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31.
Xuewen Li Dr. Shuai Yang Minghao Liu Xiubei Yang Prof. Qing Xu Prof. Gaofeng Zeng Prof. Zheng Jiang 《Angewandte Chemie (International ed. in English)》2023,62(30):e202304356
Metal-free covalent organic frameworks (COFs) have been employed to catalyze the oxygen reduction reaction (ORR). To achieve high activity and selectivity, various building blocks containing heteroatoms and groups linked by imine bonds were used to create catalytic COFs. However, the roles of linkages of COFs in ORR have not been investigated. In this work, the catalytic linkage engineering has been employed to modulate the catalytic behaviors. To create single catalytic sites while avoiding other possible catalytic sites, we synthesized COFs from benzene units linked by various bonds, such as imine, amide, azine, and oxazole bonds. Among these COFs, the oxazole-linkage in COFs enables to catalyze the ORR with the highest activity, which achieved a half-wave potential of 0.75 V and a limited current density of 5.5 mA cm−2. Moreover, the oxazole-linked COF achieved a conversion frequency (TOF) value of 0.0133 S−1, which were 1.9, 1.3, and 7.4-times that of azine-, amide- and imine-COFs, respectively. The theoretical calculation showed that the carbon atoms in oxazole linkages facilitated the formation of OOH* and promoted protonation of O* to form the OH*, thus advancing the catalytic activity. This work guides us on which linkages in COFs are suitable for ORR. 相似文献
32.
Perimetric nuclear coordinates of a triatomic molecule treat all three nuclei equivalently and are not subject to the triangle
conditions. Through an appropriate orthogonal transformation they can be separated into one scale coordinate, viz., the circumference,
and two shape coordinates, which are determined by the angles. The parameter space of the shape coordinates is an equilateral
triangle. The basic formulas are given and the relationship between points in coordinate space and molecular shapes are elucidated.
Received: 10 January 1996 / Accepted: 2 January 1997 相似文献
33.
安徽铜陵、南陵地区铜矿资源丰富,古代矿冶遗址数量众多,最早可追溯至二里头文化时期。各遗址遍地分布的炉渣、炉壁等矿冶遗物,为研究中国早期的铜矿冶炼技术提供了大量的实物资料。本工作采用X射线衍射分析（XRD）、X射线荧光分析（XRF）和扫描电镜能谱分析（SEM-EDS）等多种技术手段,对安徽铜陵、南陵地区古铜矿冶遗址的炉渣样品进行检测分析,以了解该地区早期的铜矿冶炼技术。XRD分析结果显示,所检测炉渣样品的物相以铁橄榄石、辉石、钙铁辉石为主,伴有石英、方石英、磁铁矿等矿物,符合炼铜渣的物相特征。根据炉渣的SiO2,CaO和Fe2O3的含量,可将51个炉渣样品分为三大类：Ⅰ类炉渣、Ⅱ类炉渣和Ⅲ类炉渣。其中,Ⅰ类炉渣钙、硅、铁含量较高,其CaO含量远高于Ⅱ类和Ⅲ类炉渣,为铁硅钙系。相较而言,Ⅱ类炉渣为高铁系,其Fe2O3含量明显高于Ⅰ类和Ⅲ类炉渣;Ⅲ类炉渣为高硅系,其SiO2含量较高,钙、铁含量较低。所有炉渣样品的铁含量均高于普通熔炼渣,结合其物相分析结果,可推测全部炉渣为冶炼渣。Ⅰ类、Ⅱ类炉渣的Ca和Fe含量呈现很强的负相关性,且波动范围很大,显示二者的含量并非人工调控,更可能是来自矿石中的天然成分。据此可以推测,本地区的早期工匠可能尚未认识到含钙和含铁助熔剂的作用,没有掌握不同类型铜矿石的配矿技术。SEM-EDS的分析结果表明,炉渣中的金属颗粒夹杂以冰铜、红铜和砷铜为主,表明该地区同时存在红铜和砷铜的冶炼活动。不同品位的冰铜颗粒大多来自不同遗址,尚没有在同一遗址发现较多品位依次升高的冰铜颗粒,因而难以确认冰铜熔炼环节的存在,不能证明上述遗址是否已采用了“硫化铜矿-冰铜-铜”的冶炼技术。所发现的冰铜颗粒,可能是采用硫化铜矿死焙烧工艺或混合矿原料冶炼的结果。铜陵夏家墩遗址炉渣中砷铜颗粒的存在,表明该地区早至西周时期,很可能已掌握了采用共熔还原法冶炼砷铜的技术。相关研究结果,对探讨砷铜技术的起源和传播,以及中国早期冶金技术的发展和生产组织状况均具有重要意义。 相似文献
34.
