Polyamine-based protic ionic liquid (PILs)-functionalized mesoporous silica has drawn much attention due to its high CO2 adsorption rate, high CO2 adsorption capacity, and recyclability. However, the performance of these materials under realistic operating conditions and the influence of flue gas contaminants such as SOx, NOx, and water vapor remain unexplored. In this study, the effects of these flue gas contaminants on CO2 adsorption of PILs-functionalized SBA-15 are evaluated through breakthrough experiments. The results show that the CO2 adsorption capacity and capture rate of the hybrid sorbents are increased by about one-third in the presence of trace water vapor. This is attributed to additional CO2 capture pathways with amine groups that result from the humid environment. The additional pathway was further explained with FT-IR spectroscopy and DFT calculations, which reveal that in the presence of water vapor the CO2 molecules react with amine groups to form stable zwitterionic bicarbonate ions. On the other hand, the sorbents have strong resistance to SO2 and NO over the tested concentration range of 0-500 ppm, with limited impact on CO2 capture. After 8 cyclic adsorption/regeneration experiments, the CO2 adsorption capacities of the sorbents almost are constant when compared to the first cycle performance.