Synthesis of Ag-doped ZIF-8 photocatalyst with excellent performance for dye degradation and antibacterial activity

Morinda citrifolia fruit extract-mediated synthesis of ZnO and Ag/ZnO nanoparticles for photocatalytic degradation of tetracycline

Bio-mediated synthesis of zinc oxide (ZnO) nanoparticles using plant extracts has been paid attention but still remains several challenges, e.g., alkaline addition during biosynthesis and photocatalytic effectiveness. Here, ZnO and silver (Ag)-doped ZnO at different ratios (0.5%, 1%, 3%, 5%, and 7%) were synthesized by an alkali-free method using Morinda citrifolia fruit extract. These materials were used as efficient photocatalysts for the tetracycline hydrochloride degradation. The impact of factors such as synthesis condition, Ag doping, pH, concentration, catalyst dosage, coexisting ions, and different light sources on the photocatalytic performance of green ZnO and Ag/ZnO nanoparticles was studied. The Ag-1%/ZnO composite exhibited the highest photocatalytic activity. The chief mechanisms involved in the photocatalytic process of Ag-doped ZnO nanoparticles were insightfully clarified through electrochemical and scavenging analyses. Active species including •O2-, h+, and e- played a vital role in the tetracycline hydrochloride degradation mechanism. Moreover, Ag-1%/ZnO represented four cycles with a minor decrease in degradation efficiency from 84% to 79% from the 1st to the 4th cycle. Morinda citrifolia fruit extract-mediated Ag/ZnO nanoparticles is suggested as an effective and recyclable photocatalyst in the tetracycline antibiotic treatment.

Unleashing the antibacterial potential of ZIFs and their derivatives: mechanistic insights

Antibiotic resistance presents an alarming threat to global health, with bacterial infections now ranking among the leading causes of mortality. To address this escalating challenge, strategies such as antibiotic stewardship, development of antimicrobial therapies, and exploration of alternative treatment modalities are imperative. Metal-organic frameworks (MOFs), acclaimed for their outstanding biocompatibility and in vivo biodegradability, are promising avenues for the synthesis of novel antibiotic agents under mild conditions. Among these, zeolitic imidazolate frameworks (ZIFs), a remarkable subclass of MOFs, have emerged as potent antibacterial materials; the efficacy of which stems from their porous structure, metal ion content, and tunable functionalized groups. This could be further enhanced by incorporating or encapsulating metal ions, such as Cu, Fe, Ti, Ag, and others. This perspective aims to underscore the potential of ZIFs as antibacterial agents and their underlying mechanisms including the release of metal ions, generation of reactive oxygen species (ROS), disruption of bacterial cell walls, and synergistic interactions with other antibacterial agents. These attributes position ZIFs as promising candidates for advanced applications in combating bacterial infections. Furthermore, we propose a novel approach for synthesizing ZIFs and their derivatives, demonstrating exceptional antibacterial efficacy against Escherichia coli and Staphylococcus aureus. By highlighting the benefits of ZIFs and their derivatives as antibacterial agents, this perspective emphasizes their potential to address the critical challenge of antibiotic resistance.

ZIF-8 metal-organic frameworks and their hybrid materials: emerging photocatalysts for energy and environmental applications

In the face of escalating environmental challenges such as fossil fuel dependence and water pollution, innovative solutions are essential for sustainable development. In this regard, zeolitic imidazolate frameworks (ZIFs), specifically ZIF-8, act as promising photocatalysts for environmental remediation and renewable energy applications. ZIF-8, a subclass of metal-organic frameworks (MOFs), is renowned for its large specific surface area, high porosity, rapid electron transfer ability, abundant functionalities, ease of designing, controllable properties, and remarkable chemical and thermal stability. However, its application as a standalone photocatalyst is limited by issues such as particle aggregation, poor water stability, and insufficient visible light absorption. By integrating ZIF-8 with various photoactive materials to form composite catalysts, these drawbacks can be mitigated, leading to enhanced photocatalytic efficiency. The review discusses the synthesis, properties, and applications of ZIF-8-based photocatalysts in light-driven H2 evolution, H2O2 evolution, CO2 reduction, and dye and drug degradation. It also highlights the challenges and future research directions in developing cost-effective, scalable, and environmentally friendly ZIF-8 composites for industrial applications. The potential of ZIF-8 composites to contribute to sustainable global energy solutions and environmental cleanup is significant, yet further exploration is required to harness their capabilities thoroughly.

Construction of a hydrazine electrochemical sensor using Ag@ZIF as the electrode material

In recent years, the fabrication of hydrazine sensors has received extensive attention because of the toxicity of hydrazine to the environment and human beings. It is thus important to design and develop efficient electrode modifiers for the construction of hydrazine electrochemical sensors. Herein, we reported the benign synthesis of a silver (Ag)-doped zinc-based zeolitic imidazolate framework (ZIF-8). The synthesized Ag@ZIF-8 was characterized by various advanced physiochemical characterization methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). A screen-printed electrode (SPE) was modified with the prepared Ag@ZIF-8. The cyclic voltammetry (CV) and linear sweep voltammetry (LSV) methods were used for assessing its sensing towards hydrazine. The obtained results showed a reasonable detection limit (0.1 μM), sensitivity (1.98 μA μM cm-2), stability, selectivity, and repeatability using Ag@ZIF-8/SPE as a hydrazine sensor. The real-sample investigations demonstrated recovery rates of 96-97%.

