Direct and efficient oxidation of methane to methanol and the related liquid oxygenates provides a promising pathway for sustainable chemical industry, while still remaining an ongoing challenge owing to the dilemma between methane activation and overoxidation. Here, ZnO with highly dispersed dual Au and Cu species as cocatalysts enables efficient and selective photocatalytic conversion of methane to methanol and one-carbon (C1) oxygenates using O 2 as the oxidant operated at ambient temperature. The optimized AuCu−ZnO photocatalyst achieves up to 11225 μmol•g −1 •h −1 of primary products (CH 3 OH and CH 3 OOH) and HCHO with a nearly 100% selectivity, resulting in a 14.1% apparent quantum yield at 365 nm, much higher than the previous best photocatalysts reported for methane conversion to oxygenates. In situ EPR and XPS disclose that Cu species serve as photoinduced electron mediators to promote O 2 activation to • OOH, and simultaneously that Au is an efficient hole acceptor to enhance H 2 O oxidation to • OH, thus synergistically promoting charge separation and methane transformation. This work highlights the significances of co-modification with suitable dual cocatalysts on simultaneous regulation of activity and selectivity.

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As the principal constituent of natural/shale gases, methane (CH 4 ) is a promising industrial feedstock for manufacturing value-added chemicals. [1] However, efficient CH 4 conversion is still of a great challenge owing to its high C-H bond energy (439 kJ mol À1 ), low electron affinity (À1.9 eV), and high ionization energy (12.6 eV). [2] The current industrial CH 4 conversion via dry/steam-reforming [3] and subsequent Fischer-Tropsch synthesis [4] is an energy-intensive and indirect route, where high temperature (>700 °C) is required. [5] Accordingly, direct CH 4 conversion under mild conditions is highly desired.Photocatalysis has emerged as the green pathway to activate CH 4 under mild conditions through the injection of a photoinduced charge carrier instead of thermal energy. [6] The key to efficient photocatalytic CH 4 conversion lies in the development of a suitable photocatalyst. Recently, ZnO loaded with noble metal was reported to convert CH 4 into liquid oxygenates, with oxygen (O 2 ) as the oxidant. [7] Au 1 -BP promoted CH 4 conversion into CH 3 OH with the reactive hydroxyl radicals (OH), which are formed by O 2 with the assistance of water under light irradiation. [8] It is clear that the predominant challenge lies in simultaneous regulation of both activation of CH 4 and selectivity of desired products. Suitable co-catalysts like Au and Pd were reported to be the hole/ electron acceptors to promote charge separation, [9] as well as accelerating H 2 O oxidation and O 2 reduction to generate reactive oxygen species. Such encouraging advances then provide to some extent understanding of both charge dynamics and surface kinetics during photocatalytic CH 4 activation. Besides co-catalysts modification, surface engineering is the other way to promote charge dynamics. [10] It was reported that oxygen vacancies (OVs) and metastable Ti 3þ played a vital role in determining the photocatalytic performance of TiO 2 , especially due to the n-type doping and the improved carrier density. [10c,11] Moreover, interfacial resistance could also be regulated through surface engineering. [12] In parallel, surface kinetics could also be optimized by the introduction of surface defects by providing additional chemical adsorption and reactive sites. [13] Given these aforementioned attractive potentials of co-catalyst and OVs modification, the synergy of both would largely promote charge separation and surface reactions.Besides the design of suitable photocatalysts, reaction conditions including oxidant, solvent, pressure, and reaction time during CH 4 conversion are also important taking into account the reaction kinetics. Though it is difficult to gain an efficient activity due to the low solubility of CH 4 in H 2 O, H 2 O oxidation into •OH radicals was reported to be essential in the activation of CH 4 . [14] Meanwhile, H 2 O could also promote the desorption of the oxygenate products and avoid over-oxidation of CO 2 . [15] In parallel, a high pressure would increase the concentration of reactants, and a long rea...