Selective and Efficient Photocatalytic CO2 Reduction to CO Using Visible Light and an Iron-Based Homogeneous Catalyst

Converting CO2 into valuable compounds using sunlight as the energy input and an earth-abundant metal complex as the catalyst is an exciting challenge related to contemporary energy issues as well as to climate change. By using an inexpensive organic photosensitizer under visible-light excitation (lambda > 400 nm) and a substituted iron(0) tetraphenylporphyrin as a homogeneous catalyst, we have been able to generate carbon monoxide from CO2 selectively with high turnover numbers. Sustained catalytic activity over a long time period (lambda > 50 h) did not lead to catalyst or sensitizer deactivation. A catalytic mechanism is proposed.