Ultrathin Aromatic Polyamide Membranes with Tunable Microporosity for Molecular Sieving

Abstract Advanced membrane technology for the separation and purification of active pharmaceutical ingredients (APIs) requires improvement in both membrane materials and manufacturing processes to achieve the high rejection of macromolecular solutes combined with high permeance for organic solvents in pharmaceutical industry. Here, we report a novel approach to preparing aromatic polyamide membranes (PAMs) with tunable microporosity and micropore size via modulator‐assisted interfacial polymerization. Enhanced microporosity, increased micropore size, and higher pore interconnectivity of PAMs are achieved by adding ethanol to the aqueous phase to regulate interfacial polymerization, which can be demonstrated through experiments and molecular simulations. The resulting optimal membrane achieves a methanol permeance of 11.9 L m − 2 h −1 bar −1 , representing a impressive 19.8‐fold increase compared to commercial benchmark membrane (0.6 L m −2 h −1 bar −1 ) at the same molecular weight cut‐off (∼460 g mol −1 ). For practical applications, the optimal membrane demonstrates exceptional capability in the separation of high‐value APIs such as dipyridamole, achieving not only accelerated ethanol permeance but also a 6‐fold enrichment factor relative to commercial membranes. This work demonstrates the significant potential of phenolphthalein‐based microporous polyamide membrane in advancing API separation technologies. It provides valuable insights into the development of next‐generation membrane systems tailored for pharmaceutical applications.