Isolation of Germanate Sheets with Three-Membered Rings: A Possible Precursor to Three-Dimensional Zeolite-Type Germanates

The generation of 4-connnected three-dimensional zeolite-type framework can be conceptually considered as resulting from the linking of two-dimensional sheets. The experimental evidence for the presence of these two-dimensional sheets is, however, rather rare. By using alkali metal cations (K+) to replace organic structure-directing agents, one such two-dimensional sheet has been preserved in a crystalline product denoted as UCSB-9L, a hydrated layered germanate with three- and nine-membered rings. The implication of this work on the self-assembly mechanism is that the structure-directing effect of organic molecules may only need to be active in a narrow range along the reaction coordinate.