A Germanate with a Collapsible Open-Framework

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• 作者：A. Ken Inge ; Kirsten E. Christensen ; Tom Willhammar ; Xiaodong Zou
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：December 7, 2016
• 年：2016
• 卷：16
• 期：12
• 页码：6967-6973
• 全文大小：575K
• ISSN：1528-7505

文摘

A novel open-framework germanate, |NC₂H₈∥N₂C₆H₁₈|[Ge₇O_14.5F₂]·4H₂O denoted SU-65 (SU = Stockholm University), with 24-ring channels and a very low framework density of 8.9 Ge atoms per 1000 ų was synthesized under hydro-solvothermal conditions. The framework of SU-65 is built of 5-connected Ge₇ clusters decorating the fee net and is a framework orientation isomer to ASU-16. Half of the 8- and 12-rings in ASU-16 are instead 10-rings in SU-65 due to the different orientations of half of the clusters in the crystal structure. Flexibility of the frameworks is also influenced by the orientation of the clusters. The unique unit cell angle in SU-65 changes upon heating, unlike ASU-16 which only undergoes changes in unit cell lengths. SU-65 undergoes significant structural changes at 180 °C in a vacuum, forming SU-65ht. The crystal structure of SU-65ht was investigated by rotation electron diffraction, X-ray powder diffraction, and infrared spectroscopy. Through these techniques it was deduced that SU-65ht has similar clusters, symmetry, and topology as SU-65, but one of the unit cell lengths is shortened by approximately 5 Å. This corresponds to a 22% decrease in unit cell volume.