Effect of ionic liquids (ILs) on MOFs/polymer interfacial enhancement in mixed matrix membranes

Strong interfacial interactions between the filler(s) and chosen polymer in mixed matrix membranes (MMMs) is a crucial factor in obtaining high gas separation efficiency. However, it is challenging to obtain excellent filler/polymer contact simply by direct incorporation of micron-sized metal-organic frameworks (MOFs) into a polymer matrix without modification. In this study micron-sized ZIF-67 particles were coated with a thin layer of 3 different ionic liquids (ILs) and characterized for the change in adsorption properties. The coated ZIF-67 particles were then incorporated into 6FDA-durene polymer at different loadings to fabricate MMMs for gas separation. Playing the role of interfacial binder, all ILs effectively enhanced the polymer/ZIF adhesion, minimizing the formation of non-selective interfacial defects, which was evidenced by the scanning electron microscopy (SEM) as well as by the focus ion beam scanning electron microscopy (FIB-SEM), leading to an increment in CO/N, CO/CH and CH/CH selectivity. The successful combination of ZIF-67/IL is proposed as a potential method to overcome the interfacial issues in MMMs, particularly in the application of larger micron-sized fillers