Surface Engineering Layered Metal–Organic Framework to Enhance Processability and Stability in Water

Despite considerable advancements of metal–organic frameworks (MOFs), the practical implementation of MOFs is still hindered by issues of stability and processability. In this work, we sought to overcome these difficulties through surface engineering. As a proof of concept, we subjected ZIF-L with a unique layered crystal morphology to a shell-ligand exchange reaction. This resulted in the partial replacement of 2-methylimidazole by benzimidazole as the linker in the framework on the outer surface of the crystals, thereby changing the surface of the ZIF-L crystal from hydrophilic to hydrophobic. The engineered ZIF-L (hereafter referred to as Benz-ZIF-L) formed a stable dispersion in the nonpolar solvent, hexane. The suspension of Benz-ZIF-L in hexane was applied via spin coating to a porous substrate of poly(vinylidene fluoride) (PVDF), resulting in a thin film of high density. In contrast, the application of a suspension of pure ZIF-L in the same manner did not result in the formation of a thin film. Benz-ZIF-L also exceeded pure ZIF-L with regard to hydrothermal stability and acid/base resistance.