In-situ ethylenediamine-assisted synthesis of a magnetic iron-based metal-organic framework MIL-53(Fe) for visible light photocatalysis

Fe-MOFs nanosheets for photo-Fenton degradation of carbamazepine

Iron(II)-based metal organic framework (Fe(II)-MOF) nanosheets have emerged as promising candidates for photo-Fenton catalysis. However, efficiently synthesizing Fe(II)-MOF nanosheets remains a significant challenge. Here, a bottom-up synthesis strategy is proposed to prepare two-dimensional Fe-MOF nanosheets (TFMN) with micrometer lateral dimensions and nanometer thickness, featuring Fe(II) as the metal nodes. The application of TFMN in the photo-Fenton degradation of carbamazepine (CBZ) demonstrates remarkable CBZ degradation performance and excellent efficiency across a wide range of pH values. The electron density and density of states are further calculated by density functional theory. Mechanism analysis identifies h+, •OH and •O2- as the predominant active species contributing to the catalytic oxidation process in the Vis/TFMN/H2O2 system.

S-scheme towards interfacial charge transfer between POMs and MOFs for efficient visible-light photocatalytic Cr (VI) reduction

The establishment of heterojunctions was considered as an exceptional strategy to obtain high-efficiency charge separation and enhanced photocatalytic performance. Herein, a series of FePMo/MIL-53(Fe) (FeM-53) heterojunctions were successfully constructed through in-situ growth of FePMo onto MIL-53(Fe) surface and their photocatalytic capacity were examined by visible-light-induced Cr(VI) reduction. Interestingly, the as-fabricated composites offered various photocatalytic activities controllably relying on the mass ratio of FePMo to MIL-53(Fe). Particularly, the one with the 10% ratio displayed the highest Cr(VI) reduction rate (100%) within 75 min, which was respectively over 4 and 2 folds higher than pure FePMo and MIL-53(Fe). The boosted photoactivity might be ascribed to the establishment of S-scheme heterojunction with suitable band alignment between FePMo and MIL-53(Fe), which broadened the light absorption range and improved charge separation. Further mechanism investigations implied both •O2- and e- were the key reactive species for Cr(VI) removal. Besides, the composite preserved excellent stability after 4 consecutive tests, and performed well in the presence of organic dyes. Such a S-scheme heterojunction may promise for highly efficient environmental mitigation.

Functional MOF-Based Materials for Environmental and Biomedical Applications: A Critical Review

Over the last ten years, there has been a growing interest in metal-organic frameworks (MOFs), which are a unique category of porous materials that combine organic and inorganic components. MOFs have garnered significant attention due to their highly favorable characteristics, such as environmentally friendly nature, enhanced surface area and pore volume, hierarchical arrangements, and adjustable properties, as well as their versatile applications in fields such as chemical engineering, materials science, and the environmental and biomedical sectors. This article centers on examining the advancements in using MOFs for environmental remediation purposes. Additionally, it discusses the latest developments in employing MOFs as potential tools for disease diagnosis and drug delivery across various ailments, including cancer, diabetes, neurological disorders, and ocular diseases. Firstly, a concise overview of MOF evolution and the synthetic techniques employed for creating MOFs are provided, presenting their advantages and limitations. Subsequently, the challenges, potential avenues, and perspectives for future advancements in the utilization of MOFs in the respective application domains are addressed. Lastly, a comprehensive comparison of the materials presently employed in these applications is conducted.

Visible light enhanced persulfate activation for degradation of tetracycline via boosting adsorption of persulfate by ligand-deficient MIL-101(Fe) icosahedron

