Abstract: Combining the advantages of high selectivity of amine groups, high capacity of microporous zeolite, and high transportation of mesoporous structures, amine modified micro/mesoporous composites may exhibit promising CO₂ adsorption capability. In this study, a full-atomic mimetic amine modified micro/mesoporous composite of AM-5A-MCM-41 was constructed. CO₂ adsorption and separation performance on AM-5A- MCM-41 composite were investigated by the grand canonical Monte Carlo (GCMC), in which a specific combining rule was used to describe the weak chemical interaction between CO₂ molecule and amine group. The simulation results demonstrate that CO₂ is preferentially adsorbed around amine groups, which is grafted at the surface of mesoporous channels; and the CO₂ adsorption capacity and its isosteric heat are greatly improved on AM-5A-MCM-41, whereas those of N₂ are almost kept unchanged. For the separation of mixed gas of CO₂ and N₂, both CO₂ adsorption capacity and CO₂/N₂ selectivity are greatly improved, due to the enhanced interaction between CO₂ molecules and amine groups. The chemisorption plays a significant role in the capture of CO₂ at low pressures and high temperature, giving a selectivity as high as 87.0 at 573 K and 100 kPa. The overall results show that molecular simulations serve as a powerful implement to assist the design and development of new promising CO₂ adsorbents, highlighting the importance of this approach.

Key words: molecular simulation, CO₂ adsorption, amine modification, micro/mesoporous, selectivity

摘要： 构建了氨基修饰微孔/介孔复合材料AM-5A-MCM-41的全原子模型，采用巨正则Monte Carlo（GCMC）方法研究了它的CO₂吸附分离性能，采用加权混合规则来描述氨基和CO₂分子的弱化学作用。模拟结果表明，CO₂分子优先吸附在复合材料介孔表面的氨基附近，CO₂纯气体的吸附量和吸附热有了显著提高，而N₂的吸附量和吸附热则基本不受影响。对于CO₂和N₂的混合气分离，由于复合材料对CO₂的弱化学吸附作用，显著提高了CO₂吸附量和吸附选择性，在573 K和100 kPa时CO₂/N₂的选择性达到了87.0。通过分子模拟研究可以从微观角度了解CO₂在氨基修饰的微孔/介孔复合材料中的吸附分离的细节和机理，为实验设计和合成高效CO₂吸附剂提供指导。

关键词: 分子模拟, 二氧化碳吸附, 氨基修饰, 微孔/介孔材料, 选择性