Metal-organic Framework ZIF-8 Research Articles

Highly efficient Hg2+ removal via a competitive strategy using a Co-based metal organic framework ZIF-67

The stronger coordination ability of mercury ions with organic ligands than the metal ions in metal organic framework (MOFs) provides an accessible way to separate mercury ions from solution using specific MOFs. In this study, a Co-based MOF (ZIF-67, Co(mIM)2) was synthesized. It did not introduce specific functional groups, such as -SH and -NH2, into its structure through complicated steps. It separate Hg2+ from wastewater with a new strategy, which utilized the stronger coordination ability of Hg2+ with the nitrogen atom on the imidazole ring of the organic ligand than the Co2+ ions. Hg2+ replaced Co2+ nodes from ZIF-67 and formed a more stable precipitate with mIM. The experimental results showed that this new strategy was efficient. ZIF-67 exhibited Hg2+ adsorption capacity of 1740 mg/g, much higher than the known MOFs sorbents. mIMs is the reaction center and ZIF-67 can improve its utilization. The sample color faded from purple to white due to the loss of cobalt ion. It is a great feature of ZIF-67 that allows users to judge whether the sorbent is deactivated intuitively. ZIF-67 can be sustainable recycled by adding organic ligands to the solution after treatment due to its simple synthesis method at room temperature. It's a high-efficient and sustainable sorbent for Hg2+ separation from wastewater.

Thermal pyrolysis and kinetic analysis of a ZnxCo1−x ZiF-8 metal–organic framework for recent applications

Thermal pyrolysis and kinetic analysis of a ZnxCo1−x ZiF-8 metal–organic framework for recent applications

Highly stable Pebax® Renew® thin-film nanocomposite membranes with metal organic framework ZIF-94 and ionic liquid [Bmim][BF4] for CO2 capture

Ionic liquid [Bmim][BF4] and metal organic framework ZIF-8 and ZIF-94 nanoparticles were incorporated into polymer Pebax® Renew® 30R51 to obtain highly efficient thin-film nanocomposite membranes, ca. 300 nm thick.

Atomically dispersed Mn–N4 electrocatalyst with high oxygen reduction reaction catalytic activity from metal–organic framework ZIF-8 by minimal-water-assisted mechanochemical synthesis

Single-atomic Mn–N–C catalyst, which uses ZIF-8 synthesized by a minimal-water-assisted grinding method as the precursor, has high yields and shows high ORR activity in both acid and base solutions.

Study on the Improvement of Photocatalytic Performance by Constructing Zif-67 / Ag @ Ag2s System with Metal Organic Framework Zif-67 and Some Co Derivatives and Ag2s

Study on the Improvement of Photocatalytic Performance by Constructing Zif-67 / Ag @ Ag2s System with Metal Organic Framework Zif-67 and Some Co Derivatives and Ag2s

Application of Nanoparticles of Metal Organic Framework Zif-8 as Solute for Water Ultrafiltration Through Self-Supported Single-Walled Carbon Nanotube Buckypaper Membranes

Application of Nanoparticles of Metal Organic Framework Zif-8 as Solute for Water Ultrafiltration Through Self-Supported Single-Walled Carbon Nanotube Buckypaper Membranes

ZIF-8 metal organic framework materials as a superb platform for the removal and photocatalytic degradation of organic pollutants: a review.

Metal organic frameworks (MOFs) are attracting significant attention for applications including adsorption, chemical sensing, gas separation, photocatalysis, electrocatalysis and catalysis. In particular, zeolitic imidazolate framework 8 (ZIF-8), which is composed of zinc ions and imidazolate ligands, have been applied in different areas of catalysis due to its outstanding structural and textural properties. It possesses a highly porous structure and chemical and thermal stability under varying reaction conditions. When used alone in the reaction medium, the ZIF-8 particles tend to agglomerate, which inhibits their removal efficiency and selectivity. This results in their mediocre reusability and separation from aqueous conditions. Thus, to overcome these drawbacks, several well-designed ZIF-8 structures have emerged by forming composites and heterostructures and doping. This review focuses on the recent advances on the use of ZIF-8 structures (doping, composites, heterostructures, etc.) in the removal and photodegradation of persistent organic pollutants. We focus on the adsorption and photocatalysis of three main organic pollutants (methylene blue, rhodamine B, and malachite green). Finally, the key challenges, prospects and future directions are outlined to give insights into game-changing breakthroughs in this area.

