Multi-micropore refined low-resistance-consumption fiber membrane as well as preparation method and application thereof

Abstract

The invention provides a microporous refined low-resistance-consumption fiber membrane and a preparation method and application thereof.The method comprises the following steps that S1, polylactic acid is dissolved in a solvent A according to a specific proportion, a proper amount of solvent B is added, and a modified spinning mixed solution is prepared by optimizing the fiber diameter; s2, dissolving a metal salt and a connecting agent in a solvent C and a solvent D to prepare a metal organic framework (MOF) precursor solution; s3, preparing MOF nanosheets from the MOF precursor solution obtained in the step S2 through a wet chemical synthesis method; and step S4, preparing the microporous refined low-resistance-consumption fiber membrane from the modified spinning mixed solution obtained in the step S1 and the MOF nanosheets obtained in the step S3 through a spinning technology. The fiber membrane prepared by the invention has a series of advantages of higher specific surface area, lower resistance consumption, high gas adsorption capacity, stable filtering efficiency and the like, and is a filtering material which is wide in application field and excellent in performance.

Description

Technical Field

[0001] The present invention relates to the technical field of controllable synthesis realized by using a fiber membrane template, and particularly relates to a multi-micropore refined low-resistance fiber membrane, a preparation method thereof and an application thereof. Background Art

[0002] With the significant increase in energy consumption, greenhouse gas (GHG) emissions have increased rapidly, which has become one of the most concerned issues for researchers. Carbon dioxide (CO2) is one of the main greenhouse gases, and its excessive emissions have certain harms to the climate, ecosystem and human society. For example, in terms of climate, it can absorb ground radiation and prevent heat from dissipating into space. As its emissions increase, the heat preservation effect of the Earth's atmosphere continues to strengthen, resulting in a continuous rise in the global average temperature, and further leading to the aggravation of global warming and the frequent occurrence of extreme climate events. Among different CO2 emission sources, power plants are the largest CO2 emitters. Due to the increasing global energy demand, the number of power plants has gradually increased, and the CO2 emissions have also increased accordingly.

[0003] To protect the environment, researchers are developing various technologies to capture CO2 generated after the combustion of power plants. Traditional CO2 capture technologies mainly include physical absorption method, chemical absorption method, oxy-fuel combustion method, membrane separation method, adsorption method, etc. Although these methods can capture CO2 to a certain extent, they are not so convenient and have many defects. For example, in the physical absorption method, this technology is only applicable to the environment with high-concentration CO2, and has poor selectivity and requires high-pressure operation. The chemical absorption method has high energy consumption, and the absorbent will undergo oxidative loss during the operation process and needs to be continuously supplemented, resulting in high costs and relatively cumbersome operations. Similar problems also exist in several other methods. Therefore, finding new technologies to capture CO2 is an urgent problem at present. Recently, the development of porous materials has been very remarkable in basic research and potential applications. In particular, metal-organic frameworks (MOFs) composed of inorganic and organic species have attracted much attention due to their designable structures / pores, wide range of components, high porosity and easy functionalization. MOF materials have shown great potential in the field of CO2 adsorption due to their unique structural and performance advantages, and have become a research hotspot in recent years.

[0004] MOFs are crystalline porous materials with a periodic network structure formed by connecting inorganic metal ions or metal clusters with carboxylic acid-containing or nitrogen-containing organic ligands through coordination bonds. The following characteristics make them highly concerned in CO2 adsorption: (1) MOF materials can provide a large number of adsorption sites, increasing the binding probability between CO2 and the material, thereby improving the adsorption capacity. For example, the specific surface area of some MOF materials can be as high as several thousand square meters per gram; (2) By selecting different metal ions, organic ligands, and synthesis methods, the structure and pore size of MOFs can be precisely regulated to adapt to different CO2 adsorption application scenarios and achieve selective adsorption of CO2; (3) MOF materials can be designed and synthesized with pore channels of specific pore sizes and shapes according to needs, enabling CO2 to diffuse and adsorb more effectively in the pores, while restricting the entry of other gas molecules and improving the selectivity of CO2.

[0005] It can be expected that MOF materials are combined with electrospinning technology to prepare more efficient and characteristic fiber membranes. In previous experiments, it was found that UIO-66 can be combined with electrospun fibers to obtain a fiber membrane with good specific surface area and chemical stability; ZIF-8 is combined with electrospinning to obtain a fiber membrane with strong adsorption capacity and antibacterial properties. Summary of the Invention

[0006] The main purpose of the present invention is to prepare a multi-microporous refined low-resistance fiber membrane capable of synergistically filtering dust and capturing CO2 to solve the problems of poor dust filtration and CO2 capture efficiency and poor durability of existing filtering materials.

