Reactive Sites Research Articles

PtCl2-Catalyzed Intramolecular Cyclization of α-Benzyl Allenoates to Afford Indenes and Furanones.

Indene and furanone are important ring structures widely present in active pharmaceutical molecules. Here, we have developed a straightforward method for the synthesis of indene and furanone via PtCl2-catalyzed intramolecular cyclization of α-benzyl allenoates. By altering the ester substitution pattern in the α-benzyl allenoates, we can regulate the reaction site, enabling two distinct intramolecular cyclization reactions that yield both indene and furanone products, respectively. For α-benzyl-substituted ethyl allenoate, the reaction proceeds via a 5-exo cyclization to form indene derivatives. In contrast, for α-benzyl-substituted tert-butyl allenoate, the reaction involves ester hydrolysis and intramolecular cyclization, yielding furanone products. This method operates efficiently under a 5 mol % PtCl2 catalyst and exhibits good tolerance toward various functional groups. Furthermore, furanone products can be obtained on a gram scale and further smoothly converted into 1,2-disubstituted furan.

Peroxymonosulfate Activation by Rice-Husk-Derived Biochar (RBC) for the Degradation of Sulfamethoxazole: The Key Role of Hydroxyl Groups.

In this work, rice-husk-derived biochar (RBC) was synthesized by using simple one-step pyrolysis strategies and served as catalysts to activate peroxymonosulfate (PMS) for degrading sulfamethoxazole (SMX). When the annealing temperature (T) = 800 °C, RBC800 exhibits the typical hardwood structure with several micropores and mesoporous. Furthermore, RBC800 obtains more defect sites than RBC600, RBC700, and RBC900. In the RBC800/PMS system, the removal rate of the SMX reached 92.0% under optimal conditions. The kinetic reaction rate constant (kobs) of the RBC800/PMS system was 0.009 min-1, which was about 1.50, 1.28, and 4.50 times that of the RBC600/PMS (kobs = 0.006 min-1), RBC700/PMS (kobs = 0.007 min-1), and RBC900/PMS (kobs = 0.002 min-1) systems, respectively. In the RBC800/PMS system, sulfate radical (SO4•-) is the main active species. Compared with other active sites, the hydroxyl group (C-OH) on the surface of RBC800 interacts more strongly with PMS, which is more likely to promote the stretching of the O-O bond of the PMS, thus breaking into the activated state and significantly reducing the activation energy required for reaction. The degradation intermediates of SMX were speculated, and the toxicity analysis was conducted. Generally, this work reveals in depth the interaction between reactive sites of biochar-based catalysts and PMS at the molecular level.

Magnetic coal gangue-based catalysts for peroxymonosulfate activation and benzo[a]pyrene degradation: The construction of Fe and N dual active sites

The magnetic coal gangue (CG)-based catalysts were successfully prepared by impregnation-calcination method with iron (Fe) and nitrogen (N) co-doping for peroxymonosulfate (PMS) activation, illustrating excellent catalytic property with 100.00 % removal rate of benzo[a]pyrene (BaP). Additionally, Fe/N co-doped CG catalysts (Fe-N-CG) possess desirable performance against co-existing anions and organic matter (HA), with a nearly 80.00 % removal rate in actual water systems. The mechanism of activating PMS and removing BaP was comprehensively analyzed through a series of characterizations and experiments, proving that the Fe and N double reaction sites could enhance the contribution of radical paths and non-radical paths for BaP degradation. Finally, the safety and prospects for practical environmental remediation via Fe-N-CG for PMS activation were further evaluated by ECOSAR toxicity analysis software and mung bean growth experiments. In summary, the development of Fe-N-CG widened the high-value utilization of CG and supplied a deep insight into the restoration of organically polluted environments.

Enhanced Olivine Reactivity in Wet Supercritical CO2 for Engineered Mineral Carbon Sequestration.

