Hydrogen-Bonded Framework of a Polyanionic Cluster and Its Growth from 2D to 3D for Dual-Selective Adsorption and pH-Controlled Oxidation

For fabricating a hydrogen-bonded framework with a stabilized hybrid structure for versatile functional properties, an inorganic polyanionic cluster that bears covalently grafted organic groups for hydrogen bond connection is synthesized. By modifying two guanine groups into a disklike polyoxometalate [Mn(OH)6Mo6O18]3– on both sides symmetrically, a polyanionic hybrid building block is obtained. With the cluster serving as a bridge and the grafted guanine unit serving as the binding sites, a polyoxometalate built-in hydrogen-bonded framework in the form of a square lattice shape within a two-dimensional plane has been fabricated as a single-layer assembly. In a further step, the counterion connection and hydrophilic/hydrophobic effect are used to drive the growth of layered framework assembly along the perpendicular direction. The resulting cluster-embedded framework possesses permanent porosity and inner-layer ionic characteristics after activation, which allows the framework to exhibit both high charge-/size-selective adsorption of organic cations and pH-controlled catalytic oxidation of methionine via the charged property

Controlled Triol-Derivative Bonding and Decoration Transformation on Cu-Centered Anderson–Evans Polyoxometalates

To create new types of organic ligands covalently grafted onto polyoxometalates and identify the reaction mechanism, we selected Cu^II as the central heteroatom for the synthesis of a series of disklike Anderson–Evans clusters bearing different triol derivatives on both their faces via one-pot and/or step-by-step routes. By using a [(n-C₄H₉)₄N]₄[Mo₈O₂₆] precursor cluster and copper acetate as the starting materials, several organically modified χ isomers with Cu^II heteroatom centers were obtained. Starting from a [(n-C₄H₉)₄N]₂[Mo₂O₇] subcluster, however, a half-malposition coordination fashion of triol ligands with a δ isomer on one face and a χ isomer on the other face of the Anderson–Evans cluster was obtained. By changing the reaction solvent from acetonitrile to methanol, we realized a secondary organic modification of the triol-grafted clusters and obtained a triol ligand/methanol codecoration on the Anderson–Evans polyoxometalate. In addition, by changing the reaction environment, we succeeded in modulating the transformation of triol ligands from one site to another on the polyoxometalate cluster. Importantly, by control of the reaction condition, the methanol molecules were also taken off from the cluster

A closed hollow capsule structure assembled by double acetate-decorated Anderson-like polyanions

<p>An inorganic–organic hybrid vanadotungstate, Na₆[VW₆O₂₂(CH₃COO)₃]·11H₂O (<b>1</b>), was synthesized in aqueous solution and characterized by infrared spectrum, elemental analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy, and single-crystal X-ray diffraction. The result of the single-crystal X-ray diffraction analysis reveals that the polyanion of <b>1</b> is an acetate single-sided decorated Anderson-like polyoxotungstate with a V^V in the central tetrahedral position. For better understanding of the characteristic distinction between <b>1</b> and the classical Anderson-type polyanion, we synthesized a triol ligand single-side anchored on the Anderson-type polyoxometalate, [(n-C₄H₉)₄N]₃{AlMo₆O₁₈(OH)₃[(CH₂O)₃CNHCOC₅H₄N]}·8H₂O (<b>2</b>), as a comparison. One interesting architectural feature of <b>1</b> is that two polyanions [VW₆O₂₂(CH₃COO)₃]⁶⁻ are linked by six sodium cations on the same plane to form a closed hollow capsule structure with the inner major axis of 8.54 Å and minor axis of 3.11 Å. As basic building blocks, the closed hollow capsule moieties are assembled into 1D chain-like structures through direct Na−O bonds without additional linkers. The electrochemical behavior of <b>1</b> was investigated in pH 4.8 buffer solution to investigate its potential application in electrochemical catalysis; <b>1</b> has good catalytic activity for oxidation of thioanisole.</p

Self-Assembly of an Europium-Containing Polyoxometalate and the Arginine/Lysine-Rich Peptides from Human Papillomavirus Capsid Protein L1 in Forming Luminescence-Enhanced Hybrid Nanoparticles

