Transformation of Perovskite BaBiO3 into Layered BaBiO2.5 Crystals Featuring Unusual Chemical Bonding and Luminescence

Coordination environment engineering : Layered stoichiometric BaBiO 2.5 , synthesized by nontopotactic transformation of perovskite BaBiO 3 , features an unusual electron‐density distribution and Bi−O bonding situation featuring one ionic and three covalent bonds, which give rise to peculiar near‐infrared luminescence never seen before in any Bi‐containing system (see figure).