A Pillar[5]arene-Containing Metal-Organic Framework for Rapid and Highly Capable Adsorption of a Mustard Gas Simulant.

Mustard gas causes irreversible damage upon inhalation or contact with the human body. Consequently, the development of adsorbents for effective interception of mustard gas at low concentrations and high flow rates is an urgent necessity. Here we report a stable porous pillar[5]arene-containing metal-organic framework (MOF) based on zirconium (EtP5-Zr-scu), demonstrating that embedding pillar[5]arene units in MOFs can provide specific binding sites for efficient adsorption of a mustard gas simulant, 2-chloroethyl ethyl sulfide (CEES). EtP5-Zr-scu achieves a higher capacity and more rapid adsorption compared to its counterpart without embedded pillar[5]arene units (H4tcpt-Zr-scu) and perethylated pillar[5]arene (EtP5) alone. Single crystal X-ray diffraction and solid-state nuclear magnetic resonance reveal that the enhanced performance of EtP5-Zr-scu is derived from the host-guest complexation between CEES and pillar[5]arene moieties. Moreover, breakthrough experiments confirmed that the interception performance of EtP5-Zr-scu against CEES (800 ppm, 120 mL/min) was significantly improved (566 min/g) compared with H4tcpt-Zr-scu (353 min/g) and EtP5 (0.873 min/g), attributed to the integration of open channels with specific recognition sites. This work marks a significant advancement in the development of macrocycle-incorporated crystalline framework materials with recognition sites for the efficient capture of guest molecules.

Pillararene-Based Variable Stoichiometry Co-Crystallization: A Versatile Approach to Diversified Solid-State Superstructures.

Variable stoichiometry co-crystals are important in solid-state supramolecular chemistry as they allow studies of structure-property relationships while permitting the synthesis of new scaffolds using identical synthons. In this work, we extend the concept of variable stoichiometry co-crystals into the realm of pillararene chemistry and show that this permits the rational construction of a diverse set of supramolecular structures in the solid state. Specifically, we report a series of variable stoichiometry co-crystals based on pillar[n]arenes and tetracyanobenzene (TCNB) and show that the combination of in-cavity complexation by pillar[n]arenes (n = 5,6) and outside binding with TCNB allows several types of co-crystals with different self-assembled superstructures to be isolated. The variable stoichiometry co-crystals of this study display different solid-state physicochemical properties, including colors and luminescence features. Among these pillar[n]arene-based co-crystals, we discovered unique crystallographic architectures wherein two sets of individual host-guest complexes co-exist in the solid state. These mixed co-crystal systems allow for vapochromic-based detection of n-bromoalkanes. This work highlights a new strategy for the construction of self-assembled superstructures in the solid state and for tuning their intrinsic characteristics, including their luminescent and substrate-responsive features.

Vapochromic Behaviors of A Solid-State Supramolecular Polymer Based on Exo-Wall Complexation of Perethylated Pillar[5]arene with 1,2,4,5-Tetracyanobenzene.

The research for the solid-state supramolecular polymers with specific functions accelerates the development of supramolecular and materials sciences. Herein, we discover the different complexation modes of perethylated pillar[5]arene (EtP5) with 1,2,4,5-tetracyanobenzene (TCNB) in various solvents. Driven by charge-transfer interaction, TCNB is enclosed in the cavity of EtP5 in CHCl3 , while TCNB complexes with EtP5 at the exo-wall of EtP5 in CH2 Cl2 . This is because the size of CH2 Cl2 matches the cavity of EtP5, forcing TCNB to complex with the exo-wall of EtP5. Furthermore, we fabricate a vapochromic solid-state supramolecular polymer by exploiting the exo-wall complexation, which turns from brown to reddish brown or black after adsorption of alkyl aldehyde vapors. The adsorptive nature for alkyl aldehyde vapors comes from the unoccupied cavity of EtP5 based on C-H⋅⋅⋅π interactions. The vapochromic property is attributed to the change of the charge-transfer interaction caused by molecular rearrangement induced by vapor-capture in the solid-state supramolecular polymer.

Separation of Benzene and Cyclohexane by Nonporous Adaptive Crystals of a Hybrid[3]arene.

The separation of benzene and cyclohexane is one of the most challenging tasks in the petrochemical field. However, conventional separation methods suffer from cumbersome operation, huge energy expenditure, or use of entrainers. Herein, we develop an environmentally friendly and energy saving adsorptive separation strategy using nonporous adaptive crystals of a hybrid[3]arene (1). Adaptive 1 crystals separate benzene from an equimolar benzene/cyclohexane mixture with a purity of 97.5%. The selectivity comes from the stability and variability of the new crystal structure upon capture of the preferred guest, benzene. Moreover, reversible transformations between the nonporous guest-free structure and the guest-containing structure make 1 highly recyclable.

