Hydrogen Production from Glycerol Photoreforming on TiO2/HKUST-1 Composites: Effect of Preparation Method

Coupling metal-organic frameworks (MOFs) with inorganic semiconductors has been successfully tested in a variety of photocatalytic reactions. In this work we present the synthesis of TiO2/HKUST-1 composites by grinding, solvothermal, and chemical methods, using different TiO2 loadings. These composites were used as photocatalysts for hydrogen production by the photoreforming of a glycerol-water mixture under simulated solar light. Several characterization techniques were employed, including X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), infrared spectroscopy (FTIR), and time-resolved microwave conductivity (TRMC). A synergetic effect was observed with all TiO2/HKUST-1 composites (mass ratio TiO2/MOF 1:1), which presented higher photocatalytic activity than that of individual components. These results were explained in terms of an inhibition of the charge carrier (hole-electron) recombination reaction after photoexcitation, favoring the electron transfer from TiO2 to the MOF and creating reversible Cu1+/Cu-0 entities useful for hydrogen production.