In this work, Fe-based metal-organic frameworks (Fe-MOFs) are prepared by a simple solvothermal method, in which acetic acid/N, N-dimethylformamide (HAc/DMF) mixture solvents are employed to regulate the particle morphology, exposed facets and ligand defects. At HAc/DMF = 0/50, 5/45 and 8/42 (volume ratio), the irregular particles (MIL-53(Fe)), elongated icosahedrons (5H-MIL-101(Fe)) and icosahedrons (8H-MIL-101(Fe)) are obtained, respectively. Under visible light irradiation (λ > 420 nm) and the addition of sodium persulfate (PS), 5H-MIL-101(Fe) shows the highest degradation activity for tetracycline (TC). Specifically, 80% of TC has been removed by 5H-MIL-101(Fe) within 25 min, and the degradation kinetics rate is 3.03 times higher than that over MIL-53(Fe). The improvement of catalytic activity is mainly attributed to the active facets exposed and ligand defects of 5H-MIL-101(Fe). Density functional theory (DFT) calculation further confirms that the active facets exposed and ligand defects of 5H-MIL-101(Fe) favor the adsorption and activation of PS, benefiting the generation of •SO₄^-. Besides, a probable degradation pathway of TC is proposed based on trapping experiments and liquid chromatography-mass spectrometry (LC-MS) test. Furthermore, the toxicities of intermediates are predicted by the quantitative structure-activity relationship (QSAR) mathematical model. This work demonstrates that visible light enhanced PS activation (Vis-PSA) can more effectively degrade organic pollutants, and this work also provides a simple strategy to precisely regulate ligand defects and actively exposed facets of Fe-MOFs to enhance the adsorption and activation of PS.

Application of Nanocatalysts in Advanced Oxidation Processes for Wastewater Purification: Challenges and Future Prospects

The increase in population demands for industrialization and urbanization which led to the introduction of novel hazardous chemicals in our environment. The most significant parts of these harmful substances found in water bodies remain in the background, causing a health risk to humans and animals. It is critical to remove these toxic chemicals from the wastewater to keep a cleaner and greener environment. Hence, wastewater treatment is a challenging area these days to manage liquid wastes effectively. Therefore, scientists are in search of novel technologies to treat and recycle wastewater, and nanotechnology is one of them, thanks to the potential of nanoparticles to effectively clean wastewater while also being ecologically benign. However, there is relatively little information about nanocatalysts’ applicability, efficacy, and challenges for future applications in wastewater purification. This review paper is designed to summarize the recent studies on applying various types of nanocatalysts for wastewater purification. This review paper highlights innovative work utilizing nanocatalysts for wastewater applications and identifies issues and challenges to overcome for the practical implementation of nanocatalysts for wastewater treatment.

Iron-based metal-organic framework derived pyrolytic materials for effective Fenton-like catalysis: Performance, mechanisms and practicability

In this study, a new catalyst was fabricated by pyrolysis under nitrogen atmosphere with MIL-53(Fe) as the precursor, and was applied to catalyze Fenton-like process. Effects of calcination temperature and pH on decontamination performance, and stability of materials were investigated. Under optimal conditions (calcination temperature of 500 °C and pH of 5.0), the new Fenton-like system remained low iron leaching, and achieved high pseudo-first-order rate constant of 0.0251 min^-1 for bisphenol S (BPS) removal, which is much higher than those in MIL-53(Fe), and nano-Fe₃O₄ catalyzed Fenton-like systems. The superiority of the new catalyst for Fenton-like catalysis was attributed to high specific surface area, as well as formed Fe(II), coordinatively unsaturated iron center and the Fe-O/Fe-C compounds based on the analyses of characterizations. Furthermore, main active species for BPS degradation was identified as hydroxyl radicals, and total hydroxyl radical generation was determined by trapping experiments. The degradation pathways of BPS were also proposed by intermediates monitoring. Moreover, this catalyst showed good potential for practical application, according to the evaluation of reuse, different pollutants degradation, and BPS removal in real wastewater. We believe this study developed a new catalyst with high catalytic activity, high stability and wide application scope, and also sheds light on further development of metal-organic frameworks for Fenton-like catalysis.

Photo-Fenton degradation of carbamazepine and ibuprofen by iron-based metal-organic framework under alkaline condition

