Hydrogen, Fuel Cell & Energy Storage

Hydrogen, Fuel Cell & Energy Storage

Molecular Simulation Study of CO2 Removal from H2 Stream by SIFSIX-3-Cu Adsorbent

Document Type : Research Paper

Authors
Chemical Engineering Department, Ilam University, Iran
10.22104/hfe.2026.7794.1376
Abstract
The gradual depletion of fossil fuel reserves has renewed interest in hydrogen (H2) as a durable and sustainable energy carrier. However, its successful application on an industrial scale hinges on removing trace contaminants particularly carbon dioxide (CO2) from mixed gas streams. In this study, the separation of CO2 from CO2/H2 mixtures was investigated using the metal organic framework SIFSIX 3 Cu and Grand Canonical Monte Carlo (GCMC) simulations across a wide range of temperatures and pressures. Two gas compositions (molar ratios CO2/H2 of 0.90/0.10 and 0.79/0.21) were examined between 298 K and 370 K. In every case, CO2 uptake was markedly higher than that of H2, and the adsorption of both gases decreased with increasing temperature. The Langmuir isotherm model provided an excellent fit to the observed data, indicating monolayer adsorption behavior. The isosteric heats of adsorption were calculated to be about 54kJ mol-1 for CO2 and roughly 2kJ mol-1 for H2, reflecting the stronger electrostatic attraction between CO2 molecules and the SiF62- sites in the framework. Spatial density distribution analysis revealed that CO2 molecules preferentially occupy regions near the SiF62- units, whereas H2 molecules are mainly located around pyrazine rings. Overall, these findings highlight the pronounced CO2 selectivity of SIFSIX 3 Cu even at low concentrations and underline its potential for hydrogen purification in industrial gas separation processes.
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