Silver single atoms and nanoparticles on floatable monolithic photocatalysts for synergistic solar water disinfection

Photocatalytic water disinfection technology is highly promising in off-grid areas due to abundant year-round solar irradiance. However, the practical use of powdered photocatalysts is impeded by limited recovery and inefficient inactivation of stress-resistant bacteria in oligotrophic surface water. Here we prepare a floatable monolithic photocatalyst with ZIF-8-NH2 loaded Ag single atoms and nanoparticles (AgSA+NP/ZIF). Atomically dispersed Ag sites form an Ag-N charge bridge, extending the lifetime of charge carriers and thereby promoting reactive oxygen species (ROS) generation. The photothermal effect of the plasmonic Ag nanoparticles reduces the bacterial resistance to ROS and impairs DNA repair capabilities. Under sunlight irradiation, the synergistic effect of Ag single atoms and nanoparticles enables 4.0 cm2 AgSA+NP/ZIF to achieve over 6.0 log inactivation (99.9999%) for the stress-resistant Escherichia coli (E. coli) in oligotrophic surface water within 30 min. Furthermore, 36 cm2 AgSA+NP/ZIF is capable of disinfecting at least 10.0 L of surface water, which meets the World Health Organization (WHO) recommended daily per capita drinking water allocation (8.0 L). This study presents a decentralized and sustainable approach for water disinfection in off-grid areas.

Studying the properties of green synthesized silver oxide nanoparticles in the application of organic dye degradation under visible light

In present study the green synthesis of silver oxide nanoparticles has been effectively achieved using novel plant extract Phragmanthera Macrosolen. This method provides sustainable alternative for nanoparticle synthesis, demonstrating the potential of Phragmanthera Macrosolen as a reducing and stabilizing agent in the production of Ag2O NPs. The synthesized nanoparticles were characterized for their structural, morphological, and optical properties, confirming their successful formation and potential applications in various fields. The effects of different pH values and annealing temperature of the samples on the properties of Ag2O NPs formations, as well as photo-catalytic activities towards Toluidine Blue dye degradations, were studied. Powder XRD reveals that the crystallite natures of Ag2O NPs a long with crystalline size ranges from 25.85 to 35.90 nm. FIB-SEM and HR-TEM images displayed that the Ag2O NPs as spherical shapes. UV-vis spectroscopy displayed that Ag2O NPs belong to a direct-band gap of 2.1-2.6 eV. FTIR- study shown that the green synthesized Ag2O NPs may be steadied via the interfaces of -OH as well as C = O groups in the carbohydrate, flavonoid, tannin, as well as phenolic acid existing in P. macrosolen L. leaf. The chemical states, electron-hole recombinations and purity of Ag and O in the synthesized Ag2O NPs were confirmed through X-ray Photoelectron Spectroscopy (XPS) and PL analysis respectively. Fascinatingly, the synthesized Ag2O NPs at pH 12 displayed high photo-catalytic degradations for TB dyes. The photo-catalytic degradations of the TB dyes were monitored spectro-photo-metrically in wave-length ranges of 200-900 nm, as well as high efficiency (98.50%) with half-life of 9.5798 min and kinetic rate constant of 0.07234 min-1, was obtained after 45 min of reactions. From this study, it can be concluded that Ag2O NPs synthesized from Phragmanthera Macrosolen aqueous extract are promising in the remediation of environmental pollution and water treatment. In this light, the study reports that Phragmanthera Macrosolen green synthesis of Ag2O NPs can effectively address environmental pollution in cost-effective, eco-friendly, and sustainable ways.

Green synthesis of manganese ferrite magnetic nanoparticle and its modification with metallic-organic frameworks for the tetracycline adsorption from aqueous solutions: A mathematical study of kinetics, isotherms, and thermodynamics

In the current investigation, MnFe2O4/ZIF-8 nanocomposite was generated as a magnetic nanoadsorber using the extract of Dracocephalum plant and characterized by XRD, FTIR, VSM, BET, FESEM, EDS-mapping, TEM, XPS, TPD-NH3, and TGA analyses. Also, to determine its efficiency in the adsorption process of tetracycline, the effect of pH (3-9), nanocomposite dose (0.025-2 g/L), initial pollutant concentration (5-100 mg/L), contact time (5-200 min), and temperature (5-50 °C) were studied. The results of the morphological properties of the magnetic nanocomposite confirmed the spherical shape of this nanoadsorber with an average size of 54 ± 31 nm. BET analysis showed that modification of MnFe2O4 material with ZIF-8 as a new nanoadsorber leads to excellent modification of SBET (143.8 m2/g) and VTotal (0.44 cm3/g). The highest removal efficiency of tetracycline in optimal conditions (pH = 7, contact time = 120 min, nanocomposite dose = 1.5 g/L, and temperature = 20 °C for a tetracycline concentration of 20 mg/L) was 90.11%. As the temperature increased, the removal efficiency increased from 40.46% to 95.06% during 120 min, which indicates that the adsorption reaction is endothermic. In addition, the data obtained from the isotherms of Langmuir (R2 = 0.958), Freundlich (R2 = 0.534), and Temkin (R2 = 0.747) showed that the tetracycline adsorption is monolayer and on the homogeneous surface of the synthesized magnetic nanoadsorber. The elimination process of tetracycline by nanoadsorber followed the pseudo-second order model (R2 = 0.998). Investigating the effect of interfering ions also confirmed the decrease in the adsorption efficiency. Also, the investigation of the reusability of the synthesized magnetic nanoadsorber in tetracycline adsorption indicates that after eight cycles, the efficiency decreases by %16.51. According to the results, the magnetic nanocomposite synthesized in this work can be a suitable and economical adsorber for the removal of tetracycline from aqueous environments.

