Enhanced permeation performance of polyether-polyamide block copolymer membranes through incorporating ZIF-8 nanocrystals

Membrane-based CO₂ separation is a promising alternative in terms of energy and environmental issues to other conventional techniques. Polyether-polyamide block copolymer (Pebax) membranes are promising for CO₂ separation because of their excellent selectivity, but limited by their moderate gas permeability. In this study, fresh-prepared zeolitic imidazolate framework-8 (ZIF-8) nanocrystals were integrated into the Pebax®1657 matrices to form mixed matrix membranes. The resulting membrane exhibits significantly improved CO₂ permeability (as high as 300% increase), without the sacrifice of the selectivity, to the pristine polymer membrane. Several physical characterization techniques were employed to confirm the good interfacial interaction between ZIF-8 fillers and Pebax matrices. The effect of added ZIF-8 fillers on the transport mechanism through MMMs is also explored. Mixed-gas permeation for both CO₂/N₂ and CO₂/CH₄ was also evaluated. The separation performance for CO₂/CH₄ mixtures on the ZIF-8/Pebax MMMs is very close to the Roberson upper bound, and thus is technologically attractive for purification of natural gas.