The success of CO2 mineralization as a potential solution for reducing carbon emissions hinges on understanding chemical interactions between basaltic minerals and CO2-charged fluids. This study provides a detailed analysis of olivine dissolution in CO2-water mixtures at 90 and 150 °C, 2-9 MPa, and for 8 and 24 h, in both water- and CO2-dominant conditions. By using olivine crystal sections instead of powders, surface agitation is prevented, closing the gap between laboratory studies and natural settings. Surface chemistry, texture, and cross-sectional properties were examined pre- and postreaction using a multiscale approach combining spectroscopic and imaging techniques. Results show that wet supercritical CO2 environments lead to significant olivine dissolution, forming Mg-depleted, Si-enriched etched surfaces, and under certain conditions, the formation of passivating silica precipitates. In contrast, reactions in aqueous fluids caused minimal changes in surface chemistry and texture with no silica precipitation. These observations indicate that reaction extent in the CO2-rich phase is greater relative to water-rich mixtures at equivalent temperature, pressure, and reaction duration. The presence of silica precipitates incorporating leached metals indicates limited transport of reactant away from reaction sites in a CO2-rich medium. This study semi-quantitatively evaluates reaction extents in both CO2-rich and aqueous systems across a wide range of parameters, demonstrating faster mineralization in CO2-rich environments and highlighting their potential for enhancing the CO2 storage efficiency.

Dibenzo-peri-Heptacene: A Stable Open-Shell Graphene Fragment With a Balanced Combination of Armchair and Zigzag Edge Structures.

Atomically precise open-shell graphene fragments, such as extended peri-acenes, hold significant interest for electronics and spintronics. However, their inherent high reactivity poses challenges for synthesis and application. In this study, a novel approach is introduced: the fusion of a zigzag-edged peri-tetracene with an all-armchair-edged hexa-peri-hexabenzocoronene (HBC) via two shared benzene rings to produce a stable open-shell hydrocarbon, named dibenzo-peri-heptacene (DBPH). The DBPH derivative 1 exhibits considerably enhanced stability, with a half-life (t1/2) of 46 days in toluene solution under ambient conditions. This improved stability is attributed to peri-benzannulation, enhanced aromatic stabilization, and kinetic protection of the reactive sites along the zigzag edges. The structure of 1 is unequivocally verified through single-crystal X-ray diffraction analysis. With a balanced combination of armchair and zigzag edge structures, derivative 1 displays a diradical character of 39.2% and a singlet-triplet gap of ≈-3.16 kcalmol-1. It features a narrow electrochemical energy gap (0.87 eV) and exhibits amphoteric redox behavior. Notably, its dication and dianion states manifest a closed-shell singlet ground state, representing doubly charged structures where a HBC unit is fused with a benzo[f]tetraphene moiety. This research paves the way for synthesizing novel open-shell graphene fragments with adjustable electronic properties and exceptional stability.

Boosting Photoelectrochemical Water Oxidation Performance of Ti–Fe2O3 Photoanode via NH2–MIL–53(FeCo) as a Cocatalyst

α–Fe2O3 is a promising photoanode that can be used for solar‐driven photoelectrochemical (PEC) water splitting. However, due to low carrier separation efficiency and slow water oxidation kinetics, the PEC performance of Ti–Fe2O3 is still severely hindered. Here, a novel inorganic–organic hybrid composite photoanode is prepared by depositing NH2–materials of institute Lavoisier (MIL)–53(FeCo) cocatalyst on the surface of Ti–Fe2O3 using solvothermal method. In the results, it is shown that the Ti–Fe2O3/NH2–MIL–53(FeCo) photoanode has a high photocurrent density (3.0 mA cm−2 at 1.23 V vs reversible hydrogen electrode (RHE), which is 5.1 times that of bare Ti–Fe2O3, and the initial potential of water oxidation also undergoes a negative change of about 100 mV. The separation efficiency of Ti–Fe2O3/NH2–MIL–53(FeCo) is significantly enhanced, and the charge injection efficiency increases from 17.6% to 68% at 1.23 V versus RHE. In the further research, it is suggested that the excellent PEC performance of Ti–Fe2O3/NH2–MIL–53(FeCo) may be attributed to an increase in carrier density, prolonged carrier recombination time, and an increase in exposed reactive sites. In this study, a new understanding for the design of Ti–Fe2O3 photoanodes with superior PEC performance based on metal organic framework modification is provided.

