I would not attempt to use a UV sterilizer as a CO2 reactor. The UV spectrum used by those sterilizers is very dangerous radiation. In my opinion tampering with the body of the sterilizer can subject you to possible UV burns if not done right. Also, most plastics are badly affected by UV, so the parts you add, if they are irradiated by the UV could easily become extremely brittle and break, causing a major water spill. This idea just doesn't seem like a prudent thing to do.