MOF Nanosheet-Functionalized Poly(lactic acid) Meta-membranes for Long-Term Air Purification and Intelligent Monitoring

The wide use of conventional polymeric air filters is causing a dramatically increasing accumulation of plastic and microplastic pollution. The development of poly(lactic acid) (PLA) fibrous membranes for efficient air purification is of important significance but frequently challenged by the rapid decay of filtration performance due to the intrinsically poor electret properties of PLA. Here, we propose an electroactivity promotion methodology, involving the one-step synthesis and homogeneous incorporation of high-dielectric ZIF-8 nanosheets (ZIFNSs), to facilitate interfacial polarization and fiber refinement during electrospinning of PLA nanofibers. The preparative electrospun PLA/ZIFNS meta-membranes exhibited an unusual combination of significantly reduced nanofiber diameter (∼462 nm), enhanced surface potential (approaching 10 kV), and increased surface activity and facilitated the formation of electroactive phases. With well-controlled morphological features, the highly electroactive PLA/ZIFNS meta-membranes exhibited exceptional filtration efficiencies for PM_2.5 and PM_0.3 (99.2 and 96.0%, respectively) even at the highest airflow rate of 85 L/min, in clear contrast to that of its pure PLA counterpart (only 79.3 and 74.6%). Arising from the increased electroactivity and active contact sites, remarkable triboelectric performance and self-charging mechanisms were demonstrated for the PLA/ZIFNS meta-membranes, contributing to long-term efficient PM_0.3 filtration (97.5% for over 360 min). Moreover, as triggered by physiological activities like respiration and speaking, the electroactive PLA/ZIFNS meta-membranes enabled real-time monitoring with high sensitivity and specificity. The proposed strategy affords significant promotion of electroactivity and triboelectric performance for PLA nanofibers, which may motivate the development of ecofriendly protective membranes for respiratory healthcare and real-time monitoring.