A confined micro-reactor with a movable Fe3O4 core and a mesoporous TiO2 shell for a photocatalytic Fenton-like degradation of bisphenol A

Photocatalysis and Fenton process are two primary and promising advanced oxidation processes to degrade organic pollutants. However, the practical applications of single photocatalysis and Fenton process are still limited. Introducing one of them into another to form a combined photocatalytic Fenton-like system has shown great potential but still faces challenges in designing a well-tailored catalyst. Herein, a confined photocatalytic Fenton-like micro-reactor catalyst with a movable Fe₃O₄ core and a mesoporous TiO₂ shell has been constructed via a successive Stöber coating strategy, followed by an ultrasound assisted etching method. The resulting micro-reactor possesses well-defined yolk-shell structures with uniform mesopores (～4 nm), a large Brunauer-Emmett-Teller (BET) surface area (～166.7 m²/g), a high pore volume (～0.56 cm³/g) and a strong magnetization (～51 emu/g), as well as tunable reactor sizes (20?90 nm). When evaluated for degrading bisphenol A under solar light in the presence of peroxymonosulfate, the micro-reactor exhibits a superior catalytic degradation performance with a high magnetic separation efficiency and an excellent recycle ability. The outstanding performance can be attributed to its unique textual structure, which leads to a great synergistic effect from the photocatalytic and Fenton-like process. This study gives an important insight into the design and synthesis of an advanced micro-reactor for a combined advanced oxidation processes (AOPs).     

Turning the Inert Element Zinc into an Active Single-Atom Catalyst for Efficient Fenton-Like Chemistry

Amongst various Fenton-like single-atom catalysts (SACs), the zinc (Zn)-related SACs have been barely reported due to the fully occupied 3d¹⁰ configuration of Zn²⁺ being inactive for the Fenton-like reaction. Herein, the inert element Zn is turned into an active single-atom catalyst (SA−Zn−NC) for Fenton-like chemistry by forming an atomic Zn−N₄ coordination structure. The SA−Zn−NC shows admirable Fenton-like activity in organic pollutant remediation, including self-oxidation and catalytic degradation by superoxide radical (O₂⋅⁻) and singlet oxygen (¹O₂). Experimental and theoretical results unveiled that the single-atomic Zn−N₄ site with electron acquisition can transfer electrons donated by electron-rich pollutants and low-concentration PMS toward dissolved oxygen (DO) to actuate DO reduction into O₂⋅⁻ and successive conversion into ¹O₂. This work inspires an exploration of efficient and stable Fenton-like SACs for sustainable and resource-saving environmental applications.     

Generation of FeIV=O and its Contribution to Fenton-Like Reactions on a Single-Atom Iron−N−C Catalyst

Generating Fe^IV=O on single-atom catalysts by Fenton-like reaction has been established for water treatment; however, the Fe^IV=O generation pathway and oxidation behavior remain obscure. Employing an Fe−N−C catalyst with a typical Fe−N₄ moiety to activate peroxymonosulfate (PMS), we demonstrate that generating Fe^IV=O is mediated by an Fe−N−C−PMS* complex—a well-recognized nonradical species for induction of electron-transfer oxidation—and we determined that adjacent Fe sites with a specific Fe₁−Fe₁ distance are required. After the Fe atoms with an Fe₁-Fe₁ distance <4 Å are PMS-saturated, Fe−N−C−PMS* formed on Fe sites with an Fe₁-Fe₁ distance of 4–5 Å can coordinate with the adjacent Fe^II−N₄, forming an inter-complex with enhanced charge transfer to produce Fe^IV=O. Fe^IV=O enables the Fenton-like system to efficiently oxidize various pollutants in a substrate-specific, pH-tolerant, and sustainable manner, where its prominent contribution manifests for pollutants with higher one-electron oxidation potential.     

NiCo2O4/BiOCl/Bi24O31Br10 ternary Z-scheme heterojunction enhance peroxymonosulfate activation under visible light: Catalyst synthesis and reaction mechanism

