Edge-nitrogen rich porous carbons for acid gases capture

Abstract

The functionalities of N-doped carbons primarily rely on the exposed edge-nitrogen sites, which play a critical role in SO₂ and CO₂ adsorption. Rationally creating edge-nitrogen sites so as to promote their applications in various areas has not yet been well resolved. Herein, we developed ZnCl₂-coordination-pyrolysis to design large specific surface area (1220 ∼ 1645 m²/g) and edge-nitrogen rich porous carbons (E-NPC-x), where chitosan was employed as the carbon precursor. Similar to animals revealing new skin after shedding their old one, the migration and evaporation of zinc during pyrolysis leave abundant micro-mesoporosity, adjacent to which high proportion of edge-nitrogen sites was created due to strong coordination interaction between Zn²⁺ and nitrogen atoms. This feature significantly enhances the performance of E-NPC-x for acid gases capture, showing high SO₂ capacities with fast adsorption equilibrium rates (14.6 mmol/g, 25 °C, 1.0 bar), and improved SO₂/N₂ (0.1/0.9) IAST selectivities (251.1). The room-temperature diluted CO₂ (2.0 vol%) under flue gas conditions, can be efficiently and precisely separated over the E-NPC-x with high breakthrough capacities (0.49 mmol/g). The nitrogen efficiencies of E-NPC-x for acid gases capture surpass those of current literature-reported N-doped porous carbons, underscoring its potential as a highly effective solution for mitigating environmental pollution. This work highlights a significant advance in the design of functional materials for environmental protection, addressing pressing challenges in acid gas management and contributing to a cleaner and more sustainable future.