High-performance CO2 sorbents from algae

Highly porous N-doped carbon materials with apparent surface areas in the 1300–2400 m2 g−1 range and pore volumes up to 1.2 cm3 g−1 have been synthesized from hydrothermal carbons obtained from mixtures of algae and glucose. The porosity of these materials is made up of uniform micropores, most of them having sizes <1 nm. Moreover, they have N contents in the 1.1–4.7 wt% range, and the heteroatom is mainly a pyridone-type structure. These microporous carbons present unprecedented large CO2 capture capacities, up to 7.4 mmol g−1 (1 bar, 0 °C). The importance of the pore size on the CO2 capture capacity of microporous carbon materials is clearly demonstrated. Indeed, a good correlation between the CO2 capture capacity at sub-atmospheric pressure and the volume of narrow micropores is observed. The results suggest that pyridinic-N, pyridonic/pyrrolic-N and quaternary-N do not contribute significantly to the CO2 adsorption capacity, owing probably to their low basicity in comparison with amines. These findings will help the design of high-performance CO2 capture sorbents.