Cation–π Reinforced Superhydrophobic PI@ZIF-67 Nanofiber Membrane for Durable High-Temperature Air Purification

Despite the pressing global threat of air pollution, MOF-polymer composites for air filtration are hindered by weak interfacial bonding, resulting in a compromised long-term performance. In this contribution, a low-temperature copolymerization and electrospinning strategy was employed, and the benzimidazole ring was introduced into the main chain of the polyimide (PI) through molecular design. By leveraging the strong cation–π interactions formed between the positively charged cobalt ions in ZIF-67 and the electron-rich π-system in the polyimide backbone, a PI@ZIF-67 composite material with robust interfacial binding properties was constructed. The PI@ZIF-67 nanofiber membrane demonstrated a filtration efficiency of 98.59% for PM0.3 (fine particulate matter with a diameter of less than 0.3 μm) with a pressure drop of 88.5 Pa at 300 °C. Compared with pure PI membrane, PI@ZIF-67 exhibited a 98.45% increase in the maximum formaldehyde adsorption capacity over 4 h, and its filtration performance only decreased by 0.3% after 9 cycles of reuse testing. Additionally, the PI@ZIF-67 nanofiber membrane achieved a water contact angle as high as 156.91°, confirming its superhydrophobic property. This work paves the way for high-performance, self-cleaning air filters by leveraging polyimide@ZIF-67 composites, expanding their use in high-temperature filtration.