Cumene is prepared selectively through an eco-friendly route using naturally available montmorillonite clay as the green catalyst. Pillaring of montmorillonite is done to improve the structural stability for long-term use. Alumina pillaring and the influence of mixed pillaring with zirconia and chromia on the structural as well as textural properties are characterized. Montmorillonite shows very high conversion, selectivity and regenerability upon pillaring towards isopropylation of benzene.