Mixed matrix membranes (MMMs) using an emerging metal-organic framework (MUF-15) for CO2 separation

Inorganic fillers can largely determine the ultimate performance of mixed matrix membranes (MMMs). The identification of new inorganic fillers is therefore crucial for the continued development of MMMs. MMMs that contain metal-organic framework (MOF) fillers have been extensively investigated. However, high-performance MOF fillers remain scarce and are in high demand. In this study, MUF-15 (Massey University Framework-15), an emerging MOF possessing exceptional physicochemical properties, was combined into MMM with PIM-1 for the first time. Owing to its intrinsic ability to discriminate different guest molecules, MUF-15 is an excellent filler that delivers MMMs with exceptional CO2 separation properties. Also, the layered structure of MUF-15 enabled the exfoliation of crystalline nanosheets leading to the significant enhancements of both CO2 permeability and selectivity even when only a small quantity of <5 wt% was incorporated. In addition, MUF-15 fillers could effectively inhibit the physical aging process of PIM-1 membranes. After 35 days, MMMs with a 2 wt% loading of MUF-15 nanosheets showed 155 % higher CO2 permeability, with identical CO2/N2 selectivity (25.5), relative to pristine PIM-1 membranes, which all still surpassed the 2008 upper bound. The isoreticular chemical modification of MUF-15 is proposed as a strategy to increase to further improve the MMM performance.