Issue 10, 2016

Elucidating the mechanism responsible for anomalous thermal expansion in a metal–organic framework

Abstract

The previously reported anisotropic thermal expansion of a three-dimensional metal–organic framework (MOF) is examined by means of theoretical calculations. Inspection of the 100, 190, 280 and 370 K single crystal X-ray diffraction (SCD) structures indicated a concerted change in the coordination sphere of the zinc centre leading to elongation of the coordination helix in the crystallographic c direction (the Zn–O(H)–Zn angle expands), while the largely unaltered ligands (the Zn⋯L⋯Zn distance remains constant) are pulled closer together in the ab plane. This study develops and evaluates a mechanistic model at the DFT level of theory that reproduces the convergent expansion of the coordination helix of the material. The linear increase in energy calculated for extension of a model consisting of six zinc centres and truncated ligands compares favourably with results obtained from a periodic DFT evaluation of the SCD structures. It was also found that the anisotropic thermal expansion trend could be reproduced qualitatively by Molecular Dynamics (MD) simulations in the NPT ensemble.

Graphical abstract: Elucidating the mechanism responsible for anomalous thermal expansion in a metal–organic framework

Supplementary files

Article information

Article type
Paper
Submitted
22 Cax 2015
Accepted
03 Qad 2015
First published
06 Qad 2015

Dalton Trans., 2016,45, 4141-4149

Author version available

Elucidating the mechanism responsible for anomalous thermal expansion in a metal–organic framework

D. P. van Heerden, C. Esterhuysen and L. J. Barbour, Dalton Trans., 2016, 45, 4141 DOI: 10.1039/C5DT01927C

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