High-Efficiency Solar Transformation of Sugars via a Heterogenous Gallium(III) Catalyst.

Extremely limited research exploring the photocatalytic potential of main group metals, such as aluminum, gallium, and tin, has been undertaken due to their weak light harvesting properties. This study reports the efficient transformation of sugars to 5-hydroxymethylfurfural (HMF) with high yield employing an original heterogeneous photocatalyst comprising a gallium(III) complex immobilized on an alumina support. Under visible light irradiation, the reaction rate of HMF formation is ~143 times higher than the equivalent thermal reaction performed in the absence of light.

Optimal Oxophilicity at the Fe-N Interface Enhances the Generation of Singlet Oxygen for Efficient Fenton-Like Catalysis.

In the pursuit of efficient singlet oxygen generation in Fenton-like catalysis, the utilization of single-atom catalysts (SACs) emerges as a highly desired strategy. Here, a discovery is reported that the single-atom Fe coordinated with five N-atoms on N-doped porous carbon, denoted as Fe-N/NC, outperform its counterparts, those coordinated with four (Fe-N/NC) or six N-atoms (Fe-N/NC), as well as state-of-the-art SACs comprising other transition metals. Thus, Fe-N/NC exhibits exceptional efficacy in activating peroxymonosulfate for the degradation of organic pollutants.

Cu@CuO/WO with photo-regulated singlet oxygen and oxygen adatoms generation for selective photocatalytic aromatic amines to imines.

Photocatalysts can absorb light and activate molecular O under mild conditions, but the generation of unsuitable reactive oxygen species often limits their use in synthesizing fine chemicals. To address this issue, we disperse 1 wt% copper on tungsten trioxide (WO) support to create an efficient catalyst for selective oxidative coupling of aromatic amines to imines under sunlight irradiation at room temperature. Copper consists of a metallic copper core and an oxide shell.

Photocatalytic conversion of sugars to 5-hydroxymethylfurfural using aluminium(III) and fulvic acid.

5-hydroxymethylfurfural (HMF) is a valuable and essential platform chemical for establishing a sustainable, eco-friendly fine-chemical and pharmaceutical industry based on biomass. The cost-effective production of HMF from abundant C6 sugars requires mild reaction temperatures and efficient catalysts from naturally abundant materials. Herein, we report how fulvic acid forms complexes with Al ions that exhibit solar absorption and photocatalytic activity for glucose conversion to HMF in one-pot reaction, in good yield (~60%) and at moderate temperatures (80 °C).

High Nitrile Yields of Aerobic Ammoxidation of Alcohols Achieved by Generating O and Br Radicals over Iron-Modified TiO Photocatalysts.

Catalytic ammoxidation of alcohols into nitriles is an essential reaction in organic synthesis. While highly desirable, conducting the synthesis at room temperature is challenging, using NH as the nitrogen source, O as the oxidant, and a catalyst without noble metals. Herein, we report robust photocatalysts consisting of Fe(III)-modified titanium dioxide (Fe/TiO) for ammoxidation reactions at room temperature utilizing oxygen at atmospheric pressure, NH as the nitrogen source, and NHBr as an additive.

Plasmonic Silver-Nanoparticle-Catalysed Hydrogen Abstraction from the C(sp )-H Bond of the Benzylic C atom for Cleavage of Alkyl Aryl Ether Bonds.

Selective activation of the C(sp )-H bond is an important process in organic synthesis, where efficiently activating a specific C(sp )-H bond without causing side reactions remains one of chemistry's great challenges. Here we report that illuminated plasmonic silver metal nanoparticles (NPs) can abstract hydrogen from the C(sp )-H bond of the C atom of an alkyl aryl ether β-O-4 linkage. The intense electromagnetic near-field generated at the illuminated plasmonic NPs promotes chemisorption of the β-O-4 compound and the transfer of photo-generated hot electrons from the NPs to the adsorbed molecules leads to hydrogen abstraction and direct cleavage of the unreactive ether C -O bond under moderate reaction conditions (≈90 °C).

Nanostructure Shape-Effects in ZnO heterogeneous photocatalysis.

Selective oxidation of alcohols is an essential reaction for fine chemical production. Here, the photocatalytic oxidation of benzyl alcohol by zinc oxide (ZnO) nanocrystals was investigated to clarify the mechanism of selective oxidation with this process. Reactivity when in contact with three distinct ZnO nanocrystal shapes: nanocones, nanorods and nanoplates, was studied in order to compare crystal facet-specific effects in the reaction system.

