Mixed matrix membranes with fast and selective transport pathways for efficient CO₂ separation

To improve CO₂ separation performance, porous carbon nanosheets (PCNs) were used as a filler into a Pebax MH 1657 (Pebax) matrix, fabricating mixed matrix membranes (MMMs). The PCNs exhibited a preferential horizontal orientation within the Pebax matrix because of the extremely large 2D plane and nanoscale thickness of the matrix. Therefore, the micropores of the PCNs provided fast CO₂ transport pathways, which led to increased CO₂ permeability. The reduced pore size of the PCNs was a consequence of the overlapping of PCNs and the polymer chains penetrating into the pores of the PCNs. The reduction in the pore size of the PCNs improved the CO₂/gas selectivity. As a result, the CO₂ permeability and CO₂/CH₄ selectivity of the Pebax membrane with 10 wt% PCNs-loading (Pebax-PCNs-10) were 520 barrer and 51, respectively, for CO₂/CH₄ mixed-gas. The CO₂ permeability and CO₂/N₂ selectivity of the Pebax-PCNs-10 membrane were 614 barrer and 61, respectively, for CO₂/N₂ mixed-gas.