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Gas-Phase Reactions of Carbon Dioxide with Copper Hydride Anions Cu2H2–: Temperature-Dependent Transformation C

Liu, Yun-Zhu, Jiang, Li-Xue, Li, Xiao-Na, Wang, Li-Na, Chen, Jiao-Jiao, He, Sheng-Gui
Journal of physical chemistry 2018 v.122 no.34 pp. 19379-19384
ambient temperature, anions, carbon dioxide, chemical bonding, density functional theory, formates, gases, hydrides, hydrogenation, mass spectrometry, models, value added
The hydrogenation of carbon dioxide into value-added chemicals is of great importance for CO₂ recycling. However, the underlying mechanism of CO₂ hydrogenation remains elusive owing to the lack of experimental evidence for the formation of the C–H bond. Herein, the gas-phase reaction of copper hydride anion Cu₂H₂– with CO₂ at variable temperatures (∼300–560 K) was investigated. Metal hydrides are the ideal models to study the nature of C–H bond formation in CO₂ hydrogenation, while the related studies are scarcely reported, particularly for the hydrogenation reactions at temperatures above 300 K. The generation of formate (HCO₂–) attached on product CuH₂CO₂– was identified by temperature-dependent mass spectrometric experiments and density functional theory calculations. Temperature played crucial roles to fine-tune the product selectivity, from Cu₂H₂CO₂– that dominates the room-temperature reaction into CuH₂CO₂– at elevated temperatures. The nature behind the temperature-dependent product selectivity and the mechanism of CO₂ hydrogenation has been interpreted by using theoretical calculations. The combined experimental and computational studies have provided solid evidence for the formation of formate attached in CuH₂CO₂–.