Fe-based Metal-organic Frameworks Research Articles

Synthesis of Double MOFs composite material for visible light photocatalytic degradation of tetracycline

In this paper, the Co-MIL-53(Fe)–NH2/UIO-66-NH2 (CoMU) Hybrid materials with Ⅱ-type heterojunction was synthesized through hydrothermal reaction. Compared with the degradation of tetracycline (TC) by monomer materials, CoMU has the highest photocatalytic degradation efficiency, which can reach a degradation equilibrium within 8 min. As a typical Ⅱ-based MOFs (Metal organic frameworks) material, UIO-66-NH2 can effectively promote the separation and transfer of photoelectric carriers. The introduction of cobalt ions in Fe-based MOFs materials further promoted the transfer of charges through the continuous oxidation-reduction reaction of Co3+/Co2+. The performance of CoMU is explored by studying the influence of TC concentration, pH value, different PMS dosage and different water bodies on the experiment. Active radical capture experiments show that H+ and ·O2− play a major role in the degradation of TC. In addition, based on the analysis of experimental results, a possible photocatalytic mechanism was discussed. Our results provide insight into the design and construction of high-efficiency hybrid photocatalysts combined with MOFs materials to enhance photocatalytic activity for the photodegradation of environmental pollutants.

Nano-Porous Composites of Activated Carbon–Metal Organic Frameworks (Fe-BDC@AC) for Rapid Removal of Cr (VI): Synthesis, Adsorption, Mechanism, and Kinetics Studies

Metal–organic frameworks (MOFs) are a group of porous materials that display potential in the elimination of toxic industrial compounds (TICs) from polluted water streams. However, their applications have so far been held up by issues due to their physical nature and cost. In this study, activated carbon (AC) is modified with an Fe-based MOF, iron terephthalate (Fe-BDC). A facile and cost-effective impregnation method is used for enhanced removal from aqueous solutions. The new adsorbent is characterized by SEM, FTIR, PXRD, and BET. The composite displays excellent uptake of Cr (VI) when compared to un-impregnated AC with a maximum monolayer adsorption capacity of 100 mg·g−1. The experimental data shows a high correlation to the Langmuir adsorption model. The adsorption kinetic study reveals that the adsorption of Cr (VI) to Fe-BDC@AC obeys the pseudo-first-order equation. The composite shows high reusability after five cycles and high adsorption rates reaching equilibrium in just 50 min. Such properties make the nanocomposite promising for water decontamination on larger scales compared to powder-based alternatives, such as individual MOF crystals.

Efficient Visible-Light Photoreduction of CO2 to CH4 over an Fe-Based Metal–Organic Framework (PCN-250-Fe3) in a Solid–Gas Mode

Efficient Visible-Light Photoreduction of CO₂ to CH₄ over an Fe-Based Metal–Organic Framework (PCN-250-Fe₃) in a Solid–Gas Mode

Preparation of Fe3O4@SW-MIL-101-NH2 for selective pre-concentration of chlorogenic acid metabolites in rat plasma, urine, and feces samples

An innovative sandwich-structural Fe-based metal-organic framework magnetic material (Fe3O4@SW-MIL-101-NH2) was fabricated using a facile solvothermal method. The characteristic properties of the material were investigated by field emission scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, vibrating sample magnetometry, and Brunauer-Emmett-Teller measurements. Fe3O4@SW-MIL-101-NH2 is associated with advantages, such as robust magnetic properties, high specific surface area, and satisfactory storage stability, as well as good selective recognition ability for chlorogenic acid (CA) and its metabolites via chelation, hydrogen bonding, and π-interaction. The results of the static adsorption experiment indicated that Fe3O4@SW-MIL-101-NH2 possessed a high adsorption capacity toward CA and its isomers, cryptochlorogenic acid (CCA) and neochlorogenic acid (NCA), and the adsorption behaviors were fitted using the Langmuir adsorption isotherm model. Then, a strategy using magnetic solid-phase extraction (MSPE) and ultra-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF MS/MS) was developed and successfully employed for the selective pre-concentration and rapid identification of CA metabolites in rat plasma, urine, and feces samples. This work presents a prospective strategy for the synthesis of magnetic adsorbents and the high-efficiency pretreatment of CA metabolites.

