Developing novel carbon adsorbents with high CH₄ adsorption capacity for CH₄/N₂ separation is always an imperative and challenging process, which could effectively mitigate global warming and fully utilizes low-concentration coalbed methane (CBM). Herein, a green and effective method is proposed to synthesize flexible porous carbon monolith without using binder and toxic/corrosive agents. Melamine sponge is selected as carbon source and nitrogen source, simultaneously as a three-dimensional flexible supporting framework, and glucose is used as second carbon source. The environment-friendly chemical agent potassium oxalate monohydrate (K₂C₂O₄·H₂O) is used as activator to control the ultramicroporous structure and O&N co-doped property via changing the activation temperature and the amount of K₂C₂O₄·H₂O. The optimal sample exhibits a record-high CH₄ adsorption capacity of 1.95 mmol/g and a good IAST CH₄/N₂ selectivity of 5.58 at 25 °C and 1.0 bar, outperforming many other adsorbents. Above results originate from the synergistic effect of its high ultramicropore volume (0.26 cm³ g⁻¹), suitable ultramicropore size (centered at 0.55 nm), abundant –OH groups and a certain amount of –COOH groups, as well as N-6 and N-5 species. Dynamic breakthrough experiments further approve that CH₄/N₂ mixture can be well separated on this carbon material under realistic condition. This work introduces a new pathway to prepare O&N co-doped flexible ultramicroporous carbon monolith adsorbent for efficient capture of CH₄ from low-concentration CBM

中文翻译：

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氧/氮共掺杂柔性超微孔碳整体，具有高 CH4 吸附能力，用于从低浓度煤层气中分离 CH4/N2


开发具有高 CH₄ 吸附能力的新型碳吸附剂用于 CH₄/N₂ 分离始终是一个势在必行且具有挑战性的过程，它可以有效缓解全球变暖并充分利用低浓度煤层气 （CBM）。在此，提出了一种绿色有效的方法来合成柔性多孔碳整体，而无需使用粘合剂和有毒/腐蚀剂。选择三聚氰胺海绵作为碳源和氮源，同时作为三维柔性支撑框架，葡萄糖作为第二碳源。环保型化学试剂草酸钾一水合物（K₂C₂O₄·H₂O） 用作活化剂，通过改变活化温度和 K₂C₂O₄·H₂O.最佳样品在 25 °C 和 1.0 bar 下表现出创纪录的 CH₄ 吸附载量 1.95 mmol/g 和 5.58 的良好 IAST CH₄/N₂ 选择性，优于许多其他吸附剂。上述结果源于其高超微孔体积 （0.26 cm^{3 g-1}）、合适的超微孔尺寸（以 0.55 nm 为中心）、丰富的 -OH 基团和一定量的 -COOH 基团，以及 N-6 和 N-5 物种的协同效应。动力学突破实验进一步证实，在现实条件下，CH₄/N₂ 混合物可以在这种碳材料上很好地分离。本工作为制备 O&N 共掺杂柔性超微孔碳整体吸附剂提供了一种新的途径，用于从低浓度 CBM 中高效捕获 CH₄