Zeolitic Imidazolate Framework Research Articles

Electrochemical Kinetic Behaviors and Sensing Performance of Au@ZIF-8 and Ag@ZIF-8 Nanocomposites-Based Platforms Towards Ultrasensitive Detection of Chloramphenicol

Silver (Ag) and gold (Au) nanoparticles (NPs) are incorporated into the zeolitic imidazolate framework-8 (ZIF-8) host matrix, which is successfully coated the screen-printed electrodes (SPEs) for the effective detection of chloramphenicol (CAP). The morphological and structural characteristics are examined using scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. Additionally, the electrochemical characteristics and sensing performance of CAP on the proposed electrodes are investigated in detail using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CA), and differential pulse voltammetry (DPV) measurements, respectively. The results suggest the SPEs modified with Ag@ZIF-8 and Au@ZIF-8 exhibit impressive enhancements in sensitivity, linear concentration range, limits of detection (LODs), and repeatability. Under the optimum conditions, the proposed electrochemical sensors had a linear range of 0.25–50 μM for Ag@ZIF-8/SPE and 5–50 μM for Au@ZIF-8/SPE, corresponding to LODs of 0.16 and 0.404 μM, respectively. Notably, a series of kinetic parameters related to the redox reactions of both standard Fe(CN)6 3−/4− probe and CAP molecules in phosphate-buffered saline (PBS) buffer are determined. Furthermore, valuable insights into the influence mechanism nature of Ag@ZIF-8 and Au@ZIF-8 nanocomposites on the electrochemical behaviors are proposed, demonstrating the great potential of the developed sensors for CAP detection.

Carbon dots encapsulated zeolitic imidazolate framework-8 as an enhanced multi-antioxidant for efficient cytoprotection to HK-2 cells

Excessive reactive oxygen species (ROS) can lead to the imbalance of antioxidant system in the body and cause oxidative damage to cells. It is imperative to rationally design nanomaterials with high catalytic activity and multiple antioxidant activities. Here, line peppers-derived carbon dots (CDs) is encapsulated into zeolitic imidazolate framework-8 (CDs@ZIF-8) to achieve enhanced antioxidant activities for improved protective effect on cells. This nanosystem has a broad spectrum of antioxidant properties, which can effectively remove a variety of intracellular ROS and protect cells from ROS-induced death and cytoskeleton damage. In addition, CDs@ZIF-8 can reduce malondialdehyde (MDA) level and increase the enzyme activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx), as well as the level of glutathione (GSH) in human kidney proximal tubular epithelial cells (HK-2) cells. Mechanism studies demonstrated that CDs@ZIF-8 can up-regulate the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), allowing the regulation of antioxidant enzymes to further achieve antioxidant effect. Besides, CDs@ZIF-8 inhibited the secretion of proinflammatory cytokines. This work demonstrates that the constructed CDs@ZIF-8 with multi-antioxidant activity can act as a highly efficient intracellular ROS scavenger and provide potential for the application in related oxidative stress-induced diseases.

Enhancing Li+ transfer efficiency and strength of PEO-based composite solid electrolyte for long stable cycling of all-solid-state lithium metal batteries

The metal-organic frameworks (Zeolitic imidazolate framework-67, ZIF-67) were in-situ grown on the cellulose skeleton surfaces which are rich in hydroxyl groups, and combined with PEO-based electrolytes to form composite solid electrolytes (CSEs). The assembled Li/CSEs/Li exhibit an ultra-long cycle life (>2000 h, 50°C; >2500 h, 30°C) and excellent lithium-ion transference efficiency (tLi+=0.46) at 50°C. This work provides a new pathway for the development of high-safety and low-cost all-solid-state batteries.

