Fig. 1: Design concept of membrane material and process.

a Biological ion channels achieve precise ion selectivity through noncovalent interactions, regulated by the electric potential difference across cell membranes (red: positive potential; blue: negative potential). b Schematic of a 3D COF membrane with subnanometer pores and zwitterionic-like charge distributions (red: positive potential; blue: negative potential). This architecture strengthens valence-dependent short-range interactions and integrates redox pairs, enabling conversion of the salinity gradient into an electric field to drive autonomous ion transport without external energy input.