Unlocking Key Intermediates in Copper-Catalyzed CO2 to Methanol Conversion

Although copper catalysts have been widely employed in various catalytic transformations, their potential for converting CO₂ to methanol remains largely unexplored to date. Herein, it is reported that a copper(I) salt efficiently converts CO₂ into methanol equivalent in the presence of NaBH₄ and an amide ligand (L1) under mild reaction conditions. The in situ generated active catalyst in the reaction is isolated as a single crystal and the structure solution reveals the formation of a reactive two-coordinate Cu(I) dimeric catalyst [Li₂(THF)₄Cu(L1)₄] (1). The key transient species “copper-hydride” responsible for the CO₂ to methanol equivalent via [1-BX₄]⁻ (where X = H or D) adduct formation is indirectly confirmed through NMR spectroscopy. The copper catalyst (1) shows a remarkable TON (3993) and TOF (166 h⁻¹) and remains active for more than 7 cycles with an overall TON of 10199. The mechanistic studies, supported by the characterization of key intermediates, provide a plausible pathway for this transformation.