Metal-organic frameworks have been widely used as photocatalytic materials. In this paper, a novel photocatalyst HSO₃-MIL-53(Fe) with acidity regulating groups was successfully synthesized by the solvothermal method and applied to remove carbamazepine (CBZ) and ibuprofen (IBP). The photodegradation efficiency of vis/H₂O₂/HSO₃-MIL-53(Fe) can reach 100% when the pH value is 8 or 9. The free radical capture experiment and electron paramagnetic resonance analysis proved that hole (h⁺), hydroxide radical (·OH), singlet oxygen (¹O₂), and superoxide Radical (·O₂^-) are the main active species for pollutants degradation. In the vis/H₂O₂/HSO₃-MIL-53(Fe) system, the high pollutant degradation efficiency under alkaline conditions was attributed to two factors: (1) the acidity adjusting group -HSO₃ adjusts the pH value of the whole system, which is beneficial to the photo-Fenton process. (2) The photogenerated electrons of HSO₃-MIL-53(Fe) can be captured by Fe (III), H₂O₂ and O₂ to accelerate the reduction of Fe (III) and generate ·OH, ¹O₂, and ·O₂^-. Besides, H₂O₂ can also be activated by Fe (II) and Fe (III). The above processes synergistically improved the photocatalytic efficiency. Based on liquid chromatography-mass spectrometry (LC-MS) analysis, the possible degradation pathways of the two pollutants were proposed.

Highly Sensitive Detection of Trace Tetracycline in Water Using a Metal-Organic Framework-Enabled Sensor

Due to the abuse application of antibiotics in the recent decades, a high level of antibiotics has been let out and remains in our environment. Electrochemical sensing is a useful method to sensitively detect antibiotics, and the key factor for a successful electrochemical sensor is the active electrode materials. In this study, a sensitive electrochemical sensing platform based on a metal-organic framework (MOF) of MIL-53 (Fe) was facilely fabricated. It shows highly selective and sensitive detection performance for trace tetracycline. Differential pulse voltammetry (DPV) was applied to analyze the detection of tetracycline. The linear range of tetracycline detection was 0.0643 μmol/L-1.53 μmol/L, and the limit of detection (LOD) is 0.0260 μmol/L. Furthermore, the MOF-enabled sensor can be effectively used in actual water bodies. The results indicate that the electrochemical sensor is a high potential sensing platform for tetracycline.

Facile Fabrication of Novel NiFe2O4@Carbon Composites for Enhanced Adsorption of Emergent Antibiotics

Water purification is becoming one of the most pertinent environmental issues throughout the world. Among common types of water pollution involving heavy metals, pharmaceutical drugs, textile dyes, personal care products, and other persistent organic pollutants, the pollution of antibiotic drugs is increasingly emerging due to their adverse effects on microorganisms, aquatic animals, and human health. Therefore, the treatment of such contaminants is very necessary to reduce the concentration of antibiotic pollutants to permissible levels prior to discharge. Herein, we report the use of NiFe₂O₄@C composites from a bimetallic-based metal-organic framework Ni-MIL-88B(Fe) for removal of ciprofloxacin (CFX) and tetracycline (TCC). The effect of production temperatures (600–900 °C), solution pH (2–10), NiFe₂O₄@C dose (0.05–0.2 g/L), concentration of antibiotics (10–60 mg/L), and uptake time (0–480 min) was investigated systematically. Response surface methodology and central composite design were applied for quadratic models to discover optimum conditions of antibiotic adsorption. With high coefficients of determination (R² = 0.9640–0.9713), the proposed models were significant statistically. Under proposed optimum conditions, the adsorption capacity for CFX and TCC were found at 256.244, and 105.38 mg/g, respectively. Recyclability study was employed and found that NiFe₂O₄@C-900 could be reused for up to three cycles, offering the potential of this composite as a good adsorbent for removal of emergent antibiotics.

Insights into the Stability and Activity of MIL-53(Fe) in Solar Photocatalytic Oxidation Processes in Water

