-aminoimidazole at a rate of 100mL / min and stir at 500rpm for 30min to obtain the MOF synthesis precursor solution.

[0038] Preparation of S24 NH2-MOF-based multifunctional nanofiber membrane: The electrospun polylactic acid fiber membrane obtained in S22 was immersed in the MOF synthesis precursor solution prepared in S23, and then placed in a microwave-assisted environment for in-situ synthesis. The microwave output power was 1000W, the synthesis temperature was 100℃, and the membrane was subjected to ultrasonic treatment with an ultrasonic power of 500W, an ultrasonic frequency of 20KHz, and an ultrasonic power adjustment of 90%. The synthesis time was set to 10min, the stirring speed was 0rpm, and after the reaction was completed, the membrane was rinsed with deionized water and dried to obtain the NH2-MOF-based multifunctional nanofiber membrane. The average size of the synthesized NH2-MOF material was 200nm.

[0039] Example 3

[0040] This embodiment provides a method for preparing an electrospun in-situ synthesized NH2-MOF multifunctional air purification nanofiber membrane, including the following steps:

[0041] S31. Preparation of polylactic acid solution: At 5℃, 0.5g of polylactic acid is completely dissolved in 10mL of hexafluoroisopropanol to prepare a polylactic acid solution.

[0042] S32. Preparation of electrospun polylactic acid (PLA) fibers: Take 3 mL of the PLA solution prepared in S31 into a syringe. Under the conditions of set output voltage of 8 kV, solution feed rate of 3 mL / h, fiber winding speed of 10 rpm, spinning temperature of 45℃, and humidity of 40%, a mixed solution of methanol and water (1:1) is sprayed out at a feed rate of 1 mL / h to form a mist environment around the PLA Taylor cone. High-loft PLA nanofiber membranes are spun into high-loft PLA nanofiber membranes with an average fiber diameter of 300 nm and a membrane thickness of 600 μm.

[0043] S33. Preparation of MOF synthesis precursor solution: First, dissolve 1g of zinc acetate in 50mL of water. Then, dissolve 2g of 2-methylimidazole and 4g of 4-aminoimidazole in 50mL of dimethylformamide. Then, add the zinc acetate solution to the mixed solution of 2-methylimidazole and 4-aminoimidazole at a rate of 5mL / min and stir at 50rpm for 30min to obtain the MOF synthesis precursor solution.

[0044] Preparation of S34 NH2-MOF-based multifunctional nanofiber membrane: The electrospun polylactic acid fiber membrane obtained in S32 was immersed in the MOF synthesis precursor solution prepared in S33, and then placed in a microwave-assisted environment for in-situ synthesis. The microwave output power was 100W, the synthesis temperature was 30℃, and the membrane was subjected to ultrasonic treatment with an ultrasonic power of 100W, an ultrasonic frequency of 0.5KHz, and an ultrasonic power adjustment of 20%. The synthesis time was set to 80min, the stirring speed was 300rpm, and after the reaction was completed, the membrane was rinsed with deionized water and dried to obtain the NH2-MOF-based multifunctional nanofiber membrane. The average size of the synthesized NH2-MOF material was 300nm.

[0045] Example 4

[0046] This embodiment provides a method for preparing an electrospun in-situ synthesized NH2-MOF multifunctional air purification nanofiber membrane, including the following steps:

[0047] S41. Preparation of polylactic acid solution: At 20℃, 1.5g of polylactic acid is completely dissolved in 10mL of a mixed solution of dichloromethane and dimethylformamide (mass ratio of 1:1) to obtain a polylactic acid solution.

[0048] S42. Preparation of electrospun polylactic acid (PLA) fibers: Take 1 mL of the PLA solution prepared in S41 into a syringe. Under the conditions of a set output voltage of 20 kV, a solution feed rate of 0.8 mL / h, a fiber winding speed of 200 rpm, a spinning temperature of 35℃, and a humidity of 60%, water is sprayed out at a feed rate of 2 mL / h to form a mist environment around the PLA Taylor cone. High-loft PLA nanofiber membranes are then spun to obtain a high-loft PLA nanofiber membrane with an average fiber diameter of 500 nm and a membrane thickness of 500 μm.

