Biomimetic Polymer Membrane for Precise Ion Separation in Selective Electrodialysis

ABSTRACT Electric‐driven membranes featuring precise ion transport are extensively employed in energy and environmental science. Although separation performance has been significantly improved, the structural requirements for treating high‐salinity salt‐lake brines via selective electrodialysis (S‐ED) remain ambiguous. Herein, we exploit the differential reactivity of carboxyl and aldehyde groups in D‐glucuronic acid toward the abundant amino groups of polyethyleneimine. Combined with the monomer sustained‐release effect of the porous TpPa interlayer, this approach enables the construction of a biomimetic separation layer that possesses a dense surface and continuous internal Li + ‐conducting channels. These continuous pathways, rich in carboxyl moieties, enlarge the activation free‐energy barrier difference for Li + and Mg 2+ transport from 4.03 to 4.94 kJ·mol −1 . Such energetic differentiation emulates biological ion channels, wherein carboxyl groups selectively promote Li + transit while imposing a pronounced energetic penalty on heavily hydrated Mg 2+ . Consequently, the membrane exhibits cell‐membrane‐mimetic selectivity, delivering a Li + /Mg 2+ perm‐selectivity of 22.7 and a Li flux of 4.88 × 10 −8 mol·cm −2 ·s −1 , outperforming the current upper‐bound benchmark. Notably, the step‐current S‐ED process attains 78.45% Li + recovery from a simulated brine containing 106.74 g/L Mg 2+ and a Mg/Li mass ratio of 31.58. This work provides new insights into S‐ED membrane fabrication and process design for practical scalability.