Four lanthanide-organic frameworks built from 2, 2ʹ-dinitro-4, 4ʹ-biphenyldicarboxylic acid

Four lanthanide-organic frameworks (LOFs), [LnL_1.5(DMA)]_n (Ln=Eu (1), Gd (2), Tb (3), Dy (4); H₂L=2, 2ʹ-dinitro-4, 4ʹ-biphenyldicarboxylic acid, DMA=N, N-dimethylacetylamide), have been prepared by the solvo-thermal reaction of H₂L and Ln(NO₃)₃·6H₂O. Their structures have been characterized by elemental analyses, IR, TGA, single-crystal and powder X-ray diffraction (XRD) studies. Crystal structure analyses show that LOFs 1~4 crystallize in the monoclinic system with C2/c space group. LOFs 1~4 are isomorphous and possess a binodal (3, 8)-connected three-dimensional (3D) topology network. All the LOFs exhibit high thermal stabilities (T_d > 322 ℃). Furthermore, 1 displays characteristic luminescence of Eu(Ⅲ) ion while 3 only shows the emission peak of the L2-ligand.