Iron-copper bimetallic metal-organic frameworks for efficient Fenton-like degradation of sulfamethoxazole under mild conditions

Iron-copper bimetallic photo-Fenton system promoted photothermal-hydrogen peroxide production for efficient low-temperature wastewater treatment

Enhancing the velocity of the oxidation-reduction cycle is crucial for improving the catalytic efficiency of Fenton processes. Therefore, the development of an effective strategy for wastewater degradation at low temperatures is essential. In this context, we present the preparation of an NH2-MIL-88B (Fe)/CuInS2 S-scheme heterojunction. Specifically, CuInS2 nanoparticles are introduced onto the Ferro-organic skeleton, resulting in the exposure of a significant number of active surface sites. Furthermore, NH2-MIL-88B (Fe)/CuInS2 demonstrates an extended photoresponse into the long-wavelength region, which contributes to its excellent photothermal properties. Notably, the degradation rate of tetracycline in low-temperature aqueous environments reaches as high as 99.7 %, several times higher than that of the original sample. Additionally, the hydrogen production of NH2-MIL-88B (Fe)/CuInS2 is 2.23 times that of single NH2-MIL-88B (Fe) and 3.46 times that of single CuInS2. Moreover, the system exhibits good H2O2 evolution performance, forming an efficient photo-Fenton system. The charge transfer process in S-scheme heterojunction is confirmed using in-situ X-ray photoelectron spectroscopy and electron paramagnetic resonance. Both transient photoluminescence and photo electrochemical tests further validate the enhanced photoelectrochemical properties of the NH2-MIL-88B (Fe)/CuInS2 S-scheme heterojunction. The exceptional performance of this system can be attributed to the synergistic effects of the S-scheme heterojunction and the bimetallic codoped photo-Fenton system. This research presents a novel approach for the breakdown of low-temperature wastewater using an improved photocatalytic Fenton system.

Palladium Nanoparticle-Decorated Copper-Hemin Metal Organic Framework for Enzymatic Electrochemical Detection of Creatinine in Human Urine

Creatinine is indeed a crucial biomarker for kidney diseases. In this work, a novel electrochemical biosensor based on a copper-hemin metal organic framework [Cu-hemin metal-organic framework (MOF)] nanoflake decorated with palladium (Pd) (Pd/Cu-hemin MOF) was fabricated and incorporated with creatinine deiminase (CD) on a glassy carbon electrode (GCE) for creatinine detection. The formation of a Pd/Cu-hemin MOF composite was confirmed by X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The formation of the composite as nanoflakes is evident from the scanning electron microscopy image. The transmission electron microscopy image clarifies the decoration of palladium nanoparticles on Cu-hemin MOF surfaces. Thus, the proposed biosensor (Pd/Cu-hemin MOF/CD/GCE) electrochemical performances were studied with cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. As a result, the Pd/Cu-hemin MOF/CD/GCE-based electrochemical detection of creatinine exhibits a broad linear range from 0 to 130 μM (R2 = 0.99), a low limit of detection 0.08 μM, and an excellent sensitivity of 3.2 μA μM-1 cm-2. The biosensor also determines creatinine in samples of human urine with a good recovery from 99.4 to 100.8%. Thus, in this study, an electrochemical biosensing platform based on Pd/Cu-hemin MOF/CD/GCE has been designed practically for creatinine.

Nano-photosensitizers with gallic acid-involved Fe-O-Cu "electronic storage station" bridging ligand-to-metal charge transfer for efficient catalytic theranostics

NH2-MIL-88B (Fe) (MOF) is a promising photocatalytic material for antitumor therapy because of its distinctive electronic structure. However, inadequate separation of photo-generated electrons and slow reaction rate in low/high-valence iron (Fe) cycles limit their clinical application. In the present study, "electronic storage station" as a ligand-to-metal charge transfer bridge bond was constructed to inhibit recombination of electron/hole under 650 nm laser irradiation. Cupric (Cu) ions and gallic acid (GA) were self-assembled into a MOF (denoted as CGMOF) to create an FeO(GA)Cu bridge bond. GA, characterized by robust electron delocalization and abundant electron-donating groups, significantly enhances electron transfer efficiency for photodynamic therapy (PDT). CGMOF can respond to endogenous glutathione and release cuprous ions, accelerating the iron ion/ferrous ion cycles for chemodynamic therapy (CDT). The released Fe species can serve as T2-weighted magnetic resonance imaging contrast. Extended X-ray absorption fine structure spectra confirmed the presence of GA-containing FeOCu bonds in CGMOF. Furthermore, a series of photo-electrochemical tests confirmed that the formation of FeO(GA)Cu bond prominently elevated the redox capacity and increased the carrier density of CGMOF by 2.74-fold compared to that of MOF. In addition, cinnamaldehyde was grafted onto CGMOF for tumor-responsive hydrogen peroxide self-supply. Concurrently, hyaluronic acid was surface-modified to achieve the targeted delivery of nano-photosensitizers. In summary, this study presents an innovative approach for engineering Fe-based metal-organic frameworks for synergetic PDT/CDT applications.

Recent advances in discrete Cu complexes for enhanced chemodynamic therapy

Since the concept of metal ion stimulation-mediated chemodynamic therapy was proposed by Bu and Shi's group in 2016, increasing attention has been directed toward the fabrication of efficient, safe and stable Fenton/Fenton-like catalysts to advance clinical translation. In particular, metal-based complexes with inherent metal catalytic centers have received extensive attention as potential alternatives/complements for traditional CDT agents. Among them, copper-based complexes, which possess excellent redox properties, extensive adaptability and abundant availability, enable the efficient generation of ROS through Fenton-like reactions in CDT, thereby causing oxidative damage to lipids, proteins, and DNA in cancer cells. In this brief review, we summarize the recent progress on various discrete copper-based metal complexes aimed at enhancing the therapeutic efficacy of CDT as well as their application in combination therapy. We hope that this review will attract active attention toward metal complexes in advancing more accurate and efficient chemodynamic therapy and encourage further in-depth research to facilitate clinical translation.

Biomedical Metal-Organic Framework Materials: Perspectives and Challenges

Metal-organic framework (MOF) materials are gaining significant interest in biomedical research, owing to their high porosity, crystallinity, and structural and compositional diversity. Their versatile hybrid organic/inorganic chemistry endows MOFs with the capacity to retain organic (drug) molecules, metals, and gases, to effectively channel electrons and photons, to survive harsh physiological conditions such as low pH, and even to protect sensitive biomolecules. Extensive preclinical research has been carried out with MOFs to treat several pathologies and, recently, their integration with other biomedical materials such as stents and implants has demonstrated promising performance in regenerative medicine. However, there remains a significant gap between MOF preclinical research and translation into clinically and societally relevant medicinal products. Here, we outline the intrinsic features of MOFs and discuss how these are suited to specific biomedical applications like detoxification, drug and gas delivery, or as (combination) therapy platforms. We furthermore describe relevant examples of how MOFs have been engineered and evaluated in different medical indications, including cancer, microbial, and inflammatory diseases. Finally, we critically examine the challenges facing their translation into the clinic, with the goal of establishing promising research directions and more realistic approaches that can bridge the translational gap of MOFs and MOF-containing (nano)materials.