[0007] To achieve the above purpose, the present invention provides a multi-microporous refined low-resistance fiber membrane and its preparation method and application. According to the first aspect of the present invention, a preparation method of a multi-microporous refined low-resistance fiber membrane is provided, including the following steps: Step S1, preparation of a modified spinning mixture: Dissolve polylactic acid (PLA) in solvent A in a specific proportion, and add an appropriate amount of solvent B to prepare a modified spinning mixture by optimizing the fiber diameter; Step S2, preparation of a MOF precursor solution: Dissolve metal salts and linkers in solvent C and solvent D to prepare a MOF precursor solution; Step S3, preparation of MOF nanosheets: Prepare MOF nanosheets from the MOF precursor solution obtained in Step S2 by a wet chemical synthesis method; Step S4, preparation of a multi-microporous refined low-resistance fiber membrane: Prepare a multi-microporous refined low-resistance fiber membrane from the modified spinning mixture obtained in Step S1 and the MOF nanosheets obtained in S3 by a spinning technique.

[0008] Preferably, in step S1, the solvent A is one or more of toluene, ethanol, N,N-dimethylformamide, acetone, chloroform, dimethylformamide, ethyl acetate, methanol, and triethylamine, and the concentration of polylactic acid in the modified spinning mixture is 10-30 wt%.

[0009] Preferably, in step S1, the solvent B is one or more of lithium chloride, sodium chloride, formic acid, acetylacetone, polyvinylpyrrolidone, and polyethylene glycol, and the concentration of the solvent B in polylactic acid is 2-5 wt%.

[0010] Preferably, in step S2, the metal salts are one or more of zirconium oxychloride octahydrate (ZrOCl2·8H2O), zirconium carbide, zirconium nitrate, cerium sulfate, cerium chloride, cerium acetate, cerium hydroxide, hafnium nitrate, hafnium sulfate, and hafnium acetate, and the linker is one or more of terephthalic acid, phthalic acid, and 1,3,5-benzenetricarboxylic acid (H3BTC).

[0011] Preferably, in step S2, the mass ratio of the metal salts to the linker is 1:1 to 1:6.

[0012] Preferably, in step S2, the solvent C is one or more of formic acid, terephthalic acid, isophthalic acid, phthalic acid, mellitic acid, acetic acid, benzoic acid, propionic acid, and trifluoroacetic acid, and the solvent D is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, deionized water, N-methylpyrrolidone, dimethyl sulfoxide, and acetonitrile, and the volume ratio of the solvent C to the solvent D is 1:1 to 1:9.

[0013] Preferably, in step S3, the wet chemical synthesis method is one or more of microwave-assisted method and hydrothermal synthesis method, the synthesis reaction time is 0.5-13 h, and the temperature range is 110-165°C.

[0014] Preferably, in step S4, the spinning technology is one or more of rotary non-nozzle electrospinning method, in-situ growth spinning method, coaxial electrospinning method, and dual-jet electrospinning method.

[0015] Preferably, in step S4, for the rotary non-nozzle electrospinning method of the spinning technology, the voltage is 5-25 KV, the rotation speed is 1000-10000 rpm, and the solution bath depth is 2-6 nm; for the in-situ growth spinning method, the temperature is 60-120°C and the time is 2-24 h; for the coaxial electrospinning method, the flow rate ratio of the shell layer to the core layer is 1:1, the receiving distance is 15-30 cm, the reaction temperature is 20-30°C, and the humidity is 15-35%; for the dual-jet electrospinning method, the flow rate is 0.1-1.5 mL / h, the positive and negative voltages are 8-25 KV, and the receiving distance is 15-30 cm.

[0016] To achieve the above object, according to the second aspect of the present invention, the present invention also provides a fiber membrane obtained by the foregoing preparation method.

[0017] Preferably, the fiber membrane has a refined fiber structure, the average fiber diameter is 130 - 255 nm, the specific surface area is 389 - 441 m 2 / g, and the pore size is 1.22 - 1.86 nm.

