Lignin-derived Si–O/carbon hybrid nanofibrous membranes with biomimetic brick-and-mortar architecture for robust oil/water separation under harsh conditions

Lignin-enabled Si–O/carbon nanofibrous membranes were developed for harsh-condition oil/water separation. • Lignin contributed to defect-rich carbon framework formation and interfacial functionality. • The optimized membrane showed foldable flexibility, underwater superoleophobicity, and > 99% separation efficiency. Lignin, an abundant aromatic biological macromolecule, is an attractive sustainable precursor for functional carbon materials, yet its structure-directing role in high-performance separation membranes remains insufficiently exploited. In this work, lignin-enabled Si–O/carbon hybrid nanofibrous membranes were fabricated by electrospinning polyacrylonitrile/lignin/tetraethyl orthosilicate (PAN/lignin/TEOS) precursor solutions, followed by controlled stabilization and carbonization. During thermal conversion, lignin contributed to the formation of defect-rich carbon domains and polar interfacial characteristics, while TEOS-derived amorphous Si O phases helped regulate framework evolution, suppress structural collapse, and buffer local stress concentration. As a result, the optimized membrane developed a biomimetic brick-and-mortar-like hybrid architecture with multiscale porosity, foldable flexibility, rapid water infiltration, and strong underwater oil repellency. The membrane exhibited underwater oil contact angles above 150°, achieved separation efficiencies above 99% for surfactant-free oil/water mixtures with a water flux of 1299.36 L·m −2 ·h −1 under gravity-driven conditions, and also efficiently separated SDS-stabilized oil-in-water emulsions. Moreover, it maintained stable performance after repeated cycling, prolonged storage, and treatment under cold, hot, acidic, and alkaline conditions. This study highlights lignin not only as a sustainable carbon source, but also as a functional macromolecular component for constructing robust hybrid nanofibrous membranes for harsh-environment oil/water separation.