The simultaneous catalytic oxidation of volatile organic compounds (VOCs) and NO in flue gas is challenging due to the inherent difficulties of activating inert lattice oxygen and the scarcity of active sites. To address this challenge, a series of Mn-Co-Ce composite oxide catalysts (MnaCobCecOx) were successfully synthesized and revealed that the co-introduction of Ce and Co induced profound lattice distortion and optimized electronic structure, in which Mn-O bond served as a pivotal electron bridge in the trimetallic Mn5Co4Ce3Ox catalyst. This distortion directly weakened metal-oxygen bond strengths, thereby unlocking lattice oxygen and generating abundant active sites for the simultaneous oxidation of toluene and NO. The optimized Mn5Co4Ce3Ox catalyst achieved nearly 90% toluene conversion and 100% NO conversion with high CO2 and NO2 selectivity at 220 degrees C and markedly alleviated competitive adsorption, outperforming Ce3Co4Ox, Mn5Co4Ox, and Mn5Ce3Ox. In situ DRIFTS substantiated the simultaneous oxidation mechanism of NO and toluene over Mn5Co4Ce3Ox, identifying the ring-opening of benzoic acids as the rate-limiting step. This study offers prospective guidance for the design of economical and highly active catalysts to treat VOCs and NO emissions via boosting lattice oxygen activation and active sites generation.

Volatile organic compounds (VOCs), with great harm to environment and human health, have been regarded as the main focus of air pollution control. Catalytic oxidation is acknowledged as an effective and eco-friendly approach for VOCs abatement, and how to design effective catalysts with superior low-temperature catalytic activity is the core. Oxygen vacancy (Ov) engineering has been proven to boost the interior catalytic activity of metal oxides-based catalysts. In this review, the latest advances in developing Ov-enriched catalysts for efficient VOCs oxidation are summarized systematically. Key topics addressed include: (i) the classification and characteristics of Ov, (ii) the catalytic roles of Ov, emphasizing their synergistic effects with other active sites, (iii) the main characterization methods for Ov, and (iv) rational construction strategy of Ov in metal oxides-based catalysts. Furthermore, current challenges and further perspectives regarding developing catalysts with abundant Ov are also discussed. This work aims to provide a fundamental and mechanistic insight into the underlying mechanism of Ov in catalytic oxidation and directional guidance for the development of effective Ov-enriched catalysts.

Electrically driven catalysis has been considered as an advanced technique for volatile organic compound degradation. Nevertheless, a definitive understanding of the non-thermal contributions of the electric field effect within this catalytic system remains to be elucidated. In this investigation, a cobalt substituted copper foam monolithic catalyst (CoCuOx) achieves the most efficient toluene degradation compared to Co3O4/CuOx and CuOx, at ultra-low temperatures in an electric field (T93 = 178 ℃) for the efficiency in charge separation and electron transfer over a homogeneous surface. The characterization results show that the partial electron transfer between Cu and Co cations by bridged oxygen species is boosted by the electric field effect. The oxygen transient experiment and theoretical calculations illustrate that the electrically driven catalytic reaction conforms to the typical MvK mechanism, and the electric field accelerates migration and supplementary of lattice oxygen species, resulting in an increase in oxygen vacancy concentration. This intensified migration behaviour of lattice oxygen may constitute the functional core of the electric field effect. Furthermore, an alternative reaction route directly attacking the bonds of aromatic hydrogens (C-H) and benzene rings is also induced by additional energy input, electron transfer, and lattice oxygen activation. This work offers insights into the impact of electric field on the toluene catalytic degradation, which might guide the electrically driven catalysis for VOCs treatment in non-hyperthermic environments.

