Molecular Simulations and Experimental Studies of CO<sub>2</sub>, CH<sub>4</sub>, and N<sub>2</sub> Adsorption in the UNT-14 Metal–Organic Framework
R Yasmeen, Sheikh M. S. Islam, Jincheng Du, Mohammad A. Omary
Abstract
Selective adsorption of CO 2 over CH 4 and N 2 using porous materials is a promising approach for the capture of CO 2 and upgrading of natural gas. Herein, we present a combined simulation and experimental study of the adsorption uptakes of CO 2, CH 4, and N 2 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 2 as compared to CH 4 and N 2, revealed by higher Henry’s constant ( K H ) and isosteric heats of adsorption at infinite dilution ( Q st0 ). Density functional theory (DFT) calculation displays a larger binding energy (BE) value for CO 2 than for CH 4 and N 2 . Radial distribution function (RDF) analysis reveals that CO 2 molecules tend to adsorb preferentially on the peripheral benzene rings, whereas CH 4 and N 2 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 2 /CH 4 and CO 2 /N 2 gas mixtures (for both the experimental and simulated data), demonstrating efficient CO 2 capture and natural gas upgrading ability.