Electro-Fenton degradation of pefloxacin using MOFs derived Cu, N co-doped carbon as a nanocomposite catalyst

Electro-Fenton (EF) can in-situ produce H2O2 and effectively activate H2O2 to generate powerful reactive species for the destruction of contaminants under acidic conditions, however, the production of iron-containing sludge and requirement of low working pH significantly hinder its practical application. Herein, a novel Cu, N co-doped carbon (Cu-N@C) with metal organic framework (MOF) as a precursor was constructed and adopted for the elimination of pefloxacin (PEF) in the heterogeneous electro-Fenton (HEF) process. PEF could be almost completely removed within 1 h and total organic carbon (TOC) removal efficiency was 48.57% within 6 h. Meanwhile, Cu-N@C had good repeatability and environmental adaptability, it can still maintain excellent catalytic performance after 10 cycles, and it exhibited satisfactory remediation performance in simulated water matrix. In addition, the HEF process catalyzed by Cu-N@C also showed satisfactory degradation effect on other organic pollutants including atrazine, methylene blue, and chlorotetracycline. Under the action of impressed current, the HEF system could generate H2O2 in-situ, and the active species could be generated in the redox cycle of Cu0/Cu1+/Cu2+. Electron paramagnetic resonance and quenching experiments confirmed that •OH was the dominant active species in the degradation of organic compounds. The degradation process of PEF was studied by mass spectrometry analysis of intermediate products. This study provided a simple method to prepare MOF-based electrocatalyst, which exhibits promising application potential for treatment wastewater.

Ultrasensitive detection of H2O2 via electrochemical sensor by graphene synergized with MOF-on-MOF nanozymes

An electrochemical sensor was developed for the detection of hydrogen peroxide (H2O2), utilizing the synergistic effects of graphene (Gr) and MOF-on-MOF nanozymes (FeCu-NZs). Initially, Fe-MOF with peroxide-like activity is synthesized using a solvothermal method. Subsequently, the organic ligand on its surface binds Cu2+, enhancing the enzyme-like activity further. The resulting FeCu-NZs exhibit a distinctive electrochemical signal in response to H2O2. Moreover, integrating FeCu-NZs with Gr significantly amplifies the electrochemical signal and effectively reduces the sensor's detection limit. The developed sensor exhibited linear ranges of 0.1-3800 μM, with a limit of detection (LOD) of 0.06 μM. Additionally, FeCu-NZs catalyze H2O2 to generate abundant •OH radicals, and colorimetric detection of H2O2 is facilitated using the color rendering principle of 3,3',5,5'-tetramethylbenzidine (TMB). Notably, this detection method was applied to determine  H2O2 concentrations in real samples, achieving a recovery exceeding 95.7%. In summary, this research provides a practical platform for the construction of traditional nanozymes and the integration of electrochemical systems, which have broad applications in food analysis, environmental monitoring, and medical diagnosis.

The use of bimetallic metal-organic frameworks as restoration materials for pollutants removal from water environment

Bimetallic metal-organic frameworks (BMOFs) are a class of functional porous materials constructed by coordination between nodes containing two different metal ions and organic ligands. Studies have shown that the catalytic activity of BMOFs is greatly improved owing to the adjustment of charge distribution and the increase of active sites as well as the synergistic effect between the bimetals, and the advantages of their large specific surface area, high porosity, unique structure and dispersed active centres make them available as important organic materials applied in the field of wastewater treatment. In this review, the preparation and construction methods for BMOFs in recent years are summarized, and we focus on their removal of different types of pollutants in the aqueous environment, including ions, dyes, pharmaceuticals or personal care products, phenolic compounds and microorganisms, as well as their corresponding removal mechanisms. In addition, we provide an outlook on their future opportunities and challenges in wastewater treatment.

Adsorption of antiretroviral drugs, abacavir, nevirapine, and efavirenz from river water and wastewater using exfoliated graphite: Isotherm and kinetic studies

In this work, exfoliated graphite was used to adsorb antiretroviral drugs from river water and wastewater. The exfoliated graphite was prepared from natural graphite by intercalating it with the acids and exfoliating it at 800 °C. It was characterized using Fourier Transform Infrared Spectroscopy which showed phenolic, alcoholic, and carboxylic functional groups between 1000 cm-1 and 1700 cm-1. Energy-dispersive X-ray spectroscopy results showed carbon as the main element with splashes of oxygen. The Scanning Electron Microscopy images showed increased c-axis distance between graphene layers after intercalation, which further increased after the exfoliation. The exfoliation resulted in elongated distorted cylinders, which were confirmed by the lower density (0.0068 g/mL) of exfoliated graphite material compared to the natural graphite (0.54 g/mL). The X-ray diffraction pattern showed the characteristics of hexagonal phase graphitic structure by the diffraction plane (002) at 26.74°. Raman spectroscopy results showed the natural graphite, graphite intercalated, and exfoliated graphite contained the D, G, D', and G' peaks at about 1350 cm-1, 1570 cm-1, 2440 cm-1, and 2720 cm-1, respectively indicating that the material's crystallinity was not affected by the modification. The highest antiretroviral drugs removal (95-99%), from the water was achieved with a solution pH of 7, an adsorbent mass of 30 mg, and an adsorption time of 30 min. The kinetic model and adsorption isotherm studies showed that the experimental data fit well in pseudo-second-order kinetics and is well explained by Freundlich's adsorption isotherm. The maximum adsorption capacity of the exfoliated graphite for antiretroviral drugs ranges between 1.660 and 197.0, 1.660-232.5, and 1.650-237.7 mg/g for abacavir, nevirapine, and efavirenz, respectively. The obtained removal percentages were 100% in river water, 63-100% in influent and 70-100% in effluent wastewater unspiked samples.

Cobalt based bimetallic catalysts for heterogeneous electro-Fenton adapting to vary pH for HEDP and MIT degradation

Most of the materials studied as catalysts in the electro-Fenton system are variants of iron oxide or iron hydroxide. However, iron-based catalysts often exhibit weak catalytic capabilities under neutral and alkaline conditions. In this work, we synthesized three cobalt based bimetallic oxides, Co2CuOx, Co2AlOx, and Co2NiOx, using hydrothermal method and evaluated them as catalysts for the heterogeneous electro-Fenton system to remove 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and Methylisothiazolinone [2-methyl-4-isothiazolin-3-one] (MIT). Co2NiOx has the highest catalytic degradation activity for HEDP, and Co2CuOx has the best catalytic degradation effect for MIT. Based on characterization results of the catalysts, the reasons for the differences in the pollutant removal efficiency were analysed, and the optimal pH for the three cobalt based oxides to remove HEDP and MIT was investigated. The results showed that the optimal pH values of the three cobalt based bimetallic oxides are not only influenced by the second metal type, but also by the properties of pollutants. Therefore, suitable cobalt based catalysts can be selected based on the different properties of pollutants, or the composition of cobalt based catalysts can be adjusted to meet the different pH requirements of target wastewater. The three cobalt based bimetallic oxides exhibited good degradation of HEDP and MIT under neutral conditions, which to some extent solved the problem of narrow pH range in the practical application of the electro-Fenton process.

