In-Situ Infrared Study of CO₂ Adsorption on SBA-15 Grafted with γ-(Aminopropyl)triethoxysilane

CO2 adsorption/desorption on SBA-15 grafted with γ-(aminopropyl)triethoxysilane (APTS) has been studied by infrared spectroscopy coupled with temperature-programmed desorption. SBA-15, a mesoporous silica material with a uniform pore size of 21 nm and a surface area of 200−230 m2/g, provides an OH functional group for grafting of γ-(aminopropyl)triethoxysilane. The amine-grafted SBA-15 adsorbed CO2 as carbonates and bicarbonates with a total capacity of 200−400 μmol/g. The heat of CO2 desorption was determined to be 3.2−4.5 kJ/mol in the presence of H2O and 6.6−11.0 kJ/mol in the absence of H2O during temperature-programmed desorption. Repeated CO2 adsorption/desorption CO2 cycles shifted the desorption peak temperature downward and decreased the heat of CO2 adsorption.