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-dimensiona l sheets. The experimental evidence for the presence of these two-dimension al sheets is, however, rather rare. By using alkali metal cations (K+) to r eplace organic structure-directing agents, one such two-dimensional sheet h as been preserved in a crystalline product denoted as UCSB-9L, a hydrated l ayered germanate with three- and nine-membered rings. The implication of th is work on the self-assembly mechanism is that the structure-directing effe ct of organic molecules may only need to be active in a narrow range along the reaction coordinate.