Molecular Simulations and Experimental Studies of CO, CH, and N Adsorption in the UNT-14 Metal-Organic Framework.

Selective adsorption of CO over CH and N using porous materials is a promising approach for the capture of CO and upgrading of natural gas. Herein, we present a combined simulation and experimental study of the adsorption uptakes of CO, CH, and N in UNT-14, a copper-based metal-organic framework. Grand Canonical Monte Carlo (GCMC) simulations were employed to predict the pure component adsorption isotherms at 273 and 298 K using atomic charges calculated via three different charge methods. Among those, the Mulliken charge set agrees best with the experimental adsorption data. UNT-14 exhibits greater affinity for CO as compared to CH and N, revealed by higher Henry's constant () and isosteric heats of adsorption at infinite dilution (). Density functional theory (DFT) calculation displays a larger binding energy (BE) value for CO than for CH and N. Radial distribution function (RDF) analysis reveals that CO molecules tend to adsorb preferentially on the peripheral benzene rings, whereas CH and N molecules tend to adsorb more preferentially on the central benzene ring of the linker. The ideal adsorbed solution theory (IAST) suggests a favorable adsorption selectivity of UNT-14 for equimolar CO/CH and CO/N gas mixtures (for both the experimental and simulated data), demonstrating efficient CO capture and natural gas upgrading ability.