Catalytic Activation Research Articles

Plastic wastes-derived N-doped carbon nanotubes for efficient removal of sulfamethoxazole in high salinity wastewater via nonradical peroxymonosulfate activation

Peroxymonosulfate (PMS) catalytic activation is effective to eliminate organic pollutants from water, thus the development of low-cost and efficient catalysts is significant in applications. The resource conversion of plastic wastes (PWs) into carbon nanotubes (CNTs) is a promising candidate for PMS-based advanced oxidation processes (AOPs), and also a sustainable strategy to realize plastic management and reutilization. Herein, cost-effective PWs-derived N-doped CNTs (N-pCNTs) were synthesized, which displayed efficient activity for PMS activation through an electron transfer pathway (ETP) for sulfamethoxazole (SMX) degradation in high salinity water. The pyrrolic N induced the positively charged surface of N-pCNTs, favoring the electrostatic adsorption of PMS and subsequent generation of active PMS* . A galvanic oxidation process was developed to prove the electron-shuttle dominated ETP for SMX oxidation. Combined with theoretical calculations, the efficiency of ETP was determined by the potential difference between HOMO of SMX and LUMO of N-pCNTs. Such oxidation produced low-toxicity intermediates and resulted in selective degradation of specific sulfonamide antibiotics. This work reveals the feasibility of low-cost N-pCNTs catalysts from PWs serving as an appealing candidate for PMS-AOPs in water remediation, providing a new solution to alleviate environmental issues caused by PWs and also advances the understanding of ETP during PMS activation.

Labile oxygen-driven catalytic ozonation via surface peroxide pathway for efficient wastewater treatment

The aluminosilicate-based heterogeneous catalysts hold great promise for industrial catalytic ozonation; however, the lack of exploration into novel active sites and mechanism studies has impeded their development. In this work, we demonstrate that labile oxygen (Olab) can be generated in mullite (mullite-Olab) by the introduction of extra Al-O4 tetrahedral units. In our experiments, mullite-Olab exhibits excellent performance in terms of catalytic ozone activation, with a degradation rate of 87.4 % within 15 min for nonbiodegradable atrazine, corresponding to a high quasi-first-order rate constant (k, 0.112 min−1), while the degradation constant is close to 0 for mullite without Olab. Operando Raman and density functional theory (DFT) simulations further reveal that Olab activates ozone via a novel surface peroxide pathway to generate surface Olab-O* species with a high oxidizing ability. The mullite-Olab is stable with an average Al3+ leaching of 0.339 ppm during cycling, meeting the effluent discharge standard of the total Al. Moreover, we achieve the kilogram synthesis of mullite-Olab, which shows promising activity in the catalytic ozonation of acrylic fiber wastewater, with the chemical oxygen demand (COD) and total organic carbon (TOC) removal rates of 46.0 %±4.8 % and 24.9 %±2.8 % for 5 cycles. This work is the first to demonstrate the role of Olab in ozone activation and provides an advanced mullite-Olab catalyst for future nonbiodegradable wastewater treatment.

Effect of log Kow on the degradation of pharmaceutically active compounds in a heterogeneous catalytic persulfate activation system

In heterogeneous catalytic advanced oxidation processes (HC-AOP), enhancing the reaction rate is the biggest challenge. To enhance the reaction rate, it is necessary to increase the mass transfer rate of reactants toward the catalyst surface and the number of active sites that will provide better contact with the reactants and higher mass transfer. The hydrophobicity of the reactant is an important parameter that affects the transport of molecules toward solid surfaces. In this study, the effect of log Kow, an indicator of hydrophobicity, on enhancing the catalytic activity in persulfate (PS) activation for pharmaceutic compounds (PCs) degradation was investigated. For this purpose, some PCs with different log Kow were selected and their adsorption and degradation behaviors were investigated depending on the PS concentration, catalyst dosage, contact time, pH, and temperature in HC-AOP. Adsorption percentages increased significantly with increasing log Kow value. PCs with higher log Kow were completely degraded at the end of the shorter contact times in the presence of lower catalyst and PS. PCs were significantly degraded by the triple catalytic effect of AC, Fe, and temperature. The pseudo-first-order kinetic model was the best fit for the degradation reaction for all PCs. The higher apparent rate constants and lower activation energy values of the PCs belonging to high log Kow confirmed that log Kow is an effective parameter in enhancing the catalytic activity.