A promising platform for the rapid and sensitive sensing of mercury ion and its applications in biological and environmental system

Mercury ion (Hg2+) is one of harmful heavy metal ions that can accumulate inside the human organism and cause some health problems. Herein, a novel NBD derivative, 1-(2-((7-nitrobenzo[c] [1,2,5] oxadiazol-4-yl) amino) ethyl)-3-phenylthiourea (NBD-SCN), has been reasonably designed, which was simply synthesized by introducing NBD moiety as the fluorophore, phenyl-isothionitrate as the reaction site and ethylenediamine as a linker group, resulting in intense fluorescence emission with high fluorescence quantum yields. Intriguingly, probe NBD-SCN provides a dual-mode colorimetric and fluorescence response pattern for the sensing of mercury ion with great limit of detections (3.6 nM) and rapid response time (4 s). The strong combination of mercury ions and sulfur atoms leads to intramolecular cyclization, causing the color of probe solution changed from orange to pale yellow as well as a complete vanishing of fluorescence intensity. The proposed reaction mechanism was verified by fluorescence and UV titration, 1H NMR, FTIR, HRMS analyses and DFT studies. Motivated by an impressive chromatic variation, test strip sensing platform are facilely constructed for real-time and on-site measurement of Hg2+ levels. Furthermore, confocal imaging experiments verify that this probe can be used for monitoring mercury ion in living mung bean sprouts and in biological systems in real time.

Electrochemical Growth of Copper Crystals on SPCE for Electrocatalysis Nitrate Reduction.

Copper is efficient, has a high conductivity (5.8 × 107 S/m), and is cost-effective. The use of copper-based catalysts is promising for the electrocatalytic reduction of nitrates. This work aims to grow and characterize copper micro-crystals on Screen-Printed Electrodes (SPEs) for NO3- reduction in water. Copper micro-crystals were grown by cyclic voltammetry. Different cycles (2, 5, 7, 10, 12, 15) of copper electrodeposition were investigated (potential ranges from -1.0 V to 0.0 V, scan rate of 0.1 V s-1). Electrodeposition generated different morphologies of copper crystals on the electrodes, as a function of the number of cycles, with various performances. The presence of numerous edges and defects in the copper micro-crystal structures creates highly reactive active sites, thus favoring nitrate reduction. The manufactured material can be successfully employed for environmental applications.

Ionic Liquid-Assisted Synthesis of Higher Loaded Ni/Fe Dual-Atom Catalysts in N, F, B Codoped Carbon Matrix for Accelerated Sulfur Reduction Reaction.

In response to mitigating the severe shuttle effect within lithium-sulfur batteries, single-atom catalysts have emerged as one of the most effective solutions. Here, N, F, B codoped porous hollow carbon nanocages (NFB-NiFe@NC) with high Ni and Fe doping are rationally designed and synthesized using ionic liquids (ILs) as dopants. The introduction of ILs inhibits the growth of zeolitic imidazolate framework-8 (ZIF8), resulting in NFB-ZIF8 precursors with smaller particle sizes, enabling higher loading dual-atom catalysts. Meanwhile, the abundant heteroatoms increase the reactive sites and alter the carbon matrix's nonpolar intrinsic properties, thus enhancing the chemisorption of polysulfides. The synergistic interaction of the heteroatoms with Ni and Fe dual-atoms ultimately promotes the catalytic conversion kinetics of polysulfides. As a result of these beneficial properties, the cells prepared using the NFB-NiFe@NC modified separator exhibit significantly improved performance, including a high initial capacity of 1448 mAh g-1 at 0.2 C. Even at a high S-loading of 7.6 mg cm-2, the ideal area capacity of 8.38 mAh cm-2 can still be maintained at 0.1 C. New insights are provided here for designing highly loaded dual-atom catalysts for application in lithium-sulfur batteries.

