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

Abstract

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.