A cationic three‐dimensional (3D) metal−organic framework (MOF) sustained by an N , N '‐diethylformamide (DEF)‐solvated zigzag‐shaped Cd 5 cluster secondary building unit (SBU), [Et 2 NH 2 ] 2 [Cd 5 (BTB) 4 (DEF) 2 ]∙4.75DEF ( 1a , H 3 BTB = benzene‐1,3,5‐tribenzoic acid) shows flexible framework behavior and undergoes solvate exchange with CHCl 3 to yield [Et 2 NH 2 ] 2 [Cd 5 (BTB) 4 (DEF) 2 ]∙ x CHCl 3 ( 1b ) accompanied by changes to pore sizes and shapes. Unexpectedly, the DEF solvates coordinated to the central Cd 2+ could not be replaced by strongly donor pyridyl and dipyridyl ligands. Additionally, more electron‐deficient pyridyls preferentially coordinated to the flanking Cd 2+ of the Cd 5 SBU, as exemplified by [Et 2 NH 2 ] 2 [Cd 5 (BTB) 4 (DEF) 2 (PyCHO) 2 ]∙ x Sol ( 2a , PyCHO = 4‐pyridine aldehyde) and [Et 2 NH 2 ] 2 [Cd 5 (BTB) 4 (DEF) 2 (PyAc) 2 ]∙ x Sol ( 2b , PyAc = 4‐acetylpyridine). Density functional theory (DFT) calculations were used to help understand these counterintuitive observations.

中文翻译：

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带有N，N'-二乙基甲酰胺（DEF）-溶剂化Cd5团簇二级建筑单元的柔性金属有机框架中的非常规吡啶基配体

阳离子三维（3D）金属有机骨架（MOF），由N，N'-二乙基甲酰胺（DEF）呈锯齿形的Cd 5簇二级建筑单元（SBU）支撑，[Et 2 NH 2] 2 [ Cd 5（BTB）4（DEF）2]∙4.75DEF（1a，H 3 BTB =苯-1,3,5-三苯甲酸）显示灵活的骨架行为，并与CHCl 3进行溶剂交换，生成[Et 2 NH 2 ] 2 [Cd 5（BTB）4（DEF）2]∙x CHCl 3（1b）伴随着孔径和形状的变化。出乎意料的是，与中心Cd 2+配位的DEF溶剂化物无法被强供体吡啶基和二吡啶基配体取代。此外，更多的缺电子吡啶基优先与Cd 5 SBU的侧翼Cd 2+配位，例如[Et 2 NH 2] 2 [Cd 5（BTB）4（DEF）2（PyCHO）2]∙x Sol （2a，PyCHO = 4-吡啶醛）和[Et 2 NH 2] 2 [Cd 5（BTB）4（DEF）2（PyAc）2]∙x Sol（2b，PyAc = 4-乙酰基吡啶）。密度泛函理论（DFT）计算用于帮助理解这些与直觉相反的观察结果。