Rapid solvent transport and tunable molecular sieving enabled by ultrathin alkyl-chain-engineered polyamide membranes

Organic solvent nanofiltration (OSN) has emerged as a promising separation technology for the chemical and pharmaceutical industries due to its low energy consumption and eco-friendliness. However, traditional polyamide-based membranes used in OSN often exhibit low permeance for organic solvents and it is difficult to precisely control the pore structure. In this study, we report a facile approach to fabricate ultrathin alkyl-chain-engineered polyamide nanofilms via free-standing interfacial polymerization for high-performance selective separations. The membranes were prepared via a “two birds one stone” strategy, enabled by post-treatment in aliphatic amine solution, simultaneously regulating the pore size and optimizing the membrane chemical property. This enables the membrane with high solvent permeance, especially for non-polar solvents (heptane at ∼22.2 L m⁻²h⁻¹ bar⁻¹, toluene at ∼16.8 L m⁻²h⁻¹ bar⁻¹), while maintaining excellent molecular sieving capability. Notably, the molecular weight cut-off (MWCO) can be regulated by introducing alkyl chains of varying lengths to their pores. The exceptional solvent permeance and tunable molecular sieving property make the membranes promising for high value-added products purification in the pharmaceutical industry and crude oil separation.