FeCu bimetallic metal organic frameworks photo-Fenton synergy efficiently degrades organic pollutants: Structure, properties, and mechanism insight

The high ion leaching, low photogenerated charge separation efficiency, and slow metal valence cycling of Fe-based metal organic frameworks (MOFs) have limited their application in the deep treatment of organic pollutants. Herein, FeCu bimetallic MOFs (FeCuBDC) were synthesized using a modified solvothermal method, and a coupled photo-Fenton degradation system was successfully constructed. Degradation performance tests showed that FeCuBDC could efficiently degrade 99.3% ± 0.1% of 50 mg/L phenol within 40 min. The reaction rate constants of the photo-Fenton system were 11.0 and 64.7 times higher than those of the single Fenton reaction and photocatalysis, respectively. FeCuBDC also exhibits good cycling stability, degradation generalization, and excellent photoelectric catalytic properties. Such a considerable enhancement in the overall performance pertains to the following. First, the introduction of Cu into Fe-MOFs not only improves the crystallinity and stability, but also reduces the band gap value, increases the absorption capacity of visible light, and promotes the generation of photogenerated carriers. Second, the FeCu in MOFs are all mixed valence. Initially, the high-valence FeCu captures photogenerated electrons and promotes photogenerated charge separation and transfer. Then, the low-valence FeCu adsorbs and decomposes H2O2, accelerating the valence cycling of the bimetallic sites. The core of the reaction mechanism is that FeCuBDC effectively promotes the photo-Fenton synergy.

In-situ production and activation of H2O2 over hydroxyapatite modified CuFeO2 for self-sufficient heterogeneous photo-Fenton degradation of doxycycline hydrochloride

The self-sufficient heterogeneous photo-Fenton (SH-PF) system was constructed for doxycycline hydrochloride (DOH) degradation with hydroxyapatite (Hap) modified CuFeO2 (Hap/CuFeO2) composites through H2O2 in-situ production. The modification of Hap could improve the specific surface area, visible-light response, light conversion efficiency, photoelectron lifetime and oxygen vacancies (OVs) of CuFeO2, which was conducive to H2O2 production and DOH degradation in SH-PF system. Notably, Hap/CuFeO2 fabricated with 0.5 g Hap (Hap/CuFeO2-0.5) displayed more superior performance for DOH degradation compared to other synthesized catalysts. The Hap/CuFeO2-0.5 load and initial solution pH for DOH degradation in SH-PF system were optimized, and the Hap/CuFeO2-0.5 had good reusability and stability. The •OH was the main active species for DOH degradation, and the facilitation effect of •O2- and photoelectrons on DOH degradation was associated with the H2O2 production in the present work. In addition, the capture of photogenerated holes suppressed the recombination of photogenerated carriers, elevating the production of photoelectrons and thereby enhancing H2O2 production and DOH degradation. The degradation pathways for DOH were proposed and the comprehensive toxicities of DOH were relieved after degradation in SH-PF system.

Fe-Co-Based Metal-Organic Frameworks as Peroxidase Mimics for Sensitive Colorimetric Detection and Efficient Degradation of Aflatoxin B1

Building multifunctional platforms for integrating the detection and control of hazards has great significance in food safety and environment protection. Herein, bimetallic Fe-Co-based metal-organic frameworks (Fe-Co-MOFs) peroxidase mimics are prepared and applied to develop a bifunctional platform for the synergetic sensitive detection and controllable degradation of aflatoxin B1 (AFB1). On the one hand, Fe-Co-MOFs with excellent peroxidase-like activity are combined with target-induced catalyzed hairpin assembly (CHA) to construct a colorimetric aptasensor for the detection of AFB1. Specifically, the binding of aptamer with AFB1 releases the prelocked Trigger to initiate the CHA cycle between hairpin H2-modified Fe-Co-MOFs and hairpin H1-tethered magnetic nanoparticles to form complexes. After magnetic separation, the colorimetric signal of the supernatant in the presence of TMB and H2O2 is inversely proportional to the target contents. Under optimal conditions, this biosensor enables the analysis of AFB1 with a limit of detection of 6.44 pg/mL, and high selectivity and satisfactory recovery in real samples are obtained. On the other hand, Fe-Co-MOFs with remarkable Fenton-like catalytic degradation performance for organic contaminants are further used for the detoxification of AFB1 after colorimetric detection. The AFB1 is almost completely removed within 120 min. Overall, the introduction of CHA improves the sensing sensitivity; efficient postcolorimetric-detection degradation of AFB1 reduces the secondary contamination and risk to the experimental environment and operators. This strategy is expected to provide ideas for designing other multifunctional platforms to integrate the detection and degradation of various hazards.

A magnetically reusable Ce-MOF/GO/Fe3O4 composite for effective photocatalytic degradation of chlortetracycline

Herein, we report a novel 1/GO/Fe3O4 photocatalyst, comprising Ce(BTB)(H2O) (MOF-1, H3BTB = 1,3,5-benzenetrisbenzoic acid), graphene oxide (GO), and iron oxide (Fe3O4) for photocatalytic degradation of chlortetracycline (CTC). This design enables the effective transfer of electrons from the MOF to GO, thereby reducing the photoelectron-hole recombination rate. Therefore, the optimized 1/GO/Fe3O4 photocatalyst with H2O2 shows the highest photocatalytic activity toward CTC. The kinetic constant is 5.4 times that in the system of MOF-1 and hydrogen peroxide, which usually acted as efficient electron acceptors to improve the photocatalytic performance of MOFs. More importantly, light absorption is extended from the ultraviolet to the visible region. Furthermore, 1/GO/Fe3O4 can be quickly recycled under an applied magnetic field and displays outstanding stability and reusability. According to the radical trapping experiments and electron paramagnetic resonance results, hydroxyl radicals, superoxide radicals, and holes all contribute to excellent photocatalytic activity. The possible catalytic mechanism of 1/GO/Fe3O4 is tentatively proposed. This work aims to explore the synergistic effect between metal-organic frameworks (MOFs) and GO, and provide a theoretical basis for MOF-based composites to remove antibiotic contaminants in the environment.

Coordination-Polymer-Derived Cu-CoO/C Nanocomposite Used in Fenton-like Reaction to Achieve Efficient Degradation of Organic Compounds

In this paper, carbon-matrix-supported copper (Cu) and cobaltous oxide (CoO) nanoparticles were obtained by using coordination polymers (CPs) as a precursor. The aqueous solutions of copper methacrylate (CuMA) and cobalt methacrylate (CoMA) were preferentially prepared, which were then mixed with anhydrous ethanol to fabricate dual metal ion coordination polymers (CuMA/CoMA). After calcination under an argon atmosphere, the Cu-CoO/C nanocomposite was obtained. Scanning electron microscope (SEM) and transmission electron microscope (TEM) showed that the material has banded morphology, and the dual functional nanoparticles were highly dispersed in the carbon matrix. The prepared material was used in a heterogeneous Fenton-like reaction, with the aim of replacing traditional ferric catalysts to solve pH constraints and the mass production of ferric slime. The obtained nanocomposite showed excellent catalytic performance on the degradation of methylene blue (MB) at near-neutral conditions; the discoloration efficiency is about 98.5% within 50 min in the presence of 0.15 mmol/mL H2O2 and 0.5 mg/mL catalyst. And good reusability was verified via eight cycles. The plausible pathway for MB discoloration and the possible catalytic mechanism was also proposed.

