Photocatalytic conversion of CO₂ to CO by a copper(II) quaterpyridine complex

The invention of efficient systems for the photocatalytic reduction of CO₂ comprising earth‐abundant metal catalysts is a promising approach for the production of solar fuels. One bottleneck is to design highly selective and robust molecular complexes that are able to transform the CO₂ gas. The Cu^II quaterpyridine complex [Cu(qpy)]²⁺ (1) is found to be a highly efficient and selective catalyst for visible‐light driven CO₂ reduction in CH₃CN using [Ru(bpy)₃]²⁺ (bpy: bipyridine) as photosensitizer and BIH/TEOA (1,3‐dimethyl‐2‐phenyl‐2,3‐dihydro‐1H‐benzo[d]imidazole/triethanolamine) as sacrificial reductant. The photocatalytic reaction is greatly enhanced by the presence of H₂O (1–4 % v/v), and a turnover number of >12 400 for CO production can be achieved with 97 % selectivity, which is among the highest of molecular 3d CO₂ reduction catalysts. Results from Hg poisoning and dynamic light scattering experiments suggest that this photocatalyst is homogenous. To the best of our knowledge, 1 is the first example of molecular Cu‐based catalyst for the photoreduction of CO₂. © 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim.