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

摘要

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.