The　oxidation　of　alcohols　to　the　corresponding　carbonyl　compounds　is　a　pivotal　reaction　in　organic　synthesis.　Under　visible　light　irradiation,　the　homogeneous　CuCl2　and　cheap　solvent　oxidized　benzyl　alcohol　into　benzaldehyde　with　a　selectivity　higher　than　95%　using　molecular　oxygen　as　an　oxidant　The　formation　of　a　visible　light　responsive　complex　between　Cu(II)　and　solvent　is　responsible　for　the　occurrence　of　the　oxidation　of　benzyl　alcohol.　During　the　photocatalytic　process,　molecular　oxygen　was　not　incorporated　into　the　final　benzaldehyde　and　only　involved　in　the　oxidation　of　Cu(I)　into　Cu(II)　in　which　it　served　as　a　terminal　hydrogen　acceptor　to　form　H2O.　A　similar　role　of　molecular　oxygen　has　also　been　observed　in　the　heterogeneous　TiO2　photocatalytic　system.　The　understanding　of　the　role　of　molecular　oxygen　helps　us　to　further　design　new　classes　of　synthetic　organic　reactions　by　photocatalytic　processes.