Physicochemical Methods for the Structuring and Assembly of MOF Crystals

ConspectusMetal-organic frameworks (MOFs) are promising for various applications through the creation of innovative materials and assemblies. This potential stems from their modular nature, as diverse metal ions and organic linkers can be combined to produce MOFs with unique chemical properties and lattice structures. Following extensive research on the design and postsynthetic chemical modification of MOF lattices at the molecular level, increasing attention is now focused on the next hierarchical level: controlling the morphology of MOF crystals and their subsequent assembly and positioning to create functional composites.Beyond well-established methods to regulate crystal size and shape through nucleation and coordination modulation, physicochemical techniques leveraging wetting effects, interparticle interactions, and magnetic or electric fields offer attractive avenues for the hierarchical structuring and assembly of MOFs. These techniques facilitate crystal alignment and yield unique superstructures. While our research group primarily focuses on directing MOF crystal orientation and positioning using external stimuli such as magnetic and electric fields, we also explore hierarchical MOF synthesis and structuring using liquid interfaces and depletion force-assisted packing.This account highlights our journey and progress in developing methods to regulate the morphology, assembly, orientation, and positioning of MOF crystals, placed in the context of work by other groups. First, we examine commonly utilized structuring methods for MOF crystals that employ liquid-liquid and air-liquid interfaces to spatially confine reactions, allowing us to access unique morphologies such as mushroom-like crystals and Janus particles. We also discuss strategies for concentrating and packing MOF crystals into superstructures, utilizing fluid interfaces for spatial confinement of crystals, depletion forces, entropic effects, and crystal sedimentation.A particularly compelling challenge in expanding the applicability of MOF materials is how to manipulate free-standing MOF crystals. This issue is especially important because MOFs are typically produced as loose powders, and industrial material processing is generally more efficient when the material is fluidized. While extensive research has been conducted regarding MOF growth on substrates with both positional and orientational control, there is a clear need for similar precision with free-standing MOFs dispersed in a fluid matrix. Our group has thus focused on the relatively new, yet powerful approach of using electric and magnetic fields to manipulate MOF crystals, which offers unprecedented control over the orientation and positioning of dispersed MOF crystals, complementing the more well-established methods of MOF growth on substrates. In this Account, we provide foundational background and discussions on the interactions between these external fields and MOF crystals, including critical considerations for effective MOF manipulation using such techniques. We also discuss their unique advantages and applications, and briefly examine potential application areas, such as photonics, smart materials like soft robotics and absorbents, and sensing. This Account highlights the promising potential of well-organized and aligned MOF crystals over randomly oriented ones in various applications, owing to enhanced selectivity and performance. It underscores the importance of specialized assembly methods to advance materials science and engineering, encouraging the reader to explore such approaches.

Magnetic cobalt metal organic framework for photocatalytic water splitting hydrogen evolution

Using water as a renewable and safe energy source for hydrogen generation has reduced the need to use toxic fossil fuels. Photocatalytic approaches provide a worthy solution to avoid the high expenditure on complicated electrochemical pathways to promote Hydrogen Evolution Reactions. However, several types of photocatalysts including noble metal-based catalysts have already been in use for this purpose, which are generally considered high-cost as well. The present study aims to use the benefits of metal-organic frameworks (MOFs) with semiconductor-like characteristics, highly porous structures and high design flexibility. These properties of MOFs allow more efficient and effective mass transport as well as exposure to light.in this paper, using MOF technology and benefiting from the characteristics of Fe3O4 nanoparticles as catalyst support for more efficient separation of catalyst, we have synthesized a novel composite. Our proposed photocatalyst demonstrates efficient harvest of light in all wavelengths from UV to visible to generate electron/hole pairs suitable for water splitting with a turnover frequency of 0.222 h-1 at ambient conditions without requiring any additives.

Tailoring the interfacial microenvironment of magnetic metal-organic frameworks using amino-acid-based ionic liquids for lipase immobilization

Modifying the carrier interface is a promising method to improve the microenvironment of immobilized enzymes and enhance their activity and stability. In this work, using proline as amino acid, magnetic metal-organic frameworks (MOFs) were modified with an amino-acid-based ionic liquid (AAIL) with two hydroxyl groups followed by adsorption of porcine pancreatic lipase (PPL). The activity recovery of the prepared immobilized lipase (MMOF-AAIL/PPL) was up to 162 % higher than that of MMOF-PPL (70.8 %). The Michaelis constant of MMOF-AAIL/PPL was 0.0742 mM lower than that of MMOF-PPL, but the catalytic efficiency was 0.0223 min-1 which was higher than MMOF-PPL. Furthermore, MMOF-AAIL/PPL maintained 85.6 % residual activity after stored for 40 days and its residual activity was 71.9 % while that for MMOF-PPL was 58.8 % after incubated in 6 M urea for 2 h. Particularly, after ten consecutive cycles, the residual activity of MMOF-AAIL/PPL still reached 84.4 %. In addition, the magnetic properties of the support facilitate the separation process which improves the utilization efficiency of immobilized enzymes.

