Microwave spectra of the four isotopologue/isotopomers, HI-(CO2)-C-12-O-16, HI-(CO2)-C-12-O-18-HI-C-12 (OO)-O-18-O-16, and HI-(COO)-C-12-O-16-O-18, have been recorded using pulsed-nozzle Fourier transform microwave spectroscopy. In the last two isotopomers, the heavy oxygen atom tilted toward and away from the HI moiety, respectively. Only b-type K-a = 1<--0 transitions were observed. Spectral analysis provided molecular parameters including rotational, centrifugal distortion, and quadrupole constants for each isotopomer. Then, a four-dimensional intermolecular energy surface of a HI-CO2 complex was generated, morphing the results of ab initio calculations to reproduce the experimental data. The morphed potential of HI-(CO2)-C-12-O-16 had two equivalent global minima with a well depth of 457(14) cm(-1) characterized by a planar quasi-T-shaped structure with the hydrogen atom tilted toward the CO2 moiety, separated by a barrier of 181(17) cm(-1). Also, a secondary minimum is present with a well depth of 405(14) cm(-1) with a planar quasi-T-shaped structure with the hydrogen atom tilted away from the CO2 moiety. The ground state structure of HI-(CO2)-C-12-O-16 was determined to have a planar quasi-T-shaped geometry with R = 3.7717(1) angstrom, theta(ocl) = 82.30(1)degrees, theta(ClH) = 71.55(1)degrees. The morphed potential obtained is now available for future studies of the dynamics of photoinitiated reactions of this complex.