Hierarchical Assembly of Sub‐2 nm Amorphous Nanobelt Membranes for Oil–Water Separation via Pore Engineering

ABSTRACT The trade‐off between flux and selectivity in oil–water separation membrane fundamentally originates from a structural incompatibility between interconnected transport pathways and densely distributed interfacial active sites. Herein, we construct a free‐standing membrane with a plain‐weave‐inspired pore architecture through the hierarchical assembly of sub‑2 nm ultrathin amorphous cobalt‐dodecanethiolate nanobelts. This architecture integrates hydrophobic surface groups and coordinatively unsaturated Co‐S sites within a hierarchical framework, simultaneously minimizing hydraulic resistance and maximizing accessible interfacial sites to enable rapid oil transport and selective water rejection. The optimized membrane delivers an ultrahigh flux of ∼7333 L m −2 h −1 bar −1 with 99% separation efficiency for a 1% water‐in‐dichloromethane emulsions, together with excellent antifouling stability (DR t = 11.06%, FRR = 99.56%) and preserved pore and coordination structures after repeated cycling. The membrane further exhibits consistently high fluxes across diverse organic solvents, including alkanes, alkenes, ethers, ketones, and thiols, indicating broad applicability in oil‐water separation. This work demonstrates how structural disorder in low‐dimensional amorphous materials can be harnessed as a design advantage for topology‐engineered separation membranes.