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31.
Nanocrystalline TiO2, via green combustion synthesis,as an efficient and reusable catalyst for the preparation of 1,8‐dioxooctahydroxanthenes and 1,8‐dioxodecahydroacridines 下载免费PDF全文
Nanocrystalline TiO2 is synthesized using a green combustion method and used as a recyclable catalyst for the one‐pot multicomponent synthesis of 1,8‐dioxodecahydroacridines and 1,8‐dioxooctahydroxanthenes, under solvent‐free conditions. This method is mild, environmentally friendly, inexpensive and highly effective for obtaining good to excellent yields of the products. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
32.
Dr. Yoko Hasegawa Dr. Thomas Cantin Dr. Jonathan Decaens Dr. Samuel Couve-Bonnaire Prof. Dr. André B. Charette Prof. Dr. Thomas Poisson Prof. Dr. Philippe Jubault 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(47):e202201438
The first diastereo- and enantioselective cyclopropanation reactions of electron-deficient allenes with donor-acceptor and diacceptor diazo reagents are described. The desired enantioenriched alkylidenecyclopropanes (ACPs) were obtained in high yields with high diastereo- and enantioselectivities in the presence of Rh2((S)-TCPTAD)4 or Rh2((R)-BTPCP)4 catalysts (up to 95 % yield, >95 : 5 d.r. and 99 : 1 e.r.). This methodology gave a direct access to ACPs bearing multiple electron-deficient substituents and allows to further expand the availability of ACPs chemistry. Interestingly, during the examination of the scope of this reaction, the asymmetric intramolecular C−H insertion reaction into tert-butyl group was observed as a side reaction with up to 94 : 6 e.r. 相似文献
33.
Zhengcheng Wang Shangyan Zhou Wei Liao Qian Zhou Meida Chen Jin Long Prof. Qingmei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(66):e202201987
The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt1Fe3@NC/MWCNTs catalyst with moderate Fe3+ feeding content (0.86 mA/mgPt) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mgPt). Furthermore, the CO oxidation initial potential of Pt1Fe3@NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt1Fe3@NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field. 相似文献
34.
Yueqiang Cao Hao Zhang Shufang Ji Zhijun Sui Zheng Jiang Dingsheng Wang Francisco Zaera Xinggui Zhou Xuezhi Duan Yadong Li 《Angewandte Chemie (International ed. in English)》2020,59(28):11647-11652
Atomic regulation of metal catalysts has emerged as an intriguing yet challenging strategy to boost product selectivity. Here, we report a density functional theory‐guided atomic design strategy for the fabrication of a NiGa intermetallic catalyst with completely isolated Ni sites to optimize acetylene semi‐hydrogenation processes. Such Ni sites show not only preferential acetylene π‐adsorption, but also enhanced ethylene desorption. The characteristics of the Ni sites are confirmed by multiple characterization techniques, including aberration‐corrected high‐resolution scanning transmission electron microscopy and X‐ray absorption spectrometry measurements. The superior performance is also confirmed experimentally against a Ni5Ga3 intermetallic catalyst with partially isolated Ni sites and against a Ni catalyst with multi‐atomic ensemble Ni sites. Accordingly, the NiGa intermetallic catalyst with the completely isolated Ni sites shows significantly enhanced selectivity to ethylene and suppressed coke formation. 相似文献
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36.
《Journal of Saudi Chemical Society》2020,24(2):216-222
In this work, thiocarbohydrazide doped iron nanoparticles as a novel, green, heterogeneous, and inexpensive catalyst is reported. This catalyzed the three components reaction of dialkylacetylenedicarboxylate with aromatic aldehydes and aromatic amines to yield the corresponding furan derivatives EtOH. An indispensable part of green chemistry is to be able to recover and reuse catalysts without any notable drop in catalytic activity. The analysis of catalyst and application of that for the synthesis of title compounds in high yields reveal this property. The formation, size of the metal ions present in the material is confirmed by powdered X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). 相似文献
37.