MIL-53(Fe) is a metal organic framework that has been recently considered a heterogeneous photocatalyst candidate for the degradation of water pollutants under visible or solar radiation, though stability studies are rather scarce in the literature. In this work, MIL-53(Fe) was successfully synthesized by a solvothermal method and fully characterized by X-ray diffraction (XRD), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), N2 adsorption–desorption isotherm, Thermogravimetric analysis coupled with mass spectrometry (TGA-MS), UV-visible diffuse reflectance spectroscopy (DRS), elemental analysis and wavelength dispersive X-ray fluorescence (WDXRF). The effects of pH, temperature, solar radiation and the presence of oxidants (i.e., electron acceptors) such as ozone, persulfate and hydrogen peroxide on the stability of MIL-53(Fe) in water were investigated. The as-synthetized MIL-53(Fe) exhibited relatively good stability in water at pH 4 but suffered fast hydrolysis at alkaline conditions. At pH 4–5, temperature, radiation (solar and visible radiation) and oxidants exerted negative effect on the stability of the metal–organic framework (MOF) in water, resulting in non-negligible amounts of metal (iron) and linker (terephthalic acid, H2BDC) leached out from MIL-53(Fe). The photocatalytic activity of MIL-53(Fe) under simulated solar radiation was studied using phenol and metoprolol as target pollutants. MIL-53(Fe) on its own removed less than 10% of the pollutants after 3 h of irradiation, while in the presence of ozone, persulfate or hydrogen peroxide, complete elimination of pollutants was achieved within 2 h of exposure to radiation. However, the presence of oxidants and the formation of some reaction intermediates (e.g., short-chain carboxylic acids) accelerated MIL-53(Fe) decarboxylation. The findings of this work suggest that MIL-53(Fe) should not be recommended as a heterogeneous photocatalyst for water treatment before carrying out a careful evaluation of its stability under actual reaction conditions.

Biomass-based 0D/3D N-CQD/MIL-53(Fe) photocatalyst for the simultaneous remediation of multiple hazardous pollutants in sewage

The implementation of N-CQD/MIL-53(Fe) photocatalyst in the area of photocatalytic multi-component sewage remediation.

Rapid degradation of tetracycline hydrochloride by heterogeneous photocatalysis coupling persulfate oxidation with MIL-53(Fe) under visible light irradiation

This work demonstrates a facile route to assemble MIL-53(Fe) by solvothermal method. Sulfate radical-based advanced oxidation processes (SR-AOPs) coupling with photocatalysis based on MIL-53(Fe) were investigated under visible light. The catalytic effect of MIL-53(Fe) for the degradation of tetracycline hydrochloride (TC-HCl) was systematically studied, as well as the reusability of the catalyst and the effect of operating parameters. The results indicated that 99.7 % of TC (300 mg/L) could be degraded within 80 min in the SR-AOPs coupling with photocatalysis processes, as compared to 71.4 % for the SR-AOPs and only 17.1 % for the photocatalysis. The trapping experiments and electron spin-resonance spectroscopy (ESR) showed the photogenerated electrons of MIL-53(Fe) under visible light irritation were trapped by persulfate to generated sulfate radicals which effectively suppressed the recombination of photogenerated carriers. And also, the SO₄^- could be formed by the conversion between Fe (Ⅲ) and Fe (Ⅱ) in MIL-53(Fe). Moreover, OH and O₂^- generated by the reaction increased significantly due to the increase of SO₄^- which generated more OH and reduced photogenerated carrier recombination respectively. Thus, the degradation efficiency of TC-HCl was improved. Furthermore, the degradation pathway for TC-HCl was proposed using the theoretical calculations and liquid chromatography coupled with mass spectrometry.

Dispersive solid-phase extraction of buprenorphine from biological fluids using metal-organic frameworks and its determination by ultra-performance liquid chromatography

In this work, various types of metal-organic frameworks were synthesized, and their affinities toward buprenorphine were evaluated using dispersive solid-phase extraction. The extracted buprenorphine was determined by ultra high performance liquid chromatography-ultraviolet detection system. The highest extraction recovery was observed by employing zeolitic imidazole framework-67. Then, a facile and fast extraction method was designed for the extraction and purification of the target drug. Optimization of the extraction method was carried out by the design of experiment approach. A linearity range of 1-1000 μg/L with the limit of detection of 0.15 μg/L and relative standard deviations (50 μg/L, n = 5) of 3.4% was obtained for standard sample analysis. Under optimized experimental and instrumental conditions, the relative recoveries were in the range of 95 to 111%. Eventually, zeolitic imidazole framework-67 was successfully employed for the extraction and determination of buprenorphine in the biological fluids with satisfactory results.

