Mn₃ cluster-based Metal-Organic framework for electrochemical sensing of multiple heavy metal ions

The accurate determination of multiple heavy metal ions (HMIs) is of great significance due to their high toxicity and environmental persistence. Herein, a novel Mn₃-cluster-based metal organic framework, namely [Mn₃L₃·4DMF]·4CH₃CN·2H₂O (1-Mn), has been synthesized via a solvothermal method (L = 2,2'-(1,4-Phenylenebis(thiodiethylene))dipyridine-6-carboxylic acid). It serves as a highly sensitive and selective electrochemical sensor for detecting HMIs, owing to its heteroatom-rich structure and intrinsic cavities. The limits of detection (LODs) for simultaneous detection of Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺ were 4.9 nM, 0.56 nM, 0.59 nM, and 0.33 nM, respectively, with a linear response range of 0.5-6.5 μM. The sensor demonstrates high accuracy in the analysis of practical samples, achieving recovery rates ranging from 95.57% to 104.76%. Density functional theory (DFT) calculations reveal strong p-d orbital hybridization between HMIs and 1-Mn, suggesting electron donation from O/N atoms to HMIs to form stable covalent bonds. These chemical interactions enable the sensor to exhibit effective electrochemical response toward HMIs, highlighting its promising potential for environmental water quality monitoring.