Structure Modification Function of g‐C3N4 for Al2O3 in the In Situ Hydrothermal Process for Enhanced Photocatalytic Activity

Heterojunctions of g‐C₃N₄/Al₂O₃ (g‐C₃N₄=graphitic carbon nitride) are constructed by an in situ one‐pot hydrothermal route based on the development of photoactive γ‐Al₂O₃ semiconductor with a mesoporous structure and a high surface area (188 m²g^?1) acting as electron acceptor. A structure modification function of g‐C₃N₄ for Al₂O₃ in the hydrothermal process is found, which can be attributed to the coordination between unoccupied orbitals of the Al ions and lone‐pair electrons of the N atoms. The as‐synthesized heterojunctions exhibit much higher photocatalytic activity than pure g‐C₃N₄. The hydrogen generation rate and the reaction rate constant for the degradation of methyl orange over 50 % g‐C₃N₄/Al₂O₃ under visible‐light irradiation (λ>420 nm) are 2.5 and 7.3 times, respectively, higher than those over pristine g‐C₃N₄. The enhanced activity of the heterojunctions is attributed to their large specific surface areas, their close contact, and the high interfacial areas between the components as well as their excellent adsorption performance, and efficient charge transfer ability.     

Hydrogels Triggered by Metal Ions as Precursors of Network CuS for DNA Detection

The gelation behavior of lithocholate (LC^?) with different metal ions in water was investigated. The microstructures of hydrogels were determined to be three‐dimensional (3D) networks of fibrous aggregates. The formation of fibrils was speculated to be mainly driven by the coordination between carboxylate of LC^? and metal ions, accompanied by the assistance of noncovalent interactions such as electrostatic and hydrophobic interactions. The hydrogels, which can maintain the mechanical strength at higher temperature, exhibit thermal stability. Their gelation capability was enhanced with the increase in acidity. The hydrogels of LC^? and Cu²⁺ mixtures served as the precursors for producing network nanostructures of CuS nanoparticles. These new CuS networks exhibit high fluorescence quenching ability and can act as an effective fluorescent sensing platform for ssDNA detection.     

MoS2 Nanosheets Supported on 3D Graphene Aerogel as a Highly Efficient Catalyst for Hydrogen Evolution

The development of efficient catalysts for electrochemical hydrogen evolution is essential for energy conversion technologies. Molybdenum disulfide (MoS₂) has emerged as a promising electrocatalyst for hydrogen evolution reaction, and its performance greatly depends on its exposed edge sites and conductivity. Layered MoS₂ nanosheets supported on a 3D graphene aerogel network (GA‐MoS₂) exhibit significant catalytic activity in hydrogen evolution. The GA‐MoS₂ composite displays a unique 3D architecture with large active surface areas, leading to high catalytic performance with low overpotential, high current density, and good stability.     

Surface and Structural Investigation of a MnOx Birnessite‐Type Water Oxidation Catalyst Formed under Photocatalytic Conditions

Catalytically active MnO_x species have been reported to form in situ from various Mn‐complexes during electrocatalytic and solution‐based water oxidation when employing cerium(IV) ammonium ammonium nitrate (CAN) oxidant as a sacrificial reagent. The full structural characterization of these oxides may be complicated by the presence of support material and lack of a pure bulk phase. For the first time, we show that highly active MnO_x catalysts form without supports in situ under photocatalytic conditions. Our most active ⁴MnO_x catalyst (～0.84 mmol O₂ mol Mn^?1 s^?1) forms from a Mn₄O₄ bearing a metal–organic framework. ⁴MnO_x is characterized by pair distribution function analysis (PDF), Raman spectroscopy, and HR‐TEM as a disordered, layered Mn‐oxide with high surface area (216 m²g^?1) and small regions of crystallinity and layer flexibility. In contrast, the ^SMnO_x formed from Mn²⁺ salt gives an amorphous species of lower surface area (80 m²g^?1) and lower activity (～0.15 mmol O₂ mol Mn^?1 s^?1). We compare these catalysts to crystalline hexagonal birnessite, which activates under the same conditions. Full deconvolution of the XPS Mn2p_3/2 core levels detects enriched Mn³⁺ and Mn²⁺ content on the surfaces, which indicates possible disproportionation/comproportionation surface equilibria.     