Efficient photo-Fenton degradation performance, mechanism, and pathways of tetracycline hydrochloride over missing-linker metal–organic framework with mix-valence coordinatively unsaturated metal sites

Photo-Fenton performance of Fe-based metal–organic frameworks needs to be further improved owing to little coordinatively unsaturated metal sites (Lewis acid sites) and poor photogenerated carrier separation and migration efficiency. In view of this problem, this work has developed missing-linker metal–organic framework with mix-valence coordinatively unsaturated metal site (abbreviated as CUS-Pac-MIL-100 (Fe)) for photo-Fenton degradation by thermal activation and introducing missing linker. The structure of catalysts was characterized by SEM, XRD, XPS, in-situ DRIFT, TG, BET, and EPR, which proves abundant mixed-valence coordinatively unsaturated metal sites are introduced by vacuum thermal activation and plenty of ligand vacancies are introduced by missing-linker. The conditions for TC-HCl degradation were optimized. The results indicate that CUS-Pac-MIL-100 (Fe) exhibits remarkable removal rate of TC-HCl within 80 min at 10 mL/L H2O2 dosage, 0.2 g/L catalyst dosage, and a wide pH range (4.0–7.0). The total organic carbon (TOC) removal rate also reaches 52.3% within 80 min. Such remarkable improvement in the photo-Fenton activity is attributed to the mix-valence coordinatively unsaturated metal sites improving the adsorption and activation ability of H2O2, and the ligand vacancies promoting the separation efficiency of carriers to accelerate Fe2+ regeneration. The catalyst also exhibits excellent cyclability and stability after multiple cycles. Further, the degradation mechanism and degradation pathways of TC-HCl in the photo-Fenton reaction has been proposed on the basis of radical quenching, electron paramagnetic resonance, and LC-MS tests. This work provides a worthy insight for the construction of high-efficiency MOF-based photo-Fenton materials.

Anti-VEGFR2-labeled enzyme-immobilized metal-organic frameworks for tumor vasculature targeted catalytic therapy

Tumor vasculature-targeting therapy either using angiogenesis inhibitors or vascular disrupting agents offers an important new avenue for cancer therapy. In this work, a tumor-specific catalytic nanomedicine for enhanced tumor ablation accompanied with tumor vasculature disruption and angiogenesis inhibition was developed through a cascade reaction with enzyme glucose oxidase (GOD) modified on Fe-based metal organic framework (Fe-MOF) coupled with anti-VEGFR2.The GOD enzyme could catalyze the intratumoral glucose decomposition to trigger tumor starvation and yet provide abundant hydrogen peroxide as the substrate for Fenton-like reaction catalyzed by Fe-MOF to produce sufficient highly toxic hydroxyl radicals for enhanced chemodynamic therapy and instantly attacked tumor vascular endothelial cells to destroy the existing vasculature, while the anti-VEGFR2 antibody guided the nanohybrids to target blood vessels and block the VEGF-VEGFR2 connection to prevent angiogenesis. Both in vitro and in vivo results demonstrated the smart nanohybrids could cause the tumor cell apoptosis and vasculature disruption, and exhibited enhanced tumor regression in A549 xenograft tumor-bearing mice model. This study suggested that synergistic targeting tumor growth and its vasculature network would be more promising for curing solid tumors. Statement of significanceCooperative destruction of tumor cells and tumor vasculature offers a potential avenue for cancer therapy. Under this premise, a tumor-specific catalytic nanomedicine for enhanced tumor ablation accompanied with tumor vasculature disruption and new angiogenesis inhibition was developed through a cascade reaction with glucose oxidase modified on the surface of iron-based metal organic framework coupled with VEGFR2 antibody. The resulting data demonstrated that a therapeutic regimen targeting tumor growth as well as its vasculature with both existing vasculature disruption and neovasculature inhibition would be more potential for complete eradication of tumors.

