Dynamic Tailoring Porosity and Surface Chemistry of Ultramicroporous Carbon Spheres for Highly Selective Post-combustion CO2 Capture

Carbon capture has emerged as a pivotal carbon neutrality technology for addressing greenhouse effect challenges. Porous carbons are one of the most promising adsorbents for CO2 capture and separation from flue gas, yet their traditional synthesis necessitates inert atmospheres to avoid oxidation, which greatly restricts the large-scale production at a low cost and advanced industrial applications. Herein, we propose an innovative pathway for large-scale fabrication of porous carbons via one-step pyrolysis in an air environment. Porosity and surface chemistry can be concurrently tailored by controlling the air-assisted pyrolysis process, and the optimization mechanism is unveiled in detail. The resultant materials feature well-interconnected hierarchical porosity with highly proportioned ultramicroporosity, uniform spherical morphology, and high surface heteroatom doping levels. By leveraging porosity and surface chemistry, the optimal sample exhibits superior CO2 capture behaviors of satisfactory CO2 uptake and ultrahigh selectivity. CO2/N2 selectivity reaches up to 160 at 0.15 bar and 25 °C, and it still achieves up to 76 at 1.0 bar and 25 °C, ranking it in the top 5% of the reported porous carbons. We explore the correlations between porosity, surface heteroatoms, and CO2 capture behaviors. Porosity has a decisive function on CO2 capture capacity and selectivity, especially ultramicroporosity, and surface heteroatoms doping could have a positive promotion in selectivity caused by extra CO2-philic sites. This work pioneers a feasible approach for large-scale directional design of functional porous carbons through air-assisted pyrolysis under mild conditions.