Visible‐Light Driven Acetylene Semi‐Hydrogenation to Ethylene With a Copper Photosensitizer and a Cobaloxime Catalyst

ABSTRACT The purification of ethylene streams from acetylene impurities remains a key industrial challenge, for which light‐powered strategies are emerging as sustainable alternatives to conventional approaches. Recent studies have shown that hydrogen atom transfer (HAT) pathways enable highly selective acetylene semi‐hydrogenation by ensuring rapid and controlled hydrogen delivery while suppressing over‐hydrogenation or H 2 evolution. Here, we report a fully noble‐metal‐free homogenous photocatalytic system in which a molecular cobaloxime catalyst [Co(dmgH) 2 (Im)Cl] (dmg = dimethylglyoxime, Im = imidazole) operates in tandem with a Cu‐based photosensitizer [Cu(N^N)(P^P)] + to drive the selective transfer hydrogenation from acetylene to ethylene under visible light irradiation. Under a pure C 2 H 2 atmosphere, our system converts acetylene to ethylene with a turnover number (TON) of 670 after 48 h of visible‐light irradiation with 99.6% selectivity, while under ethylene‐rich conditions, acetylene impurities are completely removed with 99.3% selectivity. Mechanistic studies reveal that catalysis proceeds via a Co III ─H intermediate. Overall, this work demonstrates that rational pairing of cobaloxime catalysts with earth‐abundant Cu‐based photosensitizers provides an efficient and sustainable strategy for photocatalytic acetylene semi‐hydrogenation and ethylene purification.