Boosting Light-Driven CO2 Conversion Into CO by a Polypyridine Iron(II) Catalyst Using an Organic Sensitizer

Direct photochemical conversion of CO2 into a single carbon-based product currently represents one of the major issues in the catalysis of the CO2 reduction reaction (CO2RR). In this work, we demonstrate that the combination of an organic photosensitizer with a heptacoordinated iron(II) complex allows to attain a noble-metal-free photochemical system capable of efficient and selective conversion of CO2 into CO upon light irradiation in the presence of N,N-diisopropylethylamine (DIPEA) and 2,2,2-trifluoroethanol (TFE) as the electron and proton donor, respectively, with unprecedented performances (ΦCO up to 36 %, TONCO >1000, selectivity >99 %). As shown by transient absorption spectroscopy studies, this can be achieved thanks to the fast rates associated with the electron transfer from the photogenerated reduced dye to the catalyst, which protect the dye from parallel degradation pathways ensuring its stability along the photochemical reaction. These results point out how the profitable merging of molecular species based on cheap and abundant elements can have great potential to target efficient and selective transformations crucial for the conversion of solar energy into fuels.