A Hierarchical Nanoporous Diamondoid Superstructure

Abstract

Sophisticated architectures assembled from a single class of subunits by cooperative interactions are ubiquitous in nature. The construction of their artificial mimics, however, remains one of the most formidable challenges facing synthetic chemists. Here, we report a hierarchical diamondoid superstructure—namely, a supramolecular diamond—that is constructed from the multiple-level self-assembly of a highly symmetrical salt, hexakis[(4,4′-bipyridin-1-ium)methylene]benzene hexafluorophosphate. The uniform octahedral single crystals, with 96 cationic organic fragments and 96 counteranions in a unit cell, can be prepared quantitatively in a controllable one-step procedure within seconds at ambient conditions. The sizes of the resulting samples are modulated from 280 nm to 660 μm. The mechanism of the self-assembly was elucidated at the atomic level. As proof of its intrinsically cationic superstructure with mobile anions, the three-dimensional nanoporous framework can exchange efficiently with metal oxoanions. This research shows that precisely tunable hierarchical assemblies can translate charged molecules into complicated architectures. Hierarchical self-assembly is a ubiquitous process for building sophisticated supramolecular architectures in nature. Mimicking the process and unraveling the mechanisms involved in high-precision self-assembly, however, remain a formidable challenge. Here, we present a unique strategy for constructing a hierarchical diamondoid superstructure—namely, a supramolecular diamond—that is constructed quantitatively from preorganized building blocks. The complementary interactions direct the repulsive cationic fragments to organize into a highly ordered 3D supramolecular framework. The sizes of the supramolecular diamond can be modulated from 280 nm to 660 μm. As proof of concept, the intrinsically cationic superstructure can exchange metal oxoanions with excellent efficiencies. This research shows the art and charm of hierarchical assembly and is a significant step toward a better fundamental understanding of how to produce precisely tunable assemblies. Stoddart and colleagues present a unique concept for constructing a nanoporous diamondoid superstructure—namely, a supramolecular diamond—from the hierarchical self-assembly of preorganized hexa-charged molecules. The octahedral single crystals of supramolecular diamond with controllable sizes can be prepared quantitatively within seconds under ambient conditions. This principle heralds a strategy for engineering complex supramolecular architectures from multi-charged ionic molecules, which are repulsive toward each other.