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Photocatalytic conversion of methane (CH 4 ) to ethane (C 2 H 6 ) has attracted extensive attention from academia and industry. Typically, the traditional oxidative coupling of CH 4 (OCM) reaches a high C 2 H 6 productivity, yet the inevitable overoxidation limits the target product selectivity. Although the traditional nonoxidative coupling of CH 4 (NOCM) can improve the product selectivity, it still encounters unsatisfied activity, arising from being thermodynamically unfavorable. To break the activity-selectivity trade-off, we propose a conceptually new mechanism of H 2 O 2 -triggered CH 4 coupling, where the H 2 O 2 -derived ·OH radicals are rapidly consumed for activating CH 4 into ·CH 3 radicals exothermically, which bypasses the endothermic steps of the direct CH 4 activation by photoholes and the interaction between ·CH 3 and ·OH radicals, affirmed by in situ characterization techniques, femtosecond transient absorption spectroscopy, and density-functional theory calculation. By this pathway, the designed Au-WO 3 nanosheets achieve unprecedented C 2 H 6 productivity of 76.3 mol mol Au -1 h -1 with 95.2% selectivity, and TON of 1542.7 (TOF = 77.1 h -1 ) in a self-designed flow reactor, outperforming previously reported photocatalysts regardless of OCM and NOCM pathways. Also, under outdoor natural sunlight irradiation, the Au-WO 3 nanosheets exhibit similar activity and selectivity toward C 2 H 6 production, showing the possibility for practical applications. Interestingly, this strategy can be applied to other various photocatalysts (Au-WO 3 , Au-TiO 2 , Au-CeO 2 , Pd-WO 3 , and Ag-WO 3 ), showing a certain universality. It is expected that the proposed mechanism adds another layer to our understanding of CH 4 -to-C 2 H 6 conversion.

The huge challenge for CH 4 photooxidation into CH 3 OH lies in the activation of the inert C-H bond and the inhibition of CH 3 OH overoxidation. Herein, we design two-dimensional in-plane Z -scheme heterostructures composed of two different metal oxides, with efforts to polarize the symmetrical CH 4 molecules and strengthen the O-H bond in CH 3 OH. As a prototype, we first fabricate ZnO/Fe 2 O 3 porous nanosheets, where high-resolution transmission electron microscopy and in situ X-ray photoelectron spectroscopy affirm their in-plane Z -scheme heterostructure. In situ Fourier transform infrared spectra and in situ electron paramagnetic resonance spectra demonstrate their higher amount of ·CH 3 radicals relative to the pristine ZnO porous nanosheets, in which density functional theory calculations validate that the high local charge accumulation on Fe sites lowers the CH 4 adsorption energy from 0.14 to 0.06 eV. Moreover, the charge-accumulated Fe sites strengthen the polarity of the O-H bond in CH 3 OH through transferring electrons to the O atoms, confirmed by the increased barrier from 0.30 to 2.63 eV for *CH 3 O formation, which inhibits the homolytic O-H bond cleavage and thus suppresses CH 3 OH overoxidation. Accordingly, the CH 3 OH selectivity over ZnO/Fe 2 O 3 porous nanosheets reaches up to nearly 100% with an activity of 178.3 μmol -1 g cat -1 , outperforming previously reported photocatalysts without adding any oxidants under room temperature and ambient pressure.