Recent Advances and Applications of Magnetic Metal-Organic Frameworks in Adsorption and Enrichment Removal of Food and Environmental Pollutants

Optimization of Cyanocobalamin (Vitamin B12) Sorption onto Mesoporous Superparamagnetic Iron Oxide Nanoparticles

The techniques used to detect and quantify cyanocobalamin (vitamin B12) vary considerably in terms of detection sensitivity, from the most sensitive, based on radioisotopes and mass spectrometry (MS) with limits of detection (LOD) in fg mL-1, to fluorescence (FL) and surface plasmon resonance (SPR) biosensors with LOD values in the range of a few µg mL-1. For accurate quantification of an analyte present at trace levels in complex biological matrices, a selective separation and enrichment step is required to overcome matrix interferences and ensure sufficient detection sensitivity. In this study, iron oxide magnetic nanoparticles (IONPs) were used for the extraction and initial preconcentration of cyanocobalamin (vitamin B12). In the dependence of the magnetization on the H-field (hysteresis loop), no coercivity and remanence values were found at 300 K, indicating the superparamagnetic properties of the tested IONPs. Perfluorinated acids were used as amphiphilic agents to allow the sorption of cyanocobalamin onto the IONPs. FT-IR/ATR spectroscopy was used to confirm the sorption of cyanocobalamin on the IONPs. The influence of the addition of a homologous series of perfluorinated acids such as trifluoroacetic acid (TFAA), heptafluorobutyric acid (HFBA), and trichloroacetic acid (TCAA) to the extraction mixture was tested considering their type, mass, and time required for effective sorption. The adsorption kinetics and isotherm, described by the Freundlich and Langmuir equations, were analyzed. The maximum adsorption capacity (qm) exceeded 6 mg g-1 and was 8.9 mg g-1 and 7.7 mg g-1 for HFBA and TCAA, respectively, as the most efficient additives. After the desorption process using aqueous KH2PO4 solution, the sample was finally analyzed spectrophotometrically and chromatographically. The IONP-based method was successfully applied for the isolation of cyanocobalamin from human urine samples. The results showed that the developed approach is simple, cheap, accurate, and efficient for the determination of traces of cyanocobalamin in biological matrices.

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.

Advanced porous organic materials for sample preparation in pharmaceutical analysis

The development of novel sample preparation media plays a crucial role in pharmaceutical analysis. To facilitate the extraction and enrichment of pharmaceutical molecules in complex samples, various functionalized materials have been developed and prepared as adsorbents. Recently, some functionalized porous organic materials have become adsorbents for pharmaceutical analysis due to their unique properties of adsorption and recognition. These advanced porous organic materials, combined with consequent analytical techniques, have been successfully used for pharmaceutical analysis in complex samples such as environmental and biological samples. This review encapsulates the progress of advanced porous materials for pharmaceutical analysis including pesticides, antibiotics, chiral drugs, and other compounds in the past decade. In addition, we also address the limitations and future trends of these porous organic materials in pharmaceutical analysis.

Research Progress of Perfluoroalkyl Substances in Edible Oil-A Review

Perfluoroalkyl substances (PFASs) have been widely used in different types of consumer and industrial applications such as surfactants, household cleaning products, textiles, carpets, cosmetics, firefighting foams, and food packaging because of their good stability and special physicochemical properties of hydrophobicity, oleophobicity, high temperature resistance, etc. Meanwhile, PFASs are considered an emerging organic pollutant due to their persistence and potential toxicity to human health. PFASs occur in edible oil, an important component of the global diet, mainly in three ways: raw material contamination, process contamination, and migration from oil contact materials. Thus, the occurrence of PFAS in edible oils has drawn more and more attention in recent years. In this work, the pertinent literature of the last two decades from the Web of Science database was researched. This review systematically addressed the potential sources, the contamination levels, and the progress of the determination of PFASs in edible oil. It aims to provide a relatively whole profile of PFASs in edible oil, render assistance to minimise human exposure to PFASs, and standardise the detection methods of perfluoroalkyl substances in edible oil.

From polyethylene waste bottles to UIO-66 (Zr) for preconcentration of steroid hormones from river water

Metal-organic framework (UiO-66 (Zr) was synthesized using polyethylene terephthalate (PET) and used as an adsorbent for extraction and preconcentration of steroid hormones in river water. Polyethylene waste bottles were used as the source of polyethylene terephthalate (PET) ligands. The UIO-66(Zr), which the PET was made from recycled waste plastics, was used for the first time for the extraction and preconcentration of four different types of steroid hormones in river water samples. Various analytical characterization techniques were employed to characterize the synthesized material. The steroid hormones were detected and quantified using high-performance liquid chromatography coupled with diode array detector (HPLC-DAD). The results were further validated using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Experimental variables, such as sample pH, the mass of adsorbent and extraction time, were optimized using Box-Behnken design (BBD). The dispersive solid phase extraction method combined with HPLC-DAD, displayed good linearity (0.004-1000 µg/L) low limits of detections (LODs, 1.1-16 ng/L for ultrapure water and 2.6-5.3 ng/L for river water) and limits of quantification (LOQs, 3.7-5.3 ng/L for ultrapure water and 8.7-11.0 ng/L for river water samples) and acceptable extraction recoveries (86-101%). The intraday (n = 10) and interday (n = 5) precisions expressed in terms of relative standard deviations (%RSD) were all less than 5%. The steroid hormones were detected in most of the river water samples (Vaal River and Rietspruit River). The DSPE/HPLC method offered a promising approach for simultaneous extraction, preconcentration and determination of steroid hormones in water.

Performance of Rod-Shaped Ce Metal-Organic Frameworks for Defluoridation

The performance of a Ce(III)-4,4',4″-((1,3,5-triazine-2,4,6-triyl) tris (azanediyl)) tribenzoic acid-organic framework (Ce-H3TATAB-MOFs) for capturing excess fluoride in aqueous solutions and its subsequent defluoridation was investigated in depth. The optimal sorption capacity was obtained with a metal/organic ligand molar ratio of 1:1. The morphological characteristics, crystalline shape, functional groups, and pore structure of the material were analyzed via SEM, XRD, FTIR, XPS, and N₂ adsorption-desorption experiments, and the thermodynamics, kinetics, and adsorption mechanism were elucidated. The influence of pH and co-existing ions for defluoridation performance were also sought. The results show that Ce-H3TATAB-MOFs is a mesoporous material with good crystallinity, and that quasi-second kinetic and Langmuir models can describe the sorption kinetics and thermodynamics well, demonstrating that