An organically-templated chiral borogermanate (CH3NH3)2[Ge(B4O9)] (1), has been solvothermally synthesized and characterized by elemental analysis, IR, PXRD, TGA, single-crystal X-ray diffraction and UV–vis spectrum. It crystallized in the monoclinic space group C2 (No. 5) with a = 10.249(1) Å, b = 9.449(1) Å, c = 6.956(2) Å, β = 131.76(2)°, V = 502.43(19) Å3, Z = 2. The structure is constructed by alternate linkage of GeO4 tetrahedra and B4O9 clusters to form a zeotype framework with diamond topology. Four intersecting channels with different sizes are observed. Large circular 10-ring channels are clearly extended along the  direction, 9-ring channels are running along the , , and  directions, respectively. Additionally, two pairs of the right- and left-handed channels couple together along the  and  directions, respectively. The preliminary investigations show that compound 1 exhibits second-harmonic generation (SHG) response and ferroelectric properties.
A chiral borogermanate open-framework is constructed by alternate linkage of GeO4 tetrahedra and B4O9 clusters, not only showing the large circular 10-ring channels but also exhibiting good NLO and ferroelectric properties.
Keywords: Borogermanate; Solvothermal synthesized; SHG; Ferroelectric property