[0018] To achieve the above object, according to the third aspect of the present invention, the present invention also provides an application of the above fiber membrane in a purification material for synergistically filtering dust and capturing CO2, with a dust filtration efficiency higher than 96.9% and a CO2 adsorption capacity higher than 1.72 mmol / g.

[0019] The MOF nanosheets prepared in the present invention are MOF-808 nanosheets prepared from metal compounds (usually Zr, Hf or Ce) and linkers. They are very attractive due to their high porosity, large specific surface area, good stability and easy functionalization. Combining them with electrospinning can obtain a multi-microporous refined low-resistance fiber membrane with a series of advantages such as a high specific surface area, low resistance loss, high gas adsorption capacity, and stable filtration efficiency, which is a purification material in synergistically filtering dust and capturing CO2 gas. Generally speaking, the fiber membrane has a refined fiber structure (the average fiber diameter is 130 - 255 nm), a large specific surface area (389 - 441 m 2 / g), a small pore size (1.22 - 1.86 nm), a high dust filtration efficiency (the filtration efficiencies of PM 0.3 and PM 2.5 are both higher than 96.9%) and a strong CO2 capture ability (the adsorption capacities are both higher than 1.72 mmol / g).

[0020] Applying the technical solution of the present invention, the beneficial effects of the multi-microporous refined low-resistance fiber membrane of the present invention are as follows: (1) Through the controllable synthesis technology realized by using the fiber membrane template, MOF modification is carried out during the spinning process, so that the strength, resistance loss and porosity of the fiber membrane are improved to a certain extent; (2) The MOF nanosheets are uniformly loaded on the polylactic acid fibers, so that the specific surface area of the polylactic acid fibers is extended and the porosity is increased, which is convenient for better filtering dust, and the overall optimization of the simple filtration function and lack of special functions of the fiber membrane is carried out. In particular, the rigid skeleton of the MOF nanosheets themselves endows it with a unique pore structure, improving the CO2 adsorption capacity of the polylactic acid nanofiber membrane; (3) After the fibers are refined, the air permeability of the fiber membrane with a refined fiber structure is greatly improved in terms of filtration, and a good filtration effect can be obtained at a lower resistance; (4) The simultaneous action of the refined fiber structure fiber membrane and MOF makes it have rich porosity, a large surface area, and a stable particle filtration efficiency (PM0.3 and PM 2.5 Both the filtration efficiency (above 96.9%) and the gas adsorption capacity (the adsorption amount of CO2 gas is above 1.72 mmol / g), along with excellent chemical stability, endow it with good development potential in the fields of industrial waste gas treatment, the development of green building materials, and the purification and emission reduction of automobile exhaust.

[0021] The polylactic acid nanofiber membrane of the present invention not only has a series of advantages such as high porosity, excellent chemical stability, high-capacity gas adsorption, and efficient soot filtration, but also is simple to operate and has diverse preparation methods. It is a purification material with a wide range of application fields and excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 is a flow chart of the preparation method of the present invention.

[0024] Figure 2 is a scanning electron microscope image of the MOF-808 nanosheets obtained in Example 1 of the present invention.

[0025] Figure 3 is a scanning electron microscope image of the multi-microporous refined low-resistance fiber membrane obtained in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other implementation manners obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. The present invention will be described in detail below with reference to the embodiments.

[0027] As Figure 1 shown, Example 1 of the present invention provides a method for preparing a multi-microporous refined low-resistance fiber membrane, including the following steps: Step S11, Preparation of modified spinning mixture: Poly(lactic acid) is fully dispersed in solvent A composed of N,N-dimethylformamide and chloroform (mass ratio 4:1) (the concentration of poly(lactic acid) in the modified spinning mixture is 10 wt%), and lithium chloride is added as solvent B (the concentration of lithium chloride in the modified spinning mixture is 2 wt%) to prepare the modified spinning mixture; Step S12, Preparation of MOF precursor solution: Zirconium oxychloride octahydrate (ZrOCl2·8H2O) is dissolved in a mixed solution composed of formic acid and deionized water (volume ratio of formic acid to deionized water 1:3), and 1,3,5-benzenetricarboxylic acid (H3BTC) is added (the mass ratio of zirconium oxychloride octahydrate to 1,3,5-benzenetricarboxylic acid is 1:1), and ultrasonic treatment is carried out to fully dissolve it to obtain the MOF precursor solution; Step S13, Preparation of MOF nanosheets: The MOF precursor solution obtained in step S12 is placed in a microwave reactor at 140 °C for 30 min for wet chemical synthesis, and after centrifugal washing and vacuum drying, MOF-808(Zr) nanosheets (average thickness 10 nm) are obtained; Step S14, Preparation of multi-microporous refined low-resistance fiber membrane: The modified spinning mixture obtained in step S11 and the MOF nanosheets obtained in step S13 are spun by a dual-spray electrospinning method (flow rate 1.5 mL / h, positive voltage +20 KV, negative voltage -10 KV, reciprocating speed 15 cm / min, receiving distance 16 cm) and dried to obtain a poly(lactic acid) fiber membrane, the specific surface area of the fiber membrane is 441 m 2 / g, average diameter 130 nm, pore size 1.22 nm.