[0049] S43. Preparation of MOF synthesis precursor solution: First, dissolve 0.8g of zinc gluconate in 120mL of water. Then, dissolve 0.8g of 2-methylimidazole and 2.4g of 1-3-aminopropylimidazole in 120mL of isopropanol. Then, add the zinc gluconate solution to the mixed solution of 2-methylimidazole and 1-3-aminopropylimidazole at a rate of 50mL / min and stir at 200rpm for 20min to obtain the MOF synthesis precursor solution.

[0050] Preparation of NH2-MOF-modified multifunctional nanofiber membrane: The electrospun polylactic acid fiber membrane obtained in S42 was immersed in the MOF synthesis precursor solution prepared in S43, and then placed in a microwave-assisted environment for in-situ synthesis. The microwave output power was 800W, the synthesis temperature was 70℃, and the membrane was subjected to ultrasonic treatment with an ultrasonic power of 400W, an ultrasonic frequency of 15KHz, and an ultrasonic power adjustment of 70%. The synthesis time was set to 15min, the stirring speed was 200rpm, and after the reaction was completed, the membrane was rinsed with deionized water and dried to obtain the NH2-MOF-modified multifunctional nanofiber membrane. The average size of the synthesized NH2-MOF material was 300nm.

[0051] Comparative Example 1 (no foggy space formed around the Taylor cone)

[0052] The NH2-MOF multifunctional nanofiber membrane was prepared using the method described in Example 1. The difference was that no electrospinning solution was added to create a spray space during electrospinning in this example. Specifically, S11, preparation of polylactic acid solution: 1g of polylactic acid was completely dissolved in 10mL of chloroform at 30°C to obtain a polylactic acid solution; S12, preparation of electrospun polylactic acid fibers: 1.5mL of the polylactic acid solution prepared in S11 was placed in a syringe, and polylactic acid nanofiber membranes were spun under the following conditions: output voltage of 20kV, solution feed rate of 1mL / h, fiber winding speed of 100rpm, spinning temperature of 30°C, and humidity of 70%. A high-bulk polylactic acid nanofiber membrane with an average fiber diameter of 400nm and a membrane thickness of 800μm was obtained; S13, preparation of MOF synthesis precursor solution: First, 0.5g of zinc nitrate was dissolved in 100mL of water, and then 1g of 2-methylimidazole and 2g of... 2-Aminobenzimidazole was dissolved in 100 mL of water. Then, zinc nitrate solution was added to the mixed solution of 2-methylimidazole and 2-aminobenzimidazole at a rate of 50 mL / min, and the mixture was stirred at 400 rpm for 20 min to obtain the MOF synthesis precursor solution. Preparation of S14 NH2-MOF-modified multifunctional nanofiber membrane: The electrospun polylactic acid fiber membrane obtained in S12 was immersed in the MOF synthesis precursor solution prepared in S13, and then placed in a microwave-assisted environment for in-situ synthesis. The microwave output power was 500 W, the synthesis temperature was 60 °C, and the membrane was subjected to ultrasonic treatment with a power of 250 W, a frequency of 10 kHz, and a power adjustment of 50%. The synthesis time was set to 30 min, and the stirring speed was 200 rpm. After the reaction, the membrane was rinsed with deionized water and allowed to stand and dry to obtain the NH2-MOF-modified multifunctional nanofiber membrane. The average size of the synthesized NH2-MOF material was 100 nm.

