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Compositional Inhomogeneity and Tuneable Thermal Expansion in Mixed-Metal ZIF-8 Analogues

preprint
submitted on 25.05.2018 and posted on 25.05.2018 by Adam Sapnik, Harry Geddes, Emily Reynolds, Hamish Yeung, Andrew Goodwin
We study the structural and thermomechanical effects
of cation substitution in the compositional family of
metal–organic frameworks Zn1􀀀xCdx(mIm)2 (HmIm = 2-
methylimidazole). We find complete miscibility for all
compositions x, with evidence of inhomogeneous distributions of Cd and Zn that in turn affect framework aperture characteristics. Using variable-temperature X-ray powder diffraction measurements, we show that Cd substitution drives a threefold reduction in the magnitude of thermal expansion behaviour. We interpret this effect in terms of an increased density of negative thermal expansion modes in the more flexible Cd-rich frameworks.

History

Email Address of Submitting Author

andrew.goodwin@chem.ox.ac.uk

Institution

University of Oxford

Country

UK

ORCID For Submitting Author

0000-0001-9231-3749

Declaration of Conflict of Interest

No conflict of interest

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