Selectable Microporous Carbons Derived from Poplar Wood by Three Preparation Routes for CO₂ Capture

Biomass-derived porous carbons are one kind of sustainable, extensive, and flexible carbon material for CO₂ capture. Here, we prepared several microporous carbons from poplar wood by three preparation routes. Especially, the residues of the poplar wood after the bioethanol process were explored as precursors to prepare activated carbon by KOH and ZnCl₂ activation. By the adjustment of the preparation routes and the optimization of the activation conditions, these porous carbons exhibited diversified morphology (sponge, nanosheets, and honeycomb structure), tunable porosity (specific surface areas: 511-2153 m²/g), and narrow micropore distribution (0.55-1.2 nm). These carbons had a high CO₂ uptake of up to 217 mg/g at 273 K and 1 bar, which was comparable with those of many N-doped porous carbons, and possessed moderate isosteric heat of CO₂ adsorption (21.1-43.2 kJ/mol), good cyclic ability, and high CO₂/N₂ selectivity (Henry's law: 44.0). The results indicated that CO₂ uptake of these carbons was mainly decided by their micropore volume (d < 1.0 nm) at 273 K and 1 bar. This work provides an important reference for preparing promising CO₂ adsorbents with tunable structures from similar biomass resources.