Volatile organic compounds (VOCs) pose severe threats to both ecosystems and human health, making the development of efficient, energy-saving degradation technologies imperative. Photothermal catalysis (PTC), which integrates photocatalysis (PC) with thermocatalysis (TC), has emerged as a promising and sustainable strategy for VOCs degradation. The synergistic effect facilitates high-efficiency VOCs degradation at relatively mild temperatures. Carbon-based materials exhibit immense potential in this field due to their superior broad-spectrum light absorption, high photothermal conversion efficiency, large specific surface areas, and tunable electronic and surface chemical properties. However, systematic reviews elucidating the synergistic photothermal effects of carbon-based materials in VOCs degradation remain scarce. Consequently, this article comprehensively reviews recent advances in carbon-based photothermal catalysts for VOCs degradation. Firstly, we discuss the characteristics of various carbon-based materials, highlighting their structural features, photothermal conversion capabilities, and physicochemical properties, as well as their specific roles in enhancing degradation processes. Subsequently, the impacts of modification strategies (including heteroatom doping, active component loading, structural morphology regulation, and defect engineering) and reaction conditions on catalytic activity are examined. Crucially, the reaction mechanisms of PC, TC, and their synergistic effects are explored in depth, with particular emphasis on how carbon-based materials enhance light absorption, promote charge separation, induce localized thermal effects, and regulate reaction pathways. Eventually, this review summarizes current applications, identifies existing challenges, and proposes future research directions, aiming to provide a theoretical foundation and technical guidance for designing efficient, stable, and cost-effective carbon-based photothermal catalysts.

Monolithic catalysts offer distinct advantages, including efficient mass transport, robust mechanical strength, and negligible pressure drop during operation. Developing such catalysts capable of efficient low-temperature volatile organic compounds (VOCs) removal remains a critical challenge in air pollution control. Herein, we propose a series of monolithic CoCuOx catalysts that were successfully prepared by combining hydrothermal ionexchange and in situ redox on Cu foam for efficient low-temperature catalytic oxidation of toluene. This simplified approach enables the substitution of Cu atoms by Co atoms based on Cu(OH)2 hydroxyl interfaces. Co species incorporation acted as a crucial actuation, triggering a beneficial evolution of material phase, surface morphology, and crystal structure. Experimental and theoretical investigations reveal that this evolution triggers synergistic effects in both electronic and structural properties critical for catalysis, manifested specifically in electron transfer and redistribution, tuned intermetallic interactions, varied surface vacancy concentrations, enhanced low-temperature reducibility, and optimized oxygen species reactive properties. The 4-CoCuOx catalyst demonstrated the highest activity (T90 = 228 degrees C) and exhibited excellent stability under a few practical scenarios. Without the guiding Cu(OH)2 nanorod interface, the in situ grown 4-Co3O4/CuOx catalyst lacks the structural template for ordered Co substitution, resulting in its suboptimal catalytic performance. Furthermore, cobalt substitution achieved the ring-opening of toluene at low temperatures crucially, which overcame the bottleneck in the rate-determining step (benzoic acid to maleic anhydride). This work offers a new direction for the rational design and optimization of monolithic catalysts for controlling VOCs emissions.

Manipulating multi-metal interactions in spinel oxides offers great opportunities to develop highly efficient and robust catalysts for volatile organic compounds (VOCs) oxidation, but such potential remains largely unexploited or even causes suppressed activity due to the ambiguity in rational design metallic interactions and the poor understanding of the origins of metallic synergy. Herein, by fine-tuning cation distributions via pyrolysis metal-organic frameworks (MOFs), the geometric-site-dependent superexchange interactions in typical Mn-Cu spinel oxides were tailored and served as the ideal model to probe their intriguing roles and underlying mechanisms in toluene oxidation. The Mnoct-O-Cutet interactions (Mn in octahedra while Cu in tetrahedra) induced an impressive five-fold increase in toluene specific reaction rate, a four-fold increase in turnover frequency, and remarkably declined apparent activation energy from 71.0 to 41.0 kJ & sdot;mol-1 as compared to Mn3O4. However, the Mnoct-O-Cuoctinteractions (Mn and Cu in octahedra) showed the unexpected opposite behavior and deteriorated the toluene specific reaction rate by 42 % and the turnover frequency by 18 %. In-depth experimental analyses and theoretical calculations revealed that Mnoct-O-Cutet triggered superexchange valence redistribution and electron delocalization, contributing to enhanced surface lattice oxygen activation. In contrast, the electronic interactions in Mnoct-O-Cuoct unit decreased the energy difference between Mnoct 3d and O 2p band centers and hence strengthened Mnoct-O covalence. This work highlights that not only the metallic combination but also the cation distributions should be carefully considered when designing polymetallic spinels, and provides fundamental insights into the origins of site-dependent metallic interactions in spinels, which sheds light on the rational design of polymetallic spinel oxides with optimized superexchange interactions and reinforced catalytic activities for VOCs treatment.

