Multiscale Computational Study on the Adsorption and Separation of CO 2 /CH 4 and CO 2 /H 2 on Li + ‐Doped Mixed‐Ligand Metal–Organic Framework Zn 2 (NDC) 2 (diPyNI)

The quantum mechanics (QM) method and grand canonical Monte Carlo (GCMC) simulations are used to study the effect of lithium cation doping on the adsorption and separation of CO 2 , CH 4 , and H 2 on a twofold interwoven metal–organic framework (MOF), Zn 2 (NDC) 2 (diPyNI) (NDC=2,6‐naphthalenedicarboxylate; diPyNI= N , N ′‐di‐(4‐pyridyl)‐1,4,5,8‐naphthalenetetracarboxydiimide). Second‐order Moller–Plesset (MP2) calculations on the (Li + –diPyNI) cluster model show that the energetically most favorable lithium binding site is above the pyridine ring side at a distance of 1.817 Å from the oxygen atom. The results reveal that the adsorption capacity of Zn 2 (NDC) 2 (diPyNI) for carbon dioxide is higher than those of hydrogen and methane at room temperature. Furthermore, GCMC simulations on the structures obtained from QM calculations predict that the Li + ‐doped MOF has higher adsorption capacities than the nondoped MOF, especially at low pressures. In addition, the probability density distribution plots reveal that CO 2 , CH 4 , and H 2 molecules accumulate close to the Li cation site. The selectivity results indicate that CO 2 /H 2 selectivity values in Zn 2 (NDC) 2 (diPyNI) are higher than those of CO 2 /CH 4 . The selectivity of CO 2 over CH 4 on Li + ‐doped Zn 2 (NDC) 2 (diPyNI) is improved relative to the nondoped MOF.