Synergistic effect in ZIF-67/MoS2 entrenched MWCNT photo (electro) catalyst for degradation of tetracycline and alternative to Pt counter electrode in dye-sensitized solar cells

Photocatalytic water purification is an effective environmental protection approach for removing hazardous chemicals in water, besides solar energy conversion is a trustworthy and sustainable choice for the future due to rising energy demands. The present research focus is on synthesis of Metal-Organic Framework (MOF) based composite, Zeolitic Imidazolate Framework-67/Molybdenum Disulfide (ZIF-67/MoS2) entrenched Multi-Walled Carbon Nanotubes (MWCNT) as a catalyst for photodegradation of tetracycline (TC), as well as substitute for Pt counter electrode in Dye-Sensitized Solar Cell (DSSC). The crystalline structure, optical response, shape, porosity, quantum states, and chemical configuration were determined using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet-Visible Diffuse Reflectance Spectroscopy (UV-DRS), Photoluminescence spectroscopy (PL), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET), and X-ray Photoelectron Spectroscopy (XPS), respectively. The degradation efficiency of ZIF-67/MoS2/MWCNT catalyst under effect of operational parameters namely, photocatalyst dosage, solution pH, coexisting ions, TC concentrations and irradiation time were studied consecutively. ZIF-67/MoS2/MWCNT composite achieved 96.1% degradation efficiency of TC under white light irradiation. Interestingly, when utilized as a counter electrode in DSSCs, this composite-based electrode delivered the highest Power Conversion Efficiency (PCE) of 3.86% with a short-circuit current density (JSC) of 7.54mAcm-2 and open-circuit voltage (VOC) of 0.79V. The observed enhancement is attributed to lesser peak-to-peak separation (EPP), lower electron lifetime, lower charge transfer resistance (RCT) and higher exchange current density (J0). Based on these findings, ZIF-67 inclusion in MoS2/MWCNT composite is not only an effective catalyst for water treatment but also a good catalyst for I3− reduction in DSSCs.

The enhanced oxidase-like activity of modified nanoceria/ZIF-67 for fluorescence and smartphone-assisted visual detection of tannic acid

As a substitute for natural enzymes, nanozymes have unique characteristics of high catalytic activity, excellent stability and low cost, making them pivotal in sensing applications. Among them, nanozymes with oxidase-like activity garner significant attention for antioxidant detection, as they efficiently catalyze the oxidation of antioxidants in the presence of oxygen. Herein, a nanozyme with an enhanced oxidase-like activity was synthesized through a 3-step strategy, that is, ceria nanoparticles were firstly modified with amino acid and oligopeptides, then combined with zeolitic imidazolate framework-67 (ZIF-67), and finally the composite was etched in neutral water. The as-synthesized nanozyme can oxidize the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) or Amplex Red (AR) in the presence of oxygen, inducing a change in their color or fluorescent signals, verifying its oxidase-like activity. Tannic acid (TA), an antioxidant, competes with TMB/AR for oxidation by the nanozyme. Leveraging this competitive relationship, a fluorescent and portable trichromatic sensor was developed for the detection of tannic acid (TA) in food samples. The fluorescent sensor shows high sensitivity with detection limits (S/N = 3) of 0.011 µM, and the trichromatic sensor presents comparable performance to colorimetric sensor, exhibiting a linear range of 30–270 µM and detection limit of 1.03 µM. By using a smartphone platform, the trichromatic sensor enables convenient, rapid, inexpensive, and quantitative assessment of TA. Both two sensors were successfully applied to TA detection in 9 different foods. This study not only provides an effective strategy to enhance enzyme performance but also paves the way for their applications in food testing.

Three-dimensional porous structured cobalt- and nitrogen-doped carbon nanotube electrocatalyst derived from cobalt-based zeolitic imidazolate framework nanoleaves for high performance zinc-air battery

The development of efficient and cost-effective electrocatalysts to overcome the intrinsic sluggish kinetics of the oxygen reduction reaction (ORR) in zinc-air batteries is crucial. In this study, we introduce a strategy that integrates a template-assisted synthesis with subsequent thermal treatment to fabricate an active and stable cobalt-based nitrogen-doped carbon electrocatalyst, denoted as Co-N-CNT. The strategy adjusts the disordered architecture of the zeolitic imidazolate framework (ZIF) through the synergistic effect of bimetallic species, restricted the growth of zeolitic imidazolate framework nanoleaves (ZIF-L) using salt templates, and directed the transformation from a two-dimensional blade-like morphology to a three-dimensional multi-tiered composite structure. Notably, the Co-N-CNT-800 sample, synthesized at an optimized pyrolysis temperature of 800 °C, exhibits a half-wave potential of 0.89 V and demonstrates stability with sustained cycling over 21 h, which is comparable to the performance of commercial Pt/C electrocatalysts. Moreover, when employed as the cathode in zinc-air batteries, Co-N-CNT-800 not only surpasses Pt/C in terms of power density but also exhibits long-term charge/discharge stability. This findings offer a viable pathway for the design of active and cost-effective ORR electrocatalysts, holding promise for applications in the electrochemical energy storage and conversion systems.

