Fluorine Substitution Induced High <i>T</i>_c of Enantiomeric Perovskite Ferroelectrics: (<i>R</i>)<i>-</i> and (<i>S</i>)<i>-</i>3‑(Fluoro­pyrrolidinium)MnCl₃

The past decade has witnessed much progress in designing molecular ferroelectrics, whose intrinsic mechanical flexibility, structural tunability, and easy processability are desirable for next-generation flexible and wearable electronic devices. However, an obstacle in expanding their promising applications in nonvolatile memory elements, capacitors, and sensors is effectively modulating the Curie temperature (Tc). Here, taking advantage of fluorine substitution on the reported molecular ferroelectric, (pyrrolidinium)­MnCl3, we present enantiomeric perovskite ferroelectrics, namely, (R)- and (S)-3-(fluoro­pyrrolidinium)­MnCl3. The close van der Waal’s radii and the similar steric parameters between H and F atoms ensure the minimum disruption of the crystal structure, while their different electronegativity and polarizability can trigger significant changes in the physical and chemical properties. As expected, the Tc gets successfully increased from 295 K in (pyrrolidinium)­MnCl3 to 333 K in these two homochiral compounds. Such a dramatic enhancement of 38 K signifies an important step toward designing high-Tc molecular ferroelectrics. In the light of the conceptually new idea of fluorine substitution, one could look forward to a continuous succession of new molecular ferroelectric materials and technology developments.过去十年间，分子铁电体（molecular ferroelectrics）的设计研发取得了长足进展。这类材料凭借固有机械柔性、结构可调性与易加工性，成为下一代柔性可穿戴电子器件的理想候选材料。然而，其在非易失性存储元件、电容器及传感器领域的应用拓展仍存在核心阻碍：如何有效调控居里温度（Curie temperature, Tc）。 本研究以已报道的分子铁电体（吡咯烷鎓）MnCl₃为研究对象，通过氟取代策略，成功制备出对映异构钙钛矿铁电体，即(R)-和(S)-3-氟吡咯烷鎓MnCl₃。氢原子与氟原子相近的范德华半径及相似的空间位阻参数，可将对晶体结构的扰动降至最低；而二者迥异的电负性与极化率，则能引发物理与化学性质的显著变化。 正如预期，这两种同手性化合物的居里温度成功从（吡咯烷鎓）MnCl₃的295 K提升至333 K，38 K的大幅增幅标志着高Tc分子铁电体的设计研发迈出了重要一步。基于这一概念新颖的氟取代策略，未来有望持续涌现新型分子铁电材料与相关技术发展成果。