Enhanced CO capturing over ultra-microporous carbon with nitrogen-active species prepared using one-step carbonization of polybenzoxazine for a sustainable environment.

Nitrogen-enriched porous carbon has been a promising material for CO capture in the recent decades. To enhance the performance of CO adsorption, both an N-active site and the textural properties are crucial determinants. Herein, ultra-microporous carbon with N-active species was prepared using two synthesis procedures: 1) one-step carbonization of a polybenzoxazine (PBZ) precursor at 800 °C, and 2) the CO activation process at 900 °C. The activated porous carbon had the higher specific surface area (943 m/g) and a total pore volume (0.51 cm/g) compared to un-activated porous carbon (335 m/g and 0.19 cm/g, respectively). In addition, the presence of N-active species such as pyridine-N, secondary-N, pyridone-N, and oxide-N in the carbon structures could be clearly observed in the high-resolution XPS spectra. The CO adsorption measurement was performed at 30 and 50 °C under a wide range of pressures (1-7 bar). The maximum amount of CO uptake was ca. 3.59 mmol/g for the activated porous carbon operated at 30 °C and a CO pressure of 7 bar, which was due to the high specific surface area and the large micropore volume. Specifically, carbon with a 3D interconnected pore structure, derived from the sol-gel process of the PBZ precursor, exhibited good structural stability and consequently led to better absorption capability under the high atmospheric pressure of CO. The enhanced CO adsorption capability for the as-prepared porous carbon was based on two mechanisms: physisorption as a result of textural properties and chemisorption as a result of the acid-base interaction between the basic N functionality and the acidic CO gas. All results suggested that ultra-microporous carbon with N-active species prepared from polybenzoxazine is a promising adsorbent for CO capture and storage, which can be used at a wide range of pressures and in many applications e.g. flue gas adsorption and natural gas production.