Multicomponent, Multicavity Metallacages That Contain Different Binding Sites for Allosteric Recognition.

The encapsulation of different guest molecules by their different recognition domains of proteins leads to selective binding, catalysis, and transportation. Synthetic hosts capable of selectively binding different guests in their different cavities to mimic the function of proteins are highly desirable but challenging. Here, we report three ladder-shaped, triple-cavity metallacages prepared by multicomponent coordination-driven self-assembly. Interestingly, the porphyrin-based metallacage is capable of heteroleptic encapsulation of fullerenes (C60 or C70) and coronene using its different cavities, allowing distinct allosteric recognition of coronene upon the addition of C60 or C70. Owing to the different binding affinities of the cavities, the metallacage hosts one C60 molecule in the central cavity and two coronene units in the side cavities, while encapsulating two C70 molecules in the side cavities and one coronene molecule in the central cavity. The rational design of multicavity assemblies that enable heteroleptic encapsulation and allosteric recognition will guide the further design of advanced supramolecular constructs with tunable recognition properties.

Metal-Organic Frameworks (MOFs) and Metal-Organic Cages (MOCs) for Photocatalytic Hydrogen Production.

Metal-organic frameworks (MOFs) and metal-organic cages (MOCs) have garnered significant attention as promising photocatalysts due to their tunable chemical structures and integrated multifunctionality. To increase the photocatalytic efficiency, strategies like ligand functionalization, introducing additional catalytic sites, and doping or encapsulating photosensitizers have been explored for both MOFs and MOCs. This concept review focuses on recent advancements in utilizing MOFs and MOCs for photocatalytic hydrogen production, highlighting their unique characteristics and introducing their respective mechanisms in this field. Moreover, it outlines the current challenges and prospects faced by MOFs and MOCs, offering an outlook on their future in this domain.

Hexaphenyltriphenylene-Based Multicomponent Metallacages: Host-Guest Complexation for White-Light Emission.

A hexaphenyltriphenylene-based hexatopic pyridyl ligand is designed and used to prepare three hexagonal prismatic metallacages via metal-coordination-driven self-assembly. Owing to the planar conjugated structures of the hexaphenyltriphenylene skeleton, such metallacages show good host-guest complexation with a series of emissive dyes, which have been further used to tune their emission in solution. Interestingly, based on their complementary emission colors, white light emission is achieved in a mixture of the host metallacages and the guests.

Isoreticular Preparation of Tetraphenylethylene-based Multicomponent Metallacages towards Light-Driven Hydrogen Production.

Multicomponent metallacages can integrate the functions of their different building blocks to achieve synergetic effects for advanced applications. Herein, based on metal-coordination-driven self-assembly, we report the preparation of a series of isoreticular tetraphenylethylene-based metallacages, which are well characterized by multinuclear NMR, ESI-TOF-MS and single-crystal X-ray diffraction techniques. The suitable integration of photosensitizing tetraphenylethylene units as faces and Re catalytic complexes as the pillars into a single metallacage offers a high photocatalytic hydrogen production rate of 1707 µmol g-1 h-1 , which is one of the highest values among reported metallacages. Femtosecond transient absorption and DFT calculations reveal that the metallacage can serve as a platform for the precise and organized arrangement of the two building blocks, enabling efficient and directional electron transfer for highly efficient photocatalytic performance. This study provides a general strategy to integrate multifunctional ligands into a certain metallacage to improve the efficiency of photocatalytic hydrogen production, which will guide the future design of metallacages towards photocatalysis.

Emissive Metallacage-Cored Polyurethanes with Self-Healing and Shape Memory Properties.

The structures of the crosslinks in supramolecular polymer networks play an important role on their properties and functions. Herein, emissive metallacages are used as crosslinks to prepare metallacage-cored polyurethanes. The mechanical properties including storage modulus, toughness, Young's modulus and breaking strength of polymers are greatly enhanced with the increase of crosslinking densities. Moreover, such polymers not only exhibit good fluorescence in the solid state, but also show self-healing and shape memory properties owing to the dynamic reversible non-covalent bonds in their structures. This study not only offers a convenient strategy to prepare metallacage-crosslinked networks, but also explores their applications as self-healing and shape memory materials, which will promote the study of metallacage-cored supramolecular networks as smart materials.

