(110)‐Oriented ZIF‐8 Thin Films on ITO with Controllable Thickness

(110)‐oriented zeolitic imidazolate framework (ZIF)‐8 thin films with controllable thickness are successfully deposited on indium tin oxide (ITO) electrodes at room temperature. The method applied uses 3‐aminopropyltriethoxysilane (APTES) in the form of self‐assembled monolayers (SAMs), followed by a subsequent adoption of the layer‐by‐layer (LBL) method. The crystallographic preferential orientation (CPO) index shows that the ZIF‐8 thin films are (110)‐oriented. A possible mechanism for the growth of the (110)‐oriented ZIF‐8 thin films on 3‐aminopropyltriethoxysilane modified ITO is proposed. The observed cross‐sectional scanning electron microscopy (SEM) images and photoluminescent (PL) spectra of the ZIF‐8 thin films indicate that the thickness of the ZIF‐8 layers is proportional to the number of growth cycles. The extension of such a SAM method for the fabrication of ZIF‐8 thin films as described herein should be applicable in other ZIF materials, and the as‐prepared ZIF‐8 thin films on ITO may be explored for photoelectrochemical applications.     

Controlling Dissolution and Transformation of Zeolitic Imidazolate Frameworks by using Electron‐Beam‐Induced Amorphization

Amorphous zeolitic imidazolate frameworks (ZIFs) offer promising applications as novel functional materials. Herein, amorphization of ZIF‐L through scanning‐electron‐beam exposure is demonstrated, based on amorphization of individual ZIF‐L crystals. The amorphized ZIF product has drastically increased stability against dissolution in water. An electron dose that allows for complete preservation of amorphous particles after immersion in water is established, resulting in new shapes of amorphous ZIF‐L with spatial control at the sub‐micrometer length scale. Changed water stability as a consequence of scanning‐electron‐beam exposure is demonstrated for three additional metal–organic frameworks (ZIF‐8, Zn(BeIm)OAc, MIL‐101), highlighting the potential use of an electron beam for top‐down MOF patterning. Lastly, recrystallization of ZIF‐L in the presence of linker is studied and shows distinct differences for crystalline and amorphized material.     

Hollow Zn/Co Zeolitic Imidazolate Framework (ZIF) and Yolk–Shell Metal@Zn/Co ZIF Nanostructures

Metal–organic frameworks (MOFs) feature a great possibility for a broad spectrum of applications. Hollow MOF structures with tunable porosity and multifunctionality at the nanoscale with beneficial properties are desired as hosts for catalytically active species. Herein, we demonstrate the formation of well‐defined hollow Zn/Co‐based zeolitic imidazolate frameworks (ZIFs) by use of epitaxial growth of Zn‐MOF (ZIF‐8) on preformed Co‐MOF (ZIF‐67) nanocrystals that involve in situ self‐sacrifice/excavation of the Co‐MOF. Moreover, any type of metal nanoparticles can be accommodated in Zn/Co‐ZIF shells to generate yolk–shell metal@ZIF structures. Transmission electron microscopy and tomography studies revealed the inclusion of these nanoparticles within hollow Zn/Co‐ZIF with dominance of the Zn‐MOF as shell. Our findings lead to a generalization of such hollow systems that are working effectively to other types of ZIFs.     

Catalytically Active Hollow Fiber Membranes with Enzyme‐Embedded Metal–Organic Framework Coating

Metal–organic frameworks (MOFs) are suitable enzyme immobilization matrices. Reported here is the in situ biomineralization of glucose oxidase (GOD) into MOF crystals (ZIF‐8) by interfacial crystallization. This method is effective for the selective coating of porous polyethersulfone microfiltration hollow fibers on the shell side in a straightforward one‐step process. MOF layers with a thickness of 8 μm were synthesized, and fluorescence microscopy and a colorimetric protein assay revealed the successful inclusion of GOD into the ZIF‐8 layer with an enzyme concentration of 29±3 μg cm^?2. Enzymatic activity tests revealed that 50 % of the enzyme activity is preserved. Continuous enzymatic reactions, by the permeation of β‐d ‐glucose through the GOD@ZIF‐8 membranes, showed a 50 % increased activity compared to batch experiments, emphasizing the importance of the convective transport of educts and products to and from the enzymatic active centers.     

