Journal of Materials Science, Vol.51, No.3, 1562-1571, 2016
Resolving topography of an electron beam-sensitive oxalate-phosphate-amine metal-organic framework (OPA-MOF)
Scanning electron microscopy (SEM) has, for many years, been the favoured method to gain insights into morphology, micro- and surface structure of new materials, thus development of SEM instruments and modes of use has been rapid. Yet, high-quality, charge artefact-free SEM-representation of highly beam-sensitive non-conductive hybrid metal-organic frameworks (MOF) remains challenging, particularly if access to highly specialised instrumentation is limited-a situation many researchers face. This study details a systematic approach taken to determine the appropriate instrument operating conditions and sample preparation methods for characterisation of a oxalate-phosphate-amine MOF (OPA-MOF) under conventional high-vacuum SEM conditions. We show that a double-coating method adapted from biological sciences, where a carbon coating (<= 15 nm) is followed by a thin gold coating (similar to 3-5 nm), enables charge- and damage-free imaging of the electron beam-sensitive OPA-MOF. Details of micro-topography are sufficiently resolved for intended purposes (similar to 100 nm) and are not unduly masked by the coating.