ChemCatChem最新文献

Three Cu/SAPO-34 catalysts were synthesized via low-temperature solid-state ion-exchange using CuCl₂, Cu(NO₃)₂, and Cu(OAc)₂ precursors to investigate precursor effects on continuous direct conversion of methane-to-methanol. In the methane-water-oxygen continuous flow reaction system at 400 °C, the STY of methanol shows the order of Cu(CuCl₂)/SAPO-34 (172.8 µmol/(g_cat·h)) > Cu(Cu(NO₃)₂)/SAPO-34 (162.7 µmol/(g_cat·h)) > Cu(Cu(OAc)₂)/SAPO-34 (139.5 µmol/(g_cat·h)). H₂-TPR, EPR, and variable-temperature in-situ DRIFTS revealed that the precursor decomposition temperatures critically regulate copper species migration and distribution. Precursors (CuCl₂, Cu(NO₃)₂) rapidly released copper species that occupied SAPO-34 ion-exchange sites through solid-state ion migration, forming abundant isolated Cu²⁺ active centers. In contrast, Cu(OAc)₂ delayed copper release, causing partial Cu²⁺ failing to access ion-exchange sites and aggregation into CuO nanoparticles. In situ DRIFTS confirmed isolated Cu²⁺ species effectively activate methane C─H bonds to generate methyl intermediates, subsequently converted to methanol under H₂O-O₂ co-feeding conditions. The Cu²⁺→Cu⁺→Cu²⁺ redox cycle facilitated oxidative regeneration of active sites, sustaining catalytic center equilibrium.

The introduction of terminal alkene groups through ethenolysis is a well-established metathesis process. However, while being widely applied in industry, this reaction is not performed without risk in organic synthesis laboratories due to the hazardous properties of ethylene. In this contribution, we present an ethylene-free ethenolysis, exemplified for a terminal alkene formation at the side chain of 12-oxophytodienoic acid (12-OPDA), a chiral naturally occurring plant-hormone with internal alkene groups. This novel type of ethenolysis was achieved through ruthenium-catalyzed metathesis with a triisopropylsilyl (TIPS)-group carrying terminal alkene, acting as ethene surrogate. The newly formed terminal alkene was isolated in high purity and the structure could be unequivocally identified via NMR-spectroscopical methods as well as mass spectrometry. We propose a mechanism which follows a pathway similar to the one of a degenerate metathesis that is driven by steric hindrance between the two alkenes during the catalytic cycle. This hypothesis is supported by our further experimental findings. The successful transfer of this concept to other alkene substrates and studies with a second catalyst indicate that this method for ethylene-free introduction of terminal alkene groups through the use of bulky reagents avoiding formation of “classic” metathesis products could be applied to a wide range of other substrates, in particular complex natural products, as well.

Quantum dots (QDs) are emerging as high-performance photocatalysts, surpassing conventional systems through their superior light-harvesting efficiency, tunable electronic properties, and robust charge carrier dynamics. Here, compositionally tuned Zn_xCd_1-xS QDs (x = 0.0–1.0) are systematically optimized for visible light-driven copper-catalyzed azide–alkyne cycloaddition (CuAAC), a pivotal reaction in organic synthesis. Zn₀.₁Cd₀.₉S QDs (x = 0.1) exhibit an exceptional 99.5% triazole yield within 4 h, significantly outperforming conventional CdS QDs (6 h). Their finely tuned 2.72 eV bandgap, precisely aligned with 456 nm blue light, enhances charge separation and accelerates catalytic efficiency. These QDs demonstrate broad substrate scope, excellent functional group tolerance, high recyclability (81% efficiency over 10 cycles), and scalability (93% gram-scale yield), maintaining structural integrity as confirmed by morphological and spectroscopic analyses. This work establishes compositionally engineered QDs as advanced, durable photocatalysts, providing a transformative approach to sustainable CuAAC chemistry and broader nanomaterial-driven applications.

In this work, we have developed a simple solvothermal protocol for designing spherically arranged AgNi alloy NPs with uniform sizes and tunable compositions. This as-synthesized heterogeneous catalyst demonstrates excellent catalytic activity for nitrile hydration in water without any additives, achieving up to 99% product yield at 80 °C within just 5 h. Our as-synthesized catalyst is magnetically separable and stable under catalytic reaction conditions. A broad variety of nitriles was efficiently transformed into their respective amides using this catalyst with high selectivity. This study introduces a sustainable and cost-effective approach for the eco-friendly synthesis of amides via nitrile hydration. In addition, the as-synthesized AgNi alloy exhibited excellent hydrogen evolution activity. Ag₅Ni₁ synthesized through precise control over the stoichiometry could attain a current density of 10 mA/cm² at an overpotential of 248 mV (versus RHE) which is the lowest among all the synthesized alloy samples. Ag₅Ni₁ alloy sample could also attain an industrial scale current density of 1000 mA/cm² at a record low overpotential of 858 mV (versus RHE). The Tafel slopes of AgNi, Ag₁Ni₅, and Ag₅Ni₁ are found to be 135.6, 96.3, and 80.7 mV dec⁻¹, respectively, which is comparable to benchmark commercial catalysts. Such low values of Tafel slope values supports the outstanding potential of our as-synthesized alloy to be used as a highly efficient electrocatalyst for HER. The present work showcases the excellent catalytic efficacy of AgNi NPs as a heterogeneous catalyst in the promising field of selective organic transformations as well as electrochemical energy applications.

