Metal-Free Bifunctional N-Heterocyclic Catalysts for CO2 Cycloaddition to Three-Membered Rings

The development of sustainable strategies for carbon dioxide valorization is essential to achieve climate neutrality. Among nonreductive CO2 conversion routes, the cycloaddition of CO2 to epoxides and aziridines represents an atom-efficient approach for the synthesis of cyclic carbonates and oxazolidinones, valuable compounds with significant industrial, technological, and pharmaceutical relevance.While metal-based catalysts have been extensively investigated, metalfree systems are promising alternatives owing to their lower environmental impact, reduced cost, and potential to operate under mild conditions. This review summarizes recent literature (2020-present) on the use of homogeneous bifunctional metal-free catalysts bearing N-heterocyclic moieties for CO2 cycloaddition to three-membered rings.