Direct C–C Coupling of CO2 and the Methyl Group from CH4 Activation through Facile Insertion of CO2 into Zn–CH3 σ-Bond

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• 作者：Yuntao Zhao ; Chaonan Cui ; Jinyu Han ; Hua Wang ; Xinli Zhu ; Qingfeng Ge
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：August 17, 2016
• 年：2016
• 卷：138
• 期：32
• 页码：10191-10198
• 全文大小：578K
• 年卷期：0
• ISSN：1520-5126

文摘

Conversion of CO₂ and CH₄ to value-added products will contribute to alleviating the green-house gas effect but is a challenge both scientifically and practically. Stabilization of the methyl group through CH₄ activation and facile CO₂ insertion ensure the realization of C–C coupling. In the present study, we demonstrate the ready C–C coupling reaction on a Zn-doped ceria catalyst. The detailed mechanism of this direct C–C coupling reaction was examined based on the results from density functional theory calculations. The results show that the Zn dopant stabilizes the methyl group by forming a Zn–C bond, thus hindering subsequent dehydrogenation of CH₄. CO₂ can be inserted into the Zn–C bond in an activated bent configuration, with the transition state in the form of a three-centered Zn–C–C moiety and an activation barrier of 0.51 eV. The C–C coupling reaction resulted in the acetate species, which could desorb as acetic acid by combining with a surface proton. The formation of acetic acid from CO₂ and CH₄ is a reaction with 100% atom economy, and the implementation of the reaction on a heterogeneous catalyst is of great importance to the utilization of the greenhouse gases. We tested other possible dopants including Al, Ga, Cd, In, and Ni and found a positive correlation between the activation barrier of C–C coupling and the electronegativity of the dopant, although C–H bond activation is likely the dominant reaction on the Ni-doped ceria catalyst.