H/CH3 Organic-Cation Substitution Regulates Structural Evolution toward High-Tc Ferroelectricity and Enhanced Blue Emission in Gallium-Based Organic-Inorganic Hybrids.

Single-component luminescent molecular ferroelectrics provide a promising platform for next-generation multifunctional optoelectronics, yet developing a single material that combines a high Curie temperature with efficient light emission remains challenging. Herein, we employed a comparative organic-cation substitution strategy involving H/CH3 variation to construct a series of single-component organic-inorganic gallium chloride hybrids. Across the composition series, the room-temperature structures show a progression from centrosymmetric to noncentrosymmetric but nonpolar, and finally to polar R3m symmetry. Within this progression, [4-NH2PyH][GaCl4] emerges as the polar member. This compound exhibits room-temperature switchable polarization and undergoes a reversible first-order ferroelectric transition with a high Tc of 432 K. Concurrently, the blue-emission photoluminescence quantum yield (PLQY) increases from 0.68% to 19.9%, accompanied by a substantial increase in the apparent radiative decay-rate constant. This optical enhancement is associated with the composition-dependent reorganization of molecular packing and local coordination geometry. These findings demonstrate that tailored organic-cation substitution provides an effective molecular-design strategy for developing high-performance materials that combine high-Tc ferroelectricity with efficient light emission.