In this paper, Co-Mn-Ce trimetallic oxides fortified biochar catalyst (XCoaMnbCec@BAC) was designed to upgrade oxygen vacancy and reducibility for enhancing toluene and Hg0 oxidation activities and lowering catalytic temperature. 10 %Co0.3Mn0.2Ce0.5@BAC exhibited excellent Etoluene and EHg alongside with superior SO2 and H2O resistance at 160-400 degrees C, acquiring EHg of 96.6 % and Etoluene of 95.9 % with CO2 selectivity of above 85 % at 240 degrees C under a space velocity of about 16000 h-1. Toluene exerted a dose-dependent inhibitory effect on Hg0 purification, while Hg0 imposed almost no effect on toluene purification. The interaction among Co, Mn and Ce together with the structure-activity relationship was synthetically delved. 10 %Co0.3Mn0.2Ce0.5@BAC combined the merits of BAC and Co-Mn-Ce synergistic effect. Diverse characterizations behaved heteroatom interdoping could emerge robust synergistic effects, which induced lattice defects, created oxygen vacancies, enhanced reducibility and elevated the electronic transfer. Moreover, hierarchical porous biochar carrier with natural hydrophobic properties not only provided big surface area, high total pore volume and active interfaces, exposing plentiful active sites, but also held appropriate microporous - mesoporous - macroporous distribution, which facilitated the convenient diffusion and mass transfer. These profitable factors collectively contributed to the outstanding low-temperature catalytic activity towards toluene and Hg0 oxidation. The unsaturated Co, Mn, and Ce cations as Lewis acid sites functioned as effective active centers, facilitating the activation and oxidation of both pollutants. Meanwhile, oxygen vacancies served as dynamic channels for regenerating and transferring reactive oxygen species (ROSs).

A series of Ce and La co-doped CoOx anchored graphitized biochar catalysts (XLayCezCo1-y-z/BCs) were successfully synthesized for low-temperature synchronous abatement of Hg-0 and chlorobenzene (CB). XLayCezCo1-y-z/BCs combined the merits of three-dimensional porous (3DP) graphitized biochar and the collectively synergistic effects from La, Ce and Co interactions. 10%La0.2Ce0.3Co0.5/BC achieved excellent CB removal efficiency (E-CB) and Hg-0 removal efficiency (E-Hg) at 160 similar to 400 degrees C, with E-CB of above 90% and E-Hg of 95% at 280 degrees C. Compared with 10%La0.4Ce0.6/BC and 10%Co/BC, 10%La0.2Ce0.3Co0.5/BC exhibited a higher proportion of Co3+ species, bigger O-alpha/O-total ratio, better metal oxide dispersion, and superior H2O/SO2 tolerance, which resulted from the strong synergistic effects among its ternary components. Comprehensive characterizations revealed that the co-doping of La and Ce into CoOx not only regulated and optimized acidity-redox properties, but also induced additional lattice defects and oxygen vacancies, boosted the activation of Co3+/Co2+ redox couples, facilitated the migration and release of reactive oxygen species (ROSs), thereby accelerating CCl bond cleavage and CB' benzene ring opening. The 3DP graphitized biochar enormously enhanced its thermal stability, provided a large surface area and exposed more active sites, strengthened reactants-catalyst interactions and efficient mass transfer, reduced the deposition of chlorine-containing by-products, favoring its activity, stability and Cl-resistance. The oxidation path of CB on 10%La0.2Ce0.3Co0.5/BC occurred via chlorobenzene -> phenolates -> maleates -> formates/acetates -> CO2 and H2O. This work thus provides significant theoretical and experimental support for the simultaneous abatement of CB and Hg-0.

