Iron-containing Metal-organic Frameworks Research Articles

Metal–Organic Framework Fe-BTC as Heterogeneous Catalyst for Electro-Fenton Treatment of Tetracycline

This study explores the use of the iron-containing metal–organic framework (MOF), Basolite®F300, as a heterogeneous catalyst for electrochemically-driven Fenton processes. Electrochemical advanced oxidation processes (EAOPs) have shown promise on the abatement of recalcitrant organic pollutants such as pharmaceuticals. Tetracyclines (TC) are a frequently used class of antibiotics that are now polluting surface water and groundwater sources worldwide. Acknowledging the fast capability of EAOPs to treat persistent pharmaceutical pollutants, we propose an electrochemical Fenton treatment process that is catalyzed by the use of a commercially available MOF material to degrade TC. The efficiency of H2O2 generation in the IrO2/carbon felt setup is highlighted. However, electrochemical oxidation with H2O2 production (ECO-H2O2) alone is not enough to achieve complete TC removal, attributed to the formation of weak oxidant species. Incorporating Basolite®F300 in the heterogeneous electro-Fenton (HEF) process results in complete TC removal within 40 min, showcasing its efficacy. Additionally, this study explores the effect of varying MOF concentrations, indicating optimal removal rates at 100 mg L−1 due to a balance of kinetics and limitation of active sites of the catalysts. Furthermore, the impact of the applied current on TC removal is investigated, revealing a proportional relationship between current and removal rates. The analysis of energy efficiency emphasizes 50 mA as the optimal current, however, balancing removal efficiency with electrical energy consumption. This work highlights the potential of Basolite®F300 as an effective catalyst in the HEF process for pollutant abatement, providing valuable insights into optimizing electrified water treatment applications with MOF nanomaterials to treat organic pollutants.

Dramatic change in the properties of magnetite-modified MOF particles depending on the synthesis approach

Iron-containing metal–organic frameworks are promising Fenton catalysts. However, the absence of additional modifiers has proven difficult due to the low reaction rates and the inability to manipulate the catalysts. We hypothesize that the production of iron oxide NPs in the presence of a metal-organic framework will increase the rate of the Fenton reaction and lead to the production of particles that can be magnetically manipulated without changing the structure of the components. A comprehensive approach lead to a metal organic framework using the example of MIL-88b (Materials of Institute Lavoisier) modified with iron oxides NPs: formulation of iron oxide in the presence of MIL-88b and vice versa. The synthesis of MIL-88b consists of preparing a complexation compound with the respective structure and addition of terephthalic acid. The synthesis of MIL-88b facilitates to control the topology of the resulting material. Both methods for composite formulation lead to the preservation of the structure of iron oxide, however, a more technologically complex approach to obtaining MIL-88b in the presence of Fe3O4 suddenly turned out to be the more efficient for the release of iron ions.

Combination of ferroptosis and pyroptosis dual induction by triptolide nano-MOFs for immunotherapy of Melanoma

Immunotherapy has good potential to eradicate tumors in the long term. However, due to the low immunogenicity of tumor cells, current cancer immunotherapies are not effective. To address this limitation, we constructed a BSA-FA functionalized iron-containing metal-organic framework (TPL@TFBF) that triggers a potent systemic anti-tumor immune response by inducing ferroptosis and pyroptosis in tumor cells and releasing large quantities of damage-associated molecular patterns (DAMPs) to induce immunogenicity, and showing excellent efficacy against melanoma lung metastases in vivo. This nanoplatform forms a metal-organic framework through the coordination between tannic acid (TA) and Fe3+ and is then loaded with triptolide (TPL), which is coated with FA-modified BSA. The nanoparticles target melanoma cells by FA modification, releasing TPL, Fe3+ and TA. Fe3+ is reduced to Fe2+ by TA, triggering the Fenton reaction and resulting in ROS production. Moreover, TPL increases the production of intracellular ROS by inhibiting the expression of nuclear factor erythroid-2 related factor (Nrf2). Such simultaneous amplification of intracellular ROS induces the cells to undergo ferroptosis and pyroptosis, releasing large amounts of DAMPs, which stimulate antigen presentation of dendritic cells (DCs) and the proliferation of cytotoxic T lymphocytes (CD4+/CD8 + T cells) to inhibit tumor and lung metastasis. In addition, combining nanoparticle treatment with immune checkpoint blockade (ICB) further inhibits melanoma growth. This work provides a new strategy for tumor immunotherapy based on various combinations of cell death mechanisms.