The Z-scheme heterostructure for photocatalyst can effectively prolong the lifetime of photogenerated carriers and retain a higher conduction/valence band position, promoting the synergistic coupling of photocatalysis and peroxymonosulfate (PMS) activation. In order to fully utilize the luminous energy and realize the efficient activation of PMS, this work achieved successful construction of NiCo₂O₄/BiOCl/Bi₂₄O₃₁Br₁₀ ternary Z-scheme heterojunction by simultaneously synthesizing BiOCl and NiCo₂O₄ with NiCl₂ and CoCl₂ as the precursors. The intercalated BiOCl could serve as a carrier migration ladder to further achieve the spatial separation of electron-hole pairs, so that the oxidation and reduction processes separately occurred in different regions. Compared with the reported catalysts, the as-prepared composites exhibited the enhanced removal efficiency for tetracycline hydrochloride (TCH) in the visible light/PMS system, with a degradation efficiency of 85.30% in 2 min, and possessed good stability. Z-scheme heterojunction was shown to be beneficial for maximizing the superiority of photo-assisted Fenton-like reaction system. The experimental and characterization results confirmed that both non-radicals (¹O₂) and radicals (SO₅^?? and SO₄^??) were involved in the reaction process and the SO₅^?? generated by the oxidation of PMS played a crucial role in the TCH degradation. The possible reaction mechanism was finally proposed. This study provided new insight into the Z-scheme heterostructure to promote the photo-assisted Fenton-like reaction.     

1H and 13C NMR study of cyclopentadienyl metal carbonyls in the solid state

In this paper we deal with some structural and dynamic properties of Cp₂W₂(CO)₆ (I) and Cp₂Ru₂(CO)₄ (II) as shown by solid state ¹³C and ¹H NMR experiments. The IR and ¹³C CPMAS spectra of a polycrystalline sample of I show that this compound possesses the anti rotameric structure found in a previously reported X-ray diffraction study. The analysis of the spinning side-band manifold in the ¹³C CPMAS spectrum of I allows us to assess a different semi-bridging character between two CO-groups not seen from the X-ray results. The spectral features of compound II are fully consistent with the X-ray and solution structures previously reported. In both compounds the cyclopentadienyl ligands are involved in fast reorientation motions which modulate the magnetic interactions responsible for the relaxation of ¹³C resonances. The activation energies (E_a) associated with this reorientation process of the Cp ring along their C₅ coordination axis have been determined to be 15.5 and 10.2 kJ mol⁻¹ for I and II respectively on the basis of ¹H T₁ measurements at different temperatures. Furthermore, we show that an empirical relationship relates E_a values and T_min (the temperature at which proton relaxation is more efficient) in a related series of cyclopentadienyl compounds.     

Stability and regeneration of metal catalytic sites with different sizes in Fenton-like system

Metal-based catalysts with different site sizes (e.g., metal nanoparticles (NPs) and single atom catalysts (SACs)) demonstrated outstanding catalytic activities in versatile Fenton-like reactions. However, the surface/structural instability is a critical issue, which will result in rapid passivation in Fenton-like reaction and fail in long-term operation. The catalytic stability of the catalysts with different metal sizes considering versatile peroxides (H₂O₂, peroxymonosulfate (PMS), and peroxodisulfate (PDS)) should be analyzed. In addition, strategies for catalyst regeneration and recyclability improvement are also important to realize the metal-based catalysts for practical applications. In this review, catalytic stability of catalysts with different metal sizes in the backgrounds of versatile peroxides and water matrixes in Fenton-like reactions were first evaluated. Regeneration of metal catalytic sites with different methods were also reviewed. Finally, major challenges and development of methods concerning the stability and regeneration of metal catalytic sites with different sizes were discussed to understand the future researches of metal catalytic sites in Fenton-like reactions.     

Highly efficient degradation of emerging contaminants by magnetic CuO@FexOy derived from natural mackinawite（FeS） in the presence of peroxymonosulfate

In this study,natural mackinawite （Fe S）,a chalcophilic mineral,was utilized to prepare iron/copper bimetallic oxides （Cu O@Fe_xO_y） by displacement plating and calcination process.Various characterization methods prove that Cu⁰is successfully coated on the surface of Fe S,which were further oxidized to Cu O,Fe₃O₄and/or Fe₂O₃during calcination process,respectively.Cu O@Fe_xO_yperformed highly efficient...     

Crystallinity engineering of Au nanoparticles on graphene for in situ SERS monitoring of Fenton-like reaction

Fabrication of multifunctional nanoplatform to in situ monitor Fenton reaction is of vital importance to probe the underlying reaction process and design high-performance catalyst.Herein,a hybrid catalyst comprising of single-crystalline Au nanoparticles（SC Au NPs） on reduced graphene oxide（RGO） sheet was prepared,which not only exhibited an excellent ¹ O₂ mediated Fenton-like catalytic activity in promoting rhodamine 6 G（R6 G） degradation by activating H₂ O_...     

