压强对Zr_(67)Ni_(33)非晶合金结构和动力学性能的影响

采用分子动力学的方法模拟Zr_(67)Ni_(33)合金液体在不同压强下快速凝固过程,通过结构分析方法如对分布函数、配位数、Honeycutt-Andersen(HA)键型指数法,以及动力学参数如均方位移、自散射关联函数、非高斯参数研究压强对Zr_(67)Ni_(33)非晶合金局域原子结构和其过冷液体动力学性能的影响.研究结果表明:压强越大,Zr_(67)Ni_(33)非晶合金中Zr-Ni原子间的相互作用越强,体系结构有序性越强,过冷液体中动力学减慢和动力学不均匀现象越显著.     

Growth of ZIF-8 MOF Films with Tunable Porosity by using Poly (1-vinylimidazole) Brushes as 3D Primers

This work reports on a novel and versatile approach to control the structure of metal–organic framework (MOFs) films by using polymeric brushes as 3D primers, suitable for triggering heterogeneous MOF nucleation. As a proof-of-concept, this work explores the use of poly(1-vinylimidazole) brushes primer obtained via surface-initiated atom transfer radical polymerization (SI-ATRP) for the synthesis of Zn-based ZIF-8 MOF films. By modifying the grafting density of the brushes, smooth porous films were obtained featuring inherently hydrophobic microporosity arising from ZIF-8 structure, and an additional constructional interparticle mesoporosity, which can be employed for differential adsorption of targeted adsorbates. It was found that the grafting density modulates the constructional porosity of the films obtained; higher grafting densities result in more compact structures, while lower grafting density generates increasingly inhomogeneous films with a higher proportion of interparticle constructional porosity.     

Hydrogen production and photocatalytic activity of g-C3N4/Co-MOF (ZIF-67) nanocomposite under visible light irradiation

Herein, cobalt (Co)-based metal–organic zeolitic imidazole frameworks (ZIF-67) coupled with g-C₃N₄ nanosheets synthesized via a simple microwave irradiation method. SEM, TEM and HR-TEM results showed that ZIF-67 were uniformly dispersed on g-C₃N₄ surfaces and had a rhombic dodecahedron shape. The photocatalytic properties of g-C₃N₄/ZIF-67 nanocomposite were evaluated by photocatalytic dye degradation of crystal violet (CV), 4-chlorophenol (4-CP) and photocatalytic hydrogen (H₂) production. In presence of visible light illumination, the photocatalytic dye results showed that 95% CV degradation and 53% 4-CP degradation within 80 min. The H₂ production of the g-C₃N₄/ZIF-67 composite was 2084 μmol g⁻¹, which is 3.84 folds greater than that of bare g-C₃N₄ (541 μmol g⁻¹).     

N‐Doped Carbon Aerogel Derived from a Metal–Organic Framework Foam as an Efficient Electrocatalyst for Oxygen Reduction

Metal–organic frameworks (MOFs) are promising alternative precursors for the fabrication of heteroatom‐doped carbon materials for energy storage and conversion. However, the direct pyrolysis of bulk MOFs usually gives microporous carbonaceous materials, which significantly hinder the mass transportation and the accessibility of active sites. Herein, N‐doped carbon aerogels with hierarchical micro‐, meso‐, and macropores were fabricated through one‐step pyrolysis of zeolitic imidazolate framework‐8/carboxymethylcellulose composite gel. Owing to the hierarchical porosity, high specific surface area, favorable conductivity, excellent thermal and chemical stability, the as‐prepared N‐doped carbon aerogel exhibits excellent oxygen reduction reaction (ORR) activity, long‐term durability, and good methanol tolerance in alkaline medium. This work thus provides a new way to fabricate new types of MOF‐derived carbon aerogels for various applications.     

