Anhydrous interfacial polymerization of sub-1 Å sieving polyamide membrane

Highly permeable polyamide (PA) membrane capable of precise ionic sieving can be utilized for many energy-efficient chemical separations. To fulfill this target, it is crucial to innovate membrane-forming process to induce a narrow pore-size distribution. Herein, we report an anhydrous interfacial polymerization (AIP) at a solid-liquid interface where the amine layer sublimated is in direct contact with the alkane containing acyl chlorides. In such a heterophase interface, water-caused side reactions are eliminated, and the amines in compact arrangement enable an intensive and orderly IP reaction, leading to a unique PA layer with an ionic sieving accuracy of 0.5 Å. The AIP-PA membrane demonstrates excellent separation selectivities of monovalent and divalent cations such as Mg²⁺/Li⁺ (78.3) and anions such as Cl^-/SO₄^2- (29.2) together with a high water flux up to 13.6 L m^-2 h^-1 bar^-1. Our AIP strategy may provide inspirations for engineering high-precision PA membranes available in various advanced separations.