Expanding interfacial polymerization for gas separation beyond water purification

Extending interfacial polymerization (IP) to gas separation is challenging due to microdefects in dry conditions, despite its attractive and straightforward processability. This study presents a systematic defect-tailoring approach for highly reproducible polyamide (PA) thin film composite (TFC) membranes with precise size-sieving ability. The approach combines highly porous polyethylene support, extended IP reaction time (60 min), and post-thermal/solvent treatments, resulting in a homogeneous PA selective layer. Particularly, isopropanol treatment removes less-reacted amine-rich monomers/oligomers and promotes PA network chain relaxation, enhancing molecular-sieving capability. The resulting PA TFC membrane exhibits a remarkable H2/CO2 selectivity of 24.8 (±3.1) and an H2 permeance of 13.6 (±1.8) gas permeation unit, surpassing the polymeric upper bound. It also ensures mechanical stability under high feed pressure and resistance to physical aging, highlighting its robustness. Additionally, universality is validated using different amine monomers. This systematic method provides a valuable framework for producing reproducible PA TFC membranes with exceptional gas separation performance, enabling practical implementation across industrial sectors. [Display omitted] •Highly reproducible polyamide (PA) thin film composite (TFC) membrane was prepared.•The porous support and longer IP reaction time ensured a uniform PA network.•Post-treatment using isopropanol effectively removed the residues in the PA network.•The resulting PA network showed excellent H2/CO2 separation performance.•Physical aging and plasticization were effectively suppressed in the PA network.