Modulated construction of Fe-based MOF via formic acid modulator for enhanced degradation of sulfamethoxazole：Design, degradation pathways, and mechanism

Metal-organic frameworks (MOFs) have attracted more attention because of their excellent environmental catalytic capabilities. Modulation approach as an advanced assistant strategy is vital essential to enhancing the performance of MOFs. In this study, the modulated method was used to successfully synthesize a group of Fe-based MOFs, with formic acid as the modulator on the synthesis mixture. The most modulated sample Fe-MOFs-2 exhibit high specific surface areas and higher catalytic activity, which could effectively degrade SMX via PS activation, with almost 95% removal efficiency within 120 min. The results revealed that the % RSE of modulated Fe-MOFs-2 increased from 2.31 to 3.27 when compared with the origin Fe-MOFs. This may be due to the addition of formic acid induces the formation of more coordinatively unsaturated metal sites in the catalyst, resulting in structural defects. In addition, the quenching experiment and EPR analysis verified SO4-·and·OH as the major active free radicals in the degradation process. Modulated Fe-MOFs-2 demonstrated good reusability and stability under fifth cycles. Finally, four possible degradation pathways and catalytic mechanism of Fe-MOFs-2 was tentatively proposed. Our work provides insights into the rational design of modulated Fe-MOFs as promising heterogeneous catalysts for advanced wastewater treatment.

Rapid oxidation of 4-cholorphenol in the iron-based Metal–Organic frameworks (MOFs)/H2O2 system: The ignored two-steps interfacial single-electron transfer

Fe-based metal–organic frameworks (MOFs) are popular in activating oxidants e.g·H2O2 and persulfate (PS) for degrading recalcitrant organic substances, generally regarded with a simple interfacial efficient iron cycle. This study has revealed that a novel two-steps single-electron transfer mechanism would occur initially to activate the rapid degradation 4-chlorophenol (4-CP) in the MIL-88B(Fe)/H2O2 system (88B/H2O2 system). The degradation of 4-CP was acidic favorable (pH0 ≤ 6.0) and could be divided into two reaction stages, i.e., initial lag phase (0–10 min) and following rapid decay phase (10–50 min). In the first stage, H2O2 was slowly activated on the surface of 88B to form superoxide radical (O2•–), which would lead to the accumulation of the key intermediate hydroquinone (HQ) through reducing 4-CP. Afterwards, HQ could reductively dissolve iron ions which would lead to the subsequent efficient homogeneous Fenton reaction for the rapid oxidation of 4-CP by hydroxyl radical (•OH) in the following rapid decay phase. It was interesting to note that specific aromatic compounds, which would form reductive benzenediols intermediates by O2•–, could be efficiently degraded in the 88B/H2O2 system. The result of this study is expected to provide a new insight for understanding the catalytic oxidation process based on MOFs, and its application if possible.

Fe-Based metal–organic frameworks as functional materials for battery applications

This review presents a comprehensive discussion on the development and application of pristine Fe-MOFs in lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, metal–air batteries and lithium–sulfur batteries.

Synthesis and Flame Inhibition Efficiency of a Novel Fe-Based Metal-Organic Framework with Phosphorus-Containing Structure

Synthesis and Flame Inhibition Efficiency of a Novel Fe-Based Metal-Organic Framework with Phosphorus-Containing Structure

A self-supported S-doped Fe-based organic framework platform enhances electrocatalysis toward highly efficient oxygen evolution in alkaline media

A novel S-doped Fe-based metal–organic framework grows on Ni foam, exhibiting a very low overpotential of 231 mV at a current density of 20 mA cm−2, as well as a small Tafel slope and long-term durability toward the OER in alkaline media.

Recent advances in Fe-based metal–organic framework derivatives for battery applications

This review summarizes the recent progress and reasonable designs of Fe-MOF derivatives as electrodes and electrocatalysts in various batteries.

