Assembly Of Metal Ions Research Articles

Recent advances and challenges of metal–organic framework/graphene-based composites

Metal–organic frameworks (MOFs) are a new kind of porous crystalline material synthesized by the assembly of metal ions and organic ligands, which have the advantages of a large specific surface area, high porosity, and tunable pore structures and morphological features. Owing to their ease of design as well as uniform and fine-tunable pore structures, MOFs are widely employed in several applications, such as in catalysts, supercapacitors , adsorbents, sensors, environmental protection, and drug delivery. However, the poor stability and electrical conductivity of traditional MOFs limit their applications. Using graphene-based materials with rich functional groups as templates for the growth of MOF particles can not only alleviate the poor conductivity and structural instability of MOFs, but also avoid the aggregation and restacking phenomenon between graphene sheets , thereby greatly expanding the application scope of MOFs. Due to the tunable structure and composition of derivatives, MOF-derived/graphene materials can also be used as multifunctional precursors, especially in the field of electrochemistry. The latest synthesis methods of MOF/graphene composites and their derivatives, as well as their diverse applications, are reviewed in this paper. In addition, the future development opportunities and challenges corresponding to MOF/graphene composites are discussed. The preparation of MOF/graphene-based composites and their applications in batteries, supercapacitors, electrocatalysts, water purification, gas separation and storage, chemical sensors and other fields. • Improving the electrical conductivity of MOFs. • To solve the aggregation and restacking phenomena of graphene. • Synergistic effect of MOFs and graphene. • Various morphologies of MOF/graphene composites. • Analyzing the advantages of MOF/graphene composites for various applications.

A General Strategy toward Metal Sulfide Nanoparticles Confined in a Sulfur-Doped Ti3 C2 Tx MXene 3D Porous Aerogel for Efficient Ambient N2 Electroreduction.

Three-dimensional (3D) porous MXene-based aerogel architectures have attracted great interest for many applications, despite limits in renewable energy conversion owing to the lack of multifunctionality in their components. Herein, a simple and general strategy for constructing a novel functional 3D MXene-based composite heterojunction aerogel (MS@S-MAs) is presented via divalent metal-ion assembly and subsequent thermal sulfidation, and its application in electrochemical nitrogen reduction reaction (NRR) is studied. The as-prepared MS@S-MAs comprises metal sulfide nanoparticles uniformly confined in 3D interconnected conductive S-doped MXene sheets with intimate interfacial interaction. Benefiting from the unique properties and an interfacial interaction, MS@S-MAs exhibit significantly improved NRR catalytic performance and excellent stability because of the higher exposure of electrochemically active sites coupled with easier accessibility, faster mass diffusion, and quicker carrier transport at the interface. Remarkably, CoS@S-MAs show an NH3 yield rate and a Faradaic efficiency of 12.4 µg h-1 mg-1 cat and 27.05% at the lower potential of -0.15V versus a reversible hydrogen electrode in 0.1 m Na2 SO4 solution under ambient conditions, which rivals or exceeds most of the previously reported MXene-based and Co-based catalysts. This work will open avenues to construct 3D MXene-based materials with rich functionalities for energy storage and conversion, catalysis, and other applications.

Formation of Defect-Dicubane-Type NiII 2LnIII 2 (Ln = Tb, Er) Clusters: Crystal Structures and Modeling of the Magnetic Properties.

