Na 4W 10O 32/ZrO 2 nanocomposite prepared via a sol–gel route: A novel, green and recoverable photocatalyst for reductive cleavage of azobenzenes to amines with 2-propanol

Abstract

Sodium decatungstate–zirconia (Na 4W 10O 32/ZrO 2) nanocomposite was prepared through entrapment of Na 4W 10O 32 into zirconia matrix by a sol–gel route. This new nanocomposite was characterized by means of X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), UV–vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and surface area measurement. The nanocomposite was used as a green and recyclable heterogeneous photocatalyst for rapid and efficient reductive cleavage of azobenzenes into their corresponding amines with 2-propanol as a hydrogen donor at room temperature under N 2 atmosphere. The reductive cleavage occurs without hydrogenolysis or hydrogenation of reducible moieties, such as –NO 2, –OH, –CH 3, –OCH 3, –COOH, –COCH 3, halogen and –CN. The photocatalyst has been reused several times, without observable loss of activity and selectivity. According to the azobenzene reduction, the Na 4W 10O 32/ZrO 2 nanocomposite is more effective as a photocatalyst than pure Na 4W 10O 32, showing that the nanocomposite approach could be an excellent choice to improve the photoactivity of POMs.