[0028] Example 2 of the present invention provides a method for preparing a multi-microporous refined low-resistance fiber membrane, including the following steps: Step S21, Preparation of modified spinning mixture: Poly(lactic acid) is fully dispersed in solvent A composed of methane and N,N-dimethylformamide (mass ratio 7:3) (the concentration of poly(lactic acid) in the modified spinning mixture is 15 wt%), and sodium chloride is added as solvent B (the concentration of poly(lactic acid) and sodium chloride in the modified spinning mixture is 1 wt%) to prepare the modified spinning mixture; Step S22, Preparation of MOF precursor solution: Hafnium nitrate (Hf(NO3)4) is dissolved in a mixed solution of formic acid and deionized water (mass ratio of formic acid to deionized water 1:1), terephthalic acid is added as an organic ligand (chemical mass ratio of hafnium nitrate to terephthalic acid 1:1), and the solution is ultrasonically treated to fully dissolve it to obtain the MOF precursor solution; Step S23, Preparation of MOF Nanosheets: The MOF precursor solution obtained in Step S22 was placed in a microwave reactor at 140 °C for 3 h for wet chemical synthesis, followed by centrifugation, washing, and vacuum drying to obtain MOF-808(Hf) nanosheets (average thickness: 30 nm). Step S24, Preparation of Multi-Microporous Refined Low-Resistance Fibrous Membrane: The MOF nanosheets obtained in Step S23 were dispersed into the modified spinning mixture obtained in Step S21, and electrospinning was carried out using a rotary nozzleless electrospinning method (rotation speed: 5000 rpm, voltage: 30 KV, solution bath depth: 5 nm) and then dried to obtain a polylactic acid fibrous membrane. The specific surface area of the fibrous membrane was 429 m 2 / g, average diameter was 155 nm, and pore size was 1.35 nm.

[0029] Example 3 of the present invention provides a method for preparing a multi-microporous refined low-resistance fibrous membrane, comprising the following steps: Step S31, Preparation of Modified Spinning Mixture: Polylactic acid was fully dispersed in Solvent A composed of N,N-dimethylformamide and dichloromethane (mass ratio 1:2) (the concentration of polylactic acid in the modified spinning mixture was 20 wt%), and formic acid was added as Solvent B (the content of formic acid in the modified spinning mixture was 5 wt%) to prepare the modified spinning mixture. Step S32, Preparation of MOF Precursor Solution: Cerium nitrate (Ce(NO3)3·6H2O) and trimesic acid (H3BTC) were respectively dissolved in N,N-dimethylformamide, and the two were uniformly mixed (mass ratio of cerium nitrate to trimesic acid was 1:2) to obtain the MOF precursor solution. Step S33, Preparation of MOF Nanosheets: The MOF precursor solution obtained in Step S32 was placed in a microwave reactor at 120 °C for 30 min for wet chemical synthesis, followed by centrifugation, washing, and vacuum drying to obtain MOF-808(Ce) nanosheets (average thickness: 20 nm). Step S34, Preparation of Multi-Microporous Refined Low-Resistance Fibrous Membrane: The modified spinning mixture obtained in Step S31 was prepared into a fibrous membrane by spinning (receiving distance: 15 cm, voltage: 30 KV, ambient humidity: 25±5%), and it was immersed in a dispersion liquid prepared from the MOF nanosheets obtained in Step S33 and deionized water. MOF-808(Ce) nanoparticles were introduced into the nanofiber skeleton structure by in-situ growth method (temperature: 100 °C, time: 12 h). After the reaction, the obtained polylactic acid fibrous membrane was washed with ethanol as a solvent and dried. The specific surface area of the obtained fibrous membrane was 402 m 2 / g, average diameter was 178 nm, and pore size was 1.47 nm.

