Zeolitic Imidazolate Framework ZIF-8 Research Articles

Molecular interactions of photosystem I and ZIF-8 in bio-nanohybrid materials.

Bio-nanohybrid devices featuring natural photocatalysts bound to a nanostructure hold great promise in the search for sustainable energy conversion. One of the major challenges of integrating biological systems is protecting them against harsh environmental conditions while retaining, or ideally enhancing their photophysical properties. In this mainly computational work we investigate an assembly of cyanobacterial photosystem I (PS I) embedded in a metal-organic framework (MOF), namely the zeolitic imidazolate framework ZIF-8. This complex has been reported experimentally [Bennett et al., Nanoscale Adv., 2019, 1, 94] but so far the molecular interactions between PS I and the MOF remained elusive. We show via absorption spectroscopy that PS I remains intact throughout the encapsulation-release cycle. Molecular dynamics (MD) simulations further confirm that the encapsulation has no noticeable structural impact on the photosystem. However, the MOF building blocks frequently coordinate to the Mg2+ ions of chlorophylls in the periphery of the antenna complex. High-level quantum mechanical calculations reveal charge-transfer interactions, which affect the excitonic network and thereby may reversibly change the fluorescence properties of PS I. Nevertheless, our results highlight the stability of PS I in the MOF, as the reaction center remains unimpeded by the heterogeneous environment, paving the way for applications in the foreseeable future.

Investigating the Structure of Defects in Heterometallic Zeolitic Imidazolate Frameworks ZIF-8(Zn/Cd) and Its Interaction with CO2 Using First-Principle Calculations

Inducing defect in metal-organic frameworks (MOFs) is one of the strategies to modify the structure and properties of this functional material. Defect may occur in a pristine MOF due to missing organic linkers, metal centres and/or other structural behaviours. In this study, the structure of defects in multicomponent MOFs especially heterometallic MOFs of zeolitic imidazolate framework (ZIF-8(Zn/Cd)) was examined to unveil the possible preference defect formation due to missing 2-methylimidazolate (MeIm) and metal centres of Cd2+ and Zn2+. Assuming defect formation due to the reaction between ZIF-8(Zn/Cd) and water, MeIm linker removal is energetically lower than removing metal centres of either Cd2+ or Zn2+. But, the MeIm linker is easier to be removed when it is connected to Cd2+ (Cd-MeIm-Cd) than when it is connected to Zn2+ (Zn-MeIm-Zn). Defect in ZIF-8(Zn/Cd) affects the band gap energy to give slightly lower value than it in pristine ZIF-8(Zn/Cd). Non-covalent interaction (NCI) and interaction region indicator (IRI) analyses were also performed to indicate possible intermolecular forces such as van der Waals and attractive forces present in non-defective and defective ZIF-8(Zn/Cd). The presence of defects in mixed-metal ZIF-8(Zn/Cd) was also tested for its potential use on CO2 adsorption. The interaction energy of CO2 inside defective ZIF-8(Zn/Cd) indicates an exothermic behaviour where CO2 molecule has a preference to be adsorbed inside the framework. This is especially when the capping agents at the defective ZIF-8(Zn/Cd) sites are removed to give open metal sites. This study provides insight how defects in multicomponent MOFs might presence affecting the structural and properties changes. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

A Novel Mechano-Synthesized Zeolitic Tetrazolate Framework for a High-Performance Triboelectric Nanogenerator and Self-Powered Selective Neurochemical Detection.

