Low-Temperature Oxidation of Simulated Diesel Exhaust Catalyzed by Polyoxovanadate Clusters Stabilized in the Metal-Organic Framework NU-1000

Developing catalysts with thermal stability and high activity toward exhaust oxidation is crucial yet challenging with standard heterogeneous catalysts, due to limited catalytic activity and due to catalyst sintering at high reaction temperature. Here, we report that a Pt SAC (single-metal atom-catalyst) sited/confined in atomically precise fashion, first by polyoxovanadate (POV) cluster and secondly by a crystalline, Zr-based metal-organic framework (MOF) NU1K, exhibits high oxidation activity and stability towards exhaust oxidation. Simultaneous air oxidation of CO, C3H6, and C3H8 is readily thermally catalyzed by fully exposed single-Pt sites. Indeed, values for T100 (temperature at 100% conversion) for oxidation of CO and C3H6 are ca. 100 °C lower on PtV9O28@NU1K compared to PtV9O28 on zirconia. PtV9O28@NU1K completely oxidizes C3H8 at 260 °C, but on PtV9O28/zirconia C3H8 oxidation does not occur on until 470 °C. Theoretical calculations show that, in the presence of oxygen vacancies, C3H8 molecules are easily adsorbed at Pt sites on isolated PtV9O27 clusters with adsorption energy of -1.84 eV. Studies with structurally well-defined, MOF-enshrouded, SACs in clusters can facilitate: a) understanding the origins of catalyst activity and b) designing fully dispersed catalysts with maximum atom efficiency.