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 (Vultra, d < 0.8 nm), played a key role for CO2 capture. These porous carbons developed therein become promising CO2 adsorbents.