Mechanical properties of a gallium fumarate metal–organic framework: a joint experimental-modelling exploration

Abstract

A gallium analogue of the commercially available Al-fumarate MOF A520 – recently identified as isotypic to MIL-53(Al)-BDC – has been synthesized for the first time and further characterized in its hydrated and dehydrated forms. The structural response under applied mechanical pressure of this MIL-53(Ga)-FA solid was investigated using advanced experimental techniques coupled with computational tools. Hg porosimetry and high-pressure X-ray powder diffraction (XRPD) experiments evidenced that the pristine dehydrated large pore form undergoes an irreversible structure contraction upon an applied pressure of 85 MPa with an associated volume change of ∼14% which makes this material promising for mechanical energy storage applications, in particular as a shock absorber. The breathing behavior was further rationalized by performing a series of periodic Density Functional Theory (DFT) calculations with the construction of an energy profile as a function of volume for both MIL-53(Ga)-FA and its aluminium analogue. As such we unravelled the microscopic origin of the difference in pressure-induced behavior for the aluminium and gallium fumarate based materials.