The role of phosphotungstic acid in enhancing the catalytic performance of UiO-66 (Zr) and its applications as an efficient solid acid catalyst for coumarins and dihydropyrimidinones synthesis

Amino-induced cadmium metal-organic framework based on thiazole ligand as a heterogeneous catalyst for the epoxidation of alkenes

Selective epoxidation of olefins is of high interest in the chemical industry due to the many applications of epoxides. This study reports on the synthesis of Cd-MOF, [Cd(DPTTZ)(5-AIP)] (IUST-1) (where DPTTZ = 2, 5-di (pyridine-4-yl) thiazolo [5, 4-d] thiazole, 5-AIP = 5-Aminoisophthalic acid), by a reflux method, which can be considered as a fast and simple process. The morphology and structure of the synthesized IUST-1 were determined by using FE-SEM (Field Emission Scanning Electron Microscopy), EDX (Energy Dispersive Analysis of X-ray), Mapping (Elemental Mapping), CHNS (Elemental analysis), XRD (X-Ray Diffraction), FT-IR (Fourier Transform Infrared), and TGA (Thermo Gravimetric Analysis). The epoxidation of cyclooctene was investigated using the activity of catalytic IUST-1. The results showed that in the presence of tert-butyl hydroperoxide and CCl4 in a 1:2 alkene/oxidant ratio, a high epoxide yield (99.8%) was obtained. In addition, IUST-1 can be easily separated by simple filtration and recycled five times successfully with a slight decrease in activity. This compound has some advantages such as high yield, short reaction time, and ease of reuse, which make it a suitable heterogeneous catalyst for the epoxidation of cyclooctene.

Green synthesis of thiourea derivatives from nitrobenzenes using Ni nanoparticles immobilized on triazine-aminopyridine-modified MIL-101(Cr) MOF

Nanohybrid metal-organic frameworks (MOF) have recently been considered next-generation catalysts regarding their unique features like large surface-to-volume ratio, tailorable geometry, uniform pore sizes, and homogeneous distribution of active sites. In this report, we address the triazine-aminopyridine-modified 3D Cr-centred MOF MIL-101(Cr)-NH2 following a post-synthetic modification approach. The excellent chelating ability of triazine-aminopyridine was applied to immobilize Ni ions over the host matrix MOF. The as-synthesized material was physicochemically characterized using various analytical techniques like FT-IR, electron microscopy, EDS, elemental mapping, XRD, and ICP-OES. Subsequently, the material has been catalytically employed in synthesizing new thiourea derivatives by reacting to nitrobenzene derivatives and phenyl isocyanate. The catalyst was isolated by centrifugation and recycled in 6 consecutive runs without momentous loss of its reactivity.

In-situ preparation of sulfonated carbonaceous copper oxide-zirconia nanocomposite as a novel and recyclable solid acid catalyst for reduction of 4-nitrophenol

The missing-linker defects of UiO-66 were exploited to covalently anchor Cu nanoclusters (Cu/UiO-66). The molecular interactions between the metals and oxides as copper-zirconia interfaces in Cu/UiO-66 are essential for heterogeneous catalysis, leading to remarkable synergistic impacts on activity and selectivity. Homogeneously distributed carbonaceous mixed metal oxides (CuO/ZrO₂@C) nanocomposite was prepared via carbonization of the Cu/UiO-66 at 600 °C for 3 h in air. To enhance the acidity properties of the CuO/ZrO₂@C nanocomposite, a small amount of sulfuric acid was added and heated at 150 °C under an N₂ atmosphere (CuO/ZrO₂-SO₃H@C). The synthesised Cu/UiO-66 and CuO/ZrO₂-SO₃H@C catalysts were used as novel catalysts in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The Cu/UiO-66 and CuO/ZrO₂-SO₃H@C catalysts displayed complete conversion of the 4-NP solution during (4 and 2 min) stirring at room temperature, respectively. These two catalysts exhibited a high reduction rate of 8.61 × 10^-3 s^-1, and 18.3 × 10^-3 s^-1, respectively. The X-ray photoelectron spectroscopic (XPS) analysis showed the charge of copper atoms in the Cu/UiO-66 catalyst was Cu⁰/Cu^II and in the CuO/ZrO₂-SO₃H@C catalyst was Cu^I/Cu^II with nearly the same ratio (65/35). The particle size and the elemental composition of the CuO/ZrO₂-SO₃H@C catalyst were analysed by using high resolution transmission electron microscopy (HR-TEM), and energy-dispersive X-ray spectroscopy (EDS), and elemental mapping, respectively. The key point beyond the high catalytic activity and selectivity of the CuO/ZrO₂-SO₃H@C catalyst is both the carbon-metal oxides heterojunction structure that leads to good dispersion of the CuO and ZrO₂ over the carbon sheets, and the high acidity properties that come from the combination between the Brønsted acid sites from sulfuric acid and Lewis acid sites from the UiO-66. The catalysts exhibited good recyclability efficiency without significant loss in activity, indicating their good potential for industrial applications.

