title: Direct C-C Coupling of CO2 and the Methyl Group from CH4 Activation through Facile Insertion of CO2 into Zn-CH3 σ-Bond.
abstract: 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.
authors.affiliation: Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University , Tianjin 300072, China.
authors.forename: Yuntao
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University , Tianjin 300072, China.|Department of Chemistry and Biochemistry, Southern Illinois University , Carbondale, Illinois 62901, United States.
authors.forename: Chaonan
authors.initials: C
authors.lastname: Cui
authors.affiliation: Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University , Tianjin 300072, China.
authors.forename: Jinyu
authors.initials: J
authors.lastname: Han
authors.affiliation: Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University , Tianjin 300072, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Wang
authors.affiliation: Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University , Tianjin 300072, China.
authors.forename: Xinli
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University , Tianjin 300072, China.|Department of Chemistry and Biochemistry, Southern Illinois University , Carbondale, Illinois 62901, United States.
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Ge