(3-CF3pyH)2(3-CF3py)Pb3I8: A Three-Dimensional Metal Halide Inorganic Framework with Distinctive Kagomé Bands

The structural diversity inherent in hybrid organic–inorganic metal halides as a function of the organic cation template can give access to numerous semiconducting materials featuring distinct polyhedral connectivity patterns. Beyond the common corner-sharing pattern of halide perovskites, different motifs can be accessed via the use of bulky and asymmetric templates, which can break the corner-sharing pattern. In this work, we report on the synthesis and characterization of a novel three-dimensional hybrid metal halide network, (3-CF₃pyH)₂(3-CF₃py)Pb₃I₈, featuring a buckled decorated honeycomb lattice arising from the corner-connected arrangement of [Pb₃I₈]^2– clusters. The compound is an indirect bandgap semiconductor with a bandgap of E_g = 2.6 eV that exhibits photoluminescence via a trap-assisted mechanism at 77 K. The inorganic cluster topology governs the electronic properties of the material, whereas the perovskite-like corner connectivity of the clusters gives rise to dispersive bands along certain crystallographic directions. The unprecedented appearance of distinctive Kagomé bands, emerging in the DFT calculated band structure of the idealized crystal structure, renders this material a promising candidate for advanced optoelectronic applications.