Excellent ammonia sorption enabled by metal-organic framework nanocomposites for seasonal thermal battery

Solar-powered seasonal thermal battery(STB) is currently anticipated as a prospective future sustainable energy technology, for which prevailing the working pairs of activated carbon and halides-ammonia are proven low-adaptability in extreme conditions. Here we reveal that MOF-ammonia working pair occupying sorption active sites in the reaction process could significantly improve the effectiveness of thermal energy storage under severe ambient temperature. Furthermore, an innovative ammonia-based working pair is reported for STB enabled by in-situ growth of CaCl2@ZIF-8(Zn) composite with a high cyclic/real-time sorption capacity of 0.310/0.406 g∙g−1, which is increased by 43.52% compared with ZIF-8(Zn) under the extreme conditions because of strong host-guest interactions to induce coordination bond rearrangements between CaCl2 and ammonia. Based on MOF composites-ammonia working pairs, a proof-of-concept solar-powered STB is designed and tested. Even under severe condition with the evaporation temperature below 10°C, the gravimetric/volumetric heat storage densities and efficiency of STB can still achieve 401.66 kJ∙kg−1, 72.54 kWh∙m−3, and 85.30% due to strong physicochemical coupling sorption behavior. The method provides a transformative low-carbon route to upgrade low-grade energy for efficient thermal management.