Polyethyleneimine-functionalized phenolphthalein-based cardo poly(ether ether ketone) membrane for CO2 separation

Phenolphthalein-based cardo poly(ether ether ketone) (PEEKWC)/polyethyleneimine (PEI) crosslinking membranes were prepared by solution casting followed by solution reaction at room temperature. The effects of reaction time and PEI content on the membrane structure and gas separation performances were investigated. Light transmittance measure and AFM evidenced the relationship between the microphase separation in PEEKWC-PEI membranes and reaction time. The CO 2 permeability increased with the PEI content, while the N 2 and CH 4 permeability remained nearly constant. This result indicated that only CO 2 was transported by the solution–diffusion mechanism and also that PEI exhibited a positive contribution as a fixed carrier for CO 2 facilitated transport. Meanwhile the PEEKWC-PEI crosslinking membranes showed higher selectivities than the pure PEEKWC membrane. The highest CO 2 /N 2 and CO 2 /CH 4 selectivities were about 131 and 122 increasing from 33 and 30, respectively. The crosslinking structure of membranes improved the CO 2 permeability stability.