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.

Synthesis of magnetic layered double hydroxide (Fe3O4@CuCr-LDH) decorated with ZIF-8 for efficient sonocatalytic degradation of tetracycline

A series of Fe3O4@CuCr-LDH hybrids decorated with different amount of ZIF-8 (FLZ, 10-40 wt%) was prepared using simple methods and characterized with different techniques. The activity of the synthesized nanocomposites was investigated in the sonocatalytic degradation of tetracycline (TC) antibiotic from wastewater. When the content of ZIF-8 in the nanocomposite structure was 20 wt%, the FLZ-20 sonocatalyst exhibited the high performance in the sonocatalytic removal of TC. At optimum conditions (0.7 g/L catalyst dosage, pH of 7, 50 mg/L initial concentration of antibiotic, and 15 min sonication time) of the sonocatalytic removal of TC approached to 91.4% under ultrasonic irradiation (USI) using FLZ-20. This efficiency was much higher than those of obtained results by Fe3O4@CuCr-LDH and pristine ZIF-8. The formed ●OH and ●O2- exhibited the major roles in the sonocatalytic TC degradation process. The excellent performance of FLZ-20 can be attributed to the heterojunctions created between composite components, which could improve the electron transfer ability and effectively separate e-/h+ pairs. In addition, FLZ-20 showed the superior reusability and stability during three successive recycling. Moreover, the facile magnetically separation of the sonocatalyst from the aqueous solution was another outstanding feature, which prevents the formation of secondary pollutants. It can be concluded that the fabrication of heterojunctions is an efficient procedure to promote the sonocatalytic acting of the catalyst.

Synthesis of Metal-Organic Framework-Based ZIF-8@ZIF-67 Nanocomposites for Antibiotic Decomposition and Antibacterial Activities

Toxic antibiotic effluents and antibiotic-resistant bacteria constitute a threat to global health. So, scientists are investigating high-performance materials for antibiotic decomposition and antibacterial activities. In this novel research work, we have successfully designed ZIF-8@ZIF-67 nanocomposites via sol-gel and solvothermal approaches. The ZIF-8@ZIF-67 nanocomposite is characterized by various techniques that exhibit superior surface area enhancement, charge separation, and high light absorption performance. Yet, ZIF-8 has high adsorption rates and active sites, while ZIF-67 has larger pore volume and efficient adsorption and reaction capabilities, demonstrating that the ZIF-8@ZIF-67 nanocomposite outperforms pristine ZIF-8 and ZIF-67. Compared with pristine ZIF-8 and ZIF-67, the most active 6ZIF-67@ZIF-8 nanocomposite showed higher decomposition efficacy for ciprofloxacin (65%), levofloxacin (54%), and ofloxacin (48%). Scavenger experiments confirmed that •OH, •O2-, and h+ are the most active species for the decomposition of ciprofloxacin (CIP), levofloxacin (LF), and ofloxacin (OFX), respectively. In addition, the 6ZIF-67/ZIF-8 nanocomposite suggested its potential applications in Escherichia coli for growth inhibition zone, antibacterial activity, and decreased viability. Moreover, the stability test and decomposition pathway of CIP, LF, and OFX were also proposed. Finally, our study aims to enhance the efficiency and stability of ZIF-8@ZIF-67 nanocomposite and potentially enable its applications in antibiotic decomposition, antibacterial activities, and environmental remediation.

Enhanced Iodine Capture Using a Postsynthetically Modified Thione-Silver Zeolitic Imidazole Framework

Efficient management of radionuclides that are released from various processes in the nuclear fuel cycle is of significant importance. Among these nuclides, radioactive iodine (mainly 129I and 131I) is a major concern due to the risk it poses to the environment and to human health; thus, the development of materials that can capture and safely store radioactive iodine is crucial. Herein, a novel silver-thione-functionalized zeolitic imidazole framework (ZIF) was synthesized via postsynthetic modification and assessed for its iodine uptake capabilities alongside the parent ZIF-8 and intermediate materials. A solvent-assisted ligand exchange procedure was used to replace the 2-methylimidazole linkers in ZIF-8 with 2-mercaptoimidazole, forming intermediate compound ZIF-8 = S, which was reacted with AgNO3 to yield the ZIF-8 = S-Ag+ composite for iodine uptake. Despite possessing the lowest BET surface area of the derivatives, the Ag-functionalized material demonstrated superior I2 adsorption in terms of both maximum capacity (550 g I2/mol) and rapid kinetics (50% loading achieved in 5 h, saturation in 50 h) compared to that of our pristine ZIF-8, which reached 450 g I2/mol after 150 h and 50% loading in 25 h. This improvement is attributed to the presence of the Ag+ ions, which provide a strong chemical driving force to form a stable Ag-I species. The results of this study contribute to a broader understanding of the strategies that can be employed to engineer adsorbents with robust iodine uptake behavior.

