Catalytic Systems for the Effective Fixation of CO2 into Epoxidized Vegetable Oils and Derivates to Obtain Biobased Cyclic Carbonates as Precursors for Greener Polymers

The chemical fixation of carbon dioxide by cycloaddition to biobased epoxides, e.g., vegetable oils, fatty acids, etc., is an efficient, sustainable, and clean strategy to obtain biobased cyclic carbonates. These can be used as feedstocks for the synthesis of environmentally friendly biobased polymers as an alternative to polymers used in daily life such as polyurethanes (PUs) and/or polycarbonates (PCs). Nevertheless, this reaction is not trivial at all due to both the low reactivity of the CO2 molecule and the nature of the needed substrates (biobased epoxides) where the epoxide groups are internal and sterically hindered, hampering the CO2 cycloaddition reaction. Therefore, the design of efficient catalytic systems to overcome these hurdles is mandatory. Most of the catalytic systems developed for this transformation aim to facilitate the rate-determining step in the CO2 cycloaddition catalytic cycle. They comprise an ionic liquid or an ionic compound with a nucleophilic anion alone or in the presence of a cocatalyst to assist the epoxide ring-opening. The most commonly used catalyst is tetrabutylammonium bromide [TBA][Br] ionic liquid, but other ammonium-, phosphonium-, and sulfonium-based ionic liquids in combination or not with a cocatalyst have also been disclosed in the literature. This Review presents a structured overview of the reported catalytic systems, both homogeneous and heterogeneous catalysts, employed in the transformation of any epoxidized vegetable oil or derivates into biobased carbonated materials. The different catalytic systems have been discussed and compared in terms of catalytic performance, employed substrates, and reaction conditions.