Studying the cleavage of the C═O bond during CO₂ activation at room temperature is highly significant for comprehending the CO₂ conversion processes. Herein, mass spectrometry experiments and density functional theory calculations indicate that the niobium carbide anions Nb₃C₄^– can continuously convert five CO₂ molecules to CO under thermal collision conditions, while the other clusters with less carbon ligands Nb₃C_1–3^– reduce fewer CO₂ molecules. Size-dependent reactivity of Nb₃C_1–4^– cluster anions toward CO₂ is observed. Interestingly, the carbon atoms in Nb₃C₄^– not only act as highly active adsorption sites for CO₂ but also serve as electron donors to reduce CO₂. The stored electrons are released through a carbon–carbon coupling process. Our findings on the role of carbon ligands in enhancing transition metal carbide reactivity can offer new insights for designing active sites on catalysts with both high activity and selectivity.

中文翻译：

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气相碳化铌簇阴离子 Nb3C4– 连续还原五个二氧化碳分子：碳配体增强反应性的不寻常机制

研究室温下CO ₂活化过程中C=O键的断裂对于理解CO ₂转化过程具有重要意义。其中，质谱实验和密度泛函理论计算表明，碳化铌阴离子Nb ₃ C ₄ ^–在热碰撞条件下可以连续将5个CO ₂分子转化为CO，而其他碳配体较少的团簇Nb ₃ C _1–3 ^–减少更少的CO ₂分子。观察到Nb ₃ C _1–4 ^-簇阴离子对 CO ₂的尺寸依赖性反应性。有趣的是，Nb ₃ C ₄中的碳原子^不仅充当CO ₂的高活性吸附位点，而且还充当还原CO ₂的电子供体。储存的电子通过碳-碳耦合过程释放。我们关于碳配体在增强过渡金属碳化物反应活性方面的作用的发现可以为设计具有高活性和选择性的催化剂活性位点提供新的见解。