Xylan-based full-color room temperature phosphorescence materials enabled by imine chemistry

Developing sustainable matrix and efficient bonding mode for preparing room temperature phosphorescence (RTP) materials with full-color afterglows is attractive but still challenging. Here, xylan, a hemicellulose by-product from the paper mill, is used to construct full-color RTP materials based on imine bonds. Xylan is oxidation by periodate to introduce aldehyde groups to increase reaction sites; aromatic amines with different π conjugations can be readily anchored to dialdehyde xylan (DAX) by imine chemistry. The dual rigid environments were constructed by hydrogen bonding and imine covalent bonding, which can facilitate the triplet population and suppress non-radiative transitions, thus the xylan derivatives display satisfactory RTP performances. As the degree of conjugation of the chromophore increases, the afterglow colors can be changed from blue to green, yellow, and then to red. Thus, such a universal, facile, and eco-friendly strategy can be used to fabricate full-color RTP materials, which show a bright future in information encryption and advanced anti-counterfeiting. These results unambiguously state that the biodegradable paper mill waste-based RTP materials are convincingly expected to replace and surpass petroleum polymer-based counterparts.

Development of modified MgO/biochar composite for chemical adsorption enhancement to cleanup fluoride-contaminated groundwater

Fluoride contamination in groundwater has become a global environmental issue. Magnesium oxide (MgO) has demonstrated effectiveness as an adsorbent in treating fluoride pollution in groundwater. However, its use in powder and fine granular form often results in losses during the adsorption process, posing challenges for post-treatment recovery and potentially causing secondary environmental pollution. In this study, two novel fluoride adsorbents [rice husk (RH) and spent coffee grounds (SCG)-based magnesium oxide (MgO) biochar composites (MgO/RH and MgO/SCG)] were developed to cleanup fluoride-polluted groundwater. During the adsorbent synthesis process, RH and SCG biochar were pyrolyzed at 500 °C and modified by calcination using MgO. Both MgO/RH and MgO/SCG surfaces exhibited abundant pore structures and formed MgO crystal phases. Batch experiments results show that when the MgO/RH and MgO/SCG material dosages were 1 g/L, fluoride removal rates reached 80% and 86% respectively. The isotherms and kinetics of fluoride adsorption with MgO/RH and MgO/SCG followed the Langmuir isotherm equation and pseudo-second-order kinetic model. The maximum fluoride adsorption capacities of MgO/RH and MgO/SCG were 63.47 mg/g and 141.98 mg/g, respectively, indicating these materials used mono-layer adsorption mechanism for fluoride adsorption. The addition of MgO into the pores of porous adsorbent materials effectively increased their reactive sites and enhanced the adsorption performance of carbon materials. Particularly, SCG biochar had a richer pore structure than RH biochar, providing a larger contact surface area, facilitating the effective dispersion and doping of MgO into the pores. Therefore, MgO/SCG composite exhibited excellent fluoride adsorption properties in water, indicating the potential for developing a new type of MgO-modified SCG adsorbent material with green prospects. This composite effectively mitigated fluoride contamination, reducing the fluoride concentration in groundwater. Both RH and SCG are agricultural and food waste by-products, thus offering the opportunity to significantly reduce production, operation, and maintenance costs.