Through a self-assembly of arginine/lysine-rich peptide from human papillomavirus (HPV) capsid protein and an Eu-containing polyoxometalate (POM), Na₉[EuW₁₀O₃₆]·32H₂O (EuW10), the formation of well-defined hybrid nanospheres in aqueous solution is presented, showing large luminescence enhancement of POM and use as a potential “turn-on” fluorescence probe in biology. The binding mechanisms between them have been explored at the molecular level by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), fluorescence spectra, isothermal titration calorimetry (ITC), ζ-potential, and nuclear magnetic resonance (¹H NMR) titration spectra. ITC study confirmed the assembly was completely enthalpy driven, and ζ-potential proved that the driving force was governed mainly by the electrostatic interaction. ¹H NMR spectroscopy indicated changes in hydrogen bond of EuW10 and the peptide segment, and the binding model was clarified. Our design constructed the self-assembly fabrication of well-defined nanoparticles by using inorganic POM and bioapplicable peptide combined with strong fluorescence characterization together. The enhanced luminescence and specific targeted-HPV peptide ability would be important and useful in the detection of HPV capsid protein and/or HPV genotypes, and such a protocol could be extended to another virus once using the corresponding peptides. Therefore, the present report will be helpful to promote the development of antivirus agents in the future

In Situ Grown Coordination-Supramolecular Layer Holding 3D Charged Channels for Highly Reversible Zn Anodes

Dynamic reversible noncovalent interactions make supramolecular framework (SF) structures flexible and designable. A three-dimensional (3D) growth of such frameworks is beneficial to improve the structure stability while maintaining unique properties. Here, through the ionic interaction of the polyoxometalate cluster, coordination of zinc ions with cationic terpyridine, and hydrogen bonding of grafted carboxyl groups, the construction of a 3D SF at a well-crystallized state is realized. The framework can grow in situ on the Zn surface, further extending laterally into a full covering without defects. Relying on the dissolution and the postcoordination effects, the 3D SF layer is used as an artificial solid electrolyte interphase to improve the Zn-anode performance. The uniformly distributed clusters within nanosized pores create a negatively charged nanochannel, accelerating zinc ion transfer and homogenizing zinc deposition. The 3D SF/Zn symmetric cells demonstrate high stability for over 3000 h at a current density of 5 mA cm–2

Structural Design Strategy of a Biobased Allyl Compound with Dynamic Boronic Ester Bonds to Form Rigid-Soft Self-Healing Polymer Networks via Thiol–Ene “Click” Photopolymerization for Integrated Preparation of a Flexible Device

Fabricating biobased flexible polymers with high toughness and self-healing ability will promote sustainable development of the fast-growing flexible electronic industry. Herein, a biobased allyl compound (BAMDB) with boronic ester bonds was synthesized from renewable eugenol and then combined with multifunctional thiol via thiol–ene “click” photopolymerization to form a series of flexible networks (BAMDB-SH). Their integrated performance, including thermal, optical, and mechanical properties as well as self-healing behavior, was studied. Their glass transition temperature ranged from 42 to 55 °C and showed high transparency (88.2–89.3% at 550 nm). At the same time, BAMDB-SH3 has the most excellent comprehensive mechanical properties with a tensile strength, an elongation at break, and a toughness of 29.8 MPa, 194.3%, and 35.3 MJ m–3, respectively, owing to its rigid-soft network structure with appropriate cross-linking density. Depending on the dynamic exchange of boronic ester bonds, BAMDB-SH3 networks could be healed in 30 min at 80 °C with a high self-healing efficiency of 98%. In addition, based on the excellent comprehensive performance and self-healing properties of BAMDB-SH3, it was used to prepare a sandwich sensor by integrated encapsulation of silver nanowires for wrist activity detection, demonstrating the potential applications of BAMDB-SH in flexible devices

Fabrication of Polyamide 6 Nanocomposite with Improved Thermal Conductivity and Mechanical Properties via Incorporation of Low Graphene Content

