Dopamine polymer derived isolated single-atom site metals/N-doped porous carbon for benzene oxidation

Constructing Nitrogen-Coordinated Single Atom Catalysts via Bond-Plucking Strategy for Oxidation of Benzene

Single-atom catalysts (SACs) with nitrogen-coordinated active centers feature unique electronic and geometric structures and thus show high catalytic activity for various industrial reactions. Searching for operable synthesis protocols to accurately devise SACs is vital but remains challenging because commonly used high-temperature pyrolysis always causes unpredictable structural changes and inhomogeneous single-atom sites. Herein, a mild bond-plucking strategy is reported to construct atomically dispersed Cu supported on graphene-liked C3N4 (g-C3N4) under lower than 100 °C, and Cu foam is used as the source of metal. When g-C3N4 closely coats the surface of Cu foam, Cu0 atoms on Cu foam transfer electrons to nitrogen on g-C3N4 due to the strong Lewis acbase interaction, simultaneously forming Cuδ+ (0 < δ < 2) and Cu─N bonds. Subsequently, g-C3N4 nanosheets are exfoliated out from the surface of Cu foam, eventually obtaining a well-defined Cu single atoms/g-C3N4 (Cu SAs/g-C3N4) catalyst with atomically dispersed Cu-N3 moieties. Cu SAs/g-C3N4 serves as a highly effective and durable catalyst toward the oxidation of benzene to phenol at 60 °C, with a conversion of 65.1% and selectivity of 97.6% after 12 h. The findings pave a new way to construct well-defined SACs at low costs, promoting large-scale production and industrial application.

Recent Advances in Engineering Fe-N-C Catalysts for Oxygen Electrocatalysis in Zn-Air Batteries

Fe-N-C single-atom catalysts (SACs) have emerged as one of the most promising candidates for oxygen electrocatalysis due to their maximized atom utilization efficiency, high intrinsic activity, and strong metal-support interaction. Significant progress has been made in engineering Fe-N-C SACs for oxygen electrocatalysis in Zn-air batteries (ZABs). This review provides a comprehensive overview of the recent advancements in Fe-N-C SACs, with a special focus on effective engineering strategies, their performance in oxygen electrocatalysis, and their potential applications in ZABs. The review also discusses the key challenges and future directions in the development of Fe-N-C SACs for efficient and durable oxygen electrocatalysis in ZABs. This review aims to offer valuable insights into the current state of research in this field and to guide future efforts in the development of advanced oxygen electrocatalysts for ZABs.

Supported nano-sized precious metal catalysts for oxidation of catalytic volatile organic compounds

Volatile organic compounds (VOCs) are common contaminants found as indoor as well as outdoor pollutants, which can induce acute or chronic health hazards to the human physiological system. The catalytic oxidation method is widely considered as one of the effective methods for removing VOCs, and the development of highly effective catalysts is highly urgent for booming this interesting field. This review focuses on the recent progress of VOC oxidation catalyzed by supported nano-sized precious metal catalysts, and discusses the effects of metal composition, supports, size, and morphology on the catalytic activity. In addition, the roles played by both nano-sized precious metals and supports in enhancing the performance of catalytic VOCs are also systematically discussed, which will guide the further development of more advanced VOC catalysts.

Spherical porous iron-nitrogen-carbon nanozymes derived from a tannin coordination framework for the preparation of L-DOPA by emulating tyrosine hydroxylase