Enhanced Interfacial Electron Transfer by Asymmetric Cu-Ov-In Sites on In2O3 for Efficient Peroxymonosulfate Activation

Enhancing the peroxymonosulfate (PMS) activation efficiency to generate more radicals is vital to promote the Fenton-like reaction activity, however, how to promote the PMS adsorption and accelerate the interfacial electron transfer to boost its activation kinetics remains a great challenge. Herein, we prepared Cu-doped defect-rich In₂O₃ (Cu-In₂O₃/O_v) catalysts containing asymmetric Cu−O_v−In sites for PMS activation in water purification. The intrinsic catalytic activity is that the side-on adsorption configuration of the O−O bond (Cu−O−O−In) at the Cu-O_v-In sites significantly stretches the O−O bond length. Meanwhile, the Cu-O_v-In sites increase the electron density near the Fermi energy level, promoting more and faster electron transfer to the O−O bond for generating more SO₄⋅⁻ and ⋅OH. The degradation rate constant of tetracycline achieved by Cu-In₂O₃/O_v is 31.8 times faster than In₂O₃/O_v, and it shows the possibility of membrane reactor for practical wastewater treatment.     

Efficient activation of peroxymonosulfate by hollow cobalt hydroxide for degradation of ibuprofen and theoretical study

Hollow microsphere structure cobalt hydroxide (h-Co(OH)₂) was synthesized via an optimized solvothermal-hydrothermal process and applied to activate peroxymonosulfate (PMS) for degradation of a typical pharmaceutically active compound, ibuprofen (IBP). The material characterizations confirmed the presence of the microscale hollow spheres with thin nanosheets shell in h-Co(OH)₂, and the crystalline phase was assigned to α-Co(OH)₂. h-Co(OH)₂ could efficiently activate PMS for radicals production, and 98.6% of IBP was degraded at 10 min. The activation of PMS by h-Co(OH)₂ was a pH-independent process, and pH 7 was the optimum condition for the activation-degradation system. Scavenger quenching test indicated that the sulfate radical (SO₄^{? ?}) was the primary reactive oxygen species for IBP degradation, which contributed to 75.7%. Fukui index (f ^?) based on density functional theory (DFT) calculation predicted the active sites of IBP molecule for SO₄^{? ?} attack, and then IBP degradation pathway was proposed by means of intermediates identification and theoretical calculation. The developed hollow Co(OH)₂ used to efficiently activate PMS is promising and innovative alternative for organic contaminants removal from water and wastewater.     

Facile preparation of α-MnO2 nanowires for assembling free-standing membrane with efficient Fenton-like catalytic activity

Assembling MnO₂ nanowires into macroscopic membrane is a promising engineered technology for catalyst separation and enhancement of Fenton-like reaction activity, yet its development is limited by the deficiencies in preparation and property modulation of the MnO₂ nanowires. In this work, we developed a facile method using C₂H₅OH and CH₃COOK as reductive and vital control reagents to react with KMnO₄ by hydrothermal reaction at 140 °C for 12 h, to prepare the ultralong α-MnO₂ nanowires up to tens of micrometers with high purity and aspect ratio. Such strategy not only had the advantages of being mild, easily controlled and environmental pollution-free, but also endowed α-MnO₂ nanowires with excellent ability as a Fenton catalyst when assembled into free-standing membrane for degrading phenolic compounds (k_obs = 0.0738 ～ 0.1695 min^?1) in a continuous flow reaction. The reactive oxygen species (i.e., ^?OH) from Fenton-like reaction were enriched within this α-MnO₂ nanowire membrane via nanoconfinement effect, which further enhanced the mass transportation of ^?OH available for phenolic contaminants. MnO₂ nanowire membrane using our method possessed the high practical potential for water purify due to its easy-preparation and enhanced catalytic performances.     

Synthesis and characterization of copper(II) and nickel(II) coordination polymers containing 2,6-naphthalenedicarboxylate and bis(benzimidazole) ligands

Two coordination polymers, namely [Ni(L1)-(ndc)(H₂O)] _n (1) and [Cu(L2)_0.5(ndc)] _n (2) (L1 = 1,3-bis(2-methylbenzimidazol-1-ylmethyl)benzene, L2 = 1,4-bis(2-methylbenzimidazole)butane, H₂ndc = 2,6-naphthalenedicarboxylic acid) have been synthesized and characterized by single-crystal and powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, and elemental analysis. Complex 1 features a 2D 3-connected hcb network with 6³ topology, which is further extended into a 3D supramolecular framework by O–H···O hydrogen bonding interactions. Complex 2 possesses a 3D threefold interpenetrating (4,5)-connected xah topological network, and its Schläfli symbol is (4².6².8²)(4⁶.6⁴). Both complexes exhibit intense luminescence emissions in the solid state and promising catalytic activities for the degradation of Congo red azo dye in a Fenton-like process.     

