We used pentacarboxylic acid ligand 3, 5-di(2', 4'-dicarboxylphenyl) benzoic acid (H₅L) to synthesize two structural similarity lanthanide-cobalt heteronuclear bimetallic organic frameworks (Ln-Co-MOFs) by hydrothermal method: (C₂H₆NH₂)₅{[Eu₉Co(L)₆(H₂O)₅(OH)₄] ·5DMF}_n (1), (C₂H₆NH₂)₂{[Sm₉Co(L)₆(H₂O)₃Cl] ·5DMF}_n (2). The structures were characterized and the property was tested by single crystal X-ray diffraction, powder X-ray diffraction, thermogravimetry, infrared, fluorescence spectra, and magnetism. The results show that 1 and 2 both belong to the trigonal R3 space group and have novel 3D structures and good thermal stability. Among them, 1 has strong fluorescence properties, which can sensitively identify drug molecules sulfasalazine and organic molecules glutaraldehyde. The detection limits could reach 0.95 and 2.10 μmol·L^-1, respectively. In addition, 1 and 2 were antiferromagnetic at 1 kOe.