Environmental pollutants, including volatile organic compounds (VOCs), characterized by their high volatility, toxicity, and diffusivity, pose significant threats to both human health and ecological systems. Among the numerous environmental remediation technologies, catalytic reactions have emerged as a crucial approach for pollutant treatment, leveraging their advantages such as high efficiency and continuous operation. Nevertheless, traditional catalytic technologies suffer from issues like insufficient catalyst activity and stability. Applying catalytic reactions enhanced by magnetic fields in environmental catalysis has proven to be a promising method, garnering significant attention due to its advantages of environmental friendliness and unique catalytic properties. However, the processes and mechanisms underlying magnetic catalysis remain insufficiently explored. This review presents a systematic synthesis of recent progress in magnetic catalysis, systematically discusses the fundamental principles of magnetic fields, as well as the mechanism driving magnetic catalysis. Furthermore, the review comprehensively summarizes the technological advantages and recent advancements in implementing magnetic catalysis for the degradation of diverse environmental pollutants, with a particular emphasis on VOCs as a representative category. Additionally, the work explores future development strategies for magnetic catalysis through the lenses of technical economic analysis (TEA), life cycle assessment (LCA), and machine learning (ML). Finally, the current limitations and challenges in this field are discussed. This review focuses on providing a scientific basis for magnetic catalysis-based environmental remediation. It is hoped that this paper will offer references for the research and technological development in the field of magnetic catalysis, and simultaneously provide different perspectives for in-depth exploration of pathways to improve catalytic efficiency.

Defect engineering has recently emerged as a pivotal strategy in the design of perovskite catalysts. Atomic disorder at grain boundaries, characterized by abundant coordinatively unsaturated atoms and oxygen vacancies, generates active sites that facilitate reactant adsorption and activation. However, the concurrent catalytic removal of toluene and chlorobenzene on perovskite catalysts, along with their mutual influence and interaction mechanisms, remains inadequately elucidated. Consequently, the rational design of LaCoO3 catalysts with controlled grain boundary structures represents a significant research challenge. In this research, we developed a one-pot, urea-modified LaCoO3 perovskite catalyst that enables in-situ regulation of lanthanum vacancies (VLa) and promotes grain boundary growth. We elucidated the fundamental relationship between grain boundary density and oxygen adsorption capacity in LaCoO3 and employed the catalyst for the simultaneous oxidation of chlorobenzene and toluene. Moderate urea modification induced La vacancies at the grain boundaries, providing a driving force for complex structural reconstruction, while the grain boundaries accommodated these vacancies and associated lattice distortions. The abundant grain boundaries facilitated the adsorption and activation of chlorobenzene, toluene, and O2, which is critical for the Mars-van Krevelen mechanism. Furthermore, these boundaries could effectively host or disperse chlorine species, thereby mitigating catalyst deactivation. As a result, LaCoO3-2U exhibited superior low-temperature activity, reducing the temperature required for 90% chlorobenzene conversion (T90) by more than 45 °C compared to the unmodified perovskite, while also accelerating the deep oxidation of chlorinated byproducts. These findings highlight the critical role of rational A-site defect engineering in the design of efficient catalysts for the abatement of chlorinated and non-chlorinated volatile organic compounds (CVOCs and VOCs).

