Synthesis and Temperature‐Induced Morphological Control in a Hybrid Porous Iron–Phosphonate Nanomaterial and Its Excellent Catalytic Activity in the Synthesis of Benzimidazoles

A new organic–inorganic hybrid porous iron–phosphonate material, HPFP‐1, has been synthesized under hydrothermal conditions by using hexamethylenediamine‐N,N,N′,N′‐tetrakis‐(methylphosphonic acid) (HDTMP) as the organophosphorus precursor. The morphology of this material was found to be different at three different temperatures. The material that was synthesized at 453 K showed a flake‐like particle morphology and the material was highly crystalline. Whereas, the materials that were synthesized at 443 K and 423 K were semi‐crystalline and showed rod‐like‐ and spherical morphological features, respectively. SEM and TEM were employed to understand this change in particle morphology depending on the reaction temperature. Powder XRD analysis suggested the formation of a new tetragonal phase in HPFP‐1 (a=11.313, c=15.825 Å; V=2025.659 ų). N₂‐sorption analysis suggested the existence of supermicropores and interparticle mesopores in these materials. Elemental‐ and thermal analyses, as well as FTIR spectroscopy, were employed to verify the composition and framework bonding of the material. The HPFP‐1 material showed excellent catalytic activity for the synthesis of benzimidazole derivatives under mild liquid‐phase reaction conditions.     

Two‐Dimensional Co@N‐Carbon Nanocomposites Facilely Derived from Metal–Organic Framework Nanosheets for Efficient Bifunctional Electrocatalysis

Metal–organic frameworks (MOFs) and MOF‐derived nanomaterials have recently attracted great interest as highly efficient, non‐noble‐metal catalysts. In particular, two‐dimensional MOF nanosheet materials possess the advantages of both 2D layered nanomaterials and MOFs and are considered to be promising nanomaterials. Herein, we report a facile and scalable in situ hydrothermal synthesis of Co–hypoxanthine (HPA) MOF nanosheets, which were then directly carbonized to prepare uniform Co@N‐Carbon nanosheets for efficient bifunctional electrocatalytic hydrogen‐evolution reactions (HERs) and oxygen‐evolution reactions (OERs). The Co embedded in N‐doped carbon shows excellent and stable catalytic performance for bifunctional electrocatalytic OERs and HERs. For OERs, the overpotential of Co@N‐Carbon at 10 mA cm^?2 was 400 mV (vs. reversible hydrogen electrode, RHE). The current density of Co@N‐Carbon reached 100 mA cm^?2 at an overpotential of 560 mV, which showed much better performance than RuO₂; the largest current density of RuO₂ that could be reached was only 44 mA cm^?2. The Tafel slope of Co@N‐Carbon was 61 mV dec^?1, which is comparable to that of commercial RuO₂ (58 mV dec^?1). The excellent electrocatalytic properties can be attributed to the nanosheet structure and well‐dispersed carbon‐encapsulated Co, CoN nanoparticles, and N‐dopant sites, which provided high conductivity and a large number of accessible active sites. The results highlight the great potential of utilizing MOF nanosheet materials as promising templates for the preparation of 2D Co@N‐Carbon materials for electrocatalysis and will pave the way to the development of more efficient 2D nanomaterials for various catalytic applications.     

High‐Yield Synthesis of Amido‐Functionalized Polyoctahedral Oligomeric Silsesquioxanes by Using Acyl Chlorides

Homosubstituted amido‐functionalized polyoctahedral oligomeric silsesquioxanes (POSS) have been synthesized by using acyl chlorides in high yields (ca. 95 %). The method proved to be superior over “conventional” syntheses applying carboxylic acids or acid anhydrides, which are much less efficient (ca. 60 % yield). A palette of aryl and alkyl groups has been used as side‐chains. The structures of the resulting amide‐POSS are supported by multinuclear ¹H, ¹³C, ²⁹Si NMR and FTIR spectroscopy and their full conversion into octasubstituted derivatives was confirmed using mass spectrometry. We also demonstrate that the functionalized silsesquioxanes with bulky organic side‐chains attached to cubic siloxane core form spherical‐like, well‐separated nanoparticles with a size of approximately 5 nm.     