Isatin N-protected ketimines with nitromethane catalyzed by chiral binol linked monomeric macrocyclic Cu(II)–salen complex

Chiral Cu-1B generated in situ was used as an efficient catalyst for the synthesis of β-nitroamines in high yield (88%) with excellent enantioselectivity (ee up to 99%) at RT in absence of co-catalyst via asymmetric aza-Henry reaction of various isatin derived N-Boc ketimines with nitromethane. This catalytic system did not work well with other nitroalkanes under the above optimized reaction conditions. To examine this catalytic behaviour, quantum chemical DFT calculations were performed with the nucleophiles (CH₂NO₂^? and CH₃CHNO₂^?) for the conversion of 1a to 2a using macrocyclic Cu-1B complex. The DFT calculated results have shown that the reaction with CH₂NO₂^? is more favourable than the corresponding CH₃CHNO₂^?. The calculated activation barriers suggest that the reaction with CH₂NO₂^? is ～8.0?kcal/mol energetically favoured than CH₃CHNO₂^?. This catalytic protocol was further used to obtain chiral β-diamines (a building block for pharmaceuticals) at gram scale. In order to elucidate the reaction mechanism of asymmetric aza Henry reaction kinetic experiments were performed with different concentrations of the catalyst Cu-1B, nitromethane and 1g as the representative substrate. The reaction of isatin N-Boc ketimine was first order with respect to the concentration of the catalyst and the nitromethane but did not depend on the initial concentration of the substrate. A possible mechanism for the aza Henry reaction was proposed.     

Surface sulfur vacancies enhanced electron transfer over Co-ZnS quantum dots for efficient degradation of plasticizer micropollutants by peroxymonosulfate activation

Peroxymonosulfate (PMS) activation in heterogeneous processes is a promising water treatment technology. Nevertheless, the high energy consumption and low efficiency during the reaction are ineluctable, due to electron cycling rate limitation. Herein, a new strategy is proposed based on a quantum dots (QDs)/PMS system. Co-ZnS QDs are synthesized by a water phase coprecipitation method. The inequivalent lattice-doping of Co for Zn leads to the generation of surface sulfur vacancies (SVs), which modulates the surface of the catalyst to form an electronic nonequilibrium surface. Astonishingly, the plasticizer micropollutants can be completely degraded within only tens of seconds in the Co-ZnS QDs/PMS system due to this type of surface modulation. The interfacial reaction mechanism is revealed that pollutants tend to be adsorbed on the cobalt metal sites as the electron donors, where the internal electrons of pollutants are captured by the metal species and transferred to the surface SVs. Meanwhile, PMS adsorbed on the SVs is reduced to radicals by capturing electrons, achieving effective electron recovery. Dissolved oxygen (DO) molecules are also easily attracted to catalyst defects and are reduced to O₂^??, further promoting the degradation of pollutants.     

Molybdenum phosphide (MoP) with dual active sites for the degradation of diclofenac in Fenton-like system

The leaching and non-recoverability of mental ions have always limited the practical application of Fenton-like processes.For the first time,we synthesized molybdenum phosphide(MoP) with dual active sites for the degradation of diclofenac(DCF) in the Fenton-like process.The DCF degradation rate constant(k) of MoP+H₂ O₂ process was calculated to be 0.13 min^-1 within 40 min,indicating a highly efficient catalytic ability of MoP.In addition,this catalyst exhibits a ...     

An Unprecedented FeMo6@Ce-Uio-66 Nanocomposite with Cascade Enzyme-Mimic Activity as Colorimetric Sensing Platform

Introducing the idea of integrated design and cascade activity into nanozyme, the novel integrated nanozymes (INAzymes), FeMo₆@Ce-Uio-66 (FC-66(n)), were designed and synthesized by encapsulating iron-based polyoxometalates (FeMo₆) into the ceria-based metal–organic framework (Ce-Uio-66). Due to the oxygen-driven reversible Ce³⁺/Ce⁴⁺ couple sites, the “Fenton-like” effect by iron centers, the “nanoscale proximity” effects by nanocages, and their synergistic effects, FC-66(n) as INAzymes exhibit elegant cascade enzyme-mimic activities (oxidase-, peroxidase-, and Fenton-like activity), which realizes INAzyme activities based on polyoxometalates based metal–organic framework (POMOFs). By employing dopamine (DA) detection as a model reaction, a high-efficient fluorescent “turning-on-enhanced” platform under near neutral conditions was established.     

