Theoretical Insights into CO Oxidation over MOF-808-Encapsulated Single-Atom Metal Catalysts

Metal–organic framework (MOF)-encapsulated single-atom metal catalysts (SACs), as a bridge between homogeneous and heterogeneous catalysts, have received extensive attention from both fundamental and applied perspectives in recent years. Herein, the CO oxidation reaction mechanism and kinetics over a series of MOF-808-encapsulated SACs (MOF-808-MII, M = Zn, Cu, Fe, Pd, Ni, and Pt) were studied using density functional theory calculations and microkinetic modeling analysis. First, it has been found that the stability of single-atom metal ions at the Zr metal node follows the trend of PtII > NiII > PdII > FeII > CuII > ZnII. Four possible reaction routes, that is, Langmuir–Hinshelwood (LH) mechanism, Eley–Rideal mechanism, CO oxidation with the μ3-O site, and the hydroxyl group over MOF-808-PtII, were systematically investigated. The LH mechanism is the most favorable CO oxidation route, in which the first CO oxidation step is the kinetically relevant step over MOF-808-PtII. Using the energetic span model, the relative turnover frequencies of CO oxidation over MOF-808-MII were calculated, indicating that the MOF-808-PtII catalyst is the most active catalyst among six MOF-808-MII catalysts.