Periodicity of Two-Dimensional Bonding of Main Group Elements

In the periodic table the position of each atom follows the ‘aufbau’ principle of the individual electron shells. The resulting intrinsic periodicity of atomic properties determines the overall behavior of atoms in two-dimensional (2D) bonding and structure formation. Insight into the type and strength of bonding is the key in the discovery of innovative 2D materials. The primary features of 2D bonding and the ensuing monolayer structures of the main-group II–VI elements result from the number of valence electrons and the change of atom size, which determine the type of hybridization. The results reveal the tight connection between strength of bonding and bond length in 2D networks. The predictive power of the periodic table reveals general rules of bonding, the bonding-structure relationship, and allows an assessment of published data of 2D materials.     

Photothermal Oxidation of Cinnamyl Alcohol with Hydrogen Peroxide Catalyzed by Gold Nanoparticle/Antimony-Doped Tin Oxide Nanocrystals

Gold nanoparticles with different mean sizes were formed on antimony-doped tin oxide nanocrystals by the temperature-varied deposition-precipitation method (Au/ATO NCs). Au/ATO NCs possess strong absorption in the near-infrared region due to Drude excitation in addition to the localized surface plasmon resonance (LSPR) of AuNPs around 530 nm. Au/ATO NCs show thermally activated catalytic activity for the oxidation of cinnamyl alcohol to cinnamaldehyde by hydrogen peroxide. The catalytic activity increases with a decrease in the mean Au particle size (d_Au) at 5.3 nm≤d_Au≤8.2 nm. Light irradiation (λ_ex >660 nm, ∼0.5 sun) of Au/ATO NCs increases the rate of reaction by more than twice with ∼95 % selectivity. Kinetic analyses indicated that the striking enhancement of the reaction stems from the rise in the temperature near the catalyst surface of ∼30 K due to the photothermal effect of the ATO NCs.     

基于内聚力模型的快速荷载下CFRP-混凝土界面剪切剥离模拟

鉴于纤维增强复合材料(Fiber Reinforced Polymer, FRP)已在混凝土结构加固中普遍应用, 能有效提高结构的承载和变形能力. 为揭示动载作用下FRP-混凝土界面的剥离机理, 本文基于ABAQUS平台, 采用内聚力模型模拟CFRP-混凝土界面层, 实现了快速荷载下CFRP-混凝土界面剥离的高效模拟. 结果表明: CFRP表面应变在加载过程中由加载端向自由端方向传递, 随着加载速率的提高, 界面承载能力也随之提高; 界面峰值剪应力也存在显著的应变率效应; 模拟结果与试验结果基本吻合, 说明了新方法的有效性.     

Polypyridine-Based Helical Amide Foldamer Channels: Rapid Transport of Water and Protons with High Ion Rejection

Synthetic strategies that enable rapid construction of covalent organic nanotubes with an angstrom-scale tubular pore remain scarcely reported. Reported here is a remarkably simple and mild one-pot polymerization protocol, employing POCl₃ as the polymerization agent. This protocol efficiently generates polypyridine amide foldamer-based covalent organic nanotubes with a 2.8 nm length at a yield of 50 %. Trapping single-file water chains in the 2.8 Å tubular cavity, rich in hydrogen-bond donors and acceptors, these tubular polypyridine ensembles rapidly and selectively transport water at a rate of 1.6×10⁹ H₂O⋅S⁻¹⋅channel⁻¹ and protons at a speed as fast as gramicidin A, with a high rejection of ions.     

