The thermo‐structural behavior of metal‐organic framework (MOF) precursors is responsible for regulating the introduction of defects in MOF structures during synthesis. In this paper, factors affecting the flexibility of MIL‐101(Cr) half‐secondary building units (half‐SBUs) are evaluated in solution using enhanced sampling methods. In particular, entropic and enthalpic contributions to the conformational free energy landscape of isolated MIL‐101(Cr) half‐SBUs are calculated in water, in the presence and absence of ionic species (Na⁺ and F⁻), and in N, N‐dimethylformamide (DMF). This analysis leads to the observation that the interplay between enthalpy and entropy determines the most probable conformational state for half‐SBUs. This observation extends to the most relevant SBU intermediate, in which conformational entropy plays a key role in stabilizing configurations that differ from those found in the MIL‐101(Cr) crystal structure. The findings highlight the importance of explicitly considering entropic effects, associated with finite‐temperature sampling when estimating the relative stability of different conformers of SBUs.

中文翻译：

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焓和熵贡献在MIL-101（Cr）二级建筑单元的构象自由能景观中的作用

金属有机骨架（MOF）前体的热结构行为负责调节合成过程中MOF结构中缺陷的引入。在本文中，使用增强采样方法在解决方案中评估了影响MIL-101（Cr）半中等建筑单元（半SBU）灵活性的因素。到的构象的自由能风景特别地，熵和焓贡献分离MIL-101（Cr）的半的SBU在水中计算，在离子物质（钠的存在和不存在⁺和F ^- ），和在Ñ，Ñ-二甲基甲酰胺（DMF）。该分析导致观察到，焓和熵之间的相互作用决定了半SBU的最可能构象状态。该观察结果扩展到最相关的SBU中间体，其中构象熵在稳定构型方面起着关键作用，该构型不同于MIL-101（Cr）晶体结构中的构象。这些发现凸显了在估计不同SBU构象异构体的相对稳定性时，明确考虑与有限温度采样相关的熵效应的重要性。