An ionic liquid-metal organic framework composite material, a preparation method and application thereof

Abstract

The application discloses an ionic liquid-metal organic framework composite material and a preparation method and application thereof, and particularly relates to the technical field of air purification membrane materials. The ionic liquid-metal organic framework composite material provided by the application realizes efficient capture of particulate pollutants (PM) in air through the action of surface charges and / or polar functional groups of MOF and the strong electrostatic action of IL with high static potential. The fiber membrane loaded with the ionic liquid-metal organic framework composite material provided by the application can capture pollutants with small particle sizes in air by means of the electrostatic force of the ionic liquid-metal organic framework composite material to attract and polarize the pollutants, so that the capture efficiency of PM and other particles in air can reach more than 98%, and the performance is almost unchanged after 96 hours of use, and the ionic liquid-metal organic framework composite material has excellent long-term durability. 2.5 ​

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air purification membrane materials, in particular to an ionic liquid-metal organic framework composite material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of industrialization and various human activities, the air pollution crisis becomes increasingly serious and threatens environmental problems and public health. Particulate matter (PM) as the culprit of haze problem has a serious impact on air quality and human health. Particulate matter with an aerodynamic diameter less than or equal to 2.5 μm (PM 2.5 ) can be inhaled into the lungs of the human body, while particulate matter with an aerodynamic diameter less than 10 μm (PM 10 ) can be retained in the upper respiratory tract of the human body through respiration, causing harm to the human body. Therefore, it is urgent to develop efficient PM filtration materials.

[0003] Existing materials used to solve the problem of PM pollution include some traditional purification materials, such as commercial filtration materials (melt-blown textile cloth and activated carbon), polar polymer nanofibers (polyacrylonitrile, polyvinylpyrrolidone and nylon, etc.) and aluminum or silver plated nanowire conductive filters. However, these methods have unavoidable shortcomings, such as high cost, high energy consumption, generation of ozone, low filtration efficiency, and failure of the electret, etc. when using high-voltage ionization air.

[0004] The prior art discloses a preparation method and application of an ionic liquid-metal organic framework composite adsorbent, which uses metal organic framework (MOF) as a carrier and ionic liquid (IL) as an active component. A plurality of ionic liquids are loaded into the pores of the metal organic framework material through surface adsorption, realizing high selective separation of olefin / alkyne mixed gas. However, the material provided by the prior art can adsorb and separate ethylene / ethyne mixed gas because the ionic liquid selectively absorbs ethylene and ethyne, and the performance of the material, such as Zeta potential, is not improved. Most of the existing materials for filtering PM in the air rely on their electrostatic force to capture and filter PM, but the increase of the electrostatic force of the material will lead to an increase in the amount of captured PM, and since PM will generate opposite charges when polarized, it will in turn reduce the electrostatic force of the filtration material. It can be seen that the electrostatic force of the filtration material will be affected by the use time, and the filtration material cannot maintain a strong electrostatic force for a long time. SUMMARY

[0005] In order to solve the problem that the existing ionic liquid-metal organic framework composite material cannot maintain strong electrostatic force for a long time, the present application provides an ionic liquid-metal organic framework composite material, which embeds ionic liquid (IL) with high absolute electrostatic potential into the channel of metal organic framework (MOF), captures PM in the air through the surface polarization of MOF and the electrostatic effect of IL, and is not affected by the electrostatic force after capturing PM due to the strong electrostatic force of the material, thereby achieving long-term durability of up to 96 hours.

[0006] Another object of the present application is to provide a preparation method of the above-mentioned ionic liquid-metal organic framework composite material.

[0007] Still another object of the present application is to provide an electrospun fiber membrane.

[0008] Still another object of the present application is to provide an application of the above-mentioned electrospun fiber membrane in air purification.

[0009] The above-mentioned objects of the present application are achieved by the following technical solutions.

[0010] An ionic liquid-metal organic framework composite material, which is structured by embedding ionic liquid into metal organic framework, wherein the ionic liquid is selected from one or more of [C4MIM]Cl, [C4MIM][OAc], [C4MIM][SCN], [C4MIM][BF4], [C4MIM][NTf2], [Tba][BF4], [Bpy][BF4] and [NBmpy][BF4].

