In order to develop the mild acidic nanocatalyst, ordered mesoporous silica, SBA -15 was functionalized with chloroacetic acid (SBA/CA) via post synthetic grafting technique for useful acidic conversions such as Knoveneganel condensation, Biginelli synthesis and Mannich reaction. The nanocomposites were characterized by Powder X-ray Diffraction method, N2 adsorptiondesorption isotherm, 13 C CP-MAS NMR, FT-IR, TPD and EDXRF. Very high activity and selectivity was observed for all the conversions under milder reaction conditions. Finally, the mechanism of the reaction is proposed and discussed. Copyright © 2013 VBRI press.