Enhanced Catalytic Ozonation for Eliminating CH3SH via Stable and Circular Electronic Metal-Support Interactions of Si-O-Mn Bonds with Low Mn Loading

pH/glutathione-responsive theranostic nanoprobes for chemoimmunotherapy and magnetic resonance imaging of ovarian cancer cells

The integration of immunotherapy and standard chemotherapy holds great promise for enhanced anticancer effects. In this study, we prepared a pH- and glutathione (GSH)-sensitive manganese-doped mesoporous silicon (MMSNs) based drug delivery system by integrating paclitaxel (PTX) and anti-programmed cell death-ligand 1 antibody (aPD-L1), and encapsulating with polydopamine (PDA) for chemoimmunosynergic treatment of ovarian cancer cells. The nanosystem was degraded in response to the tumor weakly acidic and reductive microenvironment. The Mn2+ produced by degradation can be used as a contrast agent for magnetic resonance (MR) imaging to provide visual exposure to tumor tissue. The released PTX can not only kill tumor cells directly, but also induce immunogenic death (ICD) of tumor cells, which can play a synergistic therapeutic effect with aPD-L1. Therefore, our study is expected to provide a promising strategy for improving the efficacy of cancer immunotherapy and the detection rate of cancer.

Optimization of Carbon-Defect Engineering to Boost Catalytic Ozonation Efficiency of Single Fe─N4 Coordination Motif

Carbon-defect engineering in single-atom metal-nitrogen-carbon (M─N─C) catalysts by straightforward and robust strategy, enhancing their catalytic activity for volatile organic compounds, and uncovering the carbon vacancy-catalytic activity relationship are meaningful but challenging. In this study, an iron-nitrogen-carbon (Fe─N─C) catalyst is intentionally designed through a carbon-thermal-diffusion strategy, exposing extensively the carbon-defective Fe─N4 sites within a micro-mesoporous carbon matrix. The optimization of Fe─N4 sites results in exceptional catalytic ozonation efficiency, surpassing that of intact Fe─N4 sites and commercial MnO2 by 10 and 312 times, respectively. Theoretical calculations and experimental data demonstrated that carbon-defect engineering induces selective cleavage of C─N bond neighboring the Fe─N4 motif. This induces an increase in non-uniform charges and Fermi density, leading to elevated energy levels at the center of Fe d-band. Compared to the intact atomic configuration, carbon-defective Fe─N4 site is more activated to strengthen the interaction with O3 and weaken the O─O bond, thereby reducing the barriers for highly active surface atomic oxygen (*O/*OO), ultimately achieving efficient oxidation of CH3SH and its intermediates. This research not only offers a viable approach to enhance the catalytic ozonation activity of M─N─C but also advances the fundamental comprehension of how periphery carbon environment influences the characteristics and efficacy of M─N4 sites.

Management of methyl mercaptan contained in waste gases - an overview

Methyl mercaptan is a typical volatile organosulfur pollutant contained in many gases emitted by urban waste treatment, various industries, natural gas handling, refining processes, and energy production. This work is a comprehensive overview of the scientific and practical aspects related to the management of methyl mercaptan pollution. The main techniques, including absorption, adsorption, oxidation, and biological treatments, are examined in detail. For each method, its capability as well as the technical advantages and drawbacks have been highlighted. The emerging methods developed for the removal of methyl mercaptan from natural gas are also reviewed. These methods are based on the catalytic conversion of CH3SH to hydrocarbons and H2S.

Space-confined manganese oxides nanosheets for efficient catalytic decomposition of ozone

Ground-level ozone has long posed a substantial menace to human well-being and the ecological milieu. The widely reported manganese-based catalysts for ozone decomposition still facing the persisting issues encompass inefficiency and instability. To surmount these challenges, we developed a mesoporous silica thin films with perpendicular nanochannels (SBA(⊥)) confined Mn3O4 catalyst (Mn3O4@SBA(⊥)). Under a weight hourly space velocity (WHSV) of 500,000 mL g-1 h-1, the Mn3O4@SBA(⊥) catalyst exhibited 100% ozone decomposition efficiency in 5 h and stability across a wide humidity range, which exceed the performance of bulk Mn3O4 and Mn3O4 confine in commonly reported SBA-15. Rapidly decompose 20 ppm O3 to a safety level below 100 μg m-3 in the presence of dust in smog chamber (60 × 60 × 60 cm) was also realized. This prominent catalytic performance can be attributed to the unique confined structure engenders the highly exposed active sites, facilitate the reactant-active sites contact and impeded the water accumulation on the active sites. This work offers new insights into the design of confined structure catalysts for air purification.