[0011] 1-Butyl-3-methylimidazolium chloride ([C4MIM]Cl), 1-Butyl-3-methylimidazolium acetate ([C4MIM][OAc]), 1-Butyl-3-methylimidazolium thiocyanate ([C4MIM][SCN]), 1-Butyl-3-methylimidazolium tetrafluoroborate ([C4MIM][BF4]), 1-Butyl-3-methylimidazolium bis-trifluoromethanesulfonimide ([C4MIM][NTf2]), tetrabutylammonium tetrafluoroborate ([Tba][BF4]), N-butylpyridinium tetrafluoroborate ([Bpy][BF4]) and N-butyl-N-methylpyrrolidinium tetrafluoroborate ([NBmpy][BF4]) are several ionic liquids, which all have asymmetric and flexible organic cationic parts with delocalized electrostatic charges, resulting in strong electrostatic interaction between anions and cations, so that the ionic liquid itself has a high absolute electrostatic potential, which also leads to stronger electrostatic force of the ionic liquid-metal organic framework composite material prepared by the present application on PM; at the same time, since the ionic liquid is embedded into the channel of MOF, it is less affected by the captured PM and can maintain the electrostatic force for a longer time.

[0012] Preferably, the ionic liquid is [C4MIM][BF4]. When the ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate, the resulting ionic liquid-metal-organic framework composite material exhibits better filtration performance for PM in the air after being loaded onto the carrier.

[0013] Preferably, the metal-organic framework in the ionic liquid-metal-organic framework composite material is arbitrarily selected from one or more of ZIF-8, ZIF-67, UiO-66-NH2, MIL-53-NH2, MIL-68-NH2, MIL-100-NH2, MIL-101-NH2, M-BDC-NH2, MIL-53-NH2, MOF-74-NH2, HKUST-1, and M-MOF-74-NH2.

[0014] Among the aforementioned MOFs, ZIF-8 and ZIF-67 possess surface charges, while UiO-66-NH2, MIL-53-NH2, MIL-68-NH2, MIL-100-NH2, MIL-101-NH2, M-BDC-NH2, MIL-53-NH2, and MOF-74-NH2 possess polar functional groups. HKUST-1 possesses open metal sites, and M-MOF-74-NH2 possesses both open metal sites and polar functional groups. Therefore, these MOFs exhibit stronger surface polarization of PM, and this surface polarization capability is also part of the electrostatic forces inherent in ionic liquid-metal-organic framework composites.

[0015] Preferably, the loading of the ionic liquid in the ionic liquid-metal-organic framework composite material is 5 to 30 wt%.

[0016] When the loading of IL is less than 5 wt%, the electrostatic interaction strength of the ionic liquid-metal-organic framework composite material is insufficient; when the loading of IL is greater than 30 wt%, since the ionic liquid-metal-organic framework composite material needs to be loaded onto the carrier through electrospinning process to function in this invention, and the electrostatic interaction of the material is too strong when the loading of IL is too high, more time, effort and cost are required during electrospinning. Therefore, this invention preferably uses an IL loading of less than 30 wt% in the ionic liquid-metal-organic framework composite material.

[0017] More preferably, the loading of the ionic liquid in the ionic liquid-metal-organic framework composite material is 10 to 25 wt%.

[0018] The present invention also protects the preparation method of the above-mentioned ionic liquid-metal-organic framework composite material, which specifically includes the following steps: adding the metal-organic framework into the ionic liquid solution and fully impregnating it to obtain the ionic liquid-metal-organic framework composite material.

[0019] The present invention also protects an electrospun fiber membrane on which the above-mentioned ionic liquid-metal-organic framework composite material is loaded.

[0020] The main mechanisms by which the aforementioned electrospun fiber membranes exhibit high PM filtration performance include inertial impaction, Brownian diffusion, direct interception, gravitational settling, and electrostatic forces. Firstly, inertial impaction and Brownian diffusion are relatively conventional removal principles in existing technologies. When PM moves within the electrospun fiber membrane, a higher Stokes number and Peckley number result in stronger inertial impaction and Brownian diffusion between the PM and the fiber membrane. Fibers loaded with ionic liquid-metal-organic framework composites have larger diameters than unloaded fibers, thus enhancing inertial impaction and Brownian diffusion as PM passes through the membrane. Simultaneously, the increased fiber diameter provides more and finer inter-apertures, capturing PM through direct interception and thereby improving overall filtration efficiency. Furthermore, the prepared electrospun fiber membrane material exhibits high surface energy, large specific surface area, and strong adsorption capacity. This is due to the rough surface and porous structure of micropores and mesopores formed on the fiber surface after loading with MOF, which possesses excellent PM removal potential.

