Interfacial co-assembly of colloidal covalent organic frameworks and lignocellulosic nanofibers via thermally assisted pressurized molecular weaving for selective separation membranes

Covalent organic frameworks (COFs) show considerable potential in precision membrane separation. However, constructing freestanding membranes with structural integrity remains a formidable challenge due to weak interfacial interactions. Although polymer-assisted substrates solve the bottlenecks of membrane formation, they inevitably generate non-biodegradable microplastics, exacerbating environmental burdens. Inspired by the hierarchical structure of wood, we developed a thermally assisted pressurized molecular weaving strategy to construct robust LCNF@TpPa-SOH membranes via the interfacial co-assembly of solution-processable colloidal COFs and lignocellulosic nanofibers (LCNFs). This process leverages the dynamic chemistry of LCNFs, wherein in-situ lignin self-polycondensation occurs under thermal pressurization, synergistically enhancing interfacial adhesion and dynamically regulating the pore architecture. Comprehensive characterizations combined with density functional theory (DFT) calculations elucidate these distinctive interfacial interactions. Consequently, the optimized membrane achieves an exceptional antibiotic/salt separation factor of 46.86 and a high pure water permeance of 32 L·m·h·bar, outperforming most state-of-the-art membranes. Mechanically, the membrane achieves a tensile strength of 40 MPa, and this route enables scalable fabrication of large-area membranes with a maximum lateral dimension of 20 cm. The biomass-derived matrix exhibits obvious macroscopic fragmentation after 13 weeks of soil burial, greatly mitigating environmental drawbacks of conventional separation membranes. This work demonstrates a scalable interfacial co-assembly strategy for transforming solution-processable COF colloidal particles into robust, functional membranes.