Multistage S-Scheme Heterojunction-Modified Polylactic Acid Nanofiber Membrane: Enhancing Long-Term Stability and Achieving Synergistic Purification of Multiple Indoor Air Pollutants

Indoor air pollution caused by particulate matter, VOCs, and pathogenic microorganisms has become more and more serious. The use of numerous petroleum-based polymer filters also causes environmental pollution. Therefore, it is urgent to develop green, degradable, and long-term-stable indoor air filters with synergistic purification of multiple pollutants. Polylactic acid nonwovens are considered candidates for the next generation of air filters because of their green and degradable properties. Herein, we developed a multistage S-scheme heterojunction (Ag₃PO₄/MXene/Bi₂WO₆, AMB)-modified PLA electrospun nanofiber membrane (AMB/PLA ENM) using continuous electrospinning equipment. The AMB/PLA ENMs not only exhibit high-efficiency air-filtration performance but also demonstrate robust photocatalytic activity for formaldehyde, bacteria, and viruses. The filtration performance of AMB/PLA ENMs for PM_0.3 achieved 99.99%/77.21 Pa at 32 L/min. Moreover, AMB/PLA ENMs exhibit excellent visible-light-driven photocatalytic activities for gaseous formaldehyde, reaching 76.77% within 200 min, and for liquid ciprofloxacin at 82.25% within 240 min. The establishment of the built-in electric field and the increased oxygen vacancies by MXene in the AMB heterojunction significantly enhance the photocatalytic performance of AMB/PLA ENMs. It also shows a significant killing rate of 99.99% against Escherichia coli, Staphylococcus aureus, and the H1N1 virus. This synergistic purification of multiple pollutants is attributed to a dual-functional strategy that integrates multistage S-scheme heterojunction photocatalysts with a PLA electrospun nanofiber membrane to achieve highly efficient and low-pressure air filtration and long-term stable photocatalytic performance. In addition, the AMB/PLA ENMs maintain self-cleaning, good mechanical properties, and degradability, even after long-term utilization.