Coupling of the optimized electro-Fenton-like process with pulsed laser ablation method to produce bimetallic nanoparticles of Fe°/Cu° and Fe°/Zn° in treatment of thiophene aqueous samples

In this study, an electro-Fenton-like method in the presence of iron particles was used for degradation of toxic thiophene pollutant from aqueous samples with performance >99%. In an electrolytic reactor, the effect of current density, H2O2 dosage, and pH of the sample on the treatment efficiency was investigated and optimized using the response surface method in the experimental design methodology. The conditions were optimized in current density of 20 mA/cm2, H2O2 dosage 500 ppm and pH = 3.0. In this process, a laser pulse ablation was used to produce iron nanoparticles in the electro-Fenton reactor to decrease the treatment time. Also, two bimetallic iron-copper and iron-zinc were used to investigate the synergistic effect of bimetallic catalyst on degradation efficiency of thiophene. The removal of thiophene nearly 100% can be provided in the presence Fe0.5/Cu0.5, Fe0.5/Zn0.5 and Fe alone in 10, 15 and 20 min, respectively. Also, the effect of hydroxyl scavenger and the consumption of catalysts were studied in the proposed procedure. Techniques of gas chromatography-flame ionization detector (GC-FID), gas chromatography-sulphur chemiluminescence detector (GC-SCD) and total sulphur analyser were used to follow thiophene degradation. A thiophene petrochemical wastewater was treated by the proposed method, and the results showed a significant reduction in amounts of chemical oxygen demand (COD) and biochemical oxygen demand (BOD).

Synthesis of an efficient MOF catalyst for the degradation of OPDs using TPA derived from PET waste bottles

In this study, a method for degrading PET-waste plastic bottles using ZnCl2:Urea as a catalyst was developed, resulting in high conversion (87%). The terephthalic acid obtained from the degradation of Waste PET Bottles (WPTs) was combined with copper and zinc salts to synthesize bimetallic metal-organic frameworks (MOF). The effectiveness of a bimetallic Cu-Zn(BDC)-MOF in catalyzing the reduction reaction of organic pollutant dyes (OPDs) was investigated, and the degradation efficiency of individual dyes was optimized, achieving over 95% degradation within 6-12 min under optimal conditions. Various techniques, including FT-IR, XRD, FE-SEM, EDS, and TEM were used to characterize the synthesized MOF. Results showed that the catalytic activity of Cu-Zn-MOF in reduction reaction of OPDs was enhanced by increasing the copper content. The reaction kinetics were investigated following pseudo-first-order kinetics with rate constants of 0.581, 0.43, 0.37, and 0.30 min-1 for Methylene Blue (MB), Methyl Orange (MO), 4-Nitrophenol (4-NP), and 4-Nitroaniline (4-NA), respectively. The investigations revealed that the produced catalyst exhibited excellent stability and recoverability, while its activity remained well-preserved even after undergoing three reuse cycles.

One-pot synthesis of bimetallic Fe-Cu metal-organic frameworks composite for the elimination of organic pollutants via peroxymonosulphate activation

A series of bimetallic of FeCu metal-organic frameworks (MOFs) have been synthesised using a solvothermal process by varying the ratio between the two metals. Further, the bimetallic MOF catalysts were characterised by X-ray powder diffraction, scanning electron microscopy, and infrared spectroscopy techniques. Their catalytic properties for activation of peroxymonosulphate (PMS) have been tested by the removal of a model dye, rhodamine B. As a result, NH2-Fe2.4Cu1-MOF demonstrated the highest degradation, the effect of the ratio NH2-Fe2.4Cu1-MOF/PMS has been studied, and the main reactive species have been assessed. The application of these MOFs in powder form is difficult to handle in successive batch or flow systems. Thus, this study assessed the feasibility of growing NH2-Fe2,4Cu1-MOF on polyacrylonitrile (PAN) spheres using the one-pot solvothermal synthesis method. The optimisation of the catalytic activity of the synthesised composite (NH2-Fe2.4Cu1-MOF@PAN) has been evaluated by response surface methodology using a central composite face-centred experimental design matrix and selecting as independent variables: time, PMS concentration, and catalyst dosage. Based on the results, the optimisation of the operational conditions has been validated. At 2.5 mM PMS, 90 min, and 1.19 g·L-1 of catalyst dosage, maximum degradation (80.92%) has been achieved, which doubles the removal values obtained in previous studies with other MOFs. In addition, under these conditions, the catalyst has been proven to maintain its activity and stability for several cycles without activity loss.

Sulfur-decorated Fe/C composite synthesized from MIL-88A(Fe) for peroxymonosulfate activation towards tetracycline degradation: Multiple active sites and non-radical pathway dominated mechanism

Peroxymonosulfate (PMS)-mediated advanced oxidation processes gain growing attention in degrading antibiotics (e.g., tetracycline (TC)) in wastewater for their high capacity and relatively low cost, while designing efficient catalysts for PMS activation remains a challenge. In this study, a sulfur-doped Fe/C catalyst (Fe@C-S) synthesized from iron metal-organic frameworks (Fe-MOFs) was developed for PMS activation towards TC removal. Under optimal conditions, the TC removal efficiency of Fe@C-S150/PMS system within 40 min was 91.2%. Meanwhile, the k value for Fe@C-S150/PMS system (0.2038 min-1) was 3.36-fold as high as the S-free Fe@C-based PMS system. Also, Fe@C-S150/PMS system showed high robustness in different water matrices. Further studies found that the TC degradation mechanism was mainly ascribed to the non-radical pathway (1O2 and electron transfer). Fe nanoparticles, S and CO groups on the catalyst all participated in the generation of reactive oxygen species (ROS). Besides, S species could enhance the Fe2+/Fe3+ redox cycle and accelerate the electron transfer process. This work highlights the critical role of S in enhancing the catalytic performance of Fe/C-based catalysts for PMS activation, which would provide meaningful insights into the design of high-performance PMS activators for the sustainable remediation of emerging contaminants-polluted water bodies.

Heterogeneous-Driven Glutathione Oxidation: Defining the Catalytic Role of Chalcopyrite Nanoparticles

Transition-metal nanocatalysis represents a novel alternative currently experiencing flourishing progress to tackle the tumor microenvironment (TME) in cancer therapy. These nanomaterials aim at attacking tumor cells using the intrinsic selectivity of inorganic catalysts. In addition, special attention to tune and control the release of these transition metals is also required. Understanding the chemical reactions behind the catalytic action of the transition-metal nanocatalysts and preventing potential undesired side reactions caused by acute cytotoxicity of the released ionic species represent another important field of research. Specifically, copper-based oxides may suffer from acute leaching that potentially may induce toxicity not only to target cancer cells but also to nearby cells and tissues. In this work, we propose the synthesis of chalcopyrite (CuFeS₂) nanostructures capable of triggering two key reactions for an effective chemodynamic therapy (CDT) in the heterogeneous phase: (i) glutathione (GSH) oxidation and (ii) oxidation of organic substrates using H₂O₂, with negligible leaching of metals under TME-like conditions. This represents an appealing alternative toward the development of safer copper-iron-based nanocatalytic materials with an active catalytic response without incurring leaching side phenomena.

