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The Si-Ge substitutional series in the chiral STW Zeolite Structure Type


The whole compositional range (Ge f = Ge/(Ge+Si)= 0 to 1) of zeolite STW has been synthesized and studied by a comprehensive combined experimental–theoretical approach. The yield of zeolite goes through a maximum and then drops at the GeO 2 side of the series, following the inverse of the calculated free energy curve. The unit cell generally expands, roughly linearly, as the Ge f increases, but a notable resilience to expansion is observed at the high silica side. This can be attributed to the more rigid character of SiO2 and the ability of Ge units to deform. Density functional theory calculations provide a new assignment of the previously controversial 19 F MAS NMR resonances for occluded fluoride, which is based not only in the number of Ge atoms in the double-4-ring units but also on the way they are associated (namely, no Ge, isolated Ge, Ge pairs or closed Ge clusters). While we found an overall good agreement between the experimental and theoretical trends in preferential occupation by Ge of different crystallographic sites, the theoretical models show more sharp and abrupt tendencies, likely due both to limitations of the approach and to kinetic factors that allow metastable configurations to actually exist.

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Publication details

The article was received on 26 Apr 2018, accepted on 04 Jul 2018 and first published on 06 Jul 2018

Article type: Paper
DOI: 10.1039/C8TA03879A
Citation: J. Mater. Chem. A, 2018, Accepted Manuscript
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    The Si-Ge substitutional series in the chiral STW Zeolite Structure Type

    R. T. Rigo, S. Rodríguez-Gómez Balestra, S. Hamad, R. Bueno-Perez, A. R. Ruiz-Salvador, S. Calero and M. A. Camblor, J. Mater. Chem. A, 2018, Accepted Manuscript , DOI: 10.1039/C8TA03879A

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