Iron-palladium supported graphene as an efficient bimetallic catalyst for the selective oxidation of benzyl alcohol to benzaldehyde

The catalytic oxidation of benzyl alcohol (OBA) is one of the significant methods to produce benzaldehyde, an essential reagent in the chemical and pharmaceutical industries. However, developing an active and efficient catalyst for OBA is a tremendous challenge in commercialization. This research describes a simple, eco-friendly method for producing Fe, Pd, and Fe: Pd bimetallic nanoparticles fabricated by sol immobilization over graphene to conduct OBA. The resulting composite nano-alloys were then characterized using X-ray diffraction (XRD), Fourier transforms infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The oxidation state and elemental composition of as-fabricated nanoparticles were analyzed using XPS. The point of zero charges (pH_PZC) was analyzed and the PZC value indicated that the proposed adsorbent material tends to have a positive charge. The OBA reaction efficiency (87%) of bimetallic nanocatalysts stabilized in graphene support was increased through surface modification of the ratio of both metals. The experimental error was based on three parallel tests and the carbon balance (99.6%) was analyzed during the experiments A proposed reaction mechanism of OBA validated the β-hydride step's elimination by molecular oxygen converting the metal hydride into a water molecule, forming a peroxide intermediate to form water and oxygen molecules. The Fe on the nanocatalyst’s surface is preferentially responsible for the adsorption of the substrate molecule, resulting in the formation of metal-alkoxide. Since it lacks electrons, Fe is more likely to be oxidized, allowing it to perform better than monometallic catalysts in terms of catalytic activity. The present study has great potential to be applied on an industrial scale and studied for industrialists, researchers, and academicians.     

Water Activation for Boosting Electrochemiluminescence

In conventional luminol electrochemiluminescence (ECL) systems, hydrogen peroxide and dissolved oxygen are employed as typical co-reactants to produce reactive oxygen species (ROS) for efficient ECL emission. However, the self-decomposition of hydrogen peroxide and limited solubility of oxygen in water inevitably restrict the detection accuracy and luminous efficiency of luminol ECL system. Inspired by ROS-mediated ECL mechanism, for the first time, we used cobalt-iron layered double hydroxide as co-reaction accelerator to efficiently activate water to generate ROS for enhancing luminol emission. Experimental investigations verify the formation of hydroxyl and superoxide radicals in the process of electrochemical water oxidation, which subsequently react with luminol anion radicals to trigger strong ECL signals. Finally, the detection of alkaline phosphatase has been successfully achieved with impressive sensitivity and reproducibility for practical sample analysis.     

Plasmonic Cu Nanoparticles for the Low-temperature Photo-driven Water-gas Shift Reaction

The activation of water molecules in thermal catalysis typically requires high temperatures, representing an obstacle to catalyst development for the low-temperature water-gas shift reaction (WGSR). Plasmonic photocatalysis allows activation of water at low temperatures through the generation of light-induced hot electrons. Herein, we report a layered double hydroxide-derived copper catalyst (LD-Cu) with outstanding performance for the low-temperature photo-driven WGSR. LD-Cu offered a lower activation energy for WGSR to H₂ under UV/Vis irradiation (1.4 W cm⁻²) compared to under dark conditions. Detailed experimental studies revealed that highly dispersed Cu nanoparticles created an abundance of hot electrons during light absorption, which promoted *H₂O dissociation and *H combination via a carboxyl pathway, leading to the efficient production of H₂. Results demonstrate the benefits of exploiting plasmonic phenomena in the development of photo-driven low-temperature WGSR catalysts.     

Inside Cover: Ligand Assisted Thermal Atomization of Palladium Clusters: An Inspiring Approach for the Rational Design of Atomically Dispersed Metal Catalysts (Angew. Chem. Int. Ed. 16/2023)

The transformation from metal nanocluster catalysts to metal single-atom catalysts is an important procedure in the rational design of atomically dispersed metal catalysts (ADCs). However, the conversion methods often involve high annealing temperature as well as reducing atmosphere. Herein, we reported a continuous and convenient approach to transfer Pd nanocluster into Pd single-atom in a ligand assisted annealing procedure, by which means we reduced its activating temperature low to 400 °C. Using ex-situ microscopy and spectroscopy, we comprehensively monitored the structural evolution of Pd species though the whole atomization process. Theoretical calculation revealed that the structural instability caused by remaining Cl ligands was the main reason for this low-temperature transformation. The present atomization strategy and mechanistic knowledge for the conversion from cluster to atomic dispersion provides guidelines for the rational design of ADCs.     