Novel Fe3O4@TiO2 core–shell nanostructure catalyst for NO removal through heterogeneous Fenton processes

Diverse Fe3O4@TiO2 catalysts, featuring a range of core-shell ratios, were employed within an H2O2 catalytic activation system to facilitate the oxidation of NO. These catalysts underwent comprehensive structural characterization, including XRD, TEM, BET, XPS, VSM and TPR analysis. Experimental investigations were conducted with the specific goal of assessing the catalytic efficiency of Fe3O4@TiO2 core-shell catalysts and Fe3O4/TiO2 supported catalysts in the contexts of desulfurization and denitrification. The results demonstrated that catalysts featuring a core-shell ratio of 1:2 exhibited the highest catalytic efficiency. Moreover, the core-shell catalysts outperformed their supported counterparts with the same molar ratio in terms of physicochemical properties, removal efficiency, and stability. Notably, the core-shell catalysts possessed exceptionally favorable pore structures and substantial specific surface areas, facilitating enhanced H2O2 activation for NO oxidation through synergistic interactions between the core and shell components. This research holds the potential to guide future endeavors in the development of catalysts aimed at achieving superior H2O2 catalytic efficiency.

Substrate selectivity and catalytic activation of the type III CRISPR ancillary nuclease Can2.

Type III CRISPR-Cas systems provide adaptive immunity against foreign mobile genetic elements through RNA-guided interference. Sequence-specific recognition of RNA targets by the type III effector complex triggers the generation of cyclic oligoadenylate (cOA) second messengers that activate ancillary effector proteins, thus reinforcing the host immune response. The ancillary nuclease Can2 is activated by cyclic tetra-AMP (cA4); however, the mechanisms underlying cA4-mediated activation and substrate selectivity remain elusive. Here we report crystal structures of Thermoanaerobacter brockii Can2 (TbrCan2) in substrate- and product-bound complexes. We show that TbrCan2 is a single strand-selective DNase and RNase that binds substrates via a conserved SxTTS active site motif, and reveal molecular interactions underpinning its sequence preference for CA dinucleotides. Furthermore, we identify a molecular interaction relay linking the cA4 binding site and the nuclease catalytic site to enable divalent metal cation coordination and catalytic activation. These findings provide key insights into the molecular mechanisms of Can2 nucleases in type III CRISPR-Cas immunity and may guide their technological development for nucleic acid detection applications.

Structural insights into the activation mechanism of phosphoinositide 3-kinase alpha

Phosphoinositide 3-kinases (PI3Ks) are lipid kinases known to regulate important cellular functions by phosphorylating the inositol ring of inositol-phospholipids (PtdIns) at 3’ position. The PI3Kα is a heterodimer and the activation of the catalytic subunit (p110α) is regulated by its regulatory subunit (p85α). The current work deals with studying the activation mechanism of the PI3Kα using multi micro-second molecular dynamic simulations. Structural changes involved in activation mechanism is studied by gradually releasing the inhibitory effects of different domains of regulatory subunit namely, n-terminal SH2 (nSH2) and inter SH2 (iSH2). The observation shows that even in the presence of n-terminal and inter SH2 domain (niSH2) of regulatory subunit, the catalytic domain has some intrinsic activation activity and the presence of c-terminal SH2 (cSH2) domain may be required for complete inhibition. The release of nSH2 domain leads to loss of interactions between iSH2 domain (regulatory subunit) and C2 and kinase domain (catalytic subunit). The study shows that early events in the activation mechanism involve the movement of the ABD domain of the catalytic subunit along with the linker region between ABD and RBD region which may lead to movement of ABD closer to the CLobe of the kinase domain. This movement is essentially as it triggers the rearrangement of CLobe especially the catalytic loop and activation loop which bring catalytic important residues closer to ATP and PIP2(phosphatidylinositol-4,5-bisphosphate). Water mediated interaction analysis reveal that water may be playing an important role in the transfer of phosphate from ATP to PIP2. The study shows that initial signal for release of inhibitory effect of the regulatory subunit might be propagated through the linker region between ABD and RBD through allosteric effect to different regions of the protein. These understanding of early events during the activation mechanism may help in the design of better therapeutic targeting PI3K.

Biochar-Based Single-Atom Catalyst with Fe-N3O-C Configuration for Efficient Degradation of Organic Dyes by Peroxymonosulfate Activation.

