Luminescent 3D Lanthanide-Cadmium Heterometal-Organic Frameworks with Chemical Stability and Selective Luminescent...

Four novel three-dimensional (3D) 4d-4f heterometal-organic compounds, [LnCd₂(Pbc)₄(Meimdc)(H₂O)]·3H₂O (Ln = Eu, 1a; Tb, 1b; Sm, 1c; Dy, 1d) (HPbc = 4-(4-pyridinyl)benzoic acid; H₃Meimdc = 2-methyl-1H-4,5-imidazole-dicarboxylic acid), have been successfully prepared by a hydrothermal method. All the compounds are isostructural and show three-dimensional microporous pillar-layered structures with uncoordinated carboxylate sites hung in the channels. Compound 1a possesses excellent chemical stability. The luminescent investigations show that compounds 1a, 1b, 1c, and 1d display the characteristic emission bands of Ln³⁺ ions. Compound 1a exhibits a good potential as a luminescent sensor material for multi-responsive Ag⁺, Cu²⁺, Zn⁺, Co²⁺, and Ni²⁺ cations and some organic amines. Interestingly, 1a can capture Ag⁺, Cu²⁺, Zn⁺, Co²⁺, and Ni²⁺ cations and shows cation-dependent colorimetric response, which indicates the potential for naked sensing.