Interplay between morphology and band gap energy in Fe-MIL-88A prepared via a high temperature surfactant-assisted solvothermal method

Metal-Organic Frameworks (MOFs) are a new class of crystalline microporous solids with superior properties compared to their inorganic counterparts that offer a great variety of properties. Fe-MIL-88A is a biocompatible MOF with a flexible structure that can be synthesized in various morphologies via different chemical methods. The present study proposes two efficient methods, namely, microemulsion and surfactant-assisted solvothermal method, to prepare Fe-MIL-88A nanorods with narrow size distribution and well-defined morphology. The morphology, crystalline and chemical structure of the prepared samples were studied using FESEM images, XRD patterns and FTIR spectra, respectively, and their absorption behavior was scrutinized using UV–Vis spectroscopy. It was observed that MOF nanorods had size and morphology-dependent electronic properties. The band gap energy was inversely proportional to the particle diameter. While MOF microrods showed a single band gap of 2.63 eV, their nanorods showed two band gap energies of about 3.1 and 3.6 eV. Based on the obtained results, the application of MOFs with the desired size and morphology in the field of band gap engineering seems possible.