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

25 May 2018, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

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.

Keywords

Metal Organic Framework
disorder
Thermal Expansion Behavior
Cation Ordering

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