(NH4)2Ge7O15: A Microporous Material Containing GeO4 and GeO6 Polyhedra in Nine-Rings

GeO4tetrahedra and GeO6octahedra, which form nine-rings (see sketch on the right), feature in the unprecedented structure of the microporous solid, (NH4)2Ge7O15. This compound provides the first evidence that in the GeO2/NH4+ system the cubic (NH4)3HGe7O16⋅n H2O is not the only existing phase, but depending on the GeO6/GeO4 ratio, differently charged frameworks can be generated.