Iron single-atom catalysts (Fe SACs) hold great promise for peroxymonosulfate (PMS) activation and degradation of organic pollutants in wastewater. However, insights into crucial catalytic sites and activation mechanisms of biochar-based Fe SACs for PMS remain a challenge. Herein, cotton stalk-derived biochar-based Fe SACs (Fe SACs-BC) with an asymmetric Fe-N/O-C configuration were prepared, and their PMS activation and acid orange 7 (AO7) degradation mechanisms were investigated. The results showed that the removal efficiency of the Fe SACs-BC catalyst with Fe-N3O-C configuration for AO7 and other five investigated organic dyes reached 95-99% within 15 min. The EPR spectrums, quenching experiments, electrochemical analysis, masking experiments, XPS, and theoretical calculations indicated that degradations of organic dyes were dominated by singlet oxygen, which was generated by direct PMS conversion at the electron-deficient carbon and iron sites in the Fe-N3O-C configuration. The Fe SACs-BC/PMS exhibited high removal efficiency and strong tolerance in different water matrices with a wide pH range, various coexisting anions and interfering substances, showing great potential and applicability for efficient treatment of actual textile wastewaters.

Degradation of roxarsone and simultaneous immobilization of inorganic arsenic by L-cys modified FeMnNi-LDH activated persulfate system

A series of novel L-cysteine (L-cys) modified iron-manganic-nickel hydrotalcite (L-cys-LDH) were synthesized and used for heterogeneous catalytic activation of monopersulfate (PMS) to degrade roxarsone (ROX) and adsorption of released inorganic arsenic. The catalyst was characterized by TEM, XRD, FTIR, XPS, and other characterization techniques to analyze its structure and functional properties. The degradation experiment results showed that the activity of the catalyst was effectively improved after L-cys loading on LDH. In the pH range of 3–9, 0.2 g/L L-cys-LDH and 0.2 mM PMS could degrade more than 90 % of ROX in 20 min, three times higher than that of ordinary FeMnNi-LDH. Besides, the residual amount of inorganic arsenic in the solution was less than 0.01 mg/L. The electron paramagnetic resonance (EPR) test and quenching investigation identified surface-bound SO4-· and surface-bound ·OH as the main contributors to organic degradation. Mechanism studies have shown that cysteine embedded in LDH accelerated the conversion rate of Fe(III)/Mn(III) to Fe(II)/Mn(II) by self-oxidation to cystine, thereby improving the efficiency of catalyst activation of PMS. In addition, the main degradation products were obtained by LC-MS analysis, and the possible pathway of ROX degradation was given in L-cys-LDH/PMS system combined with DFT theoretical calculation. The work showed that L-cys-LDH exhibited excellent catalytic performance and inorganic arsenic adsorption capacity. It provides an idea for the improvement of hydrotalcite-based catalysts. It also sheds some light on the degrade of novel hydrotalcite-based catalysts for the one step degradation and adsorption of ROX.

Insights on the Anion Effect in N-heterocyclic Carbene Based Dinuclear Gold(I) Catalysts.

Dinuclear bisNHC (bis(N-heterocyclic carbene)) gold(I) complexes 3 a and 4 a of general formula [Au2 Br2 (bisNHC)] were tested as catalysts in the cycloisomerization of N-(prop-2-yn-1-yl)benzamide and in the hydromethoxylation of 3-hexyne in the presence of silver(I) activators bearing different counteranions. The catalytic performance of mononuclear NHC complexes (1 a, 2 a) in the same reactions was also studied. The results highlighted the fundamental role of both NHC ligand and counterion in the catalytic cycles and activation process: dinuclear catalysts exhibit higher initial activity even under milder conditions but suffer in terms of stability with respect to mono NHCs. Furthermore, a new dinuclear bisNHC gold(I) complex 4 b of general formula [Au2 (OTs)2 (bisNHC)] (OTs=p-toluenesulfonate) was successfully synthesized and characterized by means of NMR and ESI-MS analyses.

Evaluation of a Bidentate ‘Clamp-Like’ Halogen-Bond Donor Motif Based on Iodonium(III) Moieties

AbstractA new motif for iodine(III)-based halogen-bond donors consisting of a 1,3-phenylene core and two cyclic five-membered diaryliodonium(III) wings was designed and its potential as a catalyst was evaluated. Its properties were analyzed in the solid state by X-ray crystallography and in solution by benchmark catalytic activation of a nitro-Michael addition between 5-methoxyindole and trans-β-nitrostyrene.

Electrochemical interfacial catalysis in Co-based battery electrodes involving spin-polarized electron transfer.

