Generalizing Pore-Space Partitioning in Metal-Organic Frameworks

The development of a theoretical framework typically proceeds from idealized cases toward increasingly nonideal situations. Over the past decade, pore-space partitioning (PSP) has been predominantly explored in high-symmetry systems based on trimers at the highest D_3h symmetry. Extending PSP toward a more general theoretical framework would encompass a purposeful reduction of the symmetry of building blocks or crystal symmetry. However, the design of partitioning strategies is more challenging in lower-symmetry situations. Herein, we report several new types of PSP-enabled metal-organic framework (MOF) platforms featuring ligand-triggered lower building-block symmetry or interpenetration-triggered lower crystal symmetry (even if the building-block symmetry is at the maximum). This expansion of PSP is realized through a new conceptual strategy termed retro-PSP, which enables the construction of partitioning ligands with adaptable symmetry and the discovery of tripyridyl ligands with C_3h symmetry as partitioning ligands. In addition to a new form of partitioning mode for acs net (t2-pacs) via partitioning of a trigonal-bipyramidal cage (instead of previously observed partitioning of straight channels) and the hierarchical partition in 2- and 3-fold interpenetrating acs nets (x2-pacs and x3-pacs), we have also created the partitioned pcu (pcup) and partitioned nia (pnia) systems. This work results not only in the discovery of new topologies not known before, but also the experimental realization of topologies that had previously existed only as theoretical predictions. Collectively, this work establishes retro-PSP as a generalizable approach for extending PSP to include either more partition modes or more MOF platforms, resulting in new PSP-enabled materials with enhanced stability and tunable gas adsorption properties.