MOFs meet wood with enlarged pores: A high-capacity and efficient removal of ciprofloxacin from water

The abuse of ciprofloxacin (CIP) has caused considerable worry because it not only seriously contaminates the environment but also endangers the ecology. Thus, effective antibiotic wastewater treatment technologies should be explored. In this paper, Hypericum residues were first pretreated with acidic deep eutectic solvents (DES) to remove lignin and hemicellulose (DH1 and DH2). Then, zeolite imidazolate frameworks (ZIF-8 and ZIF-67) were loaded on the wood to obtain four composites (collectively referred to as DH/ZIF), which were used for CIP removal from wastewater. The enlarged pore size of the wood's provided sufficient attachment sites for ZIF-8 and ZIF-67, which facilitated the efficient adsorption of CIP by the composites. The adsorption of CIP by all four composites (DH1/ZIF-8, DH2/ZIF-8, DH1/ZIF-67, DH2/ZIF-67) was above 1400 mg/g. The results of characterization, data fitting and parameterization suggest that pore filling, hydrogen bonding, electrostatic interactions and π-π stacking are the main mechanisms of CIP adsorption. In summary, DESs show great potential and broad utility in modifying waste biomass and compounding it with MOF to remove antibiotic contaminants.

Zeolitic imidazolate framework-8@polydopamine decorated carboxylated chitosan hydrogel with photocatalytic and photothermal antibacterial activity for infected wound healing

Open wounds are susceptible to bacterial infections, and antibiotics are commonly used to treat these infections. However, widespread use of antibiotics will easily induce bacterial resistance. Green antibacterial agents serve as excellent alternative for antibiotics in infection therapy. In this work, polydopamine (PDA) was used to modify the surface of ZIF-8, which not only enhances the water stability of Zeolitic imidazolate framework-8(ZIF-8) but also improves its photocatalytic and photothermal capabilities. ZIF-8@PDA was incorporated into carboxylated chitosan (CCS) films as an antibacterial agent, the resulting ZIF-8@PDA-CCS films exhibit excellent ionic/photocatalytic/photothermal antibacterial performance. The film exhibited an impressive 99% in vitro bacterial inhibition rate. After treatment with ZIF-8@PDA-CCS, the bacteria in infected wounds can be completely suppressed. These findings suggest that ZIF-8@PDA-CCS could serve as a potentional antibacterial dressing.

Enhanced H2S gas sensing utilizing UV-assisted In2O3@ZnO nanosheets

In the realm of environmental protection, there is a growing demand for efficient and environmentally friendly gas sensors. In this study, we employed a simple hydrothermal method to synthesize nanosheets composed of zinc oxide (ZnO)-doped indium oxide (In2O3), utilizing zeolitic imidazolate framework-8 (ZIF-8) as a precursor. These nanosheets demonstrated exceptional sensitivity and selectivity in detecting hydrogen sulfide (H2S) gas. A comprehensive analysis of crystal structure, chemical states, elemental composition, surface area, and morphology was conducted. Brunauer–Emmett–Teller (BET) surface area measurements to assess the materials' textural properties revealed that the nanosheets labeled In2O3/0.1ZnO possessed a high specific surface area of 49.02 m2/g, greater than the 45.65 m2/g of pure In2O3 nanosheets, a crucial factor contributing to the observed exceptional sensitivity and selectivity in detecting H2S gas. Particularly noteworthy is the substantial improvement in gas detection response from 109.9 to 146.2 (approximately 24.7 %) observed in the In2O3/0.1ZnO material under UV irradiation at the optimal temperature of 250 °C. This enhancement emphasizes the material's potential for superior gas detection. The incorporation of ZIF-8-derived ZnO nanostructures played a crucial role in creating additional active sites, further enhancing the gas-sensing capabilities. Importantly, this innovative synthesis technique ensures the production of clean, non-toxic materials, aligning with environmental conservation objectives, and holds promise for achieving heightened sensitivity and selectivity in the detection of environmentally harmful gases.