Interfacial catalysis occurs ubiquitously in electrochemical systems, such as batteries, fuel cells, and photocatalytic devices. Frequently, in such a system, the electrode material evolves dynamically at different operating voltages, and this electrochemically driven transformation usually dictates the catalytic reactivity of the material and ultimately the electrochemical performance of the device. Despite the importance of the process, comprehension of the underlying structural and compositional evolutions of the electrode material with direct visualization and quantification is still a significant challenge. In this work, we demonstrate a protocol for studying the dynamic evolution of the electrode material under electrochemical processes by integrating microscopic and spectroscopic analyses, operando magnetometry techniques, and density functional theory calculations. The presented methodology provides a real-time picture of the chemical, physical, and electronic structures of the material and its link to the electrochemical performance. Using Co(OH)2 as a prototype battery electrode and by monitoring the Co metal center under different applied voltages, we show that before a well-known catalytic reaction proceeds, an interfacial storage process occurs at the metallic Co nanoparticles/LiOH interface due to injection of spin-polarized electrons. Subsequently, the metallic Co nanoparticles act as catalytic activation centers and promote LiOH decomposition by transferring these interfacially residing electrons. Most intriguingly, at the LiOH decomposition potential, electronic structure of the metallic Co nanoparticles involving spin-polarized electrons transfer has been shown to exhibit a dynamic variation. This work illustrates a viable approach to access key information inside interfacial catalytic processes and provides useful insights in controlling complex interfaces for wide-ranging electrochemical systems.

BaTiO3-xNy: Highly Basic Oxide Catalyst Exhibiting Coupling of Electrons at Oxygen Vacancies with Substituted Nitride Ions.

The base strength of oxide catalysts is controlled by the electron charge distribution between cations and anions, with unsaturated oxygen ions that have lone pair electrons typically acting as basic sites. Substitution of oxide ions with anions that have different valences, such as nitride and hydride ions, can often generate basic sites. It is plausible that electrons trapped at oxygen vacancy sites could provide increased electron density and shift the highest occupied molecular orbital energy levels of anions upward in the case that the oxygen vacancies couple with surface-substituted anions. The present work demonstrates that high catalytic basicity can be obtained via site-selective doping of anions at face-sharing Ti2O9 dimer sites with oxygen vacancies in BaTiO3-x. This improved basicity stems from the coupling of substituted nitride ions to electrons at oxygen vacancies. The oxynitride BaTiO3-xNy was found to contain nitride ions that have increased electronic charge density on the basis of such interactions. Enhanced surface basicity following doping with nitride ion was also confirmed by CO2 temperature-programmed desorption and infrared spectroscopy in conjunction with the adsorption of CHCl3. The strong Lewis base sites resulting from the formation of the oxynitride evidently facilitated the catalytic activation of C-H bonds to promote Knoevenagel condensation reactions between aldehydes and active methylene compounds with pKa values of up to 28.9.

Effect of rGO content on enhanced Photo-Fenton degradation of Venlafaxine using rGO encapsulated magnetic hexagonal FeTiO3 nanosheets

In this work, we synthesized magnetic reduced graphene oxide (rGO) encapsulated hexagonal FeTiO3 (FTO@rGO) nanosheets with rGO loading amount of 0, 1, 5 and 10 wt%, with a primary objective of efficiently degrading venlafaxine (VLF) through photo-Fenton processes across a wide pH range of 3–11. The inherent visible-light photocatalytic ability of ilmenite FeTiO3 (FTO) and catalytic activation of H2O2 by Fe sites during the photo-Fenton process were established. Through the strategic integration of rGO, all FTO@rGO catalysts show higher VLF degradation rate than FTO in photo-Fenton evolution experiments and the FTO@rGO catalysts with rGO loading amount of 5 wt% presents the highest VLF degradation rate (100 % VLF degradation at 90 min), which attributed to the accelerated migration of photo-generated electrons and the efficient Fe2+/Fe3+ cycle. Furthermore, the encapsulation of rGO significantly mitigated Fe leaching throughout the reaction pH range, directing H2O2 activation to occur at the FTO@rGO interface instead of in solution. Through a comprehensive analysis, we identified 47 intermediate products of VLF and deduced the degradation pathway based on 12 representative intermediates. The degradation process was primarily driven by hydroxyl radicals as the dominant reactive oxygen species, complemented by the contribution of superoxide radicals, photogenerated electrons, and holes during the FTO@rGO-catalyzed photo-Fenton process. This study not only expands the application of ilmenite in the realm of advanced oxidation processes (AOPs) but also provides valuable insights for the future exploration and development of metal oxide/carbonaceous heterostructure catalysts.

