Pillar[5]arene-enabled dual regulation of interfacial polymerization for high-performance reverse osmosis membranes

A macrocyclic pillar[5]arene is introduced as an interfacial polymerization regulator. • MPD diffusion is reduced while interfacial reactivity is suppressed. • Controlled polymerization yields a thinner and more compact PA layer. • Enhanced RO performance with maintained water permeance. The interfacial polymerization (IP) of m -phenylenediamine (MPD) and trimesoyl chloride (TMC) is widely used to fabricate polyamide (PA) reverse osmosis (RO) membranes, yet its ultra-fast and diffusion-limited nature leads to poor controllability of the PA structure. Herein, a dual kinetic and thermodynamic regulation strategy is proposed using a macrocyclic additive, per-sulfonated pillar[5]arene (P[5]-SO 3 ), to control the IP process. The introduction of P[5]-SO 3 lowers the aqueous-phase pH and alters the interfacial reaction equilibrium, while its bulky structure suppresses MPD diffusion. This dual regulation enables the formation of a thinner and more highly crosslinked PA layer. As a result, the optimized membrane achieves significantly improved NaCl rejection (99.51%) compared to the pristine membrane (95.65%) while maintaining higher permeance (3.81 L m −2  h −1  bar −1 ), along with enhanced antifouling performance. This work provides a new strategy for precise control of interfacial polymerization toward high-performance RO membranes.