纳米金修饰锌基金属有机框架用于过氧化氢的检测研究

本研究利用溶剂热法制备锌基金属有机框架材料(ZIF-8),再通过电沉积法将金纳米颗粒(Au NPs)负载到ZIF-8上,构建无酶电化学传感器(Au NPs/ZIF-8/GCE)用于过氧化氢(H2 O2)的电化学测定.通过扫描电子显微镜(SEM)和透射电子显微镜(TEM)对修饰材料的形貌进行了表征.实验采用循环伏安法(C...     

Crystal growth of nanoporous metal organic frameworks

Nanoporous metal organic frameworks (MOFs) form one of the newest families of crystalline nanoporous material that is receiving worldwide attention. Successful use of MOFs for application requires not only development of new materials but also a need to control their crystal properties such as size, morphology, and defect concentration. An understanding of the crystal growth processes is necessary in order to aid development of routes to control such properties of the crystallites. In this Perspective article we aim to provide a short overview of the current work and understanding concerning the nucleation and growth processes of nanoporous MOFs and how this work may be expanded upon to further our comprehension of this subject. We also focus heavily on in situ studies that provide real time information on the developing materials and generally provide the most conclusive findings on the processes under investigation.     

Amorphization of the prototypical zeolitic imidazolate framework ZIF-8 by ball-milling

We report the rapid amorphization of the prototypical substituted zeolitic imidazolate framework, ZIF-8, by ball-milling. The resultant amorphous ZIF-8 (a(m)ZIF-8) possesses a continuous random network (CRN) topology with a higher density and a lower porosity than its crystalline counterpart. A decrease in thermal stability upon amorphization is also evident.     

The Henry reaction catalyzed by zeolitic imidazolate framework ZIF-8

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Experimental and molecular simulation studies of CO2 adsorption on zeolitic imidazolate frameworks: ZIF-8 and amine-modified ZIF-8

ZIF-8 has been rapidly developed as a potential candidate for CO₂ capture due to its low density, high surface area, and robust structure. Considering the electron-donating effect of amino functional groups, amino-modification is expected to be an efficient way to improve CO₂ adsorption of ZIF-8. In this work, grand canonical Monte Carlo (GCMC) simulation was performed to study the CO₂ adsorption isotherm based on ZIF-8, ZIF-8-NH₂, and ZIF-8-(NH₂)₂. ZIF-8 was synthesized and CO₂ adsorption isotherms based on ZIF-8 was measured. The experimental surface area, pore volume, and CO₂ adsorption isotherm were used to validate the force field. Adsorptive capacity of ZIF-8-NH₂, and ZIF-8-(NH₂)₂ were first estimated. The GCMC simulation results indicated that the order of increasing CO₂ capacity of the ZIF-8 in the lower pressure regime is: ZIF-8 < ZIF-8-NH₂ < ZIF-8-(NH₂)₂, and in the high pressure is: ZIF-8 < ZIF-8-(NH₂)₂ < ZIF-8-NH₂. New adsorption sites can be generated with the existence of-NH₂ groups. In addition, for non-modified and amino-modified ZIF-8, it was the first time to use density functional theory (DFT) calculations to investigate their CO₂ adsorption sites and CO₂ binding energies. The present work indicates that appropriate amine-functionalized can directly enhanced CO₂ capacity of ZIF-8.     

Opening the gate: framework flexibility in ZIF-8 explored by experiments and simulations

ZIF-8 is a zeolitic imidazole-based metal-organic framework with large cavities interconnected by narrow windows. Because the small size of the windows, it allows in principle for molecular sieving of gases such as H(2) and CH(4). However, the unexpected adsorption of large molecules on ZIF-8 suggests the existence of structural flexibility. ZIF-8 flexibility is explored in this work combining different experimental techniques with molecular simulation. We show that the ZIF-8 structure is modified by gas adsorption uptake in the same way as it is at a very high pressure (i.e., 14,700 bar) due to a swing effect in the imidazolate linkers, giving access to the porosity. Tuning the flexibility, and so the opening of the small windows, has a further impact on the design of advanced molecular sieving membrane materials for gas separation, adjusting the access of fluids to the porous network.     

Oxidation of benzyl alcohol in the copper-doped ZIF-8 metal-organic framework with encapsulated nitroxyl radical

Russian Chemical Bulletin - A novel heterogeneous catalytic system based on the TEMPO nitroxyl radical encapsulated into the cavities of copper-doped ZIF-8 metal-organic framework was synthesized...     

