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© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.

Abstract

The roles of organic additives in the assembly and crystallisation of zeolites are still not fully understood. This is important when attempting to prepare novel frameworks to produce new zeolites. We consider 18-crown-6 ether (18C6) as an additive, which has previously been shown to differentiate between the zeolite EMC-2 (EMT) and faujasite (FAU) frameworks. However, it is unclear whether this distinction is dictated by influences on the metastable free-energy landscape or geometric templating. Using high-pressure synchrotron X-ray diffraction, we have observed that the presence of 18C6 does not impact the EMT framework flexibility—agreeing with our previous geometric simulations and suggesting that 18C6 does not behave as a geometric template. This was further studied by computational modelling using solid-state density-functional theory and lattice dynamics calculations. It is shown that the lattice energy of FAU is lower than EMT, but is strongly impacted by the presence of solvent/guest molecules in the framework. Furthermore, the EMT topology possesses a greater vibrational entropy and is stabilised by free energy at a finite temperature. Overall, these findings demonstrate that the role of the 18C6 additive is to influence the free energy of crystallisation to assemble the EMT framework as opposed to FAU.

Details

Title
Intrinsic Flexibility of the EMT Zeolite Framework under Pressure
Author
Nearchou, Antony 1 ; Cornelius, Mero-Lee U 2 ; Skelton, Jonathan M 3   VIAFID ORCID Logo  ; Jones, Zöe L 1 ; Cairns, Andrew B 4   VIAFID ORCID Logo  ; Collings, Ines E 5   VIAFID ORCID Logo  ; Raithby, Paul R 1   VIAFID ORCID Logo  ; Wells, Stephen A 6 ; Asel Sartbaeva 1   VIAFID ORCID Logo 

 Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK 
 Department of Chemistry, University of the Western Cape, Bellville, Cape Town 7535, South Africa 
 Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK; School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK 
 Department of Materials, Imperial College London, Kensington, London SW7 2AZ, UK 
 European Synchrotron Radiation Facility, 71 avenue des Martyrs, 38000 Grenoble, France 
 Department of Chemical Engineering, University of Bath, Claverton Down, Bath BA2 7AY, UK 
First page
641
Publication year
2019
Publication date
2019
Publisher
MDPI AG
e-ISSN
14203049
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
2548936524
Copyright
© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.