Ethylene is one of the world's most important commodity chemicals. Nearly 200 million tons are produced annually, the most of any organic compound, with ethylene being an intermediate in 50-60% of all plastics. The vast majority of ethylene is derived from the steam cracking of petroleum, a process which unavoidably introduces impurities into the crude ethylene stream. From the standpoint of plastics production, the most pernicious of these contaminants is acetylene, which poisons the Ziegler-Natta catalysts that polymerize ethylene into plastics. Typically, crude ethylene streams contain 0.5-2% acetylene by volume; prior to plastics production, removal of the acetylene impurity is imperative. The current industrial standard for thermocatalytic acetylene semihydrogenation has weaknesses in that it uses high temperatures and pressures, H2 co-feed, and precious metal Pd catalysts. This reaction is additionally prone to over-hydrogenation to ethane, a less valuable product that also inhibits polymerization of ethylene, and therefore must be removed using cryogenic sublimation prior to plastics production. The use of Pd and excess H2 as co-feed limits the ethylene selectivity of the thermocatalytic process to 85% with >90% conversion at 200 °C. Recently, physisorption-based acetylene purification or electro- and photo-catalytic routes have been pursued, by our research groups and others, to avoid the drawbacks of the thermochemical routes. We sought to improve upon selectivity and conversion by designing photocatalytic systems based on Co-porphyrin catalysts, and succeeded in creating both a homogenous system based on [meso-tetra(4-sulfonatophenyl)porphyrinato]-cobalt(III) and a heterogeneous system based on the metal-organic framework (MOF) Co- PCN-222 (with [mesotetra(4-carboxyphenyl)porphyrinato]-cobalt(III) linkers). Notably, both achieved nearly 100% conversion with >99% selectivity for ethylene over ethane under industrially relevant conditions (dilute acetylene in a predominantly ethylene stream). However, long irradiation times (>28 h) with both homogenous and heterogenous Co-porphyrins system are necessary to achieve photocatalytic conversion of acetylene under a mixed acetylene/ethylene atmosphere (the industrially relevant conditions), which makes it unlikely for the photocatalytic process to be implemented industrially. Therefore, the discovery of novel, more efficient catalysts, and their integration in photocatalytic systems for this industrially relevant transformation remain essential.