In the field of molecular nanoclusters, cubane and defect-dicubane, or butterfly structures, are typical examples of tetranuclear metal core architectures. In this work, a halogenated and anionic Schiff-base ligand (L2–) is utilized as it is predisposed to chelate within a cluster core to both 3d and 4f metal ions, in different binding configurations (H2L = 4-chloro-2-(2-hydroxy-3-methoxybenzyliden amino)phenol). The phenolate oxygen atoms of the deprotonated ligand can act in μ-O and μ3-O bridging binding modes for the intramolecular assembly of metal ions. Based on that, two tetranuclear and isostructural compounds [Ni2Tb2(L)4(NO3)2(DMF)2]·2CH3CN (1) and [Ni2Er2(L)4(NO3)2(DMF)2]·0.5CH3CN (2) were synthesized and structurally characterized. Magnetic susceptibility and magnetization data indicate the occurrence of dominant intramolecular ferromagnetic interactions between the spin centers. Particular emphasis is given to the theoretical description of the magnetic behavior, taking into account the Ln–Ni and Ni–Ni coupling paths and the magnetic anisotropy of the LnIII and NiII ions. The study is distinguished for its discussion of two distinct models, whereby model A relies on the uniaxial B20 Stevens term describing the lanthanide anisotropy and model B is based on point-charge model calculations. Importantly, the physical meaning of the obtained parameters for both models was critically scrutinized.

Substituent effects of two isophthalate derivatives on the construction of cadmium coordination polymers incorporating a dipyridyl ligand.

In recent years, the design and construction of crystalline coordination complexes by the assembly of metal ions with multitopic ligands have attracted considerable attention because of the unique architectures and potential applications of these compounds. Two new coordination polymers, namely poly[[μ-trans-1-(2-aminopyridin-3-yl)-2-(pyridin-4-yl)ethene-κ2N:N'](μ3-5-methylisophthalato-κ4O1,O1':O3:O3')cadmium(II)], [Cd(C9H6O4)(C12H11N3)]n or [Cd(5-Me-ip)(2-NH2-3,4-bpe)]n, (I), and poly[[μ-trans-1-(2-aminopyridin-3-yl)-2-(pyridin-4-yl)ethene-κ2N:N'](μ2-5-hydroxyisophthalato-κ4O1,O1':O3:O5)cadmium(II)], [Cd(C8H4O5)(C12H11N3)]n or [Cd(5-HO-ip)(2-NH2-3,4-bpe)]n, (II), have been prepared hydrothermally by the self-assembly of Cd(NO3)2·4H2O and trans-1-(2-aminopyridin-3-yl)-2-(pyridin-4-yl)ethene (2-NH2-3,4-bpe) with two similar dicarboxylic acids, i.e. 5-methylisophthalic acid (5-Me-H2ip) and 5-hydroxyisophthalic acid (5-HO-H2ip). The coordination network of (I) is a two-dimensional sql net parallel to (101). Adjacent sql nets are further linked to form a three-dimensional supramolecular framework via hydrogen-bonding interactions. Compound (II) is a two-dimensional (3,5)-connected coordination network parallel to (010) with the point symbol (63)(55647). As the other reactants and reaction conditions are the same, the structural differences between (I) and (II) are undoubtedly determined by the different substituent groups in the 5-position of isophthalic acid. Both (I) and (II) exhibit good thermal stabilities and photoluminescence properties.

Polycationic-Shelled Capsular and Tubular Nanostructures and Their Anionic-Guest Binding Properties.

For the development of novel nanospace with unique electrostatic character, we prepared new capsular and tubular nanostructures by the quantitative assembly of metal ions and bent bisacridinium ligands. The capsule and tube have closed spherical and open cylindrical cavities, respectively, with diameters of around 1 nm surrounded by cationic polyaromatic panels. Thanks to the facile synthetic protocol (three steps), another polycationic capsule with an elliptical nanocavity was also prepared by using an elongated ligand. In spite of the absence of pendant hydrophilic groups, the spherical polyaromatic capsule shows sufficient water solubility due to the polycationic shell. Moreover, the highly cationic cavity (12+) can selectively encapsulate anionic organic compounds in water.

Hydrothermal Synthesis of Metal–Polyphenol Coordination Crystals and Their Derived Metal/N‐doped Carbon Composites for Oxygen Electrocatalysis

AbstractCobalt (or iron)–polyphenol coordination polymers with crystalline frameworks are synthesized for the first time. The crystalline framework is formed by the assembly of metal ions and polyphenol followed by oxidative self‐polymerization of the organic ligands (polyphenol) during hydrothermal treatment in alkaline condition. As a result, such coordination crystals are even partly stable in strong acid (such as 2 m HCl). The metal (Co or Fe)‐natural abundant polyphenol (tannin) coordination crystals are a renewable source for the fabrication of metal/carbon composites as a nonprecious‐metal catalyst, which show high catalytic performance for both oxygen reduction reaction and oxygen evolution reaction. Such excellent performance makes metal–polyphenol coordination crystals an efficient precursor to fabricate low‐cost catalysts for the large‐scale application of fuel cells and metal–air batteries.

