Ce-Doped Nio Aerogel with Hierarchical Porosity and Abundant Oxygen Vacancies for Enhanced Co2 Cycloaddition to Epoxides

Abstract

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, theire 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 resulting NCA features a hierarchical porous structure with a high surface area (561 m2·g–1) and pore volume (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 oC, 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 potential of NCA as a robust and scalable catalyst for solvent free, energy-efficient CO2 conversion. These results highlight the practical applicability of NCA as a scalable, solvent-free catalyst for efficient CO2 utilization, and provide a design strategy for engineering porous oxide catalysts tailored for industrial carbon utilization processes.

Keywords: CO2 fixation, CO2 cycloaddition, Synergistic mechanism, Oxygen vacancy, Metal oxide aerogel