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1.
Over the past two decades, advanced materials with hollow interiors have received significant attention in materials research owing to their great application potential across a vast number of technological fields. Though with great difficulty, multi-shelled hollow metal–organic frameworks (MSHMs) have also been successfully synthesized in recent years. Herein, a rational shell-by-shell soft-templating protocol has been devised to fabricate highly uniform multi-shelled hollow cobalt-imidazole-based MOF (ZIF-67). For the first time, it has become possible to endow mesoporosity to this new type of functional material (i.e., mesoporous MOFs). When used as carrier materials in catalytic reactions, in principle, these mesoporous MSHMs with high surface area not only improve the dispersity of metal nanoparticles (NPs), but also efficiently facilitate the mass diffusion of the reactions, resulting in enhanced catalyst activity. Moreover, the obtained MSHMs/M nanocomposites serve as base-metal bifunctional catalysts for one-pot oxidation-Knoevenagel condensation cascade reaction, in which the MSHMs itself serves as a pristine active catalyst in addition to its role of catalyst support. The results demonstrate that excellent multifunctional catalysts can be achieved via preparing intrinsically microporous bulk MOFs into extrinsically mesoporous MSHMs which possess many structural merits that conventional bulk MOFs do not have. 相似文献
2.
Dekun Wu Dr. Qing Xu Dr. Jing Qian Prof. Xiaopeng Li Prof. Yuhan Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3105-3111
Covalent organic frameworks (COFs) are a new class of crystalline porous polymers comprised mainly of carbon atoms, and are versatile for the integration of heteroatoms such as B, O, and N into the skeletons. The designable structure and abundant composition render COFs useful as precursors for heteroatom-doped porous carbons for energy storage and conversion. Herein, we describe a multifunctional electrochemical catalyst obtained through pyrolysis of a bimetallic COF. The catalyst possesses hierarchical pores and abundant iron and cobalt nanoparticles embedded with standing carbon layers. By integrating these features, the catalyst exhibits excellent electrochemical catalytic activity in the oxygen reduction reaction (ORR), with a 50 mV positive half-wave potential, a higher limited diffusion current density, and a much smaller Tafel slope than a Pt-C catalyst. Moreover, the catalyst displays superior electrochemical performance toward the hydrogen evolution reaction (HER), with overpotentials of −0.26 V and −0.33 V in acidic and alkaline aqueous solution, respectively, at a current density of 10 mA cm−2. The overpotential in the catalysis of the oxygen evolution reaction (OER) was 1.59 V at the same current density. 相似文献
3.
The detailed characterization of multifunctional hybrid organosilazane/organosilylamine telechelic oligomers by IR and 1H, 13C and 29Si NMR spectroscopy in one and two dimenions has been undertaken. The specific multifunctional oligomers, comprising NH/NH2 or SiCl functionalities depending on the monomer feed-ratio, were prepared from mono- and di-functionally reacted dichlorodimethylsilane (DDS) and mono-, di-, tri- and tetra-functionally reacted ethylenediamine (EDA). Varying the feed-ratio afforded control of the microstructures of the oligomers and the preparation of oligomers with, in some cases, conterminously located silicon–chlorine (SiCl) groups. The combination of the NMR methods with the IR technique has enabled the detailed microstructural characterization of the oligomers and the identification of the functionalities therein. This approach and the knowledge gained from the DDS/EDA system has been applied to the microstructural characterization of other hybrid organosilazane/silylamine preceramic telechelic oligomers. 相似文献
4.
Hiroji Fukui Mitsuo Sawamoto Toshinobu Higashimura 《Journal of polymer science. Part A, Polymer chemistry》1994,32(14):2699-2708
Telechelic ( 8 ) and end-functionalized four-arm star polymers ( 9 ) were synthesized through the coupling reactions of end-functionalized living poly(isobutyl vinyl ether) ( 5; DP n ~ 10) with the bi-and tetrafunctional silyl enol ethers, H4-nC? [CH2OC6H4C(OSiMe3) = CH2]n ( 3: n = 2; 4: n = 4). The precursor polymers 5 were prepared by living cationic polymerization with functionalized initiators, CH3CH(Cl)OCH2CH2X(6), in conjunction with zinc chloride in methylene chloride at ?15°C. The initiators 6 were obtained by the addition of hydrogen chloride gas to vinyl ethers bearing pendant functional groups X , including acetoxy [? OC(O)CH3], styryl (? OCH2C6H4-p-CH = CH2), and methacryloyl [? OC(O)C(CH3) = CH2]. The coupling reactions with 3 and 4 in methylene chloride at ?15°C for 24 h afforded the end-functionalized multiarmed polymers ( 8 and 9 ) in high yield (>91%), where those with styryl or methacryloyl groups are new multifunctional macromonomers. © 1994 John Wiley & Sons, Inc. 相似文献
5.
