Simulation of gas adsorption on single-walled carbon nanotubes.

This study combined Grand Canonical Monte Carlo molecular simulations with density functional theory calculations to systematically examine the adsorption of N(2), O(2), H(2), CO(2), and CH(4) on nineteen single-walled carbon-nanotube (SWCNT) architectures. The effects of temperature, pressure, nanotube diameter, chirality, and vacancy defects on adsorption energies and isosteric heats are quantified. Binary N(2)/O(2) separation within a (22,18) SWCNT is modelled by analyzing energy-distribution functions and spatial adsorption fields. Intermolecular interactions are represented with the Universal Force Field and Lennard-Jones potentials. Lower temperatures and higher pressures enhanced adsorption capacity, while adsorption energies and isosteric heats decreased accordingly. Furthermore, smaller-diameter SWCNTs exhibited superior selectivity for air separation. Neglecting electrostatic and hydrogen-bonding terms for non-polar gases is demonstrated to reduce computational cost without sacrificing accuracy. These findings establish a robust framework for rationalizing SWCNT-based adsorbents for gas-separation applications.