ChemCatChem最新文献

Palladium-catalyzed carbonylative C─C coupling reactions provide an efficient route to synthesize natural products and pharmaceuticals through three-component condensation processes. However, the use of gaseous carbon monoxide (CO) – a colorless, odorless, and toxic gas – has hindered its broad adoption as a C1 source. Addressing this, the development of versatile CO-releasing molecules (CORMs) and user-friendly, nongaseous palladium-catalyzed carbonylation techniques have emerged as a crucial research area. This review outlines recent advancements in the application of CORMs to palladium-catalyzed carbonylative C─C coupling reactions, with a focus on CO generation mechanisms and carbonyl utilization efficiency. CORMs are classified into three categories: single carbon monoxide releasing molecules (s-CORMs), multiple carbon monoxide releasing molecules (m-CORMs), and binary metal carbonyl compounds (BMCCs). By offering a comprehensive overview of the current research landscape and providing practical guidelines for CORM selection, this review aims to assist researchers in developing effective carbonylative strategies.

The development of cost-effective and highly efficient catalysts for the hydrogen evolution reaction (HER), particularly in alkaline environments, is a critical challenge for hydrogen applications. One promising approach involves the alloying of noble metals with transition metals. This study presents the synthesis of PtNi nanorod catalysts, characterized by a thickness of 500 nm, which were fabricated via magnetron sputtering onto nickel foam. When evaluated in a 1 M KOH electrolyte, the Pt–Ni alloy demonstrates superior HER performance compared with both Ni and Pt, exhibiting an overpotential of 35 mV at 10 mA/cm² and a Tafel slope of 29 mV/dec. The enhanced catalytic activity is attributed to several factors, including a high electrochemically active surface area, increased mass activity, elevated turnover frequency, and reduced electrochemical impedance. Furthermore, the Pt–Ni catalyst maintains remarkable stability at a current density of 10 mA/cm² over a duration of 100 h. The improved HER performance is ascribed to the nanorod architecture, which features a high density of grain boundaries, as well as the synergistic interactions between Ni and Pt.

With the extensive use of fossil fuels and CO₂ emission, the development of effective electrocatalysts to convert CO₂ into high-value-added chemical products has become an important issue in academia community. Single-atom alloys (SAA) integrate the advantages of single-atoms catalysts and alloys, which can improve the activity and selectivity of CO₂ electroreduction (CO₂RR) by adjusting the electronic and geometric structure of the host and guest metals simultaneously. This article provides a comprehensive review on the research advances of SAA catalysts used for CO₂RR, including the synthesis and characterizations, computational design, experimental performances, and electronic structure effects of different SAA. Specifically, the correlations between experimental results and theoretical studies have been highlighted and discussed clearly in this review, which provide unique fundamental insights on the CO₂RR performances of SAA catalysts. Based on these understanding, we finally propose a workflow combining both computational and experimental methods to rationally design the SAA, which can help the further development of CO₂RR catalysts in the future.

A key challenge in modern society is developing the sustainable processes for producing vital chemicals, such as hydrocarbons, from renewable raw materials. The OX-ZEO process, which uses bifunctional catalysts to convert syngas into hydrocarbons, offers a potential alternative to the nonsustainable cracking process. Combining oxide materials with zeolites enables the direct synthesis of various hydrocarbon products with high selectivity. However, challenges remain, particularly regarding carbon monoxide (CO) conversion and unwanted carbon dioxide (CO₂) generation. This study explores the impact of bimetallic chromites combined with H-MOR zeolite on the reaction outcome. Comparative experiments using only the oxide versus the bifunctional catalyst revealed a clear link between the methanol synthesis activity of the oxide and the overall activity in the OX-ZEO process. Furthermore, catalytic tests with monometallic oxides paired with H-MOR highlighted the role of the oxide's crystal structure in syngas conversion. These findings offer insights into the oxide–zeolite interactions, enabling the development of improved catalyst combinations that enhance the CO conversion, reduce CO₂ formation, and maintain high product selectivity.

The valorization of CO₂ into organic carbonates through its cycloaddition to epoxides has garnered significant attention in catalysis. However, the reaction is often hindered by low selectivity, and a key challenge is the development of catalysts capable of effectively activating both CO₂ and epoxides simultaneously. In this study, we prepared and characterized a catalyst comprising isolated zinc single atoms dispersed on carbon nitride for the selective CO₂ conversion to cyclic carbonates. The monoatomic nature and homogeneous distribution of the zinc species were confirmed utilizing advanced characterization methods, including X-ray absorption spectroscopy and aberration-corrected scanning transmission electron microscopy. The catalyst activity and recyclability were validated through catalytic tests with epichlorohydrin as a model epoxydic compound, and the study scope was subsequently extended to include a wide range of functionalized epoxides. Density functional theory calculations were performed to elucidate the reaction mechanism, revealing that both CO₂ and epichlorohydrin interact with the same zinc atom in the cycloaddition process, highlighting the key role of zinc single atoms in promoting the reaction. Overall, the present study provides new insights into the design and optimization of heterogeneous catalysts for CO₂ cycloadditions, paving the way for more effective strategies in CO₂ valorization and conversion for producing valuable fine chemicals.

