Gas-Responsive Metal-Organic Frameworks for Adaptive Thermal Energy Storage with Tunable Charge-Discharge...

One of the major challenges for thermal energy storage (TES) systems based on phase change materials (PCMs)─a key technology for energy decarbonization─is achieving dynamical tunability of their charge and discharge temperatures (Tcharge, Tdischarge). This capability would enable a single material to operate effectively across varying ambient conditions (e.g., different times of day, seasons, or climates) without requiring the use of multiple TES materials. In this work, we present a gas-responsive TES solution based on breathing caloric MOFs, particularly MOF-508b, in which transition temperatures can be widely tuned from -30 to 120 °C (243 to 393 K) by adjusting the surrounding CO2 pressure from 5 to 25 bar under isobaric conditions. More importantly, we demonstrate that this method allows precise control over the thermal hysteresis (|Tcharge - Tdischarge|) and can even reverse the transition temperatures (Tcharge < Tdischarge), which could be highly advantageous for temperature-driven TES applications. These findings pave the way for adaptive thermal technologies in which a single material can respond to different ambient temperatures and diverse storage needs, from cold storage to medium-high-temperature applications. We anticipate that this gas-responsive behavior is not exclusive to MOF-508b and encourage the exploration of other materials exhibiting similar tunable characteristics for adaptive TES applications.