A Three-Dimensional Organic-Inorganic Hybrid Perovskite-Type Molecular Ferroelectric Material [3.2.2-H₂dabcn]Rb(NO₃)₃

Replacing halide ions with nitrate ions to construct hybrid molecular ferroelectrics provides a new strategy for optimizing the properties of ferroelectric materials. In this work, an organic-inorganic hybrid ferroelectric crystal [3.2.2-H₂dabcn]Rb(NO₃)₃ (1) is successfully synthesized by reacting the spherical molecule 1,5-diazabicyclic[3.2.2]nonane with RbNO₃ in a 1:1 molar ratio in dilute nitric acid solution. The compound exhibits a phase transition above room temperature (317 K), accompanied by a pronounced step-like dielectric anomaly and reversible nonlinear optical switching behavior. Single-crystal structure analysis reveals that, before the phase transition, compound 1 crystallizes in the polar space group Pca2₁. The room-temperature P-E hysteresis loop demonstrates macroscopic polarization and a saturation polarization value of 8.14 μC/cm² for 1. Piezoelectric force microscopy visually reveals multidomain structures and 180° antiparallel ferroelectric domains on the polycrystalline films of 1. Furthermore, the amplitude-dependent butterfly curve indicates a coercive voltage of approximately 20 V. This lead-free hybrid perovskite ferroelectric material shows promising potential for applications in smart wearable devices and flexible electronics.