单层MXene纳米片Ti2N电磁特性的过渡金属(Sc、V、Zr)掺杂效应

二维材料MXene纳米片由于具有较大的比表面积和较高的电子迁移率而受到广泛的关注。本文采用基于密度泛函理论的第一性原理计算,对单层MXene纳米片Ti₂N电磁特性的过渡金属(Sc、V、Zr)掺杂效应进行了系统研究。结果表明,所有过渡金属掺杂体系结合能均为负值,结构均稳定;其中Ti₂N-Sc体系的形成能为-2.242 eV,结构更易形成,且保持稳定;掺杂后Ti₂N-Sc、Ti₂N-Zr体系磁矩增大;此外,Ti₂N-Sc体系中保留了较高的自旋极化率,达到84.9%,可预测该体系在自旋电子学中具有潜在的应用价值。     

新型Cd(Ⅱ)-MOF的合成及对4-硝基苯胺的高效识别

采用新型1,3,5-三(1H-苯并[d]咪唑-2-基)苯(TBB)配体及2,5-二羟基对苯二甲酸(H₂dhtp)线性配体, 以Cd(Ⅱ)离子为中心节点, 构筑了具有新型拓扑结构(unj)的手性金属-有机框架材料[Cd(TBB)(dhtp) ](配合物1). 该配合物具有较强的光致发光性能, 可分散在溶液中荧光检测硝基配合物等污染物. 其中, 4-硝基苯胺对配合物1具有高效的荧光猝灭能力, 检测限可低至0.145 mg/L, 并具有较好的选择性.     

A zinc(Ⅱ) MOF based on secondary building units of infinite wavy-shaped chain exhibiting obvious luminescent sense effects

A new metal-organic framework (MOF),{[Zn_7 (BPS)_4 (OH)_6 (H_2O)_2]·5 H_2O]_n}(1), (H_2 BPS=4,4′-bibenzoic acid-2,2′-sulfone), based on a wavy and infinite chain-shaped secondary building units, has been synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction and further confirmed by PXRD, TGA and IR spectrum. The solid-state emission spectra reveal that compound 1 presents strong luminescence emission bands at room temperature. The fluorescent properties of compound 1 in diverse organic solvents indicated that 1 has palpable luminescent sense effects for DMF and DMAC.     

The application of metal-organic frameworks in electrocatalytic nitrogen reduction

In recent years, the research of nitrogen reduction reaction (NRR) under ambient conditions has attracted wide attention for their relatively low energy consumption, in which rational design of electrocatalysts is the key to achieve high-performance NRR. Metal-organic frameworks (MOFs), as a new kind of porous material, have been intensively studied in the past few decades owing to not only their structural versatility and tunability but also intrinsic porosity. Due to their structural features, MOFs also have potential applications in mild condition electrocatalysis of NRR. In this review, the recently experimental and theoretical studies of MOFs in NRR electrocatalysts are briefly summarized.     

Nanostructured BiVO4 Derived from Bi-MOF for Enhanced Visible-light Photodegradation

BiVO4,a promising visible-light responding photocatalyst,has aroused extensive research interest because of inexpensiveness and excellent chemical stability.However,its main drawback is the poor photoinduced charge-transfer dynamics.Building nanostructures is an effective way to tackle this problem.Herein,we put forward a new method to prepare nanostructured BiVO4 from Bi-based metal-organic frameworks[Bi-MOF(CAU-17)]precursor.The as-prepared material has a rod-like morphology inherited from the Bi-MOF sacrificial template and consists of small nanoparticle as building blocks.Compared with its counterparts prepared by conventional methods,MOF-derived nanostructured BiVO4 shows better light absorption ability,narrower bandgap,and improved electrical conductivity as well as reduced recombination.Consequently,BiVO4 nanostructure demonstrates high photocatalytic activity under visible light towards the degradation of methylene blue.Methylene blue can be degraded up to 90%within 30 min with a reaction rate constant of 0.058 min-1.Moreover,the cycling stability of the catalyst is excellent to withstand unchanged degradation efficiency for at least 5 cycles.     

MOFs基材料在光催化CO2还原中的应用

系统总结了金属有机框架(MOFs)基材料在光催化还原CO₂中的最新研究进展, 其中包括MOFs直接作为光催化剂和作为复合光催化2个主要部分, 讨论了MOFs基光催化剂在催化还原CO₂方面展现出的独特优势, 并对MOFs基光催化剂的结构稳定性与CO₂转化效率等问题进行讨论与分析, 对未来发展趋势进行了展望.     

