Selective Oxidative Cleavage of Benzyl C-N Bond under Metal-Free Electrochemical Conditions

With the growing significance of green chemistry in organic synthesis, electrochemical oxidation has seen rapid development. Compounds undergo oxidation-reduction reactions through electron transfer at the electrode surface. This article proposes the use of electrochemical methods to achieve cleavage of the benzyl C-N bond. This method selectively oxidatively cleaves the C-N bond without the need for metal catalysts or external oxidants. Additionally, primary, secondary, and tertiary amines exhibit good adaptability under these conditions, utilizing water as the sole source of oxygen.

Innovative green oxidation of amines to imines under atmospheric oxygen

In recent years, the development of environmentally benign molecular construction methods has been of great importance, and especially, resource recycling, high atomic efficiency, and low environmental impact are in high demand. From this point of view, attention has also been focused on the development of one-pot synthesis of pharmaceuticals and functional molecules. Imines are excellent synthetic intermediates of these useful molecules, and the environmentally friendly oxidative synthesis of imines from amines has been energetically developed using oxygen (or air), which is abundantly available on the Earth, as an oxidant. This review focuses on the latest innovative and green oxidation systems of amines to imines under atmospheric oxygen, and their application to one-pot/eco-friendly and sustainable synthesis of pharmaceuticals and functional molecules. In particular, catalytic systems that activate molecular oxygen are categorized and described in detail as transition metal catalytic systems, photoirradiated catalytic systems, and organocatalytic systems.

Tipping Gold Nanobipyramids with Titania for the Use of Plasmonic Hotspots to Drive Amine Coupling

Designing plasmonic photocatalysts with spatially controlled catalytic sites is an effective strategy to boost the sunlight-driven chemical transformation efficiency through plasmonic enhancement. Herein, we describe a facile method for the synthesis of TiO₂-tipped Au nanobipyramids (NBPs) to give (Au NBP)/t-TiO₂ nanodumbbells. The surfactant cetyltrimethylammonium bromide concentration is the key factor in the construction of this type of unique nanostructure. The photocatalytic aerobic oxidative coupling of amines using the plasmonic photocatalysts with the dumbbell-like and core@shell structures indicates that the TiO₂-tipped ends for the photo-reduction and the exposed adjacent Au surface for the photo-oxidation on (Au NBP)/t-TiO₂ can significantly improve the photocatalytic activity. The underlying mechanism of the photocatalytic oxidative coupling of benzylamine over (Au NBP)/t-TiO₂ has been thoroughly investigated. Both experimental and simulation results for (Au NBP)/t-TiO₂ and (Au nanorod)/t-TiO₂ confirm the important effect of the plasmonic hotspots on the enhancement of the photocatalytic activity.

Recent advances in Cu2O-based composites for photocatalysis: a review

Cu₂O-based composites for photocatalysis have been extensively explored owing to their promising application in solving environmental and energy problems. At present, the research on photocatalysis is focused on improving the photocatalytic performance of materials. It has been reported that adjusting the morphology and size of Cu₂O can effectively improve its photocatalytic property. However, photocorrosion is still an inevitable problem, which hinders the application of Cu₂O in photocatalysis. The strategies of constructing heterogeneous nanostructures and ion doping can significantly improve the light stability, light absorption capacity and separation efficiency of electron-hole pairs. Cu₂O-based composites exhibit superior performances in degrading organic matter, producing hydrogen, reducing CO₂ and sterilization. Therefore, the construction of multi-materials will be one of the future directions in their photocatalytic application. This review summarizes the recent strategies for enhancing the photocatalytic activity of Cu₂O by analyzing different Cu₂O-based photocatalysts, and the charge transfer pathway is further discussed in detail. Finally, several opportunities and challenges in the field of photocatalysis are illustrated.

Selectivity control of organic chemical synthesis over plasmonic metal-based photocatalysts

The factors, issues, and design of plasmonic metal-based photocatalysts for selective photosynthesis of organic chemicals have been discussed.

Z-scheme BiVO4/Ag/Ag2S composites with enhanced photocatalytic efficiency under visible light

The Z-scheme BiVO4/Ag/Ag2S photocatalyst was fabricated via a two-step route. The as-prepared samples were characterized by XRD, FE-SEM, HRTEM, XPS and UV-vis diffuse reflectance spectroscopy. The results of PL and photocurrent response tests demonstrate that the ternary BiVO4/Ag/Ag2S composites had a high separation and migration efficiency of photoexcited carriers. As a result, the ternary photocatalyst exhibits enhanced photocatalytic activity for decomposing Rhodamine B (RhB) under LED light (420 nm) irradiation. The results of trapping experiments demonstrate both h+ and ˙OH play crucial roles in decomposing RhB molecules. Additionally, the energy band structures and density of states (DOS) of BiVO4 and Ag2S were investigated via the density functional theory (DFT) method. Finally, a Z-scheme electron migration mechanism of BiVO4 → Ag → Ag2S was proposed based on the experimental and calculated results.