Effects and Mechanisms of Cu Species in Fe-MOFs on Fenton-Like Catalytic Activity and Stability

Fe-based MOFs (Fe-MOFs) are deemed promising Fenton-like catalysts due to their well-developed pores and accessible active sites. However, their inferior catalytic activity, iron leaching, and low H₂O₂ utilization always hinder their application as Fe-based MOF catalysts. In this work, we manipulated the structure of Fe-oxo nodes in MIL-88B(Fe) via a Cu^I species substitution method, affording a mixed-valence (Cu-incorporated Fe-MOFs) with highly improved Fenton-like performance. It is found that the Cu^I serves as a shuttle to promote transfer between Fe^II/Fe^III, inducing the formation of a larger amount of stable Fe^II sites, which was proven by experimental and DFT calculation results. A linear relationship was observed for the Fenton-like performance and the amount of Cu^I species for the catalysts. The corresponding value of the ^•OH formation is 2.17 eV for Cu-incorporated MIL-88B(Fe), which is significantly lower than that of MIL-88B(Fe) (2.69 eV). Meanwhile, the enriched Cu^I species suppress Fe species leaching during the catalytic reaction. The Fe-ion leakage of 0.4Cu@MIL-88B is very tiny (0.01-0.03 mg/L), significantly less than that of MIL-88B (2.00-3.02 mg/L). At the same time, H₂O₂ utilization for 0.4Cu@ MIL-88B(Fe) is 88%, which is almost 4.4 times that of pure MIL-88B(Fe). This work provides insights into the rational design of Fe-MOFs as promising Fenton-like catalysts for wastewater treatment.

Fe-Cu bimetal metal-organic framework for efficient decontamination via Fenton-like process: Synthesis, performance and mechanism

Constructing Fe-Cu bimetal catalysts is an efficient strategy to promote Fe(III)/Fe(II) cycle, whereas there is still a long way to go before fully understanding the role of the Cu in the catalysts. Herein, a new Fe-MOF namely BUC-96(Fe) was fabricated from FeSO₄·7H₂O, 4,4'-bipyridine (bpy) and 2,5-dihydroxyterephthalic acid (H₄dhtp) by both hydrothermal reaction and microwave-assisted method. Also, bimetal BUC-96(FeCu-x) were obtained when the CuSO₄ was added into the system identical to the synthesis process of BUC-96(Fe). Series BUC-96 MOFs showed good organics elimination performance via Fenton-like process, where 88.1% (k = 0.0672 min^-1) of chloroquine phosphate (CQ, 20 mg/L) was decomposed over pristine BUC-96(Fe) within 30 min. Interestingly, nearly 100% CQ was degraded over BUC-96(FeCu-5) as catalyst under the identical conditions within 5 min, whose reaction rate (1.3527 min^-1) was 20.1-fold higher than that of BUC-96. Additionally, BUC-96(FeCu-5) exhibited excellent Fenton-like oxidation degradation performance for 10 selected emerging organic pollutants. The reaction mechanism was studied in detail by experiments, and density functional theory (DFT) calculation. The results revealed that the introduced Cu not only accelerated Fe(III)/Fe(II) cycles, hydroxyl radical (·OH) generation, electron transfer, but also lowered H₂O₂ dissociated energy barrier. This work advanced the bimetal MOFs construction and application in wastewater treatment via Fenton-like process.

Heterogeneous Fenton system driven by iron-loaded sludge biochar for sulfamethoxazole-containing wastewater treatment

In this study, the treatment performance of a heterogeneous Fenton system (Fe-BC + H₂O₂) driven by iron-loaded sludge biochar (Fe-BC) on wastewater containing sulfamethoxazole (SMX) was investigated using the CODcr removal efficiency (φ) as an indicator. The batch experimental results showed that the optimal operating conditions were as follow: initial pH 3, H₂O₂ concentration 20 mmol L^-1, Fe-BC dose 1.2 g L^-1, temperature 298 K. The corresponding φ was as high as 83.43%. The removal of CODcr was better described by BMG model and revised BMG (BMGL) model. According to the BMGL model, the φ_max could be 98.37% (298 K). Moreover, the removal of CODcr was a diffusion-controlled process, while liquid film diffusion and intraparticle diffusion together determined its removal rate. The removal of CODcr should be a synergistic effect of adsorption and Fenton oxidation (real heterogeneous Fenton and homogeneous Fenton) and other pathways. Their contributions were 42.79%, 54.01% and 3.20%, respectively. For homogeneous Fenton, there seemed to be two simultaneous SMX degradation pathways: SMX→4-(pyrrolidine-11-sulfonyl)-aniline→N-(4-aminobenzenesulfonyl) acetamide/4-amino-N-ethyl benzene sulfonamides→4-amino-N-hydroxy benzene sulfonamides; SMX→N-ethyl-3-amino benzene sulfonamides→4-methanesulfonylaniline. In summary, Fe-BC had potential for practical application as a heterogeneous Fenton catalyst.

Selective and effective oxidation of ammonium to dinitrogen in MgO/Na2SO3/K2S2O8 system

The oxidation of ammonium (NH₄⁺) to dinitrogen (N₂) with high selectivity and high efficiency is still a challenge. Herein, a novel sunlight induced persulfate (PS)-based AOPs process (MgO/Na₂SO₃/PS/hv) was proposed by introducing solid base (MgO) and hydrated electron (e_aq^-), to selectively oxidize NH₄⁺ to N₂, with high selectivity and high efficiency at a wide range of pH value. The deprotonation of NH₄⁺ into NH₃ by MgO and the generation of •OH and SO₄^-• by PS activation were responsible for the high efficiency of NH₄⁺ oxidation. The buffering capacity provided by MgO to proton released from PS activation made the NH₄⁺ oxidation possible at a wide pH range. The e_aq^- from the Na₂SO₃/hv process was the main active specie to reduce NO₂^-and NO₃^- (NO_x^-) into N₂, responsible for high N₂ selectivity of NH₄⁺ oxidation. 100% NH₄⁺ could be oxidized within 30 min, and N₂ selectivity exceeded 96% at the initial pH range of 3-11 and the initial concentration of NH₄⁺ of 30 mg N/L. This work could offer an efficient AOPs process for selective NH₄⁺ oxidation, which is promising for the chemical denitrification of wastewater ….

Facile preparation of pH-sensitive biocompatible alginate beads havening layered double hydroxide supported metal-organic framework for controlled release from doxorubicin to breast cancer cells

In the present study, a pH-sensitive controlled drug delivery system was prepared from alginate beads impregnated with AlCu layered double hydroxides (LDH) supported copper metal-organic framework (Alg-DOX-Cu MOF-LDH beads) for controlled release from doxorubicin (DOX) to breast cancer cells. The physicochemical properties of Alg-DOX-Cu MOF-LDH beads were determined by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FE-SEM), and Zeta potential. The in vitro release studies showed that the Alg-DOX-Cu MOF-LDH beads had more controlled drug release than the DOX-Cu MOF-LDH and in vitro release of DOX from both carriers showed pH-response release behavior. The kinetic adsorption studies also confirmed that the drug release from the DOX-Cu MOF-LDH and Alg-DOX-Cu MOF-LDH beads well obey the Korsmeyer-Peppas model. Meanwhile, in vitro cytotoxicity and DAPI tests on L929 (non-cancerous cells) and MCF-7 (human breast cancer cells) clearly showed that the prepared AlCu LDH and Cu MOF-LDH systems had good biocompatibility. Whereas, Alg-DOX-Cu MOF-LDH beads had higher cytotoxicity effects as a result of the controlled release of DOX to MCF-7 cells. These results suggested that the Alg-DOX-Cu MOF-LDH beads can be used as an excellent drug delivery system for cancer therapy and other biomedical applications.

