In-situ growth of biomimetic ion-selective membranes via confined molecular encapsulation for superior fluoride/chloride separation

Biomimetic ion channels demonstrate potential for nanoscale molecular separations by leveraging their unique confined recognition capabilities. Metal-organic framework (MOF)-based mixed matrix membranes (MMMs) offer a promising platform that integrates the ångström-scale pores of MOFs with polymer processability. However, slow MOF nucleation kinetics and weak interfacial interactions impede precise channel formation. Here, we present a confined molecular encapsulation (CME) strategy that synchronously regulates MOF nucleation kinetics and interfacial interactions, transforming precursors into flexible gel-network metal-organic gels (MOGs) via supramolecular assembly. Molecular dynamics simulations and in-situ optical detection show that stronger MOG-polymer interactions and confined diffusion govern enhanced interfacial compatibility and uniform dispersion. Optimized MMMs deliver a F⁻/Cl⁻ separation ratio of 32.0 with ionic current rectification. COMSOL simulations demonstrate that synergistic coupling of aligned MOF arrays and uniform surface charge enables efficient ion differentiation. This CME strategy establishes a versatile nanoscale platform for fabricating high-performance monovalent ion-selective membranes and nanofluidic devices. A “confined molecular encapsulation” strategy enables one-step fabrication of biomimetic ion-selective membranes. The in-situ formed MOFs with tunable sizes facilitate highly precise ion differentiation.