Nanocomposites Based on Magnetic Nanoparticles and Metal-Organic Frameworks for Therapy, Diagnosis, and Theragnostics

In the last two decades, metal-organic frameworks (MOFs) with highly tunable structure and porosity, have emerged as drug nanocarriers in the biomedical field. In particular, nanoscaled MOFs (nanoMOFs) have been widely investigated because of their potential biocompatibility, high drug loadings, and progressive release. To enhance their properties, MOFs have been combined with magnetic nanoparticles (MNPs) to form magnetic nanocomposites (MNP@MOF) with additional functionalities. Due to the magnetic properties of the MNPs, their presence in the nanosystems enables potential combinatorial magnetic targeted therapy and diagnosis. In this Review, we analyze the four main synthetic strategies currently employed for the fabrication of MNP@MOF nanocomposites, namely, mixing, in situ formation of MNPs in presynthesized MOF, in situ formation of MOFs in the presence of MNPs, and layer-by-layer methods. Additionally, we discuss the current progress in bioapplications, focusing on drug delivery systems (DDSs), magnetic resonance imaging (MRI), magnetic hyperthermia (MHT), and theragnostic systems. Overall, we provide a comprehensive overview of the recent advances in the development and bioapplications of MNP@MOF nanocomposites, highlighting their potential for future biomedical applications with a critical analysis of the challenges and limitations of these nanocomposites in terms of their synthesis, characterization, biocompatibility, and applicability.

Drug Delivery Angle for Various Atherosclerosis and Aneurysm Percentages of the Carotid Artery

Stroke is the second cause of mortality among adult males and the first cause of death in adult females all around the world. It is also recognized as one of the most important causes of morbidity and dementia in adults. Stenosis or rupture of the only channels of the blood supply from the heart to the brain (carotid arteries) is among the main causes of stroke. In this regard, treatment of the lesions of carotid arteries, including atherosclerosis and aneurysm, could be a huge step in preventing stroke and improving brain performance. Targeted drug delivery by drug-carrying nanoparticles is the latest method for optimal delivery of drug to the damaged parts of the artery. In this study, a wide range of carotid artery lesions, including different percentages of atherosclerosis and aneurysm, were considered. After analyzing the dynamics of the fluid flow in different damaged regions and selecting the magnetic framework with proper ligand (Fe3O4@MOF) as the drug carrier, the size of the particles and their number per cycle were analyzed. Based on the results, the particle size of 100 nm and the use of 300 particles per injection at each cardiac cycle can result in maximum drug delivery to the target site. Then, the effect of the hospital bed angle on drug delivery was investigated. The results showed a unique optimal drug delivery angle for each extent of atherosclerosis or aneurysm. For example, in a 50% aneurysm, drug delivery at an angle of 30° is about 387% higher than that at an angle of 15°. Finally, simulation of real geometry indicated the effectiveness of simple geometry instead of real geometry for the simulation of carotid arteries, which can remarkably decrease the computational time and costs.

Metal-Organic Framework as a New Type of Magnetothermally-Triggered On-Demand Release Carrier

The development of external stimuli-controlled payload systems has been sought after with increasing interest toward magnetothermally-triggered drug release (MTDR) carriers due to their non-invasive features. However, current MTDR carriers present several limitations, such as poor heating efficiency caused by the aggregation of iron oxide nanoparticles (IONPs) or the presence of antiferromagnetic phases which affect their efficiency. Herein, a novel MTDR carrier is developed using a controlled encapsulation method that fully fixes and confines IONPs of various sizes within the metal-organic frameworks (MOFs). This novel carrier preserves the MOF's morphology, porosity, and IONP segregation, while enhances heating efficiency through the oxidation of antiferromagnetic phases in IONPs during encapsulation. It also features a magnetothermally-responsive nanobrush that is stimulated by an alternating magnetic field to enable on-demand drug release. The novel carrier shows improved heating, which has potential applications as contrast agents and for combined chemo and magnetic hyperthermia therapy. It holds a great promise for magneto-thermally modulated drug dosing at tumor sites, making it an exciting avenue for cancer treatment.

