Review of Synthesis and Separation Application of Metal-Organic Framework-Based Mixed-Matrix Membranes

Optimizing cancer therapy through metal organic frameworks-based nanozymes

Cancer remains a leading global health challenge, with conventional treatments facing limitations due to drug resistance and adverse effects arising from tumor heterogeneity. Nanozymes, nanomaterials mimicking natural enzymes, have emerged as promising therapeutic agents owing to their catalytic efficiency, stability, and biocompatibility. Among nanozymes, MOFs-based nanozymes are particularly attractive due to the inherent tunability of MOFs, which allows for precise control over their structure, porosity, and catalytic activity. This review comprehensively explores the recent advancements in optimizing cancer therapy through MOFs-based nanozymes. We delve into the classification of these nanozymes based on their enzyme-mimicking activities, including peroxidase, oxidase, catalase, and superoxide dismutase, and discuss their underlying catalytic mechanisms. Additionally, emerging single-atom nanozymes are discussed as a distinct category. Furthermore, we highlight the diverse therapeutic strategies employing MOFs-based nanozymes, such as starvation therapy, oxygen supply, catalytic therapy, glutathione depletion, and activation of therapeutic agents within tumor microenvironment. By exploiting the unique properties of MOFs, these nanozymes demonstrate enhanced therapeutic efficacy in various cancer treatment modalities, including chemotherapy, radiotherapy, photodynamic therapy, and sonodynamic therapy. This review underscores the significant potential of MOFs-based nanozymes as a versatile platform for developing next-generation cancer therapeutics, offering improved targeting, reduced systemic toxicity, and enhanced treatment outcomes.

Dual Ionic Pathways in Semi-Solid Electrolyte based on Binary Metal-Organic Frameworks Enable Stable Operation of Li-Metal Batteries at Extremely High Temperatures

The rapid development of the electronics market necessitates energy storage devices characterized by high energy density and capacity, alongside the ability to maintain stable and safe operation under harsh conditions, particularly elevated temperatures. In this study, a semi-solid-state electrolyte (SSSE) for Li-metal batteries (LMB) is synthesized by integrating metal-organic frameworks (MOFs) as host materials featuring a hierarchical pore structure. A trace amount of liquid electrolyte (LE) is entrapped within these pores through electrochemical activation. These findings demonstrate that this structure exhibits outstanding properties, including remarkably high thermal stability, an extended electrochemical window (5.25 V vs Li/Li+), and robust lithium-ion conductivity (2.04 × 10-4 S cm-1), owing to the synergistic effect of the hierarchical MOF pores facilitating the storage and transport of Li ions. The Li//LiFePO4 cell incorporating prepared SSSE shows excellent capacity retention, retaining 97% (162.8 mAh g-1) of their initial capacity after 100 cycles at 1 C rate at an extremely high temperature of 95 °C. It is believed that this study not only advances the understanding of ion transport in MOF-based SSSE but also significantly contributes to the development of LMB capable of stable and safe operation even under extremely high temperatures.

Preparation of Guanidine-Grafted NH2-MIL-101(Fe)/Polyvinylidene Fluoride Mixed Matrix Membranes for Adsorption of Pb2+ for Isopropanol Purification

Electronic-grade isopropyl alcohol is widely utilized in the cleaning of semiconductors and microelectronic components. Removing ions like Pb2+ is crucial since the presence of impurities may cause degradation of electronics, increased failure rates, and short circuits. Membrane materials offer a number of advantages in the field of adsorption separation; however, the lack of adsorption sites results in limited adsorption capacity. In the current work, guanidino-grafted NH2-MIL-101(Fe) was incorporated into polyvinylidene fluoride (PVDF) to prepare MOF/PVDF mixed matrix membranes (NM/PVDF) for the removal of Pb2+ from isopropanol. Benefiting from the larger specific surface area and more lone electron pairs in the guanidine group, the Pb2+ adsorption capacity of the as-prepared NM/PVDF membrane was 29.4458 mg/g, which was higher than that of the NH2-MIL-101(Fe)/PVDF membrane (20.9306 mg/g) and the pure PVDF membrane (6.7324 mg/g). The NM/PVDF membrane was able to reduce the concentration of Pb2+ from 500 to 86.73 ppb. This work highlights the potential of guanidine-grafted Fe-based MOFs/PVDF membranes as adsorbents for acquisition of electronic-grade solvents.

