Boiling point of CO2?

Refer to the phase diagram below.

At room pressure (about 1 atm, below 5.2 atm), liquid carbon dioxide does not exist as liquid. Solid carbon dioxide sublimes to gaseous carbon dioxide on heating, while gaseous carbon dioxide solidifies on cooling. At such pressure, there is no boiling point for carbon dioxide as the liquid state does not exist.

Above 5.2 atm, all the three states of carbon dioxide exist. The boiling point of carbon dioxide depends on the pressure. The higher the pressure, the higher the boiling point of carbon dioxide is.