What programming language should I use to run physics simulations of CO2 being absorbed by different materials?
That depends on a lot of factors, mostly on available software for the task (you don't want to do the whole job yourself, if it is already done, or there are pieces you can combine with little effort, use that), in second line on how detailed your model (and it's computing requirements) is might force the use of inconvenient but efficient languages/packages.
This is probably a question better asked elsewhere, perhaps on a physics or chemistry forum (for the modelling aspects, and possibly for software alternatives in common use), or (given much more detailed requirements and specifications) on a forum on programming.