Hydrothermal Synthesis of Metal-Polyphenol Coordination Crystals and Their Derived Metal/N-doped Carbon Composites for Oxygen Electrocatalysis.

Cobalt (or iron)-polyphenol coordination polymers with crystalline frameworks are synthesized for the first time. The crystalline framework is formed by the assembly of metal ions and polyphenol followed by oxidative self-polymerization of the organic ligands (polyphenol) during hydrothermal treatment in alkaline condition. As a result, such coordination crystals are even partly stable in strong acid (such as 2 m HCl). The metal (Co or Fe)-natural abundant polyphenol (tannin) coordination crystals are a renewable source for the fabrication of metal/carbon composites as a nonprecious-metal catalyst, which show high catalytic performance for both oxygen reduction reaction and oxygen evolution reaction. Such excellent performance makes metal-polyphenol coordination crystals an efficient precursor to fabricate low-cost catalysts for the large-scale application of fuel cells and metal-air batteries.

Selective Thermal Elongation of Metal–Metal Distances in the Two-Dimensional Assembly of Ag(I) Ions Templated by Assembled Peptide Ligands

To develop a tunable assembly of metal ions, we demonstrated a two-dimensional Ag(I) array in the crystalline state by using an assembly of dipeptide ligands as a template. The two-dimensional assembly of Ag(I) ions was obtained through the assembly of a Ag(I)-peptide polymer complex, which was held together by hydrogen bonding interactions. At –180 °C, one-dimensional zigzag chains of Ag(I) ions were formed in each layer, which further assembled to form two-dimensional layers. The arrangement of the Ag(I) ions included several Ag–Ag distances that are supported differently by the peptide assembly. Because of this difference, when heated from –180 to 50 °C, the Ag(I) layer displays anisotropic thermal expansion in the arrangements, in which one of the Ag–Ag distances selectively elongated. This expansion is reversible, allowing switching between the zigzag chain assembly and the Ag(I) dimer assembly. Moreover, the resulting crystalline Ag(I) complexes show luminescence at both room temperature and at –196 °C, suggesting the existence of Ag–Ag interactions.

Structuring of metal-organic frameworks at the mesoscopic/macroscopic scale.

The assembly of metal ions with organic ligands through the formation of coordination bonds gives crystalline framework materials, known as metal-organic frameworks (MOFs), which recently emerged as a new class of porous materials. Besides the structural designability of MOFs at the molecular length scale, the researchers in this field very recently made important advances in creating more complex architectures at the mesoscopic/macroscopic scale, in which MOF nanocrystals are used as building units to construct higher-order superstructures. The structuring of MOFs in such a hierarchical order certainly opens a new opportunity to improve the material performance via design of the physical form rather than altering the chemical component. This review highlights these superstructures and their applications by categorizing them into four dimensionalities, zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) superstructures. Because the key issue for structuring of MOFs is to spatially control the nucleation process in desired locations, this review conceptually categorizes the available synthetic methodologies from the viewpoint of the reaction system.

