Two novel organic–inorganic hybrid materials of oxovanadium–organophosphonate with a 3D supramolecular structure, [{M(1,10-phen)}(VO)(OH)(hedp)]·H₂O (M = Cu (1), Zn (2); hedpH₄ = 1-hydroxyethylidenediphosphonate, 1,10-phen = 1,10-phenanthroline), have been synthesized under hydrothermal conditions. Compounds 1 and 2 are isomorphous and adopt a three-dimensional supramolecular network structure. The interconnection of {(VO₄)(OH)}, {MN₂O₃} and {CPO₃} polyhedra leads to a 2D layer through corner-sharing, and such layers are further assembled into a 3D supramolecular structure by π–π stacking interactions. Surface photovoltage and luminescent properties of the two compounds have also been studied.