Giant Expanded Porous Metallo-Hexagons.

Molecular self-assembly is a widely recognized approach for fabricating biomimetic functional nanostructures. Here, we report the synthesis of two giant hollow coronoid-like supramolecular hexagons, H1 and H2. These hexagons feature large cavities, showcasing unique inner and outer hexagons fixed by specific connectivities for enhanced stability and high metal center density. H1 exhibits properties that can be transformed through the thermodynamic conversion of the metallopolymer formed by L1 and L2. With an edge length of 6.8 nm, H2 is one of the largest hexagons reported to date. 1D and 2D NMR, TEM, ESI-MS, and TWIM-MS experiments provided conclusive evidence for the composition and structure of the assembled hexagons. This work demonstrates the feasibility of constructing giant supramolecular architectures with precise control over their size and shape, opening up new possibilities for the design and synthesis of sophisticated supramolecules and nonbiological materials.

Segmented Template-Directed Self-Assembly of Giant Truncated Triangular Supramolecules.

The template-directed strategy has been extensively employed for the construction of supramolecular architectures. However, with the increase in the size and complexity of these structures, the synthesis difficulty of the templates escalates exponentially, thereby impeding the widespread application of this strategy. In this study, two truncated triangles T1 and T2 were successfully self-assembled through a novel segmented template strategy by segmenting the core triangular template into portions. Two metallo-organic ligands L2 and L3 were designed and synthesized by dividing the central stable triangle into three separate parts and incorporating them into the precursor ligands, which served as templates to guide the self-assembly process with ligands L1 and L4, respectively. The assembled structures were unambiguously characterized by multidimensional and multinuclear NMR (1H, COSY, NOESY), multidimensional mass spectrometry analysis (ESI-MS and TWIM-MS), and transmission electron microscopy (TEM). Moreover, we observed the formation of fiberlike nanotubes from single-molecule triangles by hierarchical self-assembly.

Adjusting the Architecture of Heptagonal Metallo-Macrocycles by Embedding Metal Nodes into the Backbone.

Coordination-driven self-assembly has been extensively employed for the bottom-up construction of discrete metallo-macrocycles. However, the prevalent use of benzene rings as the backbone limits the formation of large metallo-macrocycles with more than six edges. Herein, by embedding metal nodes into the ligand backbone, we successfully regulated the ligand arm angle and assembled two giant heptagonal metallo-macrocycles with precise control. The angle between two arms at position 4 of the central terpyridine (tpy) extended after complexation with metal ions, leading to ring expansion of the metallo-macrocycle. The assembled structures were straightforwardly identified through multi-dimensional NMR spectroscopy (1 H, COSY, NOESY), multidimensional mass spectrometry analysis (ESI-MS and TWIM-MS), transmission electron microscopy (TEM), as well as scanning tunneling microscopy (STM). In addition, the catalytic performances of metallo-macrocycles in the oxidation of thioanisole were studied, with both supramolecules exhibiting good conversion rates. Furthermore, fiber-like nanostructures were observed from single-molecule heptagons by hierarchical self-assembly.

Strain-Induced Heteromorphosis Multi-Cavity Cages: Tension-Driven Self-Expansion Strategy for Controllable Enhancement of Complexity in Supramolecular Assembly.

Coordinative supramolecular cages with adjustable cavities have found extensive applications in various fields, but the cavity modification strategies for multi-functional structures are still challenging. Here, we present a tension-driven self-expansion strategy for construction of multi-cavity cages with high structural complexity. Under the regulation of strain-induced capping ligands, unprecedented heteromorphosis triple-cavity cages S2 /S4 were obtained based on a metallo-organic ligand (MOL) scaffold. The heteromorphosis cages exhibited significant higher cavity diversity than the homomorphous double-cavity cages S1 /S3 ; all of the cages were thoroughly characterized through various analytical techniques including (1D and 2D) NMR, ESI-MS, TWIM-MS, AFM, and SAXS analyses. Furthermore, the encapsulation of porphyrin in the cavities of these multi-cavity cages were investigated. This research opens up new possibilities for the architecture of heteromorphosis supramolecular cages via precisely controlled "scaffold-capping" assembly with preorganized ligands, which could have potential applications in the development of multifunctional structures with higher complexity.

The Photothermal Conversion and UV Resistance of Silk Fabrics Being Achieved through Surface Modification with C@SiO2 Nanoparticles.

