School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, Georgia 30332-0100, USA.
J Am Chem Soc. 2012 Mar 7;134(9):4313-23. doi: 10.1021/ja2108239. Epub 2012 Feb 28.
Electrostatic interactions are a critical factor in the adsorption of quadrupolar species such as CO(2) and N(2) in metal-organic frameworks (MOFs) and other nanoporous materials. We show how a version of the semiempirical charge equilibration method suitable for periodic materials can be used to efficiently assign charges and allow molecular simulations for a large number of MOFs. This approach is illustrated by simulating CO(2) and N(2) adsorption in ~500 MOFs; this is the largest set of structures for which this information has been reported to date. For materials predicted by our calculations to have promising adsorption selectivities, we performed more detailed calculations in which accurate quantum chemistry methods were used to assign atomic point charges, and molecular simulations were used to assess molecular diffusivities and binary adsorption isotherms. Our results identify two MOFs, experimentally known to be stable upon solvent removal, that are predicted to show no diffusion limitations for adsorbed molecules and extremely high CO(2)/N(2) adsorption selectivities for CO(2) adsorption from dry air and from gas mixtures typical of dry flue gas.
静电相互作用是在金属有机骨架（MOF）和其他纳米多孔材料中吸附四极物种（如 CO(2)和 N(2)）的关键因素。我们展示了如何使用适用于周期性材料的半经验电荷平衡方法的一个版本来有效地分配电荷，并允许对大量 MOF 进行分子模拟。通过模拟约 500 个 MOF 中的 CO(2)和 N(2)吸附来说明这种方法；这是迄今为止报告的此类信息的最大结构集合。对于我们的计算预测具有有前途的吸附选择性的材料，我们进行了更详细的计算，其中使用精确的量子化学方法来分配原子点电荷，并使用分子模拟来评估分子扩散率和二元吸附等温线。我们的结果确定了两种 MOF，实验上已知在去除溶剂后是稳定的，预计对于吸附分子没有扩散限制，并且对于从干燥空气中和从干燥烟道气典型的混合气体中吸附 CO(2)具有极高的 CO(2)/N(2)吸附选择性。
