MOF-5 derived carbon as material for CO₂ absorption

In our study we prepared MOF-5 derived carbon to reveal the thermodynamics of CO₂ absorption processes in great detail. Porous carbon material was prepared from a metal-organic framework (MOF-5) via carbonization at 1000 °C. The obtained structure consists only of carbon and exhibits a BET specific surface area, total pore volume and micropore volume of 1884 m² g^-1, 1.84 cm³ g^-1 and 0.59 cm³ g^-1, respectively. Structural analysis allowed the assumption that this material is an ideal candidate for efficient CO₂ absorption. The CO₂ uptake was 2.43 mmol g^-1 at 25 °C and 1 bar. Additionally, the absorption over a wide range of temperatures (25, 40, 60, 80 and 100 °C) and pressures (in range of 0-40 bar) was investigated. It is shown that the CO₂ absorption isotherm fits a multitemperature Sips model. The calculated Sips equation parameters allows the isosteric heat of adsorption to be obtained. The isosteric heat of adsorption for CO₂ decreased substantially with an increase in surface coverage by gas molecules. This indicates a negligible intermolecular interaction between CO₂ molecules. A decrease in the isosteric heat of adsorption with surface coverage is a result of the disappearance of favourable adsorption sites.