Molecular Insights into Ch4/H2o Transport and Hydrate Formation in Hydrophobic Metal-Organic Frameworks Zif-8: Implication for Ch4 Storage by Adsorption-Hydration Hybrid Method

Molecular Insights into Ch4/H2o Transport and Hydrate Formation in Hydrophobic Metal-Organic Frameworks Zif-8: Implication for Ch4 Storage by Adsorption-Hydration Hybrid Method

Highly piezocatalysis of metal-organic frameworks material ZIF-8 under vibration

• The metal-organic frameworks ZIF-8 nanoparticles were synthesized via a liquid phase method. • Piezocatalytic degradation ratio for Rhodamine B reaches ∼94.5%. • Piezocatalytic is potential in dye wastewater treatment through utilizing vibration energy. In this research, metal-organic frameworks ZIF-8 nanoparticles, which is synthesized via the liquid phase method, exhibits the outstanding piezocatalytic performance on Rhodamine B (RhB) dye degradation under vibration. The piezocatalytic degradation ratio of RhB dye (5 mg/L) can reach ∼94.5% after undergoing 90 min vibration. ZIF-8, with the coexistence of cubic phase and monoclinic phase, confirmed from XRD, is piezoelectric in theory, which contributes to the excellent piezocatalytic performance. The main active species, which plays an important role in piezocatalytic process, are the superoxide radicals (· O 2 - ), the positive charges ( q + ) and the negative charges ( q - ) on basis of the active species quenching experiment results. The MOF material ZIF-8 is potential in the application field of the highly piezocatalytic dye wastewater degradation under vibration.

Structural and optical properties evolution in pressure-induced amorphization of metal-organic framework ZIF-8

Structural and optical properties evolution in pressure-induced amorphization of metal-organic framework ZIF-8

Ultrahigh selectivity of benzene/cyclohexane separation by ZIF-8 framework: Insights from spin-probe EPR spectroscopy

Liquid-phase separation of cyclohexane and benzene is both demanded and challenging, and the use of selective sorbents, such as metal-organic frameworks (MOFs), for extraction of one component from the mixture is the most promising solution. We report new mechanistic insights into diffusion of benzene and cyclohexane in well-known MOF ZIF-8 using recently developed methodology of encapsulated spin probes detected by Electron Paramagnetic Resonance (EPR). We demonstrate unambiguously that only one component of the hydrocarbons mixture, benzene, can penetrate into ZIF-8 particles, and these EPR-based conclusions are confirmed by high values of sorption selectivity measured by gas chromatography. However, systematic analysis of the mixtures containing small fractions of benzene (e.g. ∼1%) shows noticeable decrease in separation efficiency and only partial removal of benzene from diluted benzene/cyclohexane mixtures. This occurs due to the reverse diffusion of benzene from MOF particles into solution in equilibrium. At the same time, our diffusion study clearly points out that the membrane separation of benzene/cyclohexane using ZIF-8 should be highly perspective and pursued in the future.

Enhanced Proton Conduction of Graphene Oxide by the Addition of ZIF-8 for Room Temperature Relative Humidity Sensors

Graphene oxide (GO) is proven to be a very versatile material in sensing devices. As a moisture-sensitive material, it finds a wide variety of applications from biomedical to environmental, which is mainly related to its fast response and low cost. Here a treatment to GO using the metalorganic framework ZIF-8 is applied for the realization and study of humidity sensing. An incremental increase in sensitivity is demonstrated as we move from pure GO to GO blended with ZIF-8 to ZIF-8 dispersed on the GO surface, with two and three order of magnitude change in relative DC current respectively. The particles of ZIF-8 are uniformly dispersed on the GO surface with an average size of 200 nm contributing to ionic conductivity and improving the sensing capabilities. The dynamic analysis reveals that behind the enhanced sensitivity of the surface treated GO lays the fact that, in contrast to GO, the proton ion hopping mechanism kicks in from the lowest relative humidity values and the resistance follows the R~f-1 law throughout the whole relative humidity range, while at the same time it signifies the superficial origin of the sensing mechanism.

