Bioinspired Molecular Catalyst for Photocatalytic Semihydrogenation of Acetylene with Water as a Proton Source

Selective semihydrogenation of acetylene to ethylene in ethylene-rich gas streams is a significant industrial process for obtaining high-quality polyethylene products. The conventional thermal hydrogenation route requires high temperature (>100 °C), excess H₂, and noble metal Pd to achieve satisfactory conversion efficiency. Therefore, the development of a more efficient and economical low-energy method for acetylene semihydrogenation is greatly desired yet challenging. Here, we report a noble-metal-free molecular system consisting of a bioinspired [Co^II(N₄S₂)](ClO₄)₂ catalyst and a copper photosensitizer, which achieves photocatalytic semihydrogenation of acetylene to ethylene with over 96% selectivity and 96–99.9% conversion under ambient conditions for both pure acetylene and industrially relevant ethylene cofeed (containing 1% acetylene) conditions using water as a proton source. In addition, our catalytic system in deuterium oxide exhibits ability for deuterated ethylene production, which is an important building block for various deuterated polyolefins and chemicals.