ChemCatChem最新文献

Effective and selective recycling of polyethylene terephthalate (PET) into monomers and chemicals is essential. Herein, transition metal-doped ZnO catalysts (M = Ti, Zr, and Hf) were synthesized and investigated for PET methanolysis. Among them, the Ti-doped ZnO catalyst containing 7.5 wt% Ti (7.5Ti–ZnO) exhibited excellent activity, delivering 98.3% dimethyl terephthalate (DMT) yield at 170°C in 0.5 h, representing a 2.5-fold higher activity than pristine ZnO. The catalyst also showed excellent activity in real and mixed PET wastes, confirming its broad applicability. Structural and spectroscopic analyses confirmed the incorporation of Ti into the ZnO lattice, resulting in a homogeneous solid solution with lattice distortion and an abundance of oxygen vacancies. NH₃–TPD measurements revealed a substantial increase in acid sites with optimal Ti loading (7.5 wt%). The cooperative effect between oxygen vacancies and medium-strength Lewis acid sites facilitated PET and methanol activation, and subsequent C–O dissociation via nucleophilic attack by methanol. Consequently, 7.5Ti–ZnO achieved a remarkable DMT formation rate of 510 mmol_DMT g_cat⁻¹ h⁻¹. This study further underscores the potential of DMT as a versatile feedstock for the synthesis of virgin-quality PET and other high-value monomers, thereby enabling both closed-loop recycling and open-loop upcycling pathways toward a circular plastic economy.

The conversion of methanol into aromatic hydrocarbons is fundamentally constrained by the competing formation of valuable aromatic products and polyaromatic coke, which rapidly deactivates zeolite catalysts. Here, we demonstrate that cooperative modification of ZSM-5 with a bimetallic system, zinc (Zn) and gadolinium (Gd), provides an effective strategy to overcome this limitation. Structural analyses using atomic-resolution electron microscopy, X-ray diffraction, X-ray fluorescence, and solid-state ²⁷Al nuclear magnetic resonance confirm that both metals remain atomically dispersed on the external surfaces without altering the MFI framework. Acidity measurements show that Zn introduces dehydrogenation-active Lewisacid sites, while Gd moderates strong Brønsted acid sites. Operando ultraviolet–visible spectroscopy and multi-modal coke characterization reveal that Gd suppresses polyaromatic growth, whereas Zn enhances aromatic-ring formation. Their combination yields high aromatic productivity, minimal coke deposition, and exceptional operational stability for over 72 h. The bimetallic catalyst also demonstrates excellent regeneration capability over three consecutive cycles, establishing a robust metal–acid design strategy for durable methanol-to-aromatics conversion.

Integrated CO₂ capture and utilization (ICCU) is a promising transition route for mitigating flue-gas emissions while producing useful energy-carrying chemicals. This study reveals the potential of rhenium as an alternative to nickel or ruthenium for catalyzing CO₂ methanation. It is shown that the mixing of Re/γ-Al₂O₃ with CeO₂ or a synthetic hydrotalcite-derived Mg–Al oxide (layered double oxide [LDO]) provides tunable low-Re-content dual-function materials (DFMs) with 100% CO₂ conversion and 100% methane selectivity at 300°C under cyclic operation. The direct deposition of rhenium, in an atomically dispersed form, onto CeO₂ or LDO increases the methane yield up to 128 µmol/g per 10 + 10 min cycle, suggesting a synergy between catalytic and adsorbing functions. In contrast, these two systems are poorly selective to methane in conventional gas-phase CO₂–H₂ reaction, showing the beneficial effect of sequential adsorption–hydrogenation operation on selectivity. In terms of stability, Re/CeO₂ appears as the most efficient DFM, showing stable methane production over 50 cycles, moderate deactivation in the presence of water, and full recovery after return to dry conditions. An operando diffuse reflectance infrared spectroscopy (DRIFTS) investigation of this catalyst under both ICCU and conventional hydrogenation discloses the nature of molecular adsorbates (CO, formates) and their dependence on the reaction regime. In situ Raman spectroscopy shows that the oxidation state of the active ReO_x species undergoes only minor modifications upon alternating CO₂ and H₂ steps, maintaining predominantly Re⁷⁺ moieties.