Facile fabrication of plasmonic Ag/ZIF-8: an efficient catalyst for investigation of antibacterial, haemolytic and photocatalytic degradation of antibiotics

Present article represents the fabrication of plasmonic Ag/ZIF-8 composite and its effect on antibacterial, haemolytic and photocatalytic degradation of antibiotics. Ag/ZIF-8 was prepared by varying molar concentrations (1 mM, 2.5 mM, and 5 mM) of AgNO3 into ZIF-8 using NaBH4 as a reducing agent by the sol-gel process. The material was then characterised using the XRD, XPS, FTIR, SEM, HRTEM, UVDRS, BET and EIS techniques. When it comes to breaking down the antibiotic CIP, the optimised Ag2.5/ZIF-8 exhibits the strongest photocatalytic capability, with a degradation efficiency of 82.3% after 90 minutes. Due to LSPR (Localised Surface Plasmon Resonance) as well as the efficient movement and separation of the interfaces of photo-generated charge carriers in Ag2.5/ZIF-8 may be the causes of this increase in photocatalytic degradation. The effect of several parameters, such as pH, a variety of catalysts, varying dose concentrations, scavenging and sustainability are being investigated. The para benzoquinone (OH˙) and citric acid (h+) the primary active species in the photocatalytic breakdown pathway, according to trapping study. Whereas, Ag5/ZIF-8 was optimised for greater antibacterial activity against S. aureus and E. coli due to the synergistic impact of Ag+ and Zn2+ in Ag5/ZIF-8 and in haemolytic experiment, all samples were discovered to be non-toxic to blood cells. Overall, the synthesised compound was discovered to be a reusable, affordable catalyst for water remediation that can also be used in biomedicine.

Synthesis and antibacterial activities of Ag-TiO2/ZIF-8

In recent years, massive bacterial infections have led to human illness and death, reminding us of the urgent need to develop effective and long-lasting antimicrobial materials. In this paper, Ag-TiO2/ZIF-8 with good environmental friendliness and biological antibacterial activity was prepared by solvothermal method. The structure and morphology of the synthesized materials were characterized by XRD, FT-IR, SEM-EDS, TEM, XPS, and BET. To investigate the antibacterial activity of the synthesized samples, Escherichia coli and Bacillus subtilis were used as target bacteria for experimental studies of zone of inhibition, bacterial growth curves, minimum bactericidal concentration and antibacterial durability. The results demonstrated that 20 wt.%Ag-TiO2/ZIF-8 had the best bacteriostatic effect on E. coli and B. subtilis under dark and UV conditions compared to TiO2 and ZIF-8. Under the same conditions, the diameter of the inhibition circle of 20 wt% Ag-TiO2/ZIF-8 is 8.5-11.5 mm larger than that of its constituent material 4 wt% Ag-TiO2, with more obvious antibacterial effect and better antibacterial performance. It is also proposed that the excellent antibacterial activity of Ag-TiO2/ZIF-8 is due to the synergistic effect of Ag-TiO2 and ZIF-8 under UV light. In addition, the prepared material has good stability and durability with effective antimicrobial activity for more than 5 months.

A green and facile one-step hydration method based on ZIF-8-PDA to prepare melamine composite sponges with excellent hydrophobicity for oil-water separation

Frequent crude oil spills and illegal discharges of industrial organic pollutants cause serious damage to the ecological environment and considerable loss of valuable resources. Therefore, there is an urgent need to develop efficient strategies to separate and recover oils or reagents from sewage. Herein, a green, facile and rapid one-step hydration method was applied to obtain the composite sponge (ZIF-8-PDA@MS) that monodispersed zeolitic imidazolate framework-8 nanoparticles with high porosity and large specific surface area were firmly loaded onto the melamine sponge by ligand exchange and the self-assembly of dopamine. The water contact angle of ZIF-8-PDA@MS with multiscale hierarchical porous structure could reach 162°, which remained stable over a long period of time and a wide pH range. ZIF-8-PDA@MS displayed excellent adsorption capacities (up to 85.45-168.95 g⋅g^-1), and could be reused at least 40 times. Besides, ZIF-8-PDA@MS exhibited remarkable photothermal effect. Simultaneously, Silver nanoparticle-immobilized composite sponges were also prepared via in-situ reduction of silver ions to inhibit bacterial contamination. The composite sponge developed in this work can be used not only for the treatment of industrial sewage, but also for the emergency response of large-scale marine oil spill accidents, which has inestimable practical value for water decontamination.