Dual-Atomic-Site Catalysts for Molecular Oxygen Activation in Heterogeneous Thermo-/Electro-catalysis

Efficient molecular oxygen activation (MOA) is the key to environmentally friendly catalytic oxidation reactions. In the last decade, single-atomic-site catalysts (SASCs) with nearly 100 % atomic utilization and unique electronic structure have been widely investigated for MOA. However, the single active site makes the activation effect unsatisfactory and difficult to deal with complex catalytic reactions. Recently, dual-atomic-site catalysts (DASCs) have provided a new idea for the effective activation of molecular oxygen (O₂) due to more diverse active sites and synergetic interactions among adjacent atoms. In this review, we systematically summarized the recent research progress of DASCs for MOA in heterogeneous thermo- and electrocatalysis. Finally, we look forward to the challenges and application prospects in the construction of DASCs for MOA.     

An approach utilizing the Response Surface Methodology (RSM) to optimize Adsorption-Desorption of Natural Saudi Arabian Diatomite- with the Box- Behnken Design Technique

Saudi Arabian’s natural diatomite samples were subjected to physical adsorption–desorption characterizations using Brunauer-Emmet-Teller (BET) and the Barrett-Joyner-Halenda (BJH), performed under heating of 140 °C for different periods of hours: 6, 12, 18, and 24 h, to create a central optimization design with surface areas and total pore distributions. Seventeen experimental runs resulted in the primary composite factor design. The surface response describes 100 % variability with a determination coefficient of 1, signifying the quadratic model with an expected correlation coefficient (R²) is satisfied with a standard deviation of 0.2322, demonstrating the high predictability of the model. Moreover, the RSM results have been validated using the t-test with the observed R² value and adjusted R². The model selected with higher F and p values showed<0.0001, which subsequently described the significance of the developed model. The independent components were explained with the help of 3D surface and contour plots that compare the heating time, elapsed time, pressure, and relative pressure against the dependent variable. The plots revealed that the adsorbed quantities well depended on heating time, elapsed time, pressure, relative pressure for isotherm, BET surface area, Langmuir surface area, and t-plot Micropore area.     

Observation and identification of the catalytically active species of bis(phenoxy-imine) group 4 transition metal complexes for olefin polymerization using 1H NMR spectroscopy

Solution structures of bis(phenoxy-imine) group 4 transition metal complexes (FI Catalysts) were investigated using ¹H NMR spectroscopy. At least two isomers exist in equilibrium for FI Catalysts precursors, bis[N-(3-tert-butylsalicylidene)anilinato]zirconium(IV) dichloride ( 1 ), and bis[N-(3,5-dicumylsalicylidene)anilinato]zirconium(IV) dichloride ( 2 ), while bis[N-(3-tert-butylsalicylidene)-2,3,4,5,6-pentafluoroanilinato]titanium(IV) dichloride ( 3 ) exhibits only one isomer under the conditions examined. Upon activation with MAO, all FI Catalysts ( 1-3 ) generate two species at ambient temperature judging from some key signals in the ¹H NMR. When temperature is raised (up to 75°C), one species ( 1a-3a ) converts irreversibly to the other species ( 1b-3b ). The resulting species, 1b-3b , are stereochemically rigid, in contrast to precursors 1 and 2 . Species 3b , derived from a living FI Catalyst, exhibited virtually no reactivity toward olefin insertion. The imine protons of species 1b-3b are temperature and solvent polarity sensitive. Two possibilities are proposed for the assignment of species 1b-3b, i) heterobinuclear complexes of group 4 metal and alkylaluminum with methyl and/or chlorine as bridging groups and ii) phenoxy-imine ligated aluminum complexes whose ligands are transferred from the group 4 metal. The latter is more probable from the separate synthesis of LAlMe₂ (L: phenoxy-imine ligand). When 3 was activated with MAO in the presence of olefins, a new imine signal was observed. This species ( 3c for ethylene and 3d for propylene) is thermally more robust than 3a toward transformation to 3b and assignable to the living propagating species.