[0021] More importantly, the electrospun fiber membrane provided by this invention has strong electrostatic force. This is because PM contains various ions and some highly polar functional groups (such as SO42-). 2- NO3 - NH4 + Cl - MOFs (electromagnetic materials containing CO, C=O, CN) and carrying surface charges and / or polar functional groups can polarize the PM surface. Simultaneously, ILs (inductively coupled plasmas) possess high absolute electrostatic potentials, which improve the electrostatic interaction between PM and the electrospun fiber membrane, thus significantly enhancing the PM filtration and removal performance of the fiber membrane and maintaining this PM filtration performance over a long period. Zeta potential tests confirmed that the introduction of ILs does indeed increase the charge on the fibers, thereby increasing the electrostatic force between the fibers and PM particles. This electrostatic force, acting as a driving force, improves the PM removal efficiency.

[0022] In summary, large particulate pollutants in the air that cannot pass through the tiny interlacing spaces between fibers are easily blocked by direct interception, inertial impaction, and Brownian diffusion mechanisms when passing through the fiber membrane. Meanwhile, PM2.5... 2.5 PM 0.3-0.5Smaller particles can be captured by the strong adsorption capacity and electrostatic forces of fibrous membrane materials. In addition to the contribution of MOF, IL plays a crucial role in the excellent PM filtration efficiency. It can provide sufficient charge to increase electrostatic force, thereby achieving efficient PM capture.

[0023] Preferably, the loading of the ionic liquid-metal-organic framework composite material on the electrospun fiber membrane is 2 to 50 wt%.

[0024] When the loading of the ionic liquid-metal-organic framework composite material is less than 2 wt%, the electrostatic force of the electrospun composite fiber membrane is insufficient; when the loading of the ionic liquid-metal-organic framework composite material is greater than 50 wt%, electrospinning requires more time and cost due to the high loading. Therefore, the present invention preferably uses a loading of less than 50 wt% of the ionic liquid-metal-organic framework composite material on the electrospun fiber membrane.

[0025] More preferably, the loading of the ionic liquid-metal-organic framework composite material on the electrospun fiber membrane is 5 to 20 wt%.

[0026] In a specific embodiment of the present invention, the preparation method of the above-mentioned fiber membrane may specifically include the following steps: thoroughly mixing ionic liquid-metal-organic framework composite material, PAN and organic solvent, and preparing the fiber membrane by electrospinning process.

[0027] In a specific embodiment of the present invention, the specific steps for preparing a fiber membrane by electrospinning are as follows: thoroughly mix ionic liquid-metal-organic framework composite material, polyacrylonitrile (PAN) and N,N-dimethylformamide to obtain an electrospinning solution, and then perform electrospinning.

[0028] In a specific embodiment of the present invention, the voltage applied in the electrospinning process is 9–25 kV; the spinning solution flow rate is 0.4–1.2 mL / h; the distance between the spinning metal needle tip and the receiving shaft is 12–22 cm; during electrospinning, the nonwoven fabric can be wrapped around the metal receiving shaft; the ambient temperature is maintained at 25 ± 3 °C; and the humidity is maintained at 50 ± 5%.

[0029] The present invention also protects the application of the above-mentioned fiber membrane in air purification.

[0030] Preferably, the air purified by the electrospun fiber membrane contains PM2.5. 0.5-1.0 PM 0.3-0.5 PM 2.5 and PM 10 Four types of particulate pollutants.

[0031] When the purified air contains the above four particulate pollutants, the excellent air purification performance of the electrospun fiber membrane provided by the present invention can be more fully demonstrated.

[0032] More preferably, in the air purified by the aforementioned fiber membrane, PM 2.5 Index >500 μg·m -3 PM 10 Index >900 μg·m -3 .

