共查询到20条相似文献,搜索用时 15 毫秒
1.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(24):6963-6967
This study elucidates an innovative mechanochemical approach applying Friedel–Crafts alkylation to synthesize porous covalent triazine frameworks (CTFs). Herein, we pursue a counterintuitive approach by utilizing a rather destructive method to synthesize well‐defined materials with intrinsic porosity. Investigating a model system including carbazole as monomer and cyanuric chloride as triazine node, ball milling is shown to successfully yield porous polymers almost quantitatively. We verified the successful structure formation by an in‐depth investigation applying XPS, solid‐state NMR and FT‐IR spectroscopy. An in situ study of pressure and temperature developments inside the milling chamber in combination with two‐dimensional liquid‐state NMR spectroscopy reveals insights into the polymerization mechanism. The versatility of this mechanochemical approach is showcased by application of other monomers with different size and geometry. 相似文献
2.
Carsten Bolm Jos G. Hernndez 《Angewandte Chemie (International ed. in English)》2019,58(11):3285-3299
In recent years, the application of mechanical energy to chemical systems has repeatedly proven beneficial to facilitate chemical transformations in various areas in chemistry. Today, a systematic body of evidence indicates that mechanochemistry holds great promise to become a game‐changer in chemical synthesis. Not only does mechanochemistry permit access to products that are inaccessible by established means (e.g. purely thermal activation), mechanochemical reactions often outperform their solution‐based counterparts in terms of sustainability. Most mechanochemical reactions carried out by ball milling techniques involve transformations of solids and liquids, but the number of mechanochemical reactions with gaseous reactants is increasing. The aim of this Minireview is to provide an overview of recent chemical reactions involving gaseous samples by ball milling techniques and to highlight advances in ball milling technology for the safe handling of gaseous reagents. Examples of reactions proceeding at the interface of solid–/liquid–/gas–gas systems that led to significant improvements in reactivity or selectivity will also be highlighted. 相似文献
3.
Erik Troschke Sven Grätz Dr. Tilo Lübken Dr. Lars Borchardt 《Angewandte Chemie (International ed. in English)》2017,56(24):6859-6863
This study elucidates an innovative mechanochemical approach applying Friedel–Crafts alkylation to synthesize porous covalent triazine frameworks (CTFs). Herein, we pursue a counterintuitive approach by utilizing a rather destructive method to synthesize well-defined materials with intrinsic porosity. Investigating a model system including carbazole as monomer and cyanuric chloride as triazine node, ball milling is shown to successfully yield porous polymers almost quantitatively. We verified the successful structure formation by an in-depth investigation applying XPS, solid-state NMR and FT-IR spectroscopy. An in situ study of pressure and temperature developments inside the milling chamber in combination with two-dimensional liquid-state NMR spectroscopy reveals insights into the polymerization mechanism. The versatility of this mechanochemical approach is showcased by application of other monomers with different size and geometry. 相似文献
4.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(9):2485-2488
In situ ball milling of solid catalysts is a promising yet almost unexplored concept for boosting catalytic performance. The continuous preferential oxidation of CO (CO‐PROX) under in situ ball milling of Cu‐based catalysts such as Cu/Cr2O3 is presented. At temperatures as low as −40 °C, considerable activity and more than 95 % selectivity were achieved. A negative apparent activation energy was observed, which is attributed to the mechanically induced generation and subsequent thermal healing of short‐lived surface defects. In situ ball milling at sub‐zero temperatures resulted in an increase of the CO oxidation rate by roughly 4 orders of magnitude. This drastic and highly selective enhancement of CO oxidation showcases the potential of in situ ball milling in heterogeneous catalysis. 相似文献
5.
Laboratory Real‐Time and In Situ Monitoring of Mechanochemical Milling Reactions by Raman Spectroscopy 下载免费PDF全文
Dr. Davor Gracin Dr. Vjekoslav Štrukil Prof. Tomislav Friščić Dr. Ivan Halasz Dr. Krunoslav Užarević 《Angewandte Chemie (International ed. in English)》2014,53(24):6193-6197
Mechanistic understanding of mechanochemical reactions is sparse and has been acquired mostly by stepwise ex situ analysis. We describe herein an unprecedented laboratory technique to monitor the course of mechanochemical transformations at the molecular level in situ and in real time by using Raman spectroscopy. The technique, in which translucent milling vessels are used that enable the collection of a Raman scattering signal from the sample as it is being milled, was validated on mechanochemical reactions to form coordination polymers and organic cocrystals. The technique enabled the assessment of the reaction dynamics and course under different reaction conditions as well as, for the first time, direct insight into the behavior of liquid additives during liquid‐assisted grinding. 相似文献
6.
