Site‐Specific Molecular Engineering Redirects Radical Pathways for Selective Photocatalytic Coupling of Methane to C 2+ Hydrocarbons

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ABSTRACT Toward carbon neutrality, multi‐carbon synthesis from photo‐driven oxidative coupling of CH 4 (POCM) remains a formidable challenge due to the activity‐selectivity trade‐off, originating from sluggish surface reaction kinetics and uncontrolled reactive radical reactions. Herein, alkyl thiols (C 9 SH) were site‑specifically grafted onto Au sites supported on planar TiO 2 , forming the archetypal C 9 S‐Au δ+ /Au/TiO 2 system featuring covalent gold‐thiolate interplay. Combined experimental and theoretical analyses revealed that covalent Au‐thiolate interaction could modulate the interfacial electronic structure and upshift the d ‑band center of Au sites, thereby strengthening *CH 3 adsorption and lowering the C─C coupling barrier, thus suppressing the · O 2 − ‐driven overoxidation. Moreover, the reconstructed C 9 S‐Au δ+ sites acted as rapid electron extraction channels, drawing electrons from adjacent Au nanoparticles and preserving long‐lived photogenerated holes for C─H activation. Meanwhile, the alkyl chains served as “molecular fences”, effectively promoting local CH 4 enrichment and stabilizing *CH 3 intermediates. The optimized C 9 S‐Au δ+ /Au/TiO 2 photocatalyst exhibited an excellent yield of 22.92 mmol g cat −1 h −1 for C 2+ products with 93.9% selectivity, ranking it among the state‐of‐the‐art noble‐metal‐loaded photocatalysts for POCM. This work establishes site‐specific molecular engineering as an effective strategy to regulate interfacial charge redistribution and redirect radical coupling pathways, enabling CH 4 conversion to multi‐carbon products with enhanced activity and selectivity simultaneously.