Zeolitic imidazolate framework-67 (ZIF-67) rhombic dodecahedrons as full-spectrum light harvesting photocatalyst for environmental remediation

The inferior utilization efficiency of light is the main obstacle to the practical application of traditional photocatalysts such as TiO₂ and ZnO. In this regard, the development of novel photocatalysts with the capability of harvesting full spectrum light (from ultraviolet (UV) to near-infrared (NIR)) energy is a promising solution for solar energy conversion and environmental remediation. Here, we report the discovery of a single material that can harvest UV, visible (VIS), and NIR radiations to decompose heavy metal contaminants in aqueous solution. Zeolitic imidazolate framework-67 (ZIF-67) rhombic dodecahedrons were synthesized through a facile solution approach and employed in the reduction of Cr(VI) under UV−VIS−NIR pulsed laser irradiation, which was generated from the fundamental, second and third harmonics of Nd:YAG laser, respectively. The nanostructures showed efficient Cr(VI) reduction under UV, VIS and NIR laser irradiation and the measured reduction efficiency (%) was 71.22%, 69.52%, and 40.79%, respectively after 120 min. A possible explanation for the photocatalytic activity in Cr(VI) reduction was proposed. This is the first study of its kind where pulsed laser and ZIF-67 rhombic dodecahedrons capable of harvesting full spectrum light energy have been employed for the removal of Cr(VI) from water. The extraordinary capacity of harvesting full-spectrum light and long-term stability make ZIF-67 a potential photocatalyst for environmental remediation.     

ZIF-derived mesoporous carbon materials prepared by activation via Na2SiO3 for supercapacitor

Metal organic frameworks (MOFs) derived carbonaceous materials have a wide range of applications in the fields of energy storage, catalysis, adsorption and separation, etc. Especially, zeolitic imidazolate framework-8 (ZIF-8) is an excellent candidate to synthesize porous carbon due to the large surface area and high nitrogen content. However, the dominated microporous structure of ZIF-8-derived carbon significantly hinders ionic mass transfer, limiting the improvement of performance. Herein, MOF-derived mesoporous carbon was prepared using ZIF-8 as carbon precursor and cheap sodium silicate (Na₂SiO₃) as activator. The introduction of Na₂SiO₃ created rich mesoporous structure and increased specific surface area, as well as the effects of pyrolysis temperature and Na₂SiO₃ dosage on performance was also investigated. The obtained ZIF-derived porous carbon exhibits good electrochemical performance with specific capacitance of 263 F/g at 1 A/g and excellent cycle life (96.07% after 10,000 GCD cycles) in supercapacitor. The use of cheap Na₂SiO₃ activator provides a new orientation for the preparation of MOF-derived carbons with rich pores, high surface area, and facilitates the large-scale application of MOF-derived carbons.     

ZIF-8衍生的具有可控氧空位的ZnO对光催化去除NO的增强及毒性NO2形成的抑制

氧化锌作为一种半导体材料,具有合适的能带结构位置,高催化效率,低成本和环境可持续性,因而广泛用于光催化领域.然而,由于氧化锌的宽带隙,可见光吸收能力差以及光生电子-空穴对的快速复合,极大地影响了其光催化效率.通过引入氧空位调控光催化剂的结构被证明是一种可以改善光生载流子的分离,从而提高光催化性能的有效方法.本文以ZIF-8为前驱体,采用两步煅烧法合成了具有不同浓度氧空位分布的ZnO纳米光催化剂,通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)、X射线光电子能谱(XPS)、电子顺磁共振(EPR)、荧光光谱仪(PL)等手段系统地分析了合成的光催化剂的理化性质,并评价了它们在可见光下光催化氧化去除NO反应性能.EPR结果表明,样品中氧空位的浓度取决于温度处理的过程.通过两步煅烧法得到氧化锌中氧空位的含量高于一步直接煅烧法所得的样品.此外,随着煅烧温度升高,合成的氧化锌晶格越完好,其氧空位含量越少.UV-Vis DRS结果表明,两步煅烧法合成的ZnO与商业的ZnO及一步法直接煅烧合成的ZnO相比,其吸光范围从紫外光拓展到了可见光,表现出了更加优异的吸光性能.光催化反应结果表明,与商业氧化锌和一步直接煅烧法所得样品相比,两步煅烧法合成的样品表现出了更优异的光催化去除NO性能,并抑制了中间产物毒性NO2的产生,促进了NO的深度氧化.具体反应路径为:在光照过程中,光生电子很容易被氧空位俘获,与O2反应产生更多的超氧自由基(·O2^-),从而将NO氧化成最终的产物硝酸盐.尤其有趣的是,先在350 ℃煅烧2小时再400℃煅烧1小时的两步法样品Z 350-400的NO去除效率分别比一步法样品Z 400(400℃煅烧)和商用ZnO高出1.5和4.6倍.这表明以MOF材料衍生的具有适当量氧空位的金属氧化物为一种高效去除NO的光催化剂具有很好的应用前景.     