ZIF-8 metal-organic framework conjugated to pristine and doped B12N12 nanoclusters as a new hybrid nanomaterial for detection of amphetamine

Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were fulfilled to scrutinize the adsorption behavior of amphetamine (AMP) drug molecule on the pristine, aluminum, gallium, carbon, silicon, and germanium-doped ZIF-8/B12N12 nanoclusters. The adsorption analysis demonstrates that CB11N12/ZIF-8 has the strongest interaction with the nitrogen atom of AMP via binding energy of −194.58 kcal.mol−1 in the gas phase. DFT calculations in the various solvents reveal an enhancement in the AMP drug adsorption on the nanocluster with the increasing polarity of the solvent. The results of the electronic and reactivity properties of the considered drug-nanocluster complexes confirm that the energy gap of the nanoclusters reduces after the adsorption of the AMP drug, which could be used as a detectable electrochemical signal. The TD-DFT calculations illustrate that Al, Ga, C, Si, and Ge dopant increases the λmax of B12N12/ZIF-8 nanocluster (red-shift), whereas the electronic spectra of the drug-nanocluster complexes exhibits a blue-shift toward lower wavelengths. Finally, based on different analyses, the proposed XB11N12/ZIF-8 nanoclusters could be promising candidates for sensing and removal of the AMP drug.

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 study, CuO-ZnO/ZiF-8 was successfully synthesized with different percentages of ZiF-8 Metal-organic Framework (MOF) via ultrasound assisted precipitation method. The physic-chemical properties of the samples were studied by XRD, FESEM, EDX, BET-BJH, FTIR, DRS, and pH pzc techniques. The results showed that the CuO-ZnO/ZiF-8 (20) sample possesses high photocatalytic activity with 98.1% removal of 80 ppm AO7 in 100 min. It could be attributed to the increases the surface area, the pore volume, and pore diameter, as well as efficient homogenous distribution of active sites due to the use of ultrasound irradiation. Furthermore, the presence of ZiF-8 increases light absorption and reduces the recombination rate of electron-hole pairs. • Successfully synthesis of CuO-ZnO/ZiF-8 by ultrasonic assisted precipitation method. • Promising physicochemical and optical properties of the synthesized nanocomposites. • High photocatalytic activity of CuO-ZnO/ZiF-8 (20) (98.1% degradation of AO7) • Investigation of the effective operating parameters on AO7 photodegradation performance. 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.

MOFs Derived Hetero-ZnO/Fe2O3 Nanoflowers with Enhanced Photocatalytic Performance towards Efficient Degradation of Organic Dyes.

It is still a challenge for wastewater treatment to develop efficient yet low-cost photocatalysts on a large scale. Herein, a facile yet efficient method was devised to successfully synthesize ZnO/Fe2O3 nanoflowers (NFs) by using metal organic framework ZIF-8 as the precursor. The photocatalytic activities of the as-prepared hetero-ZnO/Fe2O3 NFs are purposefully evaluated by photocatalytic degradation of methylene blue (MB) and methyl orange (MO) under UV light irradiation. The resulting ZnO/Fe2O3 NFs display even higher photocatalytic activities than those of single-phase ZnO and Fe2O3 as a photocatalyst for the degradation of both MB ad MO. Particularly, nearly 100% MB can be photocatalytically degraded in 90 min under UV light irradiation using the hetero-NFs photocatalyst. The enhanced photocatalytic properties are probably ascribed to the synergistic contributions from the suitable band alignment of ZnO and Fe2O3, large surface area, and strong light absorption property. Radical scavenger experiments prove that the photogenerated holes, ·OH and ·O2-, play key roles in photocatalytic degradation process of organic dyes. Accordingly, the photocatalytic degradation mechanism of hetero-ZnO/Fe2O3 NFs towards dyes is tentatively proposed. The work contributes an effective way to rationally design and fabricate advanced photocatalysts with heterojunction structures for photocatalytic applications.

