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Compositional dependence of anomalous thermal expansion in perovskite-like ABX3 formates
Ines E Collings1, Joshua A Hill2, Andrew B Cairns2
1Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK. andrew.goodwin@chem.ox.ac.uk and Laboratory of Crystallography, University of Bayreuth, D-95440 Bayreuth, Germany.
Abstract:
The compositional dependence of thermal expansion behaviour in 19 different perovskite-like metal-organic frameworks (MOFs) of composition [A(I)][M(II)(HCOO)3] (A = alkylammonium cation; M = octahedrally-coordinated divalent metal) is studied using variable-temperature X-ray powder diffraction measurements. While all systems show essentially the same type of thermomechanical response-irrespective of their particular structural details-the magnitude of this response is shown to be a function of A(I) and M(II) cation radii, as well as the molecular anisotropy of A(I). Flexibility is maximised for large M(II) and small A(I), while the shape of A(I) has implications for the direction of framework hingeing.
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