Characterization and visible light photocatalytic activity of cucurbit[n]urils/CdS-MoS2

In order to reduce the impact of CdS photogenerated electron-hole recombination on its photocatalytic performance, a narrow band gap semiconductor MoS2 and organic macromolecular cucurbit[ n]urils (Q[ n]) were used to modify CdS. Q[ n]/CdS-MoS2 ( n=6, 7, 8) composite photocatalysts were synthesized by hydrothermal method. Infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, ultraviolet-visible and photoluminescence spectrum were used to characterize the structure, morphology and optical properties of the products, and the catalytic degradation of the solutions of methylene blue, rhodamine B and crystal violet by Q[ n]/CdS-MoS2 composite catalyst was investigated. The results showed that the Q[ n] played a regulatory role on the growth and crystallization of CdS-MoS2 particles, Q[ n]/CdS-MoS2 ( n=6, 7, 8) formed flower clusters with petal-like leaves, the flower clusters of petal-like leaves increased the surface area and active sites of the catalyst, the Q[ n]/CdS-MoS2 barrier width decreased, the electron-hole pair separation efficiency was improved in the Q[6]/Cds-MoS2. Q[ n] makes the electron-hole pair to obtain better separation and migration. The Q[6]/CdS-MoS2 and Q[7]/CdS-MoS2 have good photocatalytic activity for methylene blue, and the catalytic process is based on hydroxyl radical principle.

Cucurbit[n]uril-Based Supramolecular Frameworks Assembled through Outer-Surface Interactions

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.

Synthesis, Adsorption, and Recognition Properties of a Solid Symmetric Tetramethylcucurbit[6]uril-Based Porous Supramolecular Framework

In this work, we reported a porous supramolecular framework (A) constructed of a symmetric tetramethylcucurbit[6]uril (TMeQ[6]) in aqueous HCl solutions; the driving force was the outer surface interaction of cucurbit[n]urils, as well as hydrogen bonding between latticed water molecules and portal carbonyl oxygens of TMeQ[6]. Adsorption experimental results revealed that the porous supramolecular framework can absorb certain fluorophore guests (FGs) to form luminescent assemblies (FG@As) by fluorescence enhancement or colour change, and some of them can respond to certain volatile organic compounds. Thus, the TMeQ[6]-based supramolecular framework could be used as a sensor for certain gas or volatile compounds.

4-Sulfocalix[4]arene/Cucurbit[7]uril-Based Supramolecular Assemblies through the Outer Surface Interactions of Cucurbit[n]uril

Upon mixing of aqueous solutions of the freely soluble building blocks cucurbit[7]uril (Q[7]) and 4-sulfocalix[4]arene (SC[4]A), white microcrystals instantly separate in near-quantitative yield. The driving force for this assembly is suggested to be the outer-surface interaction of the Q[n]. Dynamic light scattering, scanning electron microscopy, and NMR (diffusion-ordered NMR spectroscopy) analyses have confirmed the supramolecular aggregation of Q[7] and SC[4]A. Titration ¹H NMR spectroscopy and isothermal titration calorimetry have shown that the interaction ratio of Q[7] and SC[4]A is close to 3:1. Moreover, the Q[7]/SC[4]A-based supramolecular assembly can accommodate molecules of some volatile compounds or luminescent dyes. Thus, this work offers a simple and highly efficient means of preparing adsorbent or solid fluorescent materials.

Highly selective absorption of polychloromethanes in perhydroxylated cucurbit[6]uril-based supramolecular assemblies

Two perhydroxylated cucurbit[6]uril-based porous assemblies have been obtained by the crystallization of perhydroxylated cucurbit[6]uril {(HO)₁₂Q[6]} from aqueous HCl solutions of different concentrations, which exhibit highly selective absorption of polychloromethanes.

Multiple Efficient Fluorescence Emission from Cucurbit[10]uril-[Cd4Cl16]8--Based Pillared Diamond Porous Supramolecular Frameworks

Cucurbit[10]uril (Q[10] or CB[10]), with the largest rigid cavity (ca. 1.0 nm) yet characterized in the cucurbiturils family, and indeed among all artificial macrocyclic receptors to date, has been successfully exploited to construct a novel Q[10]-[Cd₄Cl₁₆]^8--based pillared diamond porous supramolecular framework. Single-crystal X-ray diffraction analysis revealed that the three-dimensional open-nanotube-type porous framework is constructed from free Q[10] molecules and [Cd₄Cl₁₆]^8- cluster anions through the outer surface interactions of Q[10]. Notably, the Q[10]-based porous framework host can accommodate guest dyes, such as rhodamine B (G1), pyrenemethanamine hydrochloride (G2), and bathocuproine hydrochloride (G3), to form solid materials with efficient red-green-blue (RGB) fluorescence. This work not only exemplifies a facile approach for the construction of macrocycle-based porous frameworks but also offers a simple, lower cost, yet still highly efficient means of preparing multi-emitting, including white-light-emitting, solid luminescent materials.

Celebrating Professor Len Lindoy’s 80th Birthday

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