Nitrogen-Doped Ultrahigh Microporous Carbons Derived from Two Nitrogen-Containing Post-Cross-Linked Polymers for Efficient CO₂ Capture

The nitrogen (N)-doped porous carbons have always been one of the important categories of the adsorbents for CO₂ capture. Herein, we prepared N-doped porous carbons from two kinds of N-containing post-cross-linked polymers (HPDV and HPDN) by KOH activation carbonization. By changing the carbonization temperature and KOH dosage, the porosity and chemical structure of two porous carbons were effectively tuned, and strictly N-doped microporous carbons with ultrahigh microporosity were acquired (80.00–90.00%). They exhibited high CO₂ uptake (3.93–6.56 mmol/g at 273 K and 1 bar), acceptable CO₂/N₂ selectivity (IAST: 21.5–39.7), moderate isosteric heat of adsorption (20.3–41.8 kJ/mol), and good reusability. Moreover, the adsorption energy results from DFT calculation indicated that diversified N-functional groups had improved CO₂ uptake through Lewis acid–base interactions and hydrogen-bonding interactions, and the study further clarified that the large micropore volume, especially the ultramicropore volume (V_ultra, d < 0.8 nm), played a key role for CO₂ capture. These porous carbons developed therein become promising CO₂ adsorbents.