Magnetic Hydroxyapatite Nanoparticles in Regenerative Medicine and Nanomedicine

This review focuses on the latest advancements in magnetic hydroxyapatite (mHA) nanoparticles and their potential applications in nanomedicine and regenerative medicine. mHA nanoparticles have gained significant interest over the last few years for their great potential, offering advanced multi-therapeutic strategies because of their biocompatibility, bioactivity, and unique physicochemical features, enabling on-demand activation and control. The most relevant synthetic methods to obtain magnetic apatite-based materials, either in the form of iron-doped HA nanoparticles showing intrinsic magnetic properties or composite/hybrid compounds between HA and superparamagnetic metal oxide nanoparticles, are described as highlighting structure-property correlations. Following this, this review discusses the application of various magnetic hydroxyapatite nanomaterials in bone regeneration and nanomedicine. Finally, novel perspectives are investigated with respect to the ability of mHA nanoparticles to improve nanocarriers with homogeneous structures to promote multifunctional biological applications, such as cell stimulation and instruction, antimicrobial activity, and drug release with on-demand triggering.

Dispersive solid phase extraction of tacrolimus from biological samples using curcumin and iron-based metal organic frameworks nanocomposite followed by LC-MS/MS determination

Tacrolimus is a potent immunosuppressive drug used in the prevention of tissue rejection. It has a narrow therapeutic index. Therefore, the determination of its concentration in biological fluids like plasma and urine is a very crucial issue. In this research, tacrolimus concentrations in plasma and urine samples were determined with a dispersive solid phase extraction procedure coupled to high-performance liquid chromatography-tandem mass spectrometry. For this purpose, a curcumin modified metal-organic framework was synthesized and used in extraction procedure. Tacrolimus was adsorbed onto the sorbent surface with aid of vortexing. Then, the adsorbed tacrolimus was eluted by a suitable solvent. Important parameters in extraction procedure were optimized by "one-variable-at-a-time" approach and reported as below: sorbent amount, 10 mg; sample solution pH, 2; agitation mode, vortexing; adsorption and desorption times, 1 min, and eluent (volume), methanol (200 µL). Under the optimized conditions and according to the International Council for Harmonization guidelines, the validation of the method was performed, and the results showed acceptable accuracy and precision (relative standard deviations ≤14 %), good linearity in a wide range (4-200 ng mL-1), and low limits of detection (1.2 ng mL-1 in plasma and 0.34 ng mL-1 in urine) and quantification (4.7 ng mL-1 in plasma and 1.12 ng mL-1 in urine). Finally, the validated method was successfully applied for the determination of tacrolimus in the plasma samples of the patients.

Synthetic of functionalized magnetic titanium-based metal-organic frameworks to efficiently remove Hg(Ⅱ) from wastewater

The rapid development of process technology has led to rapid daily industrial production, which also produced a large amount of waste liquid. At the same time, the existing treatment technology cannot keep up with the demand, resulting in the malicious destruction of the environment by wastewater, especially mercury-containing wastewater was very harmful. Effective means of removing mercury ions need to be found. With magnetic ferric oxide as the core and titanium-based metal-organic frameworks as the shell, a new type of magnetic adsorbent (BTA-MIL-125(Ti)@Fe3O4) was synthesized. Materials were tested by multiple characterization methods and multiple sets of experiments. At optimal pH 6, the removal rate in 100 ppm Hg(Ⅱ) was as high as 95.8%. The theoretical adsorption capacity was 615 mg/L. Isothermal experiments, kinetic experiments and thermodynamic experiments have respectively verified that the material was a kind of adsorption material with self-emission heat based on chemical action and synergistic adsorption with Hill model. By simulating the immunity of a variety of ions (Cu, Zn, Mg, Ni, Cd), the material itself also exhibited a very high affinity for Hg(Ⅱ). The results of five high-cycle stable adsorption proved the repeatable stability of the material itself. Various characterization methods have also shown that nitrogen and sulfur-containing groups chelated with Hg(Ⅱ). All of the above was enough to show that the BTA-MIL-125(Ti)@Fe3O4 was a magnetic adsorption material with excellent performance and great prospects.

Recent advances in metal organic frameworks-based magnetic nanomaterials for waste water treatment

Magnetic nanoparticle-incorporated metal organic frameworks (MOF) are potential composites for various applications such as catalysis, water treatment, drug delivery, gas storage, chemical sensing, and heavy metal ion removal. MOFs exhibits high porosity and flexibility enabling guest species like heavy metal ions to diffuse into bulk structure. Additionally, shape and size of the pores contribute to selectivity of the guest materials. Incorporation of magnetic materials allows easy collection of adsorbent materials from solution system making the process simple and cost-effective. In view of the above advantages in the present review article, we are discussing recent advances of different magnetic material-incorporated MOF (Mg-MOF) composite for application in photocatalytic degradation of dyes and toxic chemicals, adsorption of organic compounds, adsorption of heavy metal ions, and adsorption of dyes. The review initially discusses on properties of Mg-MOF, different synthesis techniques such as mechanochemical, sonochemical (ultrasound) synthesis, slow evaporation and diffusion methods, solvo(hydro)-thermal and iono-thermal method, microwave-assisted method, microemulsion method post-synthetic modification template strategies and followed by application in waste water treatment.