Tuning Crystal Structures of Iron-Based Metal-Organic Frameworks for Drug Delivery Applications

Iron-based metal-organic frameworks (Fe-MOFs) have emerged as promising candidates for drug delivery applications due to their low toxicity, structural flexibility, and safe biodegradation in a physiological environment. Here, we studied two types of Fe-MOFs: MIL-53 and MIL-88B, for in vitro drug loading and releasing of ibuprofen as a model drug. Both Fe-MOFs are based on the same iron clusters and organic ligands but form different crystal structures as a result of two different nucleation pathways. The MIL-53 structure demonstrates one-dimensional channels, while MIL-88B exhibits a three-dimensional cage structure. Our studies show that MIL-53 adsorbs more ibuprofen (37.0 wt %) compared to MIL-88B (19.5 wt %). A controlled drug release was observed in both materials with a slower elution pattern in the case of the ibuprofen-encapsulated MIL-88B. This indicates that a complex cage structure of MIL-88 is beneficial to control the rate of drug release. A linear correlation was found between cumulative drug release and the degree of material degradation, suggesting the biodegradation of Fe-MILs as the main drug elution mechanism. The cytotoxicity of MIL-88B was evaluated in vitro with NIH-3T3 Swiss mouse fibroblasts, and it shows that MIL-88B has no adverse effects on cell viability up to 0.1 mg/mL. This low toxicity was attributed to the morphology of MIL-88B nanocrystals. The very low toxicity and controlled drug release behavior of Fe-MIL-88B suggest that better materials for drug-delivery applications can be created by controlling not only the composition but also the crystal structure and nanoparticle morphology of the material.

Facile Strategy to Synthesize Magnetic Upconversion Nanoscale Metal-Organic Framework Composites for Theranostics Application

Recently, the design of a theranostics system has involved increasing attention in the area of biomedical applications. In many cases, the intricate synthesis process of upconversion nanoparticle-based composite materials limits the use of theranostics applications. To address this challenge, a nanocomposite has been successfully fabricated by the conjugation of magnetic NaGdF₄:Yb/Er nanoparticles as an imaging agent and MIL-53(Fe) as a drug carrier through a single step. Simultaneously, folic acid is encapsulated on the surface of the nanocomposite by conjugation chemistry to achieve the targeted drug delivery applications. The synthesized nanocomposite exhibits a sufficient amount of loading ability toward the model anticancer doxorubicin and possesses pH-responsive drug release. The functionalized nanocomposite not only possesses excellent colloidal stability and good magnetic and fluorescence property but also shows superior biocompatibility, strong tumor cell growth inhibitory effect, and cancer-enhanced cellular uptake. It is expected that the synthesized nanocomposite can also serve as a platform for both T₁ and T₂ MRI contrast agents.

Recent advances in MOF-based photocatalysis: environmental remediation under visible light

Highly photoactive MOFs can be engineered via various strategies for the purpose of extended visible light absorption, more efficient generation, separation and transfer of charge carriers, as well as good recyclability.

Nanoporous bimetallic metal-organic framework (FeCo-BDC) as a novel catalyst for efficient removal of organic contaminants

In this work, we report on the synthesis and characterization of nanoporous bimetallic metal-organic frameworks (FeCo-BDC). Effects of synthesis time and temperature on the structures, morphology, and catalytic performance of FeCo-BDC were investigated. Scanning Electron Microscopy (SEM), Transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) were used to reveal the morphological and textural characteristics. The crystal structure and chemical composition of FeCo-BDC were determined by means of X-ray powder diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) measurements. Interestingly, FeCo-BDC grew into the same crystal structure with different morphology in the temperature of 110-150 °C with 12-48 h. The heterogeneous catalytic activity of FeCo-BDC was tested to activate peroxydisulfate (PDS) and peroxymonosulfate (PMS) for removal of methylene blue (MB). The results found that FeCo-BDC synthesized at 150 °C with 24 h exhibited the best catalytic performance for PMS and obtained 100% of MB removal within 15 min. The abundant unsaturated metal active sites of Fe(II) and Co(II) in the skeleton of FeCo-BDC made a great contribution to the generation of sulfate () and hydroxyl radicals (OH), which resulted in the excellent performance for MB degradation.

