Polyoxometalate (POM) supported metal complex has proved to be a suitable catalyst for waterreduction/oxidation in recent studies. To catalyze hydrogen evolution reaction (HER), we have employed aPOM-based inorganic-organic hybrid compound [Cu^II(2,2′-bpy)(H₂O)₂Cl][Cu_II(2,2′-bpy)(H₂O)₂Al(OH)₆-Mo₆O₁₈].4H2O (1) with a spiral-chain-like structure consisting of Anderson type polyoxometalate,[Al(OH)₆Mo₆O₁₈]^3- onto which Cu-complex, [Cu(H₂O)₂(bpy)]²⁺ fragments are supported. This compoundacts as a pre-catalyst towards forming the active catalyst for catalyzing hydrogen evolution reaction (HER) bywater reduction in a neutral medium. The active catalyst derived from this compound 1 achieves a currentdensity of 1 mA/cm² at an overpotential of 348 mV. The turnover frequency calculated for the active catalystis found to be 1.780 [mol H₂ (mol Cu)^-1s^-1] with the Faradaic efficiency of 85%.

A unique electrochemical structural rearrangement under the electrochemical condition observed for a chain-like structured Cu-complex supported on Anderson type polyoxometalate,[Cu^II(2,2′-bpy)(H₂O)₂Cl][Cu_II(2,2′-bpy)(H₂O)₂Al(OH)₆-Mo₆O₁₈].4H2O (1) resulting in the formation of the active catalyst for the electrochemical HER activity. The active catalyst achieves the current density of 1 mA/cm² with an overpotential of 348 mV with faradic efficiency of 85% at neutral pH.