Functionalization strategies of metal-organic frameworks for biomedical applications and treatment of emerging pollutants: A review

One of the representative coordination polymers, metal-organic frameworks (MOFs) material, is of hotspot interest in the multi field thanks to their unique structural characteristics and properties. As a novel hierarchical structural class, MOFs show diverse topologies, intrinsic behaviors, flexibility, etc. However, bare MOFs have less desirable biofunction, high humid sensitivity and instability in water, restraining their efficiencies in biomedical and environmental applications. Thus, a structural modification is required to address such drawbacks. Herein, we pinpoint new strategies in the synthesis and functionalization of MOFs to meet demanding requirements in in vitro tests, i.e., antibacterial face masks against corona virus infection and in wound healing and nanocarriers for drug delivery in anticancer. Regarding the treatment of wastewater containing emerging pollutants such as POPs, PFAS, and PPCPs, functionalized MOFs showed excellent performance with high efficiency and selectivity. Challenges in toxicity, vast database of clinical trials for biomedical tests and production cost can be still presented. MOFs-based composites can be, however, a bright candidate for reasonable replacement of traditional nanomaterials in biomedical and wastewater treatment applications.

A Mesoporous Magnetic Fe3O4/BioMOF-13 with a Core/Shell Nanostructure for Targeted Delivery of Doxorubicin to Breast Cancer Cells

In the current project, magnetic Bio-MOF-13 was used as an efficient carrier for the targeted delivery and controlled release of doxorubicin (DOX) to MDA-MB-231 cells. Magnetic Bio-MOF-13 was prepared by two strategies and compared to determine the optimal state of the structure. In the first path, Bio-MOF-13 was grown in situ on the surface of Fe3O4 nanoparticles (core/shell structure), while in the second method, the two presynthesized materials were mixed together (surface composite). Core/shell structure, among prepared nanocomposites, was chosen for biological evaluation due to its favorable structural features like a high accessible surface area and pore volume. Also, it is highly advantageous for drug release due to its ability to selectively release DOX in the acidic pH of breast cancer cells, while preventing any premature release in the neutral pH of the blood. Drug release from the carrier structure is precisely controlled not only by pH but also by an external magnetic field, guaranteeing accurate drug delivery at the intended location. Confocal microscopy and flow cytometry assay clearly confirms the increase in drug concentration in the MDA-MB-231 cell line after external magnet applying. This point, along with the low toxicity of the carrier components, makes it a suitable candidate for injectable medicine. According to MTT results, the percentage of viable MDA-MB-231 cells after treatment with 10 μL of DOX@Fe3O4/Bio-MOF-13 core/shell composite in different concentrations, in the presence and absence of magnetic field is 0.87 ± 0.25 and 2.07 ± 0.15, respectively. As a result, the DOX@Fe3O4/Bio-MOF-13 core/shell composite was performed and approved for targeted drug delivery and magnetic field-assisted controlled release of DOX to the MDA-MB-231 cell line.

Cu2O/Fe3O4/UiO-66 nanocomposite as an efficient fenton-like catalyst: Performance in organic pollutant degradation and influencing factors based machinelearning

The persistent presence of organic pollutants like dyes in water environment necessitates innovative approaches for efficient degradation. In this research, we developed an advanced hybrid catalyst by combining metal oxides (Cu2O, Fe3O4) with UiO-66, serving as a heterogeneous Fenton catalyst for for efficient RB19 breakdown in water with H2O2. The control factors to the catalytic behavior were also quantified by machine learning. Experimental results show that the catalytic performance was much better than its individual components (P < 0.05 & non-zero 95% C.I). The improved catalytic efficiency was linked to the occurrence of active metal centers (Fe, Cu, and Zr), with Cu(I) from Cu2O playing a crucial role in promoting increased production of HO•. Also, UiO-66 served as a catalyst support, attracting pollutants to the reaction center, while magnetic Fe3O4 aids catalyst recovery. The optimal experimental parameters for best performance were pH at 7, catalyst loading of 1.6 g/L, H2O2 strength of 0.16 M, and reaction temperature of 25 °C. The catalyst can be magnetically separated and regenerated after five recycling times without significantly reducing catalytic activity. The reaction time and pH were ranked as the most influencing factors on catalytic efficiency via Random Forest and SHapley Additive exPlanations models. The findings show that developed catalyst is a suitable candidate to remove dyes in water by Fenton heterogeneous reaction.

