Herein, we report the adsorption energy and reaction path of CO2 capture by N,N-diethylethylenediamine (ee-2)-functionalized M2(dobpdc) (M = Mg, Sc-Zn; dobpdc4-= 4,4′-dioxidobiphenyl-3,3′-dicarboxylate) calculated using density functional theory (DFT). Our calculations reveal that both the amine (ee-2) binding energies and CO2 adsorption energies have strong metal center dependence. The ranges are 131.3 (Cr) to 184.1 kJ/mol (V) and 37.7 (Cu) to 79.2 kJ/mol (Sc) for the ee-2 binding energies and CO2 adsorption energies, respectively. In addition, we determined the reaction intermediates and barriers of the CO2 adsorption process. The entire process consists of two steps: first, the combination of CO2 with ee-2-M2(dobpdc) changes from a vdW complex to a chemically bonded intermediate, accompanied by the transfer of a proton in the primary amine. Then, a molecular rearrangement reaction occurs, forming a stable ammonium carbamate structure. The first step of the process has a higher barrier (1.04-1.49 eV) in comparison to that (0.01-0.27 eV) of the second step. This first step is the decisive step of the overall reaction of CO2 with ee-2-M2(dobpdc). This work provides a fundamental understanding of the microprocess of CO2 capture by amine-functionalized MOFs and sheds some insight into the design and optimization of highly efficient CO2 capture materials.
Bibliographical noteFunding Information:
X.Z., H.Z., and L.-M.Y. gratefully acknowledge support from the National Natural Science Foundation of China (21673087, 21873032, 22073033, 21903032), startup funds (2006013118 and 3004013105) from 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 on 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.