Two-step extraction for the evaluation of metal-organic framework impregnated materials

Metal-organic frameworks (MOFs) are widely used for gas adsorption, separation, and sensing materials. In most cases, MOFs are not used in their crystal form but as impregnated materials because the fine crystals result in high-pressure drops. One key characteristic of MOF-impregnated materials is the amount of MOF in the material. This is evaluated using the wet digestion method; however, it is limited to determining only the metal content. Moreover, some metal, denoted as free metal, will not react with ligands to form MOFs. Additionally, it is crucial to determine the ligand amount, which cannot be determined using wet digestion. In the present study, a two-step extraction method for copper (II) benzene-1,3,5-tricarboxylate (Cu-BTC MOF) impregnated materials was developed to determine the MOF formed and free metals and ligands. Various solvents were applied to evaluate the extraction efficiencies. The results led to the selection of ethanol (EtOH) for extracting free Cu2+ and BTC, while 0.3 M HNO3 was chosen to extract MOF-formed Cu2+ and BTC. The MOF-impregnated sample material was first extracted using EtOH and then 0.3 M HNO3. The Cu2+ and BTC in the obtained extract solutions, as well as EtOH and HNO3, were analyzed using flame atomic absorption spectroscopy and high-performance liquid chromatography, respectively. In standard addition tests, free and MOF-formed Cu2+ and BTC were quantitatively extracted from MOF-impregnated materials. The developed two-step analysis method was successfully applied to Cu-BTC-impregnated materials used in gas sensing.

Challenges and recent advances in MOF-based gas separation membranes

Membrane-based gas separation, characterized by a small footprint, low energy consumption and no pollution, has gained widespread attention as an environmentally friendly alternative to traditional gas separation. Metal-organic-frameworks (MOFs) are considered to be one of the most promising membrane-based gas separation materials because of their large specific surface area and high porosity. One of the hottest studies at the moment is how to utilize the characteristics of MOFs to prepare higher performance gas separation membranes. This paper provides a review of gas separation membranes used in recent years. Firstly, the synthesis methods of MOFs and MOF membranes are briefly introduced. Then, methods to improve the membrane properties of MOFs are described in detail, and include applications of lamellar MOFs, ionic liquid (IL) spin coating, functionalization of MOFs, defect engineering and mixed fillers. In addition, the challenges of MOF-based gas separation membranes are presented, including pore size, environmental disturbances, plasticization, interfacial compatibility, and so on. Finally, based on the current development status of the MOF membranes, the development prospects of MOF gas separation membranes are discussed. It is hoped to provide reliable and complete ideas for researchers to prepare high-performance gas separation membranes in the future.

Synthesis and performance of a nanosensing platform for homocysteine detection: A series of iridium(III) complexes containing aldehyde group as probe and MOF as supporting substrate

The low cost and simple detection method for Hcy (homocysteine) is highly desired in analytical and biological fields since Hcy has been regarded as a bio-marker for multiple diseases. In this work, five Ir(C^N)2(N^N)+ compounds having -CHO group in their C^N or N^N ligand were synthesized and tried for Hcy sensing. Electron-donating groups such as -NH2 and -CH3 were incorporated into the C^N or N^N ligand. Their geometric structure, electronic structure, and optical parameters (with or without Hcy) were analyzed and compared carefully to explore their Hcy sensing potential. The sensing mechanism was revealed by NMR titration and theoretical simulation as a cyclization reaction between the -CHO group and Hcy. The optimal compounds, which showed increased emission quantum yield (2.5-fold) and emission blue-shift (by ∼ 100 nm) upon Hcy, were then covalently grafted into a porous host bio-MOF-1. Linear working plots were fitted, with good selectivity, LOD of 0.15 μM, and response time of 33 s. The novelty of this work was the eye-sensitive emission color change of this nanosensing platform from red (without Hcy) to green (with Hcy).

Phosphorescent iridium (III) complex with covalent organic frameworks as scaffolds for highly selective and sensitive detection of homocysteine

Introduction: Developing a convenient and cost-effective platform for detecting homocysteine (Hcy) is of great interest as Hcy has been found to be a biomarker for Alzheimer's disease, gastric cancer, and other diseases. Methods: In this study, we synthesized five phosphorescent Ir(C∧N)2(N∧N)+ compounds (Irn, n = 1-5) with various substituents (-CHO or -CHO/-NH2), which were then doped into a covalent organic framework (COF) host via covalent bonding. Results and Discussion: The resulting optimal composites (denoted as Ir4/5@EBCOF) with -CHO/-NH2 substituents not only overcame the self-quenching issue of the bare Ir4/5 complexes but also showed rapid, highly selective, and sensitive detection of Hcy, with a limit of detection (LOD) of 0.23 μM and reaction time of 88 s. The sensing mechanism was revealed as the unique cyclization reaction between Ir(III) and Hcy that forms a six-membered ring. During the process, the color changes in the composites can be observed visually. It is expected that these phosphorescent Iridium (III) complexes with COFs will have the potential to serve as promising platforms for detecting thiols.

