CO₂ capture by nitrogen-doped porous carbons derived from nitrogen-containing hyper-cross-linked polymers

The N-containing hyper-cross-linked polymers with different porosity and polarity were prepared from 4-vinylbenzyl chloride and 4-vinyl pyridine by the suspension polymerization and Friedel-Crafts reaction. A carbonization process by KOH chemical activation was carried out for the N-containing hyper-cross-linked polymers, and hence a series of N-doped porous carbons (NDPC) was easily fabricated. These porous materials were comparatively evaluated for CO₂ adsorption. The NDPC were much more efficient than the N-containing hyper-cross-linked polymers for the CO₂ capture and the CO₂ uptake had a linear correlation to the ultramicropore volume (d ≤ 0.8 nm) with R² = 0.9737. NDPC-10% possessed the highest CO₂ uptake around 270 mg/g, and had the sufficient CO₂/N₂ selectivity of 20.2 at 273 K and 1.0 bar. The CO₂/N₂ selectivity of the N-containing hyper-cross-linked polymers was much higher than the NDPC due to the higher nitrogen content. The isosteric heat of adsorption on the N-containing hyper-cross-linked polymers ranged 29.0-41.2 kJ/mol while that on the NDPC was much lower (24.6-29.2 kJ/mol). The NDPC developed in this study may provide promising candidates for the CO₂ capture.