Synergy of pore confinement and co-catalytic effects in Peroxymonosulfate activation for persistent and selective removal of contaminants

The activation of peroxymonosulfate (PMS) through nanoconfinement and co-catalytic effects has demonstrated considerable promise in environmental remediation. Nevertheless, the attainment of persistent efficiency and specificity for pollutant degradation remains a formidable obstacle. Herein, we proposed a solvent-free molten approach to convert a mixture of zeolitic imidazolate frameworks (ZIFs) and MoS2 into 3D integrated cobalt-molybdenum bimetallic nitrogen-doped porous carbon foam with catalytic/co-catalytic performance (MC@NCF). The integrated materials exhibited exceptional efficiency in degrading contaminants based on the synergy of pore confinement and co-catalytic effects, achieving almost 100 % tetracycline degradation in 10 min with a k-value as high as 112.44 min−1·M−1, which was superior to the existing catalysts reported so far. The experimental findings revealed that the structural adjustment of MC@NCF significant accelerated the mass transfer through the formation of interfacial Mo-S/O-Co and Mo-N-Co/C bonds electron-tuning bridges between pore-confined micro-units, leading to the increased singlet oxygen (1O2) yield. Therefore, the MC@NCF exhibited more remarkable stability without interference from coexisting inorganic ions and cations, humic acid, and water matrices. Moreover, a flow-through nanoreactor was constructed and acquired efficient reactivity with negligible biotoxicity, and easy nanocatalyst recycling after continuous operation. The possible reactivity mechanism was identified by Frontier molecular orbital theory HOMO-LUMO, Fukui function, LC-MS, EPR, in-situ ATR-FTIR, and Raman analyses. Our results will guide integrated “catalytic/co-catalytic” nanoconfined MOF derivatives design to further enhance deep water purification technology.

Metal-polyphenol network loaded ZIF-8 for efficient removal of fluoroquinolone antibiotics

A metal-polyphenol network functionalized on surface of zeolitic imidazolate framework-8 (MPN@ZIF-8) were fabricated for efficient removal of fluoroquinolones (FQs) antibiotics. Polyphenol as one kind versatile molecular glue was employed as organic ligand as well as linkage for growth and deposition of metal-polyphenol network (MPN) on ZIF-8 supporter. The prepared MPN@ZIF-8 composite was characterized by various methods. The parameters including the dosage of adsorbents, pH value, adsorption time and salt concentration affecting the adsorption process were systematically investigated. FQs adsorption isotherms and kinetics best fitted the Langmuir isotherm (R2 > 0.980) and pseudo-second-order model (R2 > 0.987), respectively. Thermodynamic studies showed that adsorption process of Norfloxacin (NOR), Ciprofloxacin (CIP) and Enrofloxacin (ENR) were all spontaneous. The adsorption capacity of MPN@ZIF-8 were 104.60, 86.23 and 66.21mgg-1 for NOR, CIP and ENR, respectively, which were significantly higher than those of precursor ZIF-8. The potential adsorption mechanism was stated, most likely involved in π-π interaction, hydrogen-bond and electrostatic interaction between the FQs and the MPN@ZIF-8. In addition, the removal efficiency of the three FQs on MPN@ZIF-8 was still above 95% after recycle for four times. The recoveries of the three FQs were in the range of 77.1- 100.1% with RSDs below 7.8% in real sample analysis. Compared with the methods in preparation of MOF-based composite, the fabrication method mentioned in this study is versatile, very easy, environmental friendly and low cost, which has potential in large-scale production for application in environmental remediation.

Hydrophobic, zincophilic and conductive SEI protective layer stabilizes metallic Zn anode under high current densities

