Yesterday we looked at the difference between the freezing point and dew point (or frost point) of water. Please read that article first.
The CO2 phase diagram is not terribly different.
The freezing point of CO2 at one atmosphere is -78.5ºC. Temperatures in Antarctica occasionally get colder than that, so dry ice molecules do freeze directly out of the air.
However, they don’t accumulate because the number of subliming molecules is identical to the number of freezing molecules. This is exactly the same principle we discussed for water. There is very little CO2 in the atmosphere. Concentration is less than 0.0004, so not many molecules are available to be frozen. In order to get below the frost point (where CO2 ice starts to accumulate) temperatures would have to be much colder.
The freezing point is fixed at a given pressure. The partial pressure of CO2 does not change the freezing point, but it does change the frost point.