Multicolor ultralong phosphorescence from perovskite-like octahedral α-AlF3

Designing organic fluorescent and phosphorescent materials based on various core fluorophore has gained great attention, but it is unclear whether similar luminescent units exist for inorganic materials. Inspired by the BX6 octahedral structure of luminescent metal halide perovskites (MHP), here we propose that the BX6 octahedron may be a core structure for luminescent inorganic materials. In this regard, excitation-dependent color-tunable phosphorescence is discovered from alpha-AlF3 featuring AlF6 octahedron. Through further exploration of the BX6 unit by altering the dimension and changing the center metal (B) and ligand (X), luminescence from KAlF4, (NH4)(3)AlF6, AlCl3, Al(OH)(3), Ga2O3, InCl3, and CdCl2 are also discovered. The phosphorescence of alpha-AlF3 can be ascribed to clusterization-triggered emission, i.e., weak through space interaction of the n electrons of F atoms bring close proximity in the AlF6 octahedra (inter/intra). These discoveries will deepen the understanding and contribute to further development of BX6 octahedron-based luminescent materials. Unravelling the origin of emission in luminescent inorganic materials is challenging. Here, the authors report that AlF6 octahedrons exhibit excitation-dependent color-tunable phosphorescence; structurally related compounds are also luminescent.