Minghao Liu Di Jiang Dr. Yubin Fu Prof. George Zheng Chen Dr. Shuai Bi Prof. Xuesong Ding Prof. Jun He Prof. Bao-Hang Han Prof. Qing Xu Prof. Gaofeng Zeng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(1):e202317015
Covalent organic frameworks (COFs) have attracted considerable attention as adsorbents for capturing and separating gold from electronic wastes. To enhance the binding capture efficiency, constructing hydrogen-bond nanotraps along the pore walls was one of the most widely adopted approaches. However, the development of absorbing skeletons was ignored due to the weak binding ability of the gold salts (Au). Herein, we demonstrated skeleton engineering to construct highly efficiently absorbs for Au capture. The strong electronic donating feature of diarylamine units enhanced the electronic density of binding sites (imine-linkage) and thus resulted in high capacities over 1750 mg g−1 for all three COFs. Moreover, the absorbing performance was further improved via the ionization of diarylamine units. The ionic COF achieved 90 % of the maximal adsorption capacity, 1.63 times of that from the charge-neutral COF within ten minutes, and showed remarkable uptakes of 1834 mg g−1, exceptional selectivity (97.45 %) and cycling stability. The theoretical calculation revealed the binding sites altering from imine bonds to ionic amine sites after ionization of the frameworks, which enabled to bind the AuCl4− via coulomb force and contributed to enhanced absorbing kinetics. This work inspires us to design molecular/ionic capture based on COFs. 相似文献
35.
Chuan Zhao Zhongfu Yan Bo Zhou Yu Pan Dr. Anjun Hu Miao He Dr. Jing Liu Prof. Dr. Jianping Long 《Angewandte Chemie (International ed. in English)》2023,62(32):e202302746
Lewis-base sites have been widely applied to regulate the properties of Lewis-acid sites in electrocatalysts for achieving a drastic technological leap of lithium-oxygen batteries (LOBs). Whereas, the direct role and underlying mechanism of Lewis-base in the chemistry for LOBs are still rarely elucidated. Herein, we comprehensively shed light on the pivotal mechanism of Lewis-base sites in promoting the electrocatalytic reaction processes of LOBs by constructing the metal–organic framework containing Lewis-base sites (named as UIO-66-NH2). The density functional theory (DFT) calculations demonstrate the Lewis-base sites can act as electron donors that boost the activation of O2/Li2O2 during the discharged-charged process, resulting in the accelerated reaction kinetics of LOBs. More importantly, the in situ Fourier transform infrared spectra and DFT calculations firstly demonstrate the Lewis-base sites can convert Li2O2 growth mechanism from surface-adsorption growth to solvation-mediated growth due to the capture of Li+ by Lewis-base sites upon discharged process, which weakens the adsorption energy of UIO-66-NH2 towards LiO2. As a proof of concept, LOB based on UIO-66-NH2 can achieve a high discharge specific capacity (12 661 mAh g−1), low discharged-charged overpotential (0.87 V) and long cycling life (169 cycles). This work reveals the direct role of Lewis-base sites, which can guide the design of electrocatalysts featuring Lewis-acid/base dual centers for LOBs. 相似文献
36.
Dr. Kaiming Cao Dr. Yang Zhu Dr. Zhuanghao Hou Dr. Manman Liu Yanyan Yang Dr. Hongze Hu Prof. Yi Dai Dr. Yu Wang Dr. Siming Yuan Prof. Guangming Huang Dr. Jiaming Mei Prof. Peter J. Sadler Prof. Yangzhong Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(1):e202215360
The unique thermodynamic and kinetic coordination chemistry of ruthenium allows it to modulate key adverse aggregation and membrane interactions of α-synuclein (α-syn) associated with Parkinson's disease. We show that the low-toxic RuIII complex trans-[ImH][RuCl4(Me2SO)(Im)] (NAMI-A) has dual inhibitory effects on both aggregation and membrane interactions of α-syn with submicromolar affinity, and disassembles pre-formed fibrils. NAMI-A abolishes the cytotoxicity of α-syn towards neuronal cells and mitigates neurodegeneration and motor impairments in a rat model of Parkinson's. Multinuclear NMR and MS analyses show that NAMI-A binds to residues involved in protein aggregation and membrane binding. NMR studies reveal the key steps in pro-drug activation and the effect of activated NAMI-A species on protein folding. Our findings provide a new basis for designing ruthenium complexes which could mitigate α-syn-induced Parkinson's pathology differently from organic agents. 相似文献
37.
Shimao Deng Ranhao Wang Xuezhen Feng Dr. Renji Zheng Shaokuan Gong Prof. Xihan Chen Yangzi Shangguan Lili Deng Huan Tang Hao Dai Prof. Lele Duan Prof. Chengyuan Liu Prof. Yang Pan Prof. Hong Chen 《Angewandte Chemie (International ed. in English)》2023,62(39):e202309625
Highly selective photoreduction of CO2 to valuable hydrocarbons is of great importance to achieving a carbon-neutral society. Precisely manipulating the formation of the Metal1⋅⋅⋅C=O⋅⋅⋅Metal2 (M1⋅⋅⋅C=O⋅⋅⋅M2) intermediate on the photocatalyst interface is the most critical step for regulating selectivity, while still a significant challenge. Herein, inspired by the polar electronic structure feature of CO2 molecule, we propose a strategy whereby the Lewis acid-base dual sites confined in a bimetallic catalyst surface are conducive to forming a M1⋅⋅⋅C=O⋅⋅⋅M2 intermediate precisely, which can promote selectivity to hydrocarbon formation. Employing the Ag2Cu2O3 nanowires with abundant Cu⋅⋅⋅Ag Lewis acid-base dual sites on the preferred exposed {110} surface as a model catalyst, 100 % selectivity toward photoreduction of CO2 into CH4 has been achieved. Subsequent surface-quenching experiments and density functional theory (DFT) calculations verify that the Cu⋅⋅⋅Ag Lewis acid-base dual sites do play a vital role in regulating the M1⋅⋅⋅C=O⋅⋅⋅M2 intermediate formation that is considered to be prone to convert CO2 into hydrocarbons. This study reports a highly selective CO2 photocatalyst, which was designed on the basis of a newly proposed theory for precise regulation of reaction intermediates. Our findings will stimulate further research on dual-site catalyst design for CO2 reduction to hydrocarbons. 相似文献
38.
