Bioinspired membrane with Angstrom‐scale channels: A versatile nanofluidic platform for efficient single‐ion sieving

Abstract Bioinspired ion‐selective transport with high precision has long been a key pursuit in artificial membrane engineering and process industries. However, developing angstrom‐scale ion channels remains a significant challenge due to the difficulty of precisely controlling the internal structure and chemical microenvironment of pore channels. Herein, we present a biomimetic membrane fabricated by sub‐nanoconfining fully crosslinked ammonium‐functionalized crown ethers (diaminobenzo‐15‐crown‐5‐ether, DAB15C5) within the pore channels of a polyamide (PA) nanofilm via surface polymerization for electromembrane desalination. The resulting DAB15C5@PA membrane exhibits a high K + permeation rate of 1.83 mol·m −2 ·h −1 under multi‐component conditions, along with excellent single‐ion selectivity, achieving mono/monovalent (K + /Li + ) and mono/divalent (K + /Mg 2+ ) ratios of 5.2 and 33.5, respectively. Theoretical operando analysis suggests that the preferential single‐ion K + extraction/separation mechanism stems from the significant disparities in transport energy barriers among ions, synergistically governed by different extents in local dehydration, enhanced size‐exclusion effects, and preferential interaction screening.