Effect of end groups and grafting on the CO₂ separation performance of poly(ethylene glycol) based membranes

Rubbery membranes have attracted significant attention for the CO ₂/light gas separation due to their relative high permeability and high solubility selectivity. This work reports universal strategies to tailor CO₂ permeability and CO₂/light gas permselectivity via blending or grafting of poly(ethylene glycol) (PEG) derivatives into or onto organic-inorganic membrane (OIM) substrates. A PEG derivative is blended into the substrate which contains inorganic siloxane networks and poly(ethylene oxide) segments followed by thermal grafting. Ultrahigh CO₂ permeability (982 barrer at 45 °C) is achieved via physical blending, while extremely high CO₂ permeability (1840 barrer at 45 °C) is obtained after chemical grafting. Neither of these two modification methods shows the loss of CO₂/H₂ and CO₂/N₂ selectivity compared to the substrate. Melting and crystallization behaviors of this PEG derivative are believed to significantly affect the overall gas permeation performance. All the features make these OIMs promising membrane materials for CO₂ capture.