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81.
A novel method of the synthesis of molybdovanadophosphoric heteropoly acid solutions 总被引:1,自引:0,他引:1
A novel eco-friendly method of the synthesis of aqueous solutions of the Keggintype Mo-V-P heteropoly acids H3+x
PV
x
Mo12−x
O40 (HPA-x) is proposed. At the first stage, V2O5 is dissolved in cooled H2O2 to form peroxyvanadic compounds, which spontaneously decompose to yield a H6V10O28 solution. The latter is stabilized by the addition of H3PO4 to yield a H9PV14O42 solution that is added to a boiling aqueous suspension of (H3PO4 + MoO3). This suspension is gradually evaporated producing the HPA-x solution. This safe and practically wasteless method holds much promise for the preparation of HPA-x solutions with x = 2–6. 相似文献
82.
Dr. Sandip Kumar Das Dr. Satyajit Roy Prof. Dr. Buddhadeb Chattopadhyay 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202210912
Over the past few years, the development of efficient methods to construct high-valued N-heterocyclic molecules have received massive attention owing to their extensive application in the areas of medicinal chemistry, drug discovery, natural product synthesis and so on. To access those high-valued N-heterocycles, many methods have been developed. In this context, transition-metal-catalyzed denitrogenative annulation of 1,2,3-triazoles and 1,2,3,4-tetrazoles has appeared as a powerful synthetic tool because it offers a step- and atom-economical route for the preparation of the nitrogen-rich molecules. Compared with the denitrogenative annulation of various 1,2,3-triazole frameworks, annulation of 1,2,3,4-tetrazole remains more challenging due to the inertness of the tetrazole moiety. This Review summarizes the significant achievements made in the field of denitrogenative annulation of various 1,2,3-triazoles and 1,2,3,4-tetrazoles including some pioneering examples in this area of research. We anticipate that this denitrogenative annulation reaction will find broad applications in the pharmaceutical industry, drug discovery and other fields of medicinal chemistry. 相似文献
83.
Bin Wu Tianxiao Sun Ya You Haibing Meng Dulce M. Morales Mailis Lounasvuori Abbas Beheshti Askari Li Jiang Feng Zeng Baoshan Hu Xiangzhi Zhang Renzhong Tai Zhichuan J. Xu Tristan Petit Liqiang Mai 《Angewandte Chemie (International ed. in English)》2023,62(27):e202219188
Metal/nitrogen-doped carbons (M−N−C) are promising candidates as oxygen electrocatalysts due to their low cost, tunable catalytic activity and selectivity, and well-dispersed morphologies. To improve the electrocatalytic performance of such systems, it is critical to gain a detailed understanding of their structure and properties through advanced characterization. In situ X-ray absorption spectroscopy (XAS) serves as a powerful tool to probe both the active sites and structural evolution of catalytic materials under reaction conditions. In this review, we firstly provide an overview of the fundamental concepts of XAS and then comprehensively review the setup and application of in situ XAS, introducing electrochemical XAS cells, experimental methods, as well as primary functions on catalytic applications. The active sites and the structural evolution of M−N−C catalysts caused by the interplay with electric fields, electrolytes and reactants/intermediates during the oxygen evolution reaction and the oxygen reduction reaction are subsequently discussed in detail. Finally, major challenges and future opportunities in this exciting field are highlighted. 相似文献
84.
Xue Li Xue Wen Prof. Dr. Junyu Lang Yan Wei Jie Miao Xiangcheng Zhang Baoxue Zhou Prof. Dr. Mingce Long Prof. Dr. Pedro J. J. Alvarez Prof. Dr. Lizhi Zhang 《Angewandte Chemie (International ed. in English)》2023,62(27):e202303267
High-valent metal-oxo (HVMO) species are powerful non-radical reactive species that enhance advanced oxidation processes (AOPs) due to their long half-lives and high selectivity towards recalcitrant water pollutants with electron-donating groups. However, high-valent cobalt-oxo (CoIV=O) generation is challenging in peroxymonosulfate (PMS)-based AOPs because the high 3d-orbital occupancy of cobalt would disfavor its binding with a terminal oxygen ligand. Herein, we propose a strategy to construct isolated Co sites with unique N1O2 coordination on the Mn3O4 surface. The asymmetric N1O2 configuration is able to accept electrons from the Co 3d-orbital, resulting in significant electronic delocalization at Co sites for promoted PMS adsorption, dissociation and subsequent generation of CoIV=O species. CoN1O2/Mn3O4 exhibits high intrinsic activity in PMS activation and sulfamethoxazole (SMX) degradation, highly outperforming its counterpart with a CoO3 configuration, carbon-based single-atom catalysts with CoN4 configuration, and commercial cobalt oxides. CoIV=O species effectively oxidize the target contaminants via oxygen atom transfer to produce low-toxicity intermediates. These findings could advance the mechanistic understanding of PMS activation at the molecular level and guide the rational design of efficient environmental catalysts. 相似文献
85.