Designing a high-performing triboelectric novel material with eco-friendly, rapid, and cost-effective synthesis is the future of material research in triboelectric nanogenerators (TENG). We report a mechanochemical ball mill synthesis of a zeolitic tetrazolate framework (ZTF-8) that is isostructural with the well-known zeolitic imidazolate framework ZIF-8. ZTF-8 is extremely stable in water, 0.1 M aqueous acid/base solutions for 75 days at 25 °C, and boiling water (100 °C) for 7 days. Kelvin probe force microscopy and molecular electrostatic surface potential computational analysis exhibited that ZTF-8 has a very high positive surface potential. Atomic force microscopy and three-dimensional digital microscopy studies reveal the high roughness profile in the ZTF-8 film. The unique structure, exceptional acid/base stability, good dielectric property, and high roughness profile combined with the extremely electropositive nature of ZTF-8 make it a suitable candidate as a polymer-free triboelectric positive material in TENG with outstanding performance (power density of 720 mW/m2). High triboelectric output was further validated using the COMSOL Multiphysics simulation tool. Simple mechanical hand tapping of the ZTF-based TENG (ZTF-TENG) device generates high electric output, which was practically used to power numerous low-powered devices like tally counter, clinical thermometer, and digital clock and also illuminates 125 light-emitting diodes. In addition, the efficiency of ZTF-TENG was utilized as a self-powered device for a selective dopamine (DA) sensor with good sensitivity (377.76 mV/μM/cm2), wide range linearity (5-120 μM), and excellent limit of detection (0.42 μM).

Metal Organic Frameworks: Current State and Analysis of Their Use as Modifiers of the Vulcanization Process and Properties of Rubber.

The interest in and application of metal organic frameworks (MOF) is increasing every year. These substances are widely used in many places, including the separation and storage of gases and energy, catalysis, electrochemistry, optoelectronics, and medicine. Their use in polymer technology is also increasing, focusing mainly on the synthesis of MOF-polymer hybrid compounds. Due to the presence of metal ions in their structure, they can also serve as a component of the crosslinking system used for curing elastomers. This article presents the possibility of using zeolitic imidazolate framework ZIF-8 or MOF-5 as activators for sulfur vulcanization of styrene-butadiene rubber (SBR), replacing zinc oxide in conventional (CV) or effective (EF) curing systems to different extents. Their participation in the curing process and influence on the crosslinking density and structure, as well as the mechanical and thermal properties of the rubber vulcanizates, were examined.

Recovery of 2,3-Butanediol from Fermentation Broth by Zeolitic Imidazolate Frameworks.

The efficient separation of the 2,3-butanediol (2,3-BDO) intermediate from fermentation broth is an important issue in the production of biofuels from biomass-derived intermediates. Two zeolitic imidazolate frameworks ZIF-8 and ZIF-71 were investigated for the adsorption of 2,3-butanediol (2,3-BDO) from fermentation broth via liquid breakthrough adsorption measurements. While both ZIF materials initially show high separation performance, ZIF-71 retains robust separation performance even after aging in ethanol for two years, whereas the capacity of ZIF-8 decreases significantly. The robustness and stability of ZIF-71 are further confirmed with cyclic fixed bed adsorption measurements. The uptake of 2,3-BDO on ZIF-71 reaches >100 g/kg with negligible uptakes of sugars, organic acids, and other alcohols present in the fermentation broth. Excellent selectivity toward 2,3-BDO over water is also achieved. The 2,3-BDO-loaded ZIF-71 can be regenerated efficiently with ethanol as desorbent. These findings indicate that ZIF-71 shows considerable promise as an adsorbent to recover and purify diols from fermentation broths.

Fine-Tuning Electrolyte Concentration and Metal-Organic Framework Surface toward Actuating Fast Zn2+ Dehydration for Aqueous Zn-Ion Batteries.

Functional porous coating on zinc electrode is emerging as a powerful ionic sieve to suppress dendrite growth and side reactions, thereby improving highly reversible aqueous zinc ion batteries. However, the ultrafast charge rate is limited by the substantial cation transmission strongly associated with dehydration efficiency. Here, we unveil the entire dynamic process of solvated Zn2+ ions' continuous dehydration from electrolyte across the MOF-electrolyte interface into channels with the aid of molecular simulations, taking zeolitic imidazolate framework ZIF-7 as proof-of-concept. The moderate concentration of 2 M ZnSO4 electrolyte being advantageous over other concentrations possesses the homogeneous water-mediated ion pairing distribution, resulting in the lowest dehydration energy, which elucidates the molecular mechanism underlying such concentration adopted by numerous experimental studies. Furthermore, we show that modifying linkers on the ZIF-7 surface with hydrophilic groups such as -OH or -NH2 can weaken the solvation shell of Zn2+ ions to lower the dehydration free energy by approximately 1 eV, and may improve the electrical conductivity of MOF. These results shed light on the ions delivery mechanism and pave way to achieve long-term stable zinc anodes at high capacities through atomic-scale modification of functional porous materials.

