Photocatalytic Conversion of CO 2 to CO by a Copper(II) Quaterpyridine Complex

The invention of efficient systems for the photocatalytic reduction of CO 2 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 CO 2 gas. The Cu II quaterpyridine complex [Cu(qpy)] 2+ ( 1 ) is found to be a highly efficient and selective catalyst for visible‐light driven CO 2 reduction in CH 3 CN using [Ru(bpy) 3 ] 2+ (bpy: bipyridine) as photosensitizer and BIH/TEOA (1,3‐dimethyl‐2‐phenyl‐2,3‐dihydro‐1 H ‐benzo[ d ]imidazole/triethanolamine) as sacrificial reductant. The photocatalytic reaction is greatly enhanced by the presence of H 2 O (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 CO 2 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 CO 2 .