Amine-modified MCM-41 mesoporous silica for carbon dioxide capture

Abstract This paper presents an easy way to obtain a material with CO2 sorption properties by using commercially available MCM-41. In order to increase MCM-41 CO2 sorption capacity, 2.48 mmol g−1 of amine groups were anchored onto silica surface. A few carefully chosen spectroscopic techniques – namely infrared diffuse reflectance spectroscopy and solid-state 13C and 29Si nuclear magnetic resonance – demonstrated that amino groups are covalently bounded to mesoporous silica and not just adsorbed on it. CO2 uptake by the samples was investigated by microcalorimetry experiments performed at 30 °C. The amine functionalized material, MCM-41-NH2, exhibited a higher uptake of CO2 at very low pressures compared with the nongrafted material. The modified material presented heat of adsorption of −98 versus −32 kJ mol−1 for MCM-41 at low pressures. The mode of CO2 uptake in MCM-41-NH2 was both chemisorption at low pressures and physisorption at high pressures. Solid-state 13C nuclear magnetic resonance performed on amine-functionalized MCM-41 after CO2 adsorption experiments, showed a signal attributed to carbamate that was formed as a product of the reaction between CO2 and amine groups. This material has potential for CO2 recovery at low pressures/concentrations.