Catalysis Science & Technology最新文献

Crystalline orthorhombic Mo₃VO_x (MoVO) is a promising catalyst for the selective oxidation of acrolein (ACR) and methacrolein (MCR), and the heptagonal channel texture acts as a catalysis field for these reactions. However, the catalytic performance for the former reaction is far superior to that for the latter, even though their molecular structures are similar except for the presence of a methyl group. This activity difference has long been a controversial issue in the oxidation chemistry of Mo–V based mixed metal oxides, although no clear conclusion has yet been provided. Here, the catalytic properties of MoVO for these reactions were investigated in detail. Based on the structure–activity relationship, it was found that the ACR oxidation takes place over the cross-section of the rod-shaped crystal of MoVO ((001) plane), while the MCR oxidation occurs over the lateral-section. This difference was derived from the interaction between the substrates and the crystal structure of MoVO; the heptagonal channel texture in the (001) plane captured ACR inside the channel, whereas MCR was hardly accessible to the same site due to its large molecular size. Based on the fact that MoVO generates electrophilic oxygen species effective for aldehyde oxidation at the heptagonal channel, the exceptionally high catalytic performance of MoVO for the selective oxidation of ACR could be associated with the two striking properties of the heptagonal channel; capturing of ACR and generation of the electrophilic oxygen species. The former was lacking in the selective oxidation of MCR, which accounted for the significantly lower catalytic activity than that for the ACR oxidation. However, its catalytic performance was even superior to that of other reported MCR oxidation catalysts because MoVO could form the electrophilic oxygen species at the heptagonal channel exposed on the lateral-section of the rod.

In this work, a new ternary-layered double-hydroxide photocatalyst, denoted as Fe₃O₄/AlZn–Cu, was synthesized using a specific 6.5 : 3 : 7.5 : 1.5 mol mol⁻¹ ratio. The rational selection of constituents in this catalyst – Fe₃O₄ for bulk and electron richness effect, AlZn LDH for supporting the photo redox process, and copper as an active site – is thoroughly elucidated. This paper comprehensively investigates the synthesis and characterizes the properties of this magnetic ternary-layered double-hydroxide heterogeneous multifunctional photocatalyst. Several key scientific domains are explored within this study: (i) demonstrating the catalyst's efficacy in synthesizing 1,2,3-triazoles N-acetamide as an active biological candidate; (ii) synthesize a 1,2,3-triazole scaffold in a benign and ambient environment, having biologically active properties (iii) a comprehensive analysis of the catalyst's structural, optical, and electrochemical properties; and (iv) evaluating the potential of newly structured drug candidates, integrating two anti-Alzheimer heterocyclic moieties linked through click chemistry, through in vitro assessment. Employing insights from biorthogonal chemistry, this study establishes a link between two distinct active Alzheimer-targeting biological moieties via click chemistry, obviating the need for organic ligands, photosensitizers, and additives. Furthermore, the multifunctional photocatalyst proves to be cost-effective, robust, and recyclable. The stability of the Fe₃O₄/AlZn–Cu structure allows for efficient recyclability, facilitated by magnetic recovery techniques, demonstrated effectively over five cycles. Extensive analysis of the recycled catalyst is conducted, affirming its potential for sustainable applications.

This work employs ambient pressure X-ray photoelectron spectroscopy (APXPS) to delve into the atomic and electronic transformations of a core–shell Ni@NiO/NiCO₃ photocatalyst – a model system for visible light active plasmonic photocatalysts used in water splitting for hydrogen production. This catalyst exhibits reversible structural and electronic changes in response to water vapor and solar simulator light. In this study, APXPS spectra were obtained under a 1 millibar water vapor pressure, employing a solar simulator with an AM 1.5 filter to measure spectral data under visible light illumination. The in situ APXPS spectra indicate that the metallic Ni core absorbs the light, exciting plasmons, and creates hot electrons that are subsequently utilized through hot electron injection in the hydrogen evolution reaction (HER) by NiCO₃. Additionally, the data show that NiO undergoes reversible oxidation to NiOOH in the presence of water vapor and light. The present work also investigates the contribution of carbonate and its involvement in the photocatalytic reaction mechanism, shedding light on this seldom-explored aspect of photocatalysis. The APXPS results highlight the photochemical reduction of carbonates into –COOH, contributing to the deactivation of the photocatalyst. This work demonstrates the APXPS efficacy in examining photochemical reactions, charge transfer dynamics and intermediates in potential photocatalysts under near realistic conditions.

The production of high-value-added chemicals and their raw materials by partial oxidation of methane (POM) is advantageous. The screening of 31 simple oxide catalysts for direct POM showed that ZrO₂ had the highest syngas yield (CO and H₂) and was thus a promising catalyst. Kinetic analysis indicated that POM over the ZrO₂ catalyst proceeded in a Langmuir–Hinshelwood mechanism and that CH₄ activation was the rate-limiting step. Density functional theory calculations showed that CH₄ was activated on coordinatively unsaturated Zr⁴⁺ cations formed by the dehydration of the hydroxyl groups on the ZrO₂ surface. In situ diffuse reflectance infrared Fourier transform spectroscopy revealed that CH₄ was converted into CO and H₂ through CH₄-oxygenated intermediates, such as methoxy and formate species. The CH₄-oxygenated intermediates on the ZrO₂ catalyst were closely related to the catalytic performance of the oxide catalysts in POM. A comprehensive investigation of the POM reaction over ZrO₂-based catalysts was then conducted. ZrO₂ modification with tungsten oxide (WO_x) or lanthanum oxide (LaO_x) was examined to determine their ability to improve the catalytic properties of ZrO₂ for POM. ZrO₂ modification with WO_x and LaO_x enhanced its acidity and basicity, respectively. CO selectivity was increased by modifying ZrO₂ with a small amount of WO_x. Moreover, modification with LaO_x increased CH₄ conversion and H₂ yield at low temperatures.