Photocatalytic CH4 Upgrading to Multicarbon Products

Methane is both a greenhouse gas and an abundant C₁ fuel resource that exists in nature. The selective photocatalytic upgrading of methane into multicarbon (C₂₊) chemicals can both mitigate the greenhouse effect and promote the utilization and value of methane, in which the C–C coupling step is key to the production of multicarbon products. Achieving this targeted upgrading under ambient temperature and pressure conditions requires efficient activation of the C–H bonds in methane as well as the balancing of the adsorption and desorption of various free radicals and C₁ intermediates to facilitate efficient C–C coupling. In this Review, we delve into the recent advances in the photocatalytic upgrading of methane to C₂₊ products. The importance of catalyst design, including the active site assembly, crystal surface, and valence reconstruction, is first emphasized. Then, we discuss how coreactants such as carbon dioxide and carbon monoxide can be introduced to enhance the carbon chain growth pathways. Furthermore, we also summarize the developments of looping systems and photoelectrocatalysis. Finally, we conclude with an outlook for the future advancement in this photocatalytic methane upgrading field. This Review aims to provide a general framework for investigating photocatalytic methane C–C coupling reactions toward multicarbon products, thereby suggesting future research directions toward environmentally friendly and efficient methane upgrading strategies.