In this work, benzene based hypercrosslinked polymer (HCP) as an adsorbent was modified using amine group to enhance CO2uptake capability and selectivity. Based on BET analysis result, the HCP and the modified HCP provide surface area of 806 (m2g−1) and micropore volume of 453 (m2g−1) and 0.19 (cm3g−1) and 0.14 (cm3g−1), respectively. The CO2and N2gases adsorption were performed in a laboratory scale reactor at a temperature between 298 and 328 K and pressure up to 9 bar. The experimental data were evaluated using isotherm, kinetic and thermodynamic models to identify the absorbent behavior. The maximum CO2adsorption capacity at 298 K and 9 bar was obtained 301.67 (mg g−1) for HCP and 414.41 (mg g−1) for amine modified HCP. The CO2adsorption thermodynamic parameters assessment including enthalpy changes, entropy changes, and Gibbs free energy changes at 298 K were resulted − 14.852 (kJ mol−1), − 0.024 (kJ mol−1K−1), − 7.597 (kJ mol−1) for HCP and − 17.498 (kJ mol−1), − 0.029(kJ mol−1K−1), − 8.9 (kJ mol−1) for amine functionalized HCP, respectively. Finally, the selectivity of the samples were calculated at a CO2/N2composition of 15:85 (v/v) and 43% enhancement in adsorption selectivity at 298 K was obtained for amine modified HCP.