Amino-substituted triazatriangulenium photosensitizers for CO capture and aminocarbonylation to amides.

Efficient photoreduction of CO to CO using noble-metal-free systems remains a significant challenge in artificial photosynthesis. Developing low-cost photosensitizers capable of capturing CO and facilitating electron transfer is therefore essential. Here, we report an amino-substituted triazatriangulenium photosensitizer (A-TATA) that enables light harvesting and CO capture in a photocatalytic system. Systematic studies show that A-TATA, functionalized with free amino groups, captures CO as carbamic acid, serving as a local CO reservoir. This increased local concentration of CO lowers the onset potential of the cobalt catalyst. Notably, the system achieves a turnover number of 33,976 with 98% selectivity and an optimized quantum yield of 51% for CO-among the highest reported for molecular photocatalysis. Furthermore, the generated CO is converted into amides via aminocarbonylation, achieving 85% atomic efficiency and operating effectively even in the absence of solvent. These findings offer a strategy for designing versatile organic photosensitizers for sustainable CO capture and conversion.