A series of mesoporous amino resins (MA) with pore diameters of 2.82 to 9.87 nm have been successfully synthesized at low temperature using poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (P123) as surfactant template via HCl catalyzed sol-gel reactions of melamine and paraformaldehyde, followed by ethanol extraction. The mesoporous amino resin MA-P123-3.5 g, prepared at optimal condition by adding 3.5 g P123 as surfactant template, had higher specific surface area of 706.7 m(2)/g and larger pore size of 9.87 nm. After impregnating with polyethylenimine (PEI), the obtained MA-P123-3.5 g-PEI showed the highest CO2 uptakes of 4.68 mmol/g and amine utilization efficiency of 51.48% at 40 degrees C, which is higher than the theoretical amine utilization efficiency (35%). The kinetics studies implied that the Avrami model could better describe the CO2 adsorption process on the MA-PEI adsorbent, indicating the synergistic effect of chemical and physical adsorption mechanisms. The further analysis of CO2 diffusion model implied that the porous structure of MA is beneficial to the diffusion of CO2 in the particles. Due to the positive influence to the amine groups of the larger pore diameter in the accessibility and diffusion process, the MA samples impregnated with PEI also showed good regeneration stability after 10 cycles of CO2 adsorption-desorption. These results are helpful for developing high-performance CO2 adsorbents.