The Application of Metal-Organic Frameworks in Water Treatment and Their Large-Scale Preparation: A Review

Over the last few decades, there has been a growing discourse surrounding environmental and health issues stemming from drinking water and the discharge of effluents into the environment. The rapid advancement of various sewage treatment methodologies has prompted a thorough exploration of promising materials to capitalize on their benefits. Metal-organic frameworks (MOFs), as porous materials, have garnered considerable attention from researchers in recent years. These materials boast exceptional properties: unparalleled porosity, expansive specific surface areas, unique electronic characteristics including semi-conductivity, and a versatile affinity for organic molecules. These attributes have fueled a spike in research activity. This paper reviews the current MOF-based wastewater removal technologies, including separation, catalysis, and related pollutant monitoring methods, and briefly introduces the basic mechanism of some methods. The scale production problems faced by MOF in water treatment applications are evaluated, and two pioneering methods for MOF mass production are highlighted. In closing, we propose targeted recommendations and future perspectives to navigate the challenges of MOF implementation in water purification, enhancing the efficiency of material synthesis for environmental stewardship.

Glucose oxidase and metal catalysts combined tumor synergistic therapy: mechanism, advance and nanodelivery system

Cancer has always posed a significant threat to human health, prompting extensive research into new treatment strategies due to the limitations of traditional therapies. Starvation therapy (ST) has garnered considerable attention by targeting the primary energy source, glucose, utilized by cancer cells for proliferation. Glucose oxidase (GOx), a catalyst facilitating glucose consumption, has emerged as a critical therapeutic agent for ST. However, mono ST alone struggles to completely suppress tumor growth, necessitating the development of synergistic therapy approaches. Metal catalysts possess enzyme-like functions and can serve as carriers, capable of combining with GOx to achieve diverse tumor treatments. However, ensuring enzyme activity preservation in normal tissue and activation specifically within tumors presents a crucial challenge. Nanodelivery systems offer the potential to enhance therapy effectiveness by improving the stability of therapeutic agents and enabling controlled release. This review primarily focuses on recent advances in the mechanism of GOx combined with metal catalysts for synergistic tumor therapy. Furthermore, it discusses various nanoparticles (NPs) constructs designed for synergistic therapy in different carrier categories. Finally, this review provides a summary of GOx-metal catalyst-based NPs (G-M) and offers insights into the challenges associated with G-M therapy, delivery design, and oxygen (O2) supply.

Copper(II)-MOFs for bio-applications

The recent development and implementation of copper-based metal-organic frameworks in biological applications are reviewed. The advantages of the presence of copper in MOFs for relevant applications such as drug delivery, cancer treatment, sensing, and antimicrobial are highlighted. Advanced composites such as MOF-polymers are playing critical roles in developing materials for specific applications.

Holmium-Containing Metal-Organic Frameworks as Modifiers for PEBA-Based Membranes

Recently, there has been an active search for new modifiers to create hybrid polymeric materials for various applications, in particular, membrane technology. One of the topical modifiers is metal-organic frameworks (MOFs), which can significantly alter the characteristics of obtained mixed matrix membranes (MMMs). In this work, new holmium-based MOFs (Ho-MOFs) were synthesized for polyether block amide (PEBA) modification to develop novel MMMs with improved properties. The study of Ho-MOFs, polymers and membranes was carried out by methods of X-ray phase analysis, scanning electron and atomic force microscopies, Fourier transform infrared spectroscopy, low-temperature nitrogen adsorption, dynamic and kinematic viscosity, static and dynamic light scattering, gel permeation chromatography, thermogravimetric analysis and contact angle measurements. Synthesized Ho-MOFs had different X-ray structures, particle forms and sizes depending on the ligand used. To study the effect of Ho-MOF modifier on membrane transport properties, PEBA/Ho-MOFs membrane retention capacity was evaluated in vacuum fourth-stage filtration for dye removal (Congo Red, Fuchsin, Glycine thymol blue, Methylene blue, Eriochrome Black T). Modified membranes demonstrated improved flux and rejection coefficients for dyes containing amino groups: Congo Red, Fuchsin (PEBA/Ho-1,3,5-H3btc membrane possessed optimal properties: 81% and 68% rejection coefficients for Congo Red and Fuchsin filtration, respectively, and 0.7 L/(m2s) flux).