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

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⁺>>Mg²⁺) 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.