By impregnating polyethylenimine (PEI) into silica mesocellular foam with the template remaining (MCF(a)), a novel sorbent with both high CO2 adsorption capacity and high thermal stability was obtained. The remaining P123 template in the MCF played a great role in promoting the CO2 adsorption capacity, which could be 4.5 mmol.g(-1) (adsorbent) when the amount of amine loading and the adsorption temperature were optimized as 60% and at 70 degrees C for the sample MCF(a)/PEI. Meanwhile, MCF(a)/PEI had a high thermal stability and selectivity, after 10 adsorption-desorption cycles, MCF(a)/PEI almost held a constant adsorption capacity; for different compositions of CO2 and N-2 mixed gases, it always kept a high adsorption selectivity of CO2/N-2. The mechanism of the template synergistic effect was elucidated by the result of a secondorder rate law through CO2 adsorption kinetic studies. Moreover, as predicted by the Langrnuir adsorption model with n = 2 (two active adsorption sites for one CO2 molecule), the adsorption enthalpy was calculated as about -85 kj.mol(-1), a value which belonged to typical chemical adsorption.