Magnetocaloric Effect in a Microporous Material Using a Rare-Earth-Free, Hybrid Perovskite

Magnetic refrigeration using the magnetocaloric effect (MCE), where the temperature of a material changes as a magnetic field is applied, is a promising technology to increase the energy efficiency of commodity gas liquefaction at cryogenic temperatures. Currently, the most commonly studied materials for this application utilize rare-earth elements in nonporous forms. The continued development of magnetocaloric materials could benefit from (1) the discovery of materials with high surface areas capable of condensing substantial quantities of gas using minimal energy inputs and (2) the use of cheap and abundant precursors instead of utilizing rare-earth metals. We show here that microporous copper-halide perovskites, which form a layered structure with accessible crystalline voids between copper-halide sheets, demonstrate large entropy changes upon applying a magnetic field at temperatures relevant for H₂ condensation. This is the first demonstration of the magnetocaloric effect for a transition-metal-based porous material. Furthermore, tuning the halide composition gives fundamental insight into how to control both the ferromagnetic transition temperature and the magnetic entropy change within this class of materials.