Bottom-Up Assembly of a Complex Superstructure from a Simple Low-Symmetry Block and Three Ni Nodes

Design and synthesis of a superstructure with a hierarchical pore system from simple building blocks are a great challenge. Herein, we report the assembly of a complex superstructure (termed NTU-81) by using a strategy of bottom-up synthesis with a simple low-symmetry building block (4-(3,5-di(1H-imidazol-1-yl)phenyl)pyridine) and Ni nodes. Single-crystal X-ray diffraction revealed that NTU-81 ([C216H173N60Ni16O54, 2ZrF6·xGuest]) has three kinds of Ni clusters (Ni, Ni2O, and Ni3O) and two kinds of ligand connections (2-c and 3-c), which therefore makes the framework possess an unprecedented structural complexity and attractive hierarchical pore system. Notably, the crystallographically nonequivalent moieties in this monoclinic system fabricate 4-c and 5-c tetrakaidecahedrons, which are then organized into a cage-contained layer with a new topology (point symbol of {4.6.8}2{6.82}). Along with a charged pore surface, coordinated water molecules, and free pyridine N sites, NTU-81 shows highly efficient I2 capture in solution. These effects give rise to not only a new material for highly efficient I2 capture but also, more attractively, a design philosophy that can be extended to the construction of complex superstructures in a one-step reaction for desired applications.