Abstract: The amine-functionalized metal-organic frameworks are regarded as promising adsorbents for capturing CO₂ from coal-fired flue gas due to their high porosity, large CO₂ adsorption capacity, and good water resistance. However, the aggregation of surface amine molecules during high-temperature desorption processes leads to a drop in both adsorption rate and uptake. In this study, a novel amine-functionalized adsorbent was developed by physically encapsulating tetraethylenepentamine molecules into the pores of MOF-808 （TEPA@MOF-808） through a simple impregnation method. Compared to pristine MOF-808, TEPA@MOF-808 exhibited a 2.15-fold increase in CO₂ adsorption uptake, along with enhancements of 13% in adsorption rate constant and 498% in adsorption selectivity. After 10 cycles, its adsorption uptake only decreased by 10.9%. Thermodynamic analysis revealed a low heat of adsorption of 40 kJ/mol, suggesting a physical adsorption mechanism. ¹³C SSNMR and in situ DRIFTS characterization further elucidated the CO₂ physisorption mechanism of TEPA@MOF-808.