Metal–Organic Framework (MOF) Defects under Control: Insights into the Missing Linker Sites and Their Implication in the Reactivity of Zirconium-Based Frameworks

For three-dimensional (3D) metal–organic frameworks (MOFs), the presence and nature of structural defects has been recognized as a key factor shaping the material’s physical and chemical behavior. In this work, the formation of the “missing linker” defects has been addressed in the model biphenyl-4,4′-dicarboxylate (bpdc)-based Zr MOF, UiO-67. The defect showed strong dependence on the nature of the modulator acid used in the MOF synthesis; the defects, in turn, were found to correlate with the MOF physical and chemical properties. The dynamic nature of the Zr6 (node)-monocarboxylate bond showed promise in defect functionalization and “healing”, including the formation of X-ray-quality “defect-free” UiO-67 single crystals. Chemical transformations at defect sites have also been explored. The study was also extended to the isoreticular UiO-66 and UiO-68′ systems.针对三维（3D）金属有机框架（metal–organic frameworks, MOFs），其结构缺陷的存在与本质已被证实是调控该类材料物理与化学性能的核心因素。本研究以典型的联苯-4,4′-二羧酸酯（biphenyl-4,4′-dicarboxylate, bpdc）基锆基MOF UiO-67为对象，探究了"缺失连接体"缺陷的形成机制。该缺陷与MOF合成过程中使用的调节剂酸的性质密切相关；反过来，缺陷的存在也与MOF的物理化学性能存在关联。Zr6（节点）-单羧酸酯键的动态特性为缺陷功能化与"修复"提供了可行途径，包括制备出具备X射线衍射级品质的"无缺陷"UiO-67单晶。此外，本研究还对缺陷位点处的化学转化过程进行了探究，并将研究范围拓展至同构衍生的UiO-66与UiO-68′体系。