“…Solids made up of mixed anions have been taken up by researchers to explore newer crystal chemistry and discover many interesting properties such as high-temperature superconductivity, optical properties, second-harmonic generation (SHG), piezoelectricity, pyroelectricity, etc. − If such mixed-anion compounds are layered, then they show interesting intercalation behavior and direction-dependent properties. In oxyhalides, oxyhydrides, oxysulfides, and oxynitrides, the oxide anions are partially replaced with the hetero anion, and their differing charge, ionic radii, electronegativity, and polarizability act as tools to tailor their desired function. − Bismuth based compounds, showing strong photooxidation ability, were widely investigated as photocatalysts to split water and in environment remedial applications. − Bismuth oxychloride (BiOCl) comprising of [Bi 2 O 2 ] 2+ slabs interleaved with two layers of Cl – ions arranged in a layered fashion presents a prototype example to comprehend the role of mixed anion system in many bismuth-containing oxychlorides .…”