Nanostructured and Oriented Metal-Organic Framework Films enabling Extreme Surface Wetting Properties

Abstract

Herein, we report on the synthesis of highly oriented and nanostructured metal-organic framework (MOF) films featuring extreme surface wetting properties. The Ni- and Co- derivatives of the metal-catecholate series (M-CAT-1) were synthesized as highly crystalline bulk materials and thin films. Oriented pillar-like nanostructured M-CAT-1 films exhibiting pronounced needlelike morphology on gold substrates were established by incorporating a crystallization promoter into the film synthesis. These nanostructured M-CAT-1 MOF films feature extreme wetting phenomena, specifically superhydrophilic and underwater superoleophobic properties with water and underwater oil-contact angles of 0º and up to 174º, respectively. Self-cleaning capabilities for the nanostructured, needle-like M-CAT-1 films were illustrated by measuring time-dependent oil droplet rolling-off a tilted surface. The deposition of the nanostructured Ni-CAT-1 on large glass substrates allowed for the realization of an efficient transparent anti-fog coating enabling a clear view even at extreme temperature gaps up to ca. 120 ºC. This work illustrates the strong link between MOF film morphology and induced surface properties based on these framework materials.