The pillared layer framework DUT-8(Zn) (Zn₂(2,6-ndc)₂(dabco), 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo-[2.2.2]-octane, DUT = Dresden University of Technology) is a prototypical switchable MOF, showing characteristic adsorption and desorption induced open phase (op) to closed phase (cp) transformation associated with huge changes in cell volume. We demonstrate switchability strongly depends on a framework-specific critical particle size (d_crit). Superposed, the solvent removal process (pore desolvation stress contracting the framework) significantly controls the cp/op ratio after desolvation and, subsequently, the adsorption induced switchability characteristics of the system. After desolvation, the dense cp phase of DUT-8(Zn) shows no adsorption-induced reopening and therefore is non-porous for N₂ at 77 K and CO₂ at 195 K. However, polar molecules with a higher adsorption enthalpy, such as chloromethane at 249 K and dichloromethane (DCM) at 298 K can reopen the macro-sized crystals upon adsorption. For macro-sized particles, the outer surface energy is negligible and only the type of metal (Zn, Co, Ni) controls the DCM-induced gate opening pressure. The node hinge stiffness increases from Zn to Ni as confirmed by DFT calculations, X-ray crystal structural analysis, and low frequency Raman spectroscopy. This softer Zn-based node hinges and overall increased stabilization of cp vs. op phase shift the critical particle size at which switchability starts to become suppressed to even lower values (d_crit < 200 nm) as compared to the Ni-based system (d_crit ≈ 500 nm). Hence, the three factors affecting switchability (energetics of the empty host, (E_op–E_cp) (I), particle size (II), and desolvation stress (III)) appear to be of the same order of magnitude and should be considered collectively, not individually.

中文翻译：

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通过晶体尺寸工程定制吸附诱导的柱状MOF的可切换性。

柱状层框架DUT-8（Zn）（Zn ₂（2,6-ndc）₂（dabco），2,6-ndc = 2,6-萘二甲酸，dabco = 1,4-二氮杂双环-[2.2.2] -辛烷，DUT =德累斯顿工业大学）是一种典型的可转换MOF，显示出特征性的吸附和解吸诱导的开放相（op）到封闭相（cp）的转化，与细胞体积的巨大变化有关。我们证明可切换性在很大程度上取决于特定于框架的临界粒度（d _crit）。叠加后，去除溶剂的过程（孔的去溶剂应力使构架收缩）显着控制了去溶剂后的cp / op比，进而控制了系统引起的吸附诱导的可切换性。脱溶剂后，DUT-8（Zn）的致密cp相没有显示出吸附引起的重新开放，因此对于N ₂在77 K和CO _2下是无孔的然而，具有较高吸附焓的极性分子（例如249 K的氯甲烷和298 K的二氯甲烷（DCM））可以在吸附后重新打开大尺寸晶体。对于大尺寸颗粒，外表面能量可以忽略不计，只有金属类型（Zn，Co，Ni）控制DCM引起的闸门打开压力。DFT计算，X射线晶体结构分析和低频拉曼光谱证实，节点铰链刚度从Zn到Ni增加。这种较软的Zn类节点的铰链和整体增加CP的稳定化与运算相移临界粒径在该可转换开始成为抑制到更低的值（d_爆击相比于Ni基系统<200nm）的（d_暴击≈500 nm）。因此，影响切换性的三个因素（空主体的能量，（E _op – E _cp）（I），粒径（II）和去溶剂化应力（III））似乎处于相同的数量级，应为集体考虑，而不是个别考虑。