ECS-3's Complex Structure Solved

ECS-3's Complex Structure Solved

Author: ChemViews

The synthesis of aluminosilicate hybrids with organic groups fused within a crystalline framework is a daunting mission, but hybrids add variable chemical modification to the repertoire of zeolites, which are well established as heterogeneous catalysts, ion exchangers, and molecular sieves with many different pore architectures. A breakthrough in the synthesis of crystalline aluminosilica-based hybrid organic–inorganic porous materials occurred in 2008 with the advent of ECS (eni carbon silicates).

ECS-2, prepared with 1,4-bis(triethoxysilyl)benzene, was the first structure to be resolved. It consists of a regular stacking of aluminosilicate and organic layers, the latter made up of phenylene groups covalently bound to the Si atoms of adjacent inorganic layers. Formally, ECS-2 can be classified as clathrasil-like, since the arrangement of the phenylene rings generates large cages disconnected from the exterior.

Stefano Zanardi, eni s.p.a.—Refining & Marketing Division, San Donato Milanese, Italy, and colleagues report the structure of another ECS: They used automated diffraction tomography (ADT) to collect electron-diffraction data for solving the crystal structure of ECS-3. This is the first example of a crystalline hybrid organic–inorganic aluminosilicate with open porosity, generated by a regular arrangement of phenylene rings interconnecting aluminosilicate layers and one of the most complex structures ever solved by electron diffraction.

Regular arrangement of phenylene rings interconnecting aluminosilicate layers: Al turquoise, C gray, O red, Si gold. ©: Wiley-VCH.

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