Low-Molecular-Mass Penicillin Binding Protein 6b (DacD) Is Required for Efficient GOB-18 Metallo-β-Lactamase Biogenesis in Salmonella enterica and Escherichia coli

Metallo-β-lactamases (MBLs) are Zn(2+)-containing secretory enzymes of clinical relevance, whose final folding and metal ion assembly steps in Gram-negative bacteria occur after secretion of the apo form to the periplasmic space. In the search of periplasmic factors assisting MBL biogenesis, we found that dacD null (ΔdacD) mutants of Salmonella enterica and Escherichia coli expressing the pre-GOB-18 MBL gene from plasmids showed significantly reduced resistance to cefotaxime and concomitant lower accumulation of GOB-18 in the periplasm. This reduced accumulation of GOB-18 resulted from increased accessibility to proteolytic attack in the periplasm, suggesting that the lack of DacD negatively affects the stability of secreted apo MBL forms. Moreover, ΔdacD mutants of S. enterica and E. coli showed an altered ability to develop biofilm growth. DacD is a widely distributed low-molecular-mass (LMM) penicillin binding protein (PBP6b) endowed with low dd-carboxypeptidase activity whose functions are still obscure. Our results indicate roles for DacD in assisting biogenesis of particular secretory macromolecules in Gram-negative bacteria and represent to our knowledge the first reported phenotypes for bacterial mutants lacking this LMM PBP.

Metal‐Oxide Nanoparticles with Desired Morphology Inherited from Coordination‐Polymer Precursors

The “escape-by-crafty-scheme” strategy is an efficient approach to prepare metal-oxide nanomaterials with desirable morphology and crystal planes inherited from coordination-polymer nanoparticle precursors, which can be designed and finely tuned by soft chemical assembly of metal ions and organic ligands at the molecular level (see scheme; ptcda=perylene-3,4,9,10-tetracarboxylic dianhydride).

Bridging-ligand-substitution strategy for the preparation of metal–organic polyhedra

Metal-organic polyhedra-discrete molecular architectures constructed through the coordination of metal ions and organic linkers-have recently attracted considerable attention due to their intriguing structures, their potential for a variety of applications and their relevance to biological self-assembly. Several synthetic routes have been investigated to prepare these complexes. However, to date, these preparative methods have typically been based on the direct assembly of metal ions and organic linkers. Although these routes are convenient, it remains difficult to find suitable reaction conditions or to control the outcome of the assembly process. Here, we demonstrate a synthetic strategy based on the substitution of bridging ligands in soluble metal-organic polyhedra. The introduction of linkers with different properties from those of the initial metal-organic polyhedra can thus lead to new metal-organic polyhedra with distinct properties (including size and shape). Furthermore, partial substitution can also occur and form mixed-ligand species that may be difficult to access by means of other approaches.

Formation of (FeCl3)@phenylazomethine dendrimer (DPA): Fine control of the release and encapsulation of Fe ions in dendrimers

Abstract Phenylazomethine dendrimers (DPAs) act as a strong coordination site for metal ion assembly. DPA G4 is regarded as a molecular capsule having 30 metal-assembling sites with a 2.7 nm diameter. We have reported the radial stepwise complexation with Sn2+ ions in the dendrimers, which means the location and number of metal ions can be controlled. Therefore, DPA G4 should realize a ferritin-like redox nanocapsule with precise control of the number of Fe ions. On the other hand, the Fe ion is a typical paramagnetic molecule. For creating an advanced memory with a high density, ferritin is one of the candidates for use as a magnetic quantum dot. Many attempts to use biomaterials, for example, ferritins and chapero-nins, as metal storage capsules have been demonstrated. Some research groups fabricate a device by assembling ferritins on a plate using their rigid and uniform structure. The attempts to use dendrimers have also been demonstrated. We now describe the successful attempt to control the "encapsulation and release" of iron ions in a dendrimer in order to mimic a ferritin through the redox reaction. Furthermore, the assembling structures of (FeCl3) n @DPA on a plate were first observed by scanning tunneling microscopy (STM) as a dendrimer complex, which shows that a highly oriented film is formed on a plate only by solvent casting.

Modular Synthesis of Functional Nanoscale Coordination Polymers

The coordination-directed assembly of metal ions and organic bridging ligands has afforded a variety of bulk-scale hybrid materials with promising characteristics for a number of practical applications, such as gas storage and heterogeneous catalysis. Recently, so-called coordination polymers have emerged as a new class of hybrid nanomaterials. Herein, we highlight advances in the syntheses of both amorphous and crystalline nanoscale coordination polymers. We also illustrate how scaling down these materials to the nano-regime has enabled their use in a broad range of applications including catalysis, spin-crossover, templating, biosensing, biomedical imaging, and anticancer drug delivery. These results underscore the exciting opportunities of developing next-generation functional nanomaterials based on molecular components.

