Three component coupling reactions of aldehyde, beta-ketoester (or beta-diketone) and urea (or substituted urea) were carried out by using acid activated montmorillonite clay (AT-Mont.) catalyst having surface area about 400 m(2)/g for the facile synthesis of 3,4-dihydropyrimidin-2(1H)-ones via the Biginelli reactions under mild reaction conditions. The activation of montmorillonite clay was carried out with HCl under controlled conditions for generating nanopores (size 2-7 nm) into the matrix. This porous catalyst has promising feature for Biginelli reaction such as easy removal of the catalyst, short reaction time, high yield with 100% selectivity and easy workup procedure. Powder XRD, SEM-EDX, N-2 adsorption, pyridine adsorbed FT-IR and TPD analysis were carried out to characterize the solid porous AT-Mont. The catalysts can be recycled and reused several times without significant loss of their catalytic activity. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.