[0030] Example 4 of the present invention provides a method for preparing a multi-microporous refined low-resistance fiber membrane, comprising the following steps: Step S41, preparation of a modified spinning mixture: Poly(lactic acid) is fully dispersed in solvent A composed of acetone and N,N-dimethylformamide (mass ratio 1:1) (the concentration of poly(lactic acid) in the modified spinning mixture is 25 wt%), and acetylacetone is added as solvent B (the concentration of acetylacetone in the modified spinning mixture is 3 wt%) to prepare the modified spinning mixture; Step S42, preparation of a MOF precursor solution: Cerium chloride (CeCl3) and trimesic acid are respectively dissolved in an appropriate amount of dimethyl sulfoxide (DMAc), and the two are uniformly mixed (the mass ratio of cerium chloride to dimethyl sulfoxide is 1:1), and ultrasonic treatment is carried out to dissolve them fully to obtain the MOF precursor solution; Step S43, preparation of MOF nanosheets: The MOF precursor solution obtained in step S42 is placed in a hydrothermal reaction kettle, subjected to wet chemical synthesis at 160 °C for 13 h and then cooled to room temperature, and the product is centrifuged, washed and dried to obtain MOF-808(Ce) nanosheets (average thickness is 40 nm); Step S44, preparation of a multi-microporous refined low-resistance fiber membrane: The MOF nanosheets obtained in step S43 are dispersed in N,N-dimethylformamide as the shell layer solution, and the modified spinning mixture prepared in step S41 is used as the core layer solution. A fiber membrane is prepared by coaxial electrospinning technology (shell layer flow rate is 1 mL / h, core layer flow rate is 1 mL / h, receiving distance is 10 cm, temperature is 25 °C, humidity is 25 ± 5%) and dried. The specific surface area of the fiber membrane is 389 m 2 / g, average diameter is 255 nm, and pore size is 1.86 nm.

[0031] In Comparative Example 1 of the present invention, the method of Example 1 is basically adopted to prepare a multi-microporous refined low-resistance fiber. The difference is that in this example, MOF nanosheets are not used in the preparation, and an equal amount of deionized water is used instead. Specifically, poly(lactic acid) is fully dispersed in solvent A composed of N,N-dimethylformamide and chloroform (mass ratio 4:1) (the concentration of poly(lactic acid) in the modified spinning mixture is 10 wt%), and lithium chloride is added as solvent B (the concentration of lithium chloride in the modified spinning mixture is 2 wt%) to prepare the modified spinning mixture; The obtained modified spinning mixture and an equal amount of deionized water are electrospun by a double-jet electrospinning method (flow rate 1.5 mL / h, positive voltage +20 KV, negative voltage -10 KV, reciprocating speed 15 cm / min, receiving distance 16 cm) and dried to obtain a poly(lactic acid) fiber membrane. The specific surface area of the fiber membrane is 61 m 2 / g, average diameter is 397 nm, and pore size is 2.05 nm.

[0032] Comparative Example 2 of the present invention basically adopts the method of Example 1 to prepare a multi-microporous refined low-resistance fiber membrane. The difference is that in this example, the microwave-assisted method will not be used to prepare MOF nanosheets. Specifically, polylactic acid is fully dispersed in solvent A composed of N,N-dimethylformamide and chloroform (mass ratio 4:1) (the concentration of polylactic acid in the modified spinning mixture is 10 wt%), and lithium chloride is added as solvent B (the concentration of lithium chloride in the modified spinning mixture is 2 wt%) to prepare a modified spinning mixture; zirconium oxychloride octahydrate (ZrOCl2·8H2O) is dissolved in a mixed solution composed of formic acid and deionized water (volume ratio of formic acid to deionized water 1:3), and 1,3,5-benzenetricarboxylic acid (H3BTC) is added (the mass ratio of zirconium oxychloride octahydrate to 1,3,5-benzenetricarboxylic acid is 1:1), and ultrasonic treatment is carried out to make it fully dissolve to obtain a MOF precursor solution; the obtained MOF precursor solution is placed under magnetic stirring at room temperature for 30 min for wet chemical synthesis, cooled to room temperature, and centrifuged, washed and dried to obtain a MOF-808(Zr) product; the obtained modified spinning mixture and MOF nanosheets are spun by a dual-jet electrospinning method (flow rate 1.5 mL / h, positive voltage +20 KV, negative voltage -10 KV, reciprocating speed 15 cm / min, receiving distance 16 cm) and dried to obtain a polylactic acid fiber membrane, and the specific surface area of the fiber membrane is 98 m 2 / g, the average diameter is 375 nm, and the pore size is 2.55 nm.