Piezocatalysis for Chemical-Mechanical Polishing of SiC: Dual Roles of t-BaTiO3 as a Piezocatalyst and an Abrasive

Chemical mechanical polishing (CMP) offers a promising pathway to smooth third-generation semiconductors. However, it is still a challenge to reduce the use of additional oxidants or/and energy in current CMP processes. Here, a new and green atomically smoothing method: Piezocatalytic-CMP (Piezo-CMP) is reported. Investigation shows that the Piezo-CMP based on tetragonal BaTiO3 (t-BT) can polish the rough surface of a reaction sintering SiC (RS-SiC) to the ultra-smooth surface with an average surface roughness (Ra) of 0.45 nm and the rough surface of a single-crystal 4H-SiC to the atomic planarization Si and C surfaces with Ra of 0.120 and 0.157 nm, respectively. In these processes, t-BT plays a dual role of piezocatalyst and abrasive. That is, it piezo-catalytically generates in-situ active oxygen species to selectively oxidize protruding sites of SiC surface, yielding soft SiO2, and subsequently, it acts as a usual abrasive to mechanically remove these SiO2. This mechanism is further confirmed by density functional theory (DFT) calculation and molecular simulation. In this process, piezocatalytic oxidation is driven only by the original pressure and friction force of a conventional polishing process, thus, the piezo-CMP process do not require any additional oxidant and energy, being a green and effective polishing method.

Unraveling Valence Electron Number Dependent Excitonic Effects over M1-N3C1 Sites in Single-Atom Catalysts

Excitonic effects significantly influence the selective generation of reactive oxygen species and photothermal conversion efficiency in photocatalytic reactions; however, the intrinsic factors governing excitonic effects remain elusive. Herein, a series of single-atom catalysts with well-defined M1-N3C1 (M = Mn, Fe, Co, and Ni) active sites are designed and synthesized to investigate the structure-activity relationship between photocatalytic materials and excitonic effects. Comprehensive characterization and theoretical calculations unveil that excitonic effects are positively correlated with the number of valence electrons in single metal atoms. The single Mn atom with 5.93 valence electrons exhibits the weakest excitonic effects, which dominate superoxide radical (O2•-) generation through charge transfer and enhance photothermal conversion efficiency. Conversely, the single Ni atom with 9.27 valence electrons exhibits the strongest excitonic effects, dominating singlet oxygen (1O2) generation via energy transfer while suppressing photothermal conversion efficiency. Based on the valence electron number dependent excitonic effects, a reaction environment with hyperthermia and abundant cytotoxic O2•- is designed, achieving efficient and stable water disinfection. This work reveals single metal atom dependent excitonic effects and presents an atomic-level methodology for catalytic application targeted reaction environment tailoring.

Selective Synergistic Catalytic Elimination of NOx and CH3SH via Engineering Deep Oxidation Sites against Toxic Byproducts Formation

NOx and CH3SH as two typical air pollutants widely coexist in various energy and industrial processes; hence, it is urgent to develop highly efficient catalysts to synergistically eliminate NOx and CH3SH. However, the catalytic system for synergistically eliminating NOx and CH3SH is seldom investigated to date. Meanwhile, the deactivation effects of CH3SH on catalysts and the formation mechanism of toxic byproducts emitted from the synergistic catalytic elimination reaction are still vague. Herein, selective synergistic catalytic elimination (SSCE) of NOx and CH3SH via engineering deep oxidation sites over Cu-modified Nb-Fe composite oxides supported on TiO2 catalyst against toxic CO and HCN byproducts formation has been originally demonstrated. Various spectroscopic and microscopic characterizations demonstrate that the sufficient chemisorbed oxygen species induced by the persistent electron transfer from Nb-Fe composite oxides to copper oxides can deeply oxidize HCOOH to CO2 for avoiding highly toxic byproducts formation. This work is of significance in designing superior catalysts employed in more complex working conditions and sheds light on the progress in the SSCE of NOx and sulfur-containing volatile organic compounds.