Removal of Phosphorus with the Use of Marl and Travertine and Their Thermally Modified Forms-Factors Affecting the Sorption Capacity of Materials and the Kinetics of the Sorption Process

The paper presents new reactive materials, namely marl and travertine, and their thermal modifications and the Polonite^® material, analyzing their phosphorus removal from water and wastewater by sorption. Based on the experimental data, an analysis of the factors influencing the sorption capacity of the materials, such as the material dose, pH of the initial solution, process temperature, surface structure, and morphology, was performed. Adsorption isotherms and maximum sorption capacities were determined with the use of the Langmuir, Freundlich, Langmuir-Freundlich, Tóth, Radke-Praunitz, and Marczewski-Jaroniec models. The kinetics of the phosphorus sorption process of the tested materials were described using reversible and irreversible pseudo-first order, pseudo-second order, and mixed models. The natural materials were the most sensitive to changes in the process conditions, such as temperature and pH. The thermal treatment process stabilizes the marl and travertine towards materials with a more homogeneous surface in terms of energy and structure. The fitted models of the adsorption isotherms and kinetic models allowed for an indication of a possible phosphorus-binding mechanism, as well as the maximum amount of this element that can be retained on the materials' surface under given conditions-raw marl (43.89 mg P/g), raw travertine (140.48 mg P/g), heated marl (80.44 mg P/g), heated travertine (282.34 mg P/g), and Polonite^® (54.33 mg P/g).

Metal-Organic Framework-Derived Atomically Dispersed Co-N-C Electrocatalyst for Efficient Oxygen Reduction Reaction

In this work, an atomically dispersed cobalt-nitrogen-carbon (Co-N-C) catalyst is prepared for the oxygen reduction reaction (ORR) by using a metal-organic framework (MOF) as a self-sacrifice template under high-temperature pyrolysis. Spherical aberration-corrected electron microscopy is employed to confirm the atomic dispersion of high-density Co atoms on the nitrogen-doped carbon scaffold. The X-ray photoelectron spectroscopy results verify the existence of Co-N-C active sites and their content changes with the Co content. The electrochemical results show that the electrocatalytic activity shows a volcano-shaped relationship, which increases with the Co content from 0 to 0.99 wt.% and then decreases when the presence of Co nanoparticles at 1.61 wt.%. The atomically dispersed Co-N-C catalyst with Co content of 0.99 wt.% shows an onset potential of 0.96 V vs. reversible hydrogen electrode (RHE) and a half-wave potential of 0.89 V vs. RHE toward ORR. The excellent ORR activity is attributed to the high density of the Co-N-C sites with high intrinsic activity and high specific surface area to expose more active sites.

Exploring the Effect of Hierarchical Porosity in BEA Zeolite in Friedel-Crafts Acylation of Furan and Benzofuran

Hierarchical BEA zeolite was prepared through desilication or desilication followed by acid treatment. The catalytic performance of BEA zeolite samples was evaluated using Friedel-Crafts acylations with two substrates of different molecular sizes, furan (5.7 Å) and benzofuran (6.9 Å), in the presence of acetic anhydride as acylating agent. The application of the simplified Langmuir-Hinshelwood kinetic model showed that the size of the substrate leads to different catalytic activities, with improved rate constant and turnover frequency (TOF) solely in the presence of benzofuran for both desilicated and further acid treated samples. The mesopores developed during the zeolite treatments have an important role as transportation channels by reducing diffusion limitations. The application of Quantitative Structure–Property Relationships (QSPR) allowed the finding of the most relevant properties of the zeolite and substrate with impact on the catalytic parameters.

