Ion trap membrane with confined bind-jump strategy for high-efficiency direct lithium extraction

The rapidly growing demand for lithium in energy storage technologies necessitates more efficient lithium extraction methods from salt lakes. Direct lithium extraction (DLE) has gained attention, as it addresses more than 50% lithium losses in traditional salt-pond-based processes. However, separating lithium ion from sodium ion or potassium ion remains challenging due to their similar charge and hydration radii. To overcome this, we developed a covalent organic framework-based ion trap membrane by embedding lithiophilic diketone molecules [2-thenoyltrifluoroacetone (HTTA)] into subnanometer channels, enabling a "bind-jump" transport mechanism. HTTA sites selectively bind lithium ion, assist its partial dehydration (bind step), and promote hopping to adjacent HTTA sites (jump step). The optimized HTTA₁-1,3,5-triformylphloroglucinol-tris(4-aminophenyl)amine/polyacrylonitrile membrane exhibited high lithium ion/sodium ion selectivity (>320) and lithium ion permeance (~143 millimoles per square meter per hour) under electrodialysis, outperforming leading membranes. The membrane also showed stable performance over 10 cycles. This work demonstrates a scalable strategy combining thermodynamic and kinetic modulation for efficient lithium ion extraction from complex brines.