Photo-oxidative PIM-1 based mixed matrix membranes with superior gas separation performance

Abstract

We have studied mixed matrix membranes (MMMs) consisting of a zeolite imidazolate framework-71 (ZIF-71, Zn(cbIm)₂) and polymer of intrinsic microporosity (PIM-1) with and without ultraviolet (UV) irradiation for various gas separations. Well compatible MMMs are formed between ZIF-71 nanoparticles and PIM-1. The incorporation of ZIF-71 considerably enhances the gas permeability without compromising the gas pair selectivities of O₂/N₂, CO₂/N₂ and CO₂/CH₄. The PIM-1 comprising 30 wt% of ZIF-71 exhibits a 154% increase in CO₂ permeability. Excellent agreement is found between the measured permeability and the Maxwell prediction. FESEM and PAS confirm the formation of an ultrathin dense layer at the membrane surface after the UV treatment. The photo-oxidative PIM-1 has CO₂/CH₄, CO₂/N₂ and O₂/N₂ selectivities of 34.1, 29.8 and 6.7, respectively, while the UV-treated MMMs possess much higher permeabilities compared to those of photo-oxidative PIM-1 with comparable gas pair selectivities. Under mixed gas tests, the UV treated PIM-1 containing 20 wt% ZIF-71 has a CO₂ permeability of around 2000 barrers and a CO₂/CH₄ selectivity of 32. This performance outperforms that of PIM-1 and UV treated PIM membranes. The UV-PIM-1/ZIF-71 membranes have superior separation performance with both high permeability and selectivity for CO₂/CH₄ or other gas pair separation.