Endowing g‐C3N4 Membranes with Superior Permeability and Stability by Using Acid Spacers

g‐C₃N₄ membranes were modulated by intercalating molecules with SO₃H and benzene moieties between layers. The intercalation molecules break up the tightly stacking structure of g‐C₃N₄ laminates successfully and accordingly the modified g‐C₃N₄ membranes give rise to two orders magnitude higher water permeances without sacrificing the separation efficiency. The sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO)/g‐C₃N₄ with a thickness of 350 nm presents an exceptionally high water permeance of 8867 L h^?1 m^?2 bar^?1 and 100 % rejection towards methyl blue, while the original g‐C₃N₄ membrane with a thickness of 226 nm only exhibits a permeance of 60 L h^?1 m^?2 bar^?1. Simultaneously, SO₃H sites firmly anchor nitrogen with base functionality distributing onto g‐C₃N₄ through acid–base interactions. This enables the nanochannels of g‐C₃N₄ based membranes to be stabilized in acid, basic, and also high‐pressure environments for long periods.