Direct Oxidation of Methane to Formaldehyde With Molecular Oxygen Catalyzed by Gold‐Tungsten Oxide Cluster Cations

Abstract

ABSTRACT Catalytic direct oxidation of methane with molecular oxygen can be highly exothermic in thermodynamics. It offers a promising green method for production of value‐added chemicals such as formaldehyde (CH 2 O), an indispensable feedstock in industry, under mild conditions. However, it faces a long‐standing grand challenge due to the intrinsic kinetic inertness of methane. Herein, an active gold‐tungsten oxide cluster catalyst, AuWO 2 + , being able to spontaneously catalyze CH 4 + O 2  → CH 2 O + H 2 O at room temperature has been successfully identified by mass spectrometry, which is distinctly different from the related condensed phase catalysis wherein the photo‐excitation of catalysts in the presence of H 2 O or H 2 was prerequisite to initiate catalytic reactions. The previously unrecognized mechanisms of direct methane oxidation have been unveiled: the interfacial Au−metal centers can undergo thermal reaction with O 2 to spontaneously generate the active (O···O) −• hole that subsequently works together with Au atom in a relay‐manner to easily cleave two C−H bonds of methane directional for CH 2 O and H 2 O production. This finding lays a solid foundation for future design of better‐performing catalysts for direct oxidation of methane (or other molecules) with O 2 without the need of any external energy or co‐feeding with alien molecules.