Stable, crystalline, microporous materials are of immense practical importance for commercial applications such as catalysis, absorption, ion-exchange, and separation. [1, 2] The continuing need for microporous materials that display new framework topologies and novel catalytic properties has spurred increasing interest in extending the range of known structure types and compositions. To date, the vast majority of microporous materials are constructed from tetrahedral building units. [3, 4] A much smaller class of materials are those constructed from mixed octahedral ยฑ tetrahedral frameworks. Such materials are likely to display framework topologies and properties that are substantially different from those observed in purely tetrahedral materials. [5] However, a limited number of such mixed frameworks have been reported to date.
The synthesis of microporous niobium silicates and germanates is a particularly unexplored area. The only structurally characterized examples are niobium-containing nenadkevichite analogues, [6] and an open-framework potassium niobium germanate, [K 3 Nb 5 GeO 16 ] ยด2 H 2 O, synthesized hydrothermally at very high temperatures and pressures. [7] The hydrothermal synthesis of a microporous sodium niobium silicate, AM-11, has been reported, but its structure is currently unknown. [8] We are not aware of any reported syntheses of organically templated niobium silicate or germanate materials performed under mild (200 8C, P 25 atm) hydrothermal conditions.
We report here the synthesis of the first organically templated open-framework niobium silicate and germanate phases, namely [(C 4 N 2 H 11 )Nb 3 SiO 10 ] (NSH-1) and [(C 4 N 2 H 11 )-Nb 3 GeO 10 ] (NGH-1). [(C 4 N 2 H 11 )Nb 3 SiO 10 ] (NSH-1) and [(C 4 N 2 H 11 )Nb 3 GeO 10 ] (NGH-1) were synthesized in high yield (b 70 % based on Nb) under hydrothermal conditions.