Acetone Efficient Degradation under Simulated Humid Conditions by Mn-O-Pt Interaction Taming-Triggered Water Dissociation Intensification

As a generally existing component in industrial streams, H2O usually inhibits the catalytic degradation efficiency of volatile organic compounds (VOCs) greatly. Here, we propose a novel strategy that accelerates the H2O dissociation and facilitates positive feedbacks during VOC oxidation by fabricating citric acid (CA)-assisted Pt(K)-Mn2O3/SiO2 (Pt-Mn/KS-xCA). Results reveal that the complexation of carboxyl groups of citric acid with Mn cations leads to the formation of small Mn2O3 (4.1 ± 0.2 nm) and further enhances the Mn-O-Pt interaction (strengthened by the Si-O-Mn interaction), which can transfer more electrons from Pt-Mn/KS-6CA to H2O, thus facilitating its breaking of covalent bonds. It subsequently produces abundant surface hydroxyl groups, improving the adsorption and activation abilities of acetone reactant and ethanol intermediate. Attributing to these, the acetone turnover frequency value of Pt-Mn/KS-6CA is 1.8 times higher than that of Pt-Mn/KS at 160 °C, and this multiple changes to 6.3 times in the presence of H2O. Remarkably, acetone conversion over Pt-Mn/KS-6CA increases by up to 14% in the presence of H2O; but it decreases by up to 26% for Pt-Mn/KS due to its weak dissociation ability and high adsorption capacity toward H2O. This work sheds new insights into the design of highly efficient catalytic materials for VOC degradation under humid conditions.

Engineering the Crystal Facet of Monoclinic NiO for Efficient Catalytic Ozonation of Toluene

Modulating oxygen vacancies of catalysts through crystal facet engineering is an innovative strategy for boosting the activity for ozonation of catalytic volatile organic compounds (VOCs). In this work, three kinds of facet-engineered monoclinic NiO catalysts were successfully prepared and utilized for catalytic toluene ozonation (CTO). Density functional theory calculations revealed that Ni vacancies were more likely to form preferentially than O vacancies on the (110), (100), and (111) facets of monoclinic NiO due to the stronger Ni-vacancy formation ability, further affecting O-vacancy formation. Extensive characterizations demonstrated that Ni vacancies significantly promoted the formation of O vacancies and thus reactive oxygen species in the (111) facet of monoclinic NiO, among the three facets. The performance evaluation showed that the monoclinic NiO catalyst with a dominant (111) facet exhibits excellent performance for CTO, achieving a toluene conversion of ∼100% at 30 °C after reaction for 120 min under 30 ppm toluene, 210 ppm ozone, 45% relative humidity, and a space velocity of 120 000 h-1. This outperformed the previously reported noble/non-noble metal oxide catalysts used for CTO at room temperature. This study provided novel insight into the development of highly efficient facet-engineered catalysts for the elimination of catalytic VOCs.

Catalytic ozonation mechanism over M1-N3C1 active sites

The structure-activity relationship in catalytic ozonation remains unclear, hindering the understanding of activity origins. Here, we report activity trends in catalytic ozonation using a series of single-atom catalysts with well-defined M1-N3C1 (M: manganese, ferrum, cobalt, and nickel) active sites. The M1-N3C1 units induce locally polarized M - C bonds to capture ozone molecules onto M atoms and serve as electron shuttles for catalytic ozonation, exhibiting excellent catalytic activities (at least 527 times higher than commercial manganese dioxide). The combined in situ characterization and theoretical calculations reveal single metal atom-dependent catalytic activity, with surface atomic oxygen reactivity identified as a descriptor for the structure-activity relationship in catalytic ozonation. Additionally, the dissociation barrier of surface peroxide species is proposed as a descriptor for the structure-activity relationship in ozone decomposition. These findings provide guidelines for designing high-performance catalytic ozonation catalysts and enhance the atomic-level mechanistic understanding of the integral control of ozone and methyl mercaptan.

Accelerated Catalytic Ozonation in a Mesoporous Carbon-Supported Atomic Fe-N4 Sites Nanoreactor: Confinement Effect and Resistance to Poisoning

The design of a micro-/nanoreactor is of great significance for catalytic ozonation, which can achieve effective mass transfer and expose powerful reaction species. Herein, the mesoporous carbon with atomic Fe-N4 sites embedded in the ordered carbon nanochannels (Fe-N4/CMK-3) was synthesized by the hard-template method. Fe-N4/CMK-3 can be employed as nanoreactors with preferred electronic and geometric catalytic microenvironments for the internal catalytic ozonation of CH3SH. During the CH3SH oxidation process, the mass transfer coefficient of the Fe-N4/CMK-3 confined system with sufficient O3 transfer featured a level of at least 1.87 × 10-5, which is 34.6 times that of the Fe-N4/C-Si unconfined system. Detailed experimental studies and theoretical calculations demonstrated that the anchored atomic Fe-N4 sites and nanoconfinement effects regulated the local electronic structure of the catalyst and promoted the activation of O3 molecules to produce atomic oxygen species (AOS) and reactive oxygen species (ROS), eventually achieving efficient oxidation of CH3SH into CO2/SO42-. Benefiting from the high diffusion rate and the augmentation of AOS/ROS, Fe-N4/CMK-3 exhibited an excellent poisoning tolerance, along with high catalytic durability. This contribution provides the proof-of-concept strategy for accelerating catalytic ozonation of sulfur-containing volatile organic compounds (VOCs) by combining confined catalysis and atomic catalysts and can be extended to the purification of other gaseous pollutants.

