Cubic platinum nanoparticles capped with Cs2[closo-B12H12] as an effective oxidation catalyst for converting methane to ethanol.

ABSTRACT

Direct conversion of methane to alcohol remains a key challenge. Here, we report a novel aqueous catalyst, cubic platinum (Pt) nanoparticles capped with Cs2[closo-B12H12], capable of direct oxidation of methane to ethanol and methanol with H2O2 and O2 under facile conditions. The selective conversion to ethanol exceeded 97% with a yield reaching 148.41 mol·kgcat-1·h-1 at 50 °C. Experiments with 5,5'-dimethy1-1-pyrroline-N-oxide (DMPO) and electron paramagnetic resonance (EPR) tests revealed that methane oxidation occurred via free-radical chain reactions involving CH3, CH3CH2, and HO radicals. Theoretical analysis suggested that the {1 0 0} surface of the Pt nanoparticles was capped with Cs2[closo-B12H12] mediated by Pt-B bonds with a binding energy of -278.6 kcal/mol. This promoted the growth of particles along the direction of the (1 0 0) facets and finally formed a cubic structure. The EPR tests combined with theoretical calculations confirmed the hypothesis that methane-ethane-ethanol conversion was mediated by the catalyst by employing the features of nano-platinum and Cs2[closo-B12H12], on which only C1 and C2 products were generated, while no products with three or more carbon atoms were detected in the reaction systems described above.