Large-Scale Nanofiber Manufacturing| Robust Super-Liquid-Repellent nanofibermembranes for long-term high-efficiencyair filtration in harsh conditions

Achievement by Prof. Niu Haitao & Zhou Hua’s Team at Qingdao University: Super-Liquid-Repellent Nanofiber Membrane Enables Long-Term High-Efficiency Filtration in Harsh Conditions

Against the backdrop of rapid global economic development and accelerated industrialization, air pollution has become increasingly severe, posing serious threats to human production, daily life, and health. Air filtration, as a direct and efficient means to remove harmful particles from the air, plays a critical role in air purification. However, existing air filters face challenges, as they lose functionality and durability under extreme temperatures or harsh conditions, significantly impacting their service life. Particularly in industrial sectors such as automotive, power plants, metallurgy, and chemical engineering, exhaust emissions often contain large amounts of acidic/alkaline corrosive substances, organic solvents, and other hazardous materials, demanding higher performance from air filtration materials. Thus, developing materials with high efficiency, chemical/thermal resistance, and comprehensive filtration capabilities to address air filtration challenges in complex and harsh conditions has become urgent.

Recently, Prof. Niu Haitao and Prof. Zhou Hua’s team at Qingdao University published their latest research titled "Robust Super-Liquid-Repellent Nanofiber Membranes for Long-Term High-Efficiency Air Filtration in Harsh Conditions" in the internationally renowned journal Separation and Purification Technology. Utilizing electrospinning, the team precisely controlled material ratios and structures to successfully prepare a fluorinated metal-organic framework@polyetherimide/polyvinylidene fluoride-hexafluoropropylene/fluorinated alkylsilane (F-MOF@PEI/PVDF-HFP/FAS) nanofiber membrane with a 3D composite structure. This membrane exhibits exceptional superhydrophobic and superoleophobic properties, outstanding resistance to corrosive liquids (e.g., organic solvents, strong acids/bases), and maintains structural stability under extreme high/low temperatures. These advantages enable the membrane to achieve high filtration efficiency for both solid and liquid aerosols, with long-term stability in practical and harsh conditions.

Figure 1: Preparation and properties of F-MOF@PEI/PVDF-HFP/FAS super-liquid-repellent nanofiber membrane.

The multifunctional and robust super-liquid-repellent composite nanofiber membrane was fabricated in one step via electrospinning by stacking PEI/PVDF-HFP nanofibers incorporated with F-MOF and FAS (Figure 1). In this innovative design, thermoplastic PEI combined with low-surface-energy PVDF-HFP endowed the composite nanofibers with superior liquid repellency, thermal stability, and physicochemical stability, ensuring efficient filtration of solid/liquid aerosols.

Figure 2: Morphology and breathability/moisture permeability of the membrane. (a–d) SEM images of PEI, PEI/PVDF-HFP, PEI/PVDF-HFP/FAS, and F-MOF@PEI/PVDF-HFP/FAS nanofibers. (e) Digital photo of multi-needle electrospun membrane. (f–i) Pore size, porosity, air permeability, and water vapor transmission rate. (j) Thermogravimetric curves of PEI and F-MOF@PEI/PVDF-HFP/FAS membranes.

As shown in Figure 2, the F-MOF@PEI/PVDF-HFP/FAS nanofibers exhibit a beaded-fiber structure with interwoven stacking. The membrane features small pore sizes, high porosity, and excellent breathability/moisture permeability. 

Figure 3: Liquid repellency. (a) WCA of PEI/PVDF-HFP membranes at different ratios. (b) Effect of FAS concentration on WCA/OCA. (c) Effect of F-MOF content on WCA/OCA. (d) WCA/OCA of different membranes. (e) Self-cleaning performance. (f) Liquid droplets on PEI vs. F-MOF@PEI/PVDF-HFP/FAS membranes. (g) Personal protective performance.

 It demonstrates superwettability, with a water contact angle (WCA) of 162° and an oil contact angle (OCA) of 145°, along with repellency to various solutions (Figure 3).

Figure 4: Chemical/thermal resistance. (a) Acid/alkali droplets on the membrane for 2 hours. (b) Membrane soaked in various solutions for 24 hours. (c) WCA/OCA after soaking. (d–g) SEM images of pristine and acid/alkali-treated membranes. (h) WCA/OCA after high/low-temperature treatment. (i–j) SEM images after high/low-temperature exposure.

Moreover, the membrane shows strong resistance to chemicals and temperature (Figure 4). After exposure to chemical reagents and high/low temperatures, it retains intact fiber structure and stable wettability.

Figure 5: Air filtration performance. (a–b) Effect of FAS/F-MOF content on filtration. (c–d) Filtration of NaCl/DEHS particles at different basis weights. (e) Filtration efficiency for different aerosol sizes. (f) Efficiency/air resistance at varying airflow rates. (g) Continuous DEHS filtration performance. (h) Filtration mechanism.

The F-MOF@PEI/PVDF-HFP/FAS membrane exhibits outstanding air filtration performance, efficiently intercepting both saline and oily aerosol particles (Figure 5). At an airflow rate of 32 L/min, its NaCl particle retention efficiency reaches 99.95% (air resistance: 152 Pa), while its DEHS particle filtration efficiency is 99.55% (air resistance: 147 Pa).

Figure 6: Stability in extreme environments. (a) Filtration efficiency/air resistance under varying humidity. (b) Impact of acid/alkali vapors vs. commercial filters. (c) Filtration performance under real-world weather for 4 weeks.

As shown in Figure 6, the membrane maintains excellent filtration performance after exposure to extreme weather, high humidity, and acid/alkali vapors, indicating broad potential for industrial filtration and personal protection in complex or hazardous environments.