Functional material “Ionic liquid-supported MIL-101(Fe)” to enhance composite solid electrolyte for lithium metal batteries

Because of poor ionic conductivity, insufficient interfacial compatibility and other issues, all-solid-state lithium metal batteries (ASSLMBs) are difficult to commercialize. Here, a sort of composite solid-state polymer electrolytes (CSPEs) is prepared by compounding multifunctional fillers with polyethylene oxide (PEO), and the multifunctional filler is obtained by absorbing the ionic liquids (ILs) into the iron-containing metal-organic frameworks (MOFs). The porosity of MOFs can improve the path for Li+ transport and accelerate the Li+ transport after adsorbing ILs. This strategy endows the prepared CSPEs with high ionic conductivity of 8.46 × 10−4 S cm−1 at 60 °C and wide electrochemical window (5.2 V). In addition, the transference number of the CSPEs is increased to 0.54. After 250 cycles, the assembled LiFePO4/CSPE/Li battery has a discharge-specific capacity of 139.1 mAh g−1 and a capacity retention of 93.3% at 0.5 C under 60 °C. This work reveals a feasible strategy in constructing high-performance solid-state LMBs, as well as an important complement for material and structure development in the field of energy storage.

Autocatalytically hydroxyl-producing composite wound dressing for bacteria-infected wound healing

The creation of wound dressings with low drug resistance and broad-spectrum antibacterial capability is a key topic of scientific interest. To achieve this, a bactericidal wound dressing with the capacity to autocatalytically produce hydroxyl radicals (OH) was developed. The wound dressing was an electrospun PCL/gelatin/glucose composite fiber mesh (PGD) with functional iron-containing metal-organic framework (Fe-MOF) nanozymes. These functional nanozymes (G@Fe) were formed by coupling glucose oxidase (GOx) and Fe-MOF through amide bonds. These nanozymes enabled the conversion of glucose released from the PGD composite mesh into hydroxyl radicals via an autocatalytic cascade reaction to destroy bacteria. The antibacterial efficiency of wound dressings and their stimulation of tissue regeneration were assessed using a MRSA-infected skin wound infection model on the back of SD mice. The G@Fe/PGD wound dressing exhibited improved wound healing capacity and had comparable biosafety to commercial silver-containing dressings, suggesting a potential replacement in the future.

Impact of active sites on encapsulation of curcumin in Metal Organic Frameworks

In this study, we present the investigation of the curcumin loading and release properties of four different Metal-Organic Frameworks (MOFs) with varying metal centres and organic ligands. Through our research, we have identified HKUST-1 and MIL-100, highly porous copper and iron-containing MOFs, that exhibit specific interactions with curcumin, leading to high encapsulation efficiencies (55%–75%) even at low concentrations as 6 ppm. The binding modes of curcumin onto MOFs have been investigated using a combined experimental and computational approach. Furthermore, our drug-releasing studies have revealed slow and prolonged release for over two days, which further indicates the specific interactions of curcumin with HKUST-1 and MIL-100. To the best of our knowledge, this is the first comparative study that investigates the drug delivery properties of curcumin using Copper, Ferrous, and Zinc MOFs. Our findings pave the way for the development of stable, highly interactive MOFs as drug carriers for curcumin, which has the potential to overcome its poor aqueous solubility and rapid metabolism, and enhance its pharmacological activities in medicine.