[0033] Comparative Example 3 of the present invention basically adopts the method of Example 1 to prepare a multi-microporous refined low-resistance fiber membrane. The difference is that in this example, lithium chloride is not added as solvent B when preparing the modified spinning mixture. Specifically, polylactic acid is fully dispersed in solvent A composed of N,N-dimethylformamide and chloroform (mass ratio 4:1) (the concentration of polylactic acid in the modified spinning mixture is 10 wt%) to prepare a modified spinning mixture; zirconium oxychloride octahydrate (ZrOCl2·8H2O) is dissolved in a mixed solution composed of formic acid and deionized water (volume ratio of formic acid to deionized water 1:3), and 1,3,5-benzenetricarboxylic acid (H3BTC) is added (the mass ratio of zirconium oxychloride octahydrate to 1,3,5-benzenetricarboxylic acid is 1:1), and ultrasonic treatment is carried out to make it fully dissolve to obtain a MOF precursor solution; the obtained MOF precursor solution is placed in a microwave reaction kettle at 140 °C for 30 min for wet chemical synthesis, and centrifuged and washed, and after vacuum drying, MOF-808(Zr) nanosheets (average thickness 10 nm) are obtained; and spinning is carried out by a dual-jet electrospinning method (flow rate 1.5 mL / h, positive voltage +20 KV, negative voltage -10 KV, reciprocating speed 15 cm / min, receiving distance 16 cm) and dried to obtain a polylactic acid fiber membrane, and the specific surface area of the fiber membrane is 92 m 2 / g, with an average diameter of 473 nm and a pore size of 3.41 nm.

[0034] Structure Characterization and Performance Testing Observation by Scanning Electron Microscope: The microstructure of the multi-microporous refined low-resistance fiber membrane was observed by a field emission scanning electron microscope (model JSM-7900F, JEOL, Japan).

[0035] Filtration Performance Testing: The air filtration performance of the fiber membrane (with an area of 25 cm 2 ) was tested using a CLJ-3016 laser dust particle counter (Shenzhen Huashengchang Machinery Experiment Co., Ltd.). The gas flow rate was set at 85 L / min. Each group of filter membranes was tested at least at 3 different positions, and the results were averaged.

[0036] Carbon Dioxide Adsorption Performance Testing: CO2 adsorption was carried out using a gas sorption analyzer (ASAP 2020, Micromeritics, USA). High-purity gas CO2 (99.999%) was used for adsorption measurement, while the free space was measured with helium (99.999%). Isothermal adsorption was carried out at 273 K (ice-water bath) and 298 K (water bath).

[0037] Experimental Results: Figure 2 It shows the scanning electron microscope image of the multi-microporous refined low-resistance fiber membrane obtained by the microwave-assisted method in Example 1. The MOF-808 nanosheets with an average thickness of 10 nm have relatively uniform sizes and clear edges, and the surface is relatively smooth with good dispersibility.

[0038] Figure 3 It shows the scanning electron microscope image of the multi-microporous refined low-resistance fiber membrane obtained in Example 1. More MOF-808 is deposited on the nanofibers, which not only does not block the pores in the membrane but also provides a higher specific surface area for the nanofiber membrane, enhancing its ability to capture CO2 and filter dust. It can be clearly seen that the size of the polylactic acid fibers has been successfully refined, resulting in good air permeability.

[0039] Table 1 compares the results of the average diameter, specific surface area, porosity, filtration efficiency, and CO2 adsorption amount of the ultrafine fibers of the multi-microporous refined low-resistance fiber membranes obtained in the examples and comparative examples.

[0040] Table 1

[0041] Examples 1 to 4 show that the prepared multi-microporous refined low-resistance fiber membranes have a relatively large specific surface area (389 m 2 / g to 441 m 2 / g) and a relatively small pore size (1.22 nm to 1.86 nm), because microwave-assisted synthesis is used for its synthesis, resulting in a relatively reduced pore size and a higher porosity; in Comparative Example 1, the specific surface area is only 61 m 2 / g, because instead of using MOF-808 nanosheets to modify the fiber membrane, the polylactic acid fiber membrane was directly prepared.