The Synthesis of N-(Pyridin-2-yl)-Benzamides from Aminopyridine and Trans-Beta-Nitrostyrene by Fe2Ni-BDC Bimetallic Metal–Organic Frameworks

A bimetallic metal–organic framework material, which was generated by bridging iron (III) cations and nickel (II) cations with 1,4-Benzenedicarboxylic anions (Fe2Ni-BDC), was synthesized by a solvothermal approach using nickel (II) nitrate hexahydrate and iron (III) chloride hexahydrate as the mixed metal source and 1,4-Benzenedicarboxylic acid (H2BDC) as the organic ligand source. The structure of samples was determined by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and nitrogen physisorption measurements. The catalytic activity and recyclability of the Fe2Ni-BDC catalyst for the Michael addition amidation reaction of 2-aminopyridine and nitroolefins were estimated. The results illustrated that the Fe2Ni-BDC catalyst demonstrated good efficiency in the reaction under optimal conditions. Based on these results, a reaction mechanism was proposed. When the molar ratio of 2-aminopyridine and trans-β-nitrostyrene was 1:1, and the solvent was dichloromethane, the isolated yield of pyridyl benzamide reached 82%; at 80 °C over 24 h. The catalyst can be reused without a substantial reduction in catalytic activity with 77% yield after six times of reuse.

Application of Fe-based metal-organic framework and its pyrolysis products for sulfonamide treatment

The occurrence and fate of antibiotic compounds in water can adversely affect human and animal health; hence, the removal of such substrates from soil and water is indispensable. Herein, we described the synthesis method of mesoporous carbon (MPC) via the pyrolysis route from a coordination polymer Fe-based MIL-53 (or MIL-53, shortly). The MPC structure was analyzed by several physical techniques such as SEM, TEM, BET, FT-IR, VSM, and XRD. The response surface methodology (RSM) was applied to find out the effects of initial concentration, MPC dosage, and pH on the removal efficiency of trimethoprim (TMP) and sulfamethoxazole (SMX) antibiotics in water. Under the optimized conditions, the removal efficiencies of TMP and SMX were found to be 87% and 99%, respectively. Moreover, the adsorption kinetic and isotherm studies showed that chemisorption and the monolayer adsorption controlled the adsorption process. The leaching test and recyclability studies indicated that the MPC structure was stable and can be reused for at least four times without any considerable change in the removal efficiency. Plausible adsorption mechanisms were also addressed in this study. Because of high maximum adsorption capacity (85.5 mg/g and 131.6 mg/g for TMP and SMX, respectively) and efficient reusability, MPC is recommended to be a potential adsorbent for TMP and SMX from water media.

Enhanced photocatalysis using metal-organic framework MIL-101(Fe) for organophosphate degradation in water

Metal-organic frameworks (MOFs) are attractive novel classes of porous materials with diverse potentiality and easily tailored structures. It is desirable to evaluate the performance of MOFs as photocatalysts for organic contaminant removal in aqueous matrixes. In this study, iron-based MIL-101(Fe) was synthesized and a photo-Fenton reaction system (multiple wavelength light + MIL-101(Fe) + H₂O₂) was developed for elimination of tris(2-chloroethyl) phosphate (TCEP). Degradation pattern of TCEP followed an S-shape curve, which included a slow induction period and a rapid radical oxidation process. Transport of reactants into MIL-101(Fe) and the activation of electron transport within Fe-O clusters of MIL-101(Fe) may be the dominant mechanisms in the induction period, while a pseudo-first-order kinetics was observed in the hydroxyl radical oxidation process. Removal efficiencies in these two stages highly depended on the reaction conditions. Irradiation at 420 nm and acid condition were conductive, while high temperature and high [H₂O₂]:[MIL-101(Fe)] mass ratio accelerated the reaction. Before complete mineralization, eleven degradation products were generated, and the dominant degradation pathways included cleavage, hydroxylation, carbonylation, and carboxylation. Under acid condition (pH = 3), only 1% mass loss was observed after 60-min reaction, but the iron leakage was aggravated when pH increased. Furthermore, this MOF-photo-Fenton system demonstrated a robust performance on TCEP degradation in actual wastewater matrixes under acid condition. Generally, the MOF-photo-Fenton system is a potential technology for elimination of organic pollutants in aqueous solution.

