Binary Phase Diagrams of Coordination Polymers with Eutectic Behaviors

We demonstrated the construction of binary phase diagrams of coordination polymer crystals by using their reversible solid-liquid transition (melting and crystallization) behaviors. Three types of binary phase diagrams of Ag⁺-based coordination polymers were made and the origins of each diagram formation were investigated. All diagrams showed eutectic phenomena induced by ligand exchange reactions at the interface of the two constituents. Solid solution formation was observed when we used two crystals with similar structures and coordination geometries, and the reaction was driven by both the anion and ligand exchange processes. The optimal binary compounds found in the phase diagrams were applicable as a latent heat storage material working at 100 °C with high energy recovery efficiency, stability in phase-transition cycles, and large hysteresis of melting/crystallization.