Fabrication of high-performance nanofiltration membranes with biomimetic cell membrane architecture for magnesium-lithium separation

Lithium is a strategic critical metal underpinning the global low-carbon transition and new energy industry upgrading. China's salt lake brines generally feature low lithium grades and extremely high Mg/Li mass ratios, creating a core technical bottleneck for efficient lithium recovery. Herein, we design and synthesize bis(4-aminophenyl) phosphate (DAHP) as a functional comonomer, inspired by the ion transport mechanism of phospholipid cell membranes. Phosphate-functionalized polyamide NF membranes (denoted DPA) are subsequently fabricated via interfacial polymerization. Characterizations confirm that DAHP is covalently integrated into the polyamide network, simultaneously elevating surface negative charge density and selective layer crosslinking, narrowing pore size distribution, and optimizing pore channel structure. The DPA membrane achieves a MgCl 2 rejection of 97.6% and a Mg 2+ /Li + separation factor as high as 164 in a mixed system with a Mg/Li mass ratio of 100. The phosphate groups exert a synergistic effect of electrostatic Li + enrichment and coordination-mediated dehydration, significantly lowering the transmembrane energy barrier of Li + and facilitating its preferential transport. This work provides a novel biomimetic design strategy for developing high-performance NF membranes for lithium extraction from high-Mg/Li salt lake brines.