CO2 adsorption and activation over medium sized Cun (n = 7, 13 and 19) clusters: A density functional study

► Sound evidence of chemisorption of CO2 over Cun clusters, through C interaction with the cluster. ► Preferential CO2 adsorption sites have been identified on the odd numbered Cun (n = 7, 13, and 19) clusters. ► Activation of CO2 molecule observed with significantly stretched C-O bond length (1.20-1.30 Å). ► Thermodynamic favor-ability of the adsorption process established by positive adsorption energy of CunCO2 system. ► Natural population analysis (NPA) revealed that electron density moves form HOMO of Cun clusters to LUMO of CO2 molecule.