Surface ligand-assisted synthesis and biomedical applications of metal-organic framework nanocomposites

Metal-organic framework (MOF) nanocomposites have recently gained intensive attention for biosensing and disease therapy applications owing to their outstanding physiochemical properties. However, the direct growth of MOF nanocomposites is usually hindered by the mismatched lattice in the interface between the MOF and other nanocomponents. Surface ligands, molecules with surfactant-like properties, are demonstrated to exhibit the robust capability to modify the interfacial properties of nanomaterials and can be utilized as a powerful strategy for the synthesis of MOF nanocomposites. Besides this, surface ligands also exhibit significant functions in the morphological control and functionalization of MOF nanocomposites, thus greatly enhancing their performance in biomedical applications. In this review, the surface ligand-assisted synthesis and biomedical applications of MOF nanocomposites are comprehensively reviewed. Firstly, the synthesis of MOF nanocomposites is discussed according to the diverse roles of surface ligands. Then, MOF nanocomposites with different properties are listed with their applications in biosensing and disease therapy. Finally, current challenges and further directions of MOF nanocomposites are presented to motivate the development of MOF nanocomposites with elaborate structures, enriched functions, and excellent application prospects.

Synthesis of strong magnetic response ZIF-67 for rapid adsorption of Cu2+

With the acceleration of industrialization and urbanization, global water resources have been polluted. Among the water pollutants, heavy metals have caused great harm to the environment and organisms. When the concentration of Cu2+ in water exceeds the standard, the intake of the human body will mainly damage the nervous system. We use MOF materials with high chemical stability, specific surface area, adsorption, and other unique properties to adsorb Cu2+. MOF-67 was prepared with various solvents, and a stronger magnetic response MOF-67 with the largest surface area and best crystal form were selected. It quickly adsorbs low-concentration Cu2+ in water to purify water quality. At the same time, it can be recovered promptly through an external magnetic field to avoid secondary pollution, which conforms to the concept of green environmental protection. When the initial concentration of Cu2+ is 50 mg/L for 30 min, the adsorption rate reaches 93.4%. The magnetic adsorbent can be reused three times.

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.

Tuning Magnetic and Photophysical Properties of Luminomagnetic Metal-Organic Framework Composites in an Inverse Core-Satellite Structure

Luminomagnetic composites have been synthesized that allow for an individual tuning of luminescence intensity, chromaticity and magnetization by combination of superparamagnetic, citrate-stabilized iron oxide nanoparticles with the luminescent MOFs ³ _∞ [Ln₂ (BDC)₃ (H₂ O)₄ ] (Ln=Eu, Tb; BDC^2- =terephthalate). The components are arranged to a concept of inverse structuring compared to previous luminomagnetic composites with MOF@magnetic particle (shell@core) composition so that the luminescent MOF now acts as core and is covered by magnetic nanoparticles forming the satellite shell. Thereby, the magnetic and photophysical properties are individually tuneable between high emission intensity (1.2 ⋅ 10⁶  cps mg^-1 ) plus low saturation magnetization (6 emu g^-1 ) and the direct opposite (0.09 ⋅ 10⁶  cps mg^-1 ; 42 emu g^-1 ) by adjusting the particle coverage of the MOF. This is not achievable with a core-shell structure having a magnetic core and a dense MOF shell. The composition of the composites and the influence of different synthesis conditions on their properties were investigated by SEM/EDX, PXRD, magnetization measurements and photoluminescence spectroscopy.

Surface Modification of Magnetic ZIF-90 Nanoparticles Improves the Microenvironment of Immobilized Lipase and Its Application in Esterification

Interactions of enzymes with supports significantly affect the activity and stability of immobilized enzymes. Herein, amino-functionalized ionic liquid (IL)-grafted magnetic zeolitic imidazolate framework-90 (MZIF-90) was prepared and used to immobilize porcine pancreatic lipase (PPL). The nanocomposites were fully characterized; meanwhile, the interactions between ILs and ZIF-90 were calculated based on density functional theory. The prepared biocatalyst (PPL-ILs/MZIF-90) had a lipase loading of 178.3 mg/g and hydrolysis activity up to 287.5 U/g. When the biocatalyst was used to synthesize isoamyl acetate, the reaction media, molar ratio of alcohol/acid, temperature, and reaction time were optimized. Under the optimized reaction conditions (in hexane, alcohol/acid = 3:1, under 45 °C, reacted for 9 h), the ester yield reached 85.5%. The results of the stability test showed that PPL-ILs/MZIF-90 retained 88.7% of the initial activity after storing for 35 days and 92.5% of the initial activity after reusing for seven cycles for synthesizing isoamyl acetate. Moreover, the secondary structure analysis showed that the synthesized supports protected the active conformation of immobilized lipase, which lead to the enhanced catalytic performance. Additionally, the biocatalyst can be easily separated with a magnet, which facilitated the reusability. This study provides insights regarding the application of metal organic framework composites in the field of enzyme catalysis.

