The current work builds on previous works on grafting of organosilanes on mesoporous silica supports using a supercritical CO2 anhydrous method, and it extends them by examining the capacity of supercritically prepared aminosilica hybrid products for CO2 adsorption and its separation from mixtures with other gases. The CO2 adsorption capacity under dry conditions of mesoporous silica gel and MCM-41 functionalized with a monoaminosilane was evaluated first by recording CO2 adsorption isotherms and next by performing microbalance cyclic adsorption/desorption experiments at 25 and 45 degrees C. CO2 adsorption and desorption rates were also studied as a function of the aminosilane loading. CO2 adsorption results were compared to similar data available in the literature, showing improved performance for the supercritically prepared products related to the CO2 adsorption efficiency and cyclic regenerability.