Synthesis, Characterization, and Application of a Polyoxometalates-Based CuII Complex for Efficient Catalytic Oxidation and Electrochemical Detection

The development of eco-friendly, high-efficiency polyoxometalates (POMs) catalysts is vital for advancing catalytic oxidation and electrochemical detection in environmental protection. Herein, a POM-based Cu^II-containing complex with the molecular formula [H(4-AP)]₈[Cu₂(H₂O)₄(P₂Mo₅O₂₃)₂]·8H₂O (1) (4-AP = 4-aminopyridine) is synthesized using the hydrothermal method, and the crystal structure is determined by single X-ray diffraction (SXRD), infrared (IR) spectroscopy, and powder X-ray diffraction (PXRD). Structurally, complex 1 exhibits a one dimension (1D) chain arrangement, composed of Cu^II ions and Strandberg-type (P₂Mo₅O₂₃)⁶⁻ anionic clusters. These 1D chains are further interconnected through [H(4-AP)]⁺ ligands, resulting in the formation of a two dimension (2D) supramolecular network. Complex 1 serves as an outstanding heterogeneous catalyst for the oxidation of methyl phenyl sulfide (MPS), demonstrating a remarkable conversion rate of 99% for MPS and a selectivity of 98% toward methyl phenyl sulfoxide (MPSO). In addition to its catalytic capabilities, complex 1 is also employed in the electrochemical detection of Fe^III and Cr^VI ions, with low limits of detection (LODs) at 4.92 µm for Fe^III and 7.82 µM for Cr^VI.