Modulation of Electron Push-Pull by Redox Non-Innocent Additives for Long Cycle Life Zinc Anode.

Application of an aqueous Zn-ion battery is plagued by a water-induced hydrogen evolution reaction (HER), resulting in local pH variations and an unstable electrode-electrolyte interface (EEI) with uncontrolled Zn plating and side reactions. Here, 4-methyl pyridine N-oxide (PNO) is introduced as a redox non-innocent additive that comprises a hydrophilic bipolar N+-O- ion pair as a coordinating ligand for Zn and a hydrophobic ─CH3 group at the para position of the pyridine ring that reduces water activity at the EEI, thereby enhancing stability. The N+-O- moiety of PNO possesses the unique functionality of an efficient push electron donor and pull electron acceptor, thus maintaining the desired pH during charging/discharging. Intriguingly, replacing ─CH3 (electron pushing +I effect) by ─CF3 group (electron pulling ─I effect), however, does not improve the reversibility; instead, it degrades the cell performance. The electrolyte with 2 m ZnSO4 + 15 mm PNO enables symmetric cell Zn plating/stripping for a remarkable > 10 000 h at 0.5 mA cm-2 and exhibits coulombic efficiency (CE) ≈99.61% at 0.8 mA cm-2 in Zn/Cu asymmetric cell. This work showcases the immense interplay of the electron push-pull of the additives on the cycling.

Harvesting solar light with crystalline carbon nitrides for efficient photocatalytic hydrogen evolution.

Described herein is the photocatalytic hydrogen evolution using crystalline carbon nitrides (CNs) obtained by supramolecular aggregation followed by ionic melt polycondensation (IMP) using melamine and 2,4,6-triaminopyrimidine as a dopant. The solid state NMR spectrum of (15)N-enriched CN confirms the triazine as a building unit. Controlling the amount and arrangements of dopants in the CN structure can dramatically enhance the photocatalytic performance for H2 evolution. The polytriazine imide (PTI) exhibits the apparent quantum efficiency (AQE) of 15% at 400 nm. This method successfully enables a substantial amount of visible light to be harvested for H2 evolution, and provides a promising route for the rational design of a variety of highly active crystalline CN photocatalysts.

Thermochemistry of paddle wheel MOFs: Cu-HKUST-1 and Zn-HKUST-1.

Metal-organic framework (MOF) porosity relies upon robust metal-organic bonds to retain structural rigidity upon solvent removal. Both the as-synthesized and activated Cu and Zn polymorphs of HKUST-1 were studied by room temperature acid solution calorimetry. Their enthalpies of formation from dense assemblages (metal oxide (ZnO or CuO), trimesic acid (TMA), and N,N-dimethylformamide (DMF)) were calculated from the calorimetric data. The enthalpy of formation (ΔHf) of the as-synthesized Cu-HKUST-H2O ([Cu3TMA2·3H2O]·5DMF) is -52.70 ± 0.34 kJ per mole of Cu. The ΔHf for Zn-HKUST-DMF ([Zn3TMA2·3DMF]·2DMF) is -54.22 ± 0.57 kJ per mole of Zn. The desolvated Cu-HKUST-dg [Cu3TMA2] has a ΔHf of 16.66 ± 0.51 kJ/mol per mole Cu. The ΔHf for Zn-HKUST-amorph [Zn3TMA2·2DMF] is -3.57 ± 0.21 kJ per mole of Zn. Solvent stabilizes the Cu-HKUST-H2O by -69.4 kJ per mole of Cu and Zn-HKUST-DMF by at least -50.7 kJ per mole of Zn. Such strong chemisorption of solvent is similar in magnitude to the strongly exothermic binding at low coverage for chemisorbed H2O on transition metal oxide nanoparticle surfaces. The strongly exothermic solvent-framework interaction suggests that solvent can play a critical role in obtaining a specific secondary building unit (SBU) topology.

Fine dispersion of BiFeO3 nanocrystallites over highly ordered mesoporous silica material and its photocatalytic property.

Highly crystalline pure phase multi-ferroic bismuth ferrite nanoparticles have been integrated into the ordered mesoporous silica material through one pot synthesis protocol. Here, amphiphilic tri-block copolymer Pluronic P123 is being used as structure-directing agent. High temperature heating during calcination and acid treatment eliminates the presence of probable impurity phases. The existence of large uniform ordered mesopores with hexagonal pore architecture are evidenced from the small angle powder XRD, TEM image analysis and N2 adsorption/desorption isotherms. The material has considerably small optical band gap of 2.16 eV. The large specific surface area (396 m2 g(-1)) along with high crystallinity and small optical band gap of mesoporous bismuth ferrite loaded silica nanocomposite (MBFSN-1) materials suggested their potential utility as photocatalyst. Intriguingly, it completely decomposes methyl orange dye under UV-visible light irradiation within only 1 h and together with good reusability.

Synergistic Effects of Earth-Abundant Metal-Metal Oxide Enable Reductive Amination of Carbonyls at 50 °C.

