Mesoporous compound semiconductors from the reaction of metal ions with deltahedral [Ge9]4- clusters

We report the surfactant-directed assembly of mesoporous metal/germanium-based semiconducting materials from coupling of anionic (Ge-9)(4-) clusters with various linking metal ions. The resulting materials feature a metal/Ge-9 framework perforated by regular arrays of mesoporous channels. The permanent mesoporosity of the materials NU-MGe-2 (M = Sb, In, Sri, Pb, Cd), determined by N-2 physisorption measurements, corresponds to high internal BET surface areas from 127 to 277 m(2)/g and total pore volumes from 0.15 to 0.26 cm(3)/g. The mesoporous structures exhibit energy gaps in the range of 1.48-1.70 eV as well as strong photoluminescence at room temperature with emission energies varying from 740 to 845 rim. The emission depends on pore wall thickness and framework composition. The photoemission intensity in the mesoporous intermetallic germanium-based frameworks can be selectively suppressed by adsorbing electron-acceptor species such as tetracyanoethylene molecules but remains unchanged when exposed to electron-donor species such as tetrathiafulvalene molecules.