The Coordination Microenvironment Tailoring in 2D MOFs for Enhancing Photocatalytic Acetylene Semi‐Hydrogenation

Abstract The semi‐hydrogenation of acetylene (C 2 H 2 ) to ethylene (C 2 H 4 ) by photocatalytic is a new and clean strategy for removal of C 2 H 2 impurities from raw C 2 H 4 to produce polymer‐grade C 2 H 4 . In the state‐of‐the‐art, most of the studies on photocatalytic acetylene hydrogenation (PAH) were achieved by cobalt‐based photocatalysts, while the studies on the influence of microenvironment of cobalt catalytic active sites remain limited. Herein, via coordination ligand modulation method, we chose three 2D metal organic framework (2D MOFs) with different coordinated atoms (N, O, and S) around cobalt center and afforded CoN 4 MOF, CoO 4 MOF, and CoS 4 MOF, respectively, for studying the influence of coordination environment of cobalt active sites on photocatalytic C 2 H 2 reduction. As a result, CoO 4 MOF with O‐coordinated cobalt sites exhibited the highest activity with C 2 H 2 ‐to‐C 2 H 4 yield of 852.68 µmol g −1 h −1 in C 2 H 2 atmosphere. Interestingly, in simulated industry‐relevant conditions gas with 1% C 2 H 2 contained C 2 H 4 mixture, CoN 4 MOF showed the optimal performance with near 100% conversion of low‐concentrated C 2 H 2 . The photophysical, C 2 H 2 adsorption characterization, in situ FTIR, and density functional theory (DFT) calculation were conducted to investigate the reaction mechanism. The results demonstrated that the O‐coordinated Co sites behaved more favorably thermodynamically for *C 2 H 2 ‐to‐*CH 2 CH intermediate, which caused superior activity. In contrast, the N‐coordinated Co sites showed highly efficient PAH in C 2 H 4 rich conditions with low concentrated C 2 H 2 due to the weak C 2 H 4 competitive adsorption. This work is the first to explore the dependence of the active site coordination microenvironment for C 2 H 2 photoreduction and provides a platform for constructing highly selective photocatalysts.