Allyloxyporphyrin‐Functionalized Multiwalled Carbon Nanotubes: Synthesis by Radical Polymerization and Enhanced Optical‐Limiting Properties

Allyloxyporphyrin‐functionalized multiwalled carbon nanotubes (MWCNT‐TPP) were synthesized by radical polymerization and characterized by FTIR, UV/Vis absorption, and X‐ray photoelectron spectroscopy; elemental analysis; TEM; and thermogravimetric analysis. Z‐scan studies revealed that this nanohybrid exhibits enhanced nonlinear optical (NLO) properties compared to a control sample consisting of a covalently unattached physical blend of MWCNTs and porphyrin, as well as to the separate MWCNTs and porphyrin. At the wavelengths used, the mechanism of enhanced optical limiting likely involves reverse saturable absorption, nonlinear scattering, and photoinduced electron/energy transfer between the MWCNTs and the porphyrin. The role of electron/energy transfer in the NLO performance of MWCNT‐TPP was investigated by Raman and fluorescence spectroscopy.     

Polyaniline‐Intercalated Molybdenum Oxide Nanocomposites: Simultaneous Synthesis and their Enhanced Application for Supercapacitor

A new and universal synthetic strategy to hybridize metal oxides and conduct polymer nanocomposites has been proposed in this work. The simultaneous reaction process, which includes the generation of metal oxide layers, the oxidation polymerization of monomers, and the in situ formation of polymer–metal oxides sandwich structure is successfully realized and results in the unique hybrid polyaniline (PANI)‐intercalated molybdenum oxide nanocomposites. The peroxomolybdate proved to play a dual role as the precursor of the inorganic hosts and the oxidizing agent for polymerization. The as‐obtained hybrid nanocomposites present a flexible lamellar structure by oriented assembly of conductive PANI chains in the MoO₃ interlayer, and thus inherit excellent electrical performance and possess the potential of active electrode materials for electrochemical energy storage. Such uniform lamellar structure together with the anticipated high conductivity of the hybrid PANI/MoO₃ nanocomposites afford high specific capacitance and good stability during the charge–discharge cycling for supercapacitor application.     

Hybrid Porous Materials with High Surface Area Derived from Bromophenylethenyl‐Functionalized Cubic Siloxane‐Based Building Units

Sonogashira cross‐coupling of bromophenylethenyl‐terminated cubic, double four‐ring, siloxane cages with di‐/triethynyl compounds results in microporous poly(ethynylene aryleneethenylene silsesquioxane) networks, simply termed as polyorganosiloxane networks (PSNs). In comparison with porous organic polymers reported previously, these PSNs show relatively high surface area and comparable thermal stability. Their apparent BET specific surface areas vary in the range of 850–1040 m² g^?1 depending on the length and the connectable sites of the ethynyl compounds. Analyses of pore size distribution revealed bimodal micropores with relatively narrow distribution. The degree of cross‐linking affects the degree of cleavage of the siloxane bonds, and this suggests that partial cleavage of the siloxane cages is mainly a result of cage distortion. Hydrogen adsorption was performed to evaluate potential of the PSNs as hydrogen storage media. Uptakes of up to 1.19 wt % at 77 K and 760 Torr and initial isosteric heats of adsorption as high as 8.0 kJ mol^?1 were observed. These materials have been obtained by a combination of structural, synthetic organic, and materials chemistry, which can exploited to synthesize porous hybrid materials with specifically designed structures and functions.     