Defective iron based metal-organic frameworks derived from zero-valent iron for highly efficient fenton-like catalysis

Introducing crystal defects into iron based metal-organic frameworks (Fe-MOFs) is regarded as a promising strategy to enhance Fenton-like performance. However, developing a facile and effective strategy to construct defective Fe-MOFs as highly efficient Fenton-like catalyst is still a challenge. Herein, MIL-100(Fe) (Def-MIL-100(Fe)) with missing ligands defects was synthesized by a simple heterogeneous reaction using zero-valent iron. The bisphenol A degradation efficiency in the Def-MIL-100(Fe)/H₂O₂ system reached up to 91.26% within 10 min at pH 4 with a low catalyst dosage of 0.05 g/L, while the perfect MIL-100(Fe) has almost no Fenton-like performance. It was observed that missing ligands defects in the Def-MIL-100(Fe) play a key role in the Fenton-like reaction. The missing ligands defects could increase the Lewis acidity for fast H₂O₂ adsorption and accelerate the electron transfer between Fe^II and Fe^III cycling, leading to faster and more·OH generation. Moreover, the missing ligands defects could promote the mass transfer for improving·OH utilization efficiency. This work provides a novel strategy to construct defective Fe-MOFs as highly efficient Fenton-like catalyst to degrade organic pollutants in water.

Photocatalytic degradation of tetracycline antibiotic and organic dyes using biogenic synthesized CuO/Fe2O3 nanocomposite: pathways and mechanism insights

Tetracycline (TC) is a frequently administered antibiotic in many countries, due to its low price and excellent potency. However, certain antibiotics can be hazardous to living creatures due to their accumulation by complexation with metal ions which can contribute to teratogenicity and carcinogenicity. In this investigation, copper oxide-ferric oxide nanocomposite (CuO/Fe₂O₃ nanocomposite) was synthesized employing Psidium guajava (P. guajava) leaf extract as a reductant as well as a capping agent in an environment friendly and economical green synthesis method. The as-synthesized CuO/Fe₂O₃ nanocomposite was comprehensively characterized using various sophisticated techniques and its efficiency as a photocatalyst for degradation of tetracycline (TC) antibiotic and toxic dyes, i.e., rhodamine B (RhB) and methylene blue (MB) were investigated. The CuO/Fe₂O₃ nanocomposite exhibited exceptional efficiency for degradation of TC antibiotic (88% removal in 80 min), RhB (96% removal in 40 min), and MB (93% elimination in 40 min) with apparent rate constant of 0.048, 0.068, and 0.032 min^-1, respectively. In the degradation experiments, photocatalytic activity of CuO/Fe₂O₃ nanocomposite was studied by varying different factors such as time of contact, catalyst dose, and solution pH. The role of reactive species in antibiotics and dye degradation was validated by radical scavenging studies which indicated that^.OH radical played a critical role in photocatalytic decomposition. Furthermore, liquid chromatography-mass spectrometry (LC-MS) investigations were employed to anticipate a plausible mechanism for TC degradation.

Catalytic Micromotors as Self-stirring Microreactors for Efficient Dual-mode Colorimetric Detection

A catalytic micromotor-based (MIL-88B@Fe₃O₄) colorimetric detection system which exhibit rapid color reaction for quantitative colorimetry and high-throughput testing for qualitative colorimetry have been successfully developed. Taking the advantages of the micromotor with dual roles (micro-rotor and micro-catalyst), under rotating magnetic field, each micromotor represents a microreactor which have micro-rotor for microenvironment stirring and micro-catalyst for the color reaction. Numerous self-string micro-reactions rapidly catalyze the substance and show the corresponding color for the spectroscopy testing and analysis. Additionally, owing to the tiny motor can rotate and catalyze within microdroplet, a high-throughput visual colorimetric detection system with 48 micro-wells has been innovatively conducted. The system enables up to 48 microdroplet reactions based on micromotors run simultaneously under the rotating magnetic field. Multi-substance, including their species difference and concentration strength, can be easily and efficiently identified by observing the color difference of the droplet with naked eye after just one test. This novel catalytic MOF-based micromotor with attractive rotational motion and excellent catalytic performance not only endowed a new nanotechnology to colorimetry, but also shows hold great potentials in other fields, such as refined production, biomedical analysis, environmental governance etc., since such micromotor-based microreactor can be easily applied to other chemical microreactions.

Bimetal-organic framework/GOx-based hydrogel dressings with antibacterial and inflammatory modulation for wound healing

Antibiotic resistance of bacteria and persistent inflammation are critical challenges in treating bacteria infected wounds. Thus, it is urgent to develop versatile wound dressings that possess high-efficiency antibacterial performance and inflammation regulation. Herein, we have successfully constructed a hydrogel wound dressing consisting of the bimetallic metal-organic framework (MOF) loaded with glucose oxidase (GOx), termed as MOF(Fe-Cu)/GOx-polyacrylamide (PAM) gel. Hydrogel dressings can provide an efficient cascade-catalyzed system to accelerate wound healing via synergistic antibacterial and inflammatory modulation. Importantly, the catalytic property of the bimetallic MOF(Fe-Cu) is about five times that of the monometallic MOF(Fe). Based on such a cascade-catalyzed system, the abundant gluconic acid and H₂O₂ can be continuously produced by decomposing glucose via GOx. Such gluconic acid can notably improve the peroxidase performance of MOF(Fe-Cu), which can further efficiently decompose H₂O₂ to achieve the antibacterial. Meanwhile, MOF (Fe Cu)/GOx PAM gel can induce macrophages to change into an M2 phenotype, which can accelerate the transformation of the wound microenvironment to a remodeling state and then accelerate angiogenesis and neurogenesis. This work provides multifunctional bioactive materials for accelerating wound healing and will have great potential in clinical applications. STATEMENT OF SIGNIFICANCE: Antibiotic resistance and persistent inflammation are still the critical reasons for the slow healing of bacteria infected wounds. Herein, we prepared a hydrogel wound dressing composed of bimetallic metal organic framework (MOF) loaded with glucose oxidase (GOx). The catalytic activity of the bimetallic MOF(Fe-Cu) is significantly enhanced due to doping of copper, which makes it possess outstanding antibacterial ability based on cascade catalysis. Such dressing can promote the remodeling of inflammatory immunity by regulating macrophage polarization to suppress over-reactive inflammation, further accelerating the healing of bacteria-infected wounds. This study provides an innovative and effective way to accelerate the healing of bacteria infected wound by combining bacteria killing and inflammation modulation.

Rapidly and ultra-sensitive colorimetric detection of H2O2 and glucose based on ferrous-metal organic framework with enhanced peroxidase-mimicking activity

In this article, a novel metal-organic framework, namely MIL-101(Fe^II), was firstly synthesized via a facile method. In the presence of H₂O₂, MIL-101(Fe^II) possesses excellent peroxidase-like activity toward the classical chromogenic substrate, N,N-Diethyl-p-phenylenediamine sulfate salt (DPD). The substitution of Fe²⁺ enhances the construction of Fe(II)-oxo nodes and accelerates electrons transfer between DPD and H₂O₂, thereby improving the peroxidase-mimicking catalytic activity of MIL-101(Fe^II) nanoenzyme. Additionally, DPD molecules could be adsorbed readily onto the surface of the nanoparticles due to the π-π interaction. The study of Michaelis constant indicates that the MIL-101(Fe^II) exhibits a higher affinity towards DPD (0.16 mM) in contrast to horseradish peroxidase (0.78 mM). In view of the impressive catalytic performance of MIL-101(Fe^II), two reliable monitoring platforms for the rapid detection of H₂O₂ and glucose were established with extremely low detection limits of 18.04 nM and 0.87 μM in the ranges of 40-5000 nM and 1.2-300 μM, respectively. The study of the catalytic mechanism indicates that DPD oxidation is attributed to the hydroxyl radical (·OH) produced from the decomposition of H₂O₂ catalyzed by MIL-101(Fe^II). Furthermore, the developed sensor indicates high selectivity and stability and can be effectively appropriate for the detection of H₂O₂ and glucose in real samples. This work not only provides a novel nanozyme with superior catalytic performance for biological analysis, but also broadens the application field of MIL-101(Fe^II) material.

