Three-dimensional lanthanide metal–organic frameworks with the fluorene-based carboxylate ligands: Syntheses, structures, and properties

Seven three-dimensional (3D) lanthanide metal–organic frameworks (LnMOFs) [Ln3(MFDA)4(NO3)(DMF)3]n (Ln = Sm (1), Gd (2), Tb (3), Dy (4)) and {[Ln2(MFDA)2(HCOO)2(H2O)6]·H2O}n (Ln = Gd (5), Tb (6), Dy (7), H2MFDA = 9,9-dimethylfluorene-2,7-dicarboxylic acid, DMF = N,N-dimethylformamide) have been solvothermally synthesized and their structures have been determined using either X-ray powder or single-crystal diffraction data. 1–4 are isostructural, 5–7 are isostructural. Their structures all feature a 3D Ln–O rod-packing structure with 1D channels occupied by guest molecules. The solvent accessible spaces of the desolvated phase for 1–7 are about 29% of the total volume. The photoluminescent properties of 1–7 have been investigated. Complexes 1–7 all display the fluorene-based blue emission originated from the π–π∗ transitions in the solid state at room temperature. The thermal properties of 1–7 have also been studied.