Adsorption of polyhaloalkane vapors by adaptive macrocycle crystals of WreathArene through C-halogen⋯π interactions

Fluorinated Macrocycle for Adsorptive Separation and Chromatographic Separation of Toluene and Methylcyclohexane

Achieving the adsorptive separation and chromatographic separation of industrially the important chemicals toluene and methylcyclohexane using the same material is a highly desirable goal. We have successfully accomplished this using a fluorinated macrocycle tetrafluoroterphen[3]arene (4FTP3), which was synthesized and used for gas chromatographic separation in our previous work. The macrocycle 4FTP3 permitted the adsorptive separation of toluene from a toluene/methylcyclohexane mixture (1 : 1, v/v) with a purity of 99.3 % in a single adsorption cycle. Additionally, the use of 4FTP3 as a gas chromatographic stationary phase permitted the high-resolution separation of a toluene/methylcyclohexane mixture, with a retention capacity decreasing in the order of: toluene>methylcyclohexane. Single-crystal structural analysis revealed that the C-H⋅⋅⋅F interactions between 4FTP3 and toluene resulted in an enhanced binding affinity, association enthalpy, and longer retention time for toluene. This macrocycle is of particular interest for use as a separation material due to its simultaneous adsorptive separation and gas chromatographic separation of toluene/methylcyclohexane. The present fluorinated macrocycle may therefore have roles to play in both analytical science and the chemical industry.

One-step Macrocycle-to-Macrocycle Conversion Towards Two New Macrocyclic Arenes with Different Structures and Properties

Two new macrocyclic arenes H1 and H2 were conveniently synthesized by the one-step reaction of carboxylic acid substituted octopus[3]arene. It was found that H1 was composed of three ethenoanthracene subunits with a rigid hexagonal structure and H2 contained two ethenoanthracene subunits and one anthracene subunit with a rigid house-shaped structure. Among them, H2 exhibited strong blue fluorescence due to the existence of an anthracene subunit. Moreover, both H1 and H2 showed large and electron-rich cavities, which enable them to effectively complex different nitrogen-containing heterocyclic salt guests in solution and the solid state. It was further found that H2 exhibited stronger complexation towards the tested guests than H1 probably due to the stronger charge-transfer interactions between H2 and the guests.

Fluorinated Nonporous Adaptive Cages for the Efficient Removal of Perfluorooctanoic Acid from Aqueous Source Phases

Per- and polyfluoroalkyl substances (PFAS) accumulate in water resources and pose serious environmental and health threats due to their nonbiodegradable nature and long environmental persistence times. Strategies for the efficient removal of PFAS from contaminated water are needed to address this concern. Here, we report a fluorinated nonporous adaptive crystalline cage (F-Cage 2) that exploits electrostatic interaction, hydrogen bonding, and F-F interactions to achieve the efficient removal of perfluorooctanoic acid (PFOA) from aqueous source phases. F-Cage 2 exhibits a high second-order kobs value of approximately 441,000 g mg-1 h-1 for PFOA and a maximum PFOA adsorption capacity of 45 mg g-1. F-Cage 2 can decrease PFOA concentrations from 1500 to 6 ng L-1 through three rounds of flow-through purification, conducted at a flow rate of 40 mL h-1. Elimination of PFOA from PFOA-loaded F-Cage 2 is readily achieved by rinsing with a mixture of MeOH and saturated NaCl. Heating at 80 °C under vacuum then makes F-Cage 2 ready for reuse, as demonstrated across five successive uptake and release cycles. This work thus highlights the potential utility of suitably designed nonporous adaptive crystals as platforms for PFAS remediation.

Recent advances in the synthesis and applications of macrocyclic arenes

Macrocyclic arenes including calixarenes, resorcinarenes, cyclotriveratrylene, pillararenes and so on have emerged as highly attractive synthetic macrocyclic hosts due to their unique structures, facile functionalization, and broad range of applications. In recent years, there has been growing interest in the development of novel macrocyclic arenes composed of various aromatic building blocks bridged by methylene groups, which have found applications in various research areas. Consequently, the development of novel macrocyclic arenes has become a frontier and hot topic in supramolecular and macrocyclic chemistry. In this review, we feature the recent advances in the synthesis and applications of novel macrocyclic arenes that have emerged in the last decade. The general synthetic strategies employed for these macrocyclic arenes are systematically summarized, and their wide applications in molecular recognition and assemblies, molecular machines, biomedical science and functional materials are highlighted.

Synthesis, characterization and antimicrobial property in vitro of supramolecular coordination polymers bearing brominated Schiff base ligand

In this study, two supramolecular coordination polymers of Co(II) and Zn(II) based on brominated Schiff base (E)-4-bromo-2-((quinolin-6-ylimino)methyl)phenol (HL) were synthesized and characterized by using elemental analysis, IR spectroscopy and NMR spectroscopy. Furthermore, the crystal structures of HL, CoL₂ (І) and ZnL₂ (II) were determined by single crystal X-ray analysis. It was revealed that the bromine-related interaction played important role in the self-assembly of HL supramolecular network. The crystal structural investigations revealed that І and II were isomorphous with the same geometry around the metal atom and similar structural feature. The stable four-membered chelate structure resulted from coordination between the metal(II) ion and deprotonated bidentate ligand. And supramolecular coordination polymers of І and II formed diverse architecture through multiple hydrogen bondings, π···π interactions and halogen-related interactions. Antimicrobial activities of polymers were tested toward four bacteria and five phytopathogenic fungi. І and II showed higher activities toward the tested microorganisms than HL. Furthermore, the photoluminescence results indicated that HL and II accompanied with better fluorescence properties in the ultraviolet region.

Degradation and adsorption behavior of biodegradable plastic PLA under conventional weathering conditions

With the increasing pollution of plastics and the widespread use of polylactic acid (PLA), its weathering process in the natural environment needs to be studied. Hence, we investigated the characteristics of PLA under conventional weathering conditions and the adsorption behavior between PLA and tetracycline (TC). The results showed cracks and holes in the weathered PLA surface, an increase in oxygen-containing functional groups, and a 77.94 % decrease in contact angle, causing more amount of TC to be adsorbed. The maximum adsorption capacity of PLA for TC is approximately 3.5 times higher than before weathering due to multilayer physical adsorption. Nevertheless, the surface of the microplastics weathered by seawater did not change significantly. This work elucidates the weathering mechanism of biodegradable microplastics under abiotic conditions, thus correctly assessing the difference in natural and conventional degradability of biodegradable plastics.