Incorporation of 2D/3D porous materials in 6FDA-DAM polyimide-based membranes with enhanced CO2-based separation performance and aging resistance

Abstract

6FDA-DAM-based mixed-matrix membranes (MMMs) were created by simultaneously incorporating two-dimensional (2D) hexagonal boron nitride (h-BN) and three-dimensional (3D) porous nickel hexacyanoferrate (NiHCF) to alleviate the trade-off between permeability and selectivity, as well as physical aging in polymeric membranes. Each nanofiller played a complementary role: h-BN contributed to improving the mixed-gas selectivity, while NiHCF enhanced both permeability and selectivity. Experimental results showed that the CO₂ separation performance of the MMM with dual additives was moderately enhanced as compared to the pristine 6FDA-DAM membrane. Under the condition of 2 wt% h-BN and 5.5 wt% NiHCF, the CO₂ permeability increased by approximately 32.6 %, while the CO2/N2 selectivity increased by 9.5 %. Moreover, the performance degradation caused by physical aging after 15 months was partially mitigated. While the pristine 6FDA-DAM membrane showed a 64.3 % and 60.7 % decrease in CO₂ permeability and selectivity, respectively, MMM with 2 wt% h-BN and 5.5 wt% NiHCF exhibited lower degradation rates, which registered at 56.3 % and 56.7 %, respectively. These results suggest that the additives stabilize the pore structure of the polymer, thereby suppressing polymer chain rearrangement and loss of free volume.