Structures and photoelectron spectral properties of I−⋅nCO2 (n=1–7) clusters are presented at the level of second-order Møller–Plesset perturbation theory with relativistic corrections. Triple split-valence 6-311++G(d,p) basis set functions are employed herein. It is observed that the CO2 molecules approach the I− anion from one side in all the clusters and that I−⋅nCO2 clusters prefer the surface structure. The calculated vertical detachment energy of these clusters is in excellent agreement with the reported experimentally measured values (within 4 %). Efforts are also made to extract vertical detachment energy of large size of clusters, including the bulk. The extracted vertical detachment energy values for larger clusters (n=8–13) by employing the microscopic theory-based expression are also close (within 4 %) to that of the experimentally measured values.