Recent Advances in the Development of Novel Iron–Copper Bimetallic Photo Fenton Catalysts

Advanced oxidation processes (AOPs) have been postulated as viable, innovative, and efficient technologies for the removal of pollutants from water bodies. Among AOPs, photo-Fenton processes have been shown to be effective for the degradation of various types of organic compounds in industrial wastewater. Monometallic iron catalysts are limited in practical applications due to their low catalytic activity, poor stability, and recyclability. On the other hand, the development of catalysts based on copper oxides has become a current research topic due to their advantages such as strong light absorption, high mobility of charge carriers, low environmental toxicity, long-term stability, and low production cost. For these reasons, great efforts have been made to improve the practical applications of heterogeneous catalysts, and the bimetallic iron–copper materials have become a focus of research. In this context, this review focuses on the compilation of the most relevant studies on the recent progress in the application of bimetallic iron–copper materials in heterogeneous photo–Fenton-like reactions for the degradation of pollutants in wastewater. Special attention is paid to the removal efficiencies obtained and the reaction mechanisms involved in the photo–Fenton treatments with the different catalysts.

Degradation of lomefloxacin by MoS2/MIL-53(Fe, Cu) catalyst in heterogeneous electro-Fenton process

A novel heterogeneous catalyst named MoS₂/MIL-53(Fe, Cu) (MMFC) was prepared by hydrothermal method and applied in a heterogeneous electro-Fenton (hetero-EF) system for lomefloxacin (LOM) degradation in this work. Under the optimal conditions of current density 3 mA/cm², catalyst dosage 0.100 g/L, and initial pH 6, 93.5% LOM (2 mg/L) removal efficiency was achieved in the MMFC hetero-EF system within 60 min, indicating an obvious improvement compared with the MIL-53(Fe, Cu) hetero-EF system. The good catalytic activity was attributed to more effective active sites of the catalyst and the conversion of Fe(II)/Fe(III) and Cu(I)/Cu(II) promoted by Mo(IV) in MoS₂, which could be inferred by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) characterizations. The reusability and stability of MMFC were explored based on five cyclic experiments, and the average degradation efficiency reached 73.9%. Furthermore, the hetero-EF system could achieve the total removal of moxifloxacin and tetracycline within 6 min and 40 min, respectively. Quenching experiments revealed that the hydroxyl radicals (·OH) were the main reactive radicals while superoxide radicals (·O₂^-) and singlet oxygen (¹O₂) played a certain part in LOM degradation. Finally, the possible mechanism of the hetero-EF process and LOM degradation pathways were proposed, including substitution, elimination, and cleavage of ring structures. Accounting for good catalytic performance, low preparation cost, and satisfactory versatility, the MMFC exhibited good potential to work as a hetero-EF catalyst for wastewater treatment.

Preparation of copper-based catalysts from electroplating sludge by ultrasound treatment and their antibiotic degradation performance

The recovery of heavy metals from electroplating sludge is important for alleviating heavy metal pollution and recycling metal resources. However, the selective recovery of metal resources is limited by the complexity of electroplating sludge. Herein, CuFe bimetallic Fenton-like catalysts were successfully prepared from electroplating sludge by a facile room-temperature ultrasonic-assisted co-precipitation method. The prepared CuFe-S mainly consisted of nanorods with diameters of 20-30 nm and lengths of 100-200 nm and a small number of irregular particles. Subsequently, we performed tetracycline (TC) degradation experiments, and the results showed that the product CuFe-S had very good performance over a wide pH range (2-11). At an initial pH = 2, CuFe-S could degrade 91.9% of 50 mg L^-1 TC aqueous solution within 30 min, which is better than that of a single metal catalyst. Free radical scavenging experiments and electron paramagnetic resonance (EPR) tests revealed that ·OH was the main active species for the degradation of TC by CuFe-S. In conclusion, a CuFe bimetallic Fenton-like catalyst was developed for the catalytic degradation of antibiotics, which provides a novel technical route for the resource utilization of electroplating sludge and shows an important practical application prospect.

Highly Sensitive Colorimetric Detection of Glutathione in Human Serum Based on Iron-Copper Metal-Organic Frameworks

Emerging metal-organic framework (MOF)-based mimic enzymes have been exploited to design a colorimetric sensor for the detection of biomolecules. However, it is challenging to figure out the glutathione (GSH) detection method and the corresponding sensing mechanism using an MOF-based colorimetric sensor. In this work, a novel iron-copper MOF with high activity is synthesized by a wet-chemical method. A GSH colorimetric sensor based on the peroxidase-like properties of the iron-copper MOF is developed. Hydrogen peroxide is converted to hydroxyl radicals by the peroxidase-like properties of the iron-copper MOF mimic enzyme, which can catalyze the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized TMB (ox-TMB). The kinetic constant of the MOF mimic enzyme (0.02 mM for H₂O₂) is superior to horseradish peroxidase (HRP). The GSH content can be quantified by proposing a sensor based on the colorimetric method and color turn-off mechanism. The turn-off mechanism of GSH analysis includes two aspects. On the one hand, the blue ox-TMB can be deoxidized to colorless TMB by GSH. On the other hand, hydroxyl radicals (^•OH) can be consumed by GSH. The linear range and limit of detection are 2-20 and 0.439 μM, respectively. At the same time, GSH detection also shows good specificity and anti-interference characteristics. Therefore, MOF-based colorimetric sensors have been used to qualitatively and quantitatively measure GSH contents in human serum. The mechanism and application of the iron-copper MOF pave a way for the development of mimic enzymes with polymetallic active sites in the field of colorimetric sensing.

Inclusion of bimetallic Fe0.75Cu0.25-BDC MOFs into Alginate-MoO3/GO as a novel nanohybrid for adsorptive removal of hexavalent chromium from water

Metal-organic frameworks (MOFs) as porous materials have recently attracted research works in removal of toxic pollutants from water. Cr(VI) is well-known as one of the most toxic forms of chromium and the selection of efficient and effective Cr(VI)-remediation technology must be focused on a number of important parameters. Therefore, the objective of this work is to fabricate a novel nanohybrid adsorbent for removal of Cr(VI) by using assembled bimetallic MOFs (Fe_0.75Cu_0.25-BDC)-bound- Alginate-MoO₃/Graphene oxide (Alg-MoO₃/GO) via simple solvothermal process. The aimed Fe_0.75Cu_0.25-BDC@Alg-MoO₃/GO nanohybrid was confirmed by FTIR, SEM, TEM, XRD and TGA. Adsorptive extraction of Cr(VI) from aqueous solution was aimed by various optimized experimental parameters providing optimum pH = 3, dosage = 5-10 mg, starting concentration of Cr(VI) = 5-15 mg L^-1, shaking time = 5-10 min. The point of zero charge (pH_Pzc) was 3.8. For Cr(VI) removal by Fe_0.75Cu_0.25-BDC@Alg-MoO₃/GO, four isotherm models were estimated: Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) with calculated correlation coefficient (R² = 0.9934) for Langmuir model which was higher than others. The collected results from the kinetic study clarified that pseudo-second order model is the most convenient one for describing the adsorption behavior of Cr(VI) and therefore, the adsorption process was suggested to rely on a chemisorption mechanism. Thermodynamic parameters referred that the adsorption mechanism is based on a spontaneous and exothermic process. Finally, the emerged Fe_0.75Cu_0.25-BDC@Alg-MoO₃/GO nanohybrid was confirmed as an effective adsorbent for extraction of hexavalent chromium from real water specimens (tap, sea water and wastewater) with percentage recovery values > 98%.

