Search Results (959)

Surface and sub-surface atomic configurations are critical for catalysis as they host the active sites governing electrochemical processes. This study employs density functional theory (DFT) calculations and Monte Carlo simulations combined with the cluster-expansion approach to investigate atom distribution and Pt segregation in Pt-Fe alloys across varying Pt/Fe ratios. Our simulations reveal a strong tendency for Pt atoms to segregate to the surface layer while Fe atoms enrich the sub-surface region. Crucially, the calculations predict the stability of a periodic Pt₂Fe alloy surface model, characterized by specific defect structures, at low platinum content and low annealing temperatures. Electronic structure analysis indicates that forming this Pt₂Fe surface alloy lowers the d-band center of Pt atoms, weakening CO adsorption and thereby enhancing resistance to CO poisoning. Although defect-induced strains can modulate the d-band center, crystal orbital Hamilton population (COHP) analysis confirms that such strains generally strengthen Pt-CO interactions. Therefore, the theoretical design of Pt₂Fe alloy surfaces and controlling defect density are predicted to be effective strategies for enhancing catalyst resistance to CO poisoning. This work highlights the advantages of periodic Pt₂Fe surface models for anti-CO poisoning and provides computational guidance for designing efficient Pt-based electrocatalysts. Full article

Water pollution caused by increasing industrial and human activity remains a serious environmental challenge, especially due to the persistence of organic contaminants in aquatic systems. Photocatalysis offers a promising and eco-friendly solution, but in the case of bismuth oxide (Bi₂O₃) there is still a limited understanding of how structural and morphological features influence photocatalytic performance. In this work, a straightforward hydrothermal synthesis method followed by controlled calcination was developed to produce phase-pure α- and β-Bi₂O₃ with tunable morphologies. By varying the hydrothermal temperature and reaction time, distinct structures were successfully obtained, including flower-like, broccoli-like, and fused morphologies. XRD analyses showed that the final crystal phase depends solely on the calcination temperature, with β-Bi₂O₃ forming at 350 °C and α-Bi₂O₃ at 500 °C. SEM and BET analyses confirmed that morphology and surface area are strongly influenced by the hydrothermal conditions, with the flower-like β-Bi₂O₃ exhibiting the highest surface area. UV–Vis spectroscopy revealed that β-Bi₂O₃ also has a lower bandgap than its α counterpart, making it more responsive to visible light. Photocatalytic tests using Rhodamine B showed that the flower-like β-Bi₂O₃ achieved the highest degradation efficiency (81% in 4 h). Kinetic analysis followed pseudo-first-order behavior, and radical scavenging experiments identified hydroxyl radicals, superoxide radicals, and holes as key active species. The catalyst also demonstrated excellent stability and reusability. Additionally, Methyl Orange (MO), a more stable and persistent azo dye, was selected as a second model pollutant. The flower-like β-Bi₂O₃ catalyst achieved 73% degradation of MO at pH = 7 and complete removal under acidic conditions (pH = 2) in less than 3 h. These findings underscore the importance of both phase and morphology in designing high-performance Bi₂O₃ photocatalysts for environmental remediation. Full article

Ultra-high-molecular-weight polyethylene (UHMWPE) is a pivotal material in engineering and biomedical applications due to its exceptional mechanical strength, wear resistance, and impact performance. However, its extreme melt viscosity, caused by extensive chain entanglements, severely limits processability via conventional melt-processing techniques. Recent advances in catalytic synthesis have enabled the production of disentangled UHMWPE (dis-UHMWPE), which exhibits enhanced processability while retaining superior mechanical properties. Notably, heterogeneous catalytic systems, utilizing supported fluorinated bis (phenoxy-imine) titanium (FI) catalysts, polyhedral oligomeric silsesquioxanes (POSS)-modified Z-N catalysts, and other novel catalysts, have emerged as promising solutions, combining structural control with industrial feasibility. Moreover, optimizing polymerization conditions further enhances chain disentanglement while maintaining ultra-high molecular weights. These systems utilize nanoscale supports and ligand engineering to spatially isolate active sites, tailor the chain propagation/crystallization kinetics, and suppress interchain entanglement during polymerization. Furthermore, characterization techniques such as melt rheology and differential scanning calorimetry (DSC) provide critical insights into chain entanglement, revealing distinct reorganization kinetics and bimodal melting behavior in dis-UHMWPE. This development of hybrid catalytic systems opens up new avenues for solid-state processing and industrial-scale production. This review highlights recent advances concerning interaction between catalyst design, polymerization control, and material performance, ultimately unlocking the full potential of UHMWPE for next-generation applications. Full article