Well‐Defined Metal–Organic Framework Hollow Nanocages

Metal–organic frameworks (MOFs) have demonstrated great potentials in a variety of important applications. To enhance the inherent properties and endow materials with multifunctionality, the rational design and synthesis of MOFs with nanoscale porosity and hollow feature is highly desired and remains a great challenge. In this work, the formation of a series of well‐defined MOF (MOF‐5, Fe^II‐MOF‐5, Fe^III‐MOF‐5) hollow nanocages by a facile solvothermal method, without any additional supporting template is reported. A surface‐energy‐driven mechanism may be responsible for the formation of hollow nanocages. The addition of pre‐synthesized poly(vinylpyrrolidone)‐ (PVP) capped noble‐metal nanoparticles into the synthetic system of MOF hollow nanocages yields the yolk–shell noble metal@MOF nanostructures. The present strategy to fabricate hollow and yolk–shell nanostructures is expected to open up exciting opportunities for developing a novel class of inorganic–organic hybrid functional nanomaterials.     

Tris‐Functionalized Hybrid Anderson Polyoxometalates: Synthesis,Characterization, Hydrolytic Stability and Inversion of Protein Surface Charge

Single‐ and double‐sided functionalized hybrid organic–inorganic Anderson polyoxomolybdates with Ga^III and Fe^III positioned as central heteroatoms have been synthesized in a mild, two‐step synthesis in an aqueous medium. Compounds 1 – 4 were isolated as hydrated salts, [TBA]₃[GaMo₆O₁₈(OH)₃{(OCH₂)₃CCH₂OH}]×12 H₂O ( 1 ) (TBA=tetrabutylammonium), Na₃[FeMo₆O₁₈{(OCH₂)₃CCH₂OH}₂]×11 H₂O ( 2 ), [TMA]₂[GaMo₆O₁₈(OH)₃{(OCH₂)₃CNH₃}]×7 H₂O ( 3 ) (TMA=tetramethylammonium), and Na[TMA]₂[FeMo₆O₁₈(OH)₃{(OCH₂)₃CNH₃}](OH)×6 H₂O ( 4 ). All the compounds were characterized based on single‐crystal X‐ray diffraction (SXRD), FTIR, UV/Vis, thermogravimetric, ESI‐MS, NMR, and elemental analyses. Compound 1 was also crystallized with two smaller organic cations, giving [TMA]₃[GaMo₆O₁₈(OH)₃{(OCH₂)₃CCH₂OH}]×n H₂O ( 5 ) and [GDM]₃[GaMo₆O₁₈(OH)₃{(OCH₂)₃CCH₂OH}]×n H₂O ( 6 ) (GDM=guanidinium) and were characterized based on UV/Vis, NMR, FTIR, and elemental analyses. The use of these compounds as additives in macromolecular crystallography was investigated by examining their hydrolytic stability by using ESI‐MS in a pH range of 4 to 9. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) analysis showed that BSA remains intact in a solution containing up to 100 equivalents of 1 or 4 over more than four days at 20 °C. Zeta potential measurements demonstrate that 1 – 4 induce charge inversions on the positively charged surface of BSA (1 mg mL^?1) with concentrations starting as low as 1.29 mM for compounds 1 and 2 , which have the highest negative surface charge.     

Hierarchical MoS2@Carbon Microspheres as Advanced Anodes for Li‐Ion Batteries

Hierarchical hybridized nanocomposites with rationally constructed compositions and structures have been considered key for achieving superior Li‐ion battery performance owing to their enhanced properties, such as fast lithium ion diffusion, good collection and transport of electrons, and a buffer zone for relieving the large volume variations during cycling processes. Hierarchical MoS₂@carbon microspheres (HMCM) have been synthesized in a facile hydrothermal treatment. The structure analyses reveal that ultrathin MoS₂ nanoflakes (ca. 2–5 nm) are vertically supported on the surface of carbon nanospheres. The reversible capacity of the HMCM nanocomposite is maintained at 650 mA h g^?1 after 300 cycles at 1 A g^?1. Furthermore, the capacity can reach 477 mA h g^?1 even at a high current density of 4 A g^?1. The outstanding electrochemical performance of HMCM is attributed to the synergetic effect between the carbon spheres and the ultrathin MoS₂ nanoflakes. Additionally, the carbon matrix can supply conductive networks and prevent the aggregation of layered MoS₂ during the charge/discharge process; and ultrathin MoS₂ nanoflakes with enlarged surface areas, which can guarantee the flow of the electrolyte, provide more active sites and reduce the diffusion energy barrier of Li⁺ ions.     

