Now a day's, Calcium carbonate (CaCO3) is ineluctable filler in emerging industrial fields. Polymer-mediated CaCO3 nanocomposites are dreadfully useful in wide range of industrial applications. To achieve such a nanocomposites (NCs), in the present study, CaCO3 (without polymer), PMMA, PEG and PVP/CaCO3 NCs have been successfully synthesized by the biomimetic method using natural limestone rock as a crucial source. Synthesized products were characterized by FTIR, XRD, SEM-EDS, TEM, UV-Vis DRS and PL techniques to know the mineralogy, morphology, crystallites size, band gap energy and emission characteristics. The crystallites size of the final product is about 20-30 nm. It has monodispersed, spherical shape and porous like structure. The band gap value of the final product is about (3.15-3.36 eV) and product exhibits good luminescence intensity in the blue region. Synthesized products are subjected to supercapacitor performance and photocatalytic activities to know the effectiveness of the product. Achieved characteristics show that the biomimetic products may be used for various industrial applications. This synthesis method is Eco-friendly and hot chemical free. The present study, recommends that instead of huge chemicals which are used as a source, natural limestone rock may be used for getting nano CaCO3 composite for extensive industrial requirements with lesser cost. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.