Wet-coating amino-functionalized PDMS interlayer boosting thin film composite membranes for efficient CO2 separation

Membrane separation is in the spotlight as one of the most cost-effective technologies without chemicals for carbon capture. This work aims to fabricate thin film composite (TFC) membranes for boosting CO₂ separation. Commercial polysulfone (PSf) flat sheet membranes pre-treated with ethanol solutions were used as support materials by coating with amino-functionalized cross-linked polydimethylsiloxane (PDMS) interlayer. It is worth noting that the developed amino-functionalized PDMS interlayer based on a novel wet-coating method to avoid the penetration of coating solution, which provides better compatibility with the coated polyamide selective layer and also the facilitated transport for CO₂ permeation. A thin CO₂-selective layer was obtained by interfacial polymerization (IP) between trimesoyl chloride (TMC) in the organic phase and diethylene glycol bis(3-aminopropyl) ether (DGBAmE or EO3) in the aqueous phase to enhance the CO₂/N₂ selectivity. Both the IP process and the membrane preparation parameters such as heat-treatment temperature, and monomer concentration were systematically optimized. It was found that the best membrane prepared with 9.9 mmol/L TMC monomer solution presents a CO₂ permeance of 81 GPU and a CO₂/N₂ selectivity of 65, which was significantly enhanced from the non-selective supports. This work provides a facile approach for tuning the TFC membrane performance for CO₂ separation and can be extended to make high-performance membranes for industrial CO₂ capture by selecting more permeable supports.