Pillararene-Based Supramolecular Polymers for Adsorption and Separation

Supramolecular polymers have attracted increasing attention in recent years due to their perfect combination of supramolecular chemistry and traditional polymer chemistry. The design and synthesis of macrocycles have driven the rapid development of supramolecular chemistry and polymer science. Pillar[n]arenes, a new generation of macrocyclic compounds possessing unique pillar-shaped structures, nano-sized cavities, multi-functionalized groups, and excellent host-guest complexation abilities, are promising candidates to construct supramolecular polymer materials with enhanced properties and functionalities. This review summarizes recent progress in the design and synthesis of pillararene-based supramolecular polymers (PSPs) and illustrates their diverse applications as adsorption and separation materials. All performances are evaluated and analyzed in terms of efficiency, selectivity, and recyclability. Typically, PSPs can be categorized into three typical types according to their topologies, including linear, cross-linked, and hybrid structures. The advances made in the area of functional supramolecular polymeric adsorbents formed by new pillararene derivatives are also described in detail. Finally, the remaining challenges and future perspectives of PSPs for separation-based materials science are discussed. This review will inspire researchers in different fields and stimulate creative designs of supramolecular polymeric materials based on pillararenes and other macrocycles for effective adsorption and separation of a variety of targets.

Applications of macrocycle-based solid-state host-guest chemistry

Macrocyclic molecules have been used in various fields owing to their guest binding properties. Macrocycle-based host-guest chemistry in solution can allow for precise control of complex formation. Although solution-phase host-guest complexes are easily prepared, their limited stability and processability prevent widespread application. Extending host-guest chemistry from solution to the solid state results in complexes that are generally more robust, enabling easier processing and broadened applications. Macrocyclic compounds in the solid state can encapsulate guests with larger affinities than their soluble counterparts. This is crucial for use in applications such as separation science and devices. In this Review, we summarize recent progress in macrocycle-based solid-state host-guest chemistry and discuss the basic physical chemistry of these complexes. Representative macrocycles and their solid-state complexes are explored, as well as potential applications. Finally, perspectives and challenges are discussed.

Pillararenes as Promising Carriers for Drug Delivery

Since their discovery in 2008 by N. Ogoshi and co-authors, pillararenes (PAs) have become popular hosts for molecular recognition and supramolecular chemistry, as well as other practical applications. The most useful property of these fascinating macrocycles is their ability to accommodate reversibly guest molecules of various kinds, including drugs or drug-like molecules, in their highly ordered rigid cavity. The last two features of pillararenes are widely used in various pillararene-based molecular devices and machines, stimuli-responsive supramolecular/host-guest systems, porous/nonporous materials, organic-inorganic hybrid systems, catalysis, and, finally, drug delivery systems. In this review, the most representative and important results on using pillararenes for drug delivery systems for the last decade are presented.

Engineering Magnetic Guanidyl-Functionalized Supramolecular Organic Framework for Efficient Enrichment of Global Phosphopeptides

Comprehensive mass spectrometry-based proteomics analysis is currently available but remains challenging, especially for post-translational modifications of phosphorylated proteins. Herein, multifunctional magnetic pillar[5]arene supramolecular organic frameworks were fabricated and immobilized with arginine (mP5SOF-Arg) for highly effective enrichment of global phosphopeptides. The specific phosphate-P5/phosphate-guanidine affinities and large surface area with regular porosity contribute to the high enrichment capacity. By coupling with mass spectrometry, high detection sensitivity (0.1 fmol), excellent selectivity (1:5000 molar ratios of β-casein/cytochrome c), and high recyclability (seven cycles) were achieved for phosphopeptide analysis. mP5SOF-Arg can efficiently enrich phosphopeptides from practical samples, including defatted milk, egg yolk, and human saliva. Notably, a total of 450 phosphopeptides were explored for highly selective identification from A594 cells and 1445 phosphopeptides were identified from mouse liver tissue samples. mP5SOF-Arg exhibited great potential to serve as the basis for peptidomic research to identify phosphopeptides and provided insight for biomarker discovery.

Monodisperse pillar[5]arene-based polymeric sub-microsphere for on-line extraction coupling with high-performance liquid chromatography to determine antioxidants in the migration of food contact materials

The monodisperse pillar[5]arene-based polymeric sub-microsphere was prepared by polycondensation of hydroxylated pillar[5]arene and cyanuric chloride through a one-pot reaction in mild condition. The preparation was realized by a simple two-step temperature-programmed process without heating operation. The obtained polymeric sub-microsphere exhibited monodisperse and regular spherical structure with uniform particle size distribution of 220-320 nm accounting for 94%. The prominent adsorption capacity of the polymeric sub-microsphere for antioxidants was demonstrated and attributed to the synergistic effect of the cladding interaction with the π-electron rich cavity and hydrophilic interaction with terminal hydroxyl on pillar[5]arene. Then the pillar[5]arene sub-microsphere was packed into a micro-column to realize effective on-line enrichment of antioxidants coupling with high-performance liquid chromatography (HPLC). The flow rate of extraction and desorption solvent, clean-up and desorption volume were assessed to optimize the method. The method showed wide linear ranges with R² greater than 0.9926, low limits of detection (0.030-0.20 μg/L) and limits of quantification (0.10-0.67 μg/L). The developed method was successfully applied to determine trace antioxidants in the migration of food contact materials with simulated solution, which demonstrated the promising potential of this method for practical analysis. Furthermore, the migration behavior of antioxidants from food packaging materials into different food matrix was also investigated.

Supramolecular-Macrocycle-Based Crystalline Organic Materials

Supramolecular macrocycles are well known as guest receptors in supramolecular chemistry, especially host-guest chemistry. In addition to their wide applications in host-guest chemistry and related areas, macrocycles have also been employed to construct crystalline organic materials (COMs) owing to their particular structures that combine both rigidity and adaptivity. There are two main types of supramolecular-macrocycle-based COMs: those constructed from macrocycles themselves and those prepared from macrocycles with other organic linkers. This review summarizes recent developments in supramolecular-macrocycle-based COMs, which are categorized by various types of macrocycles, including cyclodextrins, calixarenes, resorcinarenes, pyrogalloarenes, cucurbiturils, pillararenes, and others. Effort is made to focus on the structures of supramolecular-macrocycle-based COMs and their structure-function relationships. In addition, the application of supramolecular-macrocycle-based COMs in gas storage or separation, molecular separation, solid-state electrolytes, proton conduction, iodine capture, water or environmental treatment, etc., are also presented. Finally, perspectives and future challenges in the field of supramolecular-macrocycle-based COMs are discussed.

A supramolecular hybrid material constructed from pillar[6]arene-based host-guest complexation and ZIF-8 for targeted drug delivery

A novel supramolecular hybrid material ZIF-8@DOX@WP6@G constructed from the host-guest complexation between carboxylated pillar[6]arene (WP6) and a galactose derivative (G), and doxorubicin (DOX)-loaded ZIF-8 has been synthesized for targeted drug delivery. The results showed that ZIF-8@DOX@WP6@G not only maintained the pH-sensitive drug release properties of ZIF-8 but also exhibited excellent water dispersibility and selective toxicity for hepatoma cancer cells due to the assembly of WP6 and G. The strategy used in this study opens up a new avenue for constructing multifunctional supramolecular hybrid materials for therapeutic applications in cancer treatment.