2D Rhombus-grid networks constructed from vanadium-substituted Keggin-type polyoxomolybdophosphates and Cd/Zn complex fragments

Two 2D rhombic grid-like organic–inorganic hybrid compounds [{M(2,2′-bpy)2}2{PMo11VO40}] (M = Cd(1), Zn(2); bpy = 2,2′-bipyridine) have been hydrothermally synthesized and characterized by elemental analysis, IR spectroscopy, TG analysis, luminescence spectroscopy, X-ray powder diffraction and single-crystal X-ray diffraction. They are isomorphic and their structures can be considered that the Keggin-heteropolyanion [PMo11VO40]4− are bridged by {M(2,2′-bpy)2} groups through the O–M–O bridges into a 2D covalent network. It is noteworthy that the adjacent layers stack each other to form 3D supermolecular structure via extended C–H⋯O interaction between Keggin-anions and 2,2′-bpy ligands of different layers. Furthermore, the electrochemical behavior of 1-CPE (1-modified carbon paste electrode) and 2-CPE and their electrocatalytic reduction of nitrite were investigated.