Reductive amination of carbonyls to primary amines is of importance to the synthesis of fine chemicals; however, this reaction with heterogeneous catalysts containing earth-abundant metals under mild conditions remains scarce. Here, we show that the nickel catalyst with mixed oxidation states enables such synthesis of primary amines under low temperature (50 °C) and H2 pressure (0.9 MPa). The catalyst shows activity in both water and toluene. The high activity likely results from the formation of small (ca. 4.6 nm) partially oxidized nickel nanoparticles (NPs) homogeneously anchored onto the silica and their synergistic effect. Detailed characterizations indicate stabilization of NPs through strong metal support interaction via electron donation from the metal to support. We identify that the support endowed with an amphoteric nature shows better performance. This strategy of making small metal-metal oxide NPs will open an avenue toward the rational development of efficient catalysts that would allow for other organic transformations under mild reaction conditions.

Nitrogen-rich porous covalent imine network (CIN) material as an efficient catalytic support for C-C coupling reactions.

In an effort to expand the realm of possibilities of nitrogen-rich porous materials that could be used in catalysis, herein we report the synthesis of a new highly nitrogen rich (ca. 45%) porous covalent imine network (CIN-1) material employing simple Schiff base chemistry and further grafting its surface with palladium. Pd-loaded CIN-1 support acts as a truly heterogeneous catalyst towards Suzuki C-C coupling reaction between aryl halides with arylboronic acids. High surface area and excellent accessibility of the catalytic sites make it very efficient for heterogeneous catalysis. The stability of the catalyst due to intimate contact between nitrogen-rich organic support and metal allows several reuses with only a minor loss in catalytic activity.

Hollow spherical mesoporous phosphosilicate nanoparticles as a delivery vehicle for an antibiotic drug.

Mesoporous phosphosilicate nanoparticles of hollow sphere architecture have been prepared hydrothermally for the first time under acidic pH conditions and this material is found to be efficient in encapsulating an antibiotic drug and its controlled release at physiological pH for possible cargo delivery applications.

Highly porous Co(II)-salicylate metal-organic framework: synthesis, characterization and magnetic properties.

A new porous Co(II)-salicylate metal-organic framework material has been synthesized hydrothermally through the reaction of Co(II) chloride with sodium salicylate under mild alkaline pH conditions. To get an idea about the structural aspect of the material from the powder X-ray diffraction (PXRD) pattern, MAUD program has been successfully utilized and the assigned peaks match very well with a new tetragonal phase (space group, P4mm) having the unit cell parameters: a = b = 12.957 (0.042) Å; c = 12.738 (0.019) Å; α = ß = γ = 90°, V = 2138.73 Å(3). N(2) adsorption/desorption analyses suggested the material is highly porous in nature having high BET surface area and pore dimensions of 2.0-3.0 nm, which is within the range of small mesopores. Thermogravimetric analysis (TGA) revealed that the H(2)O molecules may be removed from the framework without collapsing the structure and the material is stable up to ca. 573 K. The material is characterized thoroughly by using different characterization tools such as TEM, SEM, UV-visible reflectance spectroscopy, FT IR spectroscopy and photoluminescence spectroscopy. X-Ray photoelectron spectroscopic (XPS) analysis was employed to understand the oxidation state of the cobalt atom and presence of other elements within the framework. The material shows interesting magnetic properties, where the magnetic moments monotonically increase with the decrease in temperature down to 9 K. Below 9 K there is a steep increase in magnetization on further lowering the temperature, thereby suggesting the onset of a long range ferromagnetic transition with ferromagnetic Curie temperature, T(C) = 8.5 K. Furthermore, the M-H curve at 2 K shows a clear hysteresis loop with a coercive field 150 Oe and remnant magnetization 0.8 µ(B)/f.u.

Self-assembled TiO(2) nanoparticles: mesoporosity, optical and catalytic properties.

Herein, we explore the idea of self-assembly of nearly monodisperse nanoparticles as uniform building blocks to design highly crystalline mesoporous TiO(2) nanoparticles, through evaporation-induced self-assembly (EISA) and hydrothermal methods by using non-ionic Pluronic F127 and anionic surfactant SDS, respectively as structure directing agents. The small- and wide-angle powder X-ray diffraction and transmission electron microscopy (TEM) are used to characterize the mesophases. N(2) adsorption-desorption studies and high-resolution TEM results further reveal that mesopores are formed by the arrangement of the nanoparticles of size ca. 4.0-5.0 nm for SDS-templated and 8.0-9.0 nm for F127-templated TiO(2) nanoparticles with broad interparticle pore size distribution. Optical properties of these nanomaterials are studied by UV-visible diffuse-reflectance spectroscopy, photoluminescence (PL) and time-resolved fluorescence (TCSPC). These nanostructured titania exhibited excellent catalytic activity in the photodegradation of ecologically abundant dyes Methylene blue and Rose Bengal under UV-visible light irradiation.