Surface-effect on detection ability of fluorescent Eu(btc) metal-organic frameworks to metal ions

Eu(btc)metal organic frameworks(MOFs)were prepared by co-precipitation method via 1,2,4-benzenetricarboxylic acids(H3btc)connecting with Eu³⁺ions,and the morphology was controlled from compact spherical to irregular honeycomb by adjusting the pH of reaction solutions.The luminescence properties of Eu(btc)MOFs are found to be related to the surface morphology of products,and the compact spherical one performs stronger emission intensity.The sensing ability of Eu(btc)MOFs to 11 kinds of metal ions was investigated and a prominent quenching effect occurrs in Fe³⁺,or Ni²⁺solutions.Based on UV—vis absorption analysis,an“ion-fence”model presents the competition to absorb exciting light between Eu(btc)MOFs and adsorbed metal ions.Based on Stern-Volmer equation,the Eu(btc)detection is found with higher Ksv value and a lower detection limit.Meanwhile,a higher sensing efficiency is confirmed in the Eu(btc)MOFs with loose honeycomb due to aggravating porous surface offering much more sites for metal ions.     

微结构掺镱双包层光纤的研究

近年来掺健光纤激光器的研究有了较大发展,出现了用于高功率光纤激光器的双包层掺镱光纤(DCYDF)。双包层掺镱光纤的纤芯作为单模波导用于传输信号光。．内包层设计为多模波导用于传输泵浦光。由于微结构光纤具有可控的周期性折射率并且其模场面积可通过结构参数的调整而加以控制．因此这类光纤在光纤激光器和放大器中有着广泛的应用前景。文章作者根据高功率光纤激光器的性能要求．设计和制备了内包层为D形和六边形的微结构掺镱双包层光纤。     

An object-oriented operation-based approach to translation between MOF metaschemas

This paper proposes a new approach to the schema translation problem. We deal with schemas whose metaschemas are instances of the OMG’s MOF. Most metaschemas can be defined as an instance of the MOF; therefore, our approach is widely applicable. We leverage the well-known object-oriented concepts embedded in the MOF and its instances (object types, attributes, relationship types, operations, IsA hierarchies, refinements, invariants, pre- and postconditions, etc.) to define metaschemas, schemas and their translations.The main contribution of our approach is the extensive use of object-oriented concepts in the definition of translation mappings, particularly the use of operations (and their refinements) and invariants, both of which are formalized in OCL. Our translation mappings can be used to check that two schemas are translations of each other, and to translate one into the other, in both directions. The translation mappings are declaratively defined by means of pre- and postconditions and invariants, and they can be implemented in any suitable language. From an implementation point of view, by taking a MOF-based approach we have a wide set of tools available, including tools that execute OCL. By way of example, we have defined all schemas and metaschemas in this paper and executed all the OCL expressions in the USE tool.     

钴氮共掺杂碳基电催化剂的制备及性能调控

贵金属基电催化剂是促进燃料电池及金属-空气电池技术发展的关键材料,然而,其单一的氧还原/氧析出催化功能及高昂的制备成本制约了其推广应用。为此,开发低成本、高效的非贵金属双功能电催化剂至关重要。以核壳金属有机框架（MOFs）为前驱体,通过高温煅烧法制备具有核壳结构、高催化活性、高导电性的钴/氮共掺杂碳基电催化剂（Co/Co₃O₄@NGC）。结果表明：煅烧温度是影响电催化剂微纳结构、物化组成和催化活性的关键因素,最佳烧结温度为900℃;制备的电催化剂（Co/Co₃O₄@NGC-900）具有清晰的核壳结构和3D十二面体形貌,微表面遍布Co/Co₃O₄纳米颗粒和Co-N_x位点。同时,Co/Co₃O₄@NGC-900有机地结合了多元活性成分（如活性Co/Co₃O₄纳米颗粒、Co-N_x及N掺杂）和高度石墨化碳基底的共同作用,具备高效的氧还...     

MOFs in photoelectrochemical water splitting: New horizons and challenges

Growing energy consumption with the augmentation in universal population to more than nine billion by 2050 and exhausting fossil fuel reserves necessitates a harsh revolution from non-renewable energy reservoirs to renewable energy reservoirs with zero carbon emission. In the present scenario, solar energy prompted photoelectrochemical (PEC) water splitting or “Artificial Photosynthesis” via light gripping semiconductor material, originates out as the most promising methodology in accomplishing the global energy crisis. Recent studies have amply demonstrated the potential of metal-organic frameworks (MOF) towards PEC applications. They are porous crystalline coordination polymers assembled through an appropriate choice of metal ions and multidentate organic ligands. Owing to their structural regularity and synthetic tunability, MOFs integration with PEC is considered in terms of enhancing and broadening light absorption, providing active sites and directing charge transfer dynamics. Here, we have explored MOFs role in PEC and classified them into different categories such as photosensitizers, co-catalysts, counter electrode, template and also for imparting additional stability to the electrode system. MOFs mediated PEC water splitting is promising but is still rare and in its infancy. Therefore, it is pertinent and timely to take stock of the advancements made and develop insight on the use of MOFs, as an emerging solution for the problems encountered in PEC. This review covers the basics of MOF & mainly describes various case studies done during last 10 years and providing adequate impetus to researchers for critically assessing the recent advances and challenges that are faced by scientists and researchers at large.     