Recent Advances in Metal-Organic Frameworks for Applications in Magnetic Resonance Imaging

Diagnostics is an important part of medical practice. The information required for diagnosis is typically collected by performing diagnostic tests, some of which include imaging. Magnetic resonance imaging (MRI) is one of the most widely used and effective imaging techniques. To improve the sensitivity and specificity of MRI, contrast agents are used. In this review, the usage of metal-organic frameworks (MOFs) and composite materials based on them as contrast agents for MRI is discussed. MOFs are crystalline porous coordination polymers. Due to their huge design variety and high density of metal ions, they have been studied as a highly promising class of materials for developing MRI contrast agents. This review highlights the most important studies and focuses on the progress of the field over the last five years. The materials are classified based on their design and structural properties into three groups: MRI-active MOFs, composite materials based on MOFs, and MRI-active compounds loaded in MOFs. Moreover, an overview of MOF-based materials for heteronuclear MRI including 129Xe and 19F MRI is given.

MOFs and MOF-Derived Materials for Antibacterial Application

Bacterial infections pose a serious threat to people's health. Efforts are being made to develop antibacterial agents that can inhibit bacterial growth, prevent biofilm formation, and kill bacteria. In recent years, materials based on metal organic frameworks (MOFs) have attracted significant attention for various antibacterial applications due to their high specific surface area, high enzyme-like activity, and continuous release of metal ions. This paper reviews the recent progress of MOFs as antibacterial agents, focusing on preparation methods, fundamental antibacterial mechanisms, and strategies to enhance their antibacterial effects. Finally, several prospects related to MOFs for antibacterial application are proposed, aiming to provide possible research directions in this field.

Multimode Electron Tomography Sheds Light on Synthesis, Structure, and Properties of Complex Metal-Based Nanoparticles

Electron tomography has become a cornerstone technique for the visualization of nanoparticle morphology in three dimensions. However, to obtain in-depth information about a nanoparticle beyond surface faceting and morphology, different electron microscopy signals must be combined. The most notable examples of these combined signals include annular dark-field scanning transmission electron microscopy (ADF-STEM) with different collection angles and the combination of ADF-STEM with energy-dispersive X-ray or electron energy loss spectroscopies. Here, the experimental and computational development of various multimode tomography techniques in connection to the fundamental materials science challenges that multimode tomography has been instrumental to overcoming are summarized. Although the techniques can be applied to a wide variety of compositions, the study is restricted to metal and metal oxide nanoparticles for the sake of simplicity. Current challenges and future directions of multimode tomography are additionally discussed.

Simple preparation of a CuO@γ-Al2O3 Fenton-like catalyst and its photocatalytic degradation function

We designed a photocatalyst and developed sustainable wastewater purification technology, which have significant advantages in effectively solving the global problem of drinking water shortage. In this study, a new nanocomposite was reported and shown to be a catalyst with excellent performance; CuO was coated successively onto functionalized nano γ-Al₂O₃, and this novel structure could provide abundant active sites. We evaluated the performance of the CuO@γ-Al₂O₃ nanocomposite catalyst for polyvinyl alcohol (PVA) degradation under visible light irradiation. Under optimized conditions (calcination temperature, 450 °C; mass ratio of γ-Al₂O₃:Cu(NO₃)₂·3H₂O, 1:15; pH value, 7; catalyst dosage, 2.6 g/L; reaction temperature, 20 °C; and H₂O₂ dosage, 0.2 g/mL), the CuO@γ-Al₂O₃ nanocomposite catalyst presented an excellent PVA removal rate of 99.21%. After ten consecutive degradation experiments, the catalyst could still maintain a PVA removal rate of 97.58%, thus demonstrating excellent reusability. This study provides an efficient and easy-to-prepare photocatalyst and proposes a mechanism for the synergistic effect of the photocatalytic reaction and the Fenton-like reaction.

