Engineering self-assembled 2D nano-network membranes through hierarchical phase separation for efficient air filtration

Air pollution has garnered significant worldwide attention; however, the existing air filtration materials still suffer from issues related to monotonous structure and the inherent trade-off between PM rejection and air permeability. Herein, a spider web-inspired composite membrane with continuous monolayer structured 2D nano-networks tightly welded on nanofibers in the electrospun membrane scaffold is designed via a hierarchical phase separation strategy. The resultant biomimetic hierarchical-structured membranes possess the integrated features of hierarchical multiscale structures of 2D ultrafine networks composed of nanowires with a diameter of 31 nm self-assembled by nanoparticles, exceptional characteristics involving small average aperture, extremely low network thickness, high porosity and promising pore channel connectivity, combined with rich surface polar functional groups (3.02D dipole moment). Consequently, the composite membrane exhibits a high PM0.3 capture efficiency of 99.6 % and low pressure drop of 58.8 Pa, less than 0.06 % of atmosphere pressure, with outstanding long-term PM2.5 recycling filtration performance. The hierarchical phase separation–driven 2D nano-networks construction strategy, by virtue of their feasibility and tunability, holds great promise for widespread application across diverse membrane-related domains for air filtration.