Bioinspired Channel Functionalization via Covalent Grafting of Crown Ethers for Selective Ion Sieving

ABSTRACT The ultrahigh ion selectivity of biological ion channels inspires the design of high‐efficiency ion separation materials. Mimicking bionic structural and functional precision in synthetic polymer membranes remains challenging. Herein, we propose a bioinspired design strategy to construct selective structures within ion channels for high‐performance monovalent selective cation exchange membranes (MSCEMs). Using the polymer as a matrix and crown ethers as functional monomers to form a synergistic transport channel composed of a “membrane matrix‐crown ether recognition site” transport architecture. Sulfonic acid groups serve as ion hopping sites to sustain high ion flux, while embedded crown ethers provide size‐matched and coordination‐selective ion recognition. The optimal membrane exhibits selective ion transport in mixed salt systems (K + >Na + >Li + >>Mg 2+ ) with excellent long‐term stability and scalability. The membranes were scaled up and integrated into an electrodialysis stack, enabling lithium extraction from simulated salt‐lake brines. This strategy establishes an internal channel functionalization paradigm for polymer membranes, providing a rational route toward advanced ion separation materials.