[0053] Comparative Example 2 (Amino-imidazoles were not used in the preparation of the NH2-MOF synthesis precursor solution)

[0054] The NH2-MOF multifunctional nanofiber membrane was prepared using the method described in Example 2. The difference was that amino-based imidazoles were not used in the preparation of the NH2-MOF synthesis precursor solution in this example. Specifically, S21, preparation of polylactic acid solution: 2.5g of polylactic acid was completely dissolved in 10mL of acetone at 60℃ to prepare a polylactic acid solution; S22, preparation of electrospun polylactic acid fibers: 0.6mL of the polylactic acid solution prepared in S21 was placed in a syringe. Under the conditions of a set output voltage of 40kV, a solution feed rate of 0.2mL / h, a fiber winding speed of 1000rpm, a spinning temperature of 10℃, and a humidity of 80%, ethanol was sprayed at a feed rate of 5mL / h to form a mist environment around the polylactic acid Taylor cone. High-loft polylactic acid nanofiber membranes were spun to obtain a high-loft polylactic acid nanofiber membrane with an average fiber diameter of 800nm ​​and a membrane thickness of 400μm; S23, preparation of MOF synthesis precursor solution: First, 0.2g of zinc chloride was dissolved in 100mL of water, and then 1.8g of... 2-Methylimidazole was dissolved in 100 mL of anhydrous ethanol. Zinc chloride solution was then added to the 2-methylimidazole solution at a rate of 100 mL / min, and the mixture was stirred at 500 rpm for 30 min to obtain the MOF synthesis precursor solution. Preparation of S24, NH2-MOF-modified multifunctional nanofiber membrane: The electrospun polylactic acid fiber membrane obtained in S22 was immersed in the MOF synthesis precursor solution prepared in S23. It was then placed in a microwave-assisted environment for in-situ synthesis. The microwave output power was 1000 W, the synthesis temperature was 100℃, and the membrane was subjected to ultrasonic treatment at a power of 500 W, a frequency of 20 kHz, and a power adjustment of 90%. The synthesis time was set to 10 min, and the stirring speed was 0 rpm. After the reaction, the membrane was rinsed with deionized water and allowed to stand and dry to obtain the NH2-MOF-modified multifunctional nanofiber membrane. The average size of the synthesized NH2-MOF material was 200 nm.

[0055] Comparative Example 3 (In the preparation of NH2-MOF multifunctional nanofiber membranes, microwave + ultrasound-assisted in-situ synthesis was not used)

[0056] The NH2-MOF-modified multifunctional nanofiber membrane was prepared using the method described in Example 3. However, in this example, microwave-assisted in-situ synthesis was not used in the preparation of the NH2-MOF-modified multifunctional nanofiber membrane. Specifically, S31, Polylactic Acid Solution Preparation: At 5℃, 0.5g of polylactic acid was completely dissolved in 10mL of hexafluoroisopropanol to prepare a polylactic acid solution; S32, Electrospun Polylactic Acid Fiber Preparation: 3mL of the polylactic acid solution prepared in S31 was placed in a syringe. Under the conditions of an output voltage of 8kV, a solution propulsion speed of 3mL / h, a fiber winding speed of 10rpm, a spinning temperature of 45℃, and a humidity of 40%, a mixed solution of methanol and water (1:1) was sprayed at a propulsion speed of 1mL / h to form a mist environment around the polylactic acid Taylor cone. High-loft polylactic acid nanofiber membranes with an average fiber diameter of 300nm and a membrane thickness of 600μm were obtained by spinning; S33, MOF Synthesis Precursor Solution Preparation: First, 1g of zinc acetate was dissolved in 50mL of water, and then 2g of 2-methylimidazole and 4g of... 4-Aminoimidazole was dissolved in 50 mL of dimethylformamide. Then, zinc acetate solution was added to the mixed solution of 2-methylimidazole and 4-aminoimidazole at a rate of 5 mL / min, and the mixture was stirred at 50 rpm for 30 min to obtain the MOF synthesis precursor solution. Preparation of S34, NH2-MOF-modified multifunctional nanofiber membrane: The electrospun polylactic acid fiber membrane obtained in S32 was immersed in the MOF synthesis precursor solution prepared in S33, and then placed in a microwave-assisted environment for in-situ synthesis. The microwave output power was 100 W, the synthesis temperature was 30 °C, and the membrane was subjected to ultrasonic treatment with a power of 100 W, a frequency of 0.5 kHz, and a power adjustment of 20%. The synthesis time was set to 80 min, and the stirring speed was 300 rpm. After the reaction, the membrane was rinsed with deionized water and allowed to stand and dry to obtain the NH2-MOF-modified multifunctional nanofiber membrane. The average size of the synthesized NH2-MOF material was 300 nm.