ZIF-67 derived Co nanoparticles on ZIF-Derived carbon for hydrogen spillover and storage

Hydrogen spillover involves the dissociation of H2 on transition metal nanoparticles and further atomic hydrogen surface migration on catalyst supports. Hence, the spillover phenomenon has been reported in applications of heterogeneous catalysis in hydrogenation and room-temperature hydrogen storage. However, a proper catalyst design is requisite to initiate hydrogen spillover, considering the transition metal particle dispersion, sorbent surface modification, porosity, etc. In this report, we pyrolyzed the zeolitic imidazolate framework ZIF-67 for residual Co metal nanoparticles and N-dopant on ZIF-derived carbon (ZDC) for hydrogen adsorption via spillover effect. Catalyst optimization by proper ZIF carbonization process regarding manipulated pyrolytic temperatures, atmospheres, and ramping rates, results in different properties in ZDCs. Well-distributed Co nanoparticles can be obtained on N-rich graphitic sorbent ZDCs with retained high specific surface area. The Co on ZDC exhibits improved room-temperature hydrogen capacity of 0.77 wt% than neat ZIF-67 of 0.09 wt% at 30 bar, 300 K. The adsorption sites were examined experimentally by nitrogen hydrogenation, and possible atomic hydrogen diffusion was evaluated theoretically showing energy barrier reduced by over 0.1 eV. It demonstrates that cobalt nanoparticles can successfully initiate hydrogen spillover on ZIF-derived carbon with nitrogen functionality, even without noble metals.

Highly Water-Stable and Efficient Hydrogen-Producing Heterostructure Synthesized from Mn0.5Cd0.5S and a Zeolitic Imidazolate Framework ZIF-8 via Ligand and Cation Exchange.

Developing highly water-stable zeolitic imidazolate frameworks (ZIFs) for visible-light-driven photocatalytic hydrolysis is important and challenging. Herein, the Type II heterojunction catalyst Mn0.5Cd0.5S@ZIF-8 and its derivatives (including MCS@ZIF-8-Mn, MCS@ZIF-8-Br, and MCS@ZIF-8-MB) were successfully constructed using a facile strategy. Through dual postsynthetic ligand and cation exchange (PSE) treatments of Mn(Ac)2·4H2O and 4-bromo-1H-imidazole for ZIF-8, the hydrogen production efficiency of the MCS@ZIF-8-MB heterojunction catalyst can reach 5.450 mmol·g-1·h-1 and remain at 97.11% after 9 h of the stability test. Construction of heterojunctions can effectively improve the hydrogen production performance of Mn0.5Cd0.5S while maintaining excellent water stability. X-ray photoelectron spectroscopy results show that upon successful construction of the MCS@ZIF-8-MB heterojunction an interface forms between the surface of MCS and ZIF-8-MB, effectively weakening the photocorrosion of MCS. Density functional theory calculations also indicate that the induction of Mn can increase the electronic states of p and d orbitals near the Fermi level of ZIF-8, suggesting that Mn(II) attracts more electrons than Zn(II). This provides more powerful theoretical evidence for the electron cloud shift from the electron donor S2- to Mn2+.