Disentangling Local Interfacial Confinement and Remote Spillover Effects in Oxide-Oxide Interactions

Supported oxides are widely used in many important catalytic reactions, in which the interaction between the oxide catalyst and oxide support is critical but still remains elusive. Here, we construct a chemically bonded oxide-oxide interface by chemical deposition of Co3O4 onto ZnO powder (Co3O4/ZnO), in which complete reduction of Co3O4 to Co0 has been strongly impeded. It was revealed that the local interfacial confinement effect between Co oxide and the ZnO support helps to maintain a metastable CoOx state in CO2 hydrogenation reaction, producing 93% CO. In contrast, a physically contacted oxide-oxide interface was formed by mechanically mixing Co3O4 and ZnO powders (Co3O4-ZnO), in which reduction of Co3O4 to Co0 was significantly promoted, demonstrating a quick increase of CO2 conversion to 45% and a high selectivity toward CH4 (92%) in the CO2 hydrogenation reaction. This interface effect is ascribed to unusual remote spillover of dissociated hydrogen species from ZnO nanoparticles to the neighboring Co oxide nanoparticles. This work clearly illustrates the equally important but opposite local and remote effects at the oxide-oxide interfaces. The distinct oxide-oxide interactions contribute to many diverse interface phenomena in oxide-oxide catalytic systems.

Silica enhanced activation and stability of Fe/Mn decorated sludge biochar composite for tetracycline degradation

In this study, SiO₂-composited biochar decorated with Fe/Mn was prepared by co-pyrolysis method. The degradation performance of the catalyst was evaluated by activating persulfate (PS) to degrade tetracycline (TC). The effects of pH, initial TC concentration, PS concentration, catalyst dosage and coexisting anions on degradation efficiency and kinetics of TC were investigated. Under optimal conditions (TC = 40 mg L^-1, pH = 6.2, PS = 3.0 mM, catalyst = 0.1 g L^-1), the kinetic reaction rate constant could reach 0.0264 min^-1 in Fe₂Mn₁@BC-0.3SiO₂/PS system, which was 12 times higher than that in the BC/PS system (0.00201 min^-1). The electrochemical, X-ray diffractometer (XRD), Fourier transform infrared spectrum (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis showed that both metal oxides and oxygen-containing functional groups provide more active sites to activate PS. The redox cycle between Fe(II)/Fe(III) and Mn(II)/Mn(III)/Mn(IV) accelerated the electron transfer and sustained the catalytic activation of PS. Radical quenching experiments and electron spin resonance (ESR) measurements confirmed that surface sulfate radical (SO₄^•-) play a key role in TC degradation. Three possible degradation pathways of TC were proposed based on high-performance liquid chromatography coupled with high-resolution mass spectrometry (HPLC-HRMS) analysis, the toxicity of TC and its intermediates was analyzed by bioluminescence inhibition test. In addition to the enhanced catalytic performance, the presence of silica also improved the stability of the catalyst, as confirmed by cyclic experiment and metal ion leaching analysis. The Fe₂Mn₁@BC-0.3SiO₂ catalyst, derived from low-cost metals and bio-waste materials, offer an environmentally friendly option to design and implement heterogenous catalyst system for pollutant removal in water.

The research on CO oxidation over Ce-Mn oxides: The preparation method effects and oxidation mechanism

A series of CeO₂-MnO_x for highly efficient catalytical oxidation of carbon monoxide were prepared by citrate sol-gel (C), hydrothermal (H) and hydrothermal-citrate complexation (CH) methods. The outcome indicates that the catalyst generated using the CH technique (CH-1:8) demonstrated the greatest catalytic performance for CO oxidation with a T₅₀ of 98 °C, and also good stability in 1400 min. Compared to the catalysts prepared by C and H method, CH-1:8 has the highest specific surface of 156.1 m² g^-1, and the better reducibility of CH-1:8 was also observed in CO-TPR. It is also observed the high ratio of adsorbed oxygen/lattice oxygen (1.5) in the XPS result. Moreover, characterizations by the TOF-SIMS method indicated that obtained catalyst CH-Ce/Mn = 1:8 had stronger interactions between Ce and Mn oxides, and the redox cycle of Mn³⁺+Ce⁴⁺ ↔ Mn⁴⁺+Ce³⁺ was a key process for CO adsorption and oxidation process. According to in-situ FTIR, the possible reaction pathway for CO was deduced in three ways. CO directly oxidize with O₂ to CO₂, CO adsorbed on Mn⁴⁺ and Ce³⁺ reacts with O to form intermediates (COO^-) (T > 50 °C) and carbonates (T > 90 °C), which are further oxidized into CO₂.