The uncontrollable growth of Zn dendrites and adverse side reactions significantly hinder the application of metallic Zn anodes in aqueous batteries. Herein, nitrogen-doped carbon skeleton/ZnO nanocrystalline are grown in-situ within carbon hollow dodecahedrons (denoted as CZCHD) through the controlled pyrolysis of zeolitic imidazole framework-8 dodecahedrons coated with polydopamine. The solid electrolyte interface layer constructed by CZCHD suppresses hydrogen evolution and corrosion reactions, reduces nucleation barrier, improves Zn deposition kinetics, accelerates desolvation and transport of Zn2+ ions, and regulates Zn deposition behavior. When tested in symmetric cells, CZCHD@Zn anodes afford exceptional plating/stripping stability at 5 mA cm−2/1 mAh cm−2 (2681 h), 10 mA cm−2/10 mAh cm−2 (780 h), and 20 mA cm−2/20 mAh cm−2 (240 h). In asymmetric cells, CZCHD@Cu exhibits average Coulombic efficiency of 99.5 % over 500 cycles. Morphological and structural evolution analyses demonstrate the preferential horizontal flaky Zn deposition beneath the CZCHD protective layer, with no Zn dendrites observed on the surface. Furthermore, when coupled with MnVO cathodes, the assembled full cells display stable cycling performance at 2 and 5 A/g. The stable, reversible, efficient, dendrite-free Zn deposition is attributed to the synergistic effects of high hydrophobicity, strong zincophilicity and high electrical conductivity of CZCHD, which is confirmed by contact angle measurements, theoretical calculations based on density functional theory, and electrochemical impedance spectroscopy.

ZIF-8-based Nanoparticles for Inflammation Treatment and Oxidative Stress Reduction in Periodontitis.

Periodontitis, an inflammatory bone resorption disease associated with dental plaque, poses significant challenges for effective treatment. In this study, we developed Mino@ZIF-8 nanoparticles inspired by the periodontal microenvironment and the unique properties of zeolitic imidazolate framework 8, aiming to address the complex pathogenesis of periodontitis. Transcriptome analysis revealed the active engagement of Mino@ZIF-8 nanoparticles in innate and adaptive inflammatory host defense and cellular metabolic remodeling. Through sustained release of the anti-inflammatory and antibacterial agent minocycline hydrochloride (Mino) and the generation of Zn2+ with pro-antioxidant effects during degradation, Mino@ZIF-8 nanoparticles synergistically alleviate inflammation and oxidative damage. Notably, our study focuses on the pivotal role of zinc ions in mitochondrial oxidation protection. Under lipopolysaccharide (LPS) stimulation, periodontal ligament cells undergo a metabolic shift from oxidative phosphorylation (OXPHOS) to glycolysis, leading to reduced ATP production and increased reactive oxygen species levels. However, Zn2+ effectively rebalances the glycolysis-OXPHOS imbalance, restoring cellular bioenergetics, mitigating oxidative damage, rescuing impaired mitochondria, and suppressing inflammatory cytokine production through modulation of the AKT/GSK3β/NRF2 pathway. This research not only presents a promising approach for periodontitis treatment but also offers novel therapeutic opportunities for zinc-containing materials, providing valuable insights into the design of biomaterials targeting cellular energy metabolism regulation.

Magnetic and pH dual responsive injectable magnetic zeolitic imidazole framework based colloidal gel for interventional treatment on hepatocellular carcinoma

Thermal ablation is frequently combined with systemic chemotherapy for treating hepatocellular carcinoma (HCC). However, the side effects of systemic chemotherapy on normal tissues limit its clinical application. Herein, we report a magnetic and pH dual-responsive colloidal gel assembled by doxorubicin (DOX)-loaded magnetic ZIF-8 and gelatin nanoparticles for HCC. The magnetic colloidal gel shows improved injectability and high functional particle loading, which could be injected through a 27G needle with an injection force as low as 8.8 N at 150 mg/mL solid content. Meanwhile, this colloidal gel could be magnetically heated and accelerated release DOX under tumor microenvironment, which presents a synergistic therapeutic effect by combining magnetic hyperthermia and localized chemotherapy. Furthermore, this colloidal gel could be manually injected interventional under ultrasound-guidance, exhibiting effective deep tumor treatment effect. Due to the high solid content, suitable injectability, and mechanical properties, the colloidal gel is also a promising embolic agent for transarterial embolization in HCC treatment.

Dual-Targeted Zeolitic Imidazolate Frameworks Drug Delivery System Reversing Cisplatin Resistance to Treat Resistant Ovarian Cancer.

