Reversible Bond Dynamics Enable Crystallinity‐Healed COF Membranes for Selective Ion Transport

ABSTRACT Covalent organic frameworks (COFs) offer ordered, nanometer‐scale channels with programmable chemistry and topology, making them promising membrane materials for selective ion transport. However, fabricating robust COF membranes that preserve high crystallinity remains a key challenge. Here we directly address this challenge by decoupling crystallization from membrane formation. COF membranes are first made by interfacial polymerization and subsequently healed under acid‐catalyzed hydrothermal conditions, which activate reversible COF linkage bond exchange and framework self‐correction. Using TpPa‐SO 3 H as a model, this healing process enhances the (100) x‐ray diffraction peak intensity by 25‐fold, resulting in a 375% increase in proton conductivity and enhanced monovalent cation‐cation selectivity. This “make‐then‐heal” strategy leverages dynamic covalent chemistry to produce structurally precise, crystallinity‐healed COF membranes.