Preparation and characterization of Si modified Ge₉ cluster

Abstract

Open-framework germanates show interesting pore structures due to their flexible building units. Germanates with different topology built from the Ge 9 cluster can be prepared in several amine systems. This paper reports, the Si modified germanate ICMM6 (denoted as HUT-2) prepared in ethylene diamine solution through a hydrothermal synthesis route. HUT-2 is a silicogermanate with space group C222 1 (a=12.1299(6) Å, b=13.9329(11) Å, c=14.2205(6) Å, V=2403.33(25) Å 3 ) formed by the Si modified Ge 9 cluster. A variation of unit cell parameters is observed that is in accordance with Si-content. Powder X-ray diffraction, ICP and TGA-DSC analysis were recorded to determine the Si-composition at the tetrahedral sites. Structure refinements against the X-ray powder diffraction (XRPD) pattern determined the occupancy of Si at the two tetrahedral sites. An approximate Si/Ge ratio of 0.13-0.18 is obtained based on these characterizations. TGA-DSC analysis showed obvious weight loss of amine at 315 °C, which is higher than the reported pure germanate ICMM6. This further confirms the existence of Si within the structure of HUT-2.

Germanate with Three-Dimensional 12 × 12 × 11-Ring Channels Solved by X-ray Powder Diffraction with Charge-Flipping Algorithm

“…Since these properties strongly depend on the channel system of the framework structure, much effort has been made to explore open-framework materials with novel structures in the past decades . Open-framework germanates are of particular interest for their ability to form diverse structures, especially structures with an extralarge pore. − In contrast to silicate-based zeolite materials that contain only tetrahedral primary building units, open-framework germanates can be constructed from a variety of Ge-centered coordination polyhedra including Ge-centered tetrahedra, trigonal bipyramids, and octahedra. Combination of these flexible coordination modes of the Ge atom leads to formation of some well-defined clusters including Ge 7 X 19 (Ge 7 ), Ge 8 X 20 (Ge 8 ), Ge 9 X 25–26 (Ge 9 ), ,, Ge 10 X 28 (Ge 10 ), and Ni@Ge 14 clusters, where X = O, OH, or F. These large cluster building units can then be linked to each other by sharing O atoms or through additional primary building units, for instance, GeO 4 tetrahedra to form a variety of open-framework structures with large pores, as predicted by Férey on the basis of the concept of “scale chemistry” .…”

“…Open-framework germanates are of particular interest for their ability to form diverse structures, especially structures with an extralarge pore. − In contrast to silicate-based zeolite materials that contain only tetrahedral primary building units, open-framework germanates can be constructed from a variety of Ge-centered coordination polyhedra including Ge-centered tetrahedra, trigonal bipyramids, and octahedra. Combination of these flexible coordination modes of the Ge atom leads to formation of some well-defined clusters including Ge 7 X 19 (Ge 7 ), Ge 8 X 20 (Ge 8 ), Ge 9 X 25–26 (Ge 9 ), ,, Ge 10 X 28 (Ge 10 ), and Ni@Ge 14 clusters, where X = O, OH, or F. These large cluster building units can then be linked to each other by sharing O atoms or through additional primary building units, for instance, GeO 4 tetrahedra to form a variety of open-framework structures with large pores, as predicted by Férey on the basis of the concept of “scale chemistry” . For example, ASU-16 and SU-12 with 24-ring channels are built of Ge 7 and (Ge,Si) 7 clusters, respectively; FDU-4 with 24-ring channels is built of Ge 9 clusters; SU-M with mesoporous 30-ring channels is built of Ge 10 clusters; JLG-12 with mesoporous 30-ring channels is built of the combination of Ge 7 and Ge 9 clusters; FJ-1 with 24-ring channels is built of Ni@Ge 14 clusters.…”