GeB4O9 x H2en: an organically templated borogermanate with large 12-ring channels built by B4O9 polyanions and GeO4 units: host-guest symmetry and charge matching in triangular-tetrahedral frameworks.

A new borogermanate open-framework, FJ-18, with intersecting 12-/8-, 9-, and 9-ring channels in multidimensions was synthesized by using an organic diamine as structure-directing agent (SDA). X-ray diffraction showed that its structure is constructed by flexible connection of strictly alternate B(4)O(9) clusters (with fictitious tetrahedral geometry) and GeO(4) tetrahedra to form a zeotype framework with the CrB(4) topology. The topology and structural relations between FJ-18 and FJ-16, a known borogermanate based on the linkage of B(4)O(9) clusters and GeO(4) units, are described in detail. Different guest SDAs can, by means of their shape, size, and charge, directly influence the structure of the host framework, and the origin of these phenomena can be attributed to fundamental parameters such as host-guest symmetry and charge matching through H-bonding interactions, the concept of which has for the first time been extended to tetrahedral-triangular frameworks. This result is a part of our ongoing work aimed at making new large-pore materials constructed from B-O polyanions and Ge-O cluster units.