Dynamic Inclusion Complexes of Metal Nanoparticles Inside Nanocups

Host–guest inclusion complexes are abundant in molecular systems and of fundamental importance in living organisms. Realizing a colloidal analogue of a molecular dynamic inclusion complex is challenging because inorganic nanoparticles (NPs) with a well‐defined cavity and portal are difficult to synthesize in high yield and with good structural fidelity. Herein, a generic strategy towards the fabrication of dynamic 1:1 inclusion complexes of metal nanoparticles inside oxide nanocups with high yield (>70 %) and regiospecificity (>90 %) by means of a reactive double Janus nanoparticle intermediate is reported. Experimental evidence confirms that the inclusion complexes are formed by a kinetically controlled mechanism involving a delicate interplay between bipolar galvanic corrosion and alloying–dealloying oxidation. Release of the NP guest from the nanocups can be efficiently triggered by an external stimulus.     

Manganese‐Doped Highly Ordered Mesoporous Silicate with High Efficiency for Oxidation Suppression

Herein, we demonstrate a facile approach to manganese‐doped highly ordered mesoporous silicate with oxidation‐suppression function. As biocompatible supports of guest ions, the ordered mesoporous silicate was synthesized by evaporation‐induced self‐assembly. The phase‐transition from disordered to lamellar structures in the highly ordered mesoporous structure of these porosity‐tuned materials was controlled by adjusting the concentration of a lab‐made polystyrene‐b‐polyethylene oxide copolymer. Manganese was successfully incorporated as a guest in the hexagonally packed mesoporous silicate by using an ultrasound‐assisted technique. The incorporation of manganese ions into the pores of a mesoporous silicate support could be induced for host–guest functional applications. Manganese‐doped mesoporous silicate structures have been examined for their use as antioxidizing agents by electron spin resonance (ESR) measurements and radical‐scavenging tests. The manganese atoms in the mesoporous structures could act in a free‐radical‐scavenging capacity, much like manganese nanoparticles. The high efficiency of their oxidation‐suppression function is extended for application to catalytic products.     

Site‐Selective Functionalization of Periodic Mesoporous Organosilica (PMO) with Macrocyclic Host for Specific and Reversible Recognition of Heavy Metal

A novel kind of macrocyclic‐host‐functionalized periodic mesoporous organosilica (PMO) with excellent and reversible recognition of Pb^II was developed. The macrocyclic host molecule cis‐dicyclohexano[18]crown‐6, with strong affinity to Pb^II, was carefully modified as a bridged precursor to build the PMO material. To break down the limit of the functionalization degree for PMOs incorporated with large‐sized moieties, a site‐selective post‐functionalization method was proposed to further decorate the external surface of the PMO material. The selective recognition ability of the upgraded PMO material towards Pb^II was remarkably enhanced without destroying the mesoporous ordering. Solid‐state ¹³C and ²⁹Si NMR spectroscopy, X‐ray photoelectron spectroscopy (XPS), XRD, TEM, and nitrogen adsorption–desorption isotherm measurements were utilized for a full characterization of the structure, micromorphology, and surface properties. Reversible binding of Pb^II was realized in the binding–elution cycle experiments. The mechanism of the supramolecular interaction between the macrocyclic host and metal ion was discussed. The synthetic strategy can be considered a general way to optimize the properties of PMOs as binding materials for practical use while preserving the mesostructure.     

Dual‐Confined Sulfur Nanoparticles Encapsulated in Hollow TiO2 Spheres Wrapped with Graphene for Lithium–Sulfur Batteries