Electrodeposition of Ag/ZIF-8-Modified Membrane for Water Remediation

Metal-organic framework (MOF)-based membranes have been widely used in gas and liquid separation due to their porous structures and tunable compositions. Depending on the guest components, heterostructured MOFs can exhibit multiple functions. In the present work, we report a facile and rapid preparation of zeolitic imidazolate framework-8 (ZIF-8) and silver nanoparticle incorporated ZIF-8 (Ag/ZIF-8)-based membranes on stainless-steel mesh (SSM) through a "green" electrodeposition method. The SSM was first coated with a Zn-plated layer which contains mainly zinc hydroxide nitrate (Zn₅(OH)₈(NO₃)₂·2H₂O) with a "leaf-like" morphology, providing anchoring points for the deposition of ZIF-8 and Ag/ZIF-8. It takes only 10 min to prepare a uniform coating of Zn₅(OH)₈(NO₃)₂·2H₂O in aqueous conditions without the use of a strong base; this is by far the most efficient way of making zinc hydroxide nitrate nanocrystals. Following a similar electrodeposition approach, ZIF-8 and Ag/ZIF-8-coated SSM can be prepared within 20 min by applying a small current. The encapsulation of Ag does not alter the chemical composition nor the crystal structure of ZIF-8. The resulting ZIF-8 and Ag/ZIF-8-coated SSM have been tested for their effectiveness for rhodamine B dye removal in a fast vacuum filtration setting. Additionally, growth of E. coli was significantly inhibited after overnight incubation with Ag/ZIF-8-coated SSM. Overall, we demonstrate a fast synthesis procedure to make ZIF-8 and Ag/ZIF-8-coated SSM membranes for organic dye removal with excellent antimicrobial activity.

The application of a new recyclable photocatalyst γ-Fe2O3@SiO2@ZIF8-Ag in the photocatalytic degradation of amoxicillin in aqueous solutions

This pilot study synthesized the γ-Fe₂O₃@SiO₂@ZIF8-Ag nanocomposites via the hydrothermal method to study its potential use in amoxicillin degradation as a novel photocatalyst in aqueous solutions under visible light radiation. Various diagnostic methods were used to determine the morphology and functional structure of the photocatalyst, and the results confirmed its proper formation. Complete degradation of AMX was obtained at a pH of 5, catalyst dosage of 0.4 g/L, AMX concentration of 10 mg/L, and reaction time of 60 min. The efficiency of the degradation was diminished when anions were present in the reaction medium, and the order of their effect was SO₄^2- < Cl^- < NO₃^- < HCO₃^-. Biodegradability (BOD₅/COD ratio) increased from 0.20 to 0.68 after 120 min of photocatalytic treatment, with a COD removal of 87.54% and a TOC removal of 74.88%. Through the experimental trapping of electrons, we found the production of reactive species, such as hydroxyl radical (•OH), superoxide (O₂^•-), and holes (h⁺), in the photocatalysis reactor and that •OH was the predominant species in AMX photodegradation. Comparative experiments emphasized that the oxidation process occurs with the adsorption of pollutants on the surface of the catalyst, and the photocatalyst has the potential to be activated by various light sources, including visible light, UV light, and sunlight, with an AMX decomposition above 88%. The synthesized particles can be recovered after five consecutive cycles with minimal reduction in the degradation rate (< 4%). γ-Fe₂O₃@SiO₂@ZIF8-Ag can be considered a promising photocatalyst for use in AMX degradation due to its recyclability, easier activation by different light sources, and excellent mineralization.

ZIF-8 metal organic framework composites as hydrogen evolution reaction photocatalyst: A review of the current state

In the past decade, extensive research has been devoted to synthesis of ZIF-8 materials for catalytic applications. As physico-chemical properties are synthesis-dependent, this review explores different synthesis strategies based the solvent and solvent-free synthesis of zeolitic imidazole framework. Accordingly, the effect of several parameters on the ZIF-8 synthesis were discussed including solvent, deprotonating agents, precursors ratio is delivered. Additionally, the advantages and disadvantages of each synthesis have been discussed and assessed. ZIF-8 textural and structural properties justify its wide use as a stable high surface area MOF in aqueous catalytic reactions. This review includes the applicatios of ZIF-8 materials in photocatalytic hydrogen evolution reaction (HER). The efficiency of the reviewed materials was fairly assessed. Finally, Limitations, drawbacks and future challenges were fully debated to ensure the industrial viability of the ZIFs.

Cation Incorporation and Synergistic Effects on the Characteristics of Sulfur-Doped Manganese Ferrites S@Mn(Fe2O4) Nanoparticles for Boosted Sunlight-Driven Photocatalysis

In the present work, sulfur-doped manganese ferrites S@Mn(Fe₂O₄) nanoparticles were prepared by using the sol-gel and citrate method. The concentration of sulfur varied from 1 to 7% by adding Na₂S. The samples were characterized by performing Fourier Transformed Infrared Spectroscopy (FTIR), Energy Dispersive X-ray (EDX), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Ultraviolet-Visible spectroscopy (UV-Visible). The synthesized sulfur-doped manganese ferrites were applied to evaluate the photocatalytic degradation of the dyes. Further, the degradation studies revealed that the nanoparticles successfully degraded the methylene blue dye by adding a 0.006 g dose under the sunlight. The sulfur-doped manganese ferrite nanoparticles containing 3% sulfur completely degraded the dye in 2 h and 15 min in aqueous medium. Thus, the ferrite nanoparticles were found to be promising photocatalyst materials and could be employed for the degradation of other dyes in the future.