Oxidative Esterification of 5-Hydroxymethylfurfural into Dimethyl 2,5-Furandicarboxylate Using Gamma Alumina-Supported Gold Nanoparticles.

Gold nanoparticles (Au NPs) supported on a nanostructured gamma alumina (γ-AlO) fiber can exhibit excellent catalytic activity for the conversion of 5-hydroxymethylfurfural to produce its ester derivative, dimethyl 2,5-furandicarboxylate (FDMC). γ-AlO was synthesized using a PEG surfactant to generate oxide fibers that randomly stack together into irregular shapes. The average particle sizes of the Au NPs are 1-6 nm, where the catalytically active Au (111) surface is the exposed facet.

Plasmonic Switching of the Reaction Pathway: Visible-Light Irradiation Varies the Reactant Concentration at the Solid-Solution Interface of a Gold-Cobalt Catalyst.

Product selectivity of alkyne hydroamination over catalytic Au Co alloy nanoparticles (NPs) can be made switchable by a light-on/light-off process, yielding imine (cross-coupling product of aniline and alkyne) under visible-light irradiation, but 1,4-diphenylbutadiyne in the dark. The low-flux light irradiation concentrates aniline on the catalyst, accelerating the catalytic cross-coupling by several orders of magnitude even at a very low overall aniline concentrations (1.0×10  mol L ).

One-pot selective synthesis of azoxy compounds and imines via the photoredox reaction of nitroaromatic compounds and amines in water.

A facile one-pot two-stage photochemical synthesis of aromatic azoxy compounds and imines has been developed by coupling the selective reduction of nitroaromatic compounds with the selective oxidation of amines in an aqueous solution. In the first stage (light illumination, Ar atmosphere), the light excited nitroaromatic molecule abstract H from amine to form ArNOH and amine radical, which then form nitrosoaromatic, hydroxylamine and imine compounds. Water acts as a green solvent for the dispersion of the reactants and facilitates the formation of nitrosoaromatic and hydroxylamine intermediate compounds.

Photon Energy Threshold in Direct Photocatalysis with Metal Nanoparticles: Key Evidence from the Action Spectrum of the Reaction.

By investigating the action spectra (the relationship between the irradiation wavelength and apparent quantum efficiency of reactions under constant irradiance) of a number of reactions catalyzed by nanoparticles including plasmonic metals, nonplasmonic metals, and their alloys at near-ambient temperatures, we found that a photon energy threshold exists in each photocatalytic reaction; only photons with sufficient energy (e.g., higher than the energy level of the lowest unoccupied molecular orbitals) can initiate the reactions.

Silver and palladium alloy nanoparticle catalysts: reductive coupling of nitrobenzene through light irradiation.

Silver-palladium (Ag-Pd) alloy nanoparticles strongly absorb visible light and exhibit significantly higher photocatalytic activity compared to both pure palladium (Pd) and silver (Ag) nanoparticles. Photocatalysts of Ag-Pd alloy nanoparticles on ZrO and AlO supports are developed to catalyze the nitroaromatic coupling to the corresponding azo compounds under visible light irradiation. Ag-Pd alloy NP/ZrO exhibited the highest photocatalytic activity for nitrobenzene coupling to azobenzene (yield of ∼80% in 3 hours).

Viable photocatalysts under solar-spectrum irradiation: nonplasmonic metal nanoparticles.

Supported nanoparticles (NPs) of nonplasmonic transition metals (Pd, Pt, Rh, and Ir) are widely used as thermally activated catalysts for the synthesis of important organic compounds, but little is known about their photocatalytic capabilities. We discovered that irradiation with light can significantly enhance the intrinsic catalytic performance of these metal NPs at ambient temperatures for several types of reactions. These metal NPs strongly absorb the light mainly through interband electronic transitions.

Copper nanoparticles on graphene support: an efficient photocatalyst for coupling of nitroaromatics in visible light.

Copper is a low-cost plasmonic metal. Efficient photocatalysts of copper nanoparticles on graphene support are successfully developed for controllably catalyzing the coupling reactions of aromatic nitro compounds to the corresponding azoxy or azo compounds under visible-light irradiation. The coupling of nitrobenzene produces azoxybenzene with a yield of 90 % at 60 °C, but azobenzene with a yield of 96 % at 90 °C.

Coherent interfaces between crystals in nanocrystal composites.

