Chlorine Radical‐Mediated Photocatalytic C─C Coupling of Methanol to Ethylene Glycol with Near‐Unity Selectivity

Abstract

Abstract The selective activation of inert C─H bonds in methanol under mild conditions to synthesize high‐value C 2 products remains a formidable challenge, primarily due to the competing high reactivity of O─H bonds. Herein, we pioneer a chlorine radical‐mediated strategy to redirect the photocatalytic reaction pathway for methanol conversion toward ethylene glycol (EG). Efficient C─H bond activation is achieved by constructing a Z‐scheme heterojunction photocatalyst (ZnIn 2 S 4 /TiO 2 ‐Cl) composed of chlorinated TiO 2 (TiO 2 ‐Cl) and ZnIn 2 S 4 with efficient charge separation. Photogenerated holes in this system preferentially oxidize surface‐adsorbed Cl − to chlorine radicals (Cl•). These radicals drive a thermodynamically favorable hydrogen atom transfer via hydrogen abstraction, cleaving the C─H bond of methanol to form hydroxymethyl radicals (•CH 2 OH). Subsequent C─C coupling of •CH 2 OH intermediates, synergistically combined with a self‐sustaining Cl − /Cl• cycle, produces EG with exceptional selectivity (96.7%) and yield (21.6 mmol g −1 ) while suppressing overoxidation. In contrast, nonchlorinated catalysts predominantly utilize photogenerated holes for O─H bond cleavage under identical conditions, yielding only C 1 products (HCHO, HCOOH). This work not only establishes a solar‐driven approach for methanol valorization but also advances mechanistic insights into radical‐mediated pathway control in heterogeneous photocatalysis.