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 α-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)₃AlF₆, AlCl₃, Al(OH)₃, Ga₂O₃, InCl₃, and CdCl₂ are also discovered. The phosphorescence of α-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.