Karen J. Ardila‐Fierro Carsten Bolm Jos G. Hernndez 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(37):13079-13083
A mechanochemical synthesis of one‐dimensional carbon allotrope carbyne model compounds, namely tetraaryl[n]cumulenes (n=3, 5) was realized. Central for the mechanosynthesis of the cumulenic carbon nanostructures were the development of a mechanochemical Favorskii alkynylation‐type reaction and the implementation of a solvent‐free, acid‐free reductive elimination with tin(II) chloride by ball milling. 相似文献
7.
Direct In Situ Investigation of Milling Reactions Using Combined X‐ray Diffraction and Raman Spectroscopy 下载免费PDF全文
M. Sc. Lisa Batzdorf Dipl.‐Chem. Franziska Fischer Dipl.‐Chem. Manuel Wilke Dipl.‐Ing. Klaus‐Jürgen Wenzel Dr. Franziska Emmerling 《Angewandte Chemie (International ed. in English)》2015,54(6):1799-1802
The combination of two analytical methods including time‐resolved in situ X‐ray diffraction (XRD) and Raman spectroscopy provides a new opportunity for a detailed analysis of the key mechanisms of milling reactions. To prove the general applicability of our setup, we investigated the mechanochemical synthesis of four archetypical model compounds, ranging from 3D frameworks through layered structures to organic molecular compounds. The reaction mechanism for each model compound could be elucidated. The results clearly show the unique advantage of the combination of XRD and Raman spectroscopy because of the different information content and dynamic range of both individual methods. The specific combination allows to study milling processes comprehensively on the level of the molecular and crystalline structures and thus obtaining reliable data for mechanistic studies. 相似文献
8.
Christian Schumacher Jos G. Hernndez Carsten Bolm 《Angewandte Chemie (International ed. in English)》2020,59(38):16357-16360
The formation and regeneration of active CuI species is a fundamental mechanistic step in copper‐catalyzed atom transfer radical cyclizations (ATRC). Typically, the presence of the catalytically active CuI species in the reaction mixture is secured by using high CuI catalyst loadings or the addition of complementary reducing agents. In this study it is demonstrated how the piezoelectric properties of barium titanate (BaTiO3) can be harnessed by mechanical ball milling to induce electrical polarization in the strained piezomaterial. This strategy enables the conversion of mechanical energy into electrical energy, leading to the reduction of a CuII precatalyst into the active CuI species in copper‐catalyzed mechanochemical solvent‐free ATRC reactions. 相似文献
9.
Production of Magnetic Nano‐bioconjugates via Ball Milling of Commercial Boron Powder with Biomolecules 下载免费PDF全文
Okan Icten Narayan Sadashiv Hosmane Dursun Ali Kose Birgul Zumreoglu‐Karan 《无机化学与普通化学杂志》2016,642(14):828-832
Mechanochemical preparation and characterization of surface‐functionalized magnetic boron nanoparticles for biomedical applications are presented. Alloying with the stainless steel ball milling material during mechanochemical activation proved to be an alternative route to introduce magnetic properties to the nanomaterials, while functionalization with biomolecules provided biocompatible surfaces for bioconjugation. 相似文献
10.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(48):15454-15458
Although mechanochemical synthesis is becoming more widely applied and even commercialised, greater basic understanding is needed if the field is to progress on less of a trial‐and‐error basis. We report that a mechanochemical reaction in a ball mill exhibits unusual sigmoidal feedback kinetics that differ dramatically from the simple first‐order kinetics for the same reaction in solution. An induction period is followed by a rapid increase in reaction rate before the rate decreases again as the reaction goes to completion. The origin of these unusual kinetics is found to be a feedback cycle involving both chemical and mechanical factors. During the reaction the physical form of the reaction mixture changes from a powder to a cohesive rubber‐like state, and this results in the observed reaction rate increase. The study reveals that non‐obvious and dynamic rheological changes in the reaction mixture must be appreciated to understand how mechanochemical reactions progress. 相似文献
11.
