Mesocellular siliceous foams (MCFs) with and without remaining template were prepared and modified by polyethylenimine (PEI) or mixed amines [Diethylenetriamine and PEI or 3-aminopropyltrimethoxysilane (APTMS) and PEI]. These samples were evaluated for their adsorption capacities for CO2 at different temperatures. With the increase of PEI loading, the optimal adsorption temperature shifts to higher temperature for samples prepared in our study. The remaining template in MCF materials plays an important role in promoting CO2 adsorption capacity, which could be 3.24 mmol/g when the amount of PEI loading is 70 % at 85 A degrees C. Meanwhile, the remaining template contributes greatly to the dispersion of PEI, resulting in higher adsorption capacity at low temperature. The effect of the amount of remaining template was studied, and it was found that CO2 adsorption capacity decreases with increasing template. The CO2 adsorption capacities for mixed-amine-modified MCFs are higher than those of the samples modified by PEI only, which was ascribed to the better dispersion of PEI. MCF modified with the mixing of APTMS and PEI exhibited highest adsorption capacity of 2.67 mmol/g at 50 A degrees C. These findings reveal that pore structure, PEI loading, PEI dispersion, and remaining template work together to influence the CO2 adsorption performance.