Iron-containing metal-organic framework thin film as a drug delivery system

Selective bulk metal-organic frameworks (MOFs) have exhibited great potential in biomedical applications. However, topical treatments and drug elution coatings will require uniform films as drug delivery systems. This work studies the use of surface supportive MOF thin films for drug loading and releasing. More specifically, we focus on an iron-containing MOF, MIL-88B(Fe), on a COOH-terminated self-assembled monolayer (SAM) modified Au surface for encapsulating ibuprofen as a model drug. A combined experimental and computational approach was employed to study the fabrication of MIL-88B(Fe) film on functionalized Au surfaces. We used several surface characterization techniques, including infrared spectroscopy and scanning electron microscopy, to confirm the chemical composition and morphological changes of the surface after each modification step. The resulting MIL-88B(Fe) thin film was found capable of loading 8.7 wt% of ibuprofen using quartz crystal microbalance analysis. Moreover, we applied cluster simulations to study the binding mechanisms of MIL-88B(Fe) and its interactions with ibuprofen based on the density functional theory (DFT). The unsaturated Fe site was confirmed kinetically more favorable to bind to the COOH-end group on the SAM. Hydrogen bonding and π-CH interactions between ibuprofen and MIL-88B(Fe) promote ibuprofen being retained inside of the cages of MIL-88B(Fe).

Efficient and reductive removal of bromate using a novel and stable nanoscale zero-valent iron embedded in N-doped carbon derived from metal-organic frameworks

Nanoscale zero-valent iron (nZVI) has drawn great interest in the remediation of contaminated waters. In this study, we prepared a novel and stable nZVI embedded in N-doped carbon matrix (nZVI@MOF-CN) using a facile direct carbonization method, in which an iron-containing metal-organic framework (MOF) served as both the iron and carbon sources, and melamine as the nitrogen source. The nZVI@MOF-CN composites were used in the removal of bromate in water, which could be effectively reduced by the surface electrons transferred from nZVI to the carbon encapsulation layer due to the Schottky-Mott effect. Doped nitrogen significantly facilitated the reduction of bromate by nZVI, because it enhanced the nZVI dispersion and bromate adsorption, and modulated the carbon matrix conductivity. The bromate reduction activity of nZVI@MOF-CN was more than 50 times higher that of its un-doped counterpart and a commercial nZVI. Moreover, owing to the protection of carbon encapsulation layer, nZVI@MOF-CN exhibited good stability and reusability. The leached concentration of iron ions of nZVI@MOF-CN was less than 5% of the commercial nZVI under the same reaction conditions. Commercial nZVI almost completely lost its bromate reduction activity after use (3% reduction efficiency in the examined time frame), while nZVI@MOF-CN maintained a reduction efficiency of 61%. The nZVI@MOF-CN could be effectively regenerated by hydrogenation reduction. After five reaction-regeneration cycles, nZVI@MOF-CN still achieved a bromate reduction efficiency of approximately 80%. These results suggest that MOF-derived nZVI materials are highly reactive and stable for the reductive removal of pollutants in water.

Polymetallic phosphides evolved from MOF and LDH dual-precursors for robust oxygen evolution reaction in alkaline and seawater media

Water electrolysis is an efficient, clean and sustainable method for hydrogen production. However, high cost performance oxygen evolution reaction (OER) catalysts become the key to realize the industry-scale hydrogen production from water electrolysis. Herein, we for the first time report a polymetallic transition metal phosphide (Fe2P–NiCoP) catalyst derived from iron-containing metal-organic frameworks (MIL-88A) and NiCo-LDH as double precursors, effectively driving the OER in alkaline media. Experimental and density functional theory (DFT) calculation results verify that, the NiOOH/FeOOH, as real active site for OER generated by Fe2P–NiCoP reconstruction, reduces the adsorption energy of oxygen-containing intermediates and accelerate the reaction kinetics. As expected, only 239 and 260 mV overpotentials are required to reach current densities of 20 and 50 mA cm−2 in 1 M KOH solutions, which is far better than commercial RuO2 toward OER. Besides, Fe2P–NiCoP also achieves long-term stability up to 100 h, providing the possibility of commercial large-scale applications. Furthermore, it still obtains the outstanding activity in direct electrolysis of alkaline seawater, with only 258 and 278 mV overpotentials needed to reach current densities of 20 and 50 mA cm−2, respectively. Undoubtedly, Fe2P–NiCoP is one of the most promising non-noble metal electrocatalysts for practical hydrogen production from water splitting.

