Researchers from the Dalian Institute of Chemical Physics have developed ultrathin polymeric membranes using an interfacial polymer cross-linking method that creates nanoscale separation layers with quasi-ordered architectures. Detailed in Nature Chemical Engineering, these membranes achieve angstrom-level precision in ion sieving, overcoming traditional selectivity and permeability trade-offs inherent to polymeric materials. By controlling polymer network cross-linking, membranes as thin as 3 micrometers maintain mechanical robustness and operational stability, enabling rapid and selective ion transport promising for modern separation technologies.