A Molecular Perovskite with Switchable Coordination Bonds for High-Temperature Multiaxial Ferroelectrics

The underlying phase transitions of ferroelectric mechanisms in molecular crystals are mainly limited to order–disorder and displacive types that are not involved in breaking of the chemical bonds. Here, we show that the bond-switching transition under ambient pressure is designable in molecular crystals, and demonstrate how to utilize the weaker and switchable coordination bonds in a novel molecular perovskite, [(CH₃)₃NOH]₂[KFe­(CN)₆] (TMC-1), to afford a scarce multiaxial ferroelectrics with a high Curie temperature of 402 K and 24 equivalent ferroelectric directions (more than BaTiO₃). The high-quality thin films of TMC-1 can be easily fabricated by a simple solution process, and to reveal perfect ferroelectric properties at both macroscopic and microscopic scales, suggesting TMC-1 as a promising candidate for applications in next-generation flexible electronics. The presented molecular assembly strategy, together with the achieved bond-switching ferroelectric mechanism, opens a new avenue for designing advanced ferroelectric materials.