A step towards artificial photosynthesis

A photocatalyst that reduces CO2 into carbon monoxide is being commercialized by Tokyo Chemical Industry Co. (Tokyo, Japan; www.tcichemicals.com/en/jp/index.html). Developed by Osamu Ishitani and his research group at Tokyo Institute of Technology (TiTech; Japan; www.chemistry.titech.ac.jp/~ishitani/index-jp.htm), the catalyst is a step towards artificial photosynthesis whereby CO2 can be converted into useful chemicals using sunlight. Ishitani’s group combined a rhenium (I) biscarbonyl complex (which efficiently reduces CO2 but has a low absorption coefficent for visible light) with a ruthenium (II) complex as photo sensitizer (a strong absorbance for visible light) to form a supramolecule dubbed Ru(II)-Re(I). This dual complex system shows a very high efficiency for reducing CO2 into CO under irradiation with visible light. The catalyst was improved by optimizing the ligands on the Re site. Ru-Re(FPh), with two tri( p-fluorophenyl)phosphine (P( p-FPh)3) ligands, was found to be a good photocatalyst with high selectivity for CO (quantum yield of 0.15), high efficiency (turnover frequency of TNCO = 207–1) while maintaining a high stability. The researchers also showed that even under irradiation with high-intensity light,…