Passivating Lattice Oxygen in ZnO Nanocrystals to Reduce its Interactions with the Key Intermediates for a Selective Photocatalytic Methane Oxidation to Methanol.

An inevitable overoxidation process is considered as one of the most challenging problems in the direct conversion of methane (CH) to methanol (CHOH), which is limited by the uncontrollable cracking of key intermediates. Herein, we have successfully constructed a photocatalyst, the Fe-doped ZnO hollow polyhedron (Fe/ZnOHP), for the highly selective photoconversion of CH to CHOH under mild conditions. In situ experiments and density functional theory calculations confirmed that the introduction of Fe was able to decrease the energy level of the O 2p orbital, which passivated the activity of lattice oxygen in ZnO nanocrystals. This passivation effect greatly weakened the interaction between *CH and lattice oxygen, thus facilitating the conversion of *CHO to *CH intermediate rather than the direct desorption of *CHO. As a result, Fe/ZnOHP exhibited excellent CHOH generation rate (ca. 1009 μmol g  h) and selectivity (ca. 96 %) in the photocatalytic conversion of CH at room temperature and low pressure.