A New [PMo12O40]3−-Based NiII Compound: Electrochemical and Photocatalytic Properties for Water Pollutant Removal

A polyoxometalate-based metal-organic complex with the ability to treat pollutants in water was obtained under hydrothermal conditions, namely [Ni(H₂L)(HL)₂](PMo₁₂O₄₀)·3H₃O·4H₂O (<b>1</b>) (H₂L = 4,4'-(1H,1'H-[2,2'-biimidazole]-1,1'-diyl)dibenzoicacid). Structural analysis reveals that the [Ni(H₂L)(HL)₂] units are interconnected into a 2D layer via hydrogen bonds between adjacent carboxyl groups and water molecules of crystallization. [PMo₁₂O₄₀]^3- anions are embedded within the larger pores of the layer and are connected to the adjacent layers through hydrogen bonds, ultimately expanding the structure into a 3D supramolecular architecture. The intermolecular interactions were studied via Hirshfeld surface (HS) analysis. Electrochemical performance tests reveal that <b>1</b> exhibits electrocatalytic activity toward the oxidation and reduction of diverse pollutants in water, including NO₂^-, Cr(VI), BrO₃^-, Fe(III), and ascorbic acid (AA). Additionally, it can also serve as an amperometric sensor for the detection of BrO₃^- and Cr(VI). Photocatalytic studies reveal that compound <b>1</b> functions as a bifunctional photocatalyst, which not only achieves efficient degradation of organic dyes but also demonstrates remarkable reduction efficiency for toxic Cr(VI). Compound <b>1</b> demonstrates significant potential for practical water remediation applications.