Artificial microbial consortium producing oxidases enhanced the biotransformation efficiencies of multi-antibiotics

Antibiotic mixtures in the environment result in the development of bacterial strains with resistance against multiple antibiotics. Oxidases are versatile that can bio-remove antibiotics. Various laccases (LACs), manganese peroxidases (MNPs), and versatile peroxidase (VP) were reconstructed in Pichia pastoris. For the single antibiotics, over 95.0% sulfamethoxazole within 48 h, tetracycline, oxytetracycline, and norfloxacin within 96 h were bio-removed by recombinant VP with α-signal peptide, respectively. In a mixture of the four antibiotics, 80.2% tetracycline and 95.6% oxytetracycline were bio-removed by recombinant MNP2 with native signal peptide (NSP) within 8 h, whereas < 80.0% sulfamethoxazole was bio-removed within 72 h, indicating that signal peptides significantly impacted removal efficiencies of antibiotic mixtures. Regarding mediators for LACs, 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) resulted in better removal efficiencies of multi-antibiotic mixtures than 1-hydroxybenzotriazole or syringaldehyde. Furthermore, artificial microbial consortia (AMC) producing LAC2 and MNP2 with NSP significantly improved bio-removal efficiency of sulfamethoxazole (95.5%) in four-antibiotic mixtures within 48 h. Tetracycline and oxytetracycline were completely bio-removed by AMC within 48 and 72 h, respectively, indicating that AMC accelerated sulfamethoxazole, tetracycline, and oxytetracycline bio-removals. Additionally, transformation pathways of each antibiotic by recombinant oxidases were proposed. Taken together, this work provides a new strategy to simultaneously remove antibiotic mixtures by AMC.

Heterogeneous Fenton degradation of persistent organic pollutants using natural chalcopyrite: effect of water matrix and catalytic mechanism

Natural chalcopyrite was evaluated as heterogeneous Fenton catalyst. Catalytic performance was evaluated considering different systems, catalyst dosage, H2O2 concentration, and reaction temperature, and increasing the parameters favors rhodamine B degradation. Effect of aqueous matrix was systematically examined, involving solution pH, anions, cations, dissolved organic matter, and initial pollutant concentration. The degradation performance is slightly influenced by these parameters. Rhodamine B removal is 96.5% within 120 min, the rate constant ranges from 0.0086 min-1 to 0.0415 min-1 depending on temperature, and the activation energy is 79 kJ/mol. Effective degradation of different persistent organic pollutants including methylene blue, malachite green, sodium butyl xanthate, tetracycline, and p-nitrophenol is verified by UV-vis spectra. Natural chalcopyrite was characterized by advanced techniques including scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Reactions between chalcopyrite and H2O2 cause copper leaching and iron oxidation. Quenching experiments and electron paramagnetic resonance reveal the dominant role of hydroxyl radical in catalytic process. The catalytic mechanism induced by surface iron and leached copper derived from chalcopyrite is proposed.

Strategies for improving the catalytic activity of metal-organic frameworks and derivatives in SR-AOPs: Facing emerging environmental pollutants

As persulfate activator, Metal organic frameworks (MOFs) and derivatives are widely concerned in degradation of emerging environmental pollutants by advanced oxygen technology dominated by sulfate radical () (SR-AOPs). However, the poor stability and low catalytic efficiency limit the performance of MOFs, requiring multiple strategies to further enhance their catalytic activity. The aim of this paper is to improve the catalytic activity of MOFs and their derivatives by physical and chemical enhancement strategies. Physical enhancement strategies mainly refer to the activation strategies including thermal activation, microwave activation and photoactivation. However, the physical enhancement strategies need energy consumption and require high stability of MOFs. As a substitute, chemical enhancement strategies are more widely used and represented by optimization, modification, composites and derivatives. In addition, the identification of reactive oxygen species, active site and electron distribution are important for distinguishing radical and non-radical pathways. Finally, as a new wastewater treatment technology exploration of unknown areas in SR-AOPs could better promote the technology development.

Cu/Fe oxide integrated on graphite felt for degradation of sulfamethoxazole in the heterogeneous electro-Fenton process under near-neutral conditions

In the heterogeneous electro-Fenton (EF) system, high-efficiency and durable materials have attracted widespread attention as cathodes for degradation of refractory organic pollutants. In this study, a stable Cu/Fe oxide modified graphite felt electrode (Cu_0.33Fe_0.67NBDC-300/GF) was fabricated via a one-step hydrothermal method and subsequent thermal treatment, which used a bimetallic metal-organic framework (MOF) with 2-aminoterephthalic acid (NH₂BDC) ligand as the precursor. The Cu_0.33Fe_0.67NBDC-300/GF electrode was used as the cathode for sulfamethoxazole (SMX) degradation in the heterogeneous EF process. The coexistence of the Fe^II/Fe^III and Cu^I/Cu^II redox couples significantly accelerates the regeneration of Fe^II and promotes the generation of active free radicals (•OH and •O₂^-). Fe^IV was detected during the process, which indicates that the high-valent iron-oxo species was produced in near-neutral pH conditions. The removal efficiency of SMX (10 mg L^-1) can reach 100.0% within 75 min over a wide pH range (4.0-9.0). After five cycles, the electrode retained a high stability and an outstanding catalytic capacity. Furthermore, the mechanisms and pathways for SMX degradation were proposed, the products and intermediates of SMX were analyzed, and the toxicity was evaluated. It was found that the toxicity decreased after degradation. This study displays a novel strategy for building an efficient and stable self-supporting electrode for treating antibiotic wastewater.

Heterogeneous Advanced Oxidation Processes: Current Approaches for Wastewater Treatment

Nowadays, water pollution is one of the most dangerous environmental problems in the world. The presence of the so-called emerging pollutants in the different water bodies, impossible to eliminate through conventional biological and physical treatments used in wastewater treatment plants due to their persistent and recalcitrant nature, means that pollution continues growing throughout the world. The presence of these emerging pollutants involves serious risks to human and animal health for aquatic and terrestrial organisms. Therefore, in recent years, advanced oxidation processes (AOPs) have been postulated as a viable, innovative and efficient technology for the elimination of these types of compounds from water bodies. The oxidation/reduction reactions triggered in most of these processes require a suitable catalyst. The most recent research focuses on the use and development of different types of heterogeneous catalysts, which are capable of overcoming some of the operational limitations of homogeneous processes such as the generation of metallic sludge, difficult separation of treated water and narrow working pH. This review details the current advances in the field of heterogeneous AOPs, Fenton processes and photocatalysts for the removal of different types of emerging pollutants.