Ovarian cancer cells are prone to acquire tolerance to chemotherapeutic agents, which seriously affects clinical outcomes. The development of novel strategies to enhance the targeting of chemotherapeutic agents to overcome drug resistance and minimize side effects is significant for improving the clinical outcomes of ovarian cancer patients. We employed folic acid (FA)-modified ZIF-90 nanomaterials (FA-ZIF-90) to deliver the chemotherapeutic drug, cisplatin (DDP), via dual targeting to improve its targeting to circumvent cisplatin resistance in ovarian cancer cells, especially by targeting mitochondria. FA-ZIF-90/DDP could rapidly release DDP in response to dual stimulation of acidity and ATP in tumor cells. FA-ZIF-90/DDP showed good blood compatibility. It was efficiently taken up by human ovarian cancer cisplatin-resistant cells A2780/DDP and aggregated in the mitochondrial region. FA-ZIF-90/DDP significantly inhibited the mitochondrial activity and metastatic ability of A2780/DDP cells. In addition, it effectively induced apoptosis in A2780/DDP cells and overcame cisplatin resistance. In vivo experiments showed that FA-ZIF-90/DDP increased the accumulation of DDP in tumor tissues and significantly inhibited tumor growth. FA-modified ZIF-90 nanocarriers can improve the tumor targeting and anti-tumor effects of chemotherapeutic drugs, reduce toxic side effects, and are expected to be a novel therapeutic strategy to reverse drug resistance in ovarian cancer.

A facile acid-etching defect-rich leaf-like zeolitic-imidazolate framework adsorbent for simultaneous removal of organic/inorganic phosphorus pollutants from wastewater

Organophosphorus herbicide glyphosate and inorganic phosphate usually coexist in wastewater, leading to water eutrophication and posing risks to human health. In this study, acid-etching defect-rich leaf-like zeolitic-imidazolate framework (ae-ZIF-L) adsorbent was developed by a facile etching method to investigate its simultaneous removal performance of glyphosate and phosphate. Compared to ZIF-L precursor, ae-ZIF-L displayed a maximum adsorption capacity for phosphate and glyphosate of 164.4mgg–1 and 12.7mgg–1, respectively. The overall enhanced adsorption performance of ae-ZIF-L was primarily attributed to abundant Zn defects, resulting in higher positive zeta potentials to enhance electrostatic attraction. Notably, in the phosphate/glyphosate coexistence system, ae-ZIF-L has extremely high removal rates of 99.1% and 90.9%, while ZIF-L has removal rates of 97.7% and 39.4%, respectively. Furthermore, after four adsorption-desorption cycles, the removal rates of phosphate/glyphosate by ae-ZIF-L remained at 84.8% and 82.5%, respectively. In conclusion, ae-ZIF-L proved to be an efficient and reusable adsorbent with promising application for the treatment of organic/inorganic phosphorus pollution in wastewater.

Synergistic Enhancement of Electron Dynamics and Optical Properties in Zeolitic Imidazolate Framework-8-Derived Zinc Oxide via Surface Plasmon Resonance Effects of Silver Nanoparticles under UV Irradiation.

This study investigates the surface plasmon resonance (SPR)-induced UV photoresponse of zinc oxide (ZnO) derived from zeolitic imidazolate framework-8 (ZIF-8) to assess the influence of silver nanoparticles (Ag NPs) on the photoresponse behavior of metal-organic framework (MOF)-derived ZnO. The initial synthesis involved a thermal treatment in air to convert ZIF-8 into ZnO. We noted enhanced optical absorption both in the UV and visible spectra with the deposition of Ag NPs onto the ZIF-8-derived ZnO. Additionally, the presence of Ag NPs in the ZnO resulted in a substantial increase in current, even without any light exposure. This increase is attributed to the transfer of electrons from the Ag NPs to the ZnO. Photocurrent measurements under UV illumination revealed that the photocurrent with Ag NPs was significantly higher-by two orders of magnitude-compared with that without Ag NPs. This demonstrates that SPR-induced absorption markedly boosted the photocurrent, although the current rise and decay time constants remained comparable to those observed with ZnO alone. Although Ag NPs contribute electrons to ZnO, creating a "pre-doping" effect that heightens baseline conductivity (even in the absence of light), this does not necessarily alter the recombination dynamics of the photogenerated carriers, as indicated by the similar rise and decay time constants. The electron transfer from Ag to ZnO increases the density of charge carriers but does not significantly influence their recombination.

Nano-enzyme hydrogels for cartilage repair effectiveness based on ternary strategy therapy.

