MOFs are crystalline inorganic-organic networks composed of metal nodes connected by multi-dentate organic molecules. They assemble into three-dimensional structures with high internal surface area and defined pore sizes. Due to these properties, synthetic efforts over the past decade have focused on the development of MOFs for gas storage and separation. These previous investigations have led to an immense amount of knowledge pertaining to synthetic control of MOF structure and the interactions between MOFs and small molecules. As MOFs organize molecular components into networks, the overall material properties are thus a summation of the individual molecular properties. For this reason, MOFs are uniquely poised for use as semiconductor materials. By the inclusion of tailored molecules with discrete HOMO-LUMO energy levels, for example the π and π * orbitals for aromatic systems, into the overall network these orbitals overlap and create a band of states. This leads to semiconducting behavior with conduction and valence bands related to the molecular π and π * orbital energies. In short, MOFs represent the only class of compounds that allow for variation in semiconductor energetics by simple synthetic manipulation of the organic molecules incorporated.
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