Mesoporous MCM-41, MCM-48 and SBA-15 were synthesized using Rice husk ash (RHA) as the silica source and their defective Si–OH sites were functionalized by 3-cholropropyltrimethoxysilane
(CPTMS) which was subsequently grafted with amine compounds, Tris(2-aminoethyl)amine (TREN) and
Tetraethylenepentamine (TEPA). X-ray powder diffraction (XRD) and BET results of the parent mesoporous silica suggested their closeness of structural properties to those obtained from conventional silica
sources. CO2 adsorption of branched amine TREN and straight chain amine TEPA at 25, 50 and 75 ◦C was
obtained by Thermogravimetric Analyser (TGA) at atmospheric pressure. TREN grafted mesoporous silica
showed 7% of CO2 adsorption while TEPA grafted mesoporous silicas showed less CO2 adsorption, which
is due to the presence of isolated amine groups in TREN. TREN grafted mesoporous silicas were also
observed to be selective towards CO2, thermally stable and recyclable. The order of CO2 adsorption with
respect to amount of amine grafting was observed to be MCM-48/TREN > MCM-41/TREN > SBA-15/TREN.