Mn anchored zeolite molecular nest for enhanced catalytic ozonation of cephalexin

The molecular nest structured catalysts have demonstrated better performance than the traditional supported catalysts. However, they have not been tried in antibiotics or other organic pollutants removal from water by advanced oxidation processes (AOPs). Here we synthesized Mn anchored zeolite molecular nest (Mn@ZN) for the catalytic ozonation of cephalexin (CLX), which is the widely used antibiotic and also a refractory pollutant in water. The ozonation catalyzed by Mn@ZN achieves 97% of CLX degradation in only 2 min and a reaction rate constant of 0.2454 L mg^-1·s^-1, which is 79.2 times higher than that of the non-catalytic ozonation. Even after ten cycles, the 0.46Mn@ZN/O₃ still achieves a CLX degradation efficiency higher than 88% in 2 min, presenting an excellent stability. Mn ions stabilized by the molecular nests facilitate Lewis acid sites and oxygen vacancies, providing active sites for O₃ sorption and decomposition into ·O^2- and ¹O₂ through electrons transfer for the radical reaction with CLX. DFT calculation indicates that both the oxygen vacancy formation energy and the O₃ adsorption energy of Mn@ZN are reduced by the Mn species introduction. This study finds a fascinating catalyst of Mn@ZN for the catalytic ozonation of antibiotics, and also a smart design strategy for zeolite confined metals catalysts for water treatment.

Effective Toluene Ozonation over δ-MnO2: Oxygen Vacancy-Induced Reactive Oxygen Species

To improve the reactivity and lifetime of catalysts in the catalytic ozonation of toluene, a simple strategy was provided to regulate the morphology and microstructure of δ-MnO₂ via the hydrothermal reaction temperature. The effects of the reaction temperature and the ozone to toluene concentration ratio on the catalyst performance were investigated. The optimized MnO₂-260 catalyst prepared at the limiting hydrothermal temperature (260 °C) showed high catalytic activity (X_Tol = 95%) and excellent stability (1200 min) at the approximately ambient temperature of 40 °C, which was superior to the results in previous studies. The structure and morphology of δ-MnO₂ were characterized by extended X-ray absorption fine structure, X-ray diffraction, scanning electron microscopy, positron annihilation lifetime spectroscopy, electron spin resonance, and other techniques. Experimental results and density functional theory calculations were in agreement that surface oxygen vacancy clusters, especially surface oxygen dimer vacancies, are critical in ozone activation. Oxygen vacancies can facilitate the adsorption and activation of O₃ to generate reactive oxygen species (ROS, including ¹O₂, O₂^-, and ^•OH), leading to superior ozonation activity to degrade toluene and intermediates. Meanwhile, free radical detection and scavenger tests indicated that ^•OH is the primary ROS during toluene ozonation rather than ¹O₂ or O₂^-.

New insight into the enhanced ozonation of malodorous compounds by Cu(II): Inhibiting the formation of free radicals to promote ozone utilization

Metal-enhanced ozonation can greatly improve the decay of organic matter; however, whether this method benefits the decay of malodorous compounds or not and the possible mechanism are not well understood. In this study, nine typical malodorous compounds were selected to reveal that Cu(II)-enhanced ozonation can greatly promote the decay of fatty amines because of the direct ozone oxidation, which was enhanced to promote ozone utilization. Moreover, trace Cu(II) can amplify the observed rate constants of dimethylamine and trimethylamine for 48.9% and 155.7%, respectively, and Cu(II) dosage was the determining factor using response surface methodology to investigate the interactions between initial pH, Cu(II) dosage and ozone dosage. These results demonstrated that the formation of ^•OH and O₂^•- was inhibited rather than promoted, which was quite different from some previously reported Cu(II)-enhanced ozonation counterparts. Moreover, the enhanced effect of trace Cu(II) was exhibited in both single and complex malodorous compounds. The conversion pathway of nitrogen and sulfur elements was clarified, with the targeted mineralization of nitrogen of nitrogen-containing malodorous compounds into NO₃-N and the odor characteristics of sulfur-containing malodorous compounds disappeared. These findings provided new insight for utilizing metal ions to enhance the direct ozone oxidation capacity of malodorous compounds.

