Photocatalytic primary alcohol oxidation on WO₃ nanoplatelets

With the aid of direct heating through microwave irradiation in non-aqueous media, nanocrystalline tungsten(vi) oxide is achievable in 30 minutes at 200 °C, faster and at a lower temperature than conventional synthesis methods. Forming in a platelet morphology, these particles are as small as 20 nm with a BET surface area of 37 m² g^-1 WO₃. These nanoplatelets are active for the photocatalytic oxidation of the 1° alcohols benzyl alcohol (rate constant, k of 2.6 × 10^-3 h^-1) and 5-(hydroxymethyl)-2-furfural (k of 0.01 h^-1) using 10 mg of WO₃ with 2 mL of 0.250 M substrate in acetonitrile and a 150 mW cm^-2 460 nm blue LED source. As expected, these rate constants are larger than those observed for commercially prepared, micron-sized WO₃. XPS analysis shows that during catalysis, the concentration of W⁵⁺ on the surface increases, but the nanoplatelets are stable under these reaction conditions. The overall morphology and size of the particles are retained through the reactions. Moreover, the nanoplatelets are recyclable-showing no loss in activity for four reaction cycles.