SU-77: An Open-Framework Germanate Containing 12 × 10 × 10-RingChannels Solved by Combining Rotation Electron Diffraction and PowderX-ray Diffraction.

A novel open-framework germanate,denoted as SU-77, was preparedby hydrothermal synthesis using ethylenediamine as the structure directingagent. The as-synthesized SU-77 is monoclinic with space group P21/aand a= 13.52427(5) Å, b= 12.64862(5) Å, c= 9.60578(3) Å, β = 92.8599(4)°. The structureof SU-77 is built from a novel Ge6O17(C2H8N2)F (Ge6) cluster buildingunit. The Ge6clusters are connected to form chains alongthe c-axis. These chains are further connected inthe [110] and [1–10] directions to form a three-dimensionalframework with 12 × 10 × 10-ring channels. The as-synthesizedmonoclinic SU-77 became orthorhombic while being observed in a transmissionelectron microscope (TEM) or when heated to 200 °C in air. Theorthorhombic structure of SU-77 was solved from micrometer-sized crystalsby rotation electron diffraction (RED). The monoclinic structure wasbuilt from the orthorhombic structure and subsequently refined againstsynchrotron powder X-ray diffraction data. SU-77 is the first exampleof an open-framework germanate with mixed coordination polyhedra solvedby electron diffraction. [ABSTRACT FROM AUTHOR]