• • Achieved ultrahigh Cl−/SO4^2− selectivity of 125, surpassing the performance upper bound of other membranes, enabling high-purity separation in chloralkali and wastewater treatment.
• • Rigidly confined interaction within graphene oxide channels reconfigures hydration shells by rotating water molecules and altering their distance from ion center, compensating for hydration energy barriers and differentiating anion rearrangement.
• • Membrane channels combine physical rigidity with chemical affinity via charged linkers, mitigating swelling issues common in 2D membranes and maintaining sub-nanometer size exclusion.
• • The dehydration mechanism under rigid confinement yields a well-balanced ion permeability and selectivity, providing a design strategy for next-generation anion selective membranes.