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]·H ₂O}_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.