A novel organic-inorganic hybrid monocapped/bicapped Keggin structure [Co(II)(bpy)3]6(H2bpy)[(Co(II)bpy)2(PMo8(VI)Mo4(V)O40)]3 [(Co(II)bpy)(PMo8(VI)Mo4(V)O40)]·16H2O (bpy = 2,2'-bipyridine) was synthesized and shown to be an efficient visible light-driven catalyst for water oxidation.