An Ultrathin Membrane with Bubble‐Raft‐Inspired Single‐Layer Nanofibrous Networks for Efficient and Low‐Resistance Air Filtration

Airborne particulate matter (PM) is a major global safety concern, significantly straining the ecological environment, human health, and economy. Filtration membranes, essential for PM removal, are challenging in achieving both high efficiency and low air resistance, resulting in a high pressure drop during efficient filtration. Herein, inspired by bubble rafts, an ultrathinnanofibrous network membrane is fabricated by transforming a liquid film of polysulfonesolution on electrospun fibrous scaffold into a single-layer network via nonsolvent-induced phase separation. Tailoring of the polysulfone concentration in the liquid film supported by the scaffold and of the phase separation process induced by flowing nonsolvent allows the construction of the single-layer network with interconnected nanofibers (diameter of ≈40 nm). Benefiting from the single-layer network, the membrane exhibits a small pore size (≈270 nm) at a high porosity of 90.3% and ultrathin thickness of ≈800 nm. Consequently, the membrane shows high efficiency (99.8% removal of PM_0.3) at an ultralow pressure drop (<40 Pa). Moreover, the membrane exhibits high transparency (>83%) and allows the light breeze (wind speed of 3.2 m s^-1) to pass through easily, enabling energy-efficient applications, such as window screens. This work provides new insights into designing membranes for efficient and low-resistance filtration and separation.