Engineering Porous Carbons from Furfural-Derived Humins toward CO₂ Adsorption

Furfural-derived humins were produced through acid-catalyzed hydrothermal synthesis, and a series of humin-based carbon materials with different pore structures were prepared via high-temperature carbonization and KOH activation. It was found that the carbon material activated at 800 °C with a KOH-to-humin ratio of 2/3 exhibited excellent CO₂ adsorption performance, whereby the activation temperature and KOH ratio synergistically modulated the porous structure. At 0 °C and 1 bar, its adsorption capacity reached 6.06 mmol/g, and the CO₂ uptake was highly linearly correlated with the volume of micropores smaller than 0.79 nm. Moreover, the 800 °C-2/3KOH material has exhibited an excellent CO₂/N₂ adsorption selectivity of 25.16, a moderate heat of adsorption (14-24 kJ/mol), and good recyclability. This study provides a novel approach to valorize humin-based porous carbons as efficient, sustainable, and economical CO₂ adsorbents.