Li Yuan Zhenhua Chen Yonghua Zhu Xuanming Liu Hongdong Liao Ding Chen 《Applied biochemistry and biotechnology》2012,167(1):39-51
Wheat straw is one of the major lignocellulosic plant residues in many countries including China. An attractive alternative is the utilization of wheat straw for bioethanol production. This article mainly studies a simple one-step wet milling with Penicillium simplicissimum and weak acid to hydrolysis of wheat straw. The optimal condition for hydrolysis was ball milling 48?h in citrate solvent (pH?=?4) with P. simplicissimum H5 at the speed of 500?rpm and the yield of sugar increased with increased milling time. Corresponding structure transformations before and after milling analyzed by X-ray diffraction, transmission Fourier transform infrared spectroscopy, and environmental scanning electron microscopy clearly indicated that this combined treatment could be attributed to the crystalline and chemical structure changes of cellulose in wheat straw during ball milling. This combined treatment of ball milling, mild acid, and fungus hydrolysis enabled the conversion of the wheat straw. Compared with traditional method of ball milling, this work showed a more simple, novel, and environmentally friendly way in mechanochemical treatment of wheat straw. 相似文献
12.
A novel mechanochemical method of preparation of maleic anhydride grafted polypropylene (MAPP) was developed. The preparation was performed by ball milling of polypropylene (PP) powder, maleic anhydride (MA), and peroxide initiator in balls-containing jars with a planetary ball mill for a certain time. Compared with the conventional melt-mixing method, MAPP obtained through ball-milling technique reveals higher graft degree, particularly alleviated degradation of PP, or even increased molecular mass of the resulting MAPP. Maleic anhydride grafted polyethylene (MAPE) was obtained via this technique, and the optimization of the technique is in progress. The novel technique offers new opportunities in modification of polyolefins, which has also the advantages of solventless, lower process temperature, energy efficient, low cost, and simple running process. Furthermore, it is very easy to obtain purified products. 相似文献
13.
Hannes Kulla Sebastian Haferkamp Irina Akhmetova Mathias Röllig Dr. Christiane Maierhofer Prof. Dr. Klaus Rademann Dr. Franziska Emmerling 《Angewandte Chemie (International ed. in English)》2018,57(20):5930-5933
We present an in situ triple coupling of synchrotron X‐ray diffraction with Raman spectroscopy, and thermography to study milling reactions in real time. This combination of methods allows a correlation of the structural evolution with temperature information. The temperature information is crucial for understanding both the thermodynamics and reaction kinetics. The reaction mechanisms of three prototypical mechanochemical syntheses, a cocrystal formation, a C?C bond formation (Knoevenagel condensation), and the formation of a manganese‐phosphonate, were elucidated. Trends in the temperature development during milling are identified. The heat of reaction and latent heat of crystallization of the product contribute to the overall temperature increase. A decrease in temperature occurs via release of, for example, water as a by‐product. Solid and liquid intermediates are detected. The influence of the mechanical impact could be separated from temperature effects caused by the reaction. 相似文献
14.
用行星式球磨机或振荡式球磨机作为机械能发生装置,水(50 μL)或DMF(50 μL)或甲醇(150 μL)作为球磨过程中滴加的辅助溶剂,分别研究了烟酸(HNA)和氧化锌、烟酸和碱式碳酸锌的机械化学反应。 结果表明,当上述的2个化学反应在行星式球磨机(45 Hz)或在振荡式球磨机(20 Hz)中球磨30 min,少量水或者DMF均可以促使生成零维的四水合二烟酸锌(Ⅱ):[Zn(NA)2(H2O)4]。 在行星式球磨机中球磨烟酸、氧化锌和少量水的混合物,在15 Hz条件下球磨30 min,只产生少量目标产物,当球磨时间延长为60 min可生成大量目标产物,而且达到反应平衡。 相似文献
15.
Farit Kh. Urakaev 《Mendeleev Communications》2012,22(2):103-105
A kinetic equation was derived for the mechanochemical preparation of nanosystems by a dilution method; the equation was used to calculate mechanical activation times necessary for the completion of exchange reactions and mass-transfer coefficients in ball milling. 相似文献
16.
Y.H. Taufiq-Yap C.K. Goh G.J. Hutchings N. Dummer J.K. Bartley 《Journal of molecular catalysis. A, Chemical》2006,260(1-2):24-31
Modification by using mechanochemical treatment of vanadium phosphate catalysts on the microstructure, morphology, oxygen nature and catalytic performance for n-butane oxidation is described and discussed. In this work, the precursor, VOHPO4·0.5H2O prepared by reduction of VOPO4·2H2O by isobutyl alcohol was subjected to a high energy planetary ball mill for 30, 60 and 120 min in ethanol. The ball milling process reduced the crystallite size of the catalysts and consequently increased their surface area. The morphologies of the milled catalysts are dependent on milling time. The highest reactivity and mobility of the lattice oxygen species has been achieved by the catalyst milled for 60 min with lower reduction peak temperature and higher amount of oxygen atoms removed. The oxygen species removed from the active V4+ phase was shown to be correlated with the rate of reaction. A good relationship was also found between the oxygen species associated with V5+ and maleic anhydride selectivity. However, a larger amount of this oxygen species will give a deleterious effect on the conversion rate. The present study demonstrate that the mechanochemical method (with an appropriate duration) effectively enhanced the catalytic activity by increasing the surface area and controlling the reactivity, and that the amount of oxygen species contributed to the partial oxidation of n-butane to maleic anhydride. 相似文献
17.