Synthesis, characterization, and CO2 adsorption properties of metal organic framework Fe-BDC.

The iron-containing Metal–Organic Frameworks (MOFs) have attracted a great deal of attention in the areas of gas separation, catalytic conversion, and drug delivery, due to their high surface area and activity, as well as the non-toxicity of iron. In this study, Fe-based MOFs using BDC ligands, MIL-101(Fe), MIL-53(Fe) and Amino-MIL-101(Fe) are synthesized by a solvothermal method and characterized by conventional methods such as BET, SEM, and TGA. Afterwards, the synthesized MOFs are investigated from the point of view of the adsorbing capability of carbon dioxide at different pressures and temperatures, and also their resistance to water and solvent. The results showed that Amino-MIL-101(Fe) achieved more CO2 adsorption than MIL-101(Fe) and MIL-53(Fe), equal to 13 mmol g−1 at 4 MP. Although MIL-53(Fe) has the best temperature resistance, around 350 °C, Amino-MIL-101(Fe) is more stable against water and ethanol and its surface area is increased from 670 to 915 m2 g−1 after washing with ethanol. The adsorption study reveals that CO2 is adsorbed not only by a physical adsorption mechanism, but also by chemisorption of acidic carbon dioxide by basic NH2 agent in the structure of Amino-MIL-101(Fe).

MOF-Derived Porous Fe2O3 Nanoparticles Coupled with CdS Quantum Dots for Degradation of Bisphenol A under Visible Light Irradiation.

In this work, CdS quantum dots (QDs) were planted on magnetically recyclable porous Fe2O3 (denoted as F450) to obtain CdS QDs/porous Fe2O3 hybrids (denoted as X–CdS/F450, in which X is the immersion times of CdS QDs). Porous Fe2O3 was first obtained by pyrolysis from an iron-containing metal–organic framework by a two-step calcination method. Next, CdS QDs (of average size 3.0 nm) were uniformly and closely attached to the porous F450 via a sequential chemical-bath deposition strategy. As expected, the X–CdS/F450 hybrids serve as high-performance photocatalysts for the degradation of bisphenol A, a typical endocrine-disrupting chemical. Almost ∼100% of the bisphenol A was degraded over 5-CdS/F450 after visible light irradiation for 30 min (λ ≥ 420 nm). In comparison, the degradation efficiency of pure F450 powder is 59.2%. The high performance of 5-CdS/F450 may be ascribable to the fast electron transport of porous F450, the intense visible-light absorption of the CdS QDs and the matched energy levels between CdS and F450. More significantly, through the photocatalytic degradation reaction, the X–CdS/F450 hybrids can easily be recovered magnetically and reused in subsequent cycles, indicating their stability and recyclability.

A Metal-Organic Framework (MOF) Fenton Nanoagent-Enabled Nanocatalytic Cancer Therapy in Synergy with Autophagy Inhibition.

Nanocatalytic medicine has been developed recently to trigger intratumoral generation of highly toxic reactive oxygen species (ROS) for cancer therapy, which, unfortunately, suffers from compromised therapeutic efficacy due to a self-protective mechanism, autophagy, of cancer cells to mitigate oxidative damage. In this work, during the efforts of ROS generation by nanocatalytic medicine, a pharmacological autophagy inhibition strategy is implemented for augmenting ROS-induced oxidative damage for synergetic cancer therapy. An iron-containing metal-organic framework [MOF(Fe)] nanocatalyst as a peroxidase mimic is used to catalyze the generation of highly oxidizing •OH radicals specifically within cancer cells, while chloroquine is applied to deacidify lysosomes and inhibit autophagy, cutting off the self-protection pathway under severe oxidative stress. Cancer cells fail to extract their components to detoxicate and strengthen themselves, finally succumbing to the ROS-induced oxidative damage during nanocatalytic therapy. Both in vitro and in vivo results demonstrate the synergy between nanocatalytic therapy and autophagy inhibition, suggesting that such a combined strategy is applicable to amplify tumor-specific oxidative damage and may be informative to future design of therapeutic regimen.

