► Eggshell as a new bioactive and heterogeneous catalyst in organic synthesis ► Green, efficient and rapid synthesis of 7,8-dihydro-4H-chromen-5(6H)-ones ► Eggshell characterization with elemental analysis, XRD patterns and FT-IR spectra ► The ability of eggshell to carry out the large scale synthesis ► High catalytic activity and reusability of eggshell even after five cycles