High-Flux ZIF-8 Membranes on ZnO-Coated Supports for Propane/Propylene Separation

Zeolitic-imidazolate framework ZIF-8, a subclass of metal–organic frameworks (MOFs) with sodalite topology, has been a promising candidate for gas separation applications. Nevertheless, fabricating a high-flux propylene-selective ZIF-8 membrane is still challenging owing to the intrinsic crystalline nature of ZIF-8. In this study, an effective vapor-phase technique has been used to synthesize thin ZIF-8 membranes. ZnO was coated on anodic alumina oxide (AAO) supports via atomic layer deposition (ALD). The ZnO layer was vapor-phase treated with 2-methyl imidazole, which converted the ZnO layer to ZIF-8. The vapor-phase synthesized ZIF-8 membranes were evaluated for propylene/propane separation. With a ZIF-8 layer of ∼400 nm thickness, a high propylene/propane separation factor of 58 was obtained, concomitant with a high propylene permeance of 3.6 × 10–7 mol m–2 s–1 Pa–1. It was found that the vapor-phase solvent-free synthesis minimized the number of chemicals needed to fabricate a thin, highly permeable, and propylene-selective ZIF-8 membrane.

Polyhedral zeolitic imidazolate frameworks three-dimensional photonic crystals for highly sensitive chlorinated vapors sensing

Chlorinated vapors, as one of the poisonous volatile organic compounds (VOCs), seriously pollute the environment and threaten human health. It still remains a major challenge for designing reliable chlorinated vapors sensing materials with high sensitivity. Herein, we propose a simple yet powerful optical sensor based on zeolitic imidazolate frameworks ZIF-8 three-dimensional photonic crystals (3D PCs), which keeps high efficiency in vapor sensing through varying their effective refractive index (RI). ZIF-8 3D PCs sensors with tunable crystal facets and photonic bandgap were prepared by self-assembly of monodisperse polyhedral ZIF-8 particles, which are truncated rhombic dodecahedral (TRD)-, rhombic dodecahedral (RD)-, truncated cubic (TC)-, and spherical (Sphere) ZIF-8 3D PCs sensors. The application of polyhedral ZIF-8 3D PCs sensors for chlorinated vapors detection was investigated. The selectivity was found to be closely related to the exposed crystal facets, and the TRD ZIF-8 3D PCs sensor exhibited excellent selectivity, sensitivity (0.514 nm ppm−1), and sensing performance for chlorobenzene (C6H5Cl) vapor, the ultrafast response time (≤1 s) and remarkable long-term stability and recyclability, which might ultimately benefit for practical VOCs sensing applications.

Red emissive nanocomposite with high quantum yield for ultrasensitive and selective detection of latent fingerprints

Level 1–3 minutiae of latent fingerprints (LFPs) play essential roles in the identification of individuals. The level 3 details of sweat pores are especially important for accurate LFPs recognition, as they can provide microscopic features. Fluorescent materials with high quantum yield and red emission are advantageous in the LFPs detection, due to the associated potential of elevated sensitivity and contrast. Herein, a highly fluorescent red emissive nanocomposite material (PPDCDs@ZIF-8) was successfully prepared by combining carbonized polymer dots of PPDCDs with zeolitic imidazolate framework ZIF-8 in situ. The obtained material displays a strong and stable red emission at solid state with the maximum peak located at 630 nm, and the fluorescence quantum yield of PPDCDs is significantly improved from 17.8% to 43.5% after conjugation with ZIF-8. This nanocomposite material was successfully applied to detect LFPs on glass, metal, marble and other substrates with ultrahigh sensitivity. The obtained fluorescent images clearly revealed the detailed LFPs features from level 1 to level 3. Therefore, PPDCDs@ZIF-8 possesses great potential applications in crime scenes as it provides an easy and accurate strategy to visual the sweat pores in LFPs.

Synthesis of glycidol via transesterification glycerol with dimethylcarbonate in the presence of composites based on a layered titanosilicate AM-4 and ZIF-8

In this study, the one-pot synthesis of glycidol from glycerol (Gly) and dimethyl carbonate (DMC) was demonstrated in the presence of novel composite materials based on the microporous layered titanosilicate AM-4 (Aveiro-Manchester material number 4) and a zeolitic imidazolate framework ZIF-8. It was found that the reaction rate and selectivity towards glycidol depended on the ZIF-8 content in composite. Maximum 74.4% yield of glycidol with 92.5% conversion of glycerol was observed in the presence of 0.5%ZIF-8/AM-4 at DMC/Gly-molar ratio of 2, catalyst/glycerol weight ratio of 7.9 wt.% and temperature of 100°C for 8 h. The catalytic properties of developed ZIF-8/AM-4 composite correlated with (1) ZIF-8 particle size, (2) the decreasing basic sites strength, and (3) the increasing microporosity of materials.

