Hierarchical porous carbon beads for selective CO₂ capture

Excessive CO₂ emissions from increased energy consumption are causing an environmental disaster that threatens humanity. Herein, we report the development of hierarchical porous carbon beads with interconnected micro- and mesopores for selective CO₂ capture. Hierarchical porous carbon beads were prepared by the carbonization of potassium-exchanged phenol formaldehyde resin (PFR) beads obtained from exchange of K⁺ to the PFR OH groups. Interestingly, the carbonized K₂CO₃-treated PFR (CPFRs) exhibited notably high surface areas and total pore volumes with interconnected micro- and mesopores. Based on their high porosities and nitrogen contents, the K₂CO₃-treated CPFR beads adsorbed 7.80 wt% CO₂ at 0.15 bar and 298 K, which is an adsorption result that is much higher than those (4.41 wt% and 5.33 wt%) of pristine and KOH-treated CPFR beads, respectively. More importantly, the ideal CO₂/N₂ selectivity (52.6) of K₂CO₃-treated CPFR beads, as determined by Henry's constant at room temperature, is superior to those (24.2 and 28.6) of pristine and KOH-treated CPFR beads, respectively. Breakthrough experiments with 15 % CO₂ in N₂, which has a similar partial pressure to the CO₂ partial pressure in flue gases from coal power plants, revealed that K₂CO₃-treated CPFR beads selectively adsorb 5.5 wt% of CO₂ over N₂. This selective CO₂ capacity is superior to those reported in other porous carbon materials. Therefore, to reduce CO₂ emissions, hierarchical porous carbon beads with interconnected micro- and mesopores can play an important role in CO₂ capture and separation.