Zhen-Hua Zhao Jia-Run Huang Prof. Pei-Qin Liao Prof. Xiao-Ming Chen 《Angewandte Chemie (International ed. in English)》2023,62(22):e202301767
The development of efficient electrocatalysts with non-copper metal sites for electrochemical CO2 reduction reactions (eCO2RR) to hydrocarbons and oxygenates is highly desirable, but still a great challenge. Herein, a stable metal–organic framework (DMA)4[Sn2(THO)2] (Sn-THO, THO6− = triphenylene-2,3,6,7,10,11-hexakis(olate), DMA = dimethylammonium) with isolated and distorted octahedral SnO62− active sites is reported as an electrocatalyst for eCO2RR, showing an exceptional performance for eCO2RR to the CH4 product rather than the common products formate and CO for reported Sn-based catalysts. The partial current density of CH4 reaches a high value of 34.5 mA cm−2, surpassing most reported copper-based and all non-Cu metal-based catalysts. Our experimental and theoretical results revealed that the isolated SnO62− active site favors the formation of key *OCOH species to produce CH4 and can greatly inhibit the formation of *OCHO and *COOH species to produce *HCOOH and *CO, respectively. 相似文献
86.
87.
Hong Zhang Bin Song Weiwei Zhang Bowen An Lin Fu Songtao Lu Yingwen Cheng Qianwang Chen Ke Lu 《Angewandte Chemie (International ed. in English)》2023,62(6):e202217009
The sluggish polysulfide redox kinetics and the uncontrollable sulfur speciation pathway, leading to serious shuttling effect and high activation barrier associated with sulfur cathode. We describe here the use of core–shell structured composite matrixes containing abundant catalytic sites for nearly fully reversible cycling of sulfur cathodes for Na-S batteries. The bidirectional tandem electrocatalysis provide successive reversible conversion of both long- and short-chain polysulfides, whereas Fe2O3 accelerates Na2S8/Na2S6 to Na2S4 conversion and the redox-active Fe(CN)64−-doped polypyrrole shell catalyzes Na2S4 reduction to Na2S. The electrochemically reactive Na2S can be readily charged back to sulfur with minimal overpotential. Simultaneously, stable cycling of Na-S pouch cell with a high reversible capacity of 696 mAh g−1 is also demonstrated. The bidirectional confined tandem catalysis renders the manipulation of sulfur redox electrochemistry for practical Na-S cells. 相似文献
88.
Adrien Bessaguet Quentin Blancart-Remaury Pauline Poinot Isabelle Opalinski Sébastien Papot 《Angewandte Chemie (International ed. in English)》2023,62(6):e202216787
Rotaxanes and molecular knots exhibit particular properties resulting from the presence of a mechanical bond within their structure that maintains the molecular components interlocked in a permanent manner. On the other hand, the disassembly of the interlocked architecture through the breakdown of the mechanical bond can activate properties which are masked in the parent compound. Herein, we present the development of stimuli-responsive CuI-complexed [2]catenanes as OFF/ON catalysts for the copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction. The encapsulation of the CuI ion inside the [2]catenanes inhibits its ability to catalyze the formation of triazoles. In contrast, the controlled opening of the two macrocycles induces the breaking of the mechanical bond, thereby restoring the catalytic activity of the CuI ion for the CuAAC reaction. Such OFF/ON catalysts can be involved in signal amplification processes with various potential applications. 相似文献
89.
Dr. Ali M. Abdel-Mageed Dr. Bunyarat Rungtaweevoranit Dr. Sarawoot Impeng Dr. Joachim Bansmann Dr. Jabor Rabeah Dr. Shilong Chen Thomas Häring Dr. Supawadee Namuangrak Dr. Kajornsak Faungnawakij Prof. Dr. Angelika Brückner Prof. Dr. R. Jürgen Behm 《Angewandte Chemie (International ed. in English)》2023,62(30):e202301920
Elucidating the reaction mechanism in heterogeneous catalysis is critically important for catalyst development, yet remains challenging because of the often unclear nature of the active sites. Using a molecularly defined copper single-atom catalyst supported by a UiO-66 metal–organic framework (Cu/UiO-66) allows a detailed mechanistic elucidation of the CO oxidation reaction. Based on a combination of in situ/operando spectroscopies, kinetic measurements including kinetic isotope effects, and density-functional-theory-based calculations, we identified the active site, reaction intermediates, and transition states of the dominant reaction cycle as well as the changes in oxidation/spin state during reaction. The reaction involves the continuous reactive dissociation of adsorbed O2, by reaction of O2,ad with COad, leading to the formation of an O atom connecting the Cu center with a neighboring Zr4+ ion as the rate limiting step. This is removed in a second activated step. 相似文献
90.
Dongwen Guo Kai Jiang Hui Gan Yanwei Ren Prof. Jinxing Long Prof. Yingwei Li Prof. Biaolin Yin 《Angewandte Chemie (International ed. in English)》2023,62(39):e202304662
Developing well-defined structures and desired properties for porous organic polymer (POP) supported catalysts by controlling their composition, size, and morphology is of great significance. Herein, we report a preparation of polyaniline (PANI) supported Pd nanoparticles (NPs) with controllable structure and morphology. The protocol involves the introduction of MnO2 with different crystal structures (α, β, γ, δ, ϵ) serving as both the reaction template and the oxidant. The different forms of MnO2 each convert aniline to a PANI that contains a unique regular distribution of benzene and quinone. This leads to the Pd/PANI catalysts with different charge transfer properties between Pd and PANI, as well as different dispersions of the metal NPs. In this case, the Pd/ϵ-PANI catalyst greatly improves the turnover frequency (TOF; to 88.3 h−1), in the reductive coupling of furfural derivatives to potential bio-based plasticizers. Systematic characterizations reveal the unique oxidation state of the support in the Pd/ϵ-PANI catalyst and coordination mode of Pd that drives the formation of highly dispersed Pd nanoclusters. Density functional theory (DFT) calculations show the more electron rich Pd/PANI catalyst has the lower energy barrier in the oxidative addition step, which favors the C−C coupling reaction. 相似文献