Simulation and Experiment of CO₂ Philicity and Separation in Carbonate-Rich Polymers

Functional polymers containing CO2-philic groups are of great interest for membrane CO2/gas separation for carbon capture. This work, for the first time, systematically elucidates the effect of carbonate groups on CO2/gas solubility selectivity and permselectivity using an integrated simulation and experimental approach in two carbonate-rich polymers: poly(ethylene carbonate) (PEC) and poly(propylene carbonate) (PPC). Both polymers are amorphous and rubbery at 35 degrees C, and they are thoroughly characterized for physical properties and CO2/gas separation properties. PEC exhibits a CO2/C2H6 solubility selectivity of 24 at 35 degrees C, much higher than that of poly(ethylene oxide) (2.8), one of the leading membrane materials for CO2/gas separation. The binding energy between gas molecules and polymer analogue was calculated using density functional theory (DFT), and the results are consistent with the experimental sorption data. Both PEC and PPC show CO2/CH4 permselectivity of approximate to 53 at 35 degrees C, the highest reported for rubbery polymers. PEC also exhibits a CO2/N-2 permselectivity of 74, one of the best reported in the literature. Although polar carbonate groups may lower gas permeability, they can be incorporated into polymer architectures to improve CO2/gas selectivity.