With the improvement in people's living standards, the development and application of smart textiles are receiving increasing attention. In this study, a carbon nanosurface was successfully coated with a SiO2 layer to form C@SiO2 nanomaterials, which improved the dispersion of carbon nanomaterials in an aqueous solution and enhanced the absorption of light by the carbon nanoparticles. C@SiO2 nanoparticles were coupled on the surface of silk fabric with the silane coupling agent KH570 to form C@SiO2 nanosilk fabric. The silk fabric that was subjected to such surface modification was endowed with a special photothermal function. The results obtained with scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and infrared spectroscopy (FTIR) showed that C@SiO2 nanoparticles were successfully modified on the surface of the silk fabric. In addition, under the irradiation of near-infrared light with a power of 20 W and a wavelength of 808 nm, the C@SiO2 nanosilk fabric experienced rapid warming from 23 °C to 60 °C within 30 s. After subjecting the functional fabric to hundreds of photothermal experiments and multiple washes, the photothermal efficiency remained largely unchanged and proved to be durable and stable. In addition, the thermogravimetric (TG) analysis results showed that the C@SiO2 nanoparticles contributed to the thermal stability of the silk fabric. The UV transmittance results indicated that C@SiO2 nanofabric is UV-resistant. The silk modification method developed in this study is low-cost, efficient, and environmentally friendly. It has some prospects for future applications in the textile industry.

Multi-functionalized Metallo-Supramolecular Spoked Wheels: Their Emission-Tunable Hierarchically Assembled System with Dye Molecules.

Supramolecular architectures with multiple emissive units are especially appealing due to their desired properties, such as artificial light harvesting and white-light emission. But fully achieving multi-wavelength photoluminescence in a single supramolecular architecture remains a challenge. In this paper, functionalized supramolecular architectures containing twelve metal centers and six pyrene moieties were nearly quantitatively synthesized by multi-component self-assembly and fully characterized by 1D and 2D nuclear magnetic resonance, dynamic light scattering, electrospray ionization mass spectrometry, traveling-wave ion mobility mass spectrometry, and transmission electron microscopy. Moreover, the hierarchical nano-assemblies were prepared by introducing anionic dyes to the positively charged self-assembled framework, which contained three luminescence centers, namely, pyrene, tpy-Cd coordination parts, and Sulforhodamine B anions. Such a hierarchically assembled system displayed tunable emission by taking full advantage of aggregation-induced emission enhancement, aggregation-caused quenching, and fluorescence resonance energy transfer effects and showed the diverse emission colors. This research provides a new insight for constructing multiple emissive metallo-supramolecular assemblies.

Heteroleptic/Heterometallic Sierpinski Triangle with Room Temperature Fluorescence Emission and Photocatalytic Amine Oxidation Activity.

As a result of their optical and redox properties, bipyridyl (bpy) and terpyridyl (tpy) ruthenium complexes play vital roles in numerous domains. Herein, the design and synthesis of two bipyridyl and terpyridyl ruthenium(II) building units L1 and L2 are explained. A [Ru(bpy)3]2+ functionalized triangle S1 and a Sierpinski triangle S2 were synthesized in almost quantitative yields by the self-assembly of L1 with Zn2+ ions and by the heteroleptic self-assembly of L1 and L2 with Zn2+ ions, respectively. The Sierpinski triangle S2 contains the coordination metals [Ru(bpy)3]2+, [Ru(tpy)2]2+, and [Zn(tpy)2]2+. According to research on the catalytic activity of amine oxidation on supramolecules S1 and S2, the benzylamine substrates were nearly entirely transformed to N-benzylidenebenzylamine derivatives after 1 h under a Xe lamp. Furthermore, the observed ruthenium-containing terpyridyl supramolecule S2 maintains high luminous performance at ambient temperature. This discovery opens up new possibilities for the rational molecular design of terpyridyl ruthenium fluorescent materials and catalytic functional materials.

Bi-directional geometric constraints in the construction of giant dual-rim nanorings.

In the field of metallo-supramolecular assemblies, supramolecular macrocycles have attracted considerable attention due to their guest recognition and catalytic properties. Herein, we report a novel strategy for the construction of giant hollow macrocyclic structures using a bi-directional geometric constraint strategy. We investigated the structural design of two terpyridine-based tetratopic organic ligands, whose inner and outer rims have different angles. Compared to conventional strategies of self-assembly using single angular orientation building blocks that typically generate small macrocyclic objects or polymers, the mutual interaction between the different angles of the ligands could promote the formation of giant hollow macrocyclic supramolecular architectures. The self-assembly mechanism and hierarchical self-assembly of giant supramolecular macrocycles have been characterized by NMR, ESI-MS and TEM experiments. The strategy used in this study not only advances the design of giant 2D macrocycles with large inner diameters but also gives insights into the mechanism of formation of large structures.

