Pebax-Based Mixed-Matrix Membranes Incorporating Carboxyl-Functionalized PIM-Derived Polymer Dots for Enhanced CO2/N2 Separation

Incorporating porous nanofillers into polymeric membranes has emerged as an effective strategy for overcoming the permeability–selectivity trade-off in CO2 separation. Carboxyl-functionalized polymer dots (Pdots) derived from a polymer of intrinsic microporosity (PIM-1) were developed and incorporated into a Pebax matrix to fabricate mixed-matrix membranes (MMMs) for CO2/N2 separation. The porous PIM-1-derived framework provided additional pathways for gas transport, whereas the carboxylic acid functionalities introduced by poly(styrene-co-maleic anhydride) (PSMA) enhanced the CO2 affinity and polymer–filler compatibility. As a result, Pdot incorporation simultaneously improved the CO2 permeability and CO2/N2 selectivity compared with those of pristine Pebax membranes. Among the prepared membranes, the MMM containing 0.5 wt % Pdot exhibited the best separation performance, achieving a CO2 permeability of 232.61 Barrer and a CO2/N2 selectivity of 53.47, compared with 148.99 Barrer and 40.27, respectively, for pristine Pebax. Consequently, the membrane performance approached the 2008 Robeson upper bound for the CO2/N2 separation. These findings demonstrate an effective strategy for engineering polymer-compatible porous nanofillers to regulate the membrane microstructure and gas transport in mixed-matrix membranes for CO2/N2 separation.