Au@ZIF-8核壳结构中金纳米粒子分布的调控及其在荧光分子光致发光传感中的应用

控制金属@MOF核壳纳米结构中金属纳米粒子的分布不容易实现。我们应用了合成MOF胶体粒子所用到的配位调制方法来合成Au@ZIF-8核壳纳米结构。通过使用过量的2-甲基咪唑和不同用量的1-甲基咪唑可获得不同的Au@ZIF-8。该合成方法可在ZIF-8纳米晶体中灵活调整Au纳米粒子（Au NPs）的分布。此外,我们分别研究了2种不同尺寸的荧光分子与Au@ZIF-8结合后的光致发光光谱和寿命。ZIF-8的孔径可以决定这2种分子是否可通过多孔壳结构接近Au NPs。分子光学特性对Au NPs近场的发光增强和荧光猝灭的竞争非常敏感。     

ZIF-8材料的制备及应用进展

沸石咪唑酯骨架材料(Zeolitic Imidazolate Framework-8,ZIF-8)是由Zn（Ⅱ）与2-甲基咪唑配位自组装形成的多孔结晶材料,具有可调的孔径、高稳定的结构和催化活性等特点,近年来ZIF-8的制备和应用展现出巨大的潜力并引起了广泛关注。本文总结了目前ZIF-8的制备方法,在此基础上介绍了ZIF-8的形成机理及粒径调控方法,重点综述了ZIF-8及其复合材料在吸附分离、催化、生物医学等领域应用的研究进展,并展望了其应用前景与发展方向,以期为ZIF-8 的应用发展开拓新的思路。     

Design,Synthesis, and Anticancer Screening for Repurposed Pyrazolo[3,4-d]pyrimidine Derivatives on Four Mammalian Cancer Cell Lines

The present study reports the synthesis of new purine bioisosteres comprising a pyrazolo[3,4-d]pyrimidine scaffold linked to mono-, di-, and trimethoxy benzylidene moieties through hydrazine linkages. First, in silico docking experiments of the synthesized compounds against Bax, Bcl-2, Caspase-3, Ki67, p21, and p53 were performed in a trial to rationalize the observed cytotoxic activity for the tested compounds. The anticancer activity of these compounds was evaluated in vitro against Caco-2, A549, HT1080, and Hela cell lines. Results revealed that two (5 and 7) of the three synthesized compounds (5, 6, and 7) showed high cytotoxic activity against all tested cell lines with IC₅₀ values in the micro molar concentration. Our in vitro results show that there is no significant apoptotic effect for the treatment with the experimental compounds on the viability of cells against A549 cells. Ki67 expression was found to decrease significantly following the treatment of cells with the most promising candidate: drug 7. The overall results indicate that these pyrazolopyrimidine derivatives possess anticancer activity at varying doses. The suggested mechanism of action involves the inhibition of the proliferation of cancer cells.