Experimental and numerical study of CO2 adsorption on Ni/DOBDC metal-organic framework

• Amount and heat of CO2 adsorption were experimentally and numerically studied.
• Formation of CO2 adsorption was revealed at molecule level.
• Selectivity of CO2/CH4 was sensitive to the pressure and temperature.
• Electronic interactions played leading role in the selectivity.

Metal-organic frameworks show promising applications for carbon capture and storage. In this research, CO2 adsorption on a Ni/DOBDC metal-organic framework was experimentally studied at a pressure range of 0 kPa–100 kPa and a temperature range of 25 °C–115 °C. The adsorption of CO2 and selectivity for CO2/CH4 were also numerically examined through the grand canonical Monte Carlo method. The adsorbed amount increased significantly at the initial stage and then rose in a steady manner with increased pressure. In contrast, the isosteric heat of adsorption gradually decreased. As the temperature increased, the adsorbed amount decreased linearly, but the isosteric heat of adsorption remained nearly unchanged. The sites and density profiles of the adsorbate provided insight into the formed Ni2+⋯OCO at the molecular level. The selectivity for CO2/CH4 was sensitive to pressure and temperature. The electronic contribution could reach 62.0%–68.3% in the 0 kPa–100 kPa pressure range and 40.7%–68.3% in the 25 °C–115 °C temperature range.