Highly Efficient Light-Driven CO2 to CO Reduction by an Appropriately Decorated Iron Porphyrin Molecular Catalyst

Abstract

The photocatalytic CO2 reduction into value-added chemicals is regarded as one promising technology to mitigate environmental issues and the energy crisis of the modern world due to the extended CO2 emissions. Recent advances have shown that iron porphyrins are considered as one of the most efficient molecular catalysts in the activation and reduction of molecules like CO2. Thus, a suitably modified FeIII porphyrin ([FeIII(TF4TMAP)](CF3SO3)5) was prepared and its catalytic activity in terms of photocatalytic reduction of CO2 was studied. This iron catalyst possesses four fluorine substituents in the ortho and the meta position of each meso-phenyl group of the porphyrin, while trimethylammonium groups were placed in the para position. Photocatalytic studies were performed in the presence of an iridium complex as a chromophore and have shown that [FeIII(TF4TMAP)](CF3SO3)5 can effectively reduce CO2, achieving excellent turnover numbers (up to 5500 TONs) and high turnover frequencies. The main reduction product of this photocatalytic system was CO, and only a small amount of hydrogen was detected, presenting a maximum selectivity of 86 % for CO.