Framework Modifications and Dehydration Path of a Ag+-Modified Zeolite with STI Framework Type

Cametti, Georgia; Scheinost, Andreas C.; Giordani, Matteo; Churakov, Sergey V. (2019). Framework Modifications and Dehydration Path of a Ag+-Modified Zeolite with STI Framework Type. Journal of physical chemistry. C, 123(22), pp. 13651-13663. American Chemical Society 10.1021/acs.jpcc.9b01976

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The effect of Ag+ incorporation into stellerite, a natural zeolite with STI framework type, was investigated by means of Single Crystal X-ray Diffraction (SC-XRD), Molecular Dynamics (MD) simulations and X-ray Absorption Fine Structure Spectroscopy (XAFS). At room temperature the complete exchange of the original extraframework ions with Ag+ provoked a distortion of the framework accompanied by symmetry reduction from orthorhombic Fmmm to monoclinic F2/m space group. Ag+ ions were strongly disordered, with occupancies ranging from 0.02 to 0.24, at partially-occupied sites within zeolitic cages. The combination of ab initio molecular dynamic simulations and XAFS spectroscopy suggested that Ag+ is coordinated by three H2O oxygen at 2.37 Å and by two framework oxygen atoms between 2.55 and 3.00 Å. The thermal stability was monitored in situ by SC-XRD (from 25 to 400°C) and by XAFS (from 25 to 650°C). Upon heating the structure transformed to three different topologies: B phase, D’ phase, observed here for the first time, and D phase. The unit-cell volume contracted from 4392.85(14) at room temperature to 3644.4(4) Å3, measured at 400°C. Possible Ag+ to Ag0 reduction could be excluded although the formation of Ag+-Ag+ clusters could not be unambiguously ruled out.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Cametti, Georgia; Giordani, Matteo and Churakov, Sergey

Subjects:

500 Science > 540 Chemistry
500 Science > 550 Earth sciences & geology

ISSN:

1932-7447

Publisher:

American Chemical Society

Language:

English

Submitter:

Georgia Cametti

Date Deposited:

10 Mar 2021 09:41

Last Modified:

10 Mar 2021 09:50

Publisher DOI:

10.1021/acs.jpcc.9b01976

BORIS DOI:

10.48350/152637

URI:

https://boris.unibe.ch/id/eprint/152637

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