Ultrasound-amplified polymetallic nanozyme-induced pyroptosis for lung cancer theranostics

For catalytic nanozyme and biomaterials in disease treatment, the iron-based catalysts suffer from low •OH generation performance due to the creation of a passive Fe (III) oxide layer and the prevention of the catalytic activation of H2O2 as a result of the oxidation of Fe (II) to Fe (III). Herein, polymetallic Cu0.5Mn0.5Fe2O4 (CMF) nanozyme has been rationally designed and engineered for massive generation of •OH through stabilizing the surface ferric species and providing enormous catalytically active sites. Furthermore, such a nanozyme with multienzyme-mimicking activities can amplify the reactive oxygen species production, elevate the oxidative stress level and induce cell pyroptosis. Importantly, exogenous ultrasound irradiation further achieves the goal of amplified and precise therapeutic effect again lung cancer. The in vitro and in vivo anti-tumor theranostic results confirm the accurate T1-T2 dual-mode magnetic resonance imaging and emphatic tumor inhibition effect of ultrasound-amplified CMF nanozymes. These results provide the paradigm of the utilization of polymetallic nanozymes as a therapeutic nanoplatform in treating apoptosis-resistant and pyroptosis sensitive tumors.

In-situ construction of MoC quantum dots embedded in n-doped 2D nanocarbon as a multifunctional host for high-performance lithium sulfide cathode

Lithium–ion batteries using Li2S cathode are considered as an optimal alternative for current lithium–ion batteries since their high theoretical capacity (1166 mAh/g) and high energy density (2600 W h kg−1). However, low electronic/ionic conductivity, severe lithium polysulfides (LiPSs) shuttle, and sluggish electrochemical reaction kinetics are the three major challenges for the practical application of Li2S. Herein, we report a multifunctional host of MoC quantum dots embedded in N–doped 2D nanocarbon (MoC@2D–NNC) with high electronic/ionic conductivity, strong LiPSs capture ability and superior electrochemistry catalytic activation for Li2S electrode. Nano Li2S is successfully entered into the MoC@2D–NNC to form MoC@2D–NNC/Li2S composite via facile liquid–phase dissolution precipitation. The obtained MoC@2D–NNC/Li2S composite displays a high electronic conductivity of 0.1624 S cm−1, high initial discharge capacity of 1059 mAh/g, and long–term cycling performance over 1000 cycles. This reported MoC@2D–NNC/Li2S composite exhibits promising applications in advanced Li–S batteries.

Screening for the adsorption-activated H2O2 and peroxymonosulfate for high-performance heteroatom-doped graphene: Molecular dynamics simulation and DFT

As an green and efficient metal-free catalyst, heteroatom-doped graphene has gradually become a research topic in the catalytic field, but the active sites and mechanisms of the catalytic reactions are still not thorough enough. In this paper, the adsorption-activation properties of two activated molecules, H2O2 and peroxymonosulfate (PMS), on graphene (GR) and heteroatom (N, P, B, Si, F) doped graphene were investigated by means of computational methods. Molecular dynamics (MD) simulation results showed that the adsorption activation process of activated molecules on the surface of the six catalysts occurs in their first adsorption layer, in which B-doped graphene (BGR) has better catalytic activation performance for H2O2, while N-doped graphene (NGR) has better catalytic activation performance for PMS. Density function theory (DFT) revealed that the lowest molecular orbital gap of H2O2 at -BCO2 (0.691 eV), PMS at -NC2 has the lowest gap (0.432 eV). It is inferred that -BCO2 and -NC2 functional groups are the main functional regions of H2O2 activation by BGR and PMS activation by NGR, respectively. This work provides useful guidance for the design and optimization of high-performance metal-free catalysts, and the realization of green remediation for wastewater in the electrocatalytic oxidation process.

Catalytic activation of peracetic acid for pelargonic acid vanillylamide degradation by Co3O4 nanoparticles in-situ anchored carbon-coated MXene nanosheets: Performance and mechanism insight

