An Open-Framework Silicogermanate with 26-Ring Channels Built from Seven-Coordinated (Ge,Si)₁₀(O,OH)₂₈ Clusters

Abstract

We report a new open-framework silicogermanate SU-61 containing 26-ring channels with a low framework density. It can be seen as a crystalline analogue to the mesoporous silica MCM-41. The structure is built from the assembly of (Ge,Si)10(O,OH)28 clusters. It is the first time that silicon has been successfully introduced in the Ge10 cluster in significant amounts ( approximately 21% of the tetrahedral sites). Five- and six-coordinated Ge10 clusters have previously been observed in other germanate compounds leading to either dense or open structures. In SU-61, the seven-coordinated clusters fall onto yet another underlying net, the osf net. SU-61, along with other Ge10 based frameworks, shows the versatility of the germanate system to adopt defined topologies playing on the connectivity of the clusters following the principles of net decoration and scale chemistry.

Preparation and characterization of Si modified Ge9 cluster

“…The longer bond lengths and smaller bond angles found in square pyramidal and octahedral coordination are easier to break during heat treatment. Reported silicogermanates, such as SU-61 ((Ge,Si) 10 (O,OH) 28 ) [4] and ICMM7 [17] are stable up to 250 °C. …”

Si modified Ge10 cluster: the preparation and characterization of single crystal Na4(Ge,Si)9O20

“…Each tetrahedra is linked to two octahedra of the same tetrameric unit, giving rise to www.crt-journal.org © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim the formation of 3-rings. A unit consisting of such a tetramer and 6 tetrahedra is called a Ge 10 cluster or SBU-10 and has already been encountered in other materials [1,4,[10][11][12].…”

“…The Si-O distances (1.61 Å) are shorter than the Ge-O distances (1.76 Å) and the Ge-O-Ge angles are typically smaller (130°) than Si-O-Si angles [9], which leads to constrains in how much silicon that can be incorporated into a germanate framework. Ge 10 clusters with four GeO 6 octahedra and six GeO 4 tetrahedra can form 3D frameworks with a huge structural diversity [1,4,[10][11][12]. Among these germanates, so far, only SU-61 [4] was reported with Si at the tetrahedral sites.…”

“…Ge 10 clusters with four GeO 6 octahedra and six GeO 4 tetrahedra can form 3D frameworks with a huge structural diversity [1,4,[10][11][12]. Among these germanates, so far, only SU-61 [4] was reported with Si at the tetrahedral sites.…”

An unprecedented seven-connected coordination network based on octanuclear supertetrahedral lead(II) cluster as a secondary building unit

“…3c). To date, 7-connected nets are extremely rare in inorganic solids and metal-organic frameworks [27][28][29][30][31], the framework reported herein defines a new topology for 7-connected networks to the best of our knowledge [32].…”