Hydrogen‐Bond‐Assisted “Gold Cold Fusion” for Fabrication of 2D Web Structures

Keeping their cool : Fabrication of a 2D weblike nanonetwork of gold was successfully demonstrated through a two‐step procedure including complexation of gold precursors to a weblike supramolecular assembly of surfactant followed by in situ reduction of the precursors to gold. Molecular assemblies stabilized by hydrogen bonding provided a sound template, leading to the highly integrated structure of gold through room‐temperature (cold) nanostructure fusion.

     

Cooperative and FRET‐Assisted Brightness Enhancement in Oligo(phenylene ethynylene): Quantum Dot Organic–Inorganic Nanohybrids

Herein, we combine the ideas of concerted emission from fluorophore ensembles and its further amplification through FRET in an organic–inorganic hybrid approach. Spherical and highly fluorescent organic nanoparticles (FONPs, Φ_f=0.38), prepared by the self‐assembly of oligo(phenylene ethynylene) (OPE) molecules, were selected as a potential donor material. This organic core was then decorated with a shell of fluorescent CdSe/ZnS core–shell quantum dots (QDs; <d>?5.5 nm, Φ_f=0.27) with the aid of a bifunctional ligand, mercaptopropionic acid. Its high extinction coefficient (?≈4.1×10⁵ m ^?1 cm^?1) and good spectral match with the emission of the FONPs (J(λ)≈4.08×10¹⁶ m ^?1 cm^?1 nm⁴) made them a better acceptor candidate to constitute an efficient FRET pair (Φ_FRET=0.8). As a result, the QD fluorescence intensity was enhanced by more than twofold. The fundamental calculations carried out indicated an improvement in all the FRET parameters as the number of QDs around the FONPs was increased. This, together with the localization of multiple QDs in a nanometric dimension (volume≈1.8×10⁶ nm³), gave highly bright reddish luminescent hybrid particles as visualized under a fluorescence microscope.     

Functionalized Organotin‐Chalcogenide Complexes That Exhibit Defect Heterocubane Scaffolds: Formation,Synthesis, and Characterization

The synthesis of new functionalized organotin‐chalcogenide complexes was achieved by systematic optimization of the reaction conditions. The structures of compounds [(R^{1, 2}Sn)₃S₄Cl] ( 1 , 2 ), [((R²Sn)₂SnS₄)₂(μ‐S)₂] ( 3 ), [(R^{1, 2}Sn)₃Se₄][SnCl₃] ( 4, 5 ), and [Li(thf)_n][(R³Sn)(HR³Sn)₂Se₄Cl] ( 6 ), in which R¹=CMe₂CH₂C(O)Me, R²=CMe₂CH₂C(NNH₂)Me, and R³=CH₂CH₂COO, are based on defect heterocubane scaffolds, as shown by X‐ray diffraction, ¹¹⁹Sn NMR spectroscopy, and ESI mass spectrometry analyses. Compounds 4 , 5 , and 6 constitute the first examples of defect heterocubane‐type metal‐chalcogenide complexes that are comprised of selenide ligands. Comprehensive DFT calculations prompted us to search for the formal intermediates [(R¹SnCl₂)₂(μ‐S)] ( 7 ) and [(R¹SnCl)₂(μ‐S)₂] ( 8 ), which were isolated and helped to understand the stepwise formation of compounds 1 – 6 .