[0033] According to current Chinese standards, PM2.5 in the air... 2.5 The index has a 24-hour average concentration of less than 75 μg·m -3 To meet the standard, it must be greater than 500 μg·m -3 PM 2.5 The index indicates severe air pollution. Meanwhile, the national monitoring of inhalable particulate matter (PM2.5)... 10 The set standard value is a 24-hour average concentration of less than 150 μg·m³. -3 Therefore, when PM in the air 2.5 Index and PM 10 The indices are greater than 500 μg·m -3 and 900 μg·m -3 At this time, it means that the air quality is extremely poor, and the fiber membrane provided by this invention has the highest practicality.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The ionic liquid-metal-organic framework composite material provided by this invention achieves efficient capture of PM in the air through the surface charge and / or polar functional groups of the MOF, and the strong electrostatic effect of the IL with high electrostatic potential. The fiber membrane loaded with the ionic liquid-metal-organic framework composite material provided by this invention effectively captures PM. 10 Its filtration efficiency can reach 98.49±0.51%, which is effective for PM2.5. 2.5 Its filtration efficiency can reach 98.37±0.36%, which is effective for PM2.5. 0.5-1.0 and PM 0.3-0.5 The filtration efficiency can reach over 94%, and more importantly, the fiber membrane prepared by this invention has a high filtration efficiency for PM2.5. 2.5 Its filtration efficiency decreased by only 0.40% after 96 hours of use, demonstrating excellent long-term durability. Attached Figure Description

[0036] Figure 1 The chemical structural formula of the ionic liquid selected in this invention is shown below.

[0037] Figure 2The infrared spectra of the ionic liquid-metal-organic framework composite materials prepared in Examples 4 and 9-10 of this invention are shown.

[0038] Figure 3 This is a scanning electron microscope image of the fiber membrane loaded with the ionic liquid-metal-organic framework composite material obtained in Example 4 of the present invention.

[0039] Figure 4 This is a scanning electron microscope image of a pure PAN fiber membrane material.

[0040] Figure 5 The nitrogen isotherm adsorption-desorption curve is shown for the fiber membrane loaded with the ionic liquid-metal-organic framework composite material obtained in Example 4 of this invention.

[0041] Figure 6 The pore size distribution curve is shown for the fiber membrane loaded with the ionic liquid-metal-organic framework composite material obtained in Example 4 of this invention.

[0042] Figure 7 To compare the effects of fiber membranes loaded with ionic liquid-metal-organic framework composite materials obtained in Examples 4 and 9-10 of this invention on PM2.5, and fiber membranes loaded only with MOF materials, this invention is a better fit for PM2.5. 10 and PM 2.5 Filtering performance and Zeta potential.

[0043] Figure 8 The PM filtration performance test diagram and Zeta potential of the fiber membranes loaded with the series of ionic liquid-metal-organic framework composite materials provided in Examples 1 to 8 of this invention are shown.

[0044] Figure 9 This is a long-range test graph showing the PM filtration performance of the fiber membrane loaded with the ionic liquid-metal-organic framework composite material obtained in Example 4 of the present invention. Detailed Implementation

[0045] The following are specific embodiments of the present invention to further illustrate the invention in detail. However, these embodiments do not limit the invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally available commercially available raw materials and reagents.

[0046] Example 1

[0047] An ionic liquid-metal-organic framework composite material, wherein the ionic liquid is embedded in the metal-organic framework, and the ionic liquid is [C4MIM]Cl with a loading of 20 wt%.

[0048] The preparation method of the ionic liquid-metal-organic framework composite material provided in Example 1 above specifically includes the following steps:

[0049] 200 mg of metal-organic framework ZIF-8 was added to 5 mL of acetone solution of [C4MIM]Cl, where the concentration of [C4MIM]Cl was 8 mg / mL; the mixture was sealed and stirred for 8 hours to ensure thorough impregnation, and then the solvent was evaporated and dried to obtain the ionic liquid-metal-organic framework composite material.

[0050] Example 2

[0051] An ionic liquid-metal-organic framework composite material, which differs from Example 1 in that:

[0052] The ionic liquid is [C4MIM][OAc].

