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Abstract The clean‐energy‐driven synthesis of urea from carbon‐ and nitrogen‐containing small molecules has garnered significant interest but remained great challenges to achieve with high selectivity. Herein, we present a photocatalytic pathway for the selective urea synthesis through the oxidative coupling between CO and NH 3 . The key factor in this process is the atmospheric O 2 level, which plays a crucial role in controlling both the urea production rate and its selectivity. Using oxygen‐deficient TiO 2 under an air‐level (20%) O 2 atmosphere, we achieved a urea generation rate of 54.31 mg g cat −1 h −1 with 100% selectivity. This rate is 38.52 times higher than under oxygen‐free conditions, while further increasing the O 2 level significantly reduces selectivity. Mechanistic studies reveal that the process begins with the oxidation of NH 3 to •NH 2 through oxidative radicals generated on TiO 2 , especially the oxygen‐derived O 2 •– . This •NH 2 radicals then couple with CO to form urea. The concentration of radicals is controlled by the O 2 level, with the optimal concentration under air‐level O 2 enabling efficient NH 3 oxidation to •NH 2 while preventing over‐oxidation.
Huang et al. (Mon,) studied this question.