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Cucurbit[n]urils are a family of molecular container hosts bearing a rigid hydrophobic cavity and two identical carbonyl fringed portals. They have attracted much attention in supramolecular chemistry because of their superior molecular recognition properties in aqueous media. This review highlights the recent advances and challenges in the field of cucurbit[n]uril-based coordination chemistry. It not only presents progress in the knowledge of such macrocyclic compounds, which range from simple to complicated architectures, but also presents new routes of synthesis and their advantages in hybrid porous solids. The concept of structure "inducer" for their structural design to achieve predictable structures and controlled pores is described. The large pore sizes and hydrophobic cavities of these compounds that lead to unprecedented properties and potential applications are also discussed.

Supramolecular architectures and materials have attracted immense attention during the last decades because they not only open the possibility of obtaining a large variety of aesthetically interesting structures but also have applications in gas storage, sensors, separation, catalysis, and so on. On the other hand, cucurbit[n]urils (Q[n]s), a relatively new class of macrocyclic hosts with a rigid hydrophobic cavity and two identical carbonyl fringed portals, have attracted much attention in supramolecular chemistry. Because of the strong charge-dipole and hydrogen bonding interactions, as well as hydrophobic and hydrophilic effect derived from the negative portals and rigid cavities of Q[n]s, nearly all research in Q[n]s has been focused on utilizing the portals and cavities to construct supramolecular assemblies similar to other macrocyclic receptors such as cyclodextrin and calixarenes. Interestingly, a recent study revealed that other weak noncovalent interactions such as hydrogen bonding and π···π stacking, as well as C-H···π and ion-dipole interactions, could also be defined as "outer-surface interactions", which are derived from the electrostatically positive outer surface of Q[n]s. These interactions could be the driving forces in the formation of various novel Q[n]-based supramolecular architectures and functional materials. In this Account, we provide a comprehensive overview of supramolecular self-assemblies based on the outer-surface interactions of Q[n]s. These outer-surface interactions include those between Q[n]s, Q[n]s and aromatic molecules, Q[n]s and calixarenes, Q[n]s and inorganic complex ions, and Q[n]s and polyoxometalates. Pioneering work has shown that such weak noncovalent interactions play very important roles in the formation of various Q[n]-based functional materials and supramolecular architectures. For example, hydrogen bonds in outer-surface interactions between Q[n] molecules not only function as the sole driving force in the formation of one-dimensional Q[n] porous channels but also assist the bonding forces of the channels in capturing and accommodating acetylene molecules and carbon dioxide in the channel cavities. Moreover, upon introduction of a third species such as an aromatic molecule or inorganic anion into the Q[n]/metal system, "outer-surface interactions" could lead to Q[n]/metal-based self-assemblies from simple finite supramolecular coordination complexes to infinite polydimensional supramolecular architectures and other structures. Overall, this Account focuses on the novel self-assembly driving force derived from Q[n]s including (i) concepts of the outer-surface interactions of Q[n]s, (ii) providing plausible explanations of the mechanisms of the outer-surface interactions of Q[n]s, and (iii) introduction of an overview of the developments and practical applications of outer-surface interactions of Q[n]s in supramolecular chemistry. It is hoped that this study based on the outer-surface interactions of Q[n]s can enrich the field of molecular engineering of functional...

Light-emitting materials with tunable properties may offer fascinating applications in optoelectronic devices, fluorescent sensors, and imaging agents. Herein, a new supramolecular approach based on host-guest interactions that greatly decreases the number of required synthetic steps and produces a system with tunable and dynamical photophysical properties was developed. Because of the novel electronic distributions of the chromophore guest within the rigid hydrophobic cavity of the cucurbit[8]uril host in this system, color tuning of emissions such as cyan, yellow, green, and white light with efficiency increased fluorescence lifetime, and quantum yield was easily achieved by simple addition of the host in aqueous solution. Stimulus-responsive tuning of color has long been an important area of research into light emissions. The current study distinguishes itself by its combination of simple steps using a single synthetic receptor and a single organic fluorophore guest in a single solution. Our results may provide a promising advancement of the fabrication of smart and tunable luminescent materials.

Porous materials, especially metal–organic frameworks, covalent organic frameworks, and supramolecular organic frameworks, are widely used in heterogeneous catalysis, adsorption, and ion exchange. Cucurbit[n]urils (Q[n]s) suitable building units for porous materials because they possess cavities with neutral electrostatic potential, portal carbonyls with negative electrostatic potential, and outer surfaces with positive electrostatic potential, which may result in the formation of Q[n]‐based supramolecular frameworks (QSFs) assembled through the interaction of guests within Q[n]s, the coordination of Q[n]s with metal ions, and outer‐surface interaction of Q[n]s (OSIQ). This review summarizes the various QSFs assembled via OSIQs. The QSFs can be classified as being assembled by 1) self‐induced OSIQ, 2) anion‐induced OSIQ, and 3) aromatic‐induced OSIQ. The design and construction of QSFs with novel structures and specific functional properties may establish a new research direction in Q[n] chemistry.