Metal-Organic Framework MIL-125 Derived Mg2+-Doped Mesoporous TiO2 for Photocatalytic CO2 Reduction

In this study, Mg2+-doped mesoporous TiO2 photocatalysts derived from Mg2+ adsorption (MA) process on MIL-125, a metal-organic framework material, were prepared and employed for photocatalytic reduction of CO2 to produce CO. The Mg2+ doping concentration was controlled by varying the Mg2+ concentration in the Mg2+ adsorption process. It was demonstrated that the Mg2+ doping promoted the generation of surface Ti3+ and significantly increased transient photocurrent density. Over a 4 h UV/Vis irradiation period, the best performing photocatalyst, 1MA, delivered a CO production rate similar to 20 times higher than that of P25, a commercially available TiO2 nanopowder. It is believed that the Mg2+ adsorption process introduced more favorable properties to the TiO2 photocatalysts, such as higher surface area and porosity for more reactive sites, and concentrated surface Ti3+ centers for improved charge transfer.