N-Doped Polypyrrole-Based Porous Carbons for CO2 Capture

Highly porous N‐doped carbons have been successfully prepared by using KOH as activating agent and polypyrrole (PPy) as carbon precursor. These materials were investigated as sorbents for CO2 capture. The activation process was carried out under severe (KOH/PPy = 4) or mild (KOH/PPy = 2) activation conditions at different temperatures in the 600–800 °C range. Mildly activated carbons have two important characteristics: i) they contain a large number of nitrogen functional groups (up to 10.1 wt% N) identified as pyridonic‐N with a small proportion of pyridinic‐N groups, and ii) they exhibit, in relation to the carbons prepared with KOH/PPy = 4, narrower micropore sizes. The combination of both of these properties explains the large CO2 adsorption capacities of mildly activated carbon. In particular, a very high CO2 adsorption uptake of 6.2 mmol·g−1 (0 °C) was achieved for porous carbons prepared with KOH/PPy = 2 and 600 °C (1700 m2·g−1, pore size ≈ 1 nm and 10.1 wt% N). Furthermore, we observed that these porous carbons exhibit high CO2 adsorption rates, a good selectivity for CO2‐N2 separation and it can be easily regenerated. N‐doped porous carbons exhibiting high surface areas, large pore volumes and a porosity in the micro‐/mesopore range are prepared by using a one‐step synthesis strategy based on the chemical activation of polypyrrole. The prepared activated carbons exhibit a large CO2 uptake (up to 3.9 mmol CO2 g−1 at 25 °C), a good selectivity for CO2‐N2 separation, and they can be easily regenerated.