Engineering an Enzymatic Cascade Catalytic Smartphone-Based Sensor for Onsite Visual Ratiometric Fluorescence-Colorimetric Dual-Mode Detection of Methyl Mercaptan

Precise and reliable onsite detection of methyl mercaptan (CH₃SH) is of great significance for environmental surveillance. Here, we synthesized a novel blue fluorescence nanozyme CeO₂@TPE with high peroxidase-like activity by employing aggregation-induced emission (AIE) tetraphenylethene (TPE) to embed into hollow CeO₂ nanospheres. In the presence of ethanol oxidase (AOX) and o-phenylenediamine (OPD), we engineered an enzymatic cascade activation ratiometric fluorescence-colorimetric dual-mode system AOX/CeO₂@TPE + OPD toward CH₃SH. In this design, CH₃SH initiated AOX catalytic activity to convert it into H₂O₂ for activating the peroxidase-like activity of CeO₂@TPE, producing ^•OH for oxidizing the naked-eye colorless OPD into deep yellow 2,3-diaminophenazine (DAP) with an absorption enhancement at ∼425 nm, companied by a new emission peak at ∼550 nm to match with the intrinsic emission at ∼441 nm for observing ratiometric fluorescence response, enabling a ratiometric fluorescence-colorimetric dual-mode analysis. Interestingly, both the ratiometric fluorescence and colorimetric signals could be gathered for being converted into the hue parameter on a smartphone-based sensor, achieving the onsite visual fluorescence-colorimetric dual-mode detection of CH₃SH in real environmental media with acceptable results. This study gave a novel insight into designing target-responsive enzymatic cascade activation system-based efficient and reliable dual-mode point-of-care sensors for safeguarding environmental health.

Catalysts for gaseous organic sulfur removal

Organic sulfur gases (COS, CS₂ and CH₃SH) are widely present in reducing industrial off-gases, and these substances pose difficulties for the recovery of carbon monoxide and other gases. The reaction pathways and reaction mechanisms of organic sulfur on different catalyst surfaces have yet to be fully summarized. The literature shows that many factors, such as catalyst synthesis method, loaded metal composition, number of surface hydroxyl groups, number of acid-base sites and methods of surface modification, have important effects on the catalytic performance of metal catalysts. Therefore, this paper presents a comprehensive review of the research on the application of catalysts such as zeolites, metal oxides, carbon-based materials, and hydrotalcite-like derivatives in the field of organic sulfur removal. Future research prospects are summarized, more in situ characterization experiments and theoretical calculations are needed for the catalytic decomposition of methanethiol to analyze the coke generation pathways at the microscopic level, while the simultaneous removal of multiple organic sulfur gases needs to be focused on. Based on previous catalyst research, we propose possible innovations in catalyst design, desulfurization technology and organic sulfur resource utilization technology.

Tuning the Micro-coordination Environment of Al in Dealumination Y Zeolite to Enhance Electron Transfer at the Cu-Mn Oxides Interface for Highly Efficient Catalytic Ozonation of Toluene at Low Temperatures

The development of stable, highly active, and inexpensive catalysts for the ozone catalytic oxidation of volatile organic compounds (VOCs) is challenging but of great significance. Herein, the micro-coordination environment of Al in commercial Y zeolite was regulated by a specific dealumination method and then the dealuminated Y zeolite was used as the support of Cu-Mn oxides. The optimized catalyst Cu-Mn/DY exhibited excellent performance with around 95% of toluene removal at 30 °C. Besides, the catalyst delivered satisfactory stability in both high-humidity conditions and long-term reactions, which is attributed to more active oxygen vacancies and acidic sites, especially the strong Lewis acid sites newly formed in the catalyst. The decrease in the electron cloud density around aluminum species enhanced electron transfer at the interface between Cu-Mn oxides. Moreover, extra-framework octahedrally coordinated Al in the support promoted the electronic metal-support interaction (EMSI). Compared with single Mn catalysts, the incorporation of the Cu component changed the degradation pathway of toluene. Benzoic acid, as the intermediate of toluene oxidation, can directly ring-open on Cu-doped catalysts rather than being further oxidized to other byproducts, which increased the rate of the catalytic reaction. This work provides a new insight and theoretical guidance into the rational design of efficient catalysts for the catalytic ozonation of VOCs.