High entropy sulfides (HESs) stand out as prospective electrocatalysts for water hydrolysis due to their singular structure and electronic properties. However, compared with other high entropy materials, HESs remain largely unexplored owing to the challenge in achieving robust electrodes with high performance. Herein, we fabricate (FeCoNiCrCu)₃S₂ HES on nickel foam (NF) via an ion-exchange strategy under mild solvothermal conditions, working as robust bifunctional water electrolysis electrodes. The different solubility products of sulfides render it a dendritic architecture with abundant sulfur vacancies, which facilitates mass transport and active sites exposure and endows its higher hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity and stability, compared with ternary and quarternary alternatives. It demands only 1.719 V to reach 100 mA cm⁻² for overall water splitting and sustains 0.5 A cm⁻² for 110 h, while equipped in customized anion exchange membrane water electrolyzer (AEMWE). In situ Raman and XPS analysis substantiated the reconstructed active sites and demonstrates the controlled formation of sulfate in electrolyte, contributing to the enhanced HER and OER performance. The work provides a scalable route to low-cost, phase pure HES electrocatalysts and advances sustainable water electrolysis.

Coal tar pitch (CTP), a byproduct of coal chemical industries, requires novel strategies to enhance its value. Advancement of high activity and steady non-precious metal oxygen reduction reaction (ORR) electrocatalysts based on low-cost carbon precursors has emerged as a critical research direction. In this study, a strategy is reported for converting inactive MgAl₂O₄ into a novel and high-performance ORR catalyst MgAl₂O₄-HCPs. MgAl₂O₄-HCPs is designed via the pyrolysis of coal tar-based hyper-crosslinked polymers (HCPs) that are composited using the Friedel–Crafts alkylation reaction, with MgO serving as the template. Nitrogen doping serves as a catalyst to induce the abundant generation of oxygen vacancies, which synergistically interact with the porous carbon matrix to jointly regulate and significantly enhance the intrinsic catalytic activity on the spinel surface. MgAl₂O₄-HCPs show exceptional ORR activity with a half-wave potential of 0.882 V (vs. RHE) and is used as cathode material in zinc-air batteries (ZABs), achieving a peak power density of 174.06 mW cm⁻². This study not only provides an innovative plan for the design of cost-effective spinel-type oxide electrocatalysts but also paves the way for the efficient utilization of coal tar as a valuable resource.

Tri-imidazole derivatives, widely recognized for their broad pharmacological and therapeutic activities such as antibacterial, anticancer, antidiabetic, antifibrotic, antifungal, anti-inflammatory, antitubercular, and antiviral effect, used for efficiently synthesized using tetravalent metal acid (TMA) salts, which serve as heterogenous solid acid catalysts with stronger acidic sites, enhanced thermal stability, and improved selectivity in organic transformations. In this study, tri-imidazole and its derivatives were synthesized under solvent-free conditions using titanium phosphate (TiP), titanium-amino trismethylene phosphonic acid (Ti-ATMP), and titanium-hydroxy ethylidene di-phosphonic acid (Ti-HEDP) as heterogenous solid acid catalysts. The catalysts were thoroughly characterized by PXRD, FT-IR, SEM-EDX, XPS, N₂ adsorption–desorption isotherms, NH₃-TPD, and TGA analyses. A comparative investigation was conducted on the synthesis efficiency and recyclability of the catalysts, with progress monitored by TLC. Furthermore, a novel tri-imidazole derivative was successfully synthesized and confirmed by melting point, NMR (¹H, ¹³C and ¹⁹F) spectral analysis.

The present work investigated the binding of atomically dispersed transition metals to the 2D fullerene quasihexagonal phase C₆₀ (qhp-C₆₀) framework and the catalytic performance of the corresponding single/dual-sided single-atom catalysts for CO electroreduction by means of density functional theory calculations. Compared to isolated C₆₀ molecules, the qhp-C₆₀ framework not only effectively inhibits metal aggregation through its unique confining nanocages and stronger metal–substrate interactions, but also enhances the catalytic activity and selectivity by a more efficient electron-buffering effect. Among all the metal centers examined, Mn was identified as the most promising candidate for selective CO-to-methane conversion.

The photocatalytic conversion of CO₂ to valuable fuels is hampered by intrinsic challenges in charge separation and product selectivity. Therefore, the construction of single active sites (SASs) within metal organic frameworks (MOFs) and covalent organic frameworks (COFs) has emerged as an effective approach to address these limitations. These materials leverage well-defined porous structures to create confined reactive microenvironments and incorporate atomically dispersed active sites that maximize metal utilization and enhance product selectivity. This review systematically summarizes recent advances in the rational design of MOF and COF confined SASs, with emphasis on key strategies, including atomic-level engineering of active sites, modulation of the electronic and optical landscape and confinement effects, and reaction microenvironment engineering. These approaches collectively enhance light absorption, charge carrier dynamics, and intermediate stabilization. Special attention is given to the critical roles of pore confinement, local electric fields, and coordination microenvironments in steering reaction pathways and regulating key intermediates. By combining advanced in situ/operando spectroscopy with theoretical simulations, this review elucidates the fundamental structure–activity relationships governing photocatalytic behavior. Finally, this review outlines future research direction aimed at advancing MOF and COF confined SASs toward practical applications in efficient and stable CO₂ photoconversion.