Artificial Photosynthesis of Formamide via an Oxidant‐Free Photoinduced Radical Coupling Route over Pt‐CdS

Large-scale manufacturing of formamide is always involved with the use of carbon monoxide, hence developing a series of eco-friendly synthesis routes is of great significance. Alternative feedstock of low-cost methanol is expected to fulfill this breakthrough due to its green and renewable nature; however, the overoxidation of methanol severely inhibits the efficacious formamide synthesis from methanol and ammonia through the conventional catalytic route. Herein, we report the successful development of a direct radical coupling route for converting methanol and ammonia into high-selectivity formamide and hydrogen without extra oxidants under ambient conditions. The optimized Pt-CdS photocatalysts offered an impressive formamide production rate of 1.45 mmol g^-1 h^-1, as well as an exceptional hole selectivity reaching up to 63.5%. The oxidant-free radical mechanism of high-efficiency formamide generation as revealed by in situ characterizations (e.g., in situ electron paramagnetic resonance and in situ transient absorption spectroscopy), stems from the photogenerated holes oxidizing the methanol to hydroxymethyl radical for subsequently direct C─N coupling with amino radical. This work demonstrates an efficient oxidant-free photoinduced radical coupling strategy with the promise of an acceptable alternative to current technologies for artificial photosynthesis formamide using clean and abundant solar energy.