[0053] The ionic liquid-metal-organic framework composite material provided in Example 2 differs from that in Example 1 in its preparation method:

[0054] The ionic liquid used is [C4MIM][OAc].

[0055] Example 3

[0056] An ionic liquid-metal-organic framework composite material, which differs from Example 1 in that:

[0057] The ionic liquid is [C4MIM][SCN].

[0058] The ionic liquid-metal-organic framework composite material provided in Example 3 differs from that in Example 1 in that:

[0059] The ionic liquid used is [C4MIM][SCN].

[0060] Example 4

[0061] An ionic liquid-metal-organic framework composite material, which differs from Example 1 in that:

[0062] The ionic liquid is [C4MIM][BF4].

[0063] The ionic liquid-metal-organic framework composite material provided in Example 4 differs from that in Example 1 in its preparation method:

[0064] The ionic liquid used is [C4MIM][BF4].

[0065] Example 5

[0066] An ionic liquid-metal-organic framework composite material, which differs from Example 1 in that:

[0067] The ionic liquid is [C4MIM][NTf2].

[0068] The ionic liquid-metal-organic framework composite material provided in Example 5 differs from that in Example 1 in that:

[0069] The ionic liquid used is [C4MIM][NTf2].

[0070] Example 6

[0071] An ionic liquid-metal-organic framework composite material, which differs from Example 1 in that:

[0072] The ionic liquid is [Tba][BF4].

[0073] The ionic liquid-metal-organic framework composite material provided in Example 6 differs from that in Example 1 in that:

[0074] The ionic liquid used is [Tba][BF4].

[0075] Example 7

[0076] An ionic liquid-metal-organic framework composite material, which differs from Example 1 in that:

[0077] The ionic liquid is [Bpy][BF4].

[0078] The ionic liquid-metal-organic framework composite material provided in Example 7 differs from that in Example 1 in that:

[0079] The ionic liquid used is [Bpy][BF4].

[0080] Example 8

[0081] An ionic liquid-metal-organic framework composite material, which differs from Example 1 in that:

[0082] The ionic liquid is [NBmpy][BF4].

[0083] The ionic liquid-metal-organic framework composite material provided in Example 8 differs from that in Example 1 in that:

[0084] The ionic liquid used was [NBmpy][BF4].

[0085] Example 9

[0086] An ionic liquid-metal-organic framework composite material, which differs from Example 3 in that the ionic liquid loading is 30 wt%.

[0087] The ionic liquid-metal-organic framework composite material provided in Example 9 differs from that in Example 4 in that:

[0088] 200 mg of metal-organic framework ZIF-8 was added to 5 mL of acetone solution of [C4MIM][BF4], where the concentration of [C4MIM][BF4] was 12 mg / mL.

[0089] Example 10

[0090] An ionic liquid-metal-organic framework composite material, which differs from Example 3 in that the ionic liquid loading is 10 wt%.

[0091] The ionic liquid-metal-organic framework composite material provided in Example 10 differs from that in Example 4 in its preparation method:

[0092] 200 mg of the metal-organic framework ZIF-8 was added to 5 mL of acetone solution of [C4MIM][BF4], where the concentration of [C4MIM][BF4] was 4 mg / mL.

[0093] Example 11

[0094] A fiber membrane on which the ionic liquid-metal-organic framework composite material prepared in Example 4 is loaded at a loading of 10 wt%.

[0095] The fiber membrane provided in Example 11 above is prepared by the following steps:

[0096] 0.03 g of ionic liquid-metal-organic framework composite material, 0.27 g of polyacrylonitrile (PAN), and 4.23 g of N,N-dimethylformamide were thoroughly mixed to obtain an electrospinning solution. A 10 wt% ionic liquid-metal-organic framework composite fiber membrane was prepared by electrospinning. An 18 kV voltage was applied during electrospinning; the flow rate of the spinning solution was 1.0 mL / h; and the distance between the spinning metal needle tip and the receiving shaft was 20 cm.

[0097] Example 12

[0098] A fiber membrane, wherein the difference from Example 11 is that the loading of the ionic liquid-metal-organic framework composite material on the fiber membrane is 2 wt%.

[0099] The fiber membrane provided in Example 12 differs from that in Example 11 in that:

[0100] The amount of ionic liquid-metal-organic framework composite material added was 0.0055g.