[0042] The dust filtration and gas capture capabilities of the multi-microporous refined low-resistance fiber membrane are closely related to the fiber diameter, specific surface area, pore size, and MOF-808 modification. Examples 1 to 4 with finer fiber diameters, larger specific surface areas, and smaller pore sizes have soot (PM 0.3 and PM 2.5 ) filtration efficiencies all above 96.9%, and the adsorption amounts of gas (CO2) are all above 1.72 mmol / g, showing good dust filtration and gas capture capabilities. Among them, Example 1 with the finest fiber diameter, the largest specific surface area, and the smallest pore size performs best in the performance test. The filtration efficiencies of PM 0.3 and PM 2.5 reach 99.6% and 99.8% respectively, and the CO2 adsorption amount is 2.1 mmol / g, far higher than that of 2 to 4 (the CO2 adsorption amounts are all less than 2.1 mmol / g).

[0043] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims. Additionally, it should be noted that in the above specific implementation manner, the various specific technical features described can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention does not separately describe various possible combination methods. Furthermore, any arbitrary combination can be made between different implementation manners of the present invention as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a microporous, thin, low-resistance fiber membrane, characterized in that: The following steps are involved: Step S1, dissolving polylactic acid in solvent A, adding solvent B to optimize the fiber diameter, and preparing a modified spinning mixture; Step S2, dissolving metal salts and linkers in solvent C and solvent D to prepare a metal organic framework precursor solution; Step S3, preparing MOF nanosheets by a wet chemical synthesis method using the metal organic framework precursor solution obtained in step S2; Step S4, obtaining a microporous, refined, low-resistance fiber membrane by spinning the modified spinning mixture obtained in step S1 and the MOF nanosheets obtained in step S3.

2. The method for preparing a microporous, thin, low-resistance fiber membrane according to claim 1, characterized in that: In step S1, the solvent A is one or more of toluene, ethanol, N,N-dimethylformamide, acetone, chloroform, dimethylformamide, ethyl acetate, methanol, and triethylamine, and the concentration of polylactic acid in the modified spinning mixture is 10-30 wt%.

3. The method for preparing a microporous, thin, low-resistance fiber membrane according to claim 1, characterized in that: In step S1, the solvent B is one or more of lithium chloride, sodium chloride, formic acid, acetylacetone, polyvinyl pyrrolidone, and polyethylene glycol, and the concentration of the solvent B in the polylactic acid is 2-5 wt%.

4. The method for preparing a microporous, thin, low-resistance fiber membrane according to claim 1, characterized in that: In step S2, the metal salt is one or more of zirconium oxychloride octahydrate, zirconium carbide, zirconium nitrate, cerium sulfate, cerium chloride, cerium acetate, cerium hydroxide, hafnium nitrate, hafnium sulfate, and hafnium acetate, and the linking agent is one or more of terephthalic acid, phthalic acid, and 1,3,5-benzenetricarboxylic acid.

5. The method for preparing a microporous, thin, low-resistance fiber membrane according to claim 1, characterized in that: In step S2, the mass ratio of the metal salt to the linker is 1:1 to 1:

6.

6. The method for preparing a microporous, thin, low-resistance fiber membrane according to claim 1, characterized in that: In the step S2, the solvent C is one or more of formic acid, terephthalic acid, isophthalic acid, phthalic acid, trimesic acid, acetic acid, benzoic acid, propionic acid, and trifluoroacetic acid; the solvent D is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, deionized water, N-methylpyrrolidone, dimethyl sulfoxide, and acetonitrile; and the volume ratio of the solvent C to the solvent D is 1:1 to 1:

9.

7. The method for preparing a microporous, thin, low-resistance fiber membrane according to claim 1, characterized in that: The wet chemical synthesis method in step S3 is one or more of a microwave-assisted method and a hydrothermal synthesis method, the synthesis reaction time is 0.5-13 hours, and the temperature range is 110-165° C.

8. The method for preparing a microporous, thin, low-resistance fiber membrane according to claim 1, characterized in that: The spinning technology in step S4 is one or more of a rotary nozzleless electrospinning method, an in-situ spinning growth method, a coaxial electrospinning method, and a double-jet electrospinning method.

9. A fiber membrane prepared by the method for preparing a microporous, refined, low-resistance fiber membrane according to any one of claims 1 to 8.

10. Use of the fiber membrane according to claim 9 in a purification material for collaboratively filtering dust and capturing CO2 gas.

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