Barocaloric Effects from Hydrocarbon Order–Disorder Transitions

Efficient barocaloric cooling requires materials that undergo reversible phase transitions with large entropy changes, high sensitivity to hydrostatic pressure, and minimal hysteresis—the combination of which has been challenging to achieve in existing barocaloric materials. Here, I will describe how hydrocarbon order-disorder phase transitions in organic and metal–organic materials can be manipulated to induce large, reversible barocaloric effects at moderate pressures. In particular, I will discuss the structural and chemical factors that contribute to entropy changes, sensitivity to hydrostatic pressure, and hysteresis for two classes of layered materials that undergo structural transitions associated with the disordering of hydrocarbon bilayers. Additionally, I will highlight the important role the pressure-transmitting medium plays in directing these barocaloric effects.