Transparent films of metal-organic frameworks for optical applications

The optical and structural quality of thin films of metal-organic frameworks (MOFs) is of utmost importance for most potential applications as sensors and other optical devices. In this work, a dipping robot equipped with an ultrasonic bath has been developed to prepare thin, homogenous surface-mounted MOFs (SURMOFs) with well-defined thicknesses and orientations. SURMOFs of type HKUST-1, prepared with and without ultrasonication, were characterized by means of XRD, SEM, AFM and UV-vis spectroscopy. It was found that the MOF films prepared with ultrasonication are significantly cleaner, more homogenous and have a considerably smaller surface roughness than MOF films prepared without ultrasonication. The higher film quality results in a tremendously improved transparency, making them perfectly suited for optical applications. (C) 2015 Elsevier Inc. All rights reserved.