Effect of Metal in M3(btc)2 and M2(dobdc) MOFs for O2/N2 Separations: A Combined Density Functional Theory and Experimental Study

Abstract

Computational screening of metal–organic framework (MOF) materials for selective oxygen adsorption from air is used to identify new sorbents for oxyfuel combustion process feedstock streams. A comprehensive study on the effect of MOF metal chemistry on gas binding energies in two common but structurally disparate MOFs has been undertaken. Dispersion-corrected density functional theory (DFT) methods were used to calculate the oxygen and nitrogen binding energies with each of 14 metals, respectively, substituted into two MOF series, M2(dobdc) and M3(btc)2. The accuracy of DFT methods was validated by comparing trends in binding energy with experimental gas sorption measurements. A periodic trend in oxygen binding energies was found, with greater oxygen binding energies for early transition-metal-substituted MOFs compared to late transition metal MOFs; this was independent of MOF structural type. The larger binding energies were associated with oxygen binding in a side-on configuration to the metal, with con...