Gas separation in microporous materials: A computational study of the influence of structural features on the selectivity

在这个项目中，计算化学技术被用来评估不同的微孔材料(沸石、金属有机骨架、纳米孔分子晶体)在基于吸附的气体分离应用中的潜力。特别强调对特定相互作用中心的作用进行详细的分析，如骨架外阳离子、配位不饱和金属中心或官能团，以及对微孔的限制。该研究针对与工业过程相关的不同气体混合物，例如脱除烟道气或天然气中的二氧化碳，或分离烷烃/烯烃混合物。该项目遵循分层方法：首先，使用经验相互作用参数对各种候选材料进行宏正则蒙特卡罗(GCMC)模拟，从而初步估计吸附选择性。然后对在此筛选中确定的最有趣的系统进行更全面的GCMC分离性质研究。详细分析了所观察到的分离行为与材料的结构性质(特定相互作用位置、孔大小、孔拓扑)之间的关系。在接下来的工作中，进行了量子化学计算，以更好地了解特定位置和吸附分子之间的相互作用。通过分子动力学计算分析了这些位置对客体分子扩散的影响。在项目的最后部分，预测了假设的沸石的吸附性能。由于其结构的多功能性，这些系统特别适合于系统地研究孔隙拓扑的影响。

In this project, computational chemistry techniques are employed to evaluate the potential of different microporous materials (zeolites, metal-organic frameworks, nanoporous molecular crystals) for adsorption-based gas separation applications. A particular emphasis is put on a detailed analysis of the role of specific interaction sites, such as extra-framework cations, coordinatively unsaturated metal sites, or functional groups, in conjunction with confinement to micropores. The investigation addresses different gas mixtures that are of relevance for industrial processes, for example in the removal of carbon dioxide from flue gases or from natural gas, or in the separation of alkane/alkene mixtures.The project follows a hierarchical approach: Firstly, grand-canonical Monte Carlo (GCMC) simulations using empirical interaction parameters are carried out for a wide variety of candidate materials, permitting an initial estimation of the adsorption selectivity. A more thorough GCMC study of the separation properties is then carried out for the most interesting systems that were identified in this screening. The relationships between the observed separation behaviour and the structural properties of the material (specific interaction sites, pore size, pore topology) are analyzed in detail. In the following, quantum-chemical calculations are carried out to develop a better understanding of the interactions between specific sites and adsorbed molecules. Molecular dynamics calculations are performed to analyze the impact of these sites on the diffusion of guest molecules. In the final part of the project, the adsorption properties of hypothetical zeolites are predicted. Due to their structural versatility, these systems are particularly well suited for a systematic study of the influence of the pore topology.