Materials for optical oxygen sensing under high hydrostatic pressure

Optical oxygen sensors based on indicators immobilized into porous and nonporous matrix materials were investigated in regard to their sensing behaviour under high hydrostatic pressure. The sensors were subjected to step-wise pressure increase up to approximately 200 bar in multiple cycles using a custom-made chamber. The investigated materials are based on oxygen indicators (a platinum(II) benzoporphyrin dye and ruthenium(II) polypyridyl complexes) immobilized in microparticles: silica gels of different porosities, controlled pore glass, poly(phenylsilsesquioxane), crosslinked polystyrene, the metal-organic frameworks ZIF-8 and UiO-66. The microparticles are in turn dispersed in highly oxygen-permeable silicone and Hyflon AD matrices. Homogeneous films of dye doped polystyrene and polyurethane hydrogels as well as non-porous polystyrene nanospheres directly dispersed in water were used for comparison purposes. All the porous materials were found to be stable under elevated hydrostatic pressure. Although the actual oxygen concentration remained unchanged upon increasing pressure, the sensors demonstrated an apparent decrease of calculated oxygen concentration (between −0.02 and −0.45 mg O2 L-1 H2O per 100 bar), which was fully reversible. Furthermore, the kinetics of the pressure response of the sensors was determined in experiments with high temporal resolution. Spikes attributed to pressure-induced oxygen diffusion between sensor components were observed within the first seconds after pressurization/depressurization.

Bismuth-doped g-C3N4/ZIF-8 heterojunction photocatalysts with enhanced photocatalytic performance under visible light illumination

ABSTRACT In this work, g-C3N4/ZIF-8 heterojunction photocatalysts were synthesised by the process by which the metal-organic framework ZIF-8 nanoparticles were grown onto the g-C3N4 layer in situ. Bismuth element was doped into the as-prepared g-C3N4/ZIF-8 material and a new type of Bi@g-C3N4/ZIF-8 composite photocatalysts was manufactured, in which the doping element acts in adjusting the bandgap in the photocatalysts. The prepared photocatalysts were characterised by XRD, FESEM, TEM, FTIR, XPS, UV–VIS DRS, photoluminescence and photo-electrochemical experiments. The results show that the ZIF-8 nanoparticles grown in situ were well-formed onto the g-C3N4 layer, and bismuth was evenly doped into the gaps of the g-C3N4/ZIF-8 framework. The degradation rate of methylene blue by CNZ-1.5(Bi)-12, which was a photocatalyst composed of 12% Bi-doped with g-C3N4/ZIF-8 material (the mass ratio of g-C3N4: ZIF-8 = 1:1.5), reached 86.6% under visible light irradiation within 60 min. The free radical scavenging experiment and electron spin resonance spectroscopy showed that was the main active substance. Bismuth doping into the photocatalytic system promotes the excitation of electrons from the valence band to the conduction band and provides a good channel for the transmission of photogenerated carriers as well. It is achieved that intensive visible light absorption, the enhanced separation efficiency of photogenerated carriers, and excellent thermal stability and high recyclability in the novel composite photocatalyst, owing to the synergistic effect of the introduced bismuth with the heterostructure of g-C3N4/ZIF-8. Therefore, the synthesised Bi@g-C3N4/ZIF-8 heterojunction photocatalysts may be used as a good photocatalyst for purifying and degrading organic matter in sewage.

