An Electrochemically Redox-Responsive Ion-Imprinted Permeable Membrane for Controllable Separation of Monovalent Ions

Membranes offering high ion permeability with exceptional selectivity are crucial for applications ranging from sustainable water treatment to resource extraction. Inspired by "artificially constructed molecular locks" (ion imprinting) and the voltage-gated behavior of biological ion channels, we combine a carbon nanotube (CNT) conductive network with a Prussian blue (PB) ion-imprinted lattice to fabricate an electrochemically gated ion-selective membrane. Meanwhile, the anchoring of specific cations in the crystal lattice allowed for the precise tuning of subnanometer transport channel sizes. The combined action of ion-imprinted channels and redox gating enables the PB membrane to achieve an ultrahigh K⁺/Li⁺ selectivity of 481.2, far exceeding the performance (1.5-40) of previously reported electro-responsive membranes. Electrochemical characterization and DFT simulations show that applying a redox potential accelerates diffusion, improves lattice conductivity, and weakens the ion-imprinting bias. Under voltage control, the membrane preferentially transports K⁺, significantly increasing K⁺/Li⁺ selectivity. This work provides fundamental insights into redox-regulated transport in crystalline lattices and proposes an approach for designing next-generation ion-imprinted separation membranes with voltage-sensitive ultrahigh selectivity.