Functionalization of ionic liquids for heterogeneous catalysis in CO2 conversion: Cycloaddition of epoxides and hydrogenation

The mitigation of environmental impacts caused by greenhouse gas emissions has become increasingly urgent, and the use of CO₂ as a primary carbon source is an alternative in chemical transformations, including the synthesis of organic carbonates, formic acid, or methanol. This work aims to synthesize ionic liquids from the imidazolium cation family to be used in the cycloaddition of CO₂ with ILs anchored in SiO₂-clay heterostructure, MCM-41 and KIT-6 mesoporous materials, as well as the hydrogenation of CO₂ with ILs added to ruthenium complexes, i.e., two catalytic systems. The most satisfactory result for CO₂ cycloaddition (TON _PC = 226) was obtained using the IL (MeO)₃Sipmim.Cl anchored in SiO₂-clay heterostructure (0.16 mol%) as the catalyst and ZnBr₂ (0.04 mol%) as the co-catalyst. The hydrogenation was conducted with the IL (edaO)₃Sipmim.Cl and the ruthenium complex Ru-PNN were not successful, but with co-catalyst PEHA, formic acid/formamide was produced (TON _Form = 552). The unique catalytic system that showed activity for forming methanol was the commercial Ru-MACHO, Ru-C₂₉H₃₀ClNOP₂, (TON _MeOH = 3.3). These results highlight the potential of ruthenium-based complexes and supported ionic liquids as active systems in CO₂ conversion.