Defect-Selective Etching Engineering of Reduced Graphene Oxide Membranes

Two-dimensional laminar membranes hold great promise for advanced water treatment but are inherently limited by a permeability-selectivity trade-off. Herein, we report a nanoscale "defect-excavation" strategy to overcome this limitation in reduced graphene oxide (rGO) membranes by engineering dual transport pathways at the molecular level. Vertical nanopores created by mild KOH etching selectively targeted defect-prone sp3-hybridized carbon domains, carving high-speed shortcuts through the laminar structure. To complement the kinetic nanoetching, we also introduced a thermodynamic stabilization step involving ionic-liquid intercalation, wherein these supramolecular rivets anchor expanded interlayer spacings through robust cation-π interactions. This synergistic integration created a dual nanoscale transport network that reshaped the transport of water molecules within confined two-dimensional nanochannels. The optimized membrane (KOH-IL-rGO membrane) exhibited an ultrahigh water permeance of 455 L m-2 h-1 bar-1 and a methylene blue rejection of 99.68%. Molecular dynamics simulations further elucidated the cooperative transport mechanism, which provided critical quantitative insights: the vertical shortcuts significantly enhanced the overall water permeance, and the expanded interlayer spacing induced directly underpins the ultrahigh permeance and selective rejection observed. Overall, this work provides a rational materials design approach for constructing high-performance, energy-efficient membranes for sustainable water purification and recovery.