Anion exchange in bismuth oxyhalides for electronic property control and isolation of BiON3

Bismuth oxyhalides are a class of layered materials with rich potential for chemical and electronic tuning through anionic substitution, including the less-explored incorporation of pseudohalides such as azide (N₃⁻). Here, we develop three synthetic strategies for the synthesis of BiON₃: post-synthetic exchange, solvothermal synthesis, and coprecipitation. We present the first structural model for BiON₃ that is supported by Rietveld refinement, revealing a highly disordered structure that features interdigitated azide molecules between the layers. We then probe the effects of heteroanion incorporation on the electronic structure of BiON₃, including through the synthesis of mixed azide/iodide systems. Further, we demonstrate intriguing thermally induced reactivity in BiON₃ that is suggestive of N atom transfer and subsequent gas evolution. This work considerably expands the available routes for synthetic control of this promising material platform.