State-of-the-Art Advances and Challenges of Iron-Based Metal Organic Frameworks from Attractive Features, Synthesis to Multifunctional Applications.

Metal organic frameworks (MOFs), as an original kind of organic-inorganic porous material, are constructed with metal centers and organic linkers via a coordination complexation reaction. Among uncountable MOF materials, iron-containing metal organic frameworks (Fe-MOFs) have excellent potential in practical applications owing to their many fascinating properties, such as diverse structure types, low toxicity, preferable stability, and tailored functionality. Here, recent research progresses of Fe-MOFs in attractive features, synthesis, and multifunctional applications are described. Fe-MOFs with porosity and tailored functionality are discussed according to the design of building blocks. Four types of synthetic methods including solvothermal, hydrothermal, microwave, and dry gel conversion synthesis are illustrated. Finally, the applications of Fe-MOFs in Li-ion batteries, sensors, gas storage, separation in gas and liquid phases, and catalysis are elucidated, focusing on the mechanism. The aim is to provide prospects for extending Fe-MOFs in more practical applications.

An Iron‐Containing Metal–Organic Framework as a Highly Efficient Catalyst for Ozone Decomposition

AbstractWe present an iron‐containing metal–organic framework, MIL‐100(Fe), for ozone removal. MIL‐100(Fe) exhibits long‐lasting ozone conversion efficiency of 100 % for over 100 h under a relative humidity of 45 % and space velocity of 1.9×105 h−1 at room temperature, which is well beyond the performance of most porous or metal catalysts such as activated carbon and α‐MnO2. We also investigated the impact of humidity level and elucidated the plausible reaction mechanism, which is further confirmed by DFT calculations. Furthermore, MIL‐100(Fe) can be processed into films and used as filtration layer in a mask to protect personnel against ozone contamination. This study demonstrates the promising potential of MOFs in ozone pollution control, and also offers new insights for the design of ozone decomposition catalysts.

An Iron-Containing Metal-Organic Framework as a Highly Efficient Catalyst for Ozone Decomposition.

We present an iron-containing metal-organic framework, MIL-100(Fe), for ozone removal. MIL-100(Fe) exhibits long-lasting ozone conversion efficiency of 100 % for over 100 h under a relative humidity of 45 % and space velocity of 1.9×105 h-1 at room temperature, which is well beyond the performance of most porous or metal catalysts such as activated carbon and α-MnO2 . We also investigated the impact of humidity level and elucidated the plausible reaction mechanism, which is further confirmed by DFT calculations. Furthermore, MIL-100(Fe) can be processed into films and used as filtration layer in a mask to protect personnel against ozone contamination. This study demonstrates the promising potential of MOFs in ozone pollution control, and also offers new insights for the design of ozone decomposition catalysts.

Green synthesis and evaluation of an iron-based metal-organic framework MIL-88B for efficient decontamination of arsenate from water.

Iron-containing metal-organic frameworks (MOFs) have gradually emerged as environmentally benign alternatives for reducing the levels of environmental contamination because of their advantages, such as readily obtained raw materials with low cost, nontoxic metal source with good biocompatibility, and distinguished physicochemical features e.g., high porosity, framework flexibility, and semiconductor properties. In this study, we reported an innovative strategy for synthesizing an iron-based MOF, MIL-88B, at room temperature. The novelty of this strategy was the use of ethanol as solvent and the pretreatment of dry milling with neither the bulk use of a toxic organic solvent nor the addition of extremely dangerous hydrofluoric acid or strong alkali. The synthesized MIL-88B(Fe) was evaluated as a sorbent for removing arsenate in water and it exhibited high adsorption capacity (156.7 mg g-1) at a low dosage. The removal capacity of trace arsenate on MIL-88B(Fe) was 32.3 mg g-1 at a low equilibrium concentration (6.4 μg L-1), which satisfied the arsenic threshold for drinking water. The results of Fourier transform infrared and X-ray photoelectron spectroscopy indicated that the As(v) molecules bonded with the oxygen molecules, which were coordinated with FeO clusters in the framework. This work presented the potential use of the up-scaled MIL-88B as an excellent sorbent for purifying arsenate-contaminated water.

