Catalytic oxidation of toluene using a facile synthesized Ag nanoparticle supported on UiO-66 derivative

Manganese-cerium composite oxide pyrolyzed from metal organic framework supporting palladium nanoparticles for efficient toluene oxidation

Manganese-cerium metal oxide with flocculent structure prepared via the pyrolysis of Mn/Ce-MOF and supported Pd were applied for the catalytic oxidation of toluene. The Pd/Mn3Ce2-300 catalyst could completely oxidize toluene at 190 °C, which presented excellent catalytic performance. Moreover, Pd/Mn3Ce2-300 possessed great reusability, stability and water resistance even under 10 vol% water vapors. A series of characterizations including X-ray diffraction (XRD), N₂ adsorption-desorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and H₂ temperature programmed reduction (H₂-TPR) were used to investigate the physicochemical properties of the samples. It was found that Pd/Mn3Ce2-300 possessed a better reduction ability at low temperature, more surface absorbed oxygen and surface Pd species, and a strong interaction between Pd and Mn3Ce2-300, resulting in great catalytic performance for toluene degradation.

A novel cellulose hydrogel coating with nanoscale Fe0 for Cr(VI) adsorption and reduction

A novel cellulose hydrogel coating nanoscale Fe⁰ (CH@nFe⁰) was synthesized and utilized to improve the dispersibility and oxidation resistance of nFe⁰. The composition and structure of CH@nFe⁰ were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) before and after its reaction with Cr(VI). The performance of CH@nFe⁰ in the removal of Cr(VI) was evaluated through a comparative experiment between nFe⁰ and CH. The influence of the initial concentration of Cr(VI), temperature, dosage, and the initial pH of the solution were also evaluated in this reaction system. The results showed that CH@nFe⁰ allowed a higher Cr(VI) removal rate compared to nFe⁰ and CH. This might have derived from an enhanced reduction and adsorption of Cr(VI) by CH. Meanwhile, the network structure of the cellulose hydrogel served as a mass-transfer channel between Cr(VI) and nFe⁰. In addition, the increase of the initial solution pH minimized the removal of Cr(VI). This mechanism revealed that CH coating resulted in an enhancement of the adsorption capability and reducibility of CH@nFe⁰ with respect to Cr(VI). The CH@nFe⁰ composite is characterized by an advantageous mesoporous network structure and functional groups of amide and carboxylic acid, which provide additional active sites and promote mass transfer. This new three-dimensional (3-D) cellulose hydrogel coating containing nFe⁰ can be effectively used for the removal of Cr(VI) ions from aquatic environments.

Abatement of Toluene Using a Sequential Adsorption-Catalytic Oxidation Process: Comparative Study of Potential Adsorbent/Catalytic Materials

A novel strategy for toluene abatement was investigated using a sequential adsorption-regeneration process. Commercial Hopcalite (CuMn2Ox, Purelyst101MD), Ceria nanorods, and UiO-66-SO3H, a metal–organic framework (MOF), were selected for this study. Toluene was first adsorbed on the material and a mild thermal activation was performed afterwards in order to oxidize toluene into CO2 and H2O. The materials were characterized by XRD, N2 adsorption-desorption analysis, H2-TPR and TGA/DSC. The best dynamic toluene adsorption capacity was observed for UiO-66-SO3H due to its hierarchical porosity and high specific surface area. However, in terms of balance between storage and catalytic properties, Hopcalite stands out from others owing to its superior textural/chemical properties promoting irreversible toluene adsorption and outstanding redox properties, allowing a high activity and CO2 selectivity in toluene oxidation. The high conversion of toluene into CO2 which easily desorbs from the surface during heating treatment shows that the sequential adsorption-catalytic thermal oxidation can encompass a classical oxidation process in terms of efficiency, CO2 yield, and energy-cost saving, providing that the bifunctional material displays a good stability in repetitive working conditions.

Insights into the Adsorption of VOCs on a Cobalt-Adeninate Metal-Organic Framework (Bio-MOF-11)

With increasingly severe air pollution brought by volatile organic compounds (VOCs), the search for efficient adsorbents toward VOC removal is of great significance. Herein, an adenine-based metal-organic framework, namely, bio-MOF-11 [Co₂(ad)₂(CH₃CO₂)₂·0.3EtOH·0.6H₂O, ad = adeninate], was synthesized via a facile method, and its VOC adsorption was reported for the first time. This novel bio-MOF-11 was investigated by employing four common VOCs (i.e., methanol, acetone, benzene, and toluene) as adsorbates. The saturated adsorption capacity of these targeted VOCs on bio-MOF-11 was estimated to be 0.73-3.57 mmol/g, following the order: toluene < benzene < acetone < methanol. Furthermore, with the adsorption temperature increasing from 288 to 308 K, the saturated adsorption capacity was reduced by 7.3-35.6%. It is worth noting that acetone adsorption is most sensitive to temperature ascribed to its low boiling point and strong polar nature. Meanwhile, owing to the molecular sieve effect, the adsorption capacity appears negatively correlated to the size of VOC molecules. Besides, the abundant exposed nitrogen atoms and amino groups in bio-MOF-11 cavities facilitate the adsorption of polar VOC molecules. This work promotes the fundamental understanding and practical application of bio-MOF for adsorptive removal of VOCs.

Three-dimensionally macroporous MnZrOx catalysts for propane combustion: Synergistic structure and doping effects on physicochemical and catalytic properties

Three-dimensionally macroporous (3DM) MnZrO_x catalysts were fabricated to reveal the structure and Zr-doping effects on both physicochemical properties and propane combustion behaviors. The increasing addition of zirconium is favorable for the formation of 3DM structure and amorphous Mn-Zr solid solution, leading to tunable physicochemical properties. The significant activity improvement after zirconium addition was originally attributable to the superior redox ability, higher oxygen mobility and more abundant oxygen vacancy. The excellent catalytic activity, cycling stability and water resistant ability over 3DM Mn_0.6Zr_0.4O_x make it a promising material for hydrocarbons elimination. The comparative TPSR, in situ DRIFTs and kinetics study over 3DM and bulk catalysts emphasize the advantageous function of 3DM architecture on promoting propane adsorption, oxidation and lattice oxygen mobility.

Facile fabrication of a NiO/Ag3PO4 Z-scheme photocatalyst with enhanced visible-light-driven photocatalytic activity

The photocatalytic performance of Z-scheme NiO/Ag/Ag₃PO₄ was evaluated by degrading organic pollutants under visible light.