Atomically Precise Single-Site Pt Catalyst via Dual-Confinements for Enhanced Low-Temperature Exhaust Oxidation

Developing single-site catalysts (SSCs) with thermal stability and high activity towards exhaust oxidation is crucial yet challenging, due to sintering at severe reaction temperature and limited activity. Here, we report a Pt SSC with atomic-precision structures confined by both polyoxometalate (POM) and Zr-based Metal-Organic Frameworks (MOF) NU1K, exhibits high oxidation activity and stability towards exhaust oxidation. Difference envelope density (DED) and pair distribution function (PDF) analyses showed that isolated PtV9O28 clusters are well-maintained in the c-pores of NU1K. The node-bound formate facilitates partial reduction of isolated Pt (IV) species in single crystals to Pt (II) species in isolated PtV9O28 clusters after encapsulation in NU1K with the generation of oxygen vacancy as demonstrated by 1H Nuclear Magnetic Resonance (NMR) and X-ray Photoelectron Spectroscopy (XPS). When the simultaneous oxidation of CO, C3H6, and C3H8 was performed on these fully exposed single-Pt sites, the T100 (temperature at 100% conversion) for CO and C3H6 oxidation significantly decreased by 100 °C on PtV9O28@NU1K compared to that of PtV9O28/ZrO2. Meanwhile, it completely oxidizes C3H8 at 260 °C, but C3H8 oxidation does not occur on PtV9O28/ZrO2 until 470 °C. Theoretical calculation shows C3H8 molecules are easily absorbed to Pt sites on isolated PtV9O27 cluster with the adsorption energy of -1.84eV. These molecularly defined SSCs structures facilitate understanding the origins of catalyst activity and designing fully dispersed catalysts with maximum atom efficiency.