Outstanding Stability and Enhanced Catalytic Activity for Toluene Oxidation by Si–O–Mn Interaction over MnOx/SiO2

Weakening the Mn-O-Si Interaction via Carbon Intercalation for the Enhanced Catalytic Ozonation of Refractory Pollutants in Environmental Matrices

The strong metal-support interaction (MSI) has been widely attributed to enhanced catalytic activity. However, this attribution might be wrong in catalytic ozonation, since MSI that is too strong might impede the activation of electron-poor ozone molecules. Herein, we reported a strategy to subtly modulate the Mn-O-Si interaction by intercalating the carbon film between the silica support and active manganese oxide. When using MnOx/0.5C/SiO2 with the moderate MSI as a catalyst in the catalytic ozonation of refractory paracetamol (PCM), 91.1 ± 2.4% of PCM was removed within 30 min, about 30% higher than that using the catalyst of MnOx/SiO2 with a strong MSI. Moreover, the reaction rate reached 8.01 × 10-2 min-1, 2.2 and 1.3 times that with MnOx/SiO2 and MnOx/1C/SiO2, respectively. Importantly, further integration of MnOx/0.5C/SiO2 into membrane filtration achieved high rejections of PCM (>94.3%) under various realistic water scenarios during a continuous 12 h operation, demonstrating strong resistance to environmental matrices interference. Experimental and theoretical evidence revealed that the moderate MSI resulted in the high dispersion of active MnOx nanoclusters in the size of 2.3-4.4 nm and promoted the adsorption of ozone over MnOx and its dissociation into surface *O, •OH, •O2-, and 1O2 for decontamination. As a constructive work, this study revealed the significance of MSI in catalytic ozonation and offered a simple regulation method for constructing active interfaces of metal-supported catalysts.

Recent Advances of the Effect of H2O on VOC Oxidation over Catalysts: Influencing Factors, Inhibition/Promotion Mechanisms, and Water Resistance Strategies

Water vapor is a significant component in real volatile organic compounds (VOCs) exhaust gas and has a considerable impact on the catalytic performance of catalysts for VOC oxidation. Important progress has been made in the reaction mechanisms of H2O and water resistance strategies for VOC oxidation in recent years. Despite advancements in catalytic technology, most catalysts still exhibit low activity under humid conditions, presenting a challenge in reducing the adverse effects of H2O on VOC oxidation. To develop water-resistant catalysts, understanding the mechanistic role of H2O and implementing effective water-resistance strategies with influencing factors are imperative. This Perspective systematically summarizes related research on the impact of H2O on VOC oxidation, drawing from over 390 papers published between 2013 and 2024. Five main influencing factors are proposed to clarify their effects on the role of H2O. Five inhibition/promotion mechanisms of H2O are introduced, elucidating their role in the catalytic oxidation of various VOCs. Additionally, different kinds of water resistance strategies are discussed, including the fabrication of hydrophobic materials, the design of specific structures and morphologies, and the introduction of additional elements for catalyst modification. Finally, scientific challenges and opportunities for enhancing the design of efficient and water-resistant catalysts for practical applications in VOC purification are highlighted.

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.

Roles of Oxygen Species in Low-Temperature Catalytic o-Xylene Oxidation on MOF-Derived Bouquetlike CeO2

To realize efficient low-temperature catalytic o-xylene oxidation, MOF-derived CeO₂-X catalysts were prepared via the pyrolysis of MOF precursors with different ratios of cerium nitrate to trimesic acid. Among the synthesized catalysts, the bouquet like CeO₂-1 exhibited the best activity with T₅₀ and T₉₀ of 156 and 198 °C and the lowest activation energy of 60.67 kJ·mol^-1 (WHSV= 48 000 mL·g^-1·h^-1, o-xylene concentration = 500 ppm). o-Xylene was completely mineralized, and no change in conversion efficiency or CO₂ yield was found at 5 vol % H₂O for over 50 h. The rich active oxygen species (XPS: O_sur/O_latt = 0.69) and abundant oxygen vacancies (Raman: I_D/I_F2g = 0.036) of CeO₂-1 made crucial contribution to its superior catalytic activity. The O₂-TPD and H₂-TPR results confirmed that CeO₂-1 had more surface active oxygen and better mobility of bulk oxygen. Moreover, the reaction routes under different atmospheres were probed through in situ DRIFTS, in which oxygen vacancy played a key role in promoting the adsorption and activation of molecular oxygen and facilitating the migration of the bulk lattice oxygen.