Hollow Zn/Co ZIF Particles Derived from Core–Shell ZIF‐67@ZIF‐8 as Selective Catalyst for the Semi‐Hydrogenation of Acetylene

The rational design of metal–organic frameworks (MOFs) with hollow features and tunable porosity at the nanoscale can enhance their intrinsic properties and stimulates increasing attentions. In this Communication, we demonstrate that methanol can affect the coordination mode of ZIF‐67 in the presence of Co²⁺ and induces a mild phase transformation under solvothermal conditions. By applying this transformation process to the ZIF‐67@ZIF‐8 core–shell structures, a well‐defined hollow Zn/Co ZIF rhombic dodecahedron can be obtained. The manufacturing of hollow MOFs enables us to prepare a noble metal@MOF yolk‐shell composite with controlled spatial distribution and morphology. The enhanced gas storage and porous confinement that originate from the hollow interior and coating of ZIF‐8 confers this unique catalyst with superior activity and selectivity toward the semi‐hydrogenation of acetylene.     

Carbon Dioxide Sensitivity of Zeolitic Imidazolate Frameworks

Zeolitic imidazolate frameworks of zinc, cobalt, and cadmium, including the framework ZIF‐8 commercially sold as Basolite Z1200, exhibit surprising sensitivity to carbon dioxide under mild conditions. The frameworks chemically react with CO₂ in the presence of moisture or liquid water to form carbonates. This effect, which has been previously not reported in metal–organic framework chemistry, provides an explanation for conflicting reports on ZIF‐8 stability to water and is of outstanding significance for evaluating the potential applications of metal–organic frameworks, especially for CO₂ sequestration.     

In Situ Fabrication of Inorganic/Organic Hybrid Based on Cu/Co‐ZIF and Cu2O

We successfully fabricate a well‐defined inorganic/organic hybrid Cu₂O@Cu/Co‐ZIF (ZIF=zeolitic imidazolate frameworks) by use of growth of dual‐metal Cu/Co‐ZIF on the obtained Cu₂O hollow spheres. The key point of the strategy is coupling the in situ self‐sacrificing template. Cu₂O and the coordination of metal ions (Cu⁺ and Co²⁺) with 2‐methylimidazole. This new hybrid was characterized by powder X‐ray diffraction, (scanning) transmission electron microscopy, energy‐dispersive spectroscopy mapping, in situ FT‐IR spectroscopy, UV/Vis diffuse reflection spectroscopy, N₂ sorption measurements, and electron spin resonance. It was evidenced that Cu/Co‐ZIF nanocrystals have been assembled to continuous shells surrounding the Cu₂O cores as well as in the voids between layers and inner pores. Cu₂O@Cu/Co‐ZIF exhibits visible light responsiveness and holds potential as narrow band gap semiconductor and visible photocatalyst.     

Ball‐Milling‐Induced Amorphization of Zeolitic Imidazolate Frameworks (ZIFs) for the Irreversible Trapping of Iodine

The I₂‐sorption and ‐retention properties of several existing zeolitic imidazolate frameworks (ZIF‐4, ‐8, ‐69) and a novel framework, ZIF‐mnIm ([Zn(mnIm)₂]; mnIm=4‐methyl‐5‐nitroimidazolate), have been characterised using microanalysis, thermogravimetric analysis and X‐ray diffraction. The topologically identical ZIF‐8 ([Zn(mIm)₂]; mIm=2‐methylimidazolate) and ZIF‐mnIm display similar sorption abilities, though strikingly different guest‐retention behaviour upon heating. We discover that this guest retention is greatly enhanced upon facile amorphisation by ball milling, particularly in the case of ZIF‐mnIm, for which I₂ loss is retarded by as much as 200 °C. It is anticipated that this general approach should be applicable to the wide range of available metal–organic framework‐type materials for the permanent storage of harmful guest species.     