Magnetic relaxation switching assay based on three-dimensional assembly of Fe3O4@ZIF-8 for detection of cadmium ions

The design and construction of a novel magnetic resonance switch (MRS) sensor for cadmium ion (Cd2+) detection is described. Fe3O4@ZIF-8 was synthesized through seed-mediated growth of dimercaptosuccinic acid-coated Fe3O4. Fe3O4@ZIF-8 with high relaxation value (163.086 mM-1 s-1) and large negative zeta potential (-20.69 mV) exhibited good magnetic relaxation performance and water solubility. The successfully synthesized Fe3O4@ZIF-8 was used to develop an immune recognition-based MOFs-MRS sensor for highly sensitive detection of Cd2+. The proposed MRS detected a wide linear range of Cd2+ concentration from 2 to 200 ng mL-1 with a low limit of detection of 0.65 ng mL-1 (S/N = 3), and displayed high selectivity towards matrix interference. The robust sensing system was effective even in a complex sample matrix, enabling the quantitative analysis of Cd2+ content in rice samples and drinking water samples with good reliability. Recoveries of Cd2+ ranged from 91.50 to 112.05% for spiked drinking water and from 95.86 to 110.45% for spiked rice samples. The versatility of Fe3O4@ZIF-8 with customized relaxation responses could allow the adaptation of magnetic resonance platforms for food safety purposes.

Preparation of Magnetic MIL-68(Ga) Metal-Organic Framework and Heavy Metal Ion Removal Application

A magnetic metal-organic framework nanocomposite (magnetic MIL-68(Ga)) was synthesized through a "one pot" reaction and used for heavy metal ion removal. The morphology and elemental properties of the nanocomposite were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), as well as zeta potential. Moreover, the factors affecting the adsorption capacity of the nanocomposite, including time, pH, metal ion type and concentration, were studied. It was found that the adsorption capacity of magnetic MIL-68(Ga) for Pb²⁺ and Cu²⁺ was 220 and 130 mg/g, respectively. Notably, the magnetic adsorbents could be separated easily using an external magnetic field, regenerated by ethylenediaminetetraacetic acid disodium salt (EDTA-Na₂) and reused three times, in favor of practical application. This study provides a reference for the rapid separation and purification of heavy metal ions from wastewater.

Sustainable adsorptive removal of antibiotics from aqueous streams using Fe3O4-functionalized MIL101(Fe) chitosan composite beads

In this study, we synthesized recyclable Fe₃O₄-functionalized MIL101(Fe) chitosan composite beads for the removal of tetracycline (TC), doxycycline (DC) and ciprofloxacin (CFX) antibiotics from aqueous streams. More than 99% removal efficiency for each antibiotic was achieved at optimum pH, dosage, concentration and contact time. Langmuir adsorption isotherms and pseudo-second-ord er kinetic model were suitable with correlation coefficient values close to 1 for all the antibiotics. Adsorption capacities of 45.33, 33.20 and 31.30 mg g^-1 for TC, DC and CFX, respectively, were reported by the synthesized Fe₃O₄-functionalized MIL101(Fe) chitosan composite beads. The Fe₃O₄-functionalized MIL101(Fe) chitosan composite beads were also tested for their regeneration ability, and a remarkable regeneration ability over up to 5 cycles was observed. The adsorption of TC, DC and CFX on the surface of Fe₃O₄-functionalized MIL101(Fe) chitosan composite beads was governed by the π-π interaction, H-bonding and electrostatic interaction between the antibiotics and adsorbent due to protonation, deprotonation and cation exchange in the aqueous solution. These results showed a good prospect for applying the reported beads towards removing antibiotics from pharmaceutical industry wastewater.

State of the art on the ultrasonic-assisted removal of environmental pollutants using metal-organic frameworks

The environmental and health issues of drinking water and effluents released into nature are among the major area of contention in the past few decades. With the growth of ultrasound-based approaches in water and wastewater treatment, promising materials have also been considered to employ their advantages. Metal-organic frameworks (MOFs) are among the porous materials that have received great attention from researchers in recent years. Features such as high porosity, large specific surface area, electronic properties like semi-conductivity, and the capacity to coordinate with the organic matter have resulted in a substantial increase in scientific researches. This work deals with a comprehensive review of the application of MOFs for ultrasonic-assisted pollutant removal from wastewater. In this regard, after considering features and synthesis methods of MOFs, the mechanisms of several ultrasound-based approaches including sonocatalysis, sonophotocatalysis, and sono-adsorption are well assessed for removal of different organic compounds by MOFs. These methods are compared with some other water treatment processes with the application of MOFs in the absence of ultrasound. Also, the main concern about MOFs including environmental hazards and water stability is fully discussed and some techniques are proposed to reduce hazardous effects of MOFs and improve stability in humid/aqueous environments. Economic aspects for the preparation of MOFs are evaluated and cost estimates for ultrasonic-assisted AOP approaches were provided. Finally, the future outlooks and the new frontiers of ultrasonic-assisted methods with the help of MOFs in global environmental pollutant removal are presented.