The role of synchrotron radiation in examining the self-assembly of crystalline nanoporous framework materials: from zeolites and aluminophosphates to metal organic hybrids

This tutorial review describes the role of synchrotron-based techniques in the study of the formation of Crystalline Nanoporous Framework Materials (CNFMs), such as zeolites, aluminophosphates (AlPOs) and metal organic frameworks (MOFs). Initially, a general formation process for CNFMs is described and the 'tool kit' (including synchrotron and non-synchrotron-based techniques) used to examine this complex process is presented. The need for realistic in situ conditions and the balance between this, data quality and time resolution, are also discussed with reference to commonly utilized in situ synchrotron-based experimental cells. The experimental studies into the formation of several CNFM systems are then examined and the role of the synchrotron-based experiments, in context with those obtained from other techniques, is discussed. From this the importance of the synchrotron-based technique is demonstrated, however it is also shown that, to obtain a more complete understanding of the formation process, complementary independent measurements are still often required. During these discussions some of the most common experimental techniques and analytical methods are also discussed in detail and critically assessed.     

Adsorption of pyridine onto the metal organic framework MIL-101

The adsorption of pyridine onto the metal organic framework MIL-101 was investigated by experimental and theoretical methods. The amount of pyridine adsorbed on MIL-101 was extraordinarily large at 20 °C, corresponding to about 950 mg/g of dried MIL-101 and approximately half of the voids being filled. Most of the pyridine that had filled the voids was rapidly removed by evacuation at room temperature, but some of the pyridine was so strongly adsorbed that it was retained even under evacuation at 150 °C. Although IR spectra of the adsorbed pyridine indicated the adsorption of pyridine as pyridinium ions and coordinated pyridine at low temperatures, increasing the adsorption temperature induced partial cleavage of the pyridine rings. The high stabilization energy of pyridine on the coordinative unsaturated sites (CUS) of MIL-101, obtained by theoretical calculation, -103 kJ/mol, supported the strong adsorption of pyridine on the CUS.     

CdS-modified ZIF-8-derived porous carbon for organic pollutant degradations under visible-light irradiation

Research on Chemical Intermediates - A series of CdS-modified zeolitic imidazolate framework-8 (ZIF-8)-derived porous carbons (marked as CZCs) were fabricated via a facile method in the study. And,...     

Tuning luminescent properties of a metal organic framework by insertion of metal complexes

Abstract

We report the preparation and characterisation of new emissive materials based on the insertion of platinum(II) and iridium(III) complexes inside the Al(OH)(bipyridine dicarboxylate) metal organic framework (MOF-253). Guest incorporation is performed by coordination of a metal complex precursor, and provides increased robustness to the system compared to guest inclusion by its physical diffusion. Powder X-ray diffraction analysis highlights the high degree of crystallinity of the materials, with a complete change in the lattice parameters upon metal complex insertion. The photophysical properties of the resulting materials were thoroughly investigated. This synthetic approach is particularly attractive since, as we show, it is possible to tune the emission maxima of our materials over the entire visible range.     

Layer-by-layer assembly of polyelectrolyte chains and nanoparticles on nanoporous substrates: molecular dynamics simulations

We performed molecular dynamics simulations of a multilayered assembly of oppositely charged polyelectrolyte chains and nanoparticles on porous substrates with cylindrical pores. The film was constructed by the sequential adsorption of oppositely charged species in a layer-by-layer fashion from dilute solutions. The multilayer assembly proceeds through surface overcharging after the completion of each deposition step. The substrate overcharging fraction fluctuates around 0.5 for nanoparticle-polyelectrolyte systems and around 0.4 for polyelectrolyte-polyelectrolyte systems. The surface coverage increases linearly with the number of deposition steps. The rate of surface coverage increases as a function of the number of deposition step changes when the pore is blocked. The closing of the pore occurs from the pore entrance for nanoparticle-polyelectrolyte systems. In the case of polyelectrolyte-polyelectrolyte systems, the pore plug is formed inside the pore and then spreads toward the pore ends.     

Fabrication of ZiF-8 metal organic framework (MOFs)-based CuO-ZnO photocatalyst with enhanced solar-light-driven property for degradation of organic dyes

In this research, novel CuO-ZnO/ZiF-8 metal–organic frameworks (MOFs) photocatalyst with different mass percentages of ZiF-8 were prepared for water purification applications under visible light. The precipitation method was used to synthesize CuO-ZnO/ZiF-8 photocatalysts. Some techniques, including XRD, FESEM, EDX, BET-BJH, FTIR, DRS, and pH_pzc, were performed to determine the structural, chemical, and optical properties of the prepared samples. DRS analysis represented that CuO-ZnO/ZiF-8(20) had narrower band gap energy compared to CuO-ZnO and ZiF-8. Also, BET-BJH analysis results showed that CuO-ZnO had a low surface area that impeded the absorption of pollutant molecules. In contrast, the CuO-ZnO/ZiF-8(20) sample, due to the presence of ZiF-8, had a high specific surface area which enabled higher pollutant adsorption on the photocatalyst surface.Moreover, the synthesized samples were evaluated for the solar-light-driven removal of different organic dyes, such as Acid Orange 7, Methylene blue, and Malachite green. The tremendously enhanced photocatalytic activity under the simulated solar light with 98.1% removal of AO7 was observed over CuO-ZnO/ZiF-8(20) sample. Then, the effect of initial solution pH as an essential factor on photocatalytic activity was investigated. Finally, the reaction mechanism of AO7 degradation over CuO-ZnO/ZiF-8(20) was proposed.     

