Hydrogen Atom Transfer-Mediated N-Heterocycles Dehydrogenation Coupled with the CO2 Photoreduction to Syngas

Homogeneous photocatalytic organic oxidation coupled with CO₂ reduction remains challenging due to the susceptibility to a back electron transfer scenario. Herein, a pyridinethiol iron-catalyzed system is developed to achieve N-heterocycles dehydrogenation coupled with CO₂ photoreduction to syngas. The system is comprised of 2,4,5,6-tetrakis(diphenylamino)isophthalonitrile (4DPAIPN) photoredox catalysts, earth-abundant iron catalysts, and pyridinethiol organocatalysts, and the employment of pyridinethiol both as a hydrogen atom transfer (HAT) catalyst to promote N-heterocycles dehydrogenation and as an effective ligand for CO₂ reduction is the key to realizing the coupled redox reaction. Experimental and theoretical calculation results demonstrate the positive correlation between the reactivity and the S-H bond dissociation enthalpy (BDE) as well as the radical polarity (ω) parameter, gaining deep insights into understanding and designing the coupled reaction.