Novel mixed matrix membranes containing calixarene for enhanced CO2/N2 separation

Calixarene possessing advantages of small intrinsic cavity size, small particle dimension, and facile dispersion or dissolution in common solvents, is promising filler candidates in mixed matrix membranes (MMMs) for gas separation. Herein, the supramolecular C-propylpyrogallol[4]arene (PgC₃) was successfully synthesized via a phenolic resin condensation reaction. It was then incorporated into a polyether-polyamide block copolymer (Pebax-1657) to prepare mixed matrix membranes (MMMs) with varying PgC₃ loadings for CO₂/N₂ separation. The formation of hydrogen bonds between PgC₃ and Pebax facilitated the uniform dispersion of PgC₃ within the polymer matrix, enhancing interfacial compatibility. The incorporation of PgC₃ significantly enhanced the CO₂/N₂ selectivity of the Pebax while preserving its permeability. The 1 wt% PgC₃/Pebax MMMs performs the best CO₂/N₂ selectivity of 58.6, substantially higher than that of pristine Pebax membrane (32.4). This improvement can be attributed to the strong affinity between the abundant –OH groups in PgC₃ and CO₂ molecules. Moreover, the PgC₃/Pebax MMMs exhibited exceptional stability under operating pressures of up to 5 bar, maintaining its performance consistently throughout a demanding100-hour test. The good separation performance together with the excellent stability enables PgC₃ a promising filler in MMMs for CO₂/N₂ or other gas separations.