L-3,4-Dihydroxyphenylalanine (L-DOPA) is widely used in Parkinson's disease treatment and is therefore in high demand. Development of an efficient method for the production of L-DOPA is urgently required. Nanozymes emulating tyrosine hydroxylase have attracted enormous attention for biomimetic synthesis of L-DOPA, but suffered from heterogeneity. Herein, a spherical porous iron-nitrogen-carbon nanozyme was developed for production of L-DOPA. Tannic acid chelated with ferrous ions to form a tannin-iron coordination framework as a carbon precursor. Iron and nitrogen co-doped carbon nanospheres were assembled via an evaporation-induced self-assembly process using urea as a nitrogen source, F127 as a soft template, and formaldehyde as a crosslinker. The nanozyme was obtained after carbonization and acid etching. The nanozyme possessed a dispersive iron atom anchored in the Fe-N coordination structure as an active site to mimic the active center of tyrosine hydroxylase. The material showed spherical morphology, uniform size, high specific surface area, a mesoporous structure and easy magnetic separation. The structural properties could promote the density and accessibility of active sites and facilitate mass transport and electron transfer. The nanozyme exhibited high activity to catalyze the hydroxylation of tyrosine to L-DOPA as tyrosine hydroxylase in the presence of ascorbic acid and hydrogen peroxide. The titer of DOPA reached 1.2 mM. The nanozyme showed good reusability and comparable enzyme kinetics to tyrosine hydroxylase with a Michaelis-Menten constant of 2.3 mM. The major active species was the hydroxyl radical. Biomimetic simulation of tyrosine hydroxylase using a nanozyme with a fine structure provided a new route for the efficient production of L-DOPA.

A smartphone-based visual ratiometric fluoroprobe for rapid and sensitive detection hypochlorous acid based on dual-emission metal organic frameworks

Herein, we designed/developed a mixed fluorescence system with europium metal-organic framework (EDB) and zinc metal-organic framework (ZBNB). At the 270-nm excitation wavelength, the EDB-ZBNB dually emitted at 425 and 615 nm and displayed blue solution under 365-nm UV lamp. When HOCl was fortified, the 425-nm blue emission dropped progressively, while the 615-nm red emission was relatively stable. Upon addition of ClO-, the shortened fluorescence lifetime demonstrated that the quenched 425-nm fluorescence of ZBNB was owing to the occurrence of dynamic quenching effect. Besides, amino groups are protonated in water to form -NH3+, which interact with ClO- to form hydrogen bonds, reduce the distance between -NH3+ and ClO-, produce energy transfer and result in fluorescence quenching. The ratiometric fluoroprobe provided a significant color change from blue to red, making HOCl detection visual and rapid. This fluorescent probe overcome the disadvantage of conventional redox-based fluorescent probes that can be interfered by MnO4- and other oxidants with stronger oxidizing capacity than free ClO-. Furthermore, a smartphone-based portable sensing platform was developed based on EDB-ZBNB. By using a "Thingidentify" software on smartphone, the sensing platform was used to detect HOCl in waters with a low detection limit of 28.0 nM and the fortified recoveries of 98.87-103.60%. Thus, this study provides a novel and promising platform for the detection of free ClO- in monitoring water quality.

Regulating electron configuration of single Cu sites via unsaturated N,O-coordination for selective oxidation of benzene

Developing highly efficient catalyst for selective oxidation of benzene to phenol (SOBP) with low H2O2 consumption is highly desirable for practical application, but challenge remains. Herein, we report unique single-atom Cu1-N1O2 coordination-structure on N/C material (Cu-N1O2 SA/CN), prepared by water molecule-mediated pre-assembly-pyrolysis method, can efficiently boost SOBP reaction at a 2:1 of low H2O2/benzene molar ratio, showing 83.7% of high benzene conversion with 98.1% of phenol selectivity. The Cu1-N1O2 sites can provide a preponderant reaction pathway for SOBP reaction with less steps and lower energy barrier. As a result, it shows an unexpectedly higher turnover frequency (435 h−1) than that of Cu1-N2 (190 h−1), Cu1-N3 (90 h−1) and Cu nanoparticle (58 h−1) catalysts, respectively. This work provides a facile and efficient method for regulating the electron configuration of single-atom catalyst and generates a highly active and selective non-precious metal catalyst for industrial production of phenol through selective oxidation of benzene.

