Metal–organic frameworks (MOFs) are some of the best materials for energy-efficient separations, like membranes and adsorption processes, due to their nanoporosity and tunability. To tune a MOF for optimum separation of molecules with sub-angstrom differences in size, which is a common challenge in industrial separations, precise control of the local pore environment is required. Here, we explore the concept of “3-dimensional” linkers, i.e., linkers that contain sterically bulky non-planar cores, as a means to attain sub-angstrom control over MOF pore size and to control structural flexibility. In particular, the introduction of 3-dimensional linkers (3DLs) is shown to hinder global breathing transitions in MOFs. Because these linkers occupy a consistent volume regardless of their orientation, they also allow for precise size-based separation of very similar molecules, such as hexane isomers. Furthermore, we discuss the thermal stability of a subset of these materials, characterized through variable temperature X-ray diffraction and porosity measurements.

金属有机框架 (MOF) 因其纳米孔隙度和可调性而成为节能分离（如膜和吸附过程）的最佳材料。为了调整 MOF 以实现尺寸亚埃级差异的分子的最佳分离（这是工业分离中的常见挑战），需要精确控制局部孔隙环境。在这里，我们探讨了“3维”连接体的概念，即包含空间庞大的非平面核心的连接体，作为实现对MOF孔径的亚埃控制和控制结构灵活性的手段。特别是，3 维连接体 (3DL) 的引入被证明会阻碍 MOF 中的全局呼吸转变。由于这些连接体无论其方向如何都占据一致的体积，因此它们还可以对非常相似的分子（例如己烷异构体）进行基于尺寸的精确分离。此外，我们还讨论了这些材料的一部分的热稳定性，通过变温 X 射线衍射和孔隙率测量来表征。