Adsorption of CO2, CH4, and N2 on Zeolitic Imidazolate Frameworks: Experiments and Simulations

Experimental measurements and molecular simulations were conducted for two zeolitic imidazolate frameworks, ZIF‐8 and ZIF‐76. The transferability of the force field was tested by comparing molecular simulation results of gas adsorption with experimental data available in the literature for other ZIF materials (ZIF‐69). Owing to the good agreement observed between simulation and experimental data, the simulation results can be used to identify preferential adsorption sites, which are located close to the organic linkers. Topological mapping of the potential‐energy surfaces makes it possible to relate the preferential adsorption sites, Henry constant, and isosteric heats of adsorption at zero coverage to the nature of the host–guest interactions and the chemical nature of the organic linker. The role played by the topology of the solid and the organic linkers, instead of the metal sites, upon gas adsorption on zeolite‐like metal–organic frameworks is discussed.     

Zeolitic Imidazolate Framework/Graphene Oxide Hybrid Nanosheets as Seeds for the Growth of Ultrathin Molecular Sieving Membranes

A defect‐free zeolitic imidazolate framework‐8 (ZIF‐8)/graphene oxide (GO) membrane with a thickness of 100 nm was prepared using two‐dimensional (2D) ZIF‐8/GO hybrid nanosheets as seeds. Hybrid nanosheets with a suitable amount of ZIF‐8 nanocrystals were essential for producing a uniform seeding layer that facilitates fast crystal intergrowth during membrane formation. Moreover, the seeding layer acts as a barrier between two different synthesis solutions, and self‐limits crystal growth and effectively eliminates defects during the contra‐diffusion process. The resulting ultrathin membranes show excellent molecular sieving gas separation properties, such as with a high CO₂/N₂ selectivity of 7.0. This 2D nano‐hybrid seeding strategy can be readily extended to the fabrication of other defect‐free and ultrathin MOF or zeolite molecular sieving membranes for a wide range of separation applications.     

High‐Flux Zeolitic Imidazolate Framework Membranes for Propylene/Propane Separation by Postsynthetic Linker Exchange

While zeolitic imidazolate framework, ZIF‐8, membranes show impressive propylene/propane separation, their throughput needs to be greatly improved for practical applications. A method is described that drastically reduces the effective thickness of ZIF‐8 membranes, thereby substantially improving their propylene permeance (that is, flux). The new strategy is based on a controlled single‐crystal to single‐crystal linker exchange of 2‐methylimidazole in ZIF‐8 membrane grains with 2‐imidazolecarboxaldehyde (ZIF‐90 linker), thereby enlarging the effective aperture size of ZIF‐8. The linker‐exchanged ZIF‐8 membranes showed a drastic increase in propylene permeance by about four times, with a negligible loss in propylene/propane separation factor when compared to as‐prepared membranes. The linker‐exchange effect depends on the membrane synthesis method.     

Selective Capture of Carbon Dioxide under Humid Conditions by Hydrophobic Chabazite‐Type Zeolitic Imidazolate Frameworks

Hydrophobic zeolitic imidazolate frameworks (ZIFs) with the chabazite ( CHA ) topology are synthesized by incorporating two distinct imidazolate links. Zn(2‐mIm)_0.86(bbIm)_1.14 (ZIF‐300), Zn(2‐mIm)_0.94(cbIm)_1.06 (ZIF‐301), and Zn(2‐mIm)_0.67(mbIm)_1.33 (ZIF‐302), where 2‐mIm=2‐methylimidazolate, bbIm=5(6)‐bromobenzimidazolate, cbIm=5(6)‐chlorobenzimidazolate, and mbIm=5(6)‐methylbenzimidazolate, were prepared by reacting zinc nitrate tetrahydrate and 2‐mIm with the respective bIm link in a mixture of N,N‐dimethylformamide (DMF) and water. Their structures were determined by single‐crystal X‐ray diffraction and their permanent porosity shown. All of these structures are hydrophobic as confirmed by water adsorption isotherms. All three ZIFs are equally effective at the dynamic separation of CO₂ from N₂ under both dry and humid conditions without any loss of performance over three cycles and can be regenerated simply by using a N₂ flow at ambient temperature.     

