Ce-Doped NiO aerogel with hierarchical porosity and abundant oxygen vacancies for enhanced CO₂ cycloaddition to epoxides

The cycloaddition of CO₂ with epoxides to form value-added cyclic carbonates has attracted increasing interest as a promising carbon utilization route. While metal oxides are cost-effective and stable, their typically low surface areas and acid-base characteristics have limited their use as efficient catalysts in this reaction. In this study, we report a rationally engineered metal oxide aerogel catalyst based on Ce-doped NiO (NCA), synthesized via an epoxide-assisted sol–gel method followed by supercritical CO₂ drying. The incorporation of cerium with a targeted Ni:Ce molar ratio of 9:1 resulted in highly uniform doping throughout the NiO matrix, significantly enhancing its porous structure, with a BET surface area of 561 m²·g⁻¹ and pore volume of 3.3 cm³·g⁻¹. Ni species function as Lewis acid sites to activate epoxides, while abundant oxygen vacancies introduced by Ce doping provide Lewis base sites for CO₂ adsorption. The NCA exhibited outstanding catalytic activity for CO₂ cycloaddition, surpassing previously reported metal oxide-based catalysts. Under mild conditions (80 °C, 0.1 MPa, 4 h) and with a minimal amount of co-catalyst, >98 % conversion was achieved across a range of epoxides, including bulky substrates. The catalyst maintained high activity in the presence of 20 mol% moisture and showed excellent recyclability over five cycles without performance degradation. These results demonstrate the practical applicability of NCA as a robust, solvent-free, and scalable catalyst for efficient CO₂ utilization, and provide a design strategy for engineering porous oxide catalysts tailored for industrial carbon utilization processes.