Improvement of CO₂ Reduction Photocatalysis of a Ru(II)–Re(I) Complex and Carbon Nitride Hybrid by Coadsorption of an Os(II) Complex Photosensitizer

Photocatalytic CO2 reduction has attracted attention as a prospective technology for addressing global warming and the reduction in fossil fuel resources. Hybrid photocatalysts comprising a visible light-absorbing semiconductor and a supramolecular photocatalyst with photosensitizer and catalyst units in one molecule have been developed for CO2 reduction. As an example, a hybrid of TiO2-loaded polymeric carbon nitride (PCN) and a Ru(II)–Re(I) supramolecular photocatalyst (RuRe/TiO2/PCN) works as a CO2 reduction photocatalyst in the presence of triethanolamine (TEOA) to give CO with a high selectivity. However, its durability is low, and the maximum turnover number of CO formations (TONCO) is less than 100. In this study, a system was constructed with coadsorption of an Os(II)-complex photosensitizer (OsP) on the surface of RuRe/TiO2/PCN to improve the low durability of the hybrid photocatalyst by promoting a more rapid electron supply to the Re catalyst unit of RuRe. The coadsorption of OsP increased the TONCO of RuRe/TiO2/PCN to 239.