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.