A suite of CrCe oxides facilitated hierarchical porous biochars from walnut husks and rice straws (XCryCe1-y/WSAC) were readily synthesized for formaldehyde (HCHO) abatement. BET, XRD, XPS, SEM, H2-TPR, TG-DTG, and in situ DRIFTS were adopted to disclose their physicochemical properties and the elimination mechanism of HCHO. 18

The removal of volatile organic compounds (VOCs) from sulfur-containing industrial flue gas is a significant challenge due to the rapid deactivation of catalysts by sulfur dioxide (SO2) through sulfation, which impedes VOCs oxidation. To address this issue, we developed a CuCeOx-NP catalyst with tunable acidity and alkalinity via in-situ Cu doping with varying contents, achieving remarkable sulfur resistance and stability. The CuCeOx-1-NP catalyst, featuring dual sites, exhibited superior performance (T90 = 226 degrees C) in the presence of 600 ppm SO2, surpassing conventional catalysts. Through in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) and density functional theory (DFT) calculation. It is elucidated that copper modification can adjust the acidity and alkalinity of the catalyst surface, protecting the cerium active component from sulfation and thereby facilitating the oxidation reaction of toluene. This study not only provides insights into the role of Cu modification in enhancing the sulfur resistance of cerium-based catalysts but also lays the groundwork for the design of next-generation, efficient, sulfur-resistant catalysts for industrial VOCs oxidation applications.

Biomass pellet fuel is widely recognized as a mature and affordable pathway for sustainable energy utilization. However, the application of biomass as a fuel is often limited by the emission of volatile organic compounds (VOCs) resulting from incomplete combustion. In this study, a strategy based on ion-exchange modified bone char (a bio-hydroxyapatite material) was proposed for the efficient catalytic oxidation of toluene at 220 degrees C. Comprehensive characterization revealed that a high level of ion exchange facilitated the transformation of alpha-MnO2 into amorphous MnO2, thereby enhancing lattice oxygen activity and oxygen activation performance, which ultimately promoted low-temperature catalytic performance. Moreover, elevated ion-exchange levels enhanced the metal-support interaction (MSI), thereby improving catalyst stability in the presence of H2O and SO2, which are typically present in biomass combustion flue gas. This work provides a technical pathway for the utilization and recycling of two bioresources, contributing to the realization of Sustainable Development Goals (SDGs) 7 and 12.

Carbon materials have been employed in many applications in flue gas purification due to their high specific surface area, good chemical inertness, and tunable surface chemistry. However, traditional methods such as adsorption or metal-loaded catalysis can be financially burdensome. The surface of carbon materials contains abundant vacancies, interstitial atoms, boundaries, and other defects. These structural defects are often modified with saturated or unsaturated functional groups containing heteroatoms such as oxygen, nitrogen, etc., thus possessing a certain acid–base property and redox ability, which makes the carbon materials themselves have some catalytic activity. The metal-free carbon catalytic purification of flue gas pollutants offers a promising solution to improve removal efficiency while reducing costs significantly. This review examines the research on carbon materials for the removal of flue gas pollutants, presenting recent advancements in carbon catalysis purification of NOx, SO2, and VOCs. It analyzes the critical properties of carbon materials that govern carbon catalytic efficiency, such as surface functional groups, surface defects, and pore structure. Finally, it summarizes methods for regulating these properties to achieve higher efficiencies in the metal-free carbon-catalyzed purification of flue gas pollutants.

The catalytic oxidation of chlorobenzene by alpha-MnO2 has received much attention due to its excellent redox capacity. However, the differences in the catalytic activities of alpha-MnO2 with different morphologies in chlorobenzene and how to improve their chlorine resistance have not been fully explored. In this paper, a variety of alpha-MnO2 with different morphologies were prepared by hydrothermal and co-precipitation methods and examined for their catalytic performance in chlorobenzene oxidation, from which rod-like alpha-MnO2 was selected as a matrix candidate and modified with different contents of Co to further enhance its catalytic performance. The loading of Co elevated the activity and CO2 yield of alpha-MnO2 and retarded its deactivation process in durability tests. In addition, the Co-modified alpha-MnO2 nanorods exhibited better resistance to SO2, NO, toluene, and H2O at high temperatures, with versatile applicability to actual complex flue gas conditions. Characterization of the physicochemical properties showed that the introduction of Co increased the reduction capacity, the content and mobility of surface reactive oxygen species, and the acidity of alpha-MnO2 (especially the medium-strong acidic sites), which synergistically contributed to the enhancement of the catalytic performance. It was concluded that the deactivation of the catalyst was associated with adsorption of Cl-containing species and coke deposition on its surface. Possible degradation pathways of CB on the prepared catalysts were explored through in situ DRIFTS technology. This paper presents the loading of Co on alpha-MnO2 nanorods is a promising strategy for the design of cost-effective and high-performance Mn-based catalysts for the catalytic oxidation of CVOCs.

