Hierarchical Pore Structure Engineering in Bamboo Shoot Sheath-Derived Biochar: Synergistic Effects of Bio-Templated Chemical Activation and Gradient Pyrolysis

The combustion of fossil fuels has led to excessive CO 2 emissions and severe climate impacts, making efficient CO 2 capture an urgent priority. Although chemical activation can enhance the CO 2 adsorption performance of biochar, its extensive use often entails environmental, equipment, and cost challenges. In this study, we present an innovative bio-templating strategy to synthesize hierarchically porous, heteroatom-enriched biochars derived from waste bamboo shoot shells and starch, using K 2 CO 3 as an activator and yeast as the bio-template. This method significantly reduces activator consumption compared with conventional activation processes. The optimized biochar, BAS 0.5 KC-800, exhibited exceptional CO 2 adsorption capacities of 5.15   mmol/g at 0 ℃ and 3.38   mmol/g at 25 ℃. Structural analysis revealed that its high specific surface area (1186 m 2 /g) and micropore volume (0.55 cm 3 /g) provide abundant CO 2 adsorption sites. Furthermore, the bio-templating process successfully introduced N and O heteroatoms into the carbon framework. These functional groups enhance the affinity between biochar and CO 2 through electronic interactions, ensuring excellent adsorption stability over multiple adsorption–desorption cycles. Isotherm and kinetic analyses indicate that CO 2 adsorption proceeds via a multilayer diffusion-controlled mechanism. Moreover, density functional theory (DFT) calculations reveal that N dopants facilitate CO 2 capture through hydrogen bonding, whereas O atoms strengthen dipole–quadrupole interactions. Overall, this study presents a sustainable and cost-effective approach to produce high-performance CO 2 adsorbents from waste biomass and provides comprehensive mechanistic insights into how heteroatom doping promotes CO 2 capture efficiency.