Metal–organic phase-change materials for thermal energy storage | Poster Board #2531

With most of the primary energy generation in the USA being thermal in nature and the majority of energy being wasted thermally, developing materials to reversibly store thermal energy is critical to more efficiently using and managing thermal energy. Owing to their tunability, metal–organic phase-change materials based on molecular coordination complexes offer an opportunity to expand the library of existing phase-change materials for thermal energy storage and further establish fundamental structure-property relationships to design energy-dense thermal energy storage materials. Here, we will report an isostructural series of divalent metal amide complexes featuring expanded hydrogen bond networks that undergo tunable, high-enthalpy melting transitions over a wide temperature range. Using a combination of solid-state and liquid-state structural and thermal characterization techniques, we elucidate the structural and chemical factors that influence phase change thermodynamics. Importantly, we find that these amide-based metal–organic phase-change materials feature similar volumetric energy densities to metal-salt hydrates, despite the metal-salt hydrates having higher volumetric hydrogen bond densities. To investigate the influence of non-hydrogen bond contributions to melting thermodynamics in metal-organic materials, we investigated metal-organic systems that lack hydrogen bond donors and acceptors but maintain a high volumetric density of metal-ligand coordination bonds and outer sphere metal-counteranion electrostatic interactions.