Cd(II)-based fish-bone-like 1D coordination polymer: structural elucidation and computational study

{[Cd(L)2(PBT)2]}n (1) [H2L = 5-nitro-isophthalic acid; PBT = 2-pyridin-4-ylbenzothiazole], 1D Coordination Polymer (1D-CP), is characterized by single crystal X-ray diffraction. The structure of 1 contains carboxylate bridges of L2- to Cd(II), where one carboxylate chelates to Cd(II) and the other -COO bridges to two neighboring Cd(II) centers that then form eight-membered dinuclear metallacycles (Cd2C2O4). The 1D chains self-assemble via H-bonding and π⋅⋅⋅π interactions to form a supramolecular aggregate that resembles a fish-bone pattern. These interactions are further explored by Hirshfeld Surface Analysis. Density Functional Theory (DFT) computations using the crystallographic parameters of 1 predicted an energy gap, ΔE (EHOMO – ELUMO) of 3.67 eV, which is comparable to the experimental band gap obtained from a Tauc’s plot, 3.73 eV. The band gap value demonstrates the semiconducting character and may be used for device fabrication. Furthermore, molecular electrostatic potential (MEP) shows strong electrophilic reaction potential and predicts reactive sites. The PBT ligand is emissive (370 nm) while H2L is non-emissive. DMF suspensions of 1 emit at 525 nm with a long lifetime, 0.715 ns compared to the lifetime of PBT (0.05 ns). This supports that extended conjugation occurs upon formation of the 1D-CP, altering the photophysics.

Optimizing the reaction pathway of methane photo-oxidation over single copper sites.

Direct photocatalytic conversion of methane to value-added C1 oxygenate with O2 is of great interest but presents a significant challenge in achieving highly selective product formation. Herein, a general strategy for the construction of copper single-atom catalysts with a well-defined coordination microenvironment is developed on the basis of metal-organic framework for selective photo-oxidation of CH4 to HCHO. We propose the directional activation of O2 on the mono-copper site breaks the original equilibrium and tilts the balance of radical formation almost completely toward •OOH. The synchronously generated •OOH and •CH3 radicals rapidly combine to form HCHO while inhibiting competing reactions, thus resulting in ultra-highly selective HCHO production (nearly 100%) with a time yield of 2.75 mmol gcat-1 h-1. This work highlights the potential of rationally designing reaction sites to manipulate reaction pathways and achieve selective CH4 photo-oxidation, and could guide the further design of high-performance single-atom catalysts to meet future demand.

Functionalized Nanomaterials for Detecting Environmental Pollutants

AbstractThe environment consists of wide diversity, of which, an integral and most diversifying part is the living organisms, and hence it is imperative to design novel strategies that could alleviate pollutants and detect them at very minute levels. The functionalization of nanomaterials provides a very facile and efficient tool for the design of robust sensors that could detect pollutants that contaminate air, water, and soil. Because of their nanoscale size, these materials have enhanced surface‐to‐volume ratio, which in turn provide more reaction sites for the analyte interaction and enables highly specific and sensitive detection. Different nanomaterials like metal/metal oxide nanoparticles, quantum dots, carbon‐based nanomaterials, and miscellaneous nanomaterials like polymer, dendrimers, metal‐organic frameworks are functionalized with suitable ligands for efficient detection of a wide range of pollutants such as heavy metals, pesticides, industrial wastes, volatile organic compounds, toxic gases, and environmental pathogens with efficient level of sensitivity. In this review, we will briefly discuss different types of functionalized nanomaterials, strategies adopted for their functionalization, detection methodologies pursued for specific sensing and detection of different types of pollutants and their critical analysis, and future outlook.

Nature of Reactive Sites in TS-1 from 15N Solid-State NMR and Ti K-Edge X-Ray Absorption Spectroscopic Signatures Upon Pyridine Adsorption.