6.
Miguel Clemente-León Eugenio Coronado Carlos J. Gómez-García Eugenia Martínez-Ferrero 《Journal of Cluster Science》2002,13(3):381-407
The use of polyoxometalates (pOM's) as inorganic component in the synthesis of new molecular hybrid materials is presented. Here we show that the combination of organic molecules of the tetrathiafulvalene (TTF) type or perylene (per) with POM's yields new radical salts with unprecedented structures that present interesting magnetic and/or electrical properties or coexistence of both. The first true metallic radical salt containing a POM has been prepared and characterized. We also describe the recent results obtained by combining magnetic POM's with the organometallic cation decamethylferrocene. 相似文献
7.
8.
Synthesis of multi‐functionalized carbonyl compounds by palladium–catalysed γ‐substitution of MBH adducts with activated amides 下载免费PDF全文
Gao Pei‐Sen Zhang Jin‐Lei Li Ning Zheng Zhan Jiang Yuan Yang Gao Zi‐Wei Zhang Weiqiang Xu Li‐Wen 《应用有机金属化学》2018,32(3)
Catalytic allylic γ‐substitution with Morita‐Baylis‐Hillman (MBH) adducts for creating a new family of unsymmetrical dicarbonyl compounds was presented in this work, in which a variety of allylated amide products were achieved in good yields and high regioselectivity with excellent linear‐to‐branched ratios. Especially, it was found that the Pd/HZNU‐Phos complex exhibited remarkably high activity (with a TON up to 16800) in this transformation between dicarbonyl amides and MBH adducts. In addition, the possibly multisite interaction between multifunctional Pd/HZNU‐Phos catalyst system and substrates might responsible for its exceptionally high efficiency in this reaction. 相似文献
9.
Green solvent approach for printable large deformation thermoplastic elastomer based piezoresistive sensors and their suitability for biomedical applications 下载免费PDF全文
Bruna F. Gonçalves Pedro Costa Juliana Oliveira Sylvie Ribeiro Vitor Correia Gabriela Botelho Senentxu Lanceros‐Mendez 《Journal of Polymer Science.Polymer Physics》2016,54(20):2092-2103
Composites based on biocompatible thermoplastic elastomer styrene‐ethylene/butylene‐styrene (SEBS) as matrix and multi‐walled carbon nanotubes (MWCNT) as nanofillers show excellent mechanical and piezoresistive properties from low to large deformations. The MWCNT/SEBS composites have been prepared following a green solvent approach, to extend their range of applicability to biomedical applications. The obtained composites with 2, 4, and 5 wt % MWCNT content provide suitable piezoresistive response up to 80% deformation with a piezoresistive sensibility near 2.7, depending on the applied strain and MWCNT content. Composite sensors were also developed by spray and screen printing and integrated with an electronic data acquisition system with RF communication. The possibility to accurately control the composites properties and performance by varying MWCNT content, viscosity, and mechanical properties of the polymer matrix, shows the large potential of the system for the development of large deformation printable piezoresistive sensors. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2092–2103 相似文献
10.
以共沉淀法制备出Fe3O4纳米粒子,通过聚乙烯亚胺(PEI)修饰Fe3O4纳米粒子,再原位复合上Au纳米粒子,制得Fe3O4/PEI/Au纳米颗粒微球。再将Fe3O4/PEI/Au纳米颗粒与巯基乙酸修饰的量子点CdSe/CdS连接,成功制备了Fe3O4/PEI/Au@CdSe/CdS多功能复合微球。经过傅里叶变换红外光谱仪(FTIR)、荧光分光光度计、荧光显微镜、X射线衍射(XRD)、透射电子显微镜(TEM)及振动样品磁强计(VSM)的表征。结果表明:多功能复合微球的粒径在40 nm左右,具有超顺磁性,剩磁,矫顽力近似等于零,饱和磁化强度为28.83 A·m2·kg-1,同时兼有优越的荧光性能和金纳米粒子的特性。 相似文献