[0057] Structural characterization and performance testing

[0058] Scanning electron microscopy (SEM) observation: The microstructure of the NH2-MOF multifunctional nanofiber membrane was observed using a field emission scanning electron microscope (model JSM-7900F, NEC). Figure 2 , Figure 3 and Figure 4 (As shown).

[0059] Specific surface area test: Nitrogen adsorption isotherm was measured at 77K using a gas adsorption meter (ASAP 2060, Micromeritics, USA).

[0060] Filtration performance testing: An LZC-K type automatic filter media tester (Suzhou Huada Instrument Equipment Co., Ltd.) was used to test the filter media under the same area (113.04 cm²). 2 The air filtration performance and pressure drop parameters of triboelectric self-powered polylactic acid fiber filter membranes were tested. The gas flow rate was set to 32 L / min. At least three different locations were tested for each group of fiber membranes, and the average value of the results was taken.

[0061] CO2 adsorption performance test: Using a self-built gas adsorption performance test platform, medical-grade CO2 with a concentration of 99.5% was used, and an appropriate amount of CO2 was introduced into the test platform using a standard commercial regulator. The concentration of CO2 was monitored in real time using a portable CO2 sensor, and the adsorption efficiency of the nanofiber membrane on the gas was calculated after 1 hour of adsorption.

[0062] Antimicrobial activity test: Staphylococcus aureus and Escherichia coli were cultured in contact with and without NH2-MOF multifunctional nanofiber membranes, respectively. The number of bacteria in the culture dishes was counted and the antimicrobial efficiency of NH2-MOF multifunctional nanofiber membrane against different bacteria was calculated.

[0063] Experimental results: such as Figure 2 As shown, in Example 1, the NH2-MOF multifunctional nanofiber membrane produced exhibits a significant synthesis of NH2-ZIF-8 nanoparticles on its fiber surface. Furthermore, the NH2-ZIF-8 is synthesized relatively uniformly on the fiber surface, which significantly increases the contact sites of NH2-ZIF-8 with particulate matter and gas, facilitating efficient capture and adsorption. Figure 3 and Figure 4 The SEM images also show that relatively uniform NH2-ZIF-8 nanoparticles were synthesized on the surface of the fiber.

[0064] Furthermore, Table 1 shows the performance test results of Examples 1-4 and Comparative Examples 1-4. As can be seen from the table, the highest specific surface area of ​​Examples 1-4 can reach 444.8 m². 2 With a surface area of ​​ / g, it possesses excellent specific surface area, providing more adsorption sites for the polylactic acid nanofiber membrane to capture particulate matter and adsorb toxic gases. Notably, in Comparative Example 2, the specific surface area of ​​its nanofiber membrane also reached 344.7m². 2 / g, which is significantly better than other comparative examples. This is mainly because, although no amino imidazole was added, the presence of 2-methylimidazolium also promoted the synthesis of ZIF-8 on the fiber surface, thus exhibiting a higher specific surface area.