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.

State-of-the-art progress of metal-organic framework-based electrochemical and optical sensing platforms for determination of bisphenol A as an endocrine disruptor

Considering the low concentration levels of bisphenol compounds present in environmental, food, and biological samples, and the difficulty in analyzing the matrices, the main challenge is with the cleanup and extraction process, as well as developing highly sensitive determination methods. Recent advances in the field of metal-organic frameworks (MOFs) due to their large surface area, low weight, and other extraordinary physical, chemical, and mechanical features have made these porous materials a crucial agent in developing biosensing assays. This review focuses on MOFs across their definition, structural features, various types, synthetic routes, and their significant utilization in sensing assays for bisphenol A (BPA) determination. Additionally, recent improvements in characteristics and physio-chemical features of MOFs and their functional applications in developing electrochemical and optical sensing assays via different recognition elements for detecting BPA are comprehensively discussed. Finally, the existing boundaries of the current advances including future challenges concerning successful construction of sensing approaches by employing functionalized MOFs are addressed.

Improvement of anti-corrosion performance of an epoxy coating using hybrid UiO-66-NH2/carbon nanotubes nanocomposite

In this study, a porous nanocontainer from UiO-66-NH₂/CNTs nanocomposite with an excellent barrier characteristics was constructed through amine-functionalized Zr-based metal organic framework. The characterization of the prepared nano-materials were performed using different analyses such as FTIR, XRD, SEM, EDS, TEM, and BET and the results proved the successful synthesize of UiO-66-NH₂/CNTs nanocomposite. The corrosion protection performance of the coated panels was investigated by electrochemical impedance spectroscopy (EIS), salt spray, and contact angle measurement. The EIS results revealed that unmodified and UiO-66-NH₂ containing coating in 3.5 wt.% NaCl electrolyte were failed after 45 days but the corrosion was negligible in UiO-66-NH₂/CNTs coating due to high pore resistance values even after 45 days. Salt spray and contact angle measurements confirmed that UiO-66-NH₂/CNTs containing coating acts as an efficient barrier against wet saline environment even at long exposure times. This is attributed to uniform dispersion in the epoxy matrix and formation of a uniform nanocomposite coating.

Novel MOF-Based Photocatalyst AgBr/AgCl@ZIF-8 with Enhanced Photocatalytic Degradation and Antibacterial Properties

A novel visible light-driven AgBr/AgCl@ZIF-8 catalyst was synthesized by a simple and rapid method. The composition and structure of the photocatalyst were characterized by XRD, SEM, UV-DRS, and XPS. It could be observed that the 2-methylimidazole zinc salt (ZIF-8) exhibited the rhombic dodecahedron morphology with the AgCl and AgBr particles evenly distributed around it. The composite photocatalyst AgBr/AgCl@ZIF-8 showed good photocatalytic degradation and antibacterial properties. The degradation rate of RhB solution was 98%, with 60 min of irradiation of visible light, and almost all P. aeruginosaudomonas aeruginosa (P. aeruginosa), Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli) were inactivated under the irradiation of 90 min. In addition, the prepared catalyst had excellent stability and reusability. Based on the free radical capture experiment, ·O₂⁻ and h⁺ were believed to be the main active substances, and possible photocatalytic degradation and sterilization mechanisms of AgBr/AgCl@ZIF-8 were proposed.

Novel 3D cross-shaped Zn/Co bimetallic zeolite imidazolate frameworks for simultaneous removal Cr(VI) and Congo Red

The photocatalytic properties of Zn/Co zeolite imidazolate frameworks (ZIF-ZnCo) prepared by various Zn/Co ratio are of significantly diversity due to the morphology structure of the ZIF-ZnCo. Thereinto, the prepared ZIF-ZnCO-8:1 is excellent capability by virtue of its 3D cross-shaped structure. Spectral test results show that as-prepared novel 3D cross-shaped ZIF-ZnCo has a lower recombination rate of electron and hole pairs than the lamellar and dodecahedral, thus improving the photocatalytic ability. The photocatalytic ability of 3D cross-shaped ZIF-ZnCo was carefully investigated for removing mixed solution of Congo Red (CR) and Cr(VI). The photocatalytic reduction ability of 3D cross-shaped ZIF-ZnCo was 22% higher than ZIF-8 for Cr(VI). Meanwhile, CR was altogether removed at dark processing and Cr(VI) was removed 70% after dark processing 120 min and photocatalytic 240 min. Therefore, the high adsorption and photocatalytic capacity denote the potential application of 3D cross-shaped ZIF-ZnCo.