Ammonia (NH₃), recognized as a prospective green energy carrier due to its high hydrogen density and ease of transport, has garnered significant attention. However, the conventional Haber–Bosch (H–B) process for ammonia synthesis necessitates high-temperature and high-pressure conditions, accompanied by substantial carbon dioxide emissions. Consequently, the development of novel green ammonia synthesis technologies has become a focal point of research. Photocatalytic ammonia synthesis, leveraging solar energy as the driving force, converts nitrogen to ammonia under ambient conditions, offering advantages such as low energy consumption and environmental friendliness. This review summarizes recent advancements in photocatalytic ammonia synthesis, emphasizing nitrogen activation mechanisms, photocatalytic reaction pathways, and the design and optimization strategies for various photocatalysts. Through a detailed analysis of biomimetic catalysts, Ti-based materials, Bi-based materials, metal–organic frameworks (MOFs) materials, graphitic carbon nitride (g-C₃N₄) materials, and MXene materials, their applications and limitations in photocatalytic ammonia synthesis are discussed. Furthermore, this paper synthesizes photocatalyst design strategies, including morphology control, vacancy engineering, and bandgap engineering, aiming to provide theoretical support and practical guidance for the design of future novel photocatalysts.

The direct acylation of substituted arenes by carboxylic acids offers a sustainable route to valorize biomass-derived aromatics, avoiding the use of more hazardous and high-impact reagents such as anhydrides or acyl chlorides. In this work, we study the liquid phase acylation of guaiacol (G) with acetic acid (AA) at 120 °C and atmospheric pressure, catalyzed by commercial Aquivion PW87 resin. This system yields 2-metoxyphenyl acetate (MPA) and 4-hydroxy-3-methoxyacetophenone (p-HMAP), valuable intermediates to produce fine chemicals. MPA is the primary kinetic product, but it is progressively consumed with simultaneous formation of HMAPs and G, indicating a sequential reaction pathway that favors the formation of p-HMAP with high regioselectivity (para/ortho-HMAP molar ratio of 26). Interestingly, from the mechanistic viewpoint and given the similar energetics of the two isomers, this finding can only be rationalized by invoking an intermolecular mechanism, rather than an intramolecular (or Fries) rearrangement. Electronic structure calculations were used to investigate pathways involving either MPA reacting with G to form HMAPs, or two MPAs yielding G and O-acylated acetophenones (minor products). The results suggest that the latter governs the acylation regioselectivity, with the key step being the acid-activated attack of the MPA ester on an aromatic ring, energetically favoring p-HMAP formation.

The Cover Feature shows Co₃O₄(001) for the oxygen evolution reaction. The lower part shows an OH-terminated crystallographic slab. Three zoom windows identify a tetrahedral site (Termination A), an octahedral site (Termination B), and a pseudo-octahedral motif on Termination B. Connectors map each inset to its surface location. The water in the background places the material in its operating environment. More information can be found in the Research Article by K. S. Exner and co-workers (DOI: 10.1002/cctc.202500992).

The Front Cover shows how, like an octopus, the catalyst works with many components simultaneously to reach its target. New RuPOP pincer catalysts upgrade ethanol to butan-1-ol. Adding to the mechanistic understanding of ethanol upgrading, M. Nielsen and co-workers show in their Research Article (DOI: 10.1002/cctc.202500700) that catalysts void of the Noyori unit are fully capable of catalysing the reaction; this contrasts with the common understanding in the community of the role of the catalyst.

Hydrogenation of 1,3-butadiene to 1-butene with high selectivity is crucial in hydrocarbon processing. One powerful route to tailor the selectivity of the involved surface reactions is the SCILL (solid catalyst with ionic liquid layer) concept. In this context, we recently demonstrated that ionic liquids (ILs) selectively modify the adsorption of 1,3-butadiene over 1-butene, that is, the initial step of the hydrogenation of 1,3-butadiene on Pt(111). Herein, we now address the next reaction step, namely, how ultrathin layers of the IL [C₈C₁Im][PF₆] influence olefin displacement from Pt(111). Using temperature-programmed X-ray photoelectron spectroscopy, we track structural and compositional film changes and olefin desorption with increasing temperature. We find that i) IL deposition onto a saturated 1-butene layer enhances the displacement and desorption of 1-butene by a factor of 2.8; ii) 1,3-butadiene remains unaffected by the IL; and iii) IL decomposition on Pt(111) is shifted to higher temperatures by 80 ± 10 K.

Multi-functional catalysts, polyoxometalate (POM)-decorated silver nanoparticles (AgNPs) on Al₂O₃ (POM-Ag/Al₂O₃), which work as Lewis base, oxidative dehydrogenation, and Lewis acid catalysts, have been developed. They were shown to be active for the acceptorless dehydrogenative coupling of alcohols and amines to selectively form imines, while suppressing undesired C═N hydrogenation. Notably, both molecular H₂ as reductive gas and imine as a readily reducible product are produced simultaneously. The POM-Ag/Al₂O₃ catalysts were easily synthesized by selective adsorption of basic polyoxoniobate [Nb₆O₁₉]^8- on AgNPs, with loading controlled by the concentration of aqueous K₈Nb₆O₁₉, without the passivation of Lewis acid sites on the Al₂O₃ support. The desired imines were efficiently produced by tri-functional catalysis of POM-Ag/Al₂O₃ through the following two-step sequence: the acceptorless dehydrogenation of alcohols to form aldehydes and H₂ at the interface between AgNPs and basic [Nb₆O₁₉]^8-, followed by the dehydrative condensation of amines and aldehydes on Lewis acid sites of Al₂O₃. The cationic AgNP surface stabilized key intermediates for proton abstraction by [Nb₆O₁₉]^8-. Heteroassociation of hydrogen species occurred rapidly at the [Nb₆O₁₉]^8-/Ag interface, effectively suppressing imine hydrogenation even under H₂. This work highlights selective imine synthesis accompanied by H₂ evolution under completely acceptorless conditions using Ag-based catalysts decorated by basic POMs.