Crystalline Metallo-Organic Cage by Triphenylene-Cored Hexaterpyridine for Fast Iodine Capture.

In recent years, radioactive iodine capture has played an important role in nuclear waste treatment. However, most of the adsorbents possess low economic efficiency and undesirable reutilization in practical application. In this work, a terpyridine-based porous metallo-organic cage was assembled for iodine adsorption. Through synchrotron X-ray analysis, the metallo-cage was found to have a porous hierarchical packing mode with inherent cavity and packing channel. By taking advantage of polycyclic aromatic units and charged ⟨tpy-Zn2+-tpy⟩ (tpy = terpyridine) coordination sites in the structure, this nanocage exhibits an excellent ability to capture iodine in both the gas phase and aqueous medium, and the crystal state of the nanocage shows an ultrafast kinetic process of capturing I2 in aqueous solution within 5 min. The calculated maximum sorption capacities for I2 based on the Langmuir isotherm models are 1731 and 1487 mg g-1 for amorphous and crystalline nanocages, which is noticeably higher than most of the reported iodine sorbent materials in the aqueous phase. This work not only provides a rare example of iodine adsorption by a terpyridyl-based porous cage but also expands the applications of terpyridine coordination systems into iodine capture.

A 5.3 nm giant metal-organic cage and its supramolecular gel for the formation of dye molecular ionic pairs.

A terpyridine-based supramolecular cage was successfully synthesized by the self-assembly of a hexapodal metal-organic ligand with Zn2+. This metallo-cage exhibited two large parallel planes on the top and bottom with diameters close to 6 nm and a face-to-face distance close to 3.5 nm, thus possessing a large cavity. Electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance (NMR), two-dimensional nuclear Overhauser (2D-NOESY), and diffusion-ordered (DOSY) spectroscopies as well as transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements, unambiguously supported the formation of a supramolecular cage. Furthermore, the corresponding metal-organic gel was felicitously prepared in CH3CN/H2O and displayed good adsorption performance for dye molecules.

Substituents make a difference: 6,6″-modified terpyridine complexes with helix configuration and enhanced emission.

A series of complexes L22-M (L2: 6,6″-bis(4-methoxyphenyl)-4'-phenyl-2,2':6',2″-terpyridine, M: Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+) were synthesized by coordinating p-methoxyphenyl 6,6″-substituted terpyridine ligand with first-row transition metal ions and characterized by NMR, ESI-MS, and X-ray single crystal diffraction techniques. Single-crystal structures demonstrated that the steric hindrance of p-methoxyphenyl substituents endowed complexes L22-M with obvious longer coordination bond lengths and larger bond angles and dihedral angles compared with unmodified L12-M (L1: 4'-phenyl-2,2':6',2″-terpyridine). The chiral helix geometry was observed for L22-M, in which 2,2':6',2″-terpyridine moiety dramatically twisted to a spiral form in comparison to the nearly coplanar structure of the parent L12-M, resulting in plentiful intramolecular and intermolecular π-π interactions. Also, the appealing racemic (P and M) double helix packed structure for 6,6″-modified bisterpyridine complex L22-Cu was formed in the crystal. The consequent appealing charge transfer (CT) emission for L22-Zn in the solution and solid were investigated via UV-vis and fluorescence spectroscopy techniques and time-dependent density functional theory (TD-DFT) calculations. This work afforded a new method to achieve intriguing chiral geometry and CT optical properties via the subtle design and modification of terpyridine ligands.

The Marriage of Sierpinski Triangles and Platonic Polyhedra.

Fractal structures with self-similarity are of fundamental importance in the fields of aesthetic, chemistry and mathematics. Here, by taking advantage of constructs the rational geometry-directed precursor design, we report the construction of two fascinating Platonic solids, the Sierpinski tetrahedron ST-T and the Sierpinski octahedron ST-O, in which each possesses a fractal Sierpinski triangle on their independent faces. These two discrete complexes are formed in near-quantitative yield from the multi-component self-assembly of truncated Sierpinski triangular kernel L1 with tribenzotriquinacene-based hexatopic and anthracene-based tetratopic terpyridine ligands (L3 and L4 ) in the presence of metal ions, respectively. The enhanced stabilities of the 3D discrete structures were investigated by gradient tandem mass spectrometry (gMS2 ). This work provides new constructs for the imitation of complex virus assemblies and for the molecular encapsulation of giant guest molecules.

