Direct catalytic hydrogenation of CO₂ to formate over a Schiff-base-mediated gold nanocatalyst

Catalytic transformation of CO₂ to formate is generally realized through bicarbonate hydrogenation in an alkaline environment, while it suffers from a thermodynamic sink due to the considerable thermodynamic stability of the bicarbonate intermediate. Here, we devise a route for the direct catalytic conversion of CO₂ over a Schiff-base-modified gold nanocatalyst that is comparable to the fastest known nanocatalysts, with a turnover number (TON) of up to 14,470 over 12 h at 90 °C. Theoretical calculations and spectral analysis results demonstrate that the activation of CO₂ can be achieved through a weakly bonded carbamate zwitterion intermediate derived from a simple Lewis base adduct of CO₂. However, this can only occur with a hydrogen lacking Lewis base center in a polar solvent. This finding offers a promising avenue for the direct activation of CO₂ and is likely to have considerable implications in the fields of CO₂ conversion and gold catalytic chemistry.