Selectivity Switching of CO₂ Hydrogenation from HCOOH to CO with an In Situ Formed Ru–Li Complex

Herein, we report the role of alkali halide salt in regulating the pathway of CO₂ hydrogenation in the presence of Shvo’s complex. Particularly, the collaboration of Shvo’s complex with LiCl exhibited as a highly efficient catalyst for CO₂ hydrogenation to CO instead of the kinetically favorable product HCOOH under mild conditions. The reaction can be initiated at 45 °C with CO as the dominant product, and the rate of CO formation was almost 80 times to that in the absence of LiCl at 60 °C. Under optimized conditions, the TON_CO could reach 1555 at 160 °C, much higher than the reported results of the most efficient Ru-based homogeneous catalyst. Density functional theory calculations demonstrated that the cooperation of the alkali cation and chloride anion contributed to reducing the energy barrier of CO₂ activation to form the key Ru–CO₂H intermediate. An in situ formed mixed Ru–Li complex (5) has been characterized by X-ray crystallography, highlighting the indispensability of electrostatic interactions between LiCl and Shvo’s complex for enhanced reactivity and altered selectivity.