We have designed and fabricated efficient photocatalysts sensitive to visible light, Cu(II)-grafted TiO 2 (Cu(II)/TiO 2 ) and WO 3 (Cu(II)/WO 3 ), after the suggestions made in the literature as to the photo-induced interfacial charge transfer from a semiconductor to an adsorbed molecular species and the catalytic multi-electron reduction of oxygen by Cu(I) ions. In fact, Cu(II)/TiO 2 and Cu(II)/WO 3 photocatalysts decomposed 2-propanol to CO 2 via acetone under visible light (>400nm) with quantum efficiencies of 8.8% and 17%, respectively. The turnover numbers of this reaction exceeded 4.1 for Cu(II)/TiO 2 and 51 for Cu(II)/WO 3 , indicating that both function catalytically.