Pelargonic acid vanillylamide (PAVA), a capsaicin-type dacryagogue agent utilized for counter-terrorism and riot control, possesses a low stimulus threshold. This characteristic can lead to environmental contamination following its application and may easily result in secondary stimulation to personnel. Cobalt-doped Ti3C2-MXene nanosheets (Co3O4/Ti3C2@C) were synthesized for the purpose of activating peracetic acid (PAA) and degrading PAVA. A carbon layer was coated on the surface of Ti3C2-MXene nanosheets to address the challenge of poor oxygen resistance in MXenes, thus preventing a significant decline in surface reactivity. The BET surface area of Co3O4/Ti3C2@C was expanded to 149.6 m2/g, significantly exceeding that of Ti3C2 (13.0 m2/g) and Co3O4 (56.4 m2/g). With 0.5 mg/mL of Co3O4/Ti3C2@C and 0.35 mM of PAA, 100 mg/L of PAVA was completely degraded within 60 min. The augmented BET surface area and the presence of more active sites confer remarkable PAA activation and catalytic degradation properties toward PAVA. Parameters such as initial pH, PAVA concentration, catalyst dosage, and PAA concentration on PAVA degradation were systematically assessed. Furthermore, the reusability and stability of the nanocomposite were substantiated through recycling tests. Radical quenching experiments and electron paramagnetic resonance analysis demonstrated the acetylperoxy radical (CH3CO3) as the primary species responsible for PAVA degradation. This research serves as an illustration of the utilization of MXene and transition metal activated PAA in wastewater treatment.

Nitrogen fixation as NOx using air plasma coupled with heterogeneous catalysis at atmospheric pressure

AbstractThis study presents insights into the use of activated catalysts to improve the energy efficiency of production in atmospheric pressure air plasma. The introduction of catalysts in the direct current glow discharge system reduces the energy cost of production by up to 45% at low gas flow rates. Notably, even when positioned away from the plasma zone, the catalyst enhanced production, suggesting a significant role for the catalytic activation of downstream neutral species. The study also introduced a novel approach involving an air plasma jet infused with floating catalyst powder. This method significantly increased energy efficiency at higher discharge currents, with an associated energy cost of 2.9 MJ/mol for production.

Sulfur vacancies-induced electron delocalization effect of cobalt sulfide for enhanced catalytic activation of peracetic acid and norfloxacin degradation

Antibiotics have attracted widespread attention due to their potential risks to human health and environment. In this study, a heterogeneous advanced oxidation process (AOP) of peracetic acid (PAA) activation by cobalt material was developed to degrade a typical antibiotic, norfloxacin (NOR). Cobalt sulfide materials with sulfur vacancies (CoSx) were synthesized through a two-step hydrothermal process. The optimized material (CoSx-2) could efficiently activate PAA system, achieving 91.8% NOR degradation in 5 min. The Co(II)/Co(III) species in CoSx was key to activating PAA, as Co(II) initiated the reaction and Co(III) activation caused the production of CH3C(=O)OO• species. Moreover, the presence of sulfur vacancies (VS) led to the generation of hydroxyl radicals (•OH) and singlet oxygen (1O2) via chain reactions with CH3C(=O)OO•. Density functional theory (DFT) calculations reveal the contribution of VS to enhanced catalytic PAA activation, as the lower work function (5.76 eV), higher adsorption energy (-3.43 eV), bridge effect of delocalized electrons and shifted d-band center are achieved to reduce the energy barrier for electron transfer during catalytic reaction. In addition, DFT calculation on Fukui index further explains that 18 N and 21 N are reactive sites of NOR for electrophilic attack, leading to primary degradation pathways of C–N cleavage, defluorination, dealkylation and hydroxylation. This study gives a new perspective on the regulation of material structure for efficient activation of PAA and promotes the practical application of heterogenous PAA-based AOPs for emerging contaminants removal in water treatment process.

Advances of Single‐Atomic Cobalt Catalysts in Liquid‐Phase Selective Oxidative Reactions

Single‐atom catalysts (SACs) composed of atomically dispersed metal‐active sites embedded in supporting substrates are attracting increasing attention in liquid‐phase selective oxidation reactions with joint merits of both advanced catalytic efficiency and high stability. Co‐based SACs present superior performance in several model oxidative reactions against many other metals, thus they are recognized as a promising solution to the current high‐cost noble‐metal catalysts required for the synthesis of fine chemicals. In this review, the up‐to‐date research on the synthesized Co–SACs in selective oxidation applications is summarized. The strategies of the preparation of Co–SACs with diverse Co‐loading levels and well‐tuned morphologies and chemical structures are showcased, as well as the characterization techniques of the SACs. The applications of Co–SACs in a series of selective oxidation reactions and the influence of different oxidants on the overall reaction efficiency are discussed. In addition, the progress of the mechanism exploration involving active‐site identification, catalytic activation of oxidants, and oxidation pathway elucidation is highlighted. Meanwhile, the existing challenges and the future efforts for the development of the Co–SAC reaction system in selective oxidation processes are outlined.