Abstract: | The crystal structure of oxonium neodymium bis(sulfate), (H3O)Nd(SO4)2, shows a two‐dimensional layered framework assembled from SO4 tetrahedra and NdO9 tricapped trigonal prisms. One independent sulfate group makes four S—O—Nd linkages, while the other makes five such connections to generate an unprecedented anhydrous anionic [Nd(SO4)2]− layer. To achieve charge balance, H3O+ cations are inserted between adjacent layers where they participate in hydrogen‐bonding interactions with the sulfate O atoms of adjacent layers. |