In-situ ion-activated carbon nanospheres with tunable ultramicroporosity for superior CO₂ capture

Ultramicroporous carbon materials play a critical role in CO₂ capture and separation, however facile approaches to design ultramicroporous carbon with controllable amount, ratio and size of pores are still challenging. Herein, a novel strategy to design carbon nanospheres with abundant, uniform, and tunable ultramicroporosity was developed based on an in-situ ionic activation methodology. The adjustable ion-exchange capacity derived from oxidative functionalization was found capable of substantially governing the ionic activation and precisely regulating the ultramicroporosity in the resultant product. An ultrahigh ultramicropore content of 95.5% was achieved for the optimally-designed carbon nanospheres, which demonstrated excellent CO₂ capture performances with extremely high capacities of 1.58 mmol g⁻¹ at typical flue gas conditions and 4.30 mmol g⁻¹ at 25 °C and ambient pressure. Beyond that, the CO₂ adsorption mechanism in ultramicropore was also investigated through molecular dynamics simulation to guide the pore size optimization. This work provides a novel and facile guideline to engineer carbon materials with abundant and tunable ultramicroporosity towards superior CO₂ capture performance, which also delivers great potential in extensive applications such as water purification, catalysis, and energy storage.