Mechanistic Control of C─H Bond Activation and C─C Coupling in Light‐Driven Methane Conversion to C 2 + Products over Multifunctional Photocatalysts

Methane, the most abundant hydrocarbon resource on Earth, represents a highly attractive and sustainable feedstock for the solar‐driven production of fuels and value‐added chemicals. However, achieving both efficient and selective C 2+ synthesis remains a formidable challenge. The difficulties lie in realizing advanced photocatalytic materials for controlled activation of the thermodynamically stable C─H bonds and directing the complex network of competing reaction pathways toward selective C─C coupling under both oxidative and non‐oxidative conditions. In this review, we systematically elucidate the central scientific challenges associated with photocatalytic methane upgrading to C 2+ products within a unified mechanistic framework that integrates C─H bond activation, formation and evolution of intermediates, C─C coupling, together with their competing overoxidation and coking pathways, while correlating advances in material design and reaction engineering. Furthermore, we highlight the growing importance of multifunctional materials and hybrid systems that integrate photonic excitation with thermal and electrical inputs to overcome the intrinsic kinetic and energetic limitations of conventional methane photocatalysis. At last, it is emphasized that an interdisciplinary map, encompassing material synthesis, semiconductor physics and chemistry, surface science, catalysis, reaction engineering, advanced characterization, and mechanism investigation, is essential for advancing selective and sustainable methane transformation to high‐value C 2+ products.