Hydrocarbon-based lubricants are ubiquitous in industrial applications but typically consist of complex mixtures of branched molecules that are challenging to characterize and to relate to their macroscopic properties. Consequently, lubricants are typically optimized empirically for specific applications by blending base oils with organic or inorganic additives. In this study, we report the synthesis and characterization of molecularly defined lubricants via metathesis of branched terminal olefins, followed by hydrogenation. The resulting saturated hydrocarbons are characterized by ultrahigh-field (28.2 T) ¹H and ¹³C NMR spectroscopies to establish their molecular structures and resolve different stereoisomers, showing the utility of state-of-the-art spectroscopic tools for analyzing structures of branched alkanes. Furthermore, the molecular-level diffusion and bulk viscosity properties compare favorably to classical synthetic lubricants based on hydrogenated polyalphaolefin (PAO) blends, establishing olefin metathesis as a selective and scalable route to high-performance lubricant oils with defined molecular structures.

The electrochemical reduction of nitrite (NO₂⁻) and nitrate (NO₃⁻) not only enables sustainable, circular routes to produce ammonia (NH₃), but also eliminates pollutants in groundwater. In this article, we report a facile synthesis of Ru-doped Cu nanowires on Cu foam electrodes with low Ru (0.48 wt.%) loading. The composite electrode shows high-performance in the NO₂⁻/NO₃⁻ to NH₃ electroreduction, giving NH₃ Faradaic efficiency of up to 100% and NH₃ yield rates up to 33.2 mg h⁻¹ cm⁻² at −0.2 V versus RHE in NO₂⁻ reduction. For the nitrate-to-ammonia reduction, the electrode also shows high activity with Faradaic efficiency of 88.4% (at −0.6 V versus RHE) and a yield rate of 62.5 mg h⁻¹ cm⁻² (at −1.0 V versus RHE). We show that the electrode can easily be integrated into a Zn–nitrite battery, giving a power density of 9.1 mW cm⁻², a NH₃ yield rate of 1.88 mg h⁻¹ cm⁻² and a nitrite-to-ammonia Faradaic efficiency of 88.9% at a current density of 20 mA cm⁻². The system combines three productive outputs, that is removal of NO_x⁻ pollutants, synthesis of valuable NH₃ and generation of “green” electricity.

Nonstandard amino acids (nsAAs) that are l-phenylalanine derivatives with aryl ring functionalization have long been harnessed in natural product synthesis, therapeutic peptide synthesis, and diverse applications of genetic code expansion. Yet, to date, these chiral molecules have often been the products of poorly enantioselective and environmentally harsh organic synthesis routes. Here, we reveal the broad specificity of multiple natural pyridoxal 5′-phosphate (PLP)-dependent enzymes, specifically an l-threonine transaldolase, a phenylserine dehydratase, and an aminotransferase, toward substrates that contain aryl side chains with diverse substitutions. We exploit this tolerance to construct a one-pot biocatalytic cascade that achieves high-yield synthesis of 18 diverse l-phenylalanine derivatives from aldehydes under mild aqueous reaction conditions. We demonstrate the addition of a carboxylic acid reductase module to this cascade to enable the biosynthesis of l-phenylalanine derivatives from carboxylic acids that may be less expensive or less reactive than the corresponding aldehydes. Finally, we investigate the scalability of the cascade by developing a lysate-based route for preparative-scale synthesis of 4-formyl-l-phenylalanine, a nsAA with a bio-orthogonal handle that is not readily market-accessible. Overall, this work offers an efficient, versatile, and scalable route with the potential to lower manufacturing costs and democratize synthesis for many valuable nsAAs.

A novel PdI₄²⁻-supported catalyst, based on imidazolium-functionalized polyhedral oligomeric silsesquioxanes (POSS) functionalized with imidazolium arms grafted on amorphous silica, is prepared through a straightforward synthetic procedure allowing to accede to high local concentration spots of palladium sites surrounding the POSS core. The hybrid material was fully characterized by thermogravimetric analysis coupled with differential scanning calorimetry (TGA–DSC), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectroscopy (ICP–OES), and X-ray photoelectron spectroscopy (XPS). This material was successfully used as heterogeneous catalyst for the oxidative carbonylation of β-amino alcohols to 2-oxazolidinones as well as 2-aminopyridin-3-ol to oxazolo[4,5-b]pyridin-2(3H)-one under relatively mild conditions (100 °C for 3 h under 40 atm of a 4:1 mixture CO–air) in DME as the solvent and with aerobic oxygen as the simplest external oxidant, with the formation of water as benign coproduct. The catalyst could be successfully recycled up to four times, before beginning to undergo partial deactivation due to palladium reduction, as evidenced by XPS and TEM. ICP–OES analysis of some representative products evidenced a low metal contamination (palladium content <1 ppm), making our approach interesting for applications in the life science field, where a high degree of purity is required.

Systems for direct conversion of captured CO₂ into CO (i.e., CO₂ capture and reduction: CCR) via bifunctional catalysts have attracted attention as technologies for achieving carbon neutrality. However, the reported systems require additional heating above 623 K, which is still an issue from an ecological perspective. The present work realized selective CO production through CCR under isothermal conditions at 423 K by the application of a direct current electric field and a Pt-Na/TiO₂ catalyst. The application of an electric field to the catalyst is needed for CO₂ conversion at low temperature, and the loading of both Pt and Na is required for CO₂ capture and its selective reduction to CO. The obtained results open the door for greener CCR technologies that effectively utilize waste heat from power plants and industry.