Precise Assembly of Photo-functional Molecules in Phenylazomethine Dendrimer

Precise assembly of photo-functional molecules on dendritic phenylazomethine (DPA) was demonstrated. We previously reported the precise assembly of metal ions on dendritic phenylazomethine in stepwise radical fashion. Triphenylmethylium tetrafluoroborate (TPMBF4) could be coordinated to the imine group of DPA, which allows for control of the number and position of organic molecules in DPA. As one of the applications of an organic molecular assembly, TPM+ derivatives holding a photo-functional molecule, azobenzene (Azo-TPM), were incorporated into DPA stepwisely.

Biomimetic Synthesis of Gold Nanocrystals Using a Reducing Amphiphile

The first synthesis of a chelating and reactive surfactant derived from citric acid and a short silicone as hydrophobic tail is described. Aqueous solutions of this reactive amphiphile spontaneously induce gold ion reduction, particle nucleation, and further direct crystal growth. The process, both pH and light dependent, occurs through lipid-directed assembly of metal ions, their reduction and subsequent lipid-directed growth to yield ultrathin (approximately 7 nm thick) quasi two-dimensional gold nanocrystals.

Electrochemical functions of metallosupramolecular nanomaterials

Self-assembly of metal ions and organic ligands results in the formation of extended or discrete metallosupramolecular structures. In case of neutral ditopic ligands such as bisterpyridines, extended metallosupramolecular coordination polyelectrolytes (MEPEs) are formed. Metal ion-induced self-assembly of 1,4-bis(2,2':6',2''-terpyridin-4'-yl)benzene with Fe(II) or Co(II) results in MEPEs with interesting electrochemical properties. These MEPEs reversibly change their color when oxidized or reduced. The heterometallic MEPE consisting of Fe(II) and Co(II) combines the properties of the individual MEPEs and therefore shows their different states: red-purple, blue, and transparent. On the other hand, complexation of cyclic phenylazomethines with metal ions results in discrete metallosupramolecular structures. We find that metal ion assembly to the organic module occurs in a stepwise fashion because of a difference in the basicity of the imine conformers, and the metal ion assembly can be controlled electrochemically. This example illustrates how metal ion binding can be controlled by the conformation of the receptor, an important step toward assembling organic ligands and metal ions in predictable ways.

Sequential Metal Ion Assembly in Cyclic Phenylazomethine

[reaction: see text] Cyclic phenylazomethines with methylene spacers (CPA-M) are obtained by dehydration of diamine with diketone. During the titration of CPA-M 4mer with FeCl(3), we observe two consecutive isosbestic points in the UV-vis spectra. We conclude that complexation occurs in two consecutive steps. Our analysis suggests that the stepwise metal ion assembly is caused by a difference in the basicity of the imine conformers. Metal ion binding first occurs at the Z imines followed by coordination to the E imine. Finally, metal ion assembly in this compound can be controlled electrochemically.

Metal Ion Assembly in Macromolecules

Self-assembled organic-inorganic hybrid nano-materials have recently received much attention due to their novel and original functions, including new electronic, optical, magnetic, and catalytic properties. Especially, reactions in organic-metallic hybrid materials are closely related to biological reactions, such as the reactions in metal-containing protein, and the controlled metal ions assembly into organic polymers becomes very important. In the first part of this review, recent progresses in two types of organic-inorganic hybrid nano-materials (Organic compounds [character: see text] inorganic mesoporous materials and Metal ions [character: see text] organic polymer) are summarized. In the latter parts, dendrimer-metal complexes, examples of nature-mimetic materials, are introduced, and their controlled metal assembly in dendrimer and their application are reviewed.

Metal‐Organic Frameworks — Prospective Industrial Applications

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