I don't think this can be generalized that all carbon quantum dots can't do that. However, you need some sort of docking mechanism which binds CO2 with more than weak physisorption so that an efficient energy transfer from the dot to the molecule can take place and since the surface is the docking location, the termination of the dot is crucial for the success. Otherwise you just excite the dot and it just throws out the energy as heat and fluorescence at a higher wavelength.