Fully-biodegradable and self-powered intelligent filter assembled by fibrous cellulose and MOF-functionalized poly(lactic acid) core-shell nanofibers for active PM capturing and passive respiratory sensing.

With the increasing demand for ecofriendly air filtration materials, poly(lactic acid) (PLA) nanofibrous membranes (NFMs) show significant potential for efficient air purification while evading plastic pollution. However, there is still an urgent need to solve the issues of intrinsically low electroactivity and poor electret performance for PLA. Here, we prepared MOF-functionalized core-shell beaded PLA (MCSB-PLA) gradient nanofibers at fibrous cellulose, featuring a PLA/MOF-5 composite shell layer by coaxial electrospinning. Under the action of high-voltage electric field, MOF-5 nanocrystals were ready to interact with PLA chains, prompting the generation of highly refined and electroactive nanofibers. The MCSB-PLA NFMs were characterized by ultrafine fibers (diameter decrease of 23.5 %) and MOF-triggered bead-on-string microstructures. Meanwhile, both the surface potential and dielectric constant were largely elevated for MCSB-PLA NFMs (up to 5.2 kV and 1.86, respectively), accompanied by excellent tribo-output performance (236.8 % and 161.9 % increase in output voltage and current, respectively). Given the increased electroactivity, MCSB-PLA NFMs showed high-efficiency PM filtration (93.4 %, 106 Pa, at 32 L/min), representing an increase of 12.26 % compared to pure PLA counterpart (only 83.2 %). Even under high-humidity conditions, 91.3 % removal of PM was realized by MCSB-PLA (at 90 %RH and 32 L/min). Furthermore, the self-powered mechanisms were integrated with MCSB-PLA/cellulose, permitting real-time monitoring of physiological signals. The proposed degradable and highly electroactive MCSB-PLA NFMs is highly promising for air purification and passive healthcare.