Enhanced CO2 adsorption capacity of amine-functionalized MIL-100(Cr) metal-organic frameworks

Amine-functionalized metal-organic frameworks EN-MIL-100(Cr) and MMEN-MIL-100(Cr) were prepared by grafting ethylenediamine and N,N'-dimethylethylenediamine molecules, respectively, on coordinatively unsaturated chromium(III) cations in MIL-100 metal-organic frameworks. Although amine grafting results in a decrease in the surface area and pore volume of the functionalized samples compared to those of the bare MIL-100(Cr), results showed that the incorporation of amine groups into the MIL-100 framework improved both carbon dioxide adsorption capacity and kinetics, especially in the case of ethylenediamine. Heats of carbon dioxide adsorption in EN-MIL-100(Cr) and MMEN-MIL-100(Cr) were about 80 kJ mol(-1) at zero coverage, a value higher than that shown by MIL-100(Cr), which suggests chemisorption between CO2 and pendant amine groups. Measurement of CO2 adsorption-desorption cycles proved that functionalized materials show good regenerability and stability.