Fly ash contains mainly alumina and silica as its main constituents. A novel method for the extraction of highly stable alumino-silicates from fly ash has been developed. The as-extracted alumino-silicate has been further fiinctionalized with APTES ((3-aminopropyl)triethoicysilane), TRIS buffer (tris(hydroxymethyl)aminomethane), and AMP (3-amino-2-methyl-1-propanol) to impart basicity for carbon dioxide adsorption. A dynamic adsorption capacity of 6.62 mg/g has been observed for FAS (fly ash based alumino-silicate) and has improved by a factor of 4.0, with an adsorption capacity of 26.5 mg/g for AMP-functionalized FAS at 55 degrees C with 15% CO2 in N-2. The positive influence of water was observed with an improvement of adsorption capacity to 34.82 mg/g at 55 degrees C with 15% CO2, 82% N-2, and 3% water vapor. The adsorbent is studied for adsorption capacity at varying temperatures, and the best performing adsorbent is characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermal analysis, and elemental analysis to study the morphological properties of the present adsorbent support. The excellent thermal stability of synthesized material suggested the formation of promising aluminosilicate for CO2 adsorption.