State of the art on the ultrasonic-assisted removal of environmental pollutants using metal-organic frameworks

The environmental and health issues of drinking water and effluents released into nature are among the major area of contention in the past few decades. With the growth of ultrasound-based approaches in water and wastewater treatment, promising materials have also been considered to employ their advantages. Metal-organic frameworks (MOFs) are among the porous materials that have received great attention from researchers in recent years. Features such as high porosity, large specific surface area, electronic properties like semi-conductivity, and the capacity to coordinate with the organic matter have resulted in a substantial increase in scientific researches. This work deals with a comprehensive review of the application of MOFs for ultrasonic-assisted pollutant removal from wastewater. In this regard, after considering features and synthesis methods of MOFs, the mechanisms of several ultrasound-based approaches including sonocatalysis, sonophotocatalysis, and sono-adsorption are well assessed for removal of different organic compounds by MOFs. These methods are compared with some other water treatment processes with the application of MOFs in the absence of ultrasound. Also, the main concern about MOFs including environmental hazards and water stability is fully discussed and some techniques are proposed to reduce hazardous effects of MOFs and improve stability in humid/aqueous environments. Economic aspects for the preparation of MOFs are evaluated and cost estimates for ultrasonic-assisted AOP approaches were provided. Finally, the future outlooks and the new frontiers of ultrasonic-assisted methods with the help of MOFs in global environmental pollutant removal are presented.

Magnetic γ-Fe2O3/ZIF-7 Composite Particles and Their Application for Oily Water Treatment

Crude oil spills are about global challenges because of their destructive effects on aquatic life and the environment. The conventional technologies for cleaning crude oil spills need to study the selective separation of pollutants. The combination of magnetic materials and porous structures has been of considerable interest in separation studies. Here, γ-Fe₂O₃/ZIF-7 structures were prepared by growing a ZIF-7 layer onto supermagnetic γ-Fe₂O₃ nanoparticles with an average size of 18 ± 0.9 nm in situ without surface modification at low temperatures. The product composite particles were characterized using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, vibrating sample magnetometry, and N₂ adsorption/desorption isotherms. The analyses revealed a time growth-dependent ZIF-7 rod thickness with abundant nanocavities. The γ-Fe₂O₃/ZIF-7 surface area available for sorption (647 m²/g) is ∼12-fold higher than that of the γ-Fe₂O₃ nanoparticles. Moreover, the crystal structure of γ-Fe₂O₃ remained essentially unchanged following ZIF-7 coating, whereas the superparamagnetism declined depending on the coating time. The γ-Fe₂O₃/ZIF-7 particles were highly hydrophobic and selectively and rapidly (<5 min) sorbed crude oil and other hydrocarbon pollutants from water. As high as 6 g/g of the hydrocarbon was sorbed by the γ-Fe₂O₃/ZIF-7 particles immersed into the hydrocarbon. A coefficient of determination, R ₂ ², consistently >0.96 at all pollutant concentrations suggested a pseudo-second-order sorption kinetics. The thermal stability and 15 cycles of use and reuse confirmed a robust γ-Fe₂O₃/ZIF-7 sorbent.

Embedding an extraordinary amount of gemifloxacin antibiotic in ZIF-8 framework with one-step synthesis and measurement of its H2O2-sensitive release and potency against infectious bacteria

GEM@ZIF-8 has DLC = 69.82% and DLE = 89.03%, with controlled release dependent on H2O2 concentration, and it shows significant antibacterial activity.

Facile and single-step entrapment of chloramphenicol in ZIF-8 and evaluation of its performance in killing infectious bacteria with high loading content and controlled release of the drug

CLN@ZIF-8 was prepared by trapping chloramphenicol during ZIF-8 synthesis with high DLC and DLE. It showed H2O2-sensitive controlled release with higher drug release under the simulated infectious conditions and short-time antibacterial activity.

Metal–organic-framework-based photocatalysts for microorganism inactivation: a review

A metal–organic framework (MOF) is a porous coordination material composed of multidentate organic ligands and metal ions or metal clusters.

Phosphate group functionalized magnetic metal-organic framework nanocomposite for highly efficient removal of U(VI) from aqueous solution

The phosphate group functionalized metal-organic frameworks (MOFs) as the adsorbent for removal of U(VI) from aqueous solution still suffer from low adsorption efficiency, due to the low grafting rate of groups into the skeleton structure. Herein, a novel phosphate group functionalized metal-organic framework nanoparticles (denoted as Fe₃O₄@SiO₂@UiO-66-TPP NPs) designed and prepared by the chelation between Zr and phytic acid, showing fast adsorption rate and outstanding selectivity in aqueous media including 10 coexisting ions. The Fe₃O₄@SiO₂@UiO-66-TPP was properly characterized by TEM, FT-IR, BET, VSM and Zeta potential measurement. The removal performance of Fe₃O₄@SiO₂@UiO-66-TPP for U(VI) was investigated systematically using batch experiments under different conditions, including solution pH, incubation time, temperature and initial U(VI) concentration. The adsorption kinetics, isotherm, selectivity studies revealed that Fe₃O₄@SiO₂@UiO-66-TPP NPs possess fast adsorption rates (approximately 15 min to reach equilibrium), high adsorption capacities (307.8 mg/g) and outstanding selectivity (S_u = 94.4%) towards U(VI), which in terms of performance are much better than most of the other magnetic adsorbents. Furthermore, the adsorbent could be reused for U(VI) removal without obvious loss of adsorption capacity after five consecutive cycles. The research work provides a novel strategy to assemble phosphate group-functionalized MOFs.