[0065] Table 1

[0066]

[0067] Simultaneously, PM was filtered out at a high airflow rate of 32 L / min. 2.5 and PM 0.3 The performance of PM was measured, as shown in Table 1. Examples 1-4 tested PM... 0.3 Its filtration efficiency can reach 99.2% to 99.7%, effective against PM2.5. 2.5 The filtration efficiency can reach 99.7% to 99.9%. Compared with Comparative Examples 1 to 3, the examples show superior filtration performance. This is mainly because, compared with the more densely packed fiber membrane (Comparative Example 1), the high-loft fiber membrane can significantly improve the interception efficiency of particulate matter inside the fiber membrane. In addition, the high-loft fiber membrane is more conducive to the uniform synthesis of NH2-ZIF-8 on the fibers inside the fiber membrane, thereby better improving the filtration efficiency. Comparative Example 2 also shows better filtration efficiency, mainly because ZIF-8 is also better synthesized on the loose fibers. The large specific surface area is also conducive to its efficient interception of particulate matter. Comparative Example 3 shows better filtration efficiency for PM2.5. 0.3 and PM 2.5 The filtration efficiencies were only 83.4% and 90.27%, mainly due to the lack of microwave-assisted catalysis. The in-situ synthesis at a constant temperature for a short time made it difficult to synthesize complete NH2-ZIF-8 nanoparticles, thus limiting the interception of particulate matter and relying primarily on the interception of the fiber membrane itself. Secondly, due to its high bulkiness, the prepared NH2-MOF multifunctional nanofiber membrane also exhibited extremely low air resistance; in Examples 1-4, the air resistance at 32 L / min was no higher than 40 Pa.

[0068] Table 1 compares the antimicrobial activity of NH2-MOF-modified multifunctional nanofiber membranes. The data shows that the antimicrobial efficiency of all examples is above 97%, and Comparative Example 2 also achieves 97% antimicrobial activity. This indicates that the NH2-MOF-modified multifunctional nanofiber membrane has the effect of inactivating microorganisms. This is mainly because NH2-ZIF-8 has good antimicrobial activity and can inactivate microorganisms. The high bacterial filtration efficiency of Comparative Example 2 is mainly attributed to ZIF-8. The lower antimicrobial performance of Comparative Examples 1 and 3 is mainly due to the dense fiber membrane structure in Comparative Example 1, which is not conducive to the synthesis of NH2-ZIF-8 on the fiber surface, and the lack of microwave catalytic assistance in Comparative Example 3, making it difficult to synthesize complete NH2-ZIF-8 nanoparticles in a short-term isothermal synthesis.

[0069] Table 1 also compares the CO2 adsorption efficiency of NH2-MOF multifunctional nanofiber membranes. It can be seen that Examples 1-4 exhibited excellent CO2 adsorption performance, with the highest adsorption efficiency reaching 94.5%. This is mainly due to the uniform synthesis of NH2-ZIF-8 nanoparticles on the fiber surface, providing a higher specific surface area for the fiber membrane. The fluffy fibers provide more contact sites with CO2, thus enabling higher CO2 adsorption. Furthermore, the amino functional groups on NH2-ZIF-8 are weakly basic and can react chemically with weakly acidic gases like CO2, which is also more conducive to CO2 adsorption and capture. Meanwhile, tests revealed that while Comparative Example 2 had a high particulate matter filtration efficiency, its CO2 adsorption efficiency was lower. This is mainly attributed to the limited CO2 adsorption capacity of the ZIF-8 synthesized in Comparative Example 2.

[0070] This demonstrates that the polylactic acid nanofiber membrane with high bulkiness prepared by the method described in this invention, and the NH2-ZIF-8 nanoparticles synthesized in situ on the fiber surface by microwave assistance, resulting in an NH2-MOF-based multifunctional nanofiber membrane with high specific surface area, high filtration efficiency, low air resistance, high antibacterial properties, and high CO2 adsorption capacity, has broad application prospects.

