Precise Molecular Design Toward Organic–Inorganic Zinc Chloride ABX3 Ferroelectrics

Organic-inorganic ABX3 (A, B = cations, X = anion) hybrids with perovskite structure have recently attracted tremendous interest due to their structural tunability and rich functional properties, such as ferroelectricity. However, ABX3 hybrid ferroelectrics with other structures have rarely been reported. Here, we successfully designed an ABX3 hybrid ferroelectric [(CH3)3NCH2F]ZnCl3 with a spontaneous polarization of 4.8 μC/cm2 by the molecular modification of [(CH3)4N]ZnCl3 through hydrogen/halogen substitution. It is the first zinc halide ABX3 ferroelectric, which contains one-dimensional [ZnCl3]-n chains of corner-sharing ZnCl4 tetrahedra, distinct from the anionic framework of corner-sharing or face-sharing BX6 octahedra in the ABX3 perovskites. From zero dimension to one dimension, the high symmetry of ZnCl4 tetrahedra is broken, and all of them align along one direction to form a polar [ZnCl3]-n chain, beneficial to the generation of ferroelectricity. This finding provides an efficient polar anionic framework for enriching the family of hybrid ferroelectrics by assembling with various cations and should inspire further exploration of new classes of organic-inorganic ABX3 ferroelectrics.