CO2 diffusion and chemical reactions
 

Hi, I'm new to Fluent and have been looking for a way to model CO2 diffusion through a material, including some chemical reactions that take place between the CO2 and the material.
My boundary conditions do not include a velocity since the experiment is carried away in a chamber with almost no air flow. Aditionally, we are trying to model just diffusion in the material assuming a CO2 concentration in the boundary of the domain.
I have seen some porous media flow tutorials were a velocity is specified for a fluid domain which is in contact with the porous domain, but was wondering if there's a way to model just the porous domain.
Another option was to model de CO2 concentration as temperature in CFX, but couldn't find a way to model the chemical reactions then.
I would like to hear some comments or suggestions as to how to model the situation or if Fluent is in fact the best option in ANSYS to do this.