Fine tuning CO2 adsorption and diffusion behaviors in ultra-microporous carbons for favorable CO2 capture at moderate temperature

CO₂ capture from flue gas is one of the global urgent tasks. Adsorption separation of CO₂ is an energy-efficient way as compared to the absorption method. The central issue is to devise efficient adsorbents that work well under flue gas conditions with temperatures of 323–348 K and low CO₂ concentrations of 15%. In this work, we targeted this issue and proposed a well-controlled diffusion strategy, which is achieved over a series of poly(furfuryl alcohol)-derived carbons (PFCs) with dense and abundant ultra-micropores. As the adsorption temperature increased from 298 to 348 K, the CO₂ capture capacity is 54% kept for PFC-800, which is 1.2 times higher than that for samples without diffusion limitation. The capture of CO₂ is kinetics control at ambient temperature, however, at 348 K CO₂ with higher kinetic energy can overcome the restriction of the narrow pore entrance and the CO₂/N₂ selectivity for simulated flue gas composition increases from 20 to 40. Furthermore, the PFCs exhibit a high CO₂ volumetric adsorption capacity of 97 cm³ cm⁻³ at 298 K and 1 bar, benefiting the practical application deployed with an integrated adsorption column. The diffusion kinetics can be further tuned when altering the bulk phase into nanocoating, which would inspire their application in different scenarios.