Nanocrystalline\nHigh-Dimensional Nb<sub>2</sub>O<sub>5</sub> for Efficient Electroreductive\nDicarboxylation of CO<sub>2</sub> with Cycloalkane

The electrocarboxylation of C–C single bonds using\nCO<sub>2</sub> under ambient conditions is a promising strategy for\nsynthesizing\ndiacids, which have significant applications in polymer and biomedical\nsectors. In this study, we present the development of nanocrystalline\nNb<sub>2</sub>O<sub>5</sub> featuring a high-dimensional structure\n(Nb<sub>2</sub>O<sub>5</sub>–HD) that enables the efficient\ndicarboxylation of CO<sub>2</sub> with cycloalkanes under mild conditions.\nUtilizing commercially available, unactivated diethyl cyclopropane-1,2-dicarboxylate\nas a model substrate, we achieved an impressive average yield of approximately\n94%, with an 88% yield demonstrated in a gram-scale experiment. Notably,\nNb<sub>2</sub>O<sub>5</sub>–HD maintained its structure and\nperformance after 100 h of continuous operation, highlighting its\nlong-term stability. <i>In situ</i> mechanistic investigations\nelucidated the reaction pathway, revealing that the CO<sub>2</sub> radical anion (CO<sub>2</sub><sup>•–</sup>) serves\nas an essential intermediate driving the reaction rather than cycloalkane\nadsorption onto the cathode. Besides, the high-dimensional structure\nand abundant crystal defects of Nb<sub>2</sub>O<sub>5</sub>–HD\nexhibit a greater number of acid sites, which is advantageous for\nthe generation and stabilization of the CO<sub>2</sub><sup>•–</sup>. These findings underscore the potential of Nb<sub>2</sub>O<sub>5</sub>–HD as a robust catalyst for CO<sub>2</sub> conversion,\npaving the way for advancements in organic electrosynthesis.