Couldn't you just take some freebase mescaline, mix with dry ice, put in a container and allow the sublimed co2 to flush the container, then let it sit for a while. To separate you could mix with distilled water and filter, evaporate the filtrate to yield Mescaline carbonate, and recycle the freebase back into the first step.

What kind of problem are you trying to solve by doing the above?

Even if it is "just for fun" a lot of things from what you propose wouldn't work. E.g few if any have ever seen mesc freebase oil; co2 cannot salt mescaliine freebase, co2 needs to react withh water first to create carbonate; mescaline freebase is somewhat water soluble so the distilled water separation would not work, etc.