Multifunctional Amine-Containing PVA- g-POEM Graft Copolymer Membranes for CO₂ Capture

CO₂ separation technology using polymeric membranes has emerged as a viable solution to mitigate the rapidly increasing anthropogenic CO₂ emissions, which are directly linked to global warming and climate anomalies. However, in order to improve the gas separation performance, an intrinsic problem of polymeric membranes, i.e., a trade-off relationship between permeability and selectivity, needs to be addressed. In this study, a solid-state facilitated transport membrane is prepared by blending CO₂-philic, amine-compatible poly(vinyl alcohol)-g-poly(oxyethylene methacrylate) (PVA-g-POEM) graft copolymer and diethylenetriamine (DETA) carriers. The graft copolymer consisting of PVA main chains and POEM side chains is synthesized via one-pot free radical polymerization and used as a polymer matrix. With the incorporation of 10 wt % of DETA into the polymer, the membrane exhibits a high CO₂ permeance of 402.5 GPU (1 GPU = 10^-6 cm³(STP)/(s·cm²·cmHg)) and CO₂/N₂ selectivity of 52.1. The enhanced performance of the membrane results from multifunctional amine carriers in the graft copolymer owing to facilitated transport of CO₂ and an increase in the crystallinity of the polymer. DETA acts as a seed for crystallization of PVA chains at a low loading, which leads to a reduced N₂ permeance. The membrane exhibits good stability without any performance degradation over 2 weeks in the solid state. The superior separation property of the PVA-g-POEM membrane containing DETA distinguishes this facilitated transport membrane from other similar membranes and commercial membranes.