Core-shell and hollow meso@microporous carbon derived from ZIF-8 @CMK-3 composites for Li-S batteries

Lithium-sulfur (Li-S) batteries have attracted much attention because of their potential as a new technology for high-energy batteries. However, the “shuttle effect” of polysulfide intermediates and poor conductivity of sulfur active species limit the development of Li-S batteries. Herein, a novel core-shell and hollow meso@microporous carbon matrix (ZIF-8(C)@CMK-3) is designed, which wraps N-doped carbon shell in the outer layer of ordered mesoporous CMK-3 through in-situ carbonization of thin zeolitic-imidazolate framework ZIF-8 layer. The combination of advantages of unique pore size, N-doping and core-shell architecture renders the resultant carbon matrix with enhanced electron/Li+ transport and the synergistic chemical/physical polysulfide anchoring. As a result, ZIF-8(C)@CMK-3 @S exhibits high reversible capacity (1597.2 mAh/g at a current density of 0.1 C) and well stability (596 mAh/g after 300 cycles at 2 C), and the fading rate per cycle capacity is 0.11%. The results indicated ZIF-8(C)@CMK-3 has a great potential to be used as efficient sulfur immobilizer for Li-S batteries.

Zeolitic imidazolate framework ZIF-67 grown on NiAl-layered double hydroxide/graphene oxide as cathode catalysts for oxygen reduction reaction in microbial fuel cells

In this study, the cathode catalysts for microbial fuel cells (MFCs) were successfully synthesized by two-step feeding method. NiAl-layered double hydroxide (LDH) nanoparticle was attached efficiently on the surface of graphene oxide (GO) in situ, zeolitic imidazolate framework (ZIF-67) was modified on LDH surface layer; Highly crystalline NiAl-LDH/GO@ZIF-67 composite was flawlessly prepared, nano-hybrid had (003), (006), (011), (112) and (222) characteristic crystal planes attribute to NiAl-LDH/GO and ZIF-67 by X-ray diffraction (XRD), and the sheet-like structure and polyhedral structure were observed. The NiAl-LDH/GO@ZIF-67 nano-hybrid was rich in metal elements and provides a wealth of electrochemical active sites by EDS test. The study displayed that the maximum output voltage of NiAl-LDH/GO@ZIF-67-MFC was 516 mV and the stabilization time could last for about 8 d. The maximum output power was 501.26 mW/m2, which was 1.31 times of NiAl-LDH/GO-MFC (381.92 mW/m2) and 2.76 times of ZIF-67-MFC (181.48 mW/m2). The GO with high conductivity was used as the substrate to ensure the stability of electrode cycle and the efficiency of power generation, the laminar structure of NiAl-LDH provided the specific surface area for the reaction, which facilitated the transport of electrons. The good structure of ZIF-67 increased the active sites of the composite. The excellent properties of the composites promoted the electrochemical stability and electricity production output of MFC. This study provided a method for the further application of MFC in the wastewater field.

Clarifying the zeolitic imidazolate framework effect on superior electrochemical properties of hydrogen storage alloys