Co, N co-doped hierarchical porous carbon as efficient cathode electrocatalyst and its impact on microbial community of anode biofilm in microbial fuel cell

The exploration of low-cost, long-term stable, and highly electrochemically active cathode catalysts is important for the practical application of microbial fuel cell (MFC). In this work, a series of the 3D hierarchical porous Co–N–C (3DHP Co–N–C) materials are designed and synthesized by a metal-organic framework ZIF-67 as a precursor and SiO2 sphere of different sizes as the hard template. The 3DHP Co–N–C-2 with 129 nm macropore exhibits excellent ORR performance in 0.1 M KOH solution with a half-wave potential of 0.80 V vs. RHE and superior durability than Pt/C (20%) due to the specific macropore-mesopore-micropore structure that exposes a large number of active sites and accelerates the electrolyte transport and oxygen diffusion. The MFC with 3DHP Co–N–C-2 as the cathode catalysts shows excellent performance with a maximum power density of 426.9±7.87 mW m−2 and favorable durability after 50 d of operation. In addition, 16s rDNA results reveal the presence of different dominant electrogenic bacteria and different abundance of important non-electrogenic bacteria in the anode biofilm in MFCs using cathode catalysts with different ORR activity. And 3DHP Co–N–C-2 was found to be beneficial to the synergistic effect of electrogenic and non-electrogenic bacteria. This study explores electrocatalysts in terms of both electrocatalytic activity and anode microorganisms, providing new and comprehensive insights into the power generation of MFC.

Molecular insights into hybrid CH4 physisorption-hydrate growth in hydrophobic metal–organic framework ZIF-8: Implications for CH4 storage

Adsorption-hydration hybrid method has been widely concerned due to its great application potential in CH4 storage/transportation. Monte Carlo and molecular dynamics simulations were performed to investigate the hybrid CH4 physisorption-hydrate growth in ZIF-8. The two-way migration phenomenon between water molecules inside the cavities and CH4 molecules outside the cavities first occurs in the physisorption process, which increases the CH4 adsorption capacity to a level close to that of dry ZIF-8. Due to the competitive adsorption for CH4 between ZIF-8 and hydrate surface, it is not conducive to the stability of intergranular CH4 hydrate before the CH4 adsorption capacity of ZIF-8 attains the maximum. After the maximum, intergranular hydrate could exist stably and grow continuously with the dissolution of CH4. Meanwhile, partially adsorbed CH4 molecules in the cavities migrate outwards and promote hydrate growth. These constitute the link between physisorption and hydrate growth. Because of the phase separation of CH4 and water molecules, hydrate cannot form in the ZIF-8 cavities. As a result, under the synergistic effect of physisorption and intergranular hydrates, CH4 storage capacity is significantly increased in H2O-oversaturated ZIF-8 compared with that in dry ZIF-8. Further, hydrophobic ZIF-8 surface facilitates hydrogen bonds formation in interfacial water by inducing ordered structures, and interfacial water as a medium promotes the contact between hydrate cage and ZIF-8 surface. An analysis of the diffusion properties of CH4/water molecules reveals that ZIF-8 cavities, hydrate cages, and intergranular liquid water exert inhibition on their self-diffusion coefficients in different degree. This study provides important microscopic insight into CH4 storage by adsorption-hydration hybrid in ZIF-8.

High Degradation of Methylene Blue Using a New Nanocomposite Based on Zeolitic Imidazolate Framework-8.

The development of broad-spectrum ultraviolet- and visible-light photocatalysts constitutes one of the most significant challenges in the field of photocatalytic pollutant removal. Here, the efficiency of the directly prepared nitrogen-doped quantum zeolitic imidazolate framework (ZIF)-8-dot catalyst for the photocatalytic degradation of the methylene blue dye was reported. The prepared catalysts were characterized using Brunauer–Emmett–Teller, X-ray diffraction, ultraviolet–visible spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy techniques. Under sunlight irradiation, the 1% nitrogen-doped quantum-ZIF-8-dot catalyst showed 75% photodegradation in half an hour and ≈93% photodegradation after 3 hours compared to ≈87% for the ZIF-8 metal–organic framework. The high performance of the 1% nitrogen-doped quantum-ZIF-8-dot catalyst was attributed to the synergism between the catalyst components, upconverted fluorescence property of nitrogen-doped quantum dots, and charge (electrons–holes) separation. The reactive radical test revealed that the hydroxyl radical was dominant. The step-scheme heterojunction mechanism for photocatalytic degradation was also deduced. The kinetic study through the photocatalytic isotherms revealed that the pseudo-first-order kinetic model can describe the reaction mechanism.