Photocatalytic CO2 reduction with a TiO2-supported copper photosensitizer and an iron-based CO2 reduction catalyst

The combination of the homogeneous iron catalyst (2,4-bis(trimethylsilyl)bicyclo[4.3.0]nona-1,4-dien-3-one)iron tricarbonyl and the copper based photosensitizer [Cu(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline-5,6-disulfonate-disodium)(xantphos)]PF6 (PS 1) supported on TiO2 (Hombikat) allows for the reduction of carbon dioxide to carbon monoxide in the presence of 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzimidazole (BIH) as the sacrificial electron donor. The application of the titania supported PS 1 resulted in a more than doubled productivity compared to the fully homogeneous system. Applying the composite material with highest copper loading (C 4) improved the catalyst turnover numbers for the iron catalyst up to 866 (TONCO (Fe)). Quantum yields up to 9.5% at 415 nm and 0.07 W cm(-1) were achieved. The composite materials Cu-PS@TiO2 were investigated by STEM, UV/vis and time-resolved emission spectroscopy, and cyclic voltammetry as well as differential pulse voltammetry.