Global climate change and carbon emissions have necessitated the development of efficient carbon capture technologies to mitigate environmental impacts. Biochar has emerged as a promising CO₂ adsorbent due to its porous carbon structure, high adsorption capacity, and cost-effectiveness. This study investigates the enhancement of CO2 adsorption performance in woodchip-derived biochar through chemical activation and post-treatment. Chemical activation facilitates controlled thermal decomposition of biomass, promoting micropore development while suppressing other negative factors. The subsequent treatment of biochar surface to introduce nitrogen-functional groups, further improves CO2 capturing affinity. Structural and chemical modifications of the synthesized biochar's were analyzed using CHNS, FE-SEM, and FTIR for elemental composition, morphological features, and functional group retention. The experimental results indicate that the CO2 adsorption capacity improves compared to the untreated samples, with the chemical activation during pyrolysis and further by the surface functionalization. These findings highlight the synergistic role of chemical activation and functionalization in optimizing biochar-based carbon capture materials for sustainable applications.