The search for photocatalysts allowing the highly active, selective, and stable conversion of molecular oxygen into hydrogen peroxide is of worldwide interest. Here, the authors report the efficient conversion of O-2 into H2O2 with approximate to 100% selectivity and stable cycle stability by a triphasic metal oxide photocatalyst with a cobalt hydroxide carbonate nanosheet phase for water oxidation as well as iron oxide and titanium oxide phases of a core-shell morphology for charge transfer and oxygen reduction, denoted as CFT. The different surface energies of 0.78 (anatase) and 0.93 J m(-2) (rutile) for titanium oxide and 1.39 J m(-2) for iron oxide result in a core-shell morphology. The band gaps for iron oxide (2.02 eV), titanium oxide (approximate to 3 eV), and cobalt hydroxide carbonate (3.80 eV) sites reveal that the CFT photocatalyst allows visible-to-UV light absorption. The O-18(2) isotope-labeling experiments prove that the core-shell structure promotes hole transfer toward the water oxidation site. Additionally, the hole-induced H2O2 decomposition at the oxygen reduction site is efficiently hindered. Moreover, the photogenerated electrons transfer toward the oxygen reduction site to produce H2O2 from O-2 with approximate to 10-fold higher activity than those by conventional single- or dual-phase photocatalysts, while giving robust cycle stability.