Cocatalyst-Free Conversion of CO₂ to Cyclic Carbonates Using a Postsynthetically Modified Trifunctional Cu-MOF

Abstract

Carbon capture and conversion (CCC) into value-added products offers a dual benefit of mitigating CO₂ emissions while generating industrially relevant chemicals. The cycloaddition of CO₂ with epoxides to form cyclic carbonates is among the most efficient and sustainable approaches within the CCU framework. Herein, we report a postsynthetically modified Cu(II)-based metal–organic framework (MOF), [Cu(II)-IP-Tz]+Br− (C*), as a fully heterogeneous catalyst for this transformation. The parent MOF [(DMF)Cu(II)-IP-NH₂] (C), synthesized from Cu(II) salt and 5-aminoisophthalic acid (IP-NH2), was functionalized with 5-aminotetrazole (Tz-NH2) moieties and subsequently quaternized with C2H5Br to introduce Br⁻ anion. The resulting material (C*) combines Lewis acidic Cu(II) sites, Lewis basic amino groups, and nucleophilic Br⁻, enabling efficient catalysis under solvent-free and cocatalyst-free conditions at ambient CO₂ pressure. C* not only exhibits a higher CO₂ conversion of 85.4% with styrene oxide but also shows enhanced CO₂ adsorption capacity (0.68 mmol g⁻¹) compared to the unmodified MOF (conversion: 20.4%, CO2 adsorption capacity: 0.19 mmol g⁻¹). Moreover, the catalyst demonstrates a broad substrate scope across various epoxides, underscoring its potential for practical CO₂ fixation. This study emphasizes the significance of targeted postsynthetic modifications in transforming MOFs into complete heterogeneous catalysts with enhanced functionality and markedly improved performance for sustainable CO₂ fixation. © 2025 Wiley-VCH GmbH.