Confinement in Metal‐Organic Frameworks as a Route to Harnessing Liquid Barocalorics in the Solid‐State

ABSTRACT Barocaloric (BC) effects at liquid–vapor transitions in hydrofluorocarbons drive most commercial technologies used for heating and cooling in the heating, ventilation and air‐conditioning sector. However, these fluids suffer from huge global warming potential and alternative gases are less efficient, toxic or flammable. Solid–solid and solid–liquid BC materials have zero global warming potential and could even improve on current device efficiencies. Whilst solid–liquid BCs typically outperform solid–solid BCs, the latter are advantageous as they avoid leaks and present easier handling and recyclability thus facilitating waste management. Here we confine the solid–liquid BC stearic acid inside the nanopores of a functionalized metal‐organic framework (MOF) and demonstrate that the colossal BC properties are retained in a solid‐state material. Moreover, the enhanced interactions between the pore surface and the BC material allow a level of active control over the thermal response, as opposed to passive encapsulation. Our results open novel avenues to exploit and tune colossal BC effects in a wide range of combinations of solid–liquid BC materials embedded within functionalized MOFs, without the associated engineering drawbacks.