With the increasing demand for renewable energy, biogas has emerged as a promising alternative to fossil energy. However, its high CO2 content significantly reduces the heating value and contributes to greenhouse gas emissions. Efficient CO2/CH4 separation is therefore essential for upgrading biogas and mitigating environmental impacts. Here, MOF-303/graphitized carboxyl-functionalized multiwalled carbon nanotubes (MWCNTs-COOH) nanocomposites were synthesized using a hydrothermal method to improve CO2 capture capability and CO2/CH4 separation. The composite successfully maintained the crystal structure of MOF-303. Adsorption tests showed that the 5.0 wt % composite had a CO2 adsorption capacity of 164.2 cm3/g at 273 K and 1 bar, surpassing 141.1 cm3/g of pure MOF-303, while CH4 adsorption remained below 34 cm3/g at 273 K. After 10 static and five dynamic adsorption cycles, the composites preserved both high CO2 adsorption capacity and structural stability, indicating strong potential for biogas purification. It is demonstrated by DFT calculations that the introduction of MWCNTs-COOH enhances the adsorption energy of the composite, which significantly improves both the CO2 adsorption capacity and the adsorption selectivity for CO2.
Gong et al. (Mon,) studied this question.