We have systematically investigated the CO2 adsorption performance and microscopic mechanism of N,N-dimethylethylenediamine (mm-2) appended M2(dobpdc) (dobpdc4- = 4,4′-dioxidobiphenyl-3,3′-dicarboxylate; M = Mg, Sc-Zn) with density functional theory. These calculations show that the mm-2 has strong interactions with the open metal site of these structures via the first amine, and the mm-2 binding energies are generally between 123 and 172 kJ/mol. After the CO2 is attached, the ammonium carbamate molecule is created by insertion. The CO2 adsorption energies (31-81 kJ/mol) depend on the metal used (Mg; Sc-Zn). The microscopic mechanism of the CO2 adsorption process is presented at the atomic level, and the detailed potential energy surface and reaction path information are provided. The CO2 molecule and mm-2 grafted M2(dobpdc) are firstly combined via physical interactions, and then, the complex is converted into an N-coordinated zwitterion intermediate over a large energy barrier (1.02-1.51 eV). Finally, the structure is rearranged into a stable ammonium carbamate configuration through a small energy barrier (0.05-0.25 eV). We hope that this research will contribute to the understanding and production of real-world carbon capture materials.
Bibliographical noteFunding Information:
H.Z., X.Z., and L.–M.Y. gratefully acknowledge support from the National Natural Science Foundation of China (21673087, 21873032, 22073033, and 21903032), startup fund (2006013118 and 3004013105) from the Huazhong University of Science and Technology, and the Fundamental Research Funds for the Central Universities (2019kfyRCPY116). The authors thank the Minnesota Supercomputing Institute (MSI) at the University of Minnesota for supercomputing resources. The calculations were carried out using the Mesabi supercomputer. Additional work was carried out at the LvLiang Cloud Computing Center of China, and some calculations were performed on TianHe–2.
© 2021 American Chemical Society.
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