Dual‐Cation Activation of N‐Enriched Porous Carbons Improves Control of CO₂ and N₂ Adsorption Thermodynamics for Selective CO₂ Capture

Abstract

Porous carbons have potential to facilitate energy‐efficient separation of CO2 from post‐combustion flue gas. However, the complicated interplay between chemical and textural properties has prevented a comprehensive understanding of selective CO2 adsorption. This study demonstrates how dual cation activation of carbons serves as a synthetic platform to help modulate porosity independent of nitrogen content. For samples derived from nitrogen‐poor precursors, surface areas deviated significantly (2200–4500 m2 g−1) at a constant total nitrogen content (2.3 ± 0.3 at %). Surface area changed less for samples derived from nitrogen‐rich precursors (400–675 m2 g−1 at 23.1 ± 0.1 at % N). Rigorous structure‐function and thermodynamic analysis of these carbons not only helped to uncover the nature of the different adsorption sites, but also established a fundamental linear free energy exchange relationship. This coupled with material property correlations informed the properties that facilitated selective capture of CO2. Critically, for these physisorptive carbons, selectivity is almost entirely a function of relative porosity and chemical adsorbent‐adsorbate interactions play a negligible role.