Hexaphenylbenzene-Based Deep Blue-Emissive Metallacages as Donors for Light-Harvesting Systems.

We herein report the preparation of a series of hexaphenylbenzene (HPB)-based deep blue-emissive metallacages via multicomponent coordination-driven self-assembly. These metallacages feature prismatic structures with HPB derivatives as the faces and tetracarboxylic ligands as the pillars, as evidenced by NMR, mass spectrometry and X-ray diffraction analysis. Light-harvesting systems were further constructed by employing the metallacages as the donor and a naphthalimide derivative (NAP) as the acceptor, owing to their good spectral overlap. The judiciously chosen metallacage serves as the antenna, providing the suitable energy to excite the non-emissive NAP, and thus resulting in bright emission for NAP in the solid state. This study provides a type of HPB-based multicomponent emissive metallacage and explores their applications as energy donors to light up non-emissive fluorophores in the solid state, which will advance the development of emissive metallacages as useful luminescent materials.

Tetraphenylethylene-Based Multicomponent Emissive Metallacages as Solid-State Fluorescent Materials.

The construction of solid-state fluorescent materials with high quantum yield and good processability is of vital importance in the preparation of organic light-emitting devices. Herein, a series of tetraphenylethylene (TPE)-based multicomponent emissive metallacages are prepared by the coordination-driven self-assembly of tetra-(4-pyridylphenyl)ethylene, cis-Pt(PEt3 )2 (OTf)2 and tetracarboxylic ligands. These metallacages exhibit good emission both in solution and in the solid state because the coordination bonds and aggregation restrict the molecular motions of TPE synergistically, which suppresses the non-radiative decay of these metallacages. Impressively, one of the metallacages achieves very high fluorescence quantum yield (ΦF =88.46 %) in the solid state, which is further used as the coatings of a blue LED bulb to achieve white-light emission. The study not only provides a general method to the preparation of TPE-based metallacages but also explores their applications as solid-state fluorescent materials, which will promote the future design and applications of metallacages as useful emissive devices.

Visible light photocatalytic degradation of oxytetracycline hydrochloride using chitosan-loaded Z-scheme heterostructured material BiOCOOH/O-gC3N4.

In this work, a Z-scheme heterostructured BiOCOOH/O-gC3N4 material was synthesized and immobilized on chitosan (CTS) to obtain the BiOCOOH/O-gC3N4/CTS photocatalytic material for photocatalytic degradation of oxytetracycline hydrochloride (CTC).Our findings indicate that the composite material BiOCOOH/O-gC3N4, as well as the BiOCOOH/O-gC3N4/CTS composite membrane, displayed a significantly higher efficiency in photocatalytic degradation of CTC compared to BiOCOOH alone, owing to the synergistic effect of adsorption and photocatalysis. Following four cycles of use, the composite material retained around 96 % of its initial photocatalytic degradation activity. The addition of CTS in the photocatalytic material resolved issues such as aggregation and difficult recovery commonly encountered with powder materials, thereby facilitating effective collision between the photocatalytic active sites and CTC. Experimental and theoretical calculations provided confirmation that the combination of BiOCOOH and O-gC3N4 effectively enhanced the light absorption capacity and photocatalytic performance. Furthermore, we investigated the influence of environmental factors such as pH value and anions on the photocatalytic degradation experiment, which offers valuable insights for the application of composite catalysts in wastewater treatment.

Fusion of two homoleptic truncated tetrahedra into a heteroleptic truncated octahedron.

