Lanthanide Metal−Organic Frameworks Based on Octahedral Secondary Building Units: Rare Net Topology and Luminescence

Three isomorphous three-dimensional (3D) lanthanide metal−organic frameworks, [Ln 2 (DBTDC-O 2 ) 3 (DMF) 4 ]·3DMF·2H 2 O (Ln = Nd, Eu, and Gd), have been solvothermally synthesized and characterized, where H 2 DBTDC-O 2 is a sulfone-functionalized bridging ligand, S, S -dioxodibenzothiophen-3,7-dicarboxylic acid. In the structures, two lanthanide(III) ions are bridged by four syn−syn carboxylate groups and chelated by another two carboxylate groups to generate a [Ln 2 (COO) 6 ] dinuclear moiety, which serves as octahedral secondary building units (SBUs) to produce the rare sxb 3D net (4 8 5 4 6 3 ), instead of the default primitive cubic ( pcu ) net. The frameworks possess relatively large solvent-occupied cavities despite the presence of 2-fold interpenetration. The Eu(III) compound displays intense luminescence as a result of the efficient ligand-to-metal energy transfer.