Lithium–sulfur (Li?S) batteries are attractive owing to their higher energy density and lower cost compared with the universally used lithium‐ion batteries (LIBs), but there are some problems that stop their practical use, such as low utilization and rapid capacity‐fading of the sulfur cathode, which is mainly caused by the shuttle effect, and the uncontrollable deposition of lithium sulfide species. Herein, we report the design and fabrication of dual‐confined sulfur nanoparticles that were encapsulated inside hollow TiO₂ spheres; the encapsulated nanoparticles were prepared by a facile hydrolysis process combined with acid etching, followed by “wrapping” with graphene (G?TiO₂@S). In this unique composite architecture, the hollow TiO₂ spheres acted as effective sulfur carriers by confining the polysulfides and buffering volume changes during the charge‐discharge processes by means of physical force from the hollow spheres and chemical binding between TiO₂ and the polysulfides. Moreover, the graphene‐wrapped skin provided an effective 3D conductive network to improve the electronic conductivity of the sulfur cathode and, at the same time, to further suppress the dissolution of the polysulfides. As results, the G?TiO₂@S hybrids exhibited a high and stable discharge capacity of up to 853.4 mA h g^?1 over 200 cycles at 0.5 C (1 C=1675 mA g^?1) and an excellent rate capability of 675 mA h g^?1 at a current rate of 2 C; thus, G?TiO₂@S holds great promise as a cathode material for Li?S batteries.     

Periodic Mesoporous Organosilica with Molecular‐Scale Ordering Self‐Assembled by Hydrogen Bonds

Nanoporous materials with functional frameworks have attracted attention because of their potential for various applications. Silica‐based mesoporous materials generally consist of amorphous frameworks, whereas a molecular‐scale lamellar ordering within the pore wall has been found for periodic mesoporous organosilicas (PMOs) prepared from bridged organosilane precursors. Formation of a “crystal‐like” framework has been expected to significantly change the physical and chemical properties of PMOs. However, until now, there has been no report on other crystal‐like arrangements. Here, we report a new molecular‐scale ordering induced for a PMO. Our strategy is to form pore walls from precursors exhibiting directional H‐bonding interaction. We demonstrate that the H‐bonded organosilica columns are hexagonally packed within the pore walls. We also show that the H‐bonded pore walls can stably accommodate H‐bonding guest molecules, which represents a new method of modifying the PMO framework.     

A Highly Stable Zeotype Mesoporous Zirconium Metal–Organic Framework with Ultralarge Pores

Through topological rationalization, a zeotype mesoporous Zr‐containing metal–organic framework (MOF), namely PCN‐777, has been designed and synthesized. PCN‐777 exhibits the largest cage size of 3.8 nm and the highest pore volume of 2.8 cm³ g^?1 among reported Zr‐MOFs. Moreover, PCN‐777 shows excellent stability in aqueous environments, which makes it an ideal candidate as a support to incorporate different functional moieties. Through facile internal surface modification, the interaction between PCN‐777 and different guests can be varied to realize efficient immobilization.     

Observation of the Properties of a Single Unit of a Limited CDW Structure in a PtII/PtIV Host–Guest Binary System Based on a Square‐Shaped Complex

A macrocyclic tetranuclear platinum(II) complex [Pt(en)(4,4′‐bpy)]₄(NO₃)₈ ( 1 ?(NO₃)₈; en=ethylenediamine, 4,4′‐bpy=4,4′‐bipyridine) and a mononuclear platinum(IV) complex [Pt(en)₂Br₂]Br₂ ( 2 ?Br₂) formed two kinds of Pt^II/Pt^IV mixed valence assemblies when reacted: a discrete host–guest complex 1 ? 2 ?Br₁₀ ( 3 ) and an extended 1‐D zigzag sheet 1 ?( 2 )₃?Br₈(NO₃)₆ ( 4 ). Single crystal X‐ray analysis showed that the dimensions of the assemblies could be stoichiometrically controlled. Resonance Raman spectra suggested the presence of an intervalence interaction, which is typically observed for quasi‐1‐D halogen‐bridged M^II/M^IV complexes. The intervalence interaction indicates the presence of an isolated {Pt^II???X? Pt^IV? X???Pt^II} moiety in the structure of 4 . On the basis of electronic spectra and polarized reflectance measurements, we conclude that 4 exhibits intervalence charge transfer (IVCT) bands. A Kramers–Kronig transformation was carried out to obtain an optical conductivity spectrum, and two sub‐bands corresponding to slightly different Pt^II–Pt^IV distances were observed.