Hyper-cross-linked polymers (HCPs), as one of the variety of microporous polymers with nanosized pores, have attracted a lot of interest in carbon dioxide adsorption and storage. A HCP adsorbent based on benzene and Friedel–Crafts reaction was synthesized for CO2 adsorption. The response surface methodology is suggested for optimizing the process parameters in order to determine the highest possible CO2 adsorption capacity of the HCP adsorbent. Pressure, temperature, ratio (cross-linker/benzene), and synthesis time are considered as activation parameters, and adsorption capacity (mg/g) is proposed as the response of this method. Additionally, experimental adsorption data were fitted by the adsorption isotherm and kinetic models to obtain the adsorbent behavior. Finally, thermodynamic modeling was accomplished and enthalpy, entropy, and Gibbs free energy differences of adsorption at 293 K were obtained at −20.612 kJ/mol, −0.043 kJ/mol K, and −7.950 kJ/mol, respectively. The optimum values of pressure, temperature, ratio (cross-linker/benzene), and synthesis time within the experimental range that maximize CO2 adsorption capacity were obtained at 7.8 bar, 294 K, 2.75, and 13.6 h, respectively. The optimized value of CO2 adsorption capacity by benzene-based HCP was obtained as 262 mg/g.