Catalyst-free development of N-doped microporous carbons for selective CO2 separation

Abstract

Herein, we present the rational development of N-doped microporous carbons (NMCs) through a catalyst-free nucleophilic substitution reaction of rigid monomers, followed by temperature-controlled carbonization. NMC-700 shows a large specific surface area of 1571 m² g⁻¹, a high pore volume of 0.88 cm³ g⁻¹, and a micropore diameter of 4.2 Å with variable nitrogen contents. Notably, NMC-700 demonstrates an excellent CO₂ uptake of 212.1 mg g⁻¹ over benchmark adsorbents including MAPOP-4 (135 mg g⁻¹), CPOP-13 (168 mg g⁻¹), UTSA-50a (200.3 mg g⁻¹) and most reported carbon-based adsorbents at 273 K and 1 bar. More importantly, NMC-700 shows high CO₂/CH₄ selectivity (30) which is notably higher than that of recently reported adsorbents including PCTF-3 (6.0), CuPor-BPDC (6.0), BILP-16-AC (9.0), and MAPOP-4 (11.3) at 273 K and 1 bar. Our study shows that the high CO₂ uptake and excellent CO₂/CH₄ selectivity are achieved mainly due to the presence of desired functionalities and appropriate well-defined micropore structures in NMCs. Owing to their easily scalable synthetic method, catalyst-free development, and high-yield, the fabricated NMCs are considered as industrial adsorbents. Hence, these NMCs are very promising adsorbents in selective CO₂ separation from natural gas.