Latest ArticlesThe oxygen reduction reaction (ORR) is a crucial process in Zn-air systems, and the catalyst plays a significant role in this reaction. However, reported catalysts often suffer from poor durability and stability during the ORR process. Herein, we synthesized La-Fe bimetallic nanoparticles encapsulated in a N-doped porous carbon dodecahedron (La-Fe/NC) originated from ZIF-8 by a simple direct carbonization. The La-Fe/NC catalyst had a numerous mesopores and dendritic outer layer generated by carbon nanotubes (CNTs), forming a high conductivity network that helped to optimize electron transfer and mass transport in the ORR process. The effect of different doping transition metals and metal ratios on the ORR activity of Zn-air batteries was investigated. In alkaline media, the La-Fe/NC showed the highest ORR catalytic activity, with a half-wave potential (E1/2) of 0.879 V (vs. RHE, Pt/C 0.845 V). After 5000 cycles, the E1/2 of the La-Fe/NC catalyst only decreased by 7 mV, and its performance in stability tests and methanol tolerance tests was superior to Pt/C. When used as the air electrode in a Zn-air battery, the La-Fe/NC catalyst demonstrated an excellent specific capacity of 755 mAh/g and a peak power density of 179.8 mW/cm2. The results provide important insights for the development of high-performance Zn-air batteries and new directions for the design of ORR catalysts.
Axially chiral binaphthol have achieved great success in asymmetric catalysis. Compared to α-binaphthol, axially chiral aryl-β-naphthol are far less reported. Here, we report a method of asymmetric catalysis to construct β-naphthol with up to 99% yield, 95.5:4.5 enantiomeric ratio, using alkynyl esters as precursors and chiral phosphonic acid (CPA)/Lewis acid as catalysts. Key steps involve oxygen transfer and de novo arene formation to set up the chiral axis. Moreover, this methodology provides a versatile platform for structurally divergent synthesis of atroposelective β-naphthol analogs, which are widely found in bioactive molecules and asymmetric catalysts.
High-efficient rubber antioxidants for enhanced heat resistance without compromising mechanical properties remain an enormous and long-term challenge for the rubber industry. Herein, we employed the in-situ growth of Ce-doped Co-metal-organic framework (CeCo-MOF) in dendritic mesoporous organosilica nanoparticles (DMONs@CeCo-MOF, denoted as DCCM) to prepare a novel antioxidant that exhibit outstanding thermal stability. Dendritic mesoporous organosilica nanoparticles (DMONs) effectively alleviated the incompatibility of CeCo-MOF in the polymer matrix, and the effective scavenging of free radicals was attributed to the various oxidation states of metal ions in CeCo-MOF. Surprising, by adding only 0.5 phr (parts per hundred of rubber) of DMONs@CeCo-MOF to silicone rubber, (SR), the retention rate of tensile strength increased from 37.3% to 61.6% after aging 72 h at 250 ℃, and the retention rate of elongation at break of DCCM/SR1 composites reached 68%, which was 5.43 times of SR. The strategy of anchoring MOFs on the surface of silica also provides a viable method for preparing effective compound functionalized rubber antioxidant.
Pyrrolobenzoxazines are a rare terpene-amino acid family of natural products with potent biological activities. Here, we reported the full biosynthetic pathway of paeciloxazine (1), a typical pyrrolobenzoxazine, with significant insecticidal activity. Base on heterologous expression, chemical complement experiment, and in vitro biochemical assays, we demonstrated the sesquiterpene portion of 1 derived from discontinuously oxidations of amorphdiene, in which P450 monooxygenase PaxH catalyzed a cascade of hydroxylation and epoxidation, while two flavin dependent monooxygenases are involved in the transformation of the esterified tryptophan into a pyrrolobenzoxazine core. Furthermore, a total of 15 compounds were generated through heterologous expression, of which 13, 17 and 20 showed potential antiepileptic activity. This study fully elucidated the biosynthetic pathway of paeciloxazine (1) and showed the diversity and complexity of constructing natural products by organisms.
Piperidine is a crucial pharmacophore and a special scaffold in the realm of drug discovery. Its flexibility increases the molecule's capability to bind to the receptor. The piperidine-containing compounds are distinguished by their remarkable activity, and are increasingly becoming a vital category of pesticides. In this review, the research progress of piperidines in the discovery of pesticides was updated according to their active characteristics. The structure-activity relationships (SARs), and mechanisms of action of piperidine-containing compounds were also discussed. This article is meant to enable readers to quickly understand piperidines, while providing ideas for creating piperidines with novel structures and unique mechanisms of action.