The exploration of novel structures and structural transformation of supramolecular assemblies is of vital importance for their functions and applications. Herein, based on coordination-driven self-assembly, we prepare a neutral truncated tetrahedron and a heteroleptic truncated octahedron, whose structures are unambiguously confirmed by X-ray diffraction analysis. More importantly, the truncated tetrahedron is quantitatively transformed into the truncated octahedron through its fusion with another cationic truncated tetrahedron, as evidenced by fluorescence, mass and NMR spectroscopy. This study not only deepens our understanding of the process of supramolecular fusion but also opens up possibilities for the subsequent preparation of advanced supramolecular assemblies with complex structures and integrated functions.

Porphyrin-Based Multicomponent Metallacage: Host-Guest Complexation toward Photooxidation-Triggered Reversible Encapsulation and Release.

The development of supramolecular hosts with effective host-guest properties is crucial for their applications. Herein, we report the preparation of a porphyrin-based metallacage, which serves as a host for a series of polycyclic aromatic hydrocarbons (PAHs). The association constant between the metallacage and coronene reaches 2.37 × 107 M-1 in acetonitrile/chloroform (ν/ν = 9/1), which is among the highest values in metallacage-based host-guest complexes. Moreover, the metallacage exhibits good singlet oxygen generation capacity, which can be further used to oxidize encapsulated anthracene derivatives into anthracene endoperoxides, leading to the release of guests. By employing 10-phenyl-9-(2-phenylethynyl)anthracene whose endoperoxide can be converted back by heating as the guest, a reversible controlled release system is constructed. This study not only gives a type of porphyrin-based metallacage that shows desired host-guest interactions with PAHs but also offers a photooxidation-responsive host-guest recognition motif, which will guide future design and applications of metallacages for stimuli-responsive materials.

Selective adsorption of Ag (â ) from aqueous solutions using Chitosan/polydopamine@C@magnetic fly ash adsorbent beads.

A Chitosan/polydopamine@C@magnetic fly ash (CPCMFA) adsorbent bead was prepared for adsorption of Ag (Ⅰ) in aqueous solutions and exhibited good selectivity for Ag (Ⅰ) ion. To investigate its adsorption behaviors, equilibrium, kinetic and selective studies were conducted through batch experiments. Additionally, the influence of the pH value was also evaluated. In addition, the nature, composition, morphology, and magnetic property of the prepared adsorbent beads were characterized by Fourier transform-infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis, thermogravimetric-differential scanning calorimetry (TG-DSC) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating-sample magnetometry (VSM). The freeze-dry form of CPCMFA also exhibited high adsorption capacity and selectivity for Ag (Ⅰ), with a maximum adsorption capacity of 57.02 mg/g at pH 4 and 30 °C. The experimental data were well described by the Langmuir isotherm and elovich kinetic models. The thermodynamics parameters, ΔH = 10.653 kJ/mol, ΔS = 96.63 J/mol K and ΔG < 0, demonstrate that the adsorption of Ag (Ⅰ) on the freeze-dry form adsorbent is spontaneous and endothermic. Moreover, regeneration studies showed the high recyclability of the adsorbent, which after five cycles of use it was still able to adsorb 95.7% of the amount adsorbed by the fresh adsorbent.

Recycling of Cr (VI) from weak alkaline aqueous media using a chitosan/ triethanolamine/Cu (II) composite adsorbent.

A Chitosan/triethanolamine/Cu (Ⅱ) (CTS/TEA/Cu (Ⅱ)) composite adsorbent was prepared and applied to recycle Cr (Ⅵ) from aqueous media in alkaline conditions. To investigate the adsorption behavior, the influence of pH was evaluated via batch experiments, and the prepared adsorbent was characterized by FT-IR, SEM, XRD, and Zeta potential. This adsorbent exhibited high adsorption capacity for Cr (Ⅵ) in a wide pH range (especially above 7), suggesting a possible way to separate Cr (Ⅵ) from other metal cations by adjusting the pH value prior to adsorption. Adsorption kinetic and thermodynamic experiments were conducted to explore the adsorption mechanism. Regeneration studies showed that the adsorbent can be reused for five adsorption-desorption cycles without substantial loss of adsorption capacity. Overall, the CTS/TEA/Cu (Ⅱ) adsorbent exhibits high potential for recyclingCr (Ⅵ) from wastewater.