title: Extreme compressibility in LnFe(CN)6 coordination framework materials via molecular gears and torsion springs.
abstract: The mechanical flexibility of coordination frameworks can lead to a range of highly anomalous structural behaviours. Here, we demonstrate the extreme compressibility of the LnFe(CN)6 frameworks (Ln = Ho, Lu or Y), which reversibly compress by 20% in volume under the relatively low pressure of 1 GPa, one of the largest known pressure responses for any crystalline material. We delineate in detail the mechanism for this high compressibility, where the LnN6 units act like torsion springs synchronized by rigid Fe(CN)6 units performing the role of gears. The materials also show significant negative linear compressibility via a cam-like effect. The torsional mechanism is fundamentally distinct from the deformation mechanisms prevalent in other flexible solids and relies on competition between locally unstable metal coordination geometries and the constraints of the framework connectivity, a discovery that has implications for the strategic design of new materials with exceptional mechanical properties.
authors.affiliation: School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia.|Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia.
authors.forename: Samuel G
authors.identifier: http://orcid.org/0000-0002-5380-9204
authors.initials: SG
authors.lastname: Duyker
authors.affiliation: Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia.
authors.forename: Vanessa K
authors.initials: VK
authors.lastname: Peterson
authors.affiliation: Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia.
authors.forename: Gordon J
authors.initials: GJ
authors.lastname: Kearley
authors.affiliation: Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Studer
authors.affiliation: School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia.
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Kepert