Leveraging the interplay between the metal component and the supporting material represents a cornerstone strategy for augmenting electrocatalytic efficiency, e.g., electrocatalytic CO2 reduction reaction (CO2RR). Herein, we employ freestanding porous carbon fibers (PCNF) as an efficacious and stable support for the uniformly distributed SnO2 nanoparticles (SnO2PCNF), thereby capitalizing on the synergistic support effect that arises from their strong interaction. On one hand, the interaction between the SnO2 nanoparticles and the carbon support optimizes the electronic configuration of the active centers. This interaction leads to a noteworthy shift of the d-band center toward stronger intermediate adsorption energy, consequently lowering the energy barrier associated with CO2 reduction. As a result, the SnO2PCNF realizes a remarkable CO2RR performance with excellent selectivity towards formate (98.1%). On the other hand, the porous carbon fibers enable the uniform and stable dispersion of SnO2 nanoparticles, and this superior porous structure of carbon supports can also facilitate the exposure of the SnO2 nanoparticles on the reaction interface to a great extent. Consequently, adequate contact between active sites, reactants, and electrolytes can significantly increase the metal utilization, eventually bringing forth a remarkable 7.09 A/mg mass activity. This work might provide a useful idea for improving the utilization rate of metals in numerous electrocatalytic reactions.
Available online Alkaline water electrolysis (AWE) is a prominent technique for obtaining a sustainable hydrogen source and effectively managing the energy infrastructure. Noble metal-based electrocatalysts, owing to their exceptional hydrogen binding energy, exhibit remarkable catalytic activity and long-term stability in the hydrogen evolution reaction (HER). However, the restricted accessibility and exorbitant cost of noble-metal materials pose obstacles to their extensive adoption in industrial contexts. This review investigates strategies aimed at reducing the dependence on noble-metal electrocatalysts and developing a cost-effective alkaline HER catalyst, while considering the principles of sustainable development. The initial discussion covers the fundamental principle of HER, followed by an overview of prevalent techniques for synthesizing catalysts based on noble metals, along with a thorough examination of recent advancements. The subsequent discussion focuses on the strategies employed to improve noble metal-based catalysts, including enhancing the intrinsic activity at active sites and increasing the quantity of active sites. Ultimately, this investigation concludes by examining the present state and future direction of research in the field of electrocatalysis for the HER.
A supramolecular assembly composed of perylene diimide derivative (PDI-nm) and nor-seco-cucurbit[10]uril (ns-Q[10]) was designed. The excellent host-guest interaction between PDI-nm and ns-Q[10] prevented the aggregation-caused quenching (ACQ) effect of PDI-nm, resulting in a luminescent assembly. The addition of spermine to the PDI-nm/ns-Q[10] assembly restored the ACQ of PDI-nm due to the competitive binding of spermine to ns-Q[10], which released PDI-nm. The assembly based on this principle showed ultra-high sensitivity for the detection of spermine with a detection limit as low as 7.84 × 10−7 mol/L in aqueous solution and 3.69 × 10−7 mol/L in plasma solution. Moreover, an artificial light-harvesting system based on this assembly was proposed, benefiting from its good luminescent performance. Nile red (NiR) functioned as an acceptor loaded into assembly, and a highly efficient energy transfer process occurred from PDI-nm/ns-Q[10] to NiR, with an efficiency up to 87%.
Surface with well-defined components and structures possesses unique electronic, magnetic, optical and chemical properties. As a result, surface chemistry research plays a crucial role in various fields such as catalysis, energy, materials, quantum, and microelectronics. Surface science mainly investigates the correspondence between surface property and functionality. Scanning probe microscopy (SPM) techniques are important tools to characterize surface properties because of the capability of atomic-scale imaging, spectroscopy and manipulation at the single-atom level. In this review, we summarize recent advances in surface electronic, magnetic and optical properties characterized mainly by SPM-based methods. We focus on elucidating the π-magnetism in graphene-based nanostructures, construction of spin qubits on surfaces, topology properties of surface organic structures, STM-based light emission, tip-enhanced Raman spectroscopy and integration of machine learning in SPM studies.
A transition-metal- and oxidant-free amination/cyclization reaction to access 1,2,4-triazolo[1,5-a]pyridines was realized in water by using amino diphenylphosphinate as amino source. A broad array of readily accessible N-(pyridyl)amides could be converted into the products featuring a diverse set of functional groups. The sustainable methodology was successfully applied to the late-stage functionalization of natural products and drugs.
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