Molecularly Engineered 6FDA-Based Polyimide Membranes for Sour Natural Gas Separation

Glassy polyimide membranes are attractive for industrial applications in sour natural gas purification. Unfortunately, the lack of fundamental understanding of relationships between polyimide chemical structures and their gas transport properties in the presence of H₂S constrains the design and engineering of advanced membranes for such challenging applications. Herein, 6FDA-based polyimide membranes with engineered structures were synthesized to tune their CO₂/CH₄ and H₂S/CH₄ separation performances and plasticization properties. Under ternary mixed sour gas feeds, controlling polymer chain packing and plasticization tendency of such polyimide membranes via tuning the chemical structures were found to offer better combined H₂S and CO₂ removal efficiency compared to conventional polymers. Fundamental insights into structure–property relationships of 6FDA-based polyimide membranes observed in this study offer guidance for next generation membranes for sour natural gas separation.     

Manipulating Light-Induced Dynamic Macro-Movement and Static Photonic Properties within 1D Isostructural Hydrogen-Bonded Molecular Cocrystals

Smart molecular crystals with light-driven mechanical responses have received interest owing to their potential uses in molecular machines, artificial muscles, and biomimetics. However, challenges remain in control over both the dynamic photo-mechanical behaviors and static photonic properties of molecular crystals based on the same molecule. Herein, we show the construction of isostructural co-crystals allows their light-induced cracking and jumping behaviors (photosalient effect) to be controlled. Hydrogen-bonded co-crystals from 4-(1-naphthylvinyl)pyridine ( NVP ) with co-formers (tetrafluoro-4-hydroxybenzoic acid ( THA ) and tetrafluorobenzoic acid ( TA )) crystallize as isostructural crystals, but have different static and dynamic photo-mechanical behaviors. These differences are due to alternations in the orientation of NVP and hydrogen-bonding modes of the co-formers. After light activation, the 1D NVP-TA crystal splits and shears off within 1 s. For NVP-THA , its photostability and high quantum yield give novel photonic properties, including low optical waveguide loss, highly polarized anisotropy, and efficient up-conversion fluorescence.     

Anti-Markovnikov Hydroamination of Racemic Allylic Alcohols to Access Chiral γ-Amino Alcohols

A ruthenium-catalyzed formal anti-Markovnikov hydroamination of allylic alcohols for the synthesis of chiral γ-amino alcohols is presented. Proceeding via an asymmetric hydrogen-borrowing process, the catalysis allows racemic secondary allylic alcohols to react with various amines, affording enantiomerically enriched chiral γ-amino alcohols with broad substrate scope and excellent enantioselectivities (68 examples, up to >99 % ee).     

Synthesis and characterization of VO–vanillin complex immobilized on MCM-41 and its facile catalytic application in the sulfoxidation reaction,and synthesis of 2,3-dihydroquinazolin-4(1H)-ones and disulfides in green media

In this work, a vanillin complex is immobilized onto MCM-41 and characterized by FT-IR, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetric analysis, and BET techniques. This supported Schiff base complex was found to be an efficient and recoverable catalyst for the chemoselective oxidation of sulfides into sulfoxides and thiols into their corresponding disulfides (using hydrogen peroxide as a green oxidant) and also a suitable catalyst for the preparation of 2,3-dihydroquinazolin-4(1H)-one derivatives in water at 90°C. Using this protocol, we show that a variety of disulfides, sulfoxides, and 2,3-dihydroquinazolin-4(1H)-one derivatives can be synthesized in green conditions. The catalyst can be recovered and recycled for further reactions without appreciable loss of catalytic performance.     

Structure and bonding of lanthanide dinitrogen complexes,Ln(N2)1-8

Lanthanide dinitrogen complexes, Ln(N₂) _x (x = 1-8), were investigated by Density Functional Theory computations using the B3LYP exchange-correlation functional in conjunction with quasirelativistic pseudopotentials for Ln. After a recent study on the lanthanum complexes (A. Kovács, Structural Chemistry 2018 , 29, 1825), the present study aimed to probe the changes upon variously filled 4f subshells of Ln on the structures, stabilities, and bonding properties in related complexes of Nd, Ho, and Lu. The bonding properties were assessed on the basis of natural atomic charges, Ln valence orbital populations, and analysis of bonding molecular orbitals.