“…Litharge-derived [Bi 4 O 4 ] 4+ layers are observed in a multitude of structures, with the interlayer space filled by a variety of anions, e.g. halide (Charkin et al, 2021(Charkin et al, , 2003, sulfate (Siidra et al, 2020), nitrate (Ziegler et al, 2004), carbonate (Grice, 2002) and borate (Cong et al, 2011), as well as some others. In particular, there are two examples of borate anions sandwiched between the litharge layers, Bi 2 O 2 -[B 3 O 5 (OH)] and Bi 2 O 2 [BO 2 (OH)] (Cong et al, 2011).…”