Synergistic catalysis of ozonation and photooxidation by sandwich structured MnO2-NH2/GO/p-C3N4 on cephalexin degradation

Antibiotics such as cephalexin (CLX) are often detected in water and sewage, and advanced oxidation processes (AOPs) are usually the most effective method to degrade them. Currently, the synergy of AOPs has raised lively interest in water and wastewater treatment. Here the sandwiched catalyst of MnO₂-NH₂/GO/p-C₃N₄ (MN/GO/CN) is synthesized, in which graphene oxide (GO) acts as "core layer" connecting aminated MnO₂ (MnO₂-NH₂) for catalytic ozonation and proton-functionalized g-C₃N₄ (p-C₃N₄) for photocatalysis. The MN/GO/CN combines the AOPs of catalytic ozonation and photocatalysis, initiates hydroxyl radicals 4.2 times the sum of catalytic ozonation and photocatalysis, and achieves the first order kinetics constant of 2.4 × 10^-2/s, which is 2.7, 8.1 and 20.1 times that of catalytic ozonation, photo ozonation, and photocatalysis, respectively, and consequently reduces CLX from 1.0 mg/L to below the detection limit within 2.5 min, demonstrating the strong synergism between the AOPs. The sandwich structure enables GO to mediate the electron transfer between p-C₃N₄ and MnO₂-NH₂, which not only hinders electron-hole recombination on p-C₃N₄, but also speeds redox electron cycle on MnO₂ to promote the catalytic activity. The simultaneous catalytic ozonation and photocatalysis by sandwiched bifunctional catalyst to obtain synergistic effect will find its broad prospect in water and wastewater treatment.

Highly active Cs2SnCl6/C3N4 heterojunction photocatalysts operating via interfacial charge transfer mechanism

In this study, a novel lead-free perovskite heterojunction Cs₂SnCl₆/C₃N₄ composite was constructed and applied for photocatalytic NO purification. After design optimization, the Cs₂SnCl₆/C₃N₄ heterojunction exhibit excellent and stable photocatalytic NO purification ability under visible-light irradiation, which is significantly better than pristine Cs₂SnCl₆ and C₃N₄. Combined in-situ DRIFTS and electron spin resonance spin-trapping, the mechanism of Cs₂SnCl₆/C₃N₄ photocatalytic NO removal was revealed. Under visible-light irradiation, the photo-generated electrons on the conduction band of C₃N₄ would spontaneously migrate to the CB of Cs₂SnCl₆, leaving holes (h⁺) on the valence band of C₃N₄, contributing to efficiently segregated charge carriers and improved photocatalytic NO purification. Density functional theory calculations also revealed the directional electron transfer at the C₃N₄ and Cs₂SnCl₆ interface, in which the charge was migrated from C₃N₄ to Cs₂SnCl₆ induced by the internal electric field. This research sheds fresh light on the fabrication of Cs₂SnCl₆/C₃N₄ heterojunctions as well as its effective interfacial charge separation.

Evaluation of the Flexibility for Catalytic Ozonation of Dichloromethane over Urchin-Like CuMnOx in Flue Gas with Complicated Components

The evaluation of the poisoning effect of complex components in practical gas on DCM (dichloromethane) catalytic ozonation is of great significance for enhancing the technique's environmental flexibility. Herein, Ca, Pb, As, and NO/SO₂ were selected as a typical alkaline-earth metal, heavy metal, metalloid, and acid gas, respectively, to evaluate their interferences on catalytic behaviors and surface properties of an optimized urchin-like CuMn catalyst. Ca/Pb loading weakens the formation of oxygen vacancies, oxygen mobility, and acidity due to the fusion of Mn-Ca/Pb-O, leading to their inferior catalytic performance with poor CO₂ selectivity and mineralization rate. Noticeably, the presence of As induces excessively strong acidity, facilitating the inevitable formation of byproducts. Catalytic co-ozonation of NO/DCM is achieved with stoichiometric ozone addition. Unfortunately, SO₂ introduction brings irreversible deactivation due to strong competition adsorption and the loss of active sites. Unexpectedly, Ca loading protects active sites from an attack by SO₂. The formation of unstable sulfites and the released Mn-O structure offset the negative effect from SO₂. Overall, the catalytic ozonation of DCM exhibits a distinctive priority in the antipoisoning of metals with the maintenance of DCM conversion. The construction of more stable acid sites should be the future direction of catalyst design; otherwise, catalytic ozonation should be arranged together with post heavy metal capture and a deacidification system.

