Equation-of-state (pressure, density, temperature, internal energy) and reflectivity measurements on shock-compressed CO2 at and above the insulating-to-conducting transition reveal new insight into the chemistry of simple molecular systems in the warm-dense-matter regime. CO2 samples were precompressed in diamond-anvil cells to tune the initial densities from 1.35  g/cm3 (liquid) to 1.74  g/cm3 (solid) at room temperature and were then shock compressed up to 1 TPa and 93 000 K. Variation in initial density was leveraged to infer thermodynamic derivatives including specific heat and Gruneisen coefficient, exposing a complex bonded and moderately ionized state at the most extreme conditions studied.