Constructing Tunable Coordinatively Unsaturated Sites in Fe-Based Metal-Organic Framework for Effective Degradation of Pharmaceuticals in Water: Performance and Mechanism

Constructing Tunable Coordinatively Unsaturated Sites in Fe-Based Metal-Organic Framework for Effective Degradation of Pharmaceuticals in Water: Performance and Mechanism

Graphene Quantum Dots Supported on Fe-based Metal-Organic Frameworks for Efficient Photocatalytic CO2 Reduction※

Graphene Quantum Dots Supported on Fe-based Metal-Organic Frameworks for Efficient Photocatalytic CO₂ Reduction^※

Persulfate-Based Visible Photocatalysis with a Novel Stability Enhanced Fe-Based Metal-Organic Framework

Persulfate-Based Visible Photocatalysis with a Novel Stability Enhanced Fe-Based Metal-Organic Framework

A 2D/1D heterojunction nanocomposite built from polymeric carbon nitride and MIL-88A(Fe) derived α-Fe2O3for enhanced photocatalytic degradation of rhodamine B

2D/1D heterojunction α-Fe2O3/C3N4 photocatalysts containing α-Fe2O3 microrods and polymeric carbon nitride flakes are synthesised through the calcination of Fe-based metal-organic frameworks and boost the visible light photocatalytic degradation of rhodamine B.

Selective regulation of peroxydisulfate-to-hydroxyl radical for efficient in-situ chemical oxidation over Fe-based metal-organic frameworks under visible light

Selective regulation of peroxydisulfate (PDS) activation-to-hydroxyl radical (·OH) production (PDS-to-·OH) is important for in situ chemical oxidation. However, the regulation mechanisms still lack reasonable explorations. Herein, a novel system involving the selective regulation of PDS-to-·OH was investigated using Fe-based metal-organic frameworks (MOF; MIL-100(Fe)) under visible light irradiation. Spectroscopic characterizations and controlled experiments indicated that the PDS chemically linked between coordinatively unsaturated metal sites (CUSs) and coordinated H2O in MIL-100(Fe) plays critical role in regulating the PDS-to-·OH transformation. Consequently, the constructed PDS/MIL-100(Fe) system showed improved performance not only in the organic degradation rate but also in PDS utilization efficiency compared with that of the traditional sulfate radical (SO4·-)-mediated PDS/MIL-68(Fe) system. This work provides new insights into the regulation of PDS activation to ·OH generation over heterogeneous catalysis. Moreover, considering the diverse compositions and structures of MOFs, this work also demonstrates their feasibility as efficient light-induced materials for in situ chemical oxidation.

A heterogeneous peroxymonosulfate catalyst built by Fe-based metal-organic framework for the dye degradation

The regulatory control on dyes is an important issue, as their discharge into the environment can pose significant risks to human health. MIL-101(Fe) prepared by a solvothermal method was used as a catalyst to generate sulfate (SO4•−) and hydroxyl (HO•) radicals from peroxymonosulfate (PMS) for the treatment of orange G (OG). The structural properties of MIL-101(Fe) were assessed by a number of characterization approaches (e.g., Fourier-transform infrared spectroscopy). The factors controlling the removal of OG were explored by a response surface methodology with central composite design (RSM-CCD) plus adaptive neuro-fuzzy inference system (ANFIS). The synthetized MIL-101(Fe) had uniform octahedral nanocrystals with rough surfaces and porous structures. The maximum catalytic removal efficiency of OG with MIL-101(Fe)/PMS process was 74% (the final concentration of Fe2+ as 0.19 mg/L and reaction rate of 434.2 μmol/g/h). The catalytic removal of OG could be defined by the non-linear kinetic models based on RSM. The OG removal efficiency declined noticeably with the addition of radical scavengers such as ethanol (EtOH) and tert-butanol (TBA) along with some mineral anions. Accordingly, MIL-101(Fe)/PMS is identified as an effective remediation option for the dyes based on advanced oxidation process (AOPs) based on high treatment efficiency at low dosage of low cost catalyst.