Metal Exchange of ZIF-8 and ZIF-67 Nanoparticles with Fe(II) for Enhanced Photocatalytic Performance

Zeolitic imidazolate frameworks (ZIFs), such as ZIF-8 and ZIF-67, were found to be efficient catalysts. However, ZIFs are not used much in photocatalysis due to their low photocatalytic activity for most reactions. The photocatalytic activity can be improved by modifying the framework by exchanging the Zn(II) ions (ZIF-8) and Co(II) ions (ZIF-67) with a more photocatalytically active metal(II) ion to form an efficient bimetallic ZIF photocatalyst. Redox-active iron (Fe)-based materials are known to be highly potent photocatalysts. Thus, incorporating iron into ZIFs could significantly enhance their photocatalytic performance. In this study, we modified nanosized ZIF-8(Zn) and ZIF-67(Co) via metal (Fe²⁺) exchange to produce bimetallic frameworks that are photocatalytically more active than their parent ZIFs. Nanosized ZIF-8 and ZIF-67 were synthesized isothermally in either water or methanol under ambient conditions. From these, Fe-containing bimetallic ZIF-8 and ZIF-67 nanoparticles were synthesized via the metal exchange, and their performance on the photocatalytic degradation of dye was evaluated. The morphology and crystal structures of the pristine ZIF-8 and ZIF-67 nanoparticles were retained to a large extent during the iron exchange. Their Brunauer-Emmett-Teller (BET) surface areas decreased by less than 15% for nZIF-8 and less than 12% for nZIF-67. The binding energy values on X-ray photoelectron spectroscopy (XPS) confirmed the preservation of the oxidation state of Fe(II) during the exchange process. A remarkably higher catalytic activity was observed for the photocatalytic degradation of dye by the Fe-exchanged nZIF-8 and nZIF-67 compared to their parent ZIFs. This proved that the incorporation of Fe(II) centers into the ZIF framework enhanced the photocatalytic activity of the framework dramatically. In addition, these catalysts can be regenerated and reused without an appreciable loss in activity.

Electrocatalytic degradation of diuron herbicide using three-dimensional carbon felt/β-PbO2 anode as a highly porous electrode: Influencing factors and degradation mechanisms

Traditional planar PbO₂ anodes have been used extensively for the electrocatalytic degradation process. However, by using porous PbO₂ anodes that have a three-dimensional architecture, the efficiency of the process can be significantly upgraded. In the current study, carbon felt (CF) with a highly porous structure and a conventional planar graphite sheet (G) were used as electrode substrate for PbO₂ anodes. Both CF/β-PbO₂ and G/β-PbO₂ anodes were prepared by the anodic deposition method. The main properties of the electrodes were characterized by XRD, EDX-mapping, FESEM, and BET-BJH techniques. The electrocatalytic degradation of diuron using three-dimensional porous CF/β-PbO₂ anode was modeled and optimized by a rotatable central composite design. After optimizing the process, the ability of porous CF/β-PbO₂ and planar G/β-PbO₂ anodes to degrade and mineralize diuron was compared. The electrocatalytic degradation of the diuron was well described by a quadratic model (R² > 0.99). Under optimal conditions, the kinetics of diuron removal using CF/β-PbO₂ anode was 3 times faster than the G/β-PbO₂ anode. The energy consumed for the complete mineralization of diuron using CF/β-PbO₂ anode was 2077 kWh kg^-1 TOC. However, the G/β-PbO₂ anode removed only 65% of the TOC by consuming 54% more energy. The CF/β-PbO₂ had more stability (115 vs. 91 h), larger surface area (1.6287 vs. 0.8565 m² g^-1), and higher oxygen evolution potential (1.89 vs. 1.84 V) compared to the G/β-PbO₂. In the proposed pathways for diuron degradation, the aromatic ring and groups of carbonyl, dimethyl urea, and amide were the main targets for HO^• radical attacks.

In situ preparation of porous metal-organic frameworks ZIF-8@Ag on poly-ether-ether-ketone with synergistic antibacterial activity

Poly-ether-ether-ketone (PEEK) is a promising material in oral repair and orthopedic implantation field due to its stability and proper elastic modulus. However, the lack of simple but effective strategy to functionalize PEEK and improve its antibacterial function hinders its further biomedical application. In this study, a sulfonated 3D porous PEEK is fabricated via sulfonation treatment, and then decorated with the in situ synthesized zeolitic imidazolate framework-8 (ZIF-8), in which Ag⁺ ions were loaded with high loading capacity. Surface morphology, roughness, chemical composition and hydrophilicity of all the substrates were evaluated in details, suggesting Ag⁺ ions loaded ZIF-8 on sulfonated PEEK (SPZA) was successfully prepared. The antibacterial activity of pristine and functionalized PEEK was evaluated by inhibition zone test, spread plate assay, growth curve, and morphology of bacteria. Experimental results demonstrate that the SPZA has effectively bacteriostatic performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The excellent antimicrobial activity is attributed to the synergistic effect of Ag⁺ and Zn²⁺ ions released continuously from SPZA. This work provides a promising route for surface modification of PEEK and offer a potential candidate for biomedical implants.