Ruthenium Complexes/Ionic Liquids as an Efficient Catalytic System for Hydrogen Generation from Formic Acid Dehydrogenation

However, despite its considerable potential, most catalytic systems reported for FA dehydrogenation still suffer from significant drawbacks, including the reliance on volatile solvents and additives, harsh reaction conditions, and inert atmospheres. These limitations hinder the practical implementation, economic viability, and large-scale deployment of FA-based hydrogen storage and release technologies. In this work, we evaluated a series of ruthenium complexes, including [RuCl₂(p-cymene)]₂, Ru-MACHO, [RuCl₂(PPh₃)₃], cis-[RuCl₂(dppb)(bipy)], cis-[RuCl₂(dppb)(phen)], and cis-[RuCl₂(dppm)₂], as precatalysts for FA dehydrogenation using ionic liquids (ILs) as reaction additives. Under the initial reaction conditions (FA = 3 mmol, [Ru] = 3 μmol, BMMIm.OAc = 1.5 mmol, 80 °C), cis-[RuCl₂(dppm)₂] exhibited the highest catalytic activity among the evaluated complexes, achieving >99% conversion within 15 min. After optimization of the reaction conditions, the cis-[RuCl₂(dppm)₂]/EMIm.OAc catalytic system achieved a turnover frequency (TOF) of 42,779 h⁻¹ at 80 °C with >99% conversion (FA = 3 mmol, [Ru] = 1.5 μmol, [IL] = 1.5 mmol).