Promoted selective oxidation of ethylbenzene in liquid phase achieved by hollow CeVO4 microspheres

Novel catalytic behavior of defective nanozymes with catalase-mimicking characteristics for the degradation of tetracycline

Although nanozymes have shown significant potential in wastewater treatment, enhancing their degradation performance remains challenging. Herein, a novel catalytic behavior was revealed for defective nanozymes with catalase-mimicking characteristics that efficiently degraded tetracycline (TC) in wastewater. Hydroxyl groups adsorbed on defect sites facilitated the in-situ formation of vacancies during catalysis, thereby replenishing active sites. Additionally, electron transfer considerably enhanced the catalytic reaction. Consequently, numerous reactive oxygen species (ROS) were generated through these processes and subsequent radical reactions. The defective nanozymes, with their unique catalytic behavior, proved effective for the catalytic degradation of TC. Experimental results demonstrate that •OH, •O2-, 1O2 and e- were the primary contributors to the degradation process. In real wastewater samples, the normalized degradation rate constant for defective nanozymes reached 26.0 min-1 g-1 L, exceeding those of other catalysts. This study reveals the new catalytic behavior of defective nanozymes and provides an effective advanced oxidation process for the degradation of organic pollutants.

Manipulation of Electronic Effect and Assembly Architecture to Invoke Oxidation of Ethylbenzene by Hierarchical Co3O4 Wreaths

A high-performance transition-metal oxide catalyst can be designed by appropriately integrating the concepts of morphology regulation and electronic structure modulation. In this work, hierarchical Co3O4 wreaths (CCW) enriched with oxygen vacancies (Ov) were facilely constructed for the selective oxidation of ethylbenzene (EB) to acetophenone (AP). Under the screened optimal reaction conditions, the CCW catalyst can offer a 79.1% conversion of EB (ri = 0.244 mol gcat-1 h-1) accompanied by a selectivity of 92.3% to AP. The good reaction performance can be attributed to the cooperation of defect engineering and architecture design, which can synergistically facilitate the EB oxidation performance by augmenting the intrinsic reactivity and accessibility of active sites. This work presents a reliable route to construct a high-performance transitional metal oxide catalyst via manipulation of electronic effect and assembly architecture for the selective oxidation of EB and beyond.

Coupled Interface and Oxygen-Defect Engineering in Co3O4/CoMoO4 Heterostructures toward Active Oxidation of Ethylbenzene

The catalytic oxidation of ethylbenzene (EB) is a promising route to produce acetophenone (AcPO). Unfortunately, it remains a great challenge to achieve the highly efficient oxidation of EB under solvent-free conditions using molecular oxygen as the sole oxidant. In this contribution, we present a facile strategy to construct hierarchical oxygen vacancy-rich Co3O4/CoMoO4 heterostructures (Vö-CCMO), which delivers a high yield value of 74.5% at 83.2% conversion of EB and selectivity of 89.6% to AcPO. Both experimental studies and theoretical calculations substantiate the important role of oxygen-defect engineering triggered by the modified chemistry environment at the interfaces between the biphasic phases, which contributes to the good catalytic performance. This work illustrates a promising paradigm for the exploit of advanced catalysts toward boosting EB oxidation reaction in a more practical way.

Cobalt Encapsulated in Nitrogen-Doped Graphite-like Shells as Efficient Catalyst for Selective Oxidation of Arylalkanes

Selective oxidation of ethylbenzene to acetophenne is an important process in both organic synthesis and fine chemicals diligence. The cobalt-based catalysts combined with nitrogen-doped carbon have received great attention in ethylbenzene (EB) oxidation. Here, a series of cobalt catalysts with metallic cobalt nanoparticles (NPs) encapsulated in nitrogen-doped graphite-like carbon shells (Co@NC) have been constructed through the one-pot pyrolysis method in the presence of different nitrogen-containing compounds (urea, dicyandiamide and melamine), and their catalytic performance in solvent-free oxidation of EB with tert-butyl hydrogen peroxide (TBHP) as an oxidant was investigated. Under optimized conditions, the UCo@NC (urea as nitrogen source) could afford 95.2% conversion of EB and 96.0% selectivity to acetophenone, and the substrate scalability was remarkable. Kinetics show that UCo@NC contributes to EB oxidation with an apparent activation energy of 32.3 kJ/mol. The synergistic effect between metallic cobalt NPs and nitrogen-doped graphite-like carbon layers was obviously observed and, especially, the graphitic N species plays a key role during the oxidation reaction. The structure-performance relationship illustrated that EB oxidation was a free radical reaction through 1-phenylethanol as an intermediate, and the possible reaction mechanistic has been proposed.

Beneficial Synergistic Intermetallic Effect in ZnCo2O4 for Enhancing the Limonene Oxidation Catalysis

Utilization of naturally occurring limonene from renewable biomass as a key starting material for the synthesis of valuable chemicals is a promising avenue to reduce both the dependence on nonrenewable fossil fuels and global CO2 emission. Herein, we report a highly active tremella-like ZnCo2O4 catalyst for the selective oxidation of limonene with molecular oxygen under mild reaction conditions. The developed ZnCo2O4 catalyst exhibits an appealing reaction performance with a limonene conversion of 93.5% (reaction rate of 0.0823 mmol gcat-1 h-1) and selectivity of 75.8% for 1,2-limonene oxide (LO), far outperforming the monometallic oxides of ZnO and Co3O4. Detained experimental characterizations and analyses manifest that the substitution of Zn into the Co3O4 framework can facilitate the formation of more unsaturated coordination sites and oxygen vacancies due to the modified chemical environment of Co atoms, inducing a beneficial synergistic intermetallic effect for the limonene oxidation catalysis.

Multi-Prismatic Hollow Cube CeVO4 with Adjustable Wall Thickness Directed towards Photocatalytic CO2 Reduction to CO

Ternary orthovanadate compounds have received increasing attention due to their broad light absorption and diverse crystal structure. However, their multi-assembled crystal morphologies are limited mainly due to their initially polyatomic VO₄ groups. In this study, multi-prismatic hollow cubic CeVO₄ microstructures were fabricated by a one-step solvothermal method without any organic agents. The increase in wall thickness is in accordance with the radial direction of the quadrangular prism. Moreover, the overdose of the V precursor is favorable for the formation of hollow micro-cubic CeVO₄, and the wall thickness changes from 200 to 700 nm. Furthermore, these CeVO₄ microstructures were applied to photocatalytic CO₂ reduction with a maximum CO generation rate of up to 78.12 μmol g^-1 h^-1 under visible light irradiation, which was several times higher than that of the other samples. This superior photocatalytic activity might be attributed to its good crystallinity and unique exposed interior structure. This study provides guidelines for the multi-assembled structure fabrication of ternary compounds and expands upon the exploration of the spatial structure of multivariate compounds.