Extreme barocaloric effect at dissolution

Refrigeration is indispensable to modern society¹, yet the dominant vapour-compression systems rely on environmentally harmful fluorocarbon refrigerants with high global warming potential^2-4. Solid-state caloric refrigeration offers a low-carbon alternative^5-7, but its practical deployment has been hindered by limited cooling capacity and the inefficient indirect heat transfer that requires secondary fluids. Here we report an extreme barocaloric effect in NH₄SCN aqueous solutions enabled by pressure-tuned dissolution and precipitation. This mechanism delivers an exceptionally large cooling capacity and markedly enhanced cooling efficiency. We obtain an in situ temperature drop of 26.8 K in the solution at room temperature, surpassing all known caloric materials. A Carnot-like cycle is designed to deliver 67 J g^-1 cooling capacity per cycle with a second-law efficiency of 77%, benefiting from the extremely large temperature drops and direct heat transfer due to the self-circulating aqueous solution. Beyond the phase-transition scenario, this dissolution-based approach that combines the merits of current leading technologies emerges as a promising sustainable refrigeration solution.