Selective Separation of Methylfuran and Dimethylfuran by Nonporous Adaptive Crystals of Pillararenes.

The separation of 2-methylfuran (MeF) and 2,5-dimethylfuran (DMeF) mixtures is very important in the chemical industry. Herein, we offer a novel strategy for the separation of MeF and DMeF using nonporous adaptive crystals (NACs) of perethylated pillar[5]arene (EtP5), perethylated pillar[6]arene (EtP6), perbromoethylated pillar[5]arene (BrP5), and perbromoethylated pillar[6]arene (BrP6). We find that the crystals of EtP6 and BrP5 show remarkable selectivities for MeF in a 50:50 (v/v) MeF:DMeF mixture vapor, yielding purities of 94.0 and 96.3%, respectively. Single-crystal structures reveal that these different selectivities come from the different thermodynamic stabilities and binding modes of the host-guest complexes. Cycling experiments demonstrate that these crystals can be reused more than five cycles without loss of performance.

Constructing Adaptive Photosensitizers via Supramolecular Modification Based on Pillararene Host-Guest Interactions.

In order to promote the development of photodynamic therapy (PDT), undesired side effects like low tumor specificity and the "always-on" phenomenon should be avoided. An effective solution is to construct an adaptive photosensitizer that can be activated to generate reactive oxygen species (ROS) in the tumor microenvironment. Herein, we design and synthesize a supramolecular switch based on a host-guest complex containing a water-soluble pillar[5]arene (WP5) and an AIEgen photosensitizer (G). The formation of the host-guest complex WP5⊃G quenches the fluorescence and inhibits ROS generation of G. Benefitting from the pH-responsiveness of WP5, the binding site between G and WP5 changes in an acidic environment through a shuttle movement. Consequently, fluorescence and ROS generation of the host-guest complex can be switched on at pH 5.0. This work offers a new paradigm for the construction of adaptive photosensitizers by using a supramolecular method.

Separation of Monochlorotoluene Isomers by Nonporous Adaptive Crystals of Perethylated Pillar[5]arene and Pillar[6]arene.

Separation of monochlorotoluene isomers is a vital process to obtain highly pure p-chlorotoluene, which is irreplaceable in the production of medicines and pesticides. However, traditional separation methods suffer from great energy consumption, cumbersome operation or use of organic desorbents. Herein, an energy-efficient and environmentally friendly method is developed through an absorptive separation strategy based on nonporous adaptive crystals of perethylated pillar[5]arene (EtP5) and pillar[6]arene (EtP6). EtP5 and EtP6 crystals separate p-chlorotoluene from a p-chlorotoluene/o-chlorotoluene equimolar mixture with purities of 99.1% and 96.1%, respectively and show no decrease in selectivity upon cycling. The selectivity is attributed to both the stability of the final crystal structure upon guest capture and suitable host cavity size/shape. Besides, we discovered the gate-opening behavior changes of EtP5 crystals at different temperatures after absorption of p-chlorotoluene/o-chlorotoluene mixtures with various p-chlorotoluene fractions, which is helpful to understand the thermodynamics of the absorption process.

[2]Pseudorotaxane-Based Supramolecular Optical Indicator for the Visual Detection of Cellular Cyanide Excretion.

Cyanide is extremely hazardous to living organisms and the environment. Owing to its wide range of applications and high toxicity, the development of functional materials for cyanide detection and sensing is highly desirable. Host-guest complexation between bis(p-phenylene)-34-crown-10 H and N-methylacridinium salt G remarkably decreases the detection limit for cyanide anions compared with that of the guest itself. The [2]pseudorotaxane selectively recognizes the cyanide anion with high optical sensitivity as a result of the nucleophilic addition of the cyanide anion at the 9-position of G. The host-guest complexation is further incorporated into supramolecular materials for the visual detection of cyanide anions, especially the detection of cellular cyanide excretion with a detection limit of 0.6 µm. This supramolecular method provides an extremely distinct strategy for the visual detection of cyanide anions.

Discovery of non-classical complex models between a cationic water-soluble pillar[6]arene and naphthalenesulfonate derivatives and their self-assembling behaviors.

Molecular recognition based on cationic water-soluble pillar[n]arenes shows considerable advantages in their application in biological and environmental systems, such as excellent anion-binding ability and antimicrobial properties. Unique complex models are discovered in this work where a cationic water-soluble pillar[6]arene binds with disodium 1,5-naphthalenedisulfonate and disodium 2,6-naphthalenedisulfonate at the ratio of 1 : 2, which is proven by results from nuclear magnetic resonance spectroscopy, isothermal titration calorimetry, fluorescence spectroscopy experiments and transmission electron microscopy.

