Simulation of gas adsorption on single-walled carbon nanotubes

Abstract

This study combined Grand Canonical Monte Carlo molecular simulations with density functional theory calculations to systematically examine the adsorption of N₂, O₂, H₂, CO₂, and CH₄ 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 N₂/O₂ 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.