Photocatalytic conversion of methane: Catalytically active sites and species

The development of direct routes for catalytic functionalization of methane would accelerate the chemical utilization of this abundant carbon resource to produce value-added chemicals or easily trans-portable fuels. However, the selective transformation of methane remains highly challenging due to the dilemma between the activa-tion of inert C -H bond and the keeping of vulnerable target prod-ucts from over-oxidation or deep dehydrogenation. A number of studies have been devoted to selective methane transformations by heterogeneous photocatalysis. Unlike a comprehensive review of the field, this article focuses on the insights into the catalytically active sites/species, which are usually overlooked in photocatalysis, and offers the strategies that may facilitate selective methane conversions by manipulating the active sites/species at surface/ interface regions. The key factors that determine not only the C -H activation but also the selectivity control are discussed. The future opportunities for photocatalytic methane conversions by rationally controlling catalytic active sites/species are analyzed.