Metal‐organic framework ZIF‐8 nanocrystals as pseudostationary phase for capillary electrokinetic chromatography

The outstanding properties such as large surface area, diverse structure, and accessible tunnels and cages make metal organic frameworks (MOFs) attractive as novel separation media in separation sciences. However, the utilization of MOFs in EKC has not been reported before. Here we show the exploration of zeolitic imidazolate framework‐8 (ZIF‐8), one of famous MOFs, as the pseudostationary phase (PSP) in EKC. ZIF‐8 nanocrystals were used as the PSP through dispersing in the running buffer (20 mM phosphate solution containing a 1% v/v methanol (pH 9.2)) to enhance the separation of the phenolic isomers (p‐benzenediol, m‐benzenediol, o‐benzenediol, m‐nitrophenol, p‐nitrophenol, and o‐nitrophenol). ZIF‐8 nanocrystals in the running buffer were negatively charged, and interacted with the phenolic hydroxyl groups of the analytes, and thus greatly improved the separation of the phenolic isomers. Inclusion of 200 mg L?¹ ZIF‐8 in the running buffer as the background electrolyte gave a baseline separation of the phenolic isomers within 4 min. The relative standard deviations for five replicate separations of the phenolic isomers were 0.2–1.1% for migration time and 4.5–9.7% for peak area. The limits of detection varied from 0.44 to 2.0 mg L?¹. The results show that nanosized MOFs are promising for application in EKC.     

Fabrication of ZIF‐8@SiO2 Core–Shell Microspheres as the Stationary Phase for High‐Performance Liquid Chromatography

The unique features of high porosity, shape selectivity, and multiple active sites make metal–organic frameworks (MOFs) promising as novel stationary phases for high‐performance liquid chromatography (HPLC). However, the wide particle size distribution and irregular shape of conventional MOFs lead to lower column efficiency of such MOF‐packed columns. Herein, the fabrication of monodisperse MOF@SiO₂ core–shell microspheres as the stationary phase for HPLC to overcome the above‐mentioned problems is reported. Zeolitic imidazolate framework 8 (ZIF‐8) was used as an example of MOFs due to its permanent porosity, uniform pore size, and exceptional chemical stability. Unique carboxyl‐modified silica spheres were used as the support to grow the ZIF‐8 shell. The fabricated monodisperse ZIF‐8@SiO₂ packed columns (5 cm long × 4.6 mm i.d.) show high column efficiency (23 000 plates m^?1 for bisphenol A) for the HPLC separation of endocrine‐disrupting chemicals (bisphenol A, β‐estradiol, and p‐(tert‐octyl)phenol) and pesticides (thiamethoxam, hexaflumuron, chlorantraniliprole, and pymetrozine) within 7 min with good relative standard deviations for 11 replicate separations of the analytes (0.01–0.39, 0.65–1.7, 0.70–1.3, and 0.17–0.91 % for retention time, peak area, peak height, and half peak width, respectively). The ZIF‐8@SiO₂ microspheres combine the advantages of the good column packing properties of the uniform monodisperse silica microspheres and the separation ability of the ZIF‐8 crystals.     

Porous Ionic Liquids or Liquid Metal–Organic Frameworks?

Porous liquids can be prepared from the dispersion metal–organic frameworks (MOFs) in ionic liquids (ILs). Porous liquids prepared from 5 % of ZIF‐8 in a phosphonium‐based ionic liquid are capable of absorbing reversibly up to 150 % more nitrogen and 100 % more methane than the pure ionic liquid.     

Extreme Flexibility in a Zeolitic Imidazolate Framework: Porous to Dense Phase Transition in Desolvated ZIF‐4

Desolvated zeolitic imidazolate framework ZIF‐4(Zn) undergoes a discontinuous porous to dense phase transition on cooling through 140 K, with a 23 % contraction in unit cell volume. The structure of the non‐porous, low temperature phase was determined from synchrotron X‐ray powder diffraction data and its density was found to be slightly less than that of the densest ZIF phase, ZIF‐zni. The mechanism of the phase transition involves a cooperative rotation of imidazolate linkers resulting in isotropic framework contraction and pore space minimization. DFT calculations established the energy of the new structure relative to those of the room temperature phase and ZIF‐zni, while DSC measurements indicate the entropic stabilization of the porous room temperature phase at temperatures above 140 K.     