Tensile Experiments and Numerical Analysis of Textile-Reinforced Lightweight Engineered Cementitious Composites.

Despite many cases of textile-reinforced engineered cementitious composites (TR-ECCs) for repairing and strengthening concrete structures in the literature, research on lightweight engineered cementitious composites (LECC) combined with large rupture strain (LRS) textile and the effect of textile arrangement on tensile properties is still lacking. Therefore, this paper develops textile-reinforced lightweight engineered cementitious composites (TR-LECCs) with high strain characteristics through reinforcement ratio, arrangement form, and textile type. The study revealed that, by combining an LRS polypropylene (PP) textile and LECC, TR-LECCs with an ultimate strain of more than 8.0% (3-4 times that of traditional TR-ECCs) could be developed, and the PP textile's utilization rate seemed insensitive to the enhancement rate. The basalt fiber-reinforced polymer (BFRP) textile without epoxy resin coating had no noticeable reinforcement effect because of bond slip; in contrast, the BFRP grid with epoxy resin coating had an apparent improvement in bond performance with the matrix and a better reinforcement effect. The finite element method (FEM) verified that a concentrated arrangement increased the stress concentration in the TR-LECC, as well as the stress value. In contrast, a multilayer arrangement enabled uniform distribution of the stress value and revealed that the weft yarn could help the warp yarn to bear additional tensile loads.

Modular Construction of a Tessellated Octahedron, its Hierarchical Spherical Aggregate Behavior, and Electrocatalytic CO2 Reduction Activity.

Coordination-driven self-assembly has led to the formation of various aesthetical polyhedrons and compounds with advanced functions. Whereas two-dimensional supramolecules with complex and giant skeletons are plentiful, the constructions of polyhedrons are limited by using basic polygons as the panels. Herein, we report the modular synthesis of a tessellated triangle and tessellated octahedron with metal-organic modules as the panels and formed via template-driven self-assembly. These architectures have diameters on the order of 10.9 nm and molecular weights greater than 84 kDa. Interestingly, fiber and spherical-like nanostructures could be formed from the tessellated triangles and octahedrons, respectively, through hierarchical self-assembly. In addition, after hybridization with carbon nanotubes, the supramolecules exhibit electrochemical reduction activity for CO2 to CO.

Heterometallic Polyoxotitanium Clusters as Bifunctional Electrocatalysts for Overall Water Splitting.

Incorporating heterometal into titanium-oxygen clusters (TOCs) is an effective way to improve its catalytic activity. Herein, we synthesize three novel heterometallic TOCs with the formula of [Ti6Cu2O7(Dmg)2(OAc)4(iPrO)6][H2Ti6Cu2O7(Dmg)2(OAc)4(iPrO)8] ({Ti6Cu2}), [Ti8Cu2O9(Dmg)2(OAc)2(iPrO)12] ({Ti8Cu2}), and [Ti10Co2O6(Dmg)2(Pdc)4(iPrO)18Cl3] ({Ti10Co2}, DmgH2 = dimethylglyoxime; PdcH2 = pyridine-2,3-dicarboxylic acid) using dimethylglyoxime and different carboxylates as the synergistic ligands. By depositing the clusters {Ti6Cu2} and {Ti10Co2} on carbon cloth as electrodes, we investigated the electrocatalytic performance of TOCs for full water splitting for the first time. To reach a 10 mA cm-2 current density in an alkaline solution, the {Ti10Co2}@CC electrode needs an overpotential as low as 120 and 400 mV for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. In addition, full water-splitting equipment with {Ti10Co2}@CC as a cathode and an anode need only 1.67 V to deliver a current density of 10 mA cm-2. Our work confirmed the potential of noble metal-free TOCs as bifunctional cluster-based electrocatalysts for water splitting, and their activities can be tuned by doping with different metal ions.

An organic-Ru2+ cluster-initiated dendritic faced metallo-octahedron and its unpredictable photoactivity.