Heterostructures with Built-in Electric Fields for Long-lasting Chemodynamic Therapy

Sustained signal activation by hydroxyl radicals (⋅OH) has great significance, especially for tumor treatment, but remains challenging. Here, a built-in electric field (BIEF)-driven strategy was proposed for sustainable generation of ⋅OH, thereby achieving long-lasting chemodynamic therapy (LCDT). As a proof of concept, a novel Janus-like Fe@Fe₃O₄−Cu₂O heterogeneous catalyst was designed and synthesized, in which the BIEF induced the transfer of electrons in the Fe core to the surface, reducing ≡Cu²⁺ to ≡Cu⁺, thus achieving continuous Fenton-like reactions and ⋅OH release for over 18 h, which is approximately 12 times longer than that of Fe₃O₄−Cu₂O and 72 times longer than that of Cu₂O nanoparticles. In vitro and in vivo antitumor results indicated that sustained ⋅OH levels led to persistent extracellular regulated protein kinases (ERK) signal activation and irreparable oxidative damage to tumor cells, which promoted irreversible tumor apoptosis. Importantly, this strategy provides ideas for developing long-acting nanoplatforms for various applications.     

Design of copper oxide and oxygen codoped graphitic carbon nitride activator for efficient radical and nonradical activation of peroxymonosulfate

Rational regulation of stable graphitic carbon nitride (CN) for superior peroxymonosulfate (PMS) activation is important in the catalytic degradation of water contaminants. In this work, the copper oxide and oxygen co-doped graphitic carbon nitride (CuO/O-CN) was prepared via one-step synthesis and applied in activating PMS for oxytetracycline (OTC) degradation, displaying superior catalytic performance. Systematic characterization and theoretical calculations indicated that the synergistic effect between the oxygen site of CN and CuO can modulate the electronic structure of the whole composite further facilitating the formation of non-radical ¹O₂ and various reactive radicals. Results of the influencing factor experiments revealed that CuO/O-CN has a strong resistance to the environmental impact. The degradation efficiency of OTC in the real water environment even exceeded that in the deionized water. After four successive runs of the optimal catalyst, the OTC removal rate was still as high as 91.3%. This work developed a high-efficiency PMS activator to remove refractory pollutants via both radical pathway and non-radical pathway, which showed a promising potential in the treatment of wastewaters.     

Synthesis,characterization, and crystal structures of 2D cobalt(II) and nickel(II) coordination polymers containing flexible bis(benzimidazole) ligands

Three coordination polymers, namely {[Ni(L1)(nip)(H₂O)]·2H₂O} _n (1), [Co(L2)(tbip)] _n (2), and {[Co₂(L3)₂(bptc)]·3H₂O} _n (3) (L1 = 1,4-bis(5,6-dimethylbenzimidazole)butane, L2 = 1,4-bis(5,6-dimethylbenzimidazole)-2-butylene, L3 = 1,3-bis(5,6-dimethylbenzimidazole)propane, H₂nip = 5-nitro-isophthalic acid, H₂tbip = 5-tert-butyl-isophthalic acid, H₄bptc = biphenyl-3,3′,4,4′-tetracarboxylic acid), have been synthesized under hydrothermal conditions and characterized by physicochemical and spectroscopic methods as well as by single-crystal X-ray diffraction analysis. Complexes 1 and 2 both feature a two-dimensional (4,4) layer with (4⁴ × 6²) topology. Complex 3 possesses a uninodal 4-connected 2D htb network. The fluorescence spectra and catalytic properties of the complexes for the degradation of methyl orange by sodium persulfate in a Fenton-like process are reported.     

Sustainable activation of peroxymonosulfate by the Mo(IV) in MoS2 for the remediation of aromatic organic pollutants

Although MoS₂ has been proved to be a very ideal cocatalyst in advanced oxidation process (AOPs), the activation process of peroxymonosulfate (PMS) is still inseparable from metal ions which inevitably brings the risk of secondary pollution and it is not conducive to large-scale industrial application. In this study, the commercial MoS₂, as a durable and efficient catalyst, was used for directly activating PMS to degrade aromatic organic pollutant. The commercial MoS₂/PMS catalytic system demonstrated excellent removal efficiency of phenol and the total organic carbon (TOC) residual rate reach to 25%. The degradation rate was significantly reduced if the used MoS₂ was directly carried out the next cycle experiment without any post-treatment. Interestingly, the commercial MoS₂ after post-treated with H₂O₂ can exhibit good stability and recyclability for cyclic degradation of phenol. Furthermore, the mechanism for the activation of PMS had been investigated by density functional theory (DFT) calculation. The renewable Mo⁴⁺ exposed on the surface of MoS₂ was deduced as the primary active site, which realized the direct activation of PMS and avoided secondary pollution. Taking into account the reaction cost and efficient activity, the development of commercial MoS₂ catalytic system is expected to be applied in industrial wastewater.