This study investigates the influence of divalent metals—(Mg(II), Co(II), and Ni(II)) in layered double hydroxides (LDHs), with a constant trivalent Fe(III) component—on the decoloration of crystal violet and methyl blue dyes via a Fenton-type oxidation reaction. The catalysts, synthesized by co-precipitation and hydrothermal treatment, were tested in both hydroxide and oxide forms under varying agitation conditions (0 and 280 rpm). A 2² × 3 factorial design was used to analyze the effect of the divalent metal type, catalyst phase, and stirring. The Mg/Fe oxide, with the highest BET surface area (144 m²/g) and crystallite size (59.7 nm), showed superior performance—achieving up to 98% decoloration of crystal violet and 97% of methyl blue within 1 h. The kinetic analysis revealed pseudo-second-order and pseudo-first-order fits for crystal violet and methyl blue, respectively. These findings suggest that LDH-based catalysts provide a fast, low-cost, and effective option for dye removal in aqueous systems. Full article

Searching for new and efficient transfer hydrogenation catalysts, a series of new organometallic ruthenium(II)-arene complexes of the formulae [Ru(η⁶-p-cymene)(L)Cl][PF₆] (1–8) and [Ru(η⁶-p-cymene)(L)Cl][Ru(η⁶-p-cymene)Cl₃] (9–11) were synthesized and fully characterized. These were prepared from the reaction of pyridine–quinoline and biquinoline-based ligands (L) with [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂, in 1:2 and 1:1, metal (M) to ligand (L) molar ratios. Characterization includes a combination of spectroscopic methods (FT-IR, UV-Vis, multi nuclear NMR), elemental analysis and single-crystal X-ray crystallography. The pyridine–quinoline organic entities encountered, were prepared in high yield either via the thermal decarboxylation of the carboxylic acid congeners, namely 2,2′-pyridyl-quinoline-4-carboxylic acid (pqca), 8-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (8-Mepqca), 6′-methyl-2,2′-pyridyl-quinoline-4-carboxylic acid (6′-Mepqca) and 8,6′-dimethyl-2,2′-pyridyl-quinoline-4-carboxylic acid (8,6′-Me₂pqca), affording the desired ligands pq, 8-Mepq, 6′-Mepq and 8,6′-Me₂pq, or by the classical Friedländer condensation, to yield 4,6′-dimethyl-2,2′-pyridyl-quinoline (4,6′-Me₂pq) and 4-methyl-2,2′-pyridyl-quinoline (4-Mepq), respectively. The solid-state structures of complexes 1–4, 6, 8 and 9 were determined showing a distorted octahedral coordination geometry. The unit cell of 3 contains two independent molecules (Ru-3), (Ru′-3) in a 1:1 ratio, due to a slight rotation of the arene ring. All complexes catalyze the transfer hydrogenation of acetophenone, using 2-propanol as a hydrogen donor in the presence of KOiPr. Among them, complexes 1 and 5 bearing methyl groups at the 8 and 4 position of the quinoline moiety, convert acetophenone to 1-phenylethanol quantitatively, within approximately 10 min with final TOFs of 1600 h⁻¹. The catalytic performance of complexes 1–11, towards the transfer hydrogenation of p-substituted acetophenone derivatives and benzophenone, ranges from moderate to excellent. An inner-sphere mechanism has been suggested based on the detection of ruthenium(II) hydride species. Full article

Paddlewheel dirhodium complexes are cytotoxic compounds that are also used as catalysts and in the formation of Rh-based artificial metalloenzymes. Low-temperature structures of adducts formed by the model protein hen egg white lysozyme (HEWL) with dirhodium tetraacetate ([Rh₂(μ-O₂CCH₃)₄]) when crystals of the protein were treated with the metal compound at 20 °C demonstrated that [Rh₂(μ-O₂CCH₃)₄] in part breaks down upon reaction with HEWL; dimeric Rh-Rh units bind the side chains of Asp18 and the C-terminal carboxylate, and monometallic fragments coordinate the side chains of Arg14 and His15 in 20% ethylene glycol, 0.100 M sodium acetate at pH 4.5 and 0.600 M sodium nitrate, while dimeric Rh-Rh units bind the side chains of Asn93 and Lys96, the C-terminal carboxylate and Asp101, with monometallic fragments that bind the side chains of Lys33 and His15 in 0.010 M HEPES pH 7.5 and 2.00 M sodium formate. To verify whether the binding of this metallodrug to proteins also occurs at body temperature, crystals of HEWL were grown in 0.010 M HEPES pH 7.5 and 2.00 M sodium formate at 37 °C and soaked with [Rh₂(μ-O₂CCH₃)₄] at the same temperature. X-ray diffraction data collected on these crystals at 37 °C demonstrate that [Rh₂(μ-O₂CCH₃)₄] reacts with proteins at body temperature. The structures of the Rh/HEWL adduct formed at 20 °C (obtained from data collected at 100 K) and at 37 °C under the same experimental conditions are very similar, with metal binding sites that are conserved. However, metal-containing fragment occupancy is higher in the structure obtained at 37 °C, suggesting a role of temperature in defining the protein metalation process. Full article