[0071] This invention provides an electrospinning in-situ synthesis method for NH2-MOF multifunctional air-purifying nanofiber membranes and its preparation method. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for preparing NH2-MOF-based multifunctional air-purifying nanofiber membranes through electrospinning in situ, characterized in that, Includes the following steps: Step S1, Preparation of polylactic acid solution: Dissolve polylactic acid in a solvent to obtain a polylactic acid solution; Step S2, preparation of electrospun polylactic acid fibers: The polylactic acid solution obtained in step S1 is electrospun and electrosprayed. The humidity around the Taylor cone is controlled by adjusting the electrospray and the polylactic acid nanofibers are collected on the collector to prepare a polylactic acid nanofiber membrane with high bulkiness. Step S3: Preparation of MOF synthesis precursor solution: Dissolve zinc salt, 2-methylimidazole and aminoimidazole in solvent respectively, then slowly add the zinc salt solution to the mixed solution of 2-methylimidazole and aminoimidazole, and mix evenly by stirring to obtain MOF synthesis precursor solution. Step S4: Preparation of NH2-MOF-modified multifunctional nanofiber membrane: The polylactic acid nanofiber membrane obtained in step S2 is immersed in the MOF synthesis precursor solution prepared in step S3, and synthesized at a constant temperature in a microwave-assisted environment. At the same time, it is treated by ultrasound to ensure that the synthesized MOF material has uniform size. After the synthesis is completed, it is rinsed with deionized water and dried to obtain the NH2-MOF-modified multifunctional nanofiber membrane.

2. The method according to claim 1, characterized in that, In step S1, the solvent is at least one of dimethylformamide, dichloromethane, chloroform, acetone, hexafluoroisopropanol, and ethyl acetate, and the mass ratio of polylactic acid to solvent is 1:20 to 1:4, and the dissolution temperature is 5 to 60°C.

3. The method according to claim 2, characterized in that, In step S2, the output voltage of electrospinning is 8–40 kV, the solution consumption rate is 0.2–3 mL / h, the spinning winding speed is 10–1000 rpm, the receiving distance is 5–28 cm, the spinning temperature is 10–45 °C, the humidity is 40%–80%, the average diameter of polylactic acid nanofibers is 100–1000 nm, and the thickness of the fiber membrane is 400–1000 μm.

4. The method according to claim 3, characterized in that, In step S2, the electrostatic spraying technology uses an electrospraying solution, which is selected from at least one of deionized water, ethanol, methanol, ethylene glycol, and glycerol. The consumption rate of the electrospraying solution is 1-5 mL / h.

5. The method according to claim 4, characterized in that, In step S3, the zinc salt is at least one of zinc nitrate, zinc acetate, zinc sulfate, zinc chloride, and zinc gluconate, and the amino imidazole is at least one of 2-aminobenzimidazole, 2-aminoimidazolium, 1-3-aminopropylimidazolium, and 4-aminoimidazolium.

6. The method according to claim 5, characterized in that, In step S3, the solvent is at least one of deionized water, anhydrous ethanol, methanol, ethylene glycol, isopropanol, dimethyl thionamide, and dimethylformamide; the mass ratio of 2-methylimidazole to zinc salt is 1:1 to 8:1; the mass ratio of aminoimidazole to zinc salt is 1:1 to 4:1; and the mass ratio of zinc salt to solvent is 1:1000 to 1:

100.

7. The method according to claim 6, characterized in that, In step S3, the zinc salt solution is slowly added to the mixed solution of 2-methylimidazole and aminoimidazole at a rate of 5-100 mL / min, with a stirring speed of 50-500 rpm and a stirring time of 10-30 min.

8. The method according to claim 7, characterized in that, In step S4, the microwave output power used is 100-1000W, the synthesis temperature is 30-100℃, the ultrasonic power is 100-500W, the ultrasonic frequency is 0.5-20KHz, the ultrasonic power adjustable range is 20%-100%, the synthesis time is 2-80min, the stirring speed is 0-600rpm, and the average particle size of the MOF material is 10-990nm.

9. The method according to claim 8, characterized in that, In step S4, the drying method used is one of atmospheric pressure drying, vacuum drying, freeze drying, vacuum drying, and microwave drying.

10. Electrospinning in-situ synthesis of NH2-MOF-based multifunctional air-purifying nanofiber membrane, characterized in that, Prepared using the method described in any one of claims 1 to 9.

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