Designing artificial nano-enzymes for scavenging reactive oxygen species (ROS) in chondrocytes (CHOs) is considered the most feasible pathway for the treatment of osteoarthritis (OA). However, the accumulation of ROS due to the amount of nano-enzymatic catalytic site exposure and insufficient oxygen supply seriously threatens the clinical application of this therapy. Although metal-organic framework (MOF) immobilization of artificial nano-enzymes to enhance active site exposure has been extensively studied, artificial nano-enzymes/MOFs for ROS scavenging in OA treatment are still lacking. In this study, a biocompatible lubricating hydrogel-loaded iron-doped zeolitic imidazolate framework-8 (Fe/ZIF-8/Gel) centrase was engineered to scavenge endogenous overexpressed ROS synergistically generating dissolved oxygen and enhancing sustained lubrication for CHOs as a ternary artificial nano-enzyme. This property enabled the nano-enzymatic hydrogels to mitigate OA hypoxia and inhibit oxidative stress damage successfully. Ternary strategy-based therapies show excellent cartilage repair in vivo. The experimental results suggest that nano-enzyme-enhanced lubricating hydrogels are a potentially effective OA treatment and a novel strategy.

Cobalt-Copper-Embedded Nitrogen-Doped Carbon Nanostructures Derived from Zeolite Imidazolate Frameworks as Electrocatalysts for the Oxygen Reduction Reaction.

In recent years, researchers have focused on developing zeolite imidazolate frameworks (ZIFs) as an alternative to Pt electrocatalysts for various applications, including water splitting, lithium-air batteries, zinc-air batteries, and fuel cells. In this study, we synthesized CoCu-ZIF to be used as a precursor in the development of cathode catalysts for the oxygen reduction reaction (ORR) in fuel cells. Hydrazine played a crucial role in maintaining uniformity in the development and particle size of the ZIF-67 structures. Moreover, it facilitated the rapid formation of the ZIF-67 structures at higher temperatures. A unique pseudorhombic dodecahedral morphology was obtained at a Co/Cu molar ratio of 7:3. Among all the synthesized N-doped carbon nanostructures embedded with Co and Cu nanoparticles, CoCu@NC-750, pyrolyzed at 750 °C, showed superior ORR catalytic performance. This catalyst exhibited a notably higher half-wave potential of 0.816 V and demonstrated a clear 4-electron transfer mechanism. The overpotential of CoCu@NC-750 shifted by only 11 mV over 10,000 cyclic voltammetry cycles, whereas a 55 mV shift was observed for Pt/C. CoCu@NC-750 exhibited a ∼0.8% decrease in current density during a 12-h ORR, in contrast to the 8.3% decline shown by Pt/C. This superior catalytic activity and stability can be attributed to factors such as higher oxygen adsorption induced by the N-doped carbon layer due to the localized changes in electron density and the enhanced stability of the bimetallic core. Our findings suggest that CoCu@NC-750 is a promising alternative to Pt/C in fuel cell cathodes.

Adsorption properties of n-octane/1-octene binary mixtures in the zeolitic imidazolate frameworks, ZIF-8 and ZIF-67: Combined experimental and molecular simulation study

1-Octene, a linear α-olefin, can be used as a comonomer for producing plastics, oils, waxes, and surfactants. High-purity 1-octene can be obtained by removing paraffin byproducts using energy-intensive distillation. Adsorptive separation using porous material–based adsorbents is a promising alternative to distillation. Most reported adsorbents are zeolites, which preferentially adsorb 1-octene rather than n-octane owing to their polar framework. However, the existing studies are insufficient for investigating apolar adsorbents that adsorb more amounts of n-octane than 1-octene. Herein, the adsorption properties of the apolar adsorbents, zeolitic imidazolate frameworks-8 (ZIF-8) and ZIF-67, obtained from a n-octane/1-octene liquid binary mixture were systematically investigated by conducting batch adsorption experiments for the n-octane volume fraction of 10 %–90 %. Results show that ZIF-8 and ZIF-67 are promising adsorbents for the selective adsorption of n-octane owing to the preferential adsorption of n-octane in the micropores of the ZIFs at the high concentration of n-octane. Configurational-bias grand canonical Monte Carlo simulations confirm that the host–adsorbate energy between ZIF-8 and n-octane is higher than that between ZIF-8 and 1-octene, whereas the host–adsorbate energy between ZIF-67 and n-octane is similar to that between ZIF-67 and 1-octene.