A Generalized Strategy for the Synthesis of Large-Size Ultrathin Two-Dimensional Metal Oxide Nanosheets

Two-dimensional (2D) nanomaterials show unique electrical, mechanical, and catalytic performance owing to their ultrahigh surface-to-volume ratio and quantum confinement effects. However, ways to simply synthesize 2D metal oxide nanosheets through a general and facile method is still a big challenge. Herein, we report a generalized and facile strategy to synthesize large-size ultrathin 2D metal oxide nanosheets by using graphene oxide (GO) as a template in a wet-chemical system. Notably, the novel strategy mainly relies on accurately controlling the balance between heterogeneous growth and nucleation of metal oxides on the surface of GO, which is independent on the individual character of the metal elements. Therefore, ultrathin nanosheets of various metal oxides, including those from both main-group and transition elements, can be synthesized with large size. The ultrathin 2D metal oxide nanosheets also show controllable thickness and unique surface chemical state.     

A TPD‐MS study of the interaction of coumarins and their heterocyclic derivatives with a surface of fumed silica and nanosized oxides CeO2/SiO2, TiO2/SiO2, Al2O3/SiO2

The interactions between coumarins and the surface of fumed SiO₂, CeO₂/SiO₂, TiO₂/SiO₂ and Al₂O₃/SiO₂ were assessed by means of temperature‐programed desorption mass spectrometry. The different stages of the thermolysis of coumarin were identified and an analysis of the underlying reactions was performed. The kinetic parameters of the involved reactions were thus obtained. The decomposition of thiazolyl‐substituted coumarins was found to proceed through a ‘thiazole–thiazine’ ring expansion in the adsorbed state. A linear correlation between the sigma constants (Σσ) of the coumarin substituents and the activation energy of CO₂ formation was obtained. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparative Study of Sol-Gel and Coprecipitated Ni-Al Hydrotalcites

Hydrotalcite is an anionic clay mineral (layered double hydroxide) whose general formula is [M(II)_1–x M(III) _x (OH)₂] ^x+X _x/n ^n– ·mH₂O. Anionic clays with a hydrotalcite-type are widely used as useful precursors of multicomponent catalysts. Hydrotalcites with Ni/Al molar ratio 2.5 have been synthesised both by the coprecipitation method, starting with nickel and aluminium nitrates and by the sol-gel method, using nickel acetylacetonate and aluminium isopropylate as precursors. The NiO-Al₂O₃ oxidic forms have been obtained by the thermal treatment of the precursors at 450°C and 900°C, respectively, and were characterised by DTA, XRD, IR spectroscopy and temperature programmed reduction (TPR). TPR clearly demonstrated a higher reducibility of the oxidic forms derived from the sol-gel synthesised precursors.     

The calixarene cavity – binding site or refuge?

Consideration of the Hirshfeld surfaces for some simple inclusion complexes of p-t-butyltetrathiacalix[4]arene and a number of its metal ion derivatives indicates that a bound metal ion can significantly influence the nature of the interactions between the included molecule and the cavity. These interactions do, however, vary with the degree of deprotonation of the calixarene, the particular nature of the bound metal ion and, in some cases, with the extent of exo-cavity interactions of the included species. The possible influences of inclusion interactions on the catalytic activity of metallocalixarenes are assessed.     

高温燃煤钙基纳米金属氧化物复合吸附剂同时除砷脱硫研究

将纳米MgO、Al2O3和ZnO分别添加于超细CaCO3中制备出钙基纳米金属氧化物复合吸附剂,并进行燃煤过程中除砷脱硫的试验研究。结果表明,在Ca/S摩尔比为1.8,燃烧温度为1200℃,纳米金属氧化物的添加量为超细CaCO3质量的8%时,添加了纳米MgO的复合吸附剂除砷脱硫性能最好,比单一的超细CaCO3除砷率和脱硫率分别高出了28.73%和37.21%,表现出同时除砷脱硫的良好性能。     

钯催化选择性构筑(Z)-[3]戟烯反应研究

本工作发展了钯催化下芳甲醛对甲苯磺酰腙与膦酰基取代联烯的偶联反应, 顺利地以中等至良好的收率及较高的立体选择性制备了一系列(Z)-[3]戟烯衍生物. 不同于烷基取代的苯磺酰腙与烯烃的简单偶联, 该反应使用芳甲醛对甲苯磺酰腙作为底物, 经由1,3-钯迁移历程成功构筑了两个C=C双键. 在最优反应条件下, 该反应展示了较宽的底物适用范围和较高的立体选择性. 最终以31个反应实例获得一系列(Z)-[3]戟烯衍生物, 最高79%分离产率和>20:1 Z/E选择性, 为(Z)-[3]戟烯衍生物的合成应用提供了简便高效的方法.     

Sigma/pi Bonding Preferences of Solvated Alkali-Metal Cations to Ditopic Arylmethyl Anions

Arylmethyl anions allow alkali-metals to bind in a σ-fashion to the lateral carbanionic centre or a π-fashion to the aryl ring or in between these extremities, with the trend towards π bonding increasing on descending group 1. Here we review known alkali metal structures of diphenylmethane, fluorene, 2-benzylpyridine and 4-benzylpyridine. Next, we synthesise Li, Na, K monomers of these diarylmethyls using polydentate donors PMDETA or Me₆TREN to remove competing oligomerizing interactions, studying the effect that two aromatic rings has on negative charge (de)localisation via NMR, X-ray crystallographic and DFT studies. Diphenylmethyl and fluorenyl anions maintain C(H)−M interactions regardless of alkali-metal, although the adjacent arene carbons engage in interactions with larger alkali-metals. Introducing a nitrogen atom into the ring (at the 2- or 4-position) encourages relocalisation of negative charge away from the deprotonated carbon and onto nitrogen. Phenyl(2-pyridyl)methyl moves from an enamide formation at one extremity (lithium) to an aza-allyl formation at the other extremity (potassium), while C- or N-coordination modes become energetically viable for Na and K phenyl(4-pyridyl)methyl complexes.