Hydrothermal synthesis and structural characterization of zeolite-like structures based on gallium and aluminum germanates

While extensive commercial success has been achieved through the use of organic molecules in the synthesis of aluminosilicate zeolites, the synthesis of the germanium-based zeolite structures using organic structure-directing agents is a largely unexplored area. Here we report a novel class of germanate zeolite structures prepared with inorganic cations or organic amines as structure-directing agents. These new materials possess five 4- connected 3-dimensional topologies with large (12-ring), medium (10-ring), small (8-ring), or ultrasmall (6-ring) pores. They have a variety of chemical compositions such as various Ge to Ga (or Al) ratios and exhibit interesting structural features such as helical chains and odd-membered rings. UCSB- 15GaGe and UCSB-15AlGe are the first germanate-based structures with 5- rings. UCSB-7 refers to a collection of isostructural, large-pore zeolite- like structures constructed by the cross-linking of helical ribbons. UCSB- 3GaGe is the only known T₃⁺/T⁴⁺ (T refers to tetrahedral atoms) based zeolite structure with the net 38 topology. This structure is unusual because of its very high framework charge density unsurpassed by other amine-directed zeolite structures. GaGe-SOD2 and AlGe-SOD2 (sodalite analogues) have an unusually low framework symmetry for a sodalite structure. The cubic GaGe- SOD1 (or AlGe-SOD1) and the triclinic GaGe-SOD2 (or AlGe-SOD2) are ideal examples of the compositional and structural control of the inorganic framework by structure-directing amines. GaGe-ANA1 and GaGe-ANA2, two gallogermanate analcime analogues, are noncentrosymmetric, unlike many other analcime structures.