Water depollution using metal-organic frameworks-catalyzed advanced oxidation processes: A review

This paper presents a review on the environmental applications of metal-organic frameworks (MOFs), which are inorganic-organic hybrid highly porous crystalline materials, prepared from metal ion/clusters and multidentate organic ligands. The emphases are made on the enhancement of the performance of advanced oxidation processes (AOPs) (photocatalysis, Fenton reaction methods, and sulfate radical (SO₄^-)-mediated oxidations) using MOFs materials. MOFs act as adsorption and light absorbers, leading to superior performance of photocatalytic processes. More recent examples of photocatalytic degradation of dyes are presented. Additionally, it is commonly shown that Fe-based MOFs exhibited excellent catalytic performance on the Fenton-based and SO₄^•--mediated oxidations of organic pollutants (e.g., dyes, phenol and pharmaceuticals). The significantly enhanced generation of reactive species such as OH and/or SO₄^- by both homogeneous and heterogeneous catalysis was proposed as the possible mechanism for water depollution. Based on the existing literature, the challenge and future perspectives in MOF-based AOPs are addressed.

A Review on the Synthesis and Characterization of Metal Organic Frameworks for Photocatalytic Water Purification

This review analyzes the preparation and characterization of metal organic frameworks (MOFs) and their application as photocatalysts for water purification. The study begins by highlighting the problem of water scarcity and the different solutions for purification, including photocatalysis with semiconductors, such as MOFs. It also describes the different methodologies that can be used for the synthesis of MOFs, paying attention to the purification and activation steps. The characterization of MOFs and the different approaches that can be followed to learn the photocatalytic processes are also detailed. Finally, the work reviews literature focused on the degradation of contaminants from water using MOF-based photocatalysts under light irradiation.

Simultaneous efficient adsorption and accelerated photocatalytic degradation of chlortetracycline hydrochloride over novel Fe-based MOGs under visible light irradiation assisted by hydrogen peroxide

Two novel porous MOGs were prepared for degrading CTC, and JLUE-MOG-1 exhibited an enhanced performance because of the photo-Fenton synergistic effect.

Heterojunction Cu2O/RGO/BiVO4 ternary nanocomposites with enhanced photocatalytic activities towards degradation of rhodamine B and tetracycline hydrochloride

The synergy of BVO, Cu₂O and RGO inhibits the recombination of photogenic carriers to enhance the photocatalytic activity.

Effective Photocatalytic Activity of Mixed Ni/Fe-Base Metal-Organic Framework under a Compact Fluorescent Daylight Lamp

Mixed Ni/Fe-base metal-organic framework (Ni/Fe-MOF) with different molar ratios of Ni2+/Fe3+ have been successfully produced using an appropriate solvothermal router. Physicochemical properties of all samples were characterized using X-ray diffraction (XRD), Raman, field emission scanning electron microscopes (FE-SEM), fourier-transform infrared spectroscopy (FT-IR), N2 adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS), and photoluminescence spectra (PL). The photocatalytic degradation performances of the photocatalysts were evaluated in the decomposition of rhodamine B (RhB) under a compact fluorescent daylight lamp. From XRD, IR, XPS, and Raman results, with the presence of mixed ion Fe3+ and Ni2+, MIL-88B (MIL standing for Materials of Institut Lavoisier) crystals based on the mixed metal Fe2NiO cluster were formed, while MIL-53(Fe) was formed with the presence of single ion Fe3+. From UV-Vis DRS results, Ni/Fe-MOF samples exhibited the absorption spectrum up to the visible region, and then they showed the high photocatalytic activity under visible light irradiation. A Ni/Fe-MOF sample with a Ni2+/Fe3+ molar ratio of 0.3 showed the highest photocatalytic degradation capacity of RhB, superior to that of the MIL-53(Fe) sample. The obtained result could be explained as a consequence of the large surface area with large pore volumes and pore size by the Ni2+ incorporating into the MOF’s structure. In addition, a mixed metal Fe/Ni-based framework consisted of mixed-metal cluster Fe2NiO with an electron transfer effect and may enhance the photocatalytic performance.

A facile strategy for fabricating AgI–MIL-53(Fe) composites: superior interfacial contact and enhanced visible light photocatalytic performance

Through a simple grinding process, AgI–MIL-53(Fe) composites with superior interfacial contact between AgI and MIL-53(Fe) have been successfully fabricated and exhibit improved visible light photocatalytic activity for dye degradation.