Zhitao Cui Wei Du Chengwei Xiao Qiaohong Li Rongjian Sa Chenghua Sun Zuju Ma 《Frontiers of Physics》2020,15(6):63502
MoS2 is a promising candidate for hydrogen evolution reaction (HER), while its active sites are mainly distributed on the edge sites rather than the basal plane sites. Herein, a strategy to overcome the inertness of the MoS2 basal surface and achieve high HER activity by combining single-boron catalyst and compressive strain was reported through density functional theory (DFT) computations. The ab initio molecular dynamics (AIMD) simulation on B@MoS2 suggests high thermodynamic and kinetic stability. We found that the rather strong adsorption of hydrogen by B@MoS2 can be alleviated by stress engineering. The optimal stress of −7% can achieve a nearly zero value of ΔGH (~ −0.084 eV), which is close to that of the ideal Pt–SACs for HER. The novel HER activity is attributed to (i) the B– doping brings the active site to the basal plane of MoS2 and reduces the band-gap, thereby increasing the conductivity; (ii) the compressive stress regulates the number of charge transfer between (H)–(B)–(MoS2), weakening the adsorption energy of hydrogen on B@MoS2. Moreover, we constructed a SiN/B@MoS2 heterojunction, which introduces an 8.6% compressive stress for B@MoS2 and yields an ideal ΔGH. This work provides an effective means to achieve high intrinsic HER activity for MoS2. 相似文献
38.
39.
《Journal of Saudi Chemical Society》2020,24(9):663-672
Nanoscaled palladium particles supported on graphitic carbon nitride (Pd0/g-C3N4) is prepared to improve the oxygen transfer in Wacker oxidation via chemical reduction method. From the analysis of FT-IR, XRD, SEM, TEM, XPS and ICP, Pd0 particles are firmly combined with g-C3N4 layers, and sub-surface ones occupy most of the components. It is worth mentioning that graphene oxide (GO), which is completely recyclable without further pollution, can be used as a ‘solid weak acid’ taking the place of H2SO4 and CF3COOH. Under the optimization conditions, as many as 46 kinds of olefins are transferred into corresponding products with satisfactory yields, and o-methyl styrene gets the highest yield of 94%. After five times of recycling experiment, the yield of acetophenone only decreases by about 7.0% in the uniform reaction process. In virtue of former research results and molecular electrostatic potential, a possible mechanism is put forward to explain the catalytic process. 相似文献
40.
Dr. Yong-Sheng Wei Dr. Liming Sun Miao Wang Dr. Jinhua Hong Dr. Lianli Zou Hongwen Liu Dr. Yu Wang Dr. Mei Zhang Dr. Zheng Liu Prof. Yinwei Li Prof. Satoshi Horike Prof. Kazu Suenaga Prof. Qiang Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):16147-16156
Understanding the thermal aggregation behavior of metal atoms is important for the synthesis of supported metal clusters. Here, derived from a metal–organic framework encapsulating a trinuclear FeIII2FeII complex (denoted as Fe3) within the channels, a well-defined nitrogen-doped carbon layer is fabricated as an ideal support for stabilizing the generated iron nanoclusters. Atomic replacement of FeII by other metal(II) ions (e.g., ZnII/CoII) via synthesizing isostructural trinuclear-complex precursors (Fe2Zn/Fe2Co), namely the “heteroatom modulator approach”, is inhibiting the aggregation of Fe atoms toward nanoclusters with formation of a stable iron dimer in an optimal metal–nitrogen moiety, clearly identified by direct transmission electron microscopy and X-ray absorption fine structure analysis. The supported iron dimer, serving as cooperative metal–metal site, acts as efficient oxygen evolution catalyst. Our findings offer an atomic insight to guide the future design of ultrasmall metal clusters bearing outstanding catalytic capabilities. 相似文献