To ensure the sustainable use of limited resources, it is essential to establish selective and efficient recycling technologies for platinum group metals (PGMs). This study focused on the selective precipitation-based separation of Pt(IV) from hydrochloric acid (HCl) solutions in the presence of various metal ions, using trans-1,4-bis(aminomethyl)cyclohexane (BACT) as a precipitating agent. By using BACT, we succeeded in the selective separation of Pt(IV) by precipitation from HCl solutions containing Pd(II) and Rh(III). Notably, selective and efficient recovery of Pt(IV) was accomplished across various HCl concentrations, with a small amount of BACT and within a short shaking time. To evaluate the practical applicability of the method, Pt(IV) was recovered and purified from the HCl leachate of spent automotive exhaust gas purification catalysts using BACT. As a result, a high Pt recovery of 95.6% and a high purity of 99.3% were achieved. Although Pt(IV) was recovered as a precipitate containing BACT, it was found that Pt black could be readily obtained by dissolving the precipitate in HCl solution followed by reduction with sodium borohydride. Detailed structural analysis of the Pt(IV)-containing precipitate revealed that it is an ionic crystal composed of [PtCl₆]²⁻ and protonated BACT. The selective formation of this ionic crystal in HCl solution, along with its stability under such conditions, is the key to the selective recovery of Pt(IV) using BACT. Full article

Zinc–air batteries (ZABs) are crucial for renewable energy conversion and storage due to their cost-effectiveness, excellent safety, and superior cycling stability. However, developing efficient and affordable bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) at the air cathode remains a significant challenge. Manganese (Mn)-based materials, known for their tunable oxidation states, adaptable crystal structures, and environmental friendliness, are regarded as the most promising candidates. This review systematically summarizes recent advances in Mn-based bifunctional catalysts, concentrating on four primary categories: Mn–N–C electrocatalysts, manganese oxides, manganates, and other Mn-based compounds. By examining the intrinsic merits and limitations of each category, we provide a comprehensive discussion of optimization strategies, which include morphological modulation, structural engineering, carbon hybridization, heterointerface construction, heteroatom doping, and defect engineering, aimed at enhancing catalytic performance. Additionally, we critically address existing challenges and propose future research directions for Mn-based materials in rechargeable ZABs, offering theoretical insights and design principles to advance the development of next-generation energy storage systems. Full article

The disposal of wastewater resulting from petroleum industries presents a major environmental challenge due to the presence of hard-to-degrade organic pollutants, such as oils and hydrocarbons, and high chemical oxygen demand (COD). In this study, an efficient and eco-friendly method was developed to treat such wastewater using a photocatalyst composed of biochar derived from pistachio shells and loaded with zinc oxide (ZnO) nanoparticles. The biochar-ZnO composite was prepared via a co-precipitation-assisted pyrolysis method to evaluate its efficiency in the photocatalytic degradation of petroleum wastewater (PW). The synthesized material was characterized using various techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy, to determine surface morphology, crystal structure, and functional groups present on the catalyst surface. Photocatalytic degradation experiments were conducted under UV and sunlight for 90 h of irradiation to evaluate the performance of the proposed system in removing oil and reducing COD levels. Key operational parameters, such as pH (2–10), catalyst dosage (0–0.1) g/50 mL, and oil and COD concentrations (50–500) ppm and (125–1252) ppm, were optimized by response surface methodology (RSM) to obtain the maximum oil and COD removal efficiency. The oil and COD were removed from PW (90.20% and 88.80%) at 0.1 g/50 mL of PS/ZnO, a pH of 2, and 50 ppm oil concentration (125 ppm of COD concentration) under UV light. The results show that pollutant removal is slightly better when using sunlight (80.00% oil removal, 78.28% COD removal) than when using four lamps of UV light (77.50% oil removal, 75.52% COD removal) at 0.055 g/50 mL of PS/ZnO, a pH of 6.8, and 100 ppm of oil concentration (290 ppm of COD concentration). The degradation rates of the PS/ZnO supported a pseudo-first-order kinetic model with R² values of 0.9960 and 0.9922 for oil and COD. This work indicates the potential use of agricultural waste, such as pistachio shells, as a sustainable source for producing effective catalysts for industrial wastewater treatment, opening broad prospects in the field of green and nanotechnology-based environmental solutions in the development of eco-friendly and effective wastewater treatment technologies under solar light. Full article

