Adsorption Properties and Microscopic Mechanism of CO2 Capture in 1,1-Dimethyl-1,2-ethylenediamine-Grafted Metal–Organic Frameworks

• DOI: 10.1021/acsami.0c01927
• Publication Date: 2020-03-31T00:25:55Z
• Authors: Hui Zhang; Li-Ming Yang; Eric Ganz
• Keywords: Ethylene diamine

The adsorption properties and microscopic mechanism of CO2 in 1,1-dimethyl-1,2-ethylenediamine (dmen) functionalized M2(dobpdc) (dobpdc4-=4,4'-dioxidobiphenyl-3,3'-dicarboxylate; M = Mg, Sc-Zn) have been completely unveiled for the first time via comprehensive investigations based on first-principles density functional theory (DFT) calculations. results show that primary-primary amine, dmen prefers to interact with open metal site end smaller steric hindrance. binding energies MOFs are range 104-174 kJ/mol. In presence CO2, it fully inserts into metal-N bond, forming ammonium carbamate. vary from 53 89 kJ/mol, showing strong dependence. Among 11 metals, dmen-Sc2(dobpdc) dmen-Mg2(dobpdc) highest 84 respectively, may large capacity practical applications. More importantly, capture process dmen-M2(dobpdc) is revealed at atomic level. whole reaction includes two steps, is, formation zwitterion intermediate (step 1) rearrangement 2). step which nucleophilic addition between metal-bound amine proton transfer free simultaneously occur a rate-determining step, higher energy barriers (0.99-1.35 eV). second much lower (maximum 0.16 eV) extremely easy, can promote uptake dmen-M2(dobpdc). This study provides fundamental understanding underlying rather complicated sheds important insights design, synthesis, optimization highly efficient materials.