Abstract
A novel open-framework germanate [(C5H14N2)(2)(C5H12N2)(0.5)(H2O)(2.5)][Ge12.5O26(OH)(2)] with three-dimensional 10- and 11-ring channels, denoted as SU-67, has been synthesized under hydrothermal conditions using 2-methylpiperazine (MPP) as the structure-directing agent (SDA). The synthesis is intimately related to that of JLG-5, a tubular germanate built from Ge-7 clusters. The influences of synthesis parameters are discussed. A strong influence of the hydrofluoric acid quantity on the resulting cluster building units can be concluded. The framework of SU-67 is based on an elaborate topological pattern of connected Ge-10 clusters forming intersecting 10- and 11-ring channels and has a low framework density (12.4 Ge atoms per 1000 angstrom(3)). We have discovered that the topology of SU-67 is a new 8-connected nce-8-I4(1)/acd net. Strong hydrogen bonding among the organic SDAs, water molecules, and Ge-10 clusters resulted in helical networks in SU-67.