Numerous materials are polycrystalline or consist with crystals of different phases. However, materials consisting of crystals on the nanometer scale (nanocrystals) are not simply aggregates of randomly oriented crystals as is generally regarded. We found, that in four different materials that consist of nanocrystals of two different phases and were obtained by different approaches, the nanocrystals of different phases are combined coherently forming interfaces with a close crystallographic registry between adjacent crystals (coherent interfaces).

Ceramic membranes for separation of proteins and DNA through in situ growth of alumina nanofibres inside porous substrates.

Ceramic membranes were fabricated by in situ synthesis of alumina nanofibres in the pores of an alumina support as a separation layer, and exhibited a high permeation selectivity for bovine serum albumin relative to bovine hemoglobin (over 60 times) and can effectively retain DNA molecules at high fluxes.

Titanate nanofibers as intelligent absorbents for the removal of radioactive ions from water.

Layered titanate nanofibers can absorb bivalent ions from waste water via an ion exchange process. The sorption induces a considerable deformation of the layered structure, thus trapping the cations in the fibers permanently. Therefore, the fibers are desirable sorbents for the removal of toxic, radioactive Ra(2+) and Sr(2+) ions from water and subsequent safe disposal thereof.

High-flux ceramic membranes with a nanomesh of metal oxide nanofibers.

Traditional ceramic separation membranes, which are fabricated by applying colloidal suspensions of metal hydroxides to porous supports, tend to suffer from pinholes and cracks that seriously affect their quality. Other intrinsic problems for these membranes include dramatic losses of flux when the pore sizes are reduced to enhance selectivity and dead-end pores that make no contribution to filtration. In this work, we propose a new strategy for addressing these problems by constructing a hierarchically structured separation layer on a porous substrate using large titanate nanofibers and smaller boehmite nanofibers.

Laponite-supported titania photocatalysts.

This study builds on previous results published on the synthesis and characterization of laponite-supported titania photocatalysts. Titania nanocrystals are prepared prior to addition to the clay dispersion, by a sol-gel synthesis incorporating a microwave hydrothermal step. In addition to previously examinations with XRD, TEM, and FT-IR, the samples are further characterized with SEM, 29Si NMR, and BET N2 sorption to gain additional insight into the effect of TiO2 concentration and surface area on the photoactivity of the samples.

Edge-modification of laponite with dimethyl-octylmethoxysilane.

This study examines the edge modification of laponite, with a monoalkoxy silane, dimethyl-octylmethoxysilane. The influence of ultrasonics, aging time and silane concentration on the resultant materials is examined. The silylated clays are characterized by XRD, IES, TGA, and Si NMR.

Synthesis and characterisation of clay-supported titania photocatalysts.

This study examines the use of laponite, a synthetic smectite, which forms exfoliated silicate layers when dispersed in water, as an inorganic support for titania nanocrystals. Titania nanocrystals are prepared prior to addition to the clay dispersion, by a sol-gel synthesis incorporating a microwave hydrothermal step. The characteristics of the resultant structure such as titania phase, crystallite size, and particulate size are examined via X-ray diffraction (XRD), transmission electron spectroscopy (TEM), and infrared spectroscopy.

Growth and surface properties of boehmite nanofibers and nanotubes at low temperatures using a hydrothermal synthesis route.

The growth of boehmite nanostructures at low temperature using a soft chemistry route with and without (PEO) surfactant is presented. Remarkably long boehmite 1D nanotubes/nanofibers were formed within a significantly short time by changing the reaction mechanism of aluminum hydroxide. By using the PEO surfactant as a templating agent, boehmite nanotubes up to 170 nm in length with internal and external diameters of 2-5 and 3-7 nm, respectively, were formed at 100 degrees C.

Synthesis, characterization, and surface properties of iron-doped boehmite nanofibers.

Iron-doped boehmite nanofibers with varying iron contents have been prepared at low temperatures using hydrothermal treatment in the presence of poly(ethylene oxide) surfactant. The resulting nanofibers were characterized by transmission electron microscopy (TEM), X-ray diffraction, energy-dispersive X-ray analysis, and N2 adsorption. TEM images showed that the resulting nanostructures are predominantly nanofibers when the doped iron content is less than 5% (mol/mol); in contrast, nanosheets were formed when iron doping was above 4%.

Quantitative information on pore size distribution from the tangents of comparison plots.

The comparison plot obtained from the nitrogen adsorption data has a similar shape to that of the curve of accumulating pore volume of a solid. The intrinsic nature of this relation is discussed. It is known that the derivatives of the accumulating pore volume with respect to the pore size are the pore size distribution (PSD) of the solid.