Spatial patterns and influencing factors of financial agglomeration in Guangdong-Hong Kong-Macao Greater Bay Area.

The Guangdong-Hong Kong-Macao Greater Bay Area (GBA) represents a significant economic zone with a diverse financial landscape. Understanding the spatial distribution of financial resources within this area is crucial for promoting balanced economic growth and financial development. This study investigates the spatial patterns of financial agglomeration in the GBA, identifying key influencing factors and assessing their impact on the region's financial landscape. We employ the entropy value method to evaluate financial agglomeration levels across the GBA's cities. Additionally, we use spatial econometric techniques to analyze the spatial correlations and the Geo-Detector model to determine the primary factors influencing financial agglomeration. The analysis reveals an overall increase in financial agglomeration, with significant disparities among cities. Key factors driving this agglomeration include transportation infrastructure, overseas trade, foreign direct investment (FDI), and technological advancements. Hong Kong and Shenzhen display notable unevenness in the distribution of financial industries. The interplay between finance, technology, and industrial sectors suggests considerable development potential. Understanding and optimizing the spatial distribution of financial resources is essential for fostering high-quality financial development and sustainable economic growth in the GBA. This study provides insights that can inform policy decisions aimed at enhancing financial integration and cooperation within the region.

Separation of benzene and toluene associated with vapochromic behaviors by hybrid[4]arene-based co-crystals.

The combination of macrocyclic chemistry with co-crystal engineering has promoted the development of materials with vapochromic behaviors in supramolecular science. Herein, we develop a macrocycle co-crystal based on hybrid[4]arene and 1,2,4,5-tetracyanobenzene that is able to construct vapochromic materials. After the capture of benzene and toluene vapors, activated hybrid[4]arene-based co-crystal forms new structures, accompanied by color changes from brown to yellow. However, when hybrid[4]arene-based co-crystal captures cyclohexane and pyridine, neither structures nor colors change. Interestingly, hybrid[4]arene-based co-crystal can separate benzene from a benzene/cyclohexane equal-volume mixture and allow toluene to be removed from a toluene/ pyridine equal-volume mixture with purities reaching 100%. In addition, the process of adsorptive separation can be visually monitored. The selectivity of benzene from a benzene/cyclohexane equal-volume mixture and toluene from a toluene/ pyridine equal-volume mixture is attributed to the different changes in the charge-transfer interaction between hybrid[4]arene and 1,2,4,5-tetracyanobenzene when hybrid[4]arene-based co-crystal captures different vapors. Moreover, hybrid[4]arene-based co-crystal can be reused without losing selectivity and performance. This work constructs a vapochromic material for hydrocarbon separation.

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.

Recent Progress of Supramolecular Chemotherapy Based on Host-Guest Interactions.

Chemotherapy is widely recognized as an effective approach for treating cancer due to its ability to eliminate cancer cells using chemotherapeutic drugs. However, traditional chemotherapy suffers from various drawbacks, including limited solubility and stability of drugs, severe side effects, low bioavailability, drug resistance, and challenges in tracking treatment efficacy. These limitations greatly hinder its widespread clinical application. In contrast, supramolecular chemotherapy, which relies on host-guest interactions, presents a promising alternative by offering highly efficient and minimally toxic anticancer drug delivery. In this review, an overview of recent advancements in supramolecular chemotherapy based on host-guest interactions is provided. The significant role it plays in guiding cancer therapy is emphasized. Drawing on a wealth of cutting-edge research, herein, a timely and valuable resource for individuals interested in the field of supramolecular chemotherapy or cancer therapy, is presented. Furthermore, this review contributes to the progression of the field of supramolecular chemotherapy toward clinical application.

Cagearenes: synthesis, characterization, and application for programmed vapour release.

Here, we announce the establishment of a new family of organic molecular cages, named cagearenes, by taking advantage of a versatile strategy. These cagearenes were prepared via the Friedel-Crafts reaction by condensing two equivalents of a precursor bearing three 1,4-dimethoxybenzene groups and three equivalents of formaldehyde. Two cages, namely cagearene-1 and cagearene-2, are obtained and well characterized. The cagearene-1 solid exhibits the ability to adsorb benzene vapour from an equimolar benzene/cyclohexane mixture with a purity of 91.1%. Then, the adsorbed benzene molecules can be released from the cage at a relatively lower temperature, namely 70 °C, as a consequence of which, cyclohexane with a high purity was left within the cage solid. Heating the cage solid further at 130 °C led to the production of cyclohexane with a purity up to 98.7%. As inferred from the single crystal structures and theoretical calculations, the ability of the cage in programmed release of benzene and cyclohexane results from the different binding modes of these two guests.