Metal‐Free and Solvent‐Free CO 2 Fixation Into Cyclic Carbonates Catalyzed by a Deferiprone‐Derived Bifunctional System

The chemical fixation of CO2 into cyclic carbonates represents a sustainable approach for carbon utilization. In this study, a series of bifunctional ammonium chelating catalysts (CA1–CA5) was synthesized and evaluated for their ability to catalyze the coupling of epoxides with CO2. The design aimed to integrate a catechol-like portion for epoxide activation with an ammonium halide for ring opening. Among the screened candidates, CA1, derived from the simple salification of the FDA-approved iron chelator deferiprone, emerged as the most effective and synthetically accessible catalyst. Optimization studies demonstrated that the bromide salt (CA1Br) significantly outperforms its chloride counterpart, achieving 100% conversion of styrene oxide under mild conditions (70°C, 4 bar CO2, 6 h) at a 1:5 molar ratio. CA1Br showed higher activity than the commercial catalyst tetrabutylammonium bromide (87% conversion) and proved versatile across a broad range of 12 substrates, particularly those that stabilize incipient carbocations. Furthermore, the catalyst exhibited excellent reusability, maintaining high performance for up to five cycles and allowing easy separation from the reaction mixture. Given its metal-free nature, mild operating conditions, and sustainable precursor, CA1Br represents a competitive and eco-friendly alternative to current industrial catalysts for CO2 fixation.