C. Gabriela Avila-Ortiz Mario Pérez-Venegas Jorge Vargas-Caporali Eusebio Juaristi 《Tetrahedron letters》2019,60(27):1749-1757
In recent years, sustainable organocatalysis has become a relevant target in asymmetric organic synthesis. Among the most successful strategies to achieve “greener” organocatalyzed processes are (1) the elimination of solvent from reaction media, and (2) the use of alternative activation energies such as solvent-free mechanochemistry in high speed ball mills. In recent years we have stepped up efforts in the pursuit of organocatalysts and biocatalysts that allow reactions to take place in the absence of solvent and under mechanochemical activation. In this article we present the application of small dipeptides as chiral organocatalysts under solvent-free and high-speed ball milling conditions, with focus on the asymmetric aldol addition reaction. Finally, we report on recent results using supported enzymes for the resolution of racemic β-amino acids and amines, under mechanochemical conditions. 相似文献
18.
Gréta Gergely Ferenc Wéber István Lukács Levente Illés Attila L. Tóth Zsolt E. Horváth Judit Mihály Csaba Balázsi 《Central European Journal of Chemistry》2010,8(2):375-381
Hydroxyapatite (HAp) was successfully produced from recycled eggshell, seashell and phosphoric acid. The phases obtained depended
on the ratio of calcined eggshell/ seashell to phosphoric acid, the calcination temperature and the mechanochemical activation
method (ball milling or attrition milling). The HAp structures were characterized by X-ray diffraction, scanning electron
microsopy and infrared spectroscopy. Attrition milling was more effective than ball milling, yielding nanosize, homogenous
and pure Hap.
相似文献
19.
Vincent M. Morin Dr. Patrick M. J. Szell Estelle Caron-Poulin Dr. Bulat Gabidullin Prof. Dr. David L. Bryce 《ChemistryOpen》2019,8(11):1328-1336
The halogen bond has previously been explored as a versatile tool in crystal engineering and anion coordination chemistry, with mechanochemical synthetic techniques having been shown to provide convenient routes towards cocrystals. In an effort to expand our knowledge on the role of halogen bonding in anion coordination, here we explore a series of cocrystals formed between 3-iodoethynylpyridine and 3-iodoethynylbenzoic acid with halide salts. In total, we report the single-crystal X-ray structures of six new cocrystals prepared by mechanochemical ball milling, with all structures exhibiting C≡C−I⋅⋅⋅X− (X=Cl, Br) halogen bonds. Whereas cocrystals featuring a pyridine group favoured the formation of discrete entities, cocrystals featuring a benzoic acid group yielded an alternation of halogen and hydrogen bonds. The compounds studied herein were further characterized by 13C and 31P solid-state nuclear magnetic resonance, with the chemical shifts offering a clear and convenient method of identifying the occurrence of halogen bonding, using the crude product obtained directly from the mechanochemical ball milling. Whereas the 31P chemical shifts were quickly able to identify the occurrence of cocrystallization, 13C solid-state NMR was diagnostic of both the occurrence of halogen bonding and of hydrogen bonding. 相似文献
20.
Ramon Groote Lennart van Haandel Rint P. Sijbesma 《Journal of polymer science. Part A, Polymer chemistry》2012,50(23):4929-4935
We have investigated the effect of the concentration and molecular weight on the activity of polymeric silver(I)‐NHC (NHC = N‐heterocyclic carbene) catalyst complexes in ultrasound‐induced mechanochemical catalyst activation. A strong dependence of the turnover number (TON) on initial catalyst concentration was observed in the transesterification of vinyl acetate with benzyl alcohol. The main findings of this study are that the concentration and molecular weight effects on TON are caused by competition between mechanochemical catalyst activation and deactivation, most likely by reactive species produced during the sonication process. Performing the transesterification reaction under radical‐suppressing conditions resulted in a significant increase of TON. This result clearly demonstrates the increased catalyst lifetime when reducing the amount of sonochemical impurities, and it highlights the importance of controlling and suppressing secondary, sonochemical processes when using ultrasound‐induced mechanochemical generation of reactive species such as catalysts. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献