Recent Advances in Activation of Aryl Halides over Organic and MOF-Based Semiconductor Photocatalysts: Mechanisms, Strategies, and Challenges

Abstract Photocatalytic aryl halide activation enables carbon-halogen (C−X) bond functionalization for synthetic chemistry yet faces inherent thermodynamic and kinetic challenges of cleaving inert C−X bonds. Organic semiconductors (OSCs) and MOF-based semiconductor (MOFs) photocatalysts offer tunable optoelectronic properties and diverse active sites to address these challenges. This review systematically elucidates key mechanisms in OSCs/MOFs-mediated transformations, including conduction-band electron reduction, consecutive photoinduced electron transfer process, and cooperative pathways involving metal-aryl intermediates, hydrides, and radicals. We further examine how structural engineering of OSCs and MOFs—through molecular assembly, polymerization, and porous frameworks—regulates light absorption, charge separation and migration, and active-site exposure. The roles of specific active sites, such as radical anions, excited-state radical anions, and mono-/bimetallic centers, are highlighted in governing reactivity and selectivity. Finally, we present critical insights into catalyst design, mechanistic elucidation, and future directions toward activating inert bonds, applying systems to complex molecules, and advancing efficient and scalable photocatalytic platforms for chemical synthesis.