Co(Ⅱ)-Zn(Ⅱ)掺杂配位聚合物的 合成及物理性能

采用均苯三甲酸配体、 硝酸锌与硝酸钴反应, 一步合成了钴掺杂的锌配位聚合物Zn_1-xCo_x(BTC)·(OH)(H₂O)₃(NMP)(DMF)(H₂O)_1.5(H₃BTC为1,3,5-均苯三酸, NMP为1-甲基-2-吡咯烷酮, DMF为N,N'-二甲基甲酰胺, x=0~0.8). 该化合物结构经X射线单晶衍射确定, 属于立方晶系, 空间群P2₁3, 晶胞参数a=1.43863(20) nm. 利用元素分析、 能量散色光谱(EDS)、 UV-Vis光谱、 X射线粉末衍射(XRD)、 热重分析(TGA)、 氮气吸附和磁性分析等表征手段对样品的物理性质进行了表征. 氮气吸附实验结果表明, 该配位聚合物具有良好的微孔吸附特性, Langmiur比面积为832 m ²/g, 孔径为0.84 nm; 元素分析结果表明, 钴/锌摩尔比为1∶1时, 在37~300 K温度范围内其磁性表现为反铁磁性, 并满足Curie-Weiss定律.     

TiO2/CNTs复合材料涂覆隔膜的制备及在锂硫电池中的应用

以金属有机框架材料MIL-125(Ti)为模板制备了多孔TiO₂, 同时引入碳纳米管, 得到碳纳米管交联包覆多孔TiO₂的三维导电复合材料. 将该复合材料涂覆在隔膜表面并应用于锂硫电池. 利用透射电子显微镜(TEM)、 扫描电子显微镜(SEM)和X射线光电子能谱仪(XPS)等对材料的结构和组成进行了表征. 电化学测试结果表明,在0.5C(1C=1675 mA/g)倍率下, CNTs/S复合正极材料表现出高达1051.1 mA·h/g的放电容量, 循环150周后仍可保持在904.8 mA·h/g. 在1C倍率下, 放电容量最高可达1036.9 mA·h/g, 循环250周后仍有763.0 mA·h/g, 展现出了良好的倍率性能和循环稳定性.     

Ultrathin Mn Doped Ni-MOF Nanosheet Array for Highly Capacitive and Stable Asymmetric Supercapacitor

In this study, we demonstrate that an Mn-doped ultrathin Ni-MOF nanosheet array on nickel foam (Mn_0.1-Ni-MOF/NF) serves as a highly capacitive and stable supercapacitor positive electrode. The Mn_0.1-Ni-MOF/NF shows an areal capacity of 6.48 C cm⁻² (specific capacity C: 1178 C g⁻¹) at 2 mA cm⁻² in 6.0 m KOH, outperforming most reported MOF-based materials. More importantly, it possesses excellent cycle stability to maintain 80.6 % capacity after 5000 cycles. An asymmetric supercapacitor device utilizing Mn_0.1-Ni-MOF/NF as the positive electrode and activated carbon as the negative electrode attains a high energy density of 39.6 Wh kg⁻¹ at 143.8 Wkg⁻¹ power density with a capacitance retention of 83.6 % after 5000 cycles.     

基于NiCo2O4纳米片电极的非对称混合电容器

The looming global energy crisis and ever-increasing energy demands have catalyzed the development of renewable energy storage systems. In this regard, supercapacitors (SCs) have attracted widespread attention because of their advantageous attributes such as high power density, excellent cycle stability, and environmental friendliness. However, SCs exhibit low energy density and it is important to optimize electrode materials to improve the overall performance of these devices. Among the various electrode materials available, spinel nickel cobaltate (NiCo₂O₄) is particularly interesting because of its excellent theoretical capacitance. Based on the understanding that the performances of the electrode materials strongly depend on their morphologies and structures, in this study, we successfully synthesized NiCo₂O₄ nanosheets on Ni foam via a simple hydrothermal route followed by calcination. The structures and morphologies of the as-synthesized products were characterized by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller (BET) surface area analysis, and the results showed that they were uniformly distributed on the Ni foam support. The surface chemical states of the elements in the samples were identified by X-ray photoelectron spectroscopy. The as-synthesized NiCo₂O₄ products were then tested as cathode materials for supercapacitors in a traditional three-electrode system. The electrochemical performances of the NiCo₂O₄ electrode materials were studied and the area capacitance was found to be 1.26 C·cm^-2 at a current density of 1 mA·cm^-2. Furthermore, outstanding cycling stability with 97.6% retention of the initial discharge capacitance after 10000 cycles and excellent rate performance (67.5% capacitance retention with the current density from 1 to 14 mA·cm^-2) were achieved. It was found that the Ni foam supporting the NiCo₂O₄ nanosheets increased the conductivity of the electrode materials. However, it is worth noting that the contribution of nickel foam to the areal capacitance of the electrode materials was almost zero during the charge and discharge processes. To further investigate the practical application of the as-synthesized NiCo₂O₄ nanosheets-based electrode, a device was assembled with the as-prepared samples as the positive electrode and active carbon (AC) as the negative electrode. The assembled supercapacitor showed energy densities of 0.14 and 0.09 Wh·cm^-3 at 1.56 and 4.5 W·cm^-3, respectively. Furthermore, it was able to maintain 95% of its initial specific capacitance after 10000 cycles. The excellent electrochemical performance of the NiCo₂O₄ nanosheets could be ascribed to their unique spatial structure composed of interconnected ultrathin nanosheets, which facilitated electron transportation and ion penetration, suggesting their potential applications as electrode materials for high performance supercapacitors. The present synthetic route can be extended to other ternary transition metal oxides/sulfides for future energy storage devices and systems.