Herein, a novel 3D metal-organic ligand consisting of a folded Ru(II)-connected tetrameric cycle and two sets of 60° juxtaposed bisterpyridine arms was synthesized and its complexation with Zn2+ gave rise to dendritic-faced metallo-octahedron 6. Remarkably, octahedron 6 displayed unexpected photosensitization ability that could produce singlet oxygen (1O2) under white light irradiation.

Green-Engineered Cementitious Composite Production with High-Strength Synthetic Fiber and Aggregate Replacement.

Engineered cementitious composites (ECCs) are potentially useful structural reinforcement and repair materials. However, owing to their high costs and carbon emissions, they are not used extensively. To control these carbon emissions and costs, recycled fly ash cenospheres (FACs) and high-strength polyethylene (PE) fibers are used here to explore the possibility of developing green lightweight ECCs (GLECCs). A series of experiments was conducted to test the physical and mechanical properties of the developed GLECC and to evaluate the possibility of developing an GLECC. The crack width development of the GLECC was also analyzed using the digital image correlation method. The experimental results indicate the following: (1) The increase in FAC content and the decrease in PE content worsened the performance of GLECCs, but the resulting GLECCs still had significant strain-hardening properties; (2) The performance and costs of GLECCs can be balanced by adjusting the amount of FAC and PE. The maximum amount of FACs attainable is 0.45 (FAC/binder), and the required amount of PE fibers can be reduced to 1%. As a result, the cost was reduced by 40% and the carbon emission was reduced by 36%, while the compressive strength was greater than 30 MPa, the tensile strength was greater than 3.5 MPa, and the tensile strain was nearly 3%. (3) The width of the crack was positively correlated with the FAC content and negatively correlated with the fiber content. In the 0.8% strain range, the average crack width can be controlled to within 100 µm and the maximum crack width can be controlled to within 150 µm, with the performance still meeting the requirements of many applications.

Tetratopic Terpyridine Building Unit as a Precursor to Wheel-Like Metallo-Supramolecules.

In an effort to construct molecules with distinct shapes and functions, the design and synthesis of multitopic ligands are often able to play an important role. Here, we report the synthesis of a novel tetratopic organic ligand LA, which can be viewed as a bis-tenon with successive angular orientations in space. The particular ligand has been treated with different tailored metal-organic ligands to afford new members of the molecular wheel family (multi-rhomboidal-shaped wheel and bis-trapezium-shaped wheel) that show enhanced stability. Two-dimensional (2D) diffusion nuclear magnetic resonance (NMR) spectroscopy (DOSY), electrospray ionization (ESI) mass spectrometry, traveling wave ion mobility (TWIM), and gradient tandem mass spectrometry (gMS2) experiments, as well as molecular modeling, have been employed to provide structural information and differentiate the isomeric separation process. In addition, considering that LA has rotational properties, it is expected to open the door to functional supramolecules and stimuli-responsive materials.

MOF Encapsulating N-Heterocyclic Carbene-Ligated Copper Single-Atom Site Catalyst towards Efficient Methane Electrosynthesis.

The exploitation of highly efficient carbon dioxide reduction (CO2 RR) electrocatalyst for methane (CH4 ) electrosynthesis has attracted great attention for the intermittent renewable electricity storage but remains challenging. Here, N-heterocyclic carbene (NHC)-ligated copper single atom site (Cu SAS) embedded in metal-organic framework is reported (2Bn-Cu@UiO-67), which can achieve an outstanding Faradaic efficiency (FE) of 81 % for the CO2 reduction to CH4 at -1.5 V vs. RHE with a current density of 420 mA cm-2 . The CH4 FE of our catalyst remains above 70 % within a wide potential range and achieves an unprecedented turnover frequency (TOF) of 16.3 s-1 . The σ donation of NHC enriches the surface electron density of Cu SAS and promotes the preferential adsorption of CHO* intermediates. The porosity of the catalyst facilitates the diffusion of CO2 to 2Bn-Cu, significantly increasing the availability of each catalytic center.

A triple-pore tessellated square array by a metal-hexagonal ligand with reinforced tetra-connectors.

Tessellation of nine polygons into a 3 × 3 array is accomplished by the self-assembly of specifically designed hexaruthenium macrocycles containing a tetrapod ligand. Differing from the hexagon-containing bipod ligand, more connections lead to a giant discrete stable higher-order assembly. The formed tessellated square array possesses three different kinds of pores and each pore contains different metal ions, including one central tetragonum (Zn4), four corner hexagons (Ru6), and four side irregular hexagons (Ru2Zn2), which provides a promising way to fabricate multichannel architectures.