The Preparation of {001}TiO2/TiOF2 via a One-Step Hydrothermal Method and Its Degradation Mechanism of Ammonia Nitrogen

{001}TiO₂/TiOF₂ photocatalytic composites with a high activity {001} crystal plane were prepared by one-step hydrothermal methods using butyl titanate as a titanium source and hydrofluoric acid as a fluorine source. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), raman spectroscopy, N₂ adsorption-desorption curve (BET), UV-Vis diffuse absorption spectroscopy (UV-Vis DRS), X-ray photoelectron spectroscopy (XPS), and fluorescence spectroscopy (PL) were used to evaluate the structure, morphology, specific surface area, optical properties, and photocarrier separation ability of {001}TiO₂/TiOF₂. Ammonia nitrogen was taken as the target pollutant, and the degradation performance of the catalyst was investigated. The results show that hydrofluoric acid improves the content of {001} crystal plane of TiO₂ with high activity; it also improves the specific surface area and dispersion of the composite material and adjusts the ratio of {001}TiO₂ to TiOF₂ in the composite material to enhance the absorption capacity of the composite material and reduce the band gap width of the composite material. The degradation rate of ammonia nitrogen by 100 mg F15 is 93.19% when the initial concentration of ammonia nitrogen is 100 mg/L and pH is 10. Throughout the reaction process, the {001}TiO₂/TiOF₂ composite produces superoxide anion radical (·O₂^-) and hydroxyl radical (·OH) to oxidize NH₃·H₂O and generate N₂ accompanied by a small amount of NO₃^- and NO₂^-.

Synthesis of Fe2O3/Mn2O3 Nanocomposites and Impregnated Porous Silicates for Dye Removal: Insights into Treatment Mechanisms

Fe2O3/Mn2O3 nanocomposites and impregnated porous silicates (Fe2O3/Mn2O3@SiO2 [FMS]) were prepared and investigated as catalytic adsorbents. The catalysts were applied for cationic and anionic dye pollutants in the adsorption, Fenton reaction, and photocatalysis processes at a pH of 7. Fe2O3/Mn2O3 nanoparticles (FM-NPs) were prepared using the co-precipitation method and were impregnated in SiO2 by the sol–gel process. The synthesized materials were characterized using various sophisticated techniques. Results indicated that the impregnation of bi-metallic NPs in SiO2 increased the surface area, and the function of the adsorbent also improved. FMS showed a significant adsorption effect, with 79.2% rhodamine B removal within 15 min. Fenton and photocatalyst reaction showed removal rates of 85.3% and 97.9%, respectively, indicating that negatively charged porous silicate attracts cationic pollutants. In the case of the anionic pollutant, Congo red, the adsorption reaction of FMS did not occur, and the removal rate of the photocatalyst reaction was 79%, indicating the repulsive force between the negatively charged silica and the anionic dye. Simultaneously, bi-metal-bonded FM-NPs facilitated the photocatalytic reaction, reducing the recombination of electron-hole pairs. This study provides new insights into the synthesis of FM-NPs and FMS as photocatalytic adsorbents and their photocatalytic mechanisms based on reaction conditions and contaminant characteristics. The developed materials have potential applications for environmental mitigation.

Efficient Degradation of Printing and Dyeing Wastewater by Lotus Leaf-Based Nitrogen Self-Doped Mesoporous Biochar Activated Persulfate: Synergistic Mechanism of Adsorption and Catalysis

The discharge of printing and dyeing wastewater has been increasing, causing serious environmental pollution with the rapid development of the industry. Based on this, an N self-doped mesoporous lotus leaf biochar (LLC800) was prepared from lotus leaves as raw material for the activation of Persulfate (PS) to degrade wastewater from printing and dyeing. The removal rate of AO7 by PS, LLC800 and LLC800/PS systems were 0.84%, 31.11% and 99.46%, respectively. Electron paramagnetic resonance spectroscopy (EPR) and quench tests showed the presence of free radicals (•OH, SO4●− and O2●−) and nonradical (1O2) in the LLC800/PS system, where nonradicals (1O2) play an important role in the degradation of AO7. The “N self-doped” effect formed by the high N content of lotus leaves is the main factor leading to the high adsorption and catalytic performance of lotus leaf biochar. The effect of pyrolysis temperature on the performance of biochar can be attributed to the change of N content and conformation and specific surface area in biochar. Moreover, the LLC800/PS system has a strong resistance to interference. This work can provide technical support for the preparation of high-performance adsorption-catalytic biochar and the development of high-performance activation materials for persulfate.