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

Abstract

AbstractPorous 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.