High-efficiency sandwich-like hierarchical AgBr-Ag@MIL-68(Fe) photocatalysts: Step-scheme photocatalytic mechanism for enhanced photoactivity

• Heterojunctions formed by sandwiching Ag NPs between AgBr and MIL-68(Fe). • Novel impregnation–precipitation more effective than conventional synthesis. • Hybrid photocatalyst removed both aqueous RhB and Cr(IV) efficiently. • The reaction mechanism of bifunctional S-scheme AgBr-Ag@MFe was elucidated. Although both step-scheme (S-scheme) heterojunction and metal–organic framework (MOF) photocatalysts have been intensively studied, few efforts have been devoted to combining them to establish high-performance MOF-based S-scheme photocatalysts. In this work, binary Ag@MIL-68(Fe) (Ag@MFe) hybrids were first fabricated by decorating Ag nanoparticles (Ag NPs) onto MIL-68(Fe), an Fe-based MOF. Owing to the high specific surface area of MIL-68(Fe), the plasmonic Ag NPs were uniformly distributed on its surface. Then, AgBr particles were deposited on the Ag@MFe hybrids via precipitation to form the final ternary sandwich-like hierarchical AgBr-Ag@MFe photocatalyst. The 30 %AgBr-1.5 %Ag@MFe sample exhibited excellent photocatalytic performance for the degradation of rhodamine B under visible light irradiation ( λ ≥ 420 nm), with an effectiveness 9.2 and 2.1 times higher than those of the original MIL-68(Fe) and binary 1.5 %Ag@MFe hybrid, respectively. Furthermore, 30 %AgBr-1.5 %Ag@MFe performed as a high-efficiency bifunctional photocatalyst towards the detoxification of water contaminants (mixture of a dye and Cr(VI)). The significantly enhanced photoactivity was attributed to the effective spatial separation of photogenerated electron–hole pairs via S-scheme charge transfer. Moreover, the plasmonic Ag NPs assembled into the contact interface of AgBr and MIL-68(Fe) enhanced the vectorial interfacial electron transfer. The formation of an S-scheme heterojunction was supported by X-ray photoelectron spectroscopy and electron spin resonance studies. This novel bifunctional AgBr-Ag@MIL-68(Fe) hybrid photocatalyst system not only provides new opportunities for environmental remediation but also highlights a promising strategy to construct high-efficiency S-scheme photocatalysts.

Indirect Differential Pulse Voltammetric Determination of Fluoride Ions at Carbon Paste Electrode Modified with Porous and Electroactive Fe3+/Fe2+ Based-Metal Organic Frameworks Type MIL-101(Fe)

An innovative and reliable electrochemical sensor was proposed for simple, sensitive and selective determination of F− ions. The sensor based on the fabrication of porous and electroactive Fe-based metal organic frameworks [MIL-101(Fe)]. It was blended with graphite powder and liquid paraffin oil to from carbon paste electrode (CPE). The MIL-101(Fe)@CPE was characterized using different techniques such as scanning electron microscope, powder X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray, cyclic voltammetry, electrochemical impedance spectroscopy, differential pulse voltammetry. The MIL-101(Fe)@CPE exhibited two redox peaks (anodic and cathodic) corresponding to Fe3+ and Fe2+, respectively. The determination of F− ions based on the formation of a stable fluoroferric complex with Fe3+/ Fe2+, decreasing the currents of redox species. It was found that the anodic peak current (Ipa) is linearly proportional to the concentration of F− in the range of 0.67–130 μM with a limit of detection (S/N = 3) of 0.201 μM. The electrode exhibited good selectivity towards F- detection with no significant interferences from common anions. The as-fabricated sensor was applied for the determination of F− in environmental water samples with recoveries % and RSDs % in the range of 98.1%–102.4% and 2.4%–3.7%, respectively.