This review summarizes the characteristics, deactivation pathways, and design strategies of Mn-based catalysts for the catalytic oxidation of CVOCs. The objective is to provide insights for the development of highly efficient Mn-based catalysts.

The thermal stability of carbon-based catalysts remains a tremendous obstacle that deters their practical applications under high temperature range. Herein, a battery of MnCoOx supported hierarchical porous biochars with CeO2 encapsulation (MnCo/CeO2@BAC) were facilely fabricated for toluene degradation. The strategy of CeO2 encapsulation can prevent biochars from high temperature damage and emerging hydrogen bonding with interfacial H2O, thereby strengthening the thermal stability and H2O resistance of catalysts. The intrinsic relationship between catalytic activities and their physicochemical features was systematically comprehended via diverse characterization techniques. 10 %Mn0.5Co0.5/CeO2@BAC manifested surpassing activity, outstanding mineralization rate, satisfactory thermal stability, and preeminent SO2 and H2O toleration at a broad temperature interval. The impacts of O2, SO2 and H2O on toluene purification over 10 %Mn0.5Co0.5/CeO2@BAC were delved, thereinto, SO2 and H2O exhibited prohibitive effects on toluene abatement, whereas O2 demonstrated stimulative influence on toluene elimination. In contrast to 10 %Mn/CeO2@BAC and 10 %Co/CeO2@BAC, 10 % Mn0.5Co0.5/CeO2@BAC rendered superior catalytic performance due to bimetallic cooperative effect, superior redox property, more oxygen vacancies and lattice defects, higher proportions of Mn4 + and Co3+, larger Oads/ Olatt ratio and better metal oxide dispersion. Based on characterization results, chemically adsorbed oxygen dominated toluene adsorption and partial oxidation, while lattice oxygen was largely responsible for its deep oxidation.

Manganese-based mullite (AMn(2)O(5)) catalysts are promising for the catalytic oxidation of VOCs, with their oxidation reaction performance being tunable by modifying the composition of the A-site elements. In this work, various manganese-based mullite catalysts (Gd0.9X0.1Mn2O5, X =Sr, Ce, or Ca) with different A-site elements doping were prepared by the citric acid sol-gel method and applied to the catalytic oxidation of toluene. The activity tests indicated that the enhancement of catalytic performance by doping elements was in the order of Sr > Ce > Ca. Notably, the T-90 of the Gd0.9Sr0.1Mn2O5 catalyst was 235.6 degrees C, a lower 37.8 degrees C than that of the GdMn2O5. Comprehensive characterization and density functional theory (DFT) simulations revealed that Sr doping facilitates the reduction of Mn4+ to Mn3+, increases the electron occupancy of the e(g) orbitals in octahedral Mn sites, and elevates the Mn-d band center, thus facilitating the adsorption and activation of O-2. Additionally, the raised O-p band center caused by Sr doping enhances lattice oxygen mobility. In situ DRIFTS analysis indicated that the introduction of Sr at the A-site optimizes the toluene reaction pathway and accelerates the reaction rate. This work reveals that a simple A-site cation doping strategy can effectively regulate manganese-based mullite catalysts' electronic structure and surface reaction activity, providing a feasible method for the large-scale preparation of manganese-based mullite catalysts with excellent catalytic performance.