Recent development of metal-organic framework nanocomposites for biomedical applications

Albeit metal-organic framework (MOF) composites have been extensively explored, reducing the size and dimensions of various contents within the composition, to the nanoscale regime, has recently presented unique opportunities for enhanced properties with the formation of MOF-based nanocomposites. Many distinctive strategies have been used to fabricate these nanocomposites such as through the introduction of nanoparticles (NPs) into a MOF precursor solution or vice versa to achieve a core-shell or heterostructure configuration. As such, MOF-based nanocomposites offer seemingly limitless possibilities and promising solutions for the vast range of applications across biomedical disciplines especially for improving in vivo implementation. In this review, we focus on the recent development of MOF-based nanocomposites, outline their classification according to the type of integrations (NPs, coating materials, and different MOF-derived nanocomposites), and direct special attention towards the various approaches and strategies employed to construct these nanocomposites for their prospective utilization in biomedical applications including biomimetic enzymes and photo, chemo, sonodynamic, starvation and hyperthermia therapies. Lastly, our work aims to highlight the exciting potential as well as the challenges of MOF-based nanocomposites to help guide future research as well as to contribute to the progress of MOF-based nanotechnology in biomedicine.

Functional Hybrid Micro/Nanoentities Promote Agro-Food Safety Inspection

The rapid development of nanomaterials has provided a good theoretical basis and technical support to solve the problems of food safety inspection. The combination of functionalized composite nanomaterials and well-known detection methods is gradually applied to detect hazardous substances, such as chemical residues and toxins, in agricultural food products. This review concentrates on the latest agro-food safety inspection techniques and methodologies constructed with the assistance of new hybrid micro/nanoentities, such as molecular imprinting polymers integrated with quantum dots (MIPs@QDs), molecular imprinting polymers integrated with upconversion luminescent nanoparticles (MIPs@UCNPs), upconversion luminescent nanoparticles combined with metal-organic frameworks (UCNPs@MOFs), magnetic metal-organic frameworks (MOFs@Fe₃O₄), magnetic covalent-organic frameworks (Fe₃O₄@COFs), covalent-organic frameworks doped with quantum dots (COFs@QDs), nanobody-involved immunoassay for fast inspection, etc. The presented summary and discussion favor a relevant outlook for further integrating various disciplines, like material science, nanotechnology, and analytical methodology, for addressing new challenges that emerge in agro-food research fields.

Greenness of magnetic nanomaterials in miniaturized extraction techniques: A review

Green analytical chemistry principles should be followed, as much as possible, and particularly during the development of analytical sample preparation methods. In the past few years, outstanding materials such as ionic liquids, metal-organic frameworks, carbonaceous materials, molecularly imprinted materials, and many others, have been introduced in a wide variety of miniaturized techniques in order to reduce the amount of solvents and sorbents required during the analytical sample preparation step while pursuing more efficient extraction methods. Among them, magnetic nanomaterials (MNMs) have gained special attention due to their versatile properties. Mainly, their ability to be separated from the sample matrix using an external magnetic field (thus enormously simplifying the entire process) and their easy combination with other materials, which implies the inclusion of a countless number of different functionalities, highly specific in some cases. Therefore, MNMs can be used as sorbents or as magnetic support for other materials which do not have magnetic properties, the latter permiting their combination with novel materials. The greenness of these magnetic sorbents in miniaturized extractions techniques is generally demonstrated in terms of their ease of separation and amount of sorbent required, while the nature of the material itself is left unnoticed. However, the synthesis of MNMs is not always as green as their applications, and the resulting MNMs are not always as safe as desired. Is the analytical sample preparation field ready for using green magnetic nanomaterials? This review offers an overview, from a green analytical chemistry perspective, of the current state of the use of MNMs as sorbents in microextraction strategies, their preparation, and the analytical performance offered, together with a critical discussion on where efforts should go.

Synthesis of Magnetic Metal-Organic Frame Material and Its Application in Food Sample Preparation

A variety of contaminants in food is an important aspect affecting food safety. Due to the presence of its trace amounts and the complexity of food matrix, it is very difficult to effectively separate and accurately detect them. The magnetic metal-organic framework (MMOF) composites with different structures and functions provide a new choice for the purification of food matrix and enrichment of trace targets, thus providing a new direction for the development of new technologies in food safety detection with high sensitivity and efficiency. The MOF materials composed of inorganic subunits and organic ligands have the advantages of regular pore structure, large specific surface area and good stability, which have been thoroughly studied in the pretreatment of complex food samples. MMOF materials combined different MOF materials with various magnetic nanoparticles, adding magnetic characteristics to the advantages of MOF materials, which are in terms of material selectivity, biocompatibility, easy operation and repeatability. Combined with solid phase extraction (SPE) technique, MMOF materials have been widely used in the food pretreatment. This article introduced the new preparation strategies of different MMOF materials, systematically summarizes their applications as SPE adsorbents in the pretreatment of food contaminants and analyzes and prospects their future application prospects and development directions.