Superior carbon-based CO2 adsorbents prepared from poplar anthers

A series of renewable nitrogen-containing granular porous carbons with developed porosities and controlled surface chemical properties were prepared from poplar anthers. The preparation conditions such as pre-carbonization and activation temperatures and KOH amount significantly influence the structures and chemical compositions of the porous carbons, the CO2 adsorption capacities of which are highly dependent on their pore structures, surface areas, nitrogen contents and adsorption conditions. The sample with developed microporosity, especially with the pores between 0.43 and 1 nm and high nitrogen content shows high CO2 adsorption capacity at 1 bar and 25 °C. In contrast, when the adsorption pressure is higher than 5 bar, its CO2 adsorption capacity is dominated by its surface area, and more accurately by its pore volume. Irrespective of this, if the pressure was decreased to 0.1 bar, its CO2 capture ability is closely correlated to its nitrogen content but not to its porosity. By optimizing the preparation conditions, a porous carbon with a surface area of 3322 m2 g−1 and a CO2 adsorption capacity as high as 51.3 mmol g−1 at 50 bar and 25 °C was prepared.