[0101] Example 13

[0102] A fiber membrane, wherein the difference from Example 11 is that the loading of the ionic liquid-metal-organic framework composite material on the fiber membrane is 50 wt%.

[0103] The fiber membrane provided in Example 13 differs from that in Example 11 in that:

[0104] The amount of ionic liquid-metal-organic framework composite material added was 0.27g.

[0105] Example 14

[0106] A fiber membrane, wherein the difference from Example 11 is that the loading of the ionic liquid-metal-organic framework composite material on the fiber membrane is 5 wt%.

[0107] The fiber membrane provided in Example 14 differs from that in Example 11 in that:

[0108] The amount of ionic liquid-metal-organic framework composite material added was 0.0142 g.

[0109] Example 15

[0110] A fiber membrane, wherein the difference from Example 11 is that the loading of the ionic liquid-metal-organic framework composite material on the fiber membrane is 20 wt%.

[0111] The fiber membrane provided in Example 15 differs from that in Example 11 in that:

[0112] The amount of ionic liquid-metal-organic framework composite material added was 0.0675g.

[0113] Comparative Example 1

[0114] An ionic liquid-metal-organic framework composite material, which differs from Example 1 in that:

[0115] The ionic liquid is [Tma]Cl.

[0116] The ionic liquid-metal-organic framework composite material provided in Comparative Example 1 differs from that in Example 1 in that:

[0117] The ionic liquid used was [Tma]Cl.

[0118] Performance testing

[0119] Fiber membrane preparation: 0.03g of the ionic liquid-metal-organic framework composite material provided in Examples 1-10 and Comparative Example 1, 0.27g of polyacrylonitrile (PAN), and 4.23g of N,N-dimethylformamide were thoroughly mixed to obtain an electrospinning solution. A fiber membrane with an ionic liquid-metal-organic framework composite material loading of 10wt% was prepared by electrospinning. An 18kV voltage was applied during electrospinning; the flow rate of the spinning solution was 1.0mL / h; and the distance between the spinning metal needle tip and the receiving shaft was 20cm.

[0120] PM filtration performance test: The fiber membranes loaded with ionic liquid-metal-organic framework composite materials obtained in Examples 1-10 and Comparative Example 1, along with the fiber membranes provided in Examples 11-15, were placed in a cavity channel simulating PM harmful pollution for testing. PM ​​was generated by burning incense. 0.5-1.0 PM 0.3-0.5 PM 2.5 and PM 10 Four types of PM particulate matter, among which PM is guaranteed 2.5 Index >500 μg·m -3 and PM 10 Index >900 μg·m -3 Different composite fiber membrane materials with a diameter of 5 cm were sandwiched between two flanges on the simulated pipeline. The front end was connected to a cavity simulating PM harmful pollution, and an electric fan was placed there to help airflow through, with the airflow velocity set to 1.0 m / s. The rear end was connected to a cavity to collect the filtered gas. Two PM detectors (PurpleAir PA-II-SD Air Quality) were placed in the front and rear cavities to detect PM mass concentration. A digital differential pressure gauge (SMART SENSOR AS8510) was used to test the pressure drop between the two flanges on the simulated pipeline.

[0121] PM filtration performance long-term test: The fibrous membrane prepared by the ionic liquid-metal-organic framework composite material provided in Example 4 was used for testing. The test operation was similar to the PM filtration performance test above, except that the PM detector reading was read every 4 hours to calculate the PM filtration performance. The long-term test lasted for 4 days (96 hours).

[0122] Zeta potential test: The ionic liquid-metal-organic framework composite materials obtained in Examples 1-10 and Comparative Example 1 were diluted with ethanol and prepared into samples, which were then placed in a Zeta potential tester for testing.

