Endowing g-C₃ N₄ Membranes with Superior Permeability and Stability by Using Acid Spacers

g-C₃ N₄ membranes were modulated by intercalating molecules with SO₃ H and benzene moieties between layers. The intercalation molecules break up the tightly stacking structure of g-C₃ N₄ laminates successfully and accordingly the modified g-C₃ N₄ 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-C₃ N₄ 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-C₃ N₄ membrane with a thickness of 226 nm only exhibits a permeance of 60 L h^-1  m^-2  bar^-1 . Simultaneously, SO₃ H sites firmly anchor nitrogen with base functionality distributing onto g-C₃ N₄ through acid-base interactions. This enables the nanochannels of g-C₃ N₄ based membranes to be stabilized in acid, basic, and also high-pressure environments for long periods.