Copper single-atom catalysts with photothermal performance and enhanced nanozyme activity for bacteria-infected wound therapy

Nanozymes have become a new generation of antibiotics with exciting broad-spectrum antibacterial properties and negligible biological toxicity. However, their inherent low catalytic activity limits their antibacterial properties. Herein, Cu single-atom sites/N doped porous carbon (Cu SASs/NPC) is successfully constructed for photothermal-catalytic antibacterial treatment by a pyrolysis-etching-adsorption-pyrolysis (PEAP) strategy. Cu SASs/NPC have stronger peroxidase-like catalytic activity, glutathione (GSH)-depleting function, and photothermal property compared with non-Cu-doped NPC, indicating that Cu doping significantly improves the catalytic performance of nanozymes. Cu SASs/NPC can effectively induce peroxidase-like activity in the presence of H2O2, thereby generating a large amount of hydroxyl radicals (•OH), which have a certain killing effect on bacteria and make bacteria more susceptible to temperature. The introduction of near-infrared (NIR) light can generate hyperthermia to fight bacteria, and enhance the peroxidase-like catalytic activity, thereby generating additional •OH to destroy bacteria. Interestingly, Cu SASs/NPC can act as GSH peroxidase (GSH-Px)-like nanozymes, which can deplete GSH in bacteria, thereby significantly improving the sterilization effect. PTT-catalytic synergistic antibacterial strategy produces almost 100% antibacterial efficiency against Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA). In vivo experiments show a better PTT-catalytic synergistic therapeutic performance on MRSA-infected mouse wounds. Overall, our work highlights the wide antibacterial and anti-infective bio-applications of Cu single-atom-containing catalysts.

Recent Advances on Heteroatom-Doped Porous Carbon/Metal Materials: Fascinating Heterogeneous Catalysts for Organic Transformations

Design and preparation of low-cost, effective, and novel catalysts are important topics in the field of heterogeneous catalysis from academic and industrial perspectives. Recently, heteroatom-doped porous carbon/metal materials have received significant attention as promising catalysts in divergent organic reactions. Incorporation of heteroatom into the carbon framework can tailor the properties of carbon, providing suitable interaction between support and metal, resulting in superior catalytic performance compared with those of traditional pure carbon/metal catalytic systems. In this review, we try to underscore the recent advances in the design, preparation, and application of heteroatom-doped porous carbon/metal catalysts towards various organic transformations.

Carbon-Based Materials for the Development of Highly Dispersed Metal Catalysts: Towards Highly Performant Catalysts for Fine Chemical Synthesis

Single-atom catalysts (SACs), consisting of metals atomically dispersed on a support, are considered as advanced materials bridging homogeneous and heterogeneous catalysis, representing the catalysis at the limit. The enhanced performance of these catalysts is due to the combination of distinct factors such as well-defined active sites, comprising metal single atoms in different coordination environments also varying its valence state and strongly interacting with the support, in this case porous carbons, maximizing then the metal efficiency in comparison with other metal surfaces consisting of metal clusters and/or metal nanoparticles. The purpose of this review is to summarize the most recent advances in terms of both synthetic strategies of producing porous carbon-derived SACs but also its application to green synthesis of highly valuable compounds, an area in which the homogeneous catalysts are classically used. Porous carbon-derived SACs emerge as a type of new and eco-friendly catalysts with great potential. Different types of carbon forms, such as multi-wall carbon nanotubes (MWCNTs), graphene and graphitic carbon nitride or even others porous carbons derived from Metal–Organic-Frameworks (MOFs) are recognized. Although it represents an area of expansion, experimentally and theoretically, much more future efforts are needed to explore them in green fine chemical synthesis.

Modifications of heterogeneous photocatalysts for hydrocarbon C–H bond activation and selective conversion

This feature article summarizes the recent progress in the modification of heterogeneous photocatalysts for photocatalytic hydrocarbons’ C–H bond activation.