Molecular encapsulation‐mediated gradient catalytic interfacial polymerization for similar ions nanofiltration

Abstract Ultra‐selective ion‐ion separation is significant but technically challenging. Achieving the accurate separation of similar ions with nanofiltration requires constructing well‐defined solute‐transferred channels and controllable membrane structures. Herein, a pioneering molecular encapsulation‐mediated gradient catalytic interfacial polymerization is proposed to synchronously control the diffusion of the monomers and polymerization reaction. The nanocapsule orderly disintegrates and releases the reactive monomers with the catalysis of HCl to participate in interfacial polymerization. The innovative strategy enhances the homogeneity of monomer diffusion and allows the polymerization reaction to proceed in stages, resulting in the formation of channels with more ordered nanostructures and more homogeneous ion transport. The membrane exhibits size‐dependent ion sieving with sub‐angstrom precision and shows high permeability (17.9 L·m −2 ·h −1 ·bar −1 ) and precise separation efficiency (>95 for Ac − and ~10% for Cl − ). The innovative method may provide a paradigm shift for the fabrication of highly uniform polyamide membranes for precise molecular sieving.