Rational Design and Reticulation of Infinite qbe Rod Secondary Building Units into Metal–Organic Frameworks through a Global Desymmetrization Approach for Inverse C₃H₈/C₃H₆ Separation

The development of reticular chemistry has enabled the construction of a large array of metal–organic frameworks (MOFs) with diverse net topologies and functions. However, dominating this class of materials are those built from discrete/finite secondary building units (SBUs), yet the designed synthesis of frameworks involving infinite rod-shaped SBUs remain underdeveloped. Here, by virtue of a global linker desymmetrization approach, we successfully targeted a novel Cu-MOF (Cu-ASY) incorporating infinite Cu-carboxylate rod SBUs with its structure determined by micro electron diffraction (MicroED) crystallography. Interestingly, the rod SBU can be simplified as a unique cylindric sphere packing qbe tubule made of [4³.6²] tiles, which further connect the tritopic linkers to give a newly discovered 3,5-connected gfc net. Cu-ASY is a permanent ultramicroporous material featuring 1D channels with highly inert surfaces and shows a preferential adsorption of propane (C₃H₈) over propene (C₃H₆). The efficiency of C₃H₈ selective Cu-ASY is validated by multicycle breakthrough experiments, giving C₃H₆ productivity of 2.2 L/kg. Density functional theory (DFT) calculations reveal that C₃H₈ molecules form multiple C−H⋅⋅⋅π and atypical C−H⋅⋅⋅ H−C van der Waals interactions with the inner nonpolar surfaces. This work therefore highlights the linker desymmetrization as an encouraging and intriguing strategy for achieving unique MOF structures and properties.