Ti-containing zeotypes, notably titanosilicalite-1 (TS-1), are prominent examples of heterogeneous catalysts that have found applications in selective oxidation processes with hydrogen peroxide. Despite extensive characterization studies including using various probe molecules to interrogate the nature and the local environment of Ti sites, their detailed structure (as well as reactivity) remains elusive. Here, we demonstrate that using low temperature 15N magic angle spinning (MAS) ssNMR spectroscopy of adsorbed pyridine on TS-1 combined with Ti K-edge XANES on a range of samples (dehydrated, hydrated, contacted with H2O2 and pyridine) provides unique information regarding the Ti sites, highlighting their reactivity and dynamic nature. While dehydrated TS-1 shows only Lewis acid sites, the presence of H2O generates Brønsted acid sites, whose amount correlates with water loading. Moreover, the methodology─based on 15N ssNMR and Ti K-edge XANES─applied to a library of samples with various Ti-loadings and absence of extraframework TiO2 also enables quantification of the amount of Lewis acid sites and to establish a structure-activity descriptor (ratio of pyridine adsorbed on silanols vs titanium). Complementary analysis including computational modeling reveals that the reaction of Ti sites with H2O generates an acidic bridging silanol Ti-(OH)-Si, upon hydrolysis of one Ti-O-Si linkage, where Ti expands its coordination from four to pentacoordinated according to XAS.

Morphology Regulation and Oxygen Vacancy Construction Synergistically Boosting the Piezocatalytic Degradation and Pure Water Splitting of SrTiO3.

In recent years, the development of high-efficiency piezoelectric materials is an effective means to make full use of the mechanical energy widely existing in the environment. However, there are few reports on multi-strategies synergistically improving piezocatalytic activity, and the mechanism of synergistic enhancement of piezocatalytic activity also receives less attention. Herein, the SrTiO3 nanorods decorated with tunable surface oxygen vacancy concentrations are prepared. Oxygen vacancy-optimized SrTiO3 nanorods exhibit efficient and undifferentiated piezocatalytic degradation activities for both anionic and cationic dyes under ultrasonic vibration. More importantly, it can split water into H2 and H2O2 with high production rates of 540 and 332 µmol g-1 h-1 without adding any sacrificial agents and cocatalysts, respectively. Mechanism analyses demonstrate that the 1D structure is beneficial to mechanical energy harvesting, and the surface oxygen vacancy induces larger surface asymmetry and piezoelectric response, synergically enhancing the piezocatalytic activity of SrTiO3 nanorods. In addition, metal deposition experiments under different conditions show that SrTiO3 nanorods possess abundant reactive catalytic sites in the piezocatalytic reaction process. This work provides a further understanding of piezocatalysis in piezoelectric nanomaterials and is important for the development of efficient piezoelectric catalysts.

Ethylene Glycol (EG)-Derived Chlorine-Resistant Cu0/TiO2-x for Efficient Photocatalytic Degradation of Nitrate to N2 without Sacrificial Agents at Near-Neutral pH Conditions: The Synergistic Effects of Cu0 and EG Radicals.

The selective photoreduction of nitrate to nontoxic nitrogen gas has emerged as an energy-efficient and environmentally friendly route for nitrate removal. However, the coexisting high-concentration chloride ions in wastewater can exert a significant influence on nitrate reduction due to the competitive adsorption and corrosion of Cl- on photocatalysts. Herein, we prepared ethylene glycol-Cu/TiO2-x (EG-Cu/TiO2-x) through a solvothermal reaction of Cu-doped TiO2 in an EG solution. The photodegradation of nitrate using EG-Cu/TiO2-x without adding sacrificial agents can efficiently occur in near-neutral pH solutions containing 50 mM Cl- with 95.26% of NO3- removal and 76.52% of N2 selectivity. Moreover, the photocatalyst performance remained at a high level after 8 cycles. In this work, NO3- was first converted to NH4+ by Cu0 and Ti3+, followed by the NH4+-to-N2 conversion by photogenerated chlorine free radicals. Compared to HO•, Cl•, and Cl2•-, ClO• is proved to play the predominant role in transforming NH4+ to N2. The EG radicals produced by UV light impede Cl- adsorption on Cu, protecting Cu0 from being corroded. What's more, photoelectrons can reduce Ti4+ to Ti3+ and protect Cu0 from being oxidized, enabling the stability of reactive sites. This work provides novel insights and understanding on designing photocatalysts for NO3- removal in solutions containing chloride ions, highlighting the significance of eliminating Cl- by EG radicals and adjusting the conversion process of NO3- for the efficient removal of NO3-.

