Nanocrystalline High-Dimensional Nb₂O₅ for Efficient Electroreductive Dicarboxylation of CO₂ with Cycloalkane

The electrocarboxylation of C–C single bonds using CO2 under ambient conditions is a promising strategy for synthesizing diacids, which have significant applications in polymer and biomedical sectors. In this study, we present the development of nanocrystalline Nb2O5 featuring a high-dimensional structure (Nb2O5–HD) that enables the efficient dicarboxylation of CO2 with cycloalkanes under mild conditions. Utilizing commercially available, unactivated diethyl cyclopropane-1,2-dicarboxylate as a model substrate, we achieved an impressive average yield of approximately 94%, with an 88% yield demonstrated in a gram-scale experiment. Notably, Nb2O5–HD maintained its structure and performance after 100 h of continuous operation, highlighting its long-term stability. In situ mechanistic investigations elucidated the reaction pathway, revealing that the CO2 radical anion (CO2•–) serves as an essential intermediate driving the reaction rather than cycloalkane adsorption onto the cathode. Besides, the high-dimensional structure and abundant crystal defects of Nb2O5–HD exhibit a greater number of acid sites, which is advantageous for the generation and stabilization of the CO2•–. These findings underscore the potential of Nb2O5–HD as a robust catalyst for CO2 conversion, paving the way for advancements in organic electrosynthesis.