Enhancing the organophilic separations with mixed matrix membranes of PIM-1 and bimetallic Zn/Co-ZIF filler

Novel mixed matrix membranes (MMMs) were fabricated by incorporating bimetallic Zn/Co-ZIF nanoparticles into the prototypical polymer of intrinsic microporosity (PIM-1). The morphological and structural characteristics of Zn/Co-ZIF and ZIF-8 were analyzed with XRD, FTIR, BET and SEM. The characterization results showed that the Zn/Co-ZIF is isostructural to ZIF-8 occupying the same crystallographic sites, however, Zn/Co-ZIF has smaller BET surface area and lower pore volume than ZIF-8. The SEM images of fabricated MMMs demonstrated good dispersion and interaction of the filler in the polymer matrix, even at high loadings. The addition of hydrophobic nanoparticles enhanced the hydrophobicity of the MMMs, and relatively more for the Zn/Co-ZIF/PIM. The MMMs were analyzed for their separation performance of two binary mixtures made of ethanol/water and butanol/water comprising 5 wt% alcohol, via pervaporation. Flux and separation factor of both alcohols increased with filler loadings in both ZIF-8/PIM-1 and Zn/Co-ZIF/PIM-1 membranes, showing an anti-tradeoff effect which is more significant in Zn/Co-ZIF/PIM-1 membranes. Zn/Co-ZIF/PIM-20 wt% membranes showed 129% higher separation in comparison with pristine PIM-1 membranes. Moreover, not only did the Zn/Co-ZIF/PIM-1 membranes show a higher separation factor, but they also had a higher rate of increase with increased loadings, which was quasi-constant for ZIF-8/PIM-1 membranes. ZIF-8/PIM-1 at filler loading of 20 wt% showed the highest normalized flux of 139 kg.µm.m-2.h-1.

Keywords: PIM-1; ZIF-8; Zn/Co-ZIF; Mixed Matrix Membranes; Pervaporation.