Zeolitic imidazolate framework ZIF-8 polyhedral crystal is coated uniformly on the surface of hydrogen storage alloys (HSAs) using a simple method of wet-chemical. On the one hand, the adsorption of H2 on ZIF-8 verified by density functional theory simulations is in favor of the suppression of side reaction of H2 evolution, enlisting the improved discharge capacity. On the other hand, the adsorbed H2 on ZIF-8 is able to be desorbed to H atom further adsorbed on HSAs, increasing the H concentration on electrode/electrolyte interface, which is beneficial to the enhanced electrochemical reaction rate and H diffusion rate. As a consequence, compared with the bare HSAs electrode, the HSAs/ZIF-8 hybrid electrode exhibits excellent electrochemical performances for enhanced maximum discharge specific capacity (302.6 vs. 328.2 mAh g–1) and superior high-rate dischargeability (capacity retention increases from 13.5 to 30.2% at a discharge current density of 3000 mA g–1). Furthermore, another ZIF-based system of HSAs/ZIF-67 electrode shows similar electrochemical properties to the HSAs/ZIF-8 electrode; besides, the extended system of HSAs/ZIF-8-graphene hybrid electrode also exhibits enhanced rate capabililty.

Unusual CO2 Adsorption in ZIF-7: Insight from Raman Spectroscopy and Computational Studies.

Here, we use Raman spectroscopy to investigate temperature-dependent changes in the atomic-scale structure of the zeolitic imidazolate framework ZIF-7 in a CO2 atmosphere and uncover the mechanism of maximal CO2 adsorption at 206 K. At 301 K, the Raman spectra of ZIF-7 at various CO2 gas pressures reveal a narrow-pore (np) to large-pore (lp) phase transition commencing at 0.1 bar as a result of adsorption of CO2, as evident in the appearance of Fermi resonance bands of CO2 at 1272 and 1376 cm-1. Moreover, the Raman inactive bending mode of CO2 becomes active due to geometrical distortion of adsorbed CO2. It further splits into two peaks due to hydrogen bonding interactions between CO2 and the benzene ring of the benzimidazole linker ZIF-7, as supported by our computational studies. In addition, the interaction between CO2 molecules plays a key role. Upon reducing the temperature at 1 bar CO2 gas pressure, ZIF-7 exhibits softening of the imidazole puckering mode and the Fermi resonance CO2 band due to interactions between CO2 and the framework through hydrogen bonding. At 206 K, substantial modification in the lattice mode and disappearance of the Raman inactive CO2 bending mode confirm the changes in the size of the pore cavity through structural rearrangements of CO2.

Impact of zinc salt counterion on poly(ethylene oxide) solution viscosity, conductivity, and ability to generate electrospun MOF/nanofiber composites

The effect of seeding poly(ethylene oxide), PEO, aqueous solutions with zinc acetate (ZA) and zinc chloride (ZC) on solution properties (e.g., viscosity and electrical conductivity) and the ability to electrospin nanofibers was investigated. The impacts of the type of Zn counterion and overall salt concentration on solution viscosity and electrical conductivity were correlated to the ability to electrospin nanofibers, as well as the resulting fiber morphology. In dilute PEO solutions, Zn salt addition reduced the PEO hydrodynamic radius ( R h ) and viscosity likely as a result of PEO chain envelopment of Zn cations, while in semi-dilute entangled regimes, Zn salt addition increased R h and viscosity likely due to interactions a single Zn cation with multiple polymer chains. The addition of Zn salts had limited effects on the overlap concentration ( c* ), but increased the entanglement concentration ( c e ), and the presence of either ZA or ZC enabled electrospinning of bead-free fibers at lower PEO concentrations (than without salt) because of the increased electrical conductivity of the solution. However, increasing the ZA concentration in solution had limited effect on fiber diameter and morphology, while raising the ZC concentration in solution resulted in the fusion of fibers into webs and films likely due to charge carryover. The resulting salt-doped PEO nanofibers were used as a template to synthesize a zeolitic imidazolate framework, ZIF-8, through a vapor-deposition approach exploiting the embedded Zn as nucleation sites for heterogeneous growth in a ‘Fiber-first’ strategy. • Aqueous poly(ethylene oxide) solutions were seeded with zinc salts. • Zinc salts, notably Zn acetate, reduced polymer concentration required to spin bead-free fibers. • Zinc chloride, especially at higher loadings, led to electrospun fused webs instead of fibers. • Zinc counterion type impacted solution conductivity and affected bead-free fiber development. • Zinc salt seeding enabled the vapor-phase growth of the zeolitic imidazolate framework ZIF-8.

