Selective Semi‐Hydrogenation of Acetylene using a Single‐Atom Cobalt on Carbon Nitride Photocatalyst with Water as a Proton Source

Light-powered strategies for the semi-hydrogenation of acetylene to ethylene are rapidly emerging as sustainable alternatives to the traditional thermochemical processes. The development of a robust, selective, as well as recyclable, non-noble catalyst that can be powered by visible light and uses water as proton source to accomplish this important reaction remains a key challenge. Here the first demonstration of a cobalt single-atom catalyst supported on carbon-nitride (Co-CN) as an all-in-one photocatalyst for the semi-hydrogenation of acetylene to ethylene is reported using water as the proton source, offering advantages over current hydrogenation technologies. Carbon nitride hosts the individual catalytic active sites of cobalt thus combining photosensitizer and cocatalyst in one unit, in line with first-principles modelling. Under visible light irradiation, Co-CN reduces acetylene to ethylene with stable activity for over 40 days of continuous operation, ≥99.9% selectivity, and provides means for coupling organic upgrading to produce valuable oxidation products. The heterogeneous Co-CN can be easily recovered and reused repeatedly without loss of catalytic activity and structural integrity. Thereby, the integrated and recyclable platform overcomes the need of coupling a separate photosensitizer to a catalyst, and using noble metal catalysts with an external H₂ gas feed.