MOF衍生碳包覆硅纳米颗粒限制于石墨烯复合负极材料的制备及性能研究

采用原位生长法设计并合成了MOF衍生碳包覆硅纳米颗粒限制于石墨烯的复合材料(Si/C@G),并应用于锂离子电池负极材料,该材料结构有效缓解硅基负极材料充放电过程的体积变化,促进了稳定的固态电解质中间相层的形成,提高了电极材料的电导率。Si/C@G负极材料在电流密度500 mA/g时经100次循环可逆比容量仍有1081.2 mAh/g;在电流密度5.0 A/g时其可逆容量达到949.6 mAh/g。Si/C@G负极在1.0 A/g的恒电流密度下循环500次后可逆比容量可保持在677.2 mAh/g左右,库仑效率可达99.84%,表现出良好的循环稳定性。     

FTTH用微结构光纤

文章描述了国外光纤到户(FTTH)用微结构光纤(MOF)的种类及其应用情况,并从弯曲损耗、衰减、熔接损耗以及寿命4个方面阐述了微结构弯曲不敏感光纤的性能.分析表明,微结构弯曲不敏感光纤适合于空间狭小、弯曲直径较小与弯曲点较多的情况下的灵活安装,可满足FTTH光网络发展的需要.     

MIL-53 and its Isoreticular Analogues: a Review of the Chemistry and Structure of a Prototypical Flexible Metal-Organic Framework

We present a review of the structural chemistry of metal-organic framework materials with the MIL-53 type structure. This family of materials is well-known for its structural flexibility, and also the wide variety of metal cations and functional ligands that can be included. This gives rise to a set of multivariate materials and isoreticular analogues, to which isoreticular functionalisation can also be applied. Starting from the parent structure, containing infinite chains of octahedral trivalent metal cations cross-linked by benzene-1,4-dicarboxylate, we illustrate the compositional variety possible: this includes materials that contain tetravalent and divalent cations, mixtures of metal cations, functionalised ligands, expanded structures from extended linkers and inclusion of pendant ligands. We emphasise the crystal chemistry of this group of materials, but will give some examples of properties, particularly those associated with the structural breathing effect of relevance to molecular sieving, and also discuss emerging practical applications.     

Study on the performance of Cd2+ sorption using dimethylethylenediamine-modified zinc-based MOF (ZIF-8-mmen): optimization of the process by RSM technique

ABSTRACT

Cadmium as a highly toxic metal is released into the environment through paper production, metal processing, phosphate fertilizers, insecticides, and treatment of wastewater. Cadmium also inhibits the body activities and is very toxic for kidney and other organisms. In the current study, zinc-based metal–organic framework, zeolitic imidazolate framework (ZIF)-8, was synthesized and modified by dimethylethylenediamine (ZIF-8-mmen) for the removal of cadmium. To optimize the experiments, response surface methodology was applied with three variables including pH, adsorbent dosage, and contact time using central composite design. The optimum conditions for pH, dosage, and time were 2, 0.1 g, and 89 min, respectively, with removal efficiency of 85.38%. The Langmuir isotherm (q _m = 1000 mg/g) indicates the monolayer adsorption. The kinetic studies reveal that the Lagergren model was predominant and cadmium was not chemisorbed. Thermodynamic parameters show spontaneous, endothermic, and physisorption processes.     

Design and self-assembly of metal-organic framework-derived porous Co3O4 hierarchical structures for lithium-ion batteries

Porous metal oxides hierarchical structures with controlled morphologies have received great attention because of their promising applications in catalysis, energy storage, gas sensing, etc. Porous Co₃O₄ hierarchical structures with controlled morphologies were synthesized on the basis of a pyrolytic conversion of Co-based metal-organic frameworks (Co-MOFs), which were initially grown in solutions containing Co(NO₃)₂·6H₂O, 1,3,5-Benzentricarboxylic acid and pyrazine as solute and N,N-dimethylformamide (DMF) as solvent under a solvothermal condition. Porous Co₃O₄ with twin hemispherical and flower-like structures were obtained with the assistance of PVP by adjusting the amount of pyrazine. The results of nitrogen adsorption–desorption indicate the BET surface area (22.6 m² g⁻¹) of twin hemispherical Co₃O₄ structures is lower than that (33.3 m² g⁻¹) of flower-like Co₃O₄ structures. However, the pore size of twin hemispherical Co₃O₄ structures is smaller, which is centered at about 2.5, 4.0 and 20.0 nm. The Co₃O₄ with twin hemispherical structures exhibit more excellent electrochemical performance as anode materials for lithium ion batteries than that of flower-like Co₃O₄ structures, which may be attributed to the smaller particle size and compact porous structures with suitable pore size.