A five- and six-coordinated two-dimensional metal halide organic–inorganic phase transition material

Two-dimensional organic-inorganic hybrid metal halides (2D OIHMHs) have attracted extensive attention due to their diverse functionalities, but most of them form layered structures with only six-coordinate geometry. Herein, we report a novel 2D OIHMH phase transition material, (<i>N</i>,<i>N</i>'-diisopropylethylammonium) tricadmium heptachloride, which contains Cd²⁺ ions with both five- and six-coordinate configurations, forming a rarely seen 2D structure. In addition, it exhibits an isostructural phase transition at 263 K and a large optical bandgap of 5.53 eV.