Selective CO2 hydrogenation to formic acid using ruthenium catalysts and basic ionic liquids as reaction additives

The catalytic hydrogenation of CO₂ to formic acid (FA) was investigated using six ruthenium precatalysts with basic ionic liquids (ILs) as additives. All complexes showed activity, but the cis-[RuCl₂(dppm)₂]/EMIm.OAc system was the most efficient, achieving a TON of 24,502 under optimized conditions (0.66 mmol IL, 0.033 μmol Ru, 30 bar CO₂/H₂, 80 °C, 22 h). Kinetic studies from 60–90 °C yielded an activation energy of 90.9 kJ mol⁻¹, consistent with literature. This system demonstrates remarkable activity at ultralow metal loadings, offering a selective and efficient route for CO₂ conversion to FA under mild conditions, with potential applications in carbon utilization and hydrogen storage.