[0123] The performance test results are as follows: Figures 1-9 As shown in Table 1:

[0124] Table 1. Performance test data of Examples 1-15 and Comparative Example 1

[0125]

[0126]

[0127] As can be seen from the data in Examples 1-8 and Comparative Example 1 in Table 1, the ionic liquid-metal-organic framework composite materials provided by this invention all exhibit high Zeta potentials. This is because the ionic liquids used in this invention all have higher absolute electrostatic potentials. The ionic liquid-metal-organic framework composite material constructed using [Tma]Cl, which has a lower absolute electrostatic potential, has a Zeta potential of only 18.54 mV. When the Zeta potential reaches 38 mV or higher, the ionic liquid-metal-organic framework composite material provided by this invention, after being loaded onto a fiber membrane carrier, exhibits better performance against PM2.5. 2.5 The filtration efficiency can reach over 97%, and it is effective against PM2.5. 10 The filtration efficiency of the fiber membrane can generally reach over 98%; among them, when the ionic liquid is [C4MIM][BF4], the filtration efficiency of the fiber membrane for PM2.5 is […]. 2.5 and PM 10 The filtration efficiency is higher. Meanwhile, the fiber membrane obtained by electrospinning the ionic liquid-metal-organic framework composite material provided in Comparative Example 1 has a higher filtration efficiency for PM2.5. 2.5 and PM 10 Its filtration efficiency is only about 90%.

[0128] As can be seen from the data in Examples 4, 9-10, when the loading of the ionic liquid in the ionic liquid-metal-organic framework composite material is higher, the resulting material has a higher Zeta potential, and the resulting fiber membrane also has better filtration performance. However, when the loading of the ionic liquid is higher than 30 wt%, the cost of electrospinning is too high, and the improvement in Zeta potential is not significant. Therefore, the preferred ionic liquid loading of this invention is 5-30 wt%, more preferably 10-25 wt%.

[0129] As can be seen from the data in Examples 11-15, when the loading of the ionic liquid-metal-organic framework composite material on the fiber membrane obtained by the electrospinning process of the present invention is increased from 2 wt% to 50 wt%, the fiber membrane exhibits better performance against PM2.5. 2.5 and PM 10 The filtration efficiency is constantly improving, but the improvement in filtration efficiency is not significant when the loading increases from 10 wt% to 50 wt%. Moreover, the cost of preparing fiber membranes by electrospinning is getting higher and higher. Therefore, the preferred loading of ionic liquid-metal-organic framework composite material on the fiber membrane is 2 to 50 wt%, more preferably 5 to 20 wt%.

[0130] Figure 1 The chemical structural formulas of the ILs selected in Examples 1 to 8 of this invention are shown.

[0131] Figure 2 The images show the infrared spectra of the ionic liquid-metal-organic framework composite materials prepared in Examples 4 and 9-10 of this invention. By comparing the characteristic vibrational absorptions in the infrared spectra of pure ZIF-8 and [C4MIM][BF4], it can be seen that the ionic liquid-metal-organic framework composite materials were successfully synthesized in this invention.

[0132] Figure 3 and Figure 4 These are scanning electron microscope images of the fiber membrane loaded with the ionic liquid-metal-organic framework composite material obtained in Example 4 of this invention and the pure PAN fiber membrane material, respectively. Figure 3 and Figure 4 The comparison shows that fibers loaded with ionic liquid-metal-organic framework composites have a larger diameter than unloaded fibers. Therefore, when airborne PM passes through the fiber membrane, inertial impaction and Brownian diffusion are enhanced. Simultaneously, the increased fiber diameter provides more and finer inter-apertures, capturing PM through direct interception, thus improving overall filtration efficiency.

[0133] Figure 5 The nitrogen isotherm adsorption-desorption curves are shown for the fiber membrane loaded with the ionic liquid-metal-organic framework composite material obtained in Example 4 of this invention. Figure 6 The pore size distribution curve is shown for the fiber membrane loaded with the ionic liquid-metal-organic framework composite material obtained in Example 4 of this invention. Figure 5 and Figure 6 The results demonstrate that the ionic liquid-metal-organic framework composite fiber membrane obtained in Example 4 has a high specific surface area and a hierarchical pore structure with both micropores and mesopores, resulting in strong adsorption capacity and excellent PM filtration potential.

