We note, however, that this is still a drastic improvement compared to the 87 hours required for our previous Co-PCN-222-based MOF system to fully remove C2H2 from the industrial mixture, and compared to the 68 hours required by recently reported metal-organic framework nanosheets to reduce acetylene concentration below 5 ppm. Crucially, like the homogeneous system, no over-hydrogenation to C2H6 is observed, such that the selectivity for C2H4 remains >99.9% (Figure ). Sorption isotherms demonstrate a higher Henry's adsorption constant for acetylene than that for ethylene (𝐾 ! " ! ! ! = 3.17 × 10 -3 mmol g -1 torr -1 and 𝐾 ! " ! ! " = 2.29 × 10 -3 mmol g -1 torr -1 as determined from the linear region of each isotherm, Figure ). We expect that, however, the propensity of ZrCo-MOF to selectively adsorb either C2H2 or C2H4 will be very different in the solution compared to the gas phase. Indeed, we exclude C2H2 adsorption effects on the photoreduction reaction by the ZrCo-MOF-based heterogeneous system. This conclusion is corroborated by the unchanged C2H2 content that is measured for the ZrCo-MOF-based heterogeneous system under C2H4/C2H2 either before the 4 h of illumination or after being kept in the dark for 4 h (Figure ).