Pyrolysis of Metal–Organic Frameworks to Fe3O4@Fe5C2 Core–Shell Nanoparticles for Fischer–Tropsch Synthesis

We prepared highly active catalysts for Fischer–Tropsch (FT) synthesis through the pyrolysis of iron-containing metal–organic frameworks (MOFs). The Fe-time yields of the nitrogen-doped catalyst were as high as 720 μmolCO gFe–1 s–1 under the conditions of 300 °C, 2 MPa, and H2/CO = 1, which is a value that surpasses that of most FT catalysts reported in the literature. The pyrolysis of the MOFs yielded nanoparticles with a unique iron oxide@iron carbide core–shell structure dispersed on carbon supports. Such a structure is favorable for FT synthesis and has never been reported previously. Our strategy resolved the problem that the strong metal–support interactions that are usually required to stabilize dispersed particles in calcination compromise the catalytic activity, because of the difficulty of reducing metal oxides. Moreover, we found full coverage of carbonates on the particle surfaces, which likely result from decarboxylation of the MOFs and further stabilize the particles before decomposing to CO...

Multiscale Model for a Metal–Organic Framework: High-Spin Rebound Mechanism in the Reaction of the Oxoiron(IV) Species of Fe-MOF-74

We performed ONIOM QM/MM calculations to understand how ethane is hydroxylated and ethanol is converted to acetaldehyde by an oxoiron(IV) species generated within an iron-containing metal–organic framework called Fe-MOF-74. The calculations showed that the ethane hydroxylation proceeds via a high-spin rebound mechanism. The conversion of ethanol into acetaldehyde should occur more favorably via H-abstraction from the O–H bond than via C–H cleavage, although the O–H bond of ethanol is stronger than the C(1)–H bond. This trend can be rationalized by the effect of proton-coupled electron transfer, which stabilizes the transition state for O–H cleavage.

Kinetically tuned dimensional augmentation as a versatile synthetic route towards robust metal-organic frameworks.

Metal-organic frameworks with high stability have been pursued for many years due to the sustainability requirement for practical applications. However, researchers have had great difficulty synthesizing chemically ultra-stable, highly porous metal-organic frameworks in the form of crystalline solids, especially as single crystals. Here we present a kinetically tuned dimensional augmentation synthetic route for the preparation of highly crystalline and extremely robust metal-organic frameworks with a preserved metal cluster core. Through this versatile synthetic route, we obtain large single crystals of 34 different iron-containing metal-organic frameworks. Among them, PCN-250(Fe2Co) exhibits high volumetric uptake of hydrogen and methane, and is also stable in water and aqueous solutions with a wide range of pH values.

Hollow carbon nano-onions with hierarchical porosity derived from commercial metal organic framework

We report on the synthesis of new metal–organic framework derived carbons using a two-step process employing for the first time a commercially available iron-containing metal–organic framework. The resulting carbons consist mainly of highly graphitic shells due to the highly dispersed iron in the precursor structure which catalyzes the formation of graphitic carbon. In addition, a distinct onion-like morphology is observed, with high total pore volumes of up to 1cc/g and a hierarchically structured porosity in which the hollow cores of the carbon onions are accessible via smaller micro- and mesopores. As a proof of concept we furthermore demonstrate the inherent structure of this carbon being advantageous for the application in lithium–sulfur batteries as a both confining and contacting host for the active material, yielding capacities of up to 550mAh/g after 40 cycles.