Fabrication of FeO3 sites in FeOx/ZnO for efficient and selective photo-catalytic oxidation of methane to liquid oxygenates

New catalysts and product diversification of direct CH4 conversion remain very challenging in catalysis. Here, we report FeOx/ZnO photo-catalysts for the conversion of CH4 to liquid oxygenates with high yield (4,108 μmol·gcat−1·h−1) and nearly 100% selectivity. Based on the combinative results from X-ray photoelectron spectroscopy, X-ray absorption, electron paramagnetic resonance, radical quenching, and theoretical calculations, it is found that, in addition to the activation of CH4 in the liquid phase, the presence of highly dispersed FeO3 motifs in the ZnO lattice facilitates the formation of surface-active O− species; this plays an effective role for CH4 activation to ·CH3 radicals. Meanwhile, HCHO is obtained as the major product in our system, rather than the typically reported CH3OH, and this may offer new opportunities to extend the product structure of CH4 upgrading via tandem catalysis.