Amine-Appended Hierarchical Ca-A Zeolite for Enhancing CO₂ /CH₄ Selectivity of Mixed-Matrix Membranes

An amine-appended hierarchical Ca-A zeolite that can selectively capture CO₂ was synthesized and incorporated into inexpensive membrane polymers, in particular polyethylene oxide and Matrimid, to design mixed-matrix membranes with high CO₂ /CH₄ selectivities. Binary mixture permeation testing reveals that amine-appended mesoporous Ca-A is highly effective in improving CO₂ /CH₄ selectivity of polymeric membranes. In particular, the CO₂ /CH₄ selectivity of the polyethylene oxide membrane increases from 15 to 23 by incorporating 20 wt % amine-appended Ca-A zeolite. Furthermore, the formation of filler/polymer interfacial defects, which is typically found in glassy polymer-zeolite pairs, is inhibited owing to the interaction between the amine groups on the external surface of zeolites and polymer chains. Our results suggest that the amine-appended hierarchial Ca-A, which was utilized in membrane fabrication for the first time, is a good filler material for fabricating a CO₂ -selective mixed-matrix membrane with defect-free morphology.