Synthesis and Structure of KBGe₂O₆: The First Chiral Zeotype Borogermanate with 7-Ring Channels

Among the known zeolite topologies, odd rings are rare with the exception of 5-ring. We report here the hydrothermal synthesis and structural characterization of a novel compound, KBGe2O6, the first germanate-based zeotype material with 7-ring channels. It crystallized in the orthorhombic system, space group P212121 (No. 19), a = 4.8037(3) Å, b = 10.2063(7) Å, c = 10.7402(10) Å, V = 526.57(5) Å3, Z = 3. The framework topology of this compound is previous unknown with the vertex symbol 4·6·4·6·6·72(vertex1), 4·6·4·6·6·72(vertex2), and 6·6·6·6·62·72(vertex3). It is worth noting that the structure of the compound is chiral containing helices condensed from GeO4 tetrahedra, which arrange around 21 screw axes. Furthermore, the K+ ions within the channels are mobile and can be partially ion-exchanged with Na+ at room temperature.