As the effects of climate change become more apparent in the form of rising global temperatures, the necessity for temperature control become more significant. Current refrigerants are low cost and work extremely efficiently but these materials possess very high global warming potentials. A greener alternative is a solid-state approach via barocaloric materials which exhibit large adiabatic temperature and isothermal entropy changes upon compression and decompression cycles. Metal-organic frameworks (MOFs) are porous, crystalline materials that are highly modular due to the many metal and linker combinations possible. Notably, certain MOFs exhibit the breathing effect wherein the adsorption and desorption of guest molecules are accompanied by a large reversible volume change. From this, they have been recognised as potential barocaloric materials. Moreover, we have found orientational disorder in the linkers which result in conformational isomers that can tune the barocaloric performance of the frameworks. My research use ab initio molecular dynamics to further understand the effects of the conformational isomerism on the properties of the MIL-53-fum framework series. Grand canonical Monte Carlo simulations allow us to isolate, for the first time, the entropic contributions of guest adsorption from the volumetric or conformational aspects. This reveals the role of breathing MOFs in refrigeration applications and inform the design of functional materials.
Hong et al. (Thu,) studied this question.