Multiple non-covalent interactions synergistically construct <?A3B2 pi6?>room-temperature photoferroelectric semiconductor (Cl-PA)₂PbCl₄

Non-covalent interactions play an indispensable role in the construction of molecular ferroelectrics, as they can regulate the relative orientation and stacking mode between molecules. However, the difficulty and challenge lie in precisely designing and regulating the weak intermolecular interactions, ultimately generating macroscopically reversible spontaneous polarization through synergistic effects, thereby achieving ferroelectricity. Herein, we introduced halogenated ammonium Cl-PA+ (Cl-PA+ is 3-chloropropylaminium) to regulate non-covalent interactions in the structure of hybrid perovskite, and constructed a photoferroelectric semiconductor (Cl-PA)2PbCl4 with large piezoelectric coefficient (d33 = 27.4 pC/N) and high Curie temperature (Tc = 353 K) through the synergistic effect of hydrogen bonding and halogen-halogen interactions. Compared with non-ferroelectric (PA)2PbCl4 (PA+ is n-propylaminium), the severe distortion of PbCl6 octahedra, weakened N–H···Cl hydrogen bond between organic cations and inorganic frameworks, enhanced C–H···Cl hydrogen bond between cations, and the additional Cl···Cl interaction in the structure synergistically induce the ferroelectricity of (Cl-PA)2PbCl4. In addition, the large dipole moment of Cl-PA is also beneficial for constructing molecular ferroelectrics, and the synergetic effect of non-covalent interactions in (Cl-PA)2PbCl4 provides the possibility for dipole flipping and symmetry breaking. Therefore, constructing molecular ferroelectrics through the synergistic effect of non-covalent interactions essentially utilizes dynamic coupling and precise equilibrium of multiple weak interactions to achieve the formation, stability, and external field flipping of spontaneous polarization. Through this collaborative design, ferroelectrics with high spontaneous polarization (Ps), low coercive field, and wide temperature range can be achieved, which opens up new directions for flexible electronics and energy storage.非共价相互作用（Non-covalent interactions）在分子铁电体（molecular ferroelectrics）的构建中发挥着不可或缺的作用，因其可调控分子间的相对取向与堆积模式。然而，精准设计并调控弱分子间相互作用，最终通过协同效应实现宏观可逆自发极化（spontaneous polarization）以获得铁电性，仍是该领域的难点与挑战。于此研究中，我们引入卤化铵Cl-PA+（Cl-PA+为3-氯丙胺阳离子）来调控杂化钙钛矿（hybrid perovskite）结构中的非共价相互作用，并通过氢键（hydrogen bond）与卤-卤相互作用（halogen-halogen interactions）的协同效应，构建出兼具大压电系数（piezoelectric coefficient, d33 = 27.4 pC/N）与高居里温度（Curie temperature, Tc = 353 K）的光铁电半导体(Cl-PA)2PbCl4。相较于非铁电材料(PA)2PbCl4（PA+为正丙胺阳离子），(Cl-PA)2PbCl4的结构中存在PbCl6八面体严重畸变、有机阳离子与无机骨架间的N–H···Cl氢键减弱、阳离子间C–H···Cl氢键增强，以及额外的Cl···Cl相互作用，这些因素协同诱导了该材料的铁电性。此外，Cl-PA拥有较大的偶极矩（dipole moment），这也有助于构建分子铁电体；而(Cl-PA)2PbCl4中非共价相互作用的协同效应，为偶极翻转与对称性破缺（symmetry breaking）提供了可能。因此，通过非共价相互作用的协同效应构建分子铁电体，本质上是利用多重弱相互作用的动态耦合与精准平衡，实现自发极化的形成、稳定与外场翻转。通过该协同设计策略，可获得具有高自发极化（spontaneous polarization, Ps）、低矫顽场（coercive field）与宽温度适用范围的铁电材料，为柔性电子与储能领域开辟了全新方向。