Three-Dimensional Metal-Free Molecular Perovskite with a Thermally Induced Switchable Dielectric Response

Temperature-responsive materials with switching physical properties have been widely researched. Among them, the switchable dielectric perovskite materials show potential applications in the electrical and electronic industries and even the intelligence industries. However, perovskite oxides and hybrid organic–inorganic perovskites, as the most representative switchable dielectric materials, are limited by bad biocompatibility. Herein, we report temperature-dielectric-responsive metal-free perovskite (H₂dabco)­(NH₄)­[BF₄]₃ constructed by the strategy of substituting the B site in the general formula ABX₃ (doubly protonated 1,4-diazabicyclo[2.2.2]­octane = H₂dabco). Meanwhile, structurally similar hybrid material (H₂dabco)­Rb­[BF₄]₃ was designed as a control. They exhibit similar phase-transition characteristics and dielectric response behaviors around 333 K. More interestingly, the ordered–disordered transformation of their organic “spherical” cations (H₂dabco) was deemed to produce their phase transitions and dielectric response switching. Given its ability to generate a dielectric response, (H₂dabco)­(NH₄)­[BF₄]₃ will show the potential application of metal-free perovskite in a future thermal sensing device.