Metal-assisted pore architecture regulating CO₂ adsorption and supercapacitor performance in biomass-derived carbons

Reducing atmospheric CO₂ requires low cost and energy efficient adsorbents, yet porous carbons are still often designed primarily based on BET surface area. Here, pinecone-derived porous carbons were synthesized via metal-assisted activation to tailor ultramicropore structure and surface chemistry. The optimized Mn-600-700 sample shows a CO₂ uptake of 4.18 mmol g^-1 at 298.15 K, with high CO₂/N₂ selectivity of 13.56 at 1 bar and a moderate adsorption heat of 21.28 kJ mol^-1, together with initial adsorption-desorption regenerability. Correlation analysis reveals that CO₂ uptake is governed mainly by ultramicropores rather than total surface area, indicating a confinement-controlled mechanism relevant to low pressure capture. Dual-site Langmuir fitting and DFT calculations based on an idealized metal-O-modified graphene model further suggest that polarized metal-carbon interfacial sites enhance surface polarization and CO₂ affinity without inducing strong chemisorption, thereby preserving reversibility. In contrast, electrochemical charge storage depends more on ion-accessible micropores and mesopore-assisted transport. This work clarifies the distinct pore-structure requirements for CO₂ capture and capacitive storage and provides a practical strategy for designing sustainable biomass-derived carbons.