To achieve selective CO2 adsorption, the ordered mesoporous material Na-MCM-41 was synthesized by a hydrothermal method and subsequently modified with different amounts of tetra ethylene pentamine (TEPA) through wet impregnation. The as-synthesized adsorbents were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, BET analysis, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The effects of amine loading and adsorption temperature on the performance of the adsorbents for selective CO2 adsorption were evaluated using a breakthrough method with a fixed-bed reactor equipped with an online multicomponent gas analyzer. The CO2 adsorption capacity of Na-MCM-41 with 55 wt.% TEPA loading (Na-MCM-41(0.55)) was as high as 3.178 mmol/g under the conditions of 10% (v/v) CO2 in CH4 at 70°C, with a maximum separation coefficient of 3.9198. Moreover, cyclic CO2 adsorption–desorption tests demonstrated the excellent regenerability and stability of Na-MCM-41(0.55), which exhibited a decrease in adsorption capacity of only 5.76% over 10 cycles.