Shuaishuai Hu Chenfan Xie Yu-Ping Xu Xuelu Chen Dr. Ming-Liang Gao He Wang Prof. Dr. Weijie Yang Prof. Dr. Zhong-Ning Xu Prof. Dr. Guo-Cong Guo Prof. Dr. Hai-Long Jiang 《Angewandte Chemie (International ed. in English)》2023,62(48):e202311625
The selectivity control of Pd nanoparticles (NPs) in the direct CO esterification with methyl nitrite toward dimethyl oxalate (DMO) or dimethyl carbonate (DMC) remains a grand challenge. Herein, Pd NPs are incorporated into isoreticular metal–organic frameworks (MOFs), namely UiO-66-X (X=-H, -NO2, -NH2), affording Pd@UiO-66-X, which unexpectedly exhibit high selectivity (up to 99 %) to DMC and regulated activity in the direct CO esterification. In sharp contrast, the Pd NPs supported on the MOF, yielding Pd/UiO-66, displays high selectivity (89 %) to DMO as always reported with Pd NPs. Both experimental and DFT calculation results prove that the Pd location relative to UiO-66 gives rise to discriminated microenvironment of different amounts of interface between Zr-oxo clusters and Pd NPs in Pd@UiO-66 and Pd/UiO-66, resulting in their distinctly different selectivity. This is an unprecedented finding on the production of DMC by Pd NPs, which was previously achieved by Pd(II) only, in the direct CO esterification. 相似文献
39.
Dr. Miaomiao Tong Dr. Fanfei Sun Dr. Gengyu Xing Prof. Chungui Tian Lei Wang Prof. Honggang Fu 《Angewandte Chemie (International ed. in English)》2023,62(52):e202314933
Single atom sites (SAS) often undergo structural recombination in oxygen reduction reaction (ORR), while the effect of valence state and reconstruction on active centers needs to be investigated thoroughly. Herein, the Mn-SAS catalyst with uniform and precise Mn-N4 configuration is rationally designed. We utilize operando synchrotron radiation to track the dynamic evolution of active centers during ORR. Under the applied potential, the structural evolution of Mn-N4 into Mn-N3C and further into Mn-N2C2 configurations is clarified. Simultaneously, the valence states of Mn are increased from +3.0 to +3.8 and then decreased to +3.2. When the potential is removed, the catalyst returned to its initial Mn+3.0-N4 configuration. Such successive evolutions optimize the electronic and geometric structures of active centers as evidenced by theory calculations. The evolved Mn+3.8-N3C and Mn+3.2-N2C2 configurations respectively adjust the O2 adsorption and reduce the energy barrier of rate-determining step. Thus, it can achieve an onset potential of 0.99 V, superior stability over 10,000 cycles, and a high turnover frequency of 1.59 s−1 at 0.85 VRHE. Our present work provides new insights into the construction of well-defined SAS catalysts by regulating the valence states and configurations of active centers. 相似文献
40.
Steven G. Young;James Valdez;Michelle Espy;Alex Edgar;Jack Brett;Michael T. Pettes;Clay Mathers;Matthew Barbour;Brian M. Patterson; 《X射线光谱测定》2024,53(1):2-15
Two historic-period metal artifacts were provided by the New Mexico Historic Sites to Los Alamos National Laboratory for non-destructive analysis. The artifacts were a crossbow quarrel (or bolthead) and a reliquary pendant recovered from Kuaua Pueblo (also known as the Coronado Historic Site) in Bernalillo, NM. The quarrel is a heavily patinated metal that had been flattened due to compressive forces. The pendant consisted of a metal casing that had previously surrounded two center gemstones on the front and rear face of the pendant. The gemstone in the rear setting had fractured and was displaced from the setting, leaving only a small, loose fragment within the pendant for study. The front gem appeared to be very dark, near-black in color, and the fragment of the rear gem was a bright red color. The artifacts were analyzed to ascertain their composition and glean insight into their provenance using the following X-ray techniques: X-ray computed tomography, confocal micro X-ray fluorescence, and X-ray diffraction. Infrared spectroscopy and electron microscopy were used on selected areas. Ultraviolet Raman spectra were collected on the two gems and the pendant. The metal material of the artifacts was found to be primarily composed of copper. The gems in the pendant were composed of manganese (front gem) and calcium (side gem). 相似文献