The nature of adsorption between MOF absorbent and SO remains a challenging issue due to the difficulty in understanding their interaction force and dynamic behavior on molecular level. Herein, a new series of M-MOF-74 (M = Co, Ni, Zn) with high SO adsorption performance were synthesized through an improved solvothermal method. The interaction between M-MOF-74 (M = Co, Ni, Zn) and SO was revealed by combining in-situ infrared spectroscopy and density functional theory (DFT) calculations. It was found that Zn-MOF-74 shows excellent SO uptakes (8.16 mmol g), significantly higher than that of Co-MOF (6.11 mmol/g) and Ni-MOF (6.36 mmol/g). These results were consistent with SO binding energies calculated at optimal adsorption sites, which were −11.1 kcal/mol, −12.2 kcal/mol, −18.2 kcal/mol for M-MOF-74 (M = Co, Ni, Zn), respectively. The specific adsorption behavior of Zn-MOF-74 towards SO is attributed to its higher negative attraction of electrostatic potential(∼48.2 kcal/mol)and van der Waals pulling forces (∼−2.6 kcal/mol). The higher interaction force between Zn-MOF-74 and SO was elucidated not only by their strong dominant dispersion interactions, but also by the formation of hydrogen bonding between SO and benzene ring, as demonstrated by independent gradient model (IGM) and infrared analysis. What's more, a unique radial SO movement with high speed of 323 p.m./ps, which was much higher than that of traditional molecular sieve (∼240 p.m./ps) adsorbent, were observed towards Zn-MOF-74 framework wall. Then the pore size of MOF-74 and SO motion trajectory was analyzed by Molecular Dynamics. This work gives insight into mechanisms on SO adsorption in MOFs.

中文翻译：

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难处理的气态 SO2 与新型吸附剂的相互作用——金属有机框架：M-MOF-74（M = Co、Ni、Zn）

由于难以理解它们在分子水平上的相互作用力和动态行为，MOF 吸收剂和 SO 之间的吸附性质仍然是一个具有挑战性的问题。在此，通过改进的溶剂热法合成了一系列具有高 SO 吸附性能的新系列 M-MOF-74（M = Co、Ni、Zn）。通过结合原位红外光谱和密度泛函理论（DFT）计算揭示了M-MOF-74（M = Co、Ni、Zn）和SO之间的相互作用。结果发现，Zn-MOF-74 显示出优异的 SO 吸收率（8.16 mmol/g），显着高于 Co-MOF（6.11 mmol/g）和 Ni-MOF（6.36 mmol/g）。这些结果与在最佳吸附位点计算的 SO 结合能一致，M-MOF-74（M = Co、Ni、Zn）分别为 -11.1 kcal/mol、-12.2 kcal/mol、-18.2 kcal/mol 。 Zn-MOF-74对SO的特定吸附行为归因于其较高的静电势负吸引力（∼48.2 kcal/mol）和范德华拉力（∼−2.6 kcal/mol）。独立梯度模型（IGM）和红外分析证明，Zn-MOF-74 和 SO 之间较高的相互作用力不仅是由于它们强的占主导地位的色散相互作用，而且是由于 SO 和苯环之间形成氢键。此外，在 Zn-MOF-74 框架壁上观察到独特的径向 SO 运动，速度高达 323 pm/ps，远高于传统分子筛 (∼240 pm/ps) 吸附剂。然后通过分子动力学分析MOF-74的孔径和SO运动轨迹。这项工作深入了解了 MOF 中 SO 吸附的机制。