Heterometallic organic framework: a highly selective functional probe for carmine and TNP molecules

Abstract

Based on the 2,2′-bipyridine-4,4′-dicarboxylic acid ligand (H₂LZ), a heterometal–organic framework with a three-dimensional interpenetrating structure, namely [TbZn(LZ)₂(HCOO)(H₂O)₃]_n (1), was synthesized. Compound 1 exhibited stable luminescence in the pH range of 2–12 in an aqueous solution. It is noteworthy to mention that compound 1 could discern carmine (CM) in some food additives and trinitrophenol (TNP) in nitroaromatic explosives by the fluorescence quenching effect. In particular, compound 1 displayed high sensitivity, selectivity, recyclability, and anti-interference for sensing CM and TNP in aqueous solutions, and the detection limits of CM and TNP were 7.76 × 10⁻⁶ M and 1.35 × 10⁻⁴ M, respectively. In addition, the fluorescence mechanisms of compound 1 for sensing CM and TNP molecules are also discussed in detail.