Self-Accelerating Interfacial Catalytic Elimination of Gaseous Sulfur-Containing Volatile Organic Compounds as Microbubbles in a Facet-Engineered Three-Dimensional BiOCl Sponge Fenton-Like Process

The elimination of gaseous sulfur-containing volatile organic compounds (S-VOCs) by a microbubble-assisted Fenton-like process is an innovative strategy. Herein, we established a microbubble-assisted Fenton-like process to eliminate malodorous microbubble CH₃SH as representative gaseous S-VOCs, in which BiOCl nanosheets loaded on a three-dimensional sponge were exposed to (001) or (010) facets and induced Fenton-like interface reactions. Intriguingly, the microbubble-assisted Fenton-like process significantly removed 99.9% of CH₃SH, higher than that of the macrobubble-assisted Fenton-like process (39.0%). The self-accelerating interfacial catalytic mechanism was in-depth identified by in situ ATR-FTIR, PTR-TOF-MS, EPR, and DFT computational study. The extraordinary elimination performance of microbubble-assisted Fenton-like process lies in the enhancing dissolution/mass transfer of gaseous CH₃SH in the gas/liquid phase and the tight contact between CH₃SH-microbubbles and 3D-BiOCl sponge due to the low rising velocity (0.13 mm s^-1) and negative charge (-45.53 mV) of CH₃SH-microbubbles, as well as the effective generation of ¹O₂ by activating the enriched dissolved oxygen in CH₃SH-microbubble via effective electron-polarized sites on 3D-BiOCl sponge. Furthermore, CH₃SH-microbubbles transferred electrons to H₂O₂ through electron-rich oxygen vacancy centers of the 3D-BiOCl sponge to generate more •OH, thus achieving excellent elimination performance. Overall, this study demonstrates the enhanced self-accelerating interfacial catalytic elimination by S-VOC microbubble and provides the underlying mechanisms.

Boosting SO2-Resistant NOx Reduction by Modulating Electronic Interaction of Short-Range Fe-O Coordination over Fe2O3/TiO2 Catalysts

SO₂-resistant selective catalytic reduction (SCR) of NO_x remains a grand challenge for eliminating NO_x generated from stationary combustion processes. Herein, SO₂-resistant NO_x reduction has been boosted by modulating electronic interaction of short-range Fe-O coordination over Fe₂O₃/TiO₂ catalysts. We report a remarkable SO₂-tolerant Fe₂O₃/TiO₂ catalyst using sulfur-doped TiO₂ as the support. Via an array of spectroscopic and microscopic characterizations and DFT theoretical calculations, the active form of the dopant is demonstrated as SO₄^2- residing at subsurface TiO₆ locations. Sulfur doping exerts strong electronic perturbation to TiO₂, causing a net charge transfer from Fe₂O₃ to TiO₂ via increased short-range Fe-O coordination. This electronic effect simultaneously weakens charge transfer from Fe₂O₃ to SO₂ and enhances that from NO/NH₃ to Fe₂O₃, resulting in a remarkable "killing two birds with one stone" scenario, that is, improving NO/NH₃ adsorption that benefits SCR reaction and inhibiting SO₂ poisoning that benefits catalyst long-term stability.

Catalytic ozonation of CH2Cl2 over hollow urchin-like MnO2 with regulation of active oxygen by catalyst modification and ozone promotion

This paper firstly reported efficient catalytic ozonation of CH₂Cl₂ (dichloromethane, DCM) at low temperature over hollow urchin-like MnO₂ with high chlorine resistance. Regulations on morphologies and Cu doping, as well as ozone promotion were conducted to optimize active oxygen of MnO₂ catalysts, contributing to excellent catalytic behaviors. Cu doping MnO₂ with hollow urchin-like morphology attained a stable 100% DCM conversion with O₃/DCM molar ratio of 10 at 120 °C. The ozone utilization rate, final products, and byproducts distribution were discussed. Abundant crystal defects, low-valance Mn/Cu, O_ads, and weak acidity, as well as better low temperature reducibility contributed to its superior performance. During DCM catalytic ozonation, DCM oxidation exhibited competitive effect on O₃ decomposition due to the occupation of intermediates (CH₂ClO₃·, O-CH₂Cl, and O-CH₂ -O) over active sites that should belong to O₃ originally. Nevertheless, O₃ decomposition exhibited synergistic effects on DCM oxidation with promotion on active oxygen. Density functional theory (DFT) calculations confirmed the positive effect on oxygen vacancy formation and O₃/DCM adsorption from Cu doping. The possible mechanism for DCM catalytic ozonation included four parts, including O₃/DCM adsorption, O₃ activation, DCM oxidation, and electron replenishment. This paper provides new insight for catalytic elimination of chlorinated alkanes at mild conditions.