Tailored Mobility in a Zeolite Imidazolate Framework (ZIF) Antibody Conjugate**

Zeolitic imidazolate framework (ZIF) hybrid fluorescent nanoparticles and ZIF antibody conjugates have been synthesized, characterized, and employed in lateral-flow immunoassay (LFIA). The bright fluorescence of the conjugates and the possibility to tailor their mobility gives a huge potential for diagnostic assays. An enzyme-linked immunosorbent assay (ELISA) with horseradish peroxidase (HRP) as label, proved the integrity, stability, and dispersibility of the antibody conjugates, LC-MS/MS provided evidence that a covalent link was established between these metal-organic frameworks and lysine residues in IgG antibodies.     

Preparation of Cu nanoparticle‐doped ZIF‐8/RGO composites for effective photodegradation of organic pollutant

Cu nanoparticle‐connected ZIF‐8/reduced graphite oxide (RGO) composite was successfully prepared through a facile hydrothermal reaction using sulfate in this paper. The crossover mechanism of metal nanoparticles loading and RGO decoration to enhance the photocatalytic efficiency of pristine ZIF‐8 was studied. The results showed that the prepared Cu‐S@ZIF‐8/RGO has a strong ability to take advantage of sunlight, indicating an appreciable application prospect. RGO can act as a base to support the whole structure and serve as an electron sink to accept photoexcited electrons, realizing the formation of reactive oxygen species (ROS) and inhibition of electron–hole pair recombination. Cu nanoparticles act as connectors between ZIF‐8 and RGO to transfer electrons and realize the formation of partial ROS on its surface. The doped sulfate radical can promote to extend the utilization of the wavelength range by generating surface states. Cu‐S@ZIF‐8/RGO showed the best photocatalytic activity in simulated sunlight for eliminating rhodamine B and 4‐chlorophenol among all the prepared samples, the structure kept intact even in the presence of different kinds of anions. The crossover study of metal loading and RGO decoration can develop a new way for only UV‐responsive metal–organic frameworks to remove organic contaminants under sunlight irradiation.     

Interactive Thermal Effects on Metal–Organic Framework Polymer Composite Membranes

Polymeric membranes are important tools for intensifying separation processes in chemical industries, concerning strategic tasks such as CO₂ sequestration, H₂ production, and water supply and disposal. Mixed‐matrix and supported membranes have been widely developed; recently many of them have been based on metal–organic frameworks (MOFs). However, most of the impacts MOFs have within the polymer matrix have yet to be determined. The effects related to thermal behavior arising from the combination of MOF ZIF‐8 and polysulfone have now been quantified. The catalyzed oxidation of the polymer is strongly affected by the MOF crystal size and distribution inside the membrane. A 16 wt % 140 nm‐sized ZIF‐8 loading causes a 40 % decrease in the observed activation energy of the polysulfone oxidation that takes place at a temperature (545 °C) 80 °C lower than in the raw polymer (625 °C).     

Nanoparticle Size‐Fractionation through Self‐Standing Porous Covalent Organic Framework Films

Covalent organic frameworks (COFs) have attracted attention due to their ordered pores leading to important industrial applications like storage and separation. Combined with their modular synthesis and pore engineering, COFs could become ideal candidates for nanoseparations. However, the fabrication of these microcrystalline powders as continuous, crack‐free, robust films remains a challenge. Herein, we report a simple, slow annealing strategy to construct centimeter‐scale COF films ( Tp‐Azo and Tp‐TTA ) with micrometer thickness. The as‐synthesized films are porous (SA_BET=2033 m² g^?1 for Tp‐Azo ) and chemically stable. These COFs have distinct size cut‐offs (ca. 2.7 and ca. 1.6 nm for Tp‐Azo and Tp‐TTA , respectively), which allow the size‐selective separation of gold nanoparticles. Unlike, other conventional membranes, the durable structure of the COF films allow for excellent recyclability (up to 4 consecutive cycles) and easy recovery of the gold nanoparticles from the solution.