Single‐Atom Nickel on Carbon Nitride Photocatalyst Achieves Semihydrogenation of Alkynes with Water Protons via Monovalent Nickel
Tongtong Jia, Di Meng, Ran Duan, Hongwei Ji, Hua Sheng, Chuncheng Chen, Jikun Li, Wenjing Song, Jincai Zhao
Abstract
Abstract Prospects in light‐driven water activation have prompted rapid progress in hydrogenation reactions. We describe a Ni 2+ −N 4 site built on carbon nitride for catalyzed semihydrogenation of alkynes, with water supplying protons, powered by visible‐light irradiation. Importantly, the photocatalytic approach developed here enabled access to diverse deuterated alkenes in D 2 O with excellent deuterium incorporation. Under visible‐light irradiation, evolution of a four‐coordinate Ni 2+ species into a three‐coordinate Ni + species was spectroscopically identified. In combination with theoretical calculations, the photo‐evolved Ni + is posited as HO−Ni + −N 2 with an uncoordinated, protonated pyridinic nitrogen, formed by coupled Ni 2+ reduction and water dissociation. The paired Ni−N prompts hydrogen liberation from water, and it renders desorption of alkene preferred over further hydrogenation to alkane, ensuring excellent semihydrogenation selectivity.