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.