N-doped porous carbons derived from a polymer precursor with a record-high N content: Efficient adsorbents for CO₂ capture

N-doped porous carbons (NPCs) are characterized by well-developed porosity and N-doped active sites, which makes them suitable for CO₂ capture. However, their application in practice is obstructed by the relatively low N-doped content and unsatisfactory adsorption capacity. Herein, we report the synthesis of NPCs through the rational design of the precursor NUT-21 (NUT means Nanjing Tech University) with a record-high N content (up to 46.16%, wt). The NUT-21 was fabricated by the polymerization of two simple monomers of 2,4,6-tris(bromomethyl)mesitylene and 3,5-diamino-1,2,4-triazole with an unusually high N content of 70.67% (wt). With the carbonization of NUT-21 at different temperatures (500, 600, and 700 °C, respectively), a series of NPCs possessing various porosity and N contents are produced, successfully. For the NPC generated at 600 °C, the N content can reach 7.41% (wt), the surface area is 2208 m²/g, the micropore volume is 0.791 cm³/g, and the CO₂ capacity is up to 8.3 mmol/g at 273 K and 1 bar, which is much higher than those of benchmarks including 13X zeolite (4.1 mmol/g) and activated carbon (2.8 mmol/g), and most carbon-based adsorbents reported till now. It was proved in our previous studies that the ultrahigh N content of the precursor was beneficial for both the formation of developed porosity and the generation of abundant N-doped sites, which can give rise to superior capacity and selectivity of CO₂ capture. The NPCs obtained may offer to be highly promising candidates for CO₂ separation from gas mixtures including natural gas and flue gas.