Tuning the Adsorption Selectivity of ZIF-8 by Amorphization

Amorphous metal–organic frameworks (a_mMOFs) with a partially collapsed structure are a new category of porous hybrid materials. Here, solid-state amorphization of ZIF-8 was achieved by mechanical compression at 0.75 GPa. The compression-induced amorphous ZIF-8 (a_mZIF-8) had a collapsed structure, but retained partial porosity. Benefiting from the deformed channel, the resultant a_mZIF-8 exhibited preferable adsorption of C₃H₆, resulting in higher thermodynamic adsorption selectivity of C₃H₆/C₃H₈ (6.72) than the crystalline counterparts (1.06). Further, a_mZIF-8 achieved complete separation of an equimolar C₃H₆/C₃H₈ mixture with the first breakthrough of C₃H₈. a_mZIF-8 also displayed an enhancement in CO₂/N₂ and CO₂/CH₄ adsorption selectivities. More importantly, a self-standing a_mZIF-8 membrane with boundary-free microstructure was constructed for the first time, and exhibited separation potential for H₂/CH₄, CO₂/N₂, CO₂/CH₄, and C₃H₆/C₃H₈ with ideal selectivities of 14.79, 12.83, 16.23, and 2.67, respectively.     

Synthesis, characterization, and application of metal organic framework nanostructures

The considerable number of important physical properties, including optical, electronic, and magnetic properties, of Prussian blue (PB) analogues have attracted fundamental and industrial interest. Nevertheless, the gas sorption properties of PB coordination compounds were only investigated very recently. In this work, we report the synthesis and gas sorption properties of PB nanocomposites with different size and shape obtained by using poly(vinylpyrrolidone) (PVP), chitosan, and dioctyl sodium sulfosuccinate (AOT) as stabilizers and structure directing agents. All three porous nanocrystals show high and selective CO(2) adsorption over CH(4) or N(2). No distinct relationship was found between the size (or shape) of the nanosorbents and their gas uptake capacities. To our knowledge, this is the first report on the use of PB nanocomposites for CO(2) capture applications.     

金属有机骨架材料MOF-5吸附苯并噻吩性能

苯并噻吩类硫化物的脱除是燃油实现深度脱硫的关键。实验研究了典型的金属有机骨架材料MOF-5吸附苯并噻吩性能。结果表明,MOF-5对模型油中苯并噻吩的吸附动力学过程满足拟二级动力学模型。Langmuir、Freundlich和Dubinin-Radushkevich (D-R) 三种等温吸附模型均可较好地描述MOF-5对苯并噻吩的等温吸附行为 (Freundlich>D-R>Langmuir)。热力学参数表明,MOF-5对苯并噻吩的吸附是自发的吸热吸附过程。     

On the performance of Cu-BTC metal organic framework for carbon tetrachloride gas removal

The performance of Cu-BTC metal organic framework for carbon tetrachloride removal from air has been studied using molecular simulations. According to our results, this material shows extremely high adsorption selectivity in favour of carbon tetrachloride. We demonstrate that this selectivity can be further enhanced by selective blockage of the framework.     

Hollow Co9S8 from metal organic framework supported on rGO as electrode material for highly stable supercapacitors

We demonstrate a hydrothermal method to fabricate a composite of reduced graphene oxide (rGO) with hollow Co₉S₈ derived from metal organic framework (MOF), which exhibits a high specific capacitance of 575.9 F/g at 2 A/g and 92.0% capacitance retention after 9000 cycles.     

Novel conjugated nanoporous alkynyl metalloporphyrin framework as effective catalyst for oxidation of toluene with molecular oxygen

A porous alkynylporphyrin conjugated organic polymer (MnE‐TPP) was synthesized by Sonogashira coupling reaction with Mn(II) 5,10,15,20‐tetrakis(4′‐ethynylphenyl)porphyrin and Mn(II) 5,10,15,20‐tetrakis(4′‐bromophenyl)porphyrin as building blocks. The polymer was characterized using nitrogen adsorption–desorption isotherms, field‐emission scanning electron microscopy, high‐resolution transmission electron microscopy, Fourier transform infrared and UV–visible spectroscopies, X‐ray diffraction, thermogravimetry and inductively coupled plasma atomic emission spectrometry. The electrochemical behaviors of MnE‐TPP were investigated by cyclic voltammetry. MnE‐TPP was developed as a heterogeneous catalyst for the activation of molecular oxygen to oxidize toluene under mild conditions. The selectivity of total benzaldehyde and benzyl alcohol remained above 70.0% with a conversion of toluene up to 10.2%. The turnover number was as high as 13 653. Also, MnE‐TPP remained structurally stable and the toluene conversion rate hardly decreased after 5 h of reaction and five cycles of reuse.