Molecular simulation of adsorption and diffusion of H2 /CO2 /CO /MeOH /EtOH mixture into the zeolitic imidazolate framework ZIF-8

The adsorption and diffusion behaviors of H2, CO2, CO, MeOH, and EtOH into ZIF-8 were studied in pure and mixtures (binary and total) states by grand canonical Monte Carlo and molecular dynamics simulation, respectively. In addition, the separation of MeOH over the other guest molecules was also investigated in the mentioned mixtures. The results of molecular dynamics simulations showed that the diffusion coefficients of pure guest molecules followed the trend of H2> CO2> CO > MeOH > EtOH. Analysis of adsorption indicated that all of the guest molecules (except H2) have S-shaped adsorption isotherms with an initial low-uptake region, which can be ascribed to the cage-filling phenomenon. However, the trend of the initial sorption plateau range is CO2> CO > MeOH > EtOH. In the mixture used guest molecules, the most separation is related to the separation of MeOH from H2 and EtOH, which is the optimal separation of MeOH from H2 at pressures less than 1584 kPa and the optimal separation of MeOH from EtOH at a pressure of 10,000 kPa.

Pyrolysis-derived materials of Mn-doped ZIF-67 for the electrochemical detection of o-nitrophenol

• Carbonized Mn-doped ZIF67 electrocatalytically detects two groups on o-nitrophenol. • Broad linear range of 0.5–100 μM and LOD of 0.16 μM for o-nitrophenol measurement. • Recovery from real water samples w/ added o-nitrophenol exceeded that of UV method. The zeolitic imidazolate framework ZIF-67 can be used as a favorable catalyst carrier owing to its unique structure. Although the catalytic activity of ZIF-67 can be considerably improved by doping with transition metals such as manganese, manganese-doped ZIF-67 has rarely been applied in electrocatalysis. In this study, manganese-doped ZIF-67 was carbonized to form CoC@Mn and to prepare an electrochemical sensor for detecting o -nitrophenol ( o- NP). The results showed that CoC@Mn exhibits a good electrocatalytic performance. The constructed sensor possessed a linear range of 0.5–100 μM for the detection of o- NP, with a detection limit of 0.16 μM. In addition, it was found to accurately detect o- NP in real lake and tap water samples. CoC@Mn is therefore expected to be an efficient electrocatalyst for detecting o- NP as an industrial pollutant.

Structure and dynamics of a water/methanol mixture confined in zeolitic imidazolate framework ZIF-8 from atomistic simulations.

A classical atomistic simulation study is reported for the microscopic structure and dynamics of a water/methanol mixture confined in flexible nanoporous zeolitic imidazolate framework ZIF-8. Both the radial density distribution and vivid two-dimensional density profile demonstrate that methanol molecules can roughly be viewed as "embedded" between two layers of water molecules to form a "sandwich" structure. The reason for the formation of such a specific structure is explained based on the hydrogen-bonding state and the strength of various hydrogen bonds. The investigation of guest molecular diffusion shows that the self-diffusion coefficient of confined water is generally one to two orders of magnitude smaller than that of bulk water. In addition, the dependence of the self-diffusion coefficient on loading is non-monotonic: the self-diffusion coefficient firstly shows a significant increase and then decreases at higher loading. Moreover, both the structure and dynamics of the hydrogen bond (HB) network of confined water molecules are investigated in a spatially resolved manner. The results indicate that both the HB structure and dynamics of water molecules near the ZIF-8 surface deviate significantly from those of bulk water. However, while water molecules located at the pore center are relatively similar to bulk water molecules with respect to the HB structure, they exhibit strong slowdown in HB dynamics when compared with bulk water. This simulation study elucidates in detail the structural and dynamical properties of a water/methanol mixture in nanoscopic ZIF-8 confinement, which is expected to provide a deep insight into the role of porous fillers, such as ZIF-8, in improving the performance of the dehydration of alcohols via pervaporation and other related processes.