Imidazole functionalized graphene oxide/PEBAX mixed matrix membranes for efficient CO2 capture

•ImGO as a CO2-philic filler was blended in PEBAX to improve CO2 separation ability.•The selectivity of MMM for CO2/N2 increased by 46.0% compared to PEBAX membrane.•ImGO 0.8 exhibited the best CO2 separation performance surpassing the Upper Bound. Mixed matrix membranes (MMMs) were composed of imidazole functionalized graphene oxide (ImGO), a CO2-philic nano-sheet inorganic material, and poly(ether-b-amide) (PEBAX) for CO2 capture. MMM doped with 0.8wt.% ImGO exhibits the best CO2 separation performance, which shows the CO2/N2 selectivity up to 105.5 combined with CO2 permeability of 76.2 Barrer (1 Barrer=10−10cm3(STP)cmcm−2s−1cmHg−1), surpassing the Robeson Upper Bound of 2008. The selectivity of MMM for CO2/N2 increases by 46.0% compared to the Pristine PEBAX due to the interaction between CO2 and imidazole groups. With the increase of feed pressure, CO2 permeability increases significantly because of its higher solubility in polymer matrix and plasticization. It is effective to separation CO2 from N2 at lower temperature for MMMs because the apparent activation energy of the N2 permeation process in ImGO/PEBAX MMMs is much higher than that of CO2. Tg of MMMs are increased gradually because the polymer chain mobility is restricted by the presence of ImGO and a rigidified interface generates between polymer and filler. The mechanical properties have been significantly enhanced by the ImGO sheet as expected because of the presence of H-bonding. Having distinct improvement of CO2 separation performance, the ImGO/PEBAX MMMs indicates promising applications in CO2 capture processes.