[0134] Figure 7 To compare the effects of fiber membranes loaded with ionic liquid-metal-organic framework composite materials obtained in Examples 4 and 9-10 of this invention, pure PAN membranes, and PAN membranes loaded only with MOF materials on PM2.5. 10 and PM 2.5The filtration performance and Zeta potential of the prepared fiber membrane materials with different ionic liquid loadings (0.2 in [C4MIM][BF4]@ZIF-8-0.2 / PAN indicates a loading of 20 wt% ionic liquid, and similarly, 0.3 in [C4MIM][BF4]@ZIF-8-0.3 / PAN indicates a loading of 30 wt%) all showed superior PM filtration performance compared to pure PAN fiber membrane materials and ZIF-8 / PAN fiber membranes loaded only with MOF. Furthermore, the filtration performance increased with increasing IL loading, demonstrating that IL embedding enhances the Zeta potential of the ionic liquid-metal-organic framework composite material, thereby improving PM filtration performance. Specifically, the [C4MIM][BF4]@ZIF-8-0.2 / PAN fiber membrane prepared in Example 4 showed superior PM filtration performance. 10 Its filtration efficiency is 98.49%, effective against PM2.5. 2.5 Its filtration efficiency is 98.37%.

[0135] Figure 8 The graphs show the PM filtration performance test results and Zeta potential of the fiber membranes loaded with the series of ionic liquid-metal-organic framework composite materials provided in Examples 1-8 of this invention. It can be seen that the prepared series of ionic liquid-metal-organic framework composite fiber membranes effectively remove PM... 10 and PM 2.5 The filtration efficiencies of all samples were above 97.4%, and the Zeta potentials were higher than those of ZIF-8 / PAN fiber membrane materials, proving that the embedding of IL significantly improved the electrostatic force of the fiber membrane, thereby improving the PM filtration performance.

[0136] Figure 9 This is a long-range test graph showing the PM filtration performance of the fiber membrane loaded with the ionic liquid-metal-organic framework composite material obtained in Example 4 of this invention. It can be seen that after 96 hours, the two-layer [C4MIM][BF4]@ZIF-8-0.2 / PAN fiber membrane prepared in Example 4 still maintains good PM filtration performance, effectively removing PM... 2.5 The filtration efficiency was 98.60%, compared to the initial stage, PM 2.5 The filtration efficiency decreased by only 0.40%. Among them, the filtered PM particles were adsorbed and attached to the fiber membrane by strong electrostatic force, causing the fiber membrane to turn yellowish-brown. The color deepened with the increase of long-distance filtration time, indicating that the intercepted PM accumulated on the fiber membrane.

[0137] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. An electrospun fiber membrane, characterized in that, The electrospun fiber membrane is loaded with an ionic liquid-metal-organic framework composite material. The structure of the ionic liquid-metal-organic framework composite material is that the ionic liquid is embedded in the metal-organic framework. The ionic liquid is arbitrarily selected from one or more of [C4MIM]Cl, [C4MIM][OAc], [C4MIM][SCN], [C4MIM][BF4], [C4MIM][NTf2], [Tba][BF4], [Bpy][BF4], and [NBmpy][BF4].

2. The electrospun fiber membrane as described in claim 1, characterized in that, The ionic liquid is [C4MIM][BF4].

3. The electrospun fiber membrane as described in claim 1, characterized in that, The loading of ionic liquid in the ionic liquid-metal-organic framework composite material is 5~30wt%.

4. The electrospun fiber membrane as described in claim 3, characterized in that, The loading of ionic liquid in the ionic liquid-metal-organic framework composite material is 10~25wt%.

5. The electrospun fiber membrane according to any one of claims 1 to 4, characterized in that, The preparation method of the ionic liquid-metal-organic framework composite material specifically includes the following steps: adding the metal-organic framework into the ionic liquid solution and fully impregnating it to obtain the ionic liquid-metal-organic framework composite material.

6. The electrospun fiber membrane as described in claim 5, characterized in that, The loading of the ionic liquid-metal-organic framework composite material on the electrospun fiber membrane is 2~50wt%.

7. The electrospun fiber membrane as described in claim 6, characterized in that, The loading of the ionic liquid-metal-organic framework composite material on the electrospun fiber membrane is 5~20wt%.

8. The application of the electrospun fiber membrane as described in any one of claims 1 to 7 in air purification.

9. The application of the electrospun fiber membrane as described in claim 8 in air purification, characterized in that, The air purified by the electrospun fiber membrane contains PM2.

5. 0.5-1.0 PM 0.3-0.5 PM 2.5 and PM 10 Four types of particulate pollutants.

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