Hierarchically Structured Porous Nitrogen-Doped Carbon for Highly Selective CO<sub>2</sub> Capture

Abstract

Nitrogen-doping has proven to be an effective strategy for enhancing the CO<sub>2</sub> adsorption capacity of carbon-based adsorbents. However, it remains challenging to achieve a high doping level of nitrogen (N) and a significant porosity in a carbon material simultaneously. Here we report a facile method that enables the fabrication of ordered macroporous nitrogen-doped carbon with the content of N as high as 31.06 wt %. Specifically, we used poly­(EGDMA-<i>co</i>-MAA) microspheres as a template to fabricate the structure which can strongly interact with melamine (the precursor of nitrogen-doped carbon framework), self-assemble into three-dimensionally ordered structure, and be easily removed afterward. Upon chemical activation, significant microporosity is generated in this material without degrading its ordered macroporous structure, giving rise to a hierarchically structured porous nitrogen-doped carbon in which a remarkable N content (14.45 wt %) is retained. This material exhibits a moderate CO<sub>2</sub> adsorption capacity (2.69 mmol g<sup>–1</sup> at 25 °C and 3.82 mmol g<sup>–1</sup> at 0 °C under 1 bar) and an extraordinarily high CO<sub>2</sub>/N<sub>2</sub> selectivity (134), which is determined from the single-component adsorption isotherms based on the ideal adsorption solution theory (IAST) method. This value far exceeds the CO<sub>2</sub>/N<sub>2</sub> selectivity of thus-far reported carbon-based adsorbents including various nitrogen-doped ones. We believe that such an unprecedented CO<sub>2</sub>/N<sub>2</sub> selectivity is largely associated with the unusually high N content as well as the partially graphitic framework of this material

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