A 3D graphene network was constructed in polyamide 6 (PA6) monomers through the reduction and self-assembly of graphene oxide (GO), and then PA6 nanocomposites with low graphene content were fabricated through in situ polymerization. The effects of the 3D graphene network on the structure and properties of the PA6 were systematically investigated. Results show that the 3D graphene network can significantly improve the thermal conductivity of PA6. In the case of the PA6 with only 0.25 wt % graphene, its thermal conductivity is 0.69 W/(m K), about 2.88 times of that of the pure PA6. This improvement is attributed to the more-compact thermal conductive paths of the 3D graphene network, and its stronger interfacial interaction with PA6 in this work compares with those of pre-synthesized free-standing 3D graphene networks. Moreover, the mechanical properties and water resistance of PA6 also have significantly improved with the incorporation of the 3D graphene network

Solvent Dielectricity-Modulated Helical Assembly and Morphologic Transformation of Achiral Surfactant-Inorganic Cluster Ionic Complexes

Ionic complexes comprising single/double chain cationic surfactant and Lindqvist-type polyoxomolybdate anionic cluster were used for controlled self-assembly in organic solutions. In the solvent with low dielectric constant the complexes self-assembled into flat ribbon like lamellar aggregations with an inverse bilayer substructure where the cluster located at the middle. Under the condition of increased dielectric constant, the solvent triggered the formation of helical self-assemblies, which finally transformed from helical ribbons to the flower-like assemblies due to the bilayer becoming excessively twisted. The self-assembled morphology and the substructure were characterized by SEM, TEM, and XRD. The solvent dielectricity-controlled morphologic transformations modulated by the variation of electrostatic interactions between organic cations and inorganic polyanions were demonstrated by ¹H NMR and IR spectra. The strategy in this work represents an effective route in targeting the chirality-directed functionalization of inorganic clusters by combining controllable and helical assemblies of achiral polyoxometalate complexes in one system

Hybrid Assembly toward Enhanced Thermal Stability of Virus-like Particles and Antibacterial Activity of Polyoxometalates

In an effort to improve both the stability of virus-like particles (VLPs) and the medical activity of polyoxometalates (POMs), a new hybrid assembly system between human papillomavirus (HPV) capsid protein L1 and a europium-containing POM (EuW₁₀) has been constructed, for the first time, via the electrostatic interactions between them. The co-assembly of EuW₁₀ and HPV 16 L1-pentamer (L1-p) in buffer solution resulted in the encapsulation of POMs in the cavity of VLPs, which was further confirmed by cesium chloride (CsCl) gradient ultracentrifugation, SDS-PAGE, dynamic light scattering, and transmission electron microscopy, whereas the post-assembly of EuW₁₀ with the as-prepared VLPs leads to the adsorption of POMs only on the external surface of particles, and both cases improved the thermal and storage stabilities of VLPs obviously. Particularly, the encapsulation of POMs in VLPs largely improved the antibacterial activity of EuW₁₀, and thereby, the present study will be significant for both the stability improvement of protein vaccines and the development of POM medicine

3D-Printed Photocurable Resin with Synergistic Hydrogen Bonding Based on Deep Eutectic Solvent

Vat polymerization, one of the 3D printing technologies, has been widely applied owing to its advantageous properties, such as high accuracy and surface quality. However, the applicability of this technology is limited to end-use product manufacturing, requiring advancements due to a gradual increase in the performance requirements and functional demands of the products. In this study, deep eutectic solvent-based photocurable resins (PCRs) with synergistic hydrogen bonding are synthesized using a facile and ecofriendly procedure to tune monomer proportions. The as-prepared PCRs, with ultralow viscosity and ultrahigh curing rate, are compatible with commercial liquid-crystal display printers. The 3D-printed parts with high optical transparency, stiffness, and thermal resistance exhibit humidity-dependent electrical conductivity and mechanical properties. In addition, the 3D-printed objects demonstrate self-healing features due to the synergistic effect of high-density hydrogen bonding in the microphase-separated polymer matrix. Moreover, different categories of structural assembly, from 2D to 3D and small to large, are demonstrated, and their solubility ensued in recycling and remolding. The synthesized PCRs are suitable for fabricating sacrificial molds, enabling the on-demand fabrication of precise multifunctional structures with various materials, which are otherwise incompatible with UV-based 3D printing, facilitating 3D printing by overcoming its material-selection limitations