重温小分子在金属有机骨架 Ni-MOF-74 中的竞争吸附,Inorganic Chemistry

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重温小分子在金属有机骨架 Ni-MOF-74 中的竞争吸附
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2022-12-31 , DOI: 10.1021/acs.inorgchem.2c03751
Haardik Pandey ₁ , Hao Wang ₂ , Liang Feng ₃ , Kun-Yu Wang ₃ , Hong-Cai Zhou ₃ , Jing Li ₂ , Timo Thonhauser ₁ , Kui Tan ₄

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为了精确评估金属有机骨架 (MOF) 在气体分离和纯化应用中的潜力，了解各种分子如何竞争性吸附在 MOF 内部至关重要。在这篇论文中，我们将原位红外光谱与从头算计算相结合，研究了原型结构 Ni-MOF-74中几种小分子（包括 CO、NO 和 CO _{2 ）的共吸附相关机制。}令人惊讶的是，我们发现 Ni-MOF-74 内部结合的 CO 的置换（结合能为 53 kJ/mol）很容易由 CO ₂暴露驱动，即使 CO ₂结合能明显较弱，仅为 41 kJ/mol；同时，结合力明显更强的 NO 分子 (90 kJ/mol) 无法轻易置换 Ni-MOF74 内部结合的 CO。这些结果表明，MOF 内部分子的单相结合能不能完全描述它们在其他客体分子存在下与 MOF 的相互作用。我们揭示了许多关键因素，例如控制共吸附过程的动力学势垒、分压、二级结合位点和客体-主体/横向相互作用，结合结合能，可以更好地描述气体混合物的行为和吸附在 MOF 内部。

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Revisiting Competitive Adsorption of Small Molecules in the Metal–Organic Framework Ni-MOF-74

To precisely evaluate the potential of metal–organic frameworks (MOFs) for gas separation and purification applications, it is crucial to understand how various molecules competitively adsorb inside MOFs. In this paper, we combine in situ infrared spectroscopy with ab initio calculations to investigate the mechanisms associated with coadsorption of several small molecules, including CO, NO, and CO₂ inside the prototypical structure Ni-MOF-74. Surprisingly, we find that the displacement of CO bound inside Ni-MOF-74 (binding energy of 53 kJ/mol) is readily driven by CO₂ exposure, even though CO₂ has a noticeably weaker binding energy of only 41 kJ/mol; meanwhile, the significantly more strongly binding NO molecule (90 kJ/mol) is not able to easily displace bound CO inside Ni-MOF74. These results show that single-phase binding energies of a molecule inside the MOF cannot completely describe their interaction with the MOF in the presence of other guest molecules. We unveil many crucial factors, such as the kinetic barrier, partial pressure, secondary binding sites, and guest–host/lateral interactions that control the coadsorption process and, combined with the binding energy, are better descriptors of the behavior and adsorption of gas mixtures inside MOFs.

更新日期：2022-12-31

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