Highly Segregated Lamello‐Columnar Mesophase Organizations and Fast Charge Carrier Mobility in New Discotic Donor–Acceptor Triads

Four new donor–acceptor triads (D–A–D) based on discotic and arylene mesogens have been synthesized by using Sonogashira coupling and cyclization reactions. This family of triads consists of two side‐on pending triphenylene mesogens, acting as the electron‐donating groups (D), laterally connected through short lipophilic spacers to a central perylenediimide (PI), benzo[ghi]perylenediimide (BI), or coronenediimide (CI) molecular unit, respectively, playing the role of the electron acceptor (A). All D–A–D triads self‐organize to form a lamello‐columnar oblique mesophase, with a highly segregated donor–acceptor (D–A) heterojunction organization, consequent to efficient molecular self‐sorting. The structure consists in the regular alternation of two disrupted rows of triphenylene columns and a continuous row of diimine species. High‐resolution STM images demonstrate that PI‐TP2 forms stable 2D self‐assembly nanostructures with some various degrees of regularity, whereas the other triads do not self‐organize into ordered architectures. The electron‐transport mobility of CI‐TP2, measured by time‐of‐flight at 200 °C in the mesophase, is one order of magnitude higher than the hole mobility. By means of this specific molecular designing idea, we realized and demonstrated for the first time the so‐called p–n heterojunction at the molecular level in which the electron‐rich triphenylene columns act as the hole transient pathways, and the coronenediimide stacks form the electron‐transport channels.     

Total Syntheses of (−)‐Isoschizogamine and (−)‐2‐Hydroxyisoschizogamine

Total syntheses of (?)‐isoschizogamine and (?)‐2‐hydroxyisoschizogamine are described. The synthesis employs two asymmetric Michael additions to establish chiral centers at C7 and the quaternary carbon C20. Regioselective reduction of the methylthioiminium cation rather than the enamine generates an isoschizogamine‐type pentacyclic skeleton. Acidic hydrolysis of the isoschizogamine‐type intermediate in the absence of oxygen provides natural (?)‐isoschizogamine. Conducting the reaction in the presence of oxygen leads to a multistep oxidative hydrolysis cascade that affords unnatural (?)‐2‐hydroxyisoschizogamine.     

A Convenient Palladium‐Catalyzed Carbonylative Suzuki Coupling of Aryl Halides with Formic Acid as the Carbon Monoxide Source

A practical palladium‐catalyzed carbonylative Suzuki coupling of aryl halides under carbon monoxide gas‐free conditions has been developed. Here, formic acid was utilized as the carbon monoxide source for the first time with acetic anhydride as the additive. A variety of diarylketones were produced in moderate to excellent yields from the corresponding aryl halides and arylboronic acids.     

Thermal and environmental stability of poly(4-ethynyl-p-xylylene-co-p-xylylene) thin films

The aim of this paper was to test the thermal and environmental stability of poly(4-ethynyl-p-xylyleneco-p-xylylene) thin films prepared by chemical vapor deposition(CVD) and to optimize the reaction conditions of the polymer.Fourier transformed infrared spectroscopy(FTIR),thermogravimetric analysis(TGA) and fluorescence microscopy were employed to investigate the stability of the reactive polymer coatings in various environmental conditions.Chemical reactivity of the thin films were then tested by Huisgen 1,3-dipolar cycloaddition reaction(‘‘click' reaction).The alkyne functional groups on poly(4-ethynyl-p-xylylene-co-p-xylylene) thin films were found to be stable under ambient storage conditions and thermally stable up to 100 8C when annealed at 0.08 Torr in argon.We also optimized the click reaction conditions of azide-functionalized molecules with poly(4-ethynyl-p-xylylene-co-p-xylylene).The best reaction result was achieved,when copper concentration was 0.5 mmol/L,sodium ascorbate concentration to copper concentration was 5:1.In contrast,the azide concentration and temperature had no obvious effect on the surface reaction.     

Characterization and reactivity of γ-Al_2O_3 supported Pd–Ni bimetallic nanocatalysts for selective hydrogenation of cyclopentadiene

Several g-Al2O3 supported Pd–Ni bimetallic nanocatalysts(Pd–Ni(x:y)/Al2O3; where x and y represent the mass ratio of Pd and Ni, respectively) were prepared by the impregnation method and used for selective hydrogenation of cyclopentadiene to cyclopentene. The Pd–Ni/Al2O3 samples were confirmed to generate Pd–Ni bimetallic nanoparticles by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM). The catalytic activity was assessed in view of the effects of different mass ratios of Pd and Ni, temperature, pressure, etc. Among all the samples, the Pd–Ni(1:1)/Al2O3(PN-1:1) catalyst showed extremely high catalytic ability. The conversion of cyclopentadiene and selectivity for cyclopentene can be simultaneously more than 90%.