Synergistic Effect of Hierarchical Pores and Amine Functionalization on CO2 Adsorption Performance by Distillers' Grains-Derived Biochar Spheres

• • Amine-functionalized hierarchical porous carbon spheres (0.2PW-K-CNF-PEI) achieved a CO2 adsorption capacity of 1.03 mmol/g at 100 °C, demonstrating effective capture at typical flue gas temperatures. • • The CO2 diffusion coefficient reached 0.0495 min−1, indicating rapid mass transfer due to retained macropores (total pore volume 0.0030–0.0066 cm3/g after amine loading). • • At 80 °C, the material exhibited superior selective CO2 adsorption of 44 mg/g, crucial for separating CO2 from flue gas mixtures. • • The synthesis method (ash self-templating and particle self-assembly) simultaneously created pores and loaded amines, increasing adsorption sites while preserving structural stability, offering a scalable route for waste-derived adsorbents.