Enhanced sensitivity and selectivity of ZnSe/PANI nanocomposite for Low-ppm NO2 detection at room temperature gas sensor application

The utilization of n-p composite-based gas sensors has garnered substantial interest within the field of gas sensing. This heightened attention can be attributed to the remarkable band alignment of the constituent materials which results in superior charge transfer rate, increased gas interaction sites and reduced optimum operating temperature. In this work, n-ZnSe/p-PANI composites were prepared by simple hydrothermal technique. The obtained X-ray diffraction pattern confirms the phase formation ZnSe, PANI and ZnSe/PANI composites. The pure ZnSe exhibits a sensing performance at a higher operating temperature of 100 °C, whereas ZnSe/PANI composite sample demonstrates an improved sensing response at 30 °C. Notably, the 20 wt.% composite sample (ZnSe–P2) achieved a maximum sensing response of 77 % towards 20 ppm of NO2 gas molecule. Additionally, the sensor exhibits the response time (Tres) of 112 s and recovery time (Trec) of 648 s, at an operating temperature of 30 °C. It also shows better stability, reproducibility and specific selectivity towards NO2 gas molecule. The superior sensing behavior of the ZnSe-P2 sensor can be ascribed to the development of a depletion region in the interface of ZnSe/PANI composites, which improved the charge transfer rate and increased the number of reactive sites. Therefore, the formation of n-p inorganic-organic composite strategy offers an effective approach for detecting NO2 gas molecules at lower temperature of 30 °C.

Boosting Reactive Oxygen Species Generation via Contact‐Electro‐Catalysis with FeIII‐Initiated Self‐cycled Fenton System

AbstractContact Electro‐Catalysis (CEC) using commercial dielectric materials in contact‐separation cycles with water can trigger interfacial electron transfer and induce the generation of reactive oxygen species (ROS). However, the inherent hydrophobicity of commercial dielectric materials limits the effective reaction sites, and the generated ROS inevitably undergo self‐combination to form hydrogen peroxide (H2O2). In typical CEC systems, H2O2 does not further decompose into ROS, leading to suboptimal reaction rates. Addressing the generation and activation of H2O2 is therefore crucial for advancing CEC. Here, we synthesized a catalyst by loading the dielectric material polytetrafluoroethylene (PTFE) onto ZSM‐5 (PTFE/ZSM‐5, PZ for short), achieving uniform dispersion of the catalyst in water for the first time. The introduction of an FeIII‐initiated self‐cycling Fenton system (SF‐CEC), with the synergistic effects of O2 activation and FeIII‐activated H2O2, further enhanced ROS generation. In the FeIII‐initiated SF‐CEC system, the synergistic effects of ROS and protonated azo dyes enabled nearly 99 % degradation of azo dyes within 10 minutes, a sixfold improvement compared to the CEC system. This represents the fastest degradation rate of methyl orange dye induced by ultrasound to date. Without extra oxidants, this system enabled stable dissolution of precious metals in weakly acidic solutions at room temperature, achieving 80 % gold dissolution within 2 hours, 2.5 times faster than similar CEC systems. This study also corrects the unfavorable perception of CEC applications under acidic conditions, providing new insights for the fields of dye degradation and precious metal recovery.

Catalytic Asymmetric Conjugate Addition and Allylic Substitution of Cyclobutenones with Arylzinc Halides

Comprehensive SummaryConjugate addition and allylic substitution are two essential chemical transformations, and they could be competitive for substrates with multiple reactive sites. Herein, we report the diversified enantioselective synthesis of cyclobutenes via the functionalization of cyclobutenones. The conjugate addition of cyclobutenones with arylzinc halides provided enantioenriched cyclobutenes with all‐carbon quaternary centers. On the other hand, when cyclobutenones with gem‐dichloro groups were employed, a chemo‐ and enantioselective allylic substitution occurred. Further synthetic utility was demonstrated for synthesizing versatile cyclobutane derivatives, together with ring‐opening and expansion products.