Abstract Uracil photooxygenation occurs in acidic water (pH= 1) at 25 C, under oxygen (1 atm), irradiating with λ> 300 nm in the presence of selected polyoxometalates (POM). A marked diversity of photocatalytic behavior is registered for different POMs in terms of oxidation rate and selectivity. H 3 PW 12 O 40 (PW 12) appears to be the most reactive photocatalyst, by far superior to isostructural complexes, leading to a product distribution ...