Surface defect-rich g-C3N4/TiO2 Z-scheme heterojunction for efficient photocatalytic antibiotic removal: rational regulation of free radicals and photocatalytic mechanism

Surface defect engineering was employed to introduce two different surface defect structures (i.e., nitrogen vacancies on g-C₃N₄ and oxygen vacancies on TiO₂) on the surface of g-C₃N₄/TiO₂ for efficient photocatalytic antibiotic removal.

Tuning effect of amorphous Fe2O3 on Mn3O4 for efficient atom-economic synthesis of imines at low temperature: improving [O] transfer cycle of Mn3+/Mn2+ in Mn3O4

A novel Fe₂O₃ modified Mn₃O₄ catalyst (Fe₅Mn₅-100) has been prepared by adopting a simple co-precipitation method following low temperature baking. Fe₅Mn₅-100 showed exceptionally high catalytic activity for the production of imine.

Core-Shell Type Semiconducting Heterostructures for Visible Light Photocatalysis

This personal account highlights a part of the work done over the years in our group towards directed synthesis of morphologically controlled nanostructures. We begin with our efforts on the synthesis of families of nanostructured metal oxides and metal oxalates of well-defined morphology using low temperature microemulsion and hydrothermal techniques. The parameters that govern the morphology in these syntheses e. g. choice of solvent and temperature are described. We then discuss nanostructures with core-shell architecture and specifically their utilization to harvest visible light for photocatalysis and photoelectrochemical applications. The techniques described to utilize visible light include sensitizing wide bandgap semiconductors using 1) appropriate narrow bandgap materials and 2) metals that have surface plasmon resonance active bands. The reports are classified according to morphology with spherical, cubes and rods discussed in separate sections. A discussion of recent reports by other groups on core-shell structures of similar composition as well as future directions and perspectives are presented at the end.

Atomic-Scale Observation of Bimetallic Au-CuOx Nanoparticles and Their Interfaces for Activation of CO Molecules

Supported gold nanoparticles with sizes below 5 nm display attractive catalytic activities for heterogeneous reactions, particularly those promoted by secondary metal (e.g., Cu) because of the well-defined synergy between metal compositions. However, the specific atomic structure at interfaces is less interpreted systematically. In this work, various bimetallic Au-CuO_x catalysts with specific surface structures were synthesized and explored by aberration-corrected scanning transmission electron microscopy (AC-STEM), temperature-programmed experiments and in situ DRIFT experiments. Results suggest that the atomic structure and interfaces between gold and CuO_x are determined by the nucleation behaviors of the nanoparticles and result in subsequently the distinctive ability for CO activation. Bimetallic CuO*/Au sample formatted by gold particles surrounded with CuO_x nanoclusters have rough surface with prominently exposed low-coordinated Au step defects. Whereas the bimetallic Au@CuO sample formatted by copper precursor in the presence of gold nanoparticles have core-shell structure with relatively smooth surface. The former structure of CuO*/Au displays much accelerated properties for CO adsorption and activation with 90% CO converted to CO₂ at 90 °C and nice stability with time on stream. The results clearly determine from atomic scale the significance of exposed gold step sites and intrinsic formation of defected surface by different nucleation. The above properties are directly responsible for the induced variation in chemical composition and the catalytic activity.

One-pot synthesis of Pd-promoted Ce–Ni mixed oxides as efficient catalysts for imine production from the direct N-alkylation of amine with alcohol

Pd-promoted CeNi_XO_Y mixed oxides showed high production of imines through the oxidative coupling of amines with alcohols due to the synergistic effect between Pd⁰ species and redox properties of CeNi_XO_Y.

One-pot fabrication of a double Z-scheme CeCO3OH/g-C3N4/CeO2 photocatalyst for nitrogen fixation under solar irradiation

A ternary photocatalyst CeCO₃OH/g-C₃N₄/CeO₂ was synthesized by an in situ self-sacrificing method, and its N₂ photofixation performance was investigated.

Construction of a 0D/1D composite based on Au nanoparticles/CuBi2O4 microrods for efficient visible-light-driven photocatalytic activity

Photocatalysis is considered to be a promising technique for the degradation of organic pollutants. Herein, a 0D/1D composite photocatalyst consisting of Au nanoparticles (NPs) and CuBi₂O₄ microrods (Au/CBO) was designed and prepared by a simple thermal reduction-precipitation approach. It shows excellent photocatalytic performance in the degradation of tetracycline (TC). The maximum photocatalytic degradation rate constant for Au/CBO composites with 2.5 wt % Au NPs was 4.76 times as high as that of bare CBO microrods. Additionally, the 0D/1D Au/CBO composite also exhibited ideal stability. The significant improvement of the photocatalytic performance could be attributed to the improved light harvesting and increased specific surface area, enhancing photoresponse and providing more active sites. Our work shows a possible design of efficient photocatalysts for environmental remediation.