A Wide-Bandgap Molecular Ferroelectric Semiconductor with a Two-Step Wide-Temperature Second Harmonic Generation Response: [FMeQ] ₂ ZnI ₄

Wide-bandgap molecular ferroelectric semiconductors are emerging as critical candidates for next-generation multifunctional optoelectronics, yet integrating robust ferroelectricity with a wide optical bandgap remains a formidable challenge. Herein, we report a zero-dimensional organic–inorganic hybrid ferroelectric semiconductor, [FMeQ] 2 ZnI 4 (FMeQ = N -fluoromethyl-quinuclidine), constructed via a targeted cation fluorination strategy. This compound crystallizes in the polar orthorhombic space group Pna 2 1 and exhibits a wide indirect bandgap of approximately 3.65 eV, comparable to traditional inorganic semiconductors like GaN. Remarkably, [FMeQ] 2 ZnI 4 undergoes two sequential reversible order–disorder phase transitions at 306 and 336 K, endowing the material with a unique two-step switchable second harmonic generation (SHG) response over a wide temperature range. Electronic structure analysis reveals an effective decoupling mechanism where the inorganic [ZnI 4 ] 2– anion dominates the wide bandgap, while the dynamic organic cation dictates the ferroelectricity. This discovery provides an alternative approach to explore wide-bandgap molecular ferroelectrics, especially ferroelectric semiconductors with high-performance multistate optical switching capabilities.