Carbon sorbents are of interest for post-combustion CO₂ capture. Polymers are one of the potential precursors to develop carbon adsorbent with suitable surface functionalities. In this research, furfurylamine-based polybezoxazine was used to produce the carbon adsorbent because of its superior properties such as high char yield, high thermal stability, and low water adsorption. To obtain the carbon adsorbent, benzoxazine monomer was prepared by using furfurylamine, paraformaldehyde, and phenol. Polymerization by a sol-gel technique using xylene as a solvent was employed. The obtained polymer was carbonized at various temperatures: 600, 700, and 800 °C. Physical and chemical activation were then conducted at 900 °C by using CO₂ and KOH as an activating agent, respectively. The CO₂ adsorption performance was conducted using a volumetric method at 40, 70, and 110 °C. The results show that both surface morphology and functionalities play a key role in CO₂ adsorption performance. Chemical activation gave the carbon adsorbent with higher surface area and pore volume than the physical activated adsorbents. The conversion of pyridinic functionalities to pyrrolic and pyridonic functionalities was revealed in the XPS analysis in both adsorbents activated by chemical and physical methods. The adsorbent carbonized at 800 °C and activated and chemical activated gave the highest CO₂ adsorption capacity at all adsorption temperatures as a result of its high surface area (1,273 m²/g), high pore volume (0.537 cm³/g micropore volume and 0.7891 cm³/g total pore volume) and suitable surface functionalities.