Green hydrogen production from water electrolysis (WE) is one of the most promising technologies to realize a decarbonized future and efficiently utilize intermittent renewable energy. Among the various WE technologies, the emerging anion exchange membrane (AEMWE) technology shows the greatest potential for producing green hydrogen at a competitive price. To achieve this goal, simple methods for the large-scale synthesis of efficient and low-cost electrocatalysts are needed. This paper proposes a very simple and scalable process for the synthesis of nanostructured NiCo- and NiFe-based electrode materials for a zero-gap AEMWE full cell. For the preparation of the cell anode, oxides with different Ni molar fractions (0.50 or 0.85) are synthesized by the sol–gel method, followed by calcination in air at different temperatures (400 or 800 °C). To fabricate the cell cathode, the oxides are reduced in a H₂/Ar atmosphere. Electrochemical testing reveals that phase purity and average crystal size significantly influence cell performance. Highly pure and finely grained electrocatalysts yield higher current densities at lower overpotentials. The best performing membrane electrode assembly exhibits a current density of 1 A cm⁻² at 2.15 V during a steady-state 150 h long stability test with 1 M KOH recirculating through the cell, the lowest series resistance at any cell potential (1.8 or 2.0 V), and the highest current density at the cut-off voltage (2.2 V) both at the beginning (1 A cm⁻²) and end of tests (1.78 A cm⁻²). The presented results pave the way to obtain, via simple and scalable techniques, cost-effective catalysts for the production of green hydrogen aimed at a wider market penetration by AEMWE. Full article

A novel metal–organic framework based on zinc ions, designated as Zn-URJC-12, has been synthesized and applied for the first time in the cycloaddition reaction between carbon dioxide and epoxides. This MOF is constructed from two different organic linkers: 5-aminoisophthalic acid and 4,4′-biphenyldicarboxylic acid. The framework features –NH₂ functional groups coordinated to Zn(II) centers, as confirmed by single-crystal X-ray diffraction analysis. Zn-URJC-12 demonstrates exceptional chemical stability in polar organic solvents, such as methanol, while maintaining thermal stability up to 250 °C. The material exhibits high catalytic efficiency in the cycloaddition of CO₂ with epoxides, achieving yields of 100% and 76% for propylene oxide and allyl glycidyl ether, respectively. Additionally, Zn-URJC-12 maintains its structural integrity and catalytic performance during five successive reaction cycles. These findings underscore Zn-URJC-12 as a promising heterogeneous catalyst for the valorization of CO₂ into cyclic carbonates. Full article

In this study, Mg-Al-Zn, MgO, Al₂O_3, and ZnO were synthesized via the co-precipitation method and evaluated as catalysts for the transesterification reaction of dimethyl carbonate (DMC) and ethanol. The crystal structure, morphological characteristics, pore structure properties, and alkaline properties of the catalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, temperature-programmed desorption of CO₂ (CO₂-TPD), and Fourier transform infrared spectroscopy (FTIR). The surface alkali strength and alkalinity of the solids were determined using the Hammett indicator method and non-aqueous titration. When Al₂O₃ and ZnO are used as catalysts for this transesterification, the conversion rate of dimethyl carbonate is relatively low. When MgO and Mg-Al-Zn are used as catalysts, the conversion rate of dimethyl carbonate is higher. This indicates that the alkali strength of the catalyst for the transesterification reaction needs to be greater than 9.3. Additionally, the activity of the catalysts is also related to the amount of the alkaline sites on the solid surface. The alkali strength of MgO is greater than 11; its excessively high alkali strength will react with CO₂ and H₂O during use, resulting in a reduction in the number of alkaline sites and thus showing unsatisfactory reactivity. The alkaline strength of the Mg-Al-Zn catalyst ranges from 9.3 to 11.0. When used for the first time, the number of alkaline sites decreases, and then the alkalinity remains at a certain value. Therefore, the alkaline strength of the solid catalyst for the transesterification reaction between DMC and ethanol needs to be between 9.3 and 11.0 so that the number of alkaline sites on the catalyst surface remains unchanged and the catalytic activity remains stable. Full article

Background: α-Hydroxyphosphonates, one of the most prominent classes of phosphonates, remain of utmost importance because of their potential and real biological activity as pharmaceutical or pesticide agents. The effect is the consequence of their enzyme inhibitory properties. Objectives: It was planned to make available new heterocyclic hydroxyphosphonate derivatives with cytotoxic activity. Methods: After optimizing the synthesis, 23 members of a new family, α-hydroxy-α-(benzothiophen-2-yl)-methylphosphonates, were prepared by the Pudovik reaction of benzo[b]thiophene-2-carboxaldehydes and diethyl phosphite. The addition was performed at 26 °C in the presence of triethylamine as the catalyst. One of the products was also characterized by single-crystal X-ray analysis. Results: The cytotoxic effect of the α-hydroxy-α-benzothiophenyl-methylphosphonates was tested on U266 myeloma, A2058 melanoma, HT-29 colon, and EBC-1 lung cancer cell lines. Most of the molecules showed significant activity; the greatest effects were seen after treatment with hydroxyphosphonates with a trifluoromethyl group in the benzene ring. Conclusions: The cytotoxic activity of the newly synthesized α-hydroxyphosphonates is encouraging to find even better derivatives. Full article

A series of para-trifluoromethoxy-substituted and fluorobenzhydryl-functionalized 1,2-bis(imine)acenaphthene ligands: 1-[2,6-{(4-F-C₆H₄)₂CH}₂-4-F₃COC₆H₂N]-2-(ArN)C₂C₁₀H₆ (Ar = 2,6-Me₂C₆H₃ L1, 2,6-Et₂C₆H₃ L2, 2,6-iPr₂C₆H₃ L3, 2,4,6-Me₃C₆H₂ L4, 2,6-Et₂-4-MeC₆H₂ L5), were synthesized and used to generate their corresponding nickel(II) bromide complexes (Ni1–Ni5). Elemental analysis, ¹⁹F NMR, and FT-IR spectroscopy were employed to characterize these five nickel complexes. Single-crystal X-ray diffraction of Ni2 and Ni4 confirmed distorted tetrahedral geometries. Upon activation with either EtAlCl₂ (ethylaluminum dichloride) or EASC (ethyl aluminum sesquichloride), these complexes showed exceptional high activities (up to 22.0 × 10⁶ g PE mol⁻¹ (Ni) h⁻¹) and remarkable thermal stability (4.82 × 10⁶ g PE mol⁻¹(Ni) h⁻¹ at 80 °C) towards ethylene polymerization. The resulting polyethylenes are highly branched, with the type and extent of branches tunable by temperature, solvent, and co-catalyst choice. Moreover, these polymers demonstrated excellent tensile strength (σ_b up to 20.7 MPa) and elastic recovery (up to 58%), characteristic of thermoplastic elastomers (TPEs). These results highlight the dual role of trifluoromethoxy and fluorobenzhydryl groups in enhancing catalytic performance and polymer properties. Full article

As one of the most important platform chemicals, furfural (FAL) can be converted into high-value-added products such as furfuryl alcohol (FOL) through multiple pathways. Zirconium-based MOF-801 demonstrates exceptional catalytic potential for FAL conversion via catalytic transfer hydrogenation (CTH), owing to its unique crystal defects generated during growth. In this study, a series of defective MOF-801 samples were efficiently synthesized using an air–liquid segmented microfluidic technique. The characterization results reveal that the air–liquid segmented flow method not only regulates the defect content of MOF-801 to expose more active sites but also adjusts the crystal size and pore structures by precisely controlling the reaction time. The enhanced defects in MOF-801 significantly improved its catalytic performance. A-MOF-801-64 exhibited the highest activity, achieving over 99% FAL conversion and 98% FOL selectivity under mild conditions (130 °C, 12 h) using isopropanol as the hydrogen donor; this performance surpassed that of other reported Zr-based catalysts. This study will facilitate the practical applications of defect-engineered MOF-801 in upgrading biomass-derived chemicals. Full article