Mixed-Ligand Engineering of Manganese Perovskite-like Materials with Tunable Solid−Solid Phase Transitions

High Resolution Image Download MS PowerPoint Slide The rational design of novel materials capable of reversible solid-state phase transitions is a central challenge in modern materials science, owing to their potential in thermal regulation and energy storage. Hybrid organic−inorganic perovskites (HOIPs) have emerged as promising candidates due to their pronounced and reversible entropy changes near room temperature. In this work, we explore a mixed-ligand strategy employing azide and formate linkers to systematically tailor the structural and thermal properties of a manganese-based perovskite-like framework ([TMA][Mn(N 3 ) 3 ]). The azide ligand imparts structural flexibility and dynamic behavior, while formate contributes stability and structural diversity. By varying the azide-to-formate ratio (at low concentrations), we achieved controlled tuning of phase transition temperatures and enthalpy/entropy responses, with transitions occurring near ambient conditions. Importantly, ligand substitution also induces broadened multi-step thermal transitions correlated with monoclinic−cubic phase coexistence revealed by XRPD analysis. Our findings reveal that mixed-ligand design not only enables modulation of thermal properties and phase behavior but also expands the structural landscape accessible to HOIPs, highlighting their potential as solid-state phase change materials for energy-efficient technologies. This study underscores the versatility of combinatorial ligand approaches for engineering functional materials with customizable thermodynamic responses.