Selective Photocatalytic Reduction of Acetylene to Ethylene Powered by a Cobalt-Porphyrin Metal–Organic Framework

Purifying crude ethylene streams from an acetylene contaminant using state-of-the-art thermal hydrogenation requires high temperature, an external feed of H2 gas, and noble metal catalysts and is not only expensive and energy-intensive but also prone to overhydrogenation to ethane. This Letter reports the photocatalytic semihydrogenation of acetylene to ethylene using the metal-organic framework (MOF) Co-PCN-222. Under pure acetylene atmosphere the system achieves an overall conversion of 1.6 mol ethylene per gram of Co and remains catalytically active for 1 week. Under a mixed acetylene/ethylene atmosphere (the industrially relevant conditions), the system achieves nearly 100% conversion of acetylene after 87 h with >99.9% ethylene selectivity over ethane. The heterogeneous nature of the MOF lends advantages over the homogeneous catalyst, namely, facile recyclability and increased longevity. These features also offer substantial advantages over current thermocatalytic hydrogenation technologies with respect to selectivity and sustainability. While MOFs have been pursued academically for the physical separation of acetylene and ethylene, this is the first demonstration of MOFs as catalysts for the selective, photocatalytic conversion of acetylene to ethylene.