You need to spend a bit of time learning chemistry.
Just because there are two oxygen atoms bonded to a carbon atom (CO2) it does NOT mean that the oxygen is free to react as normal, diatomic oxygen (O2) would.
Both gasses are inert (for our purposes). Nitrogen tends to be drier from the bottle, but CO2 can be had that is just as dry as nitrogen.
We fridgys have started using CO2 again as a refrigerant for low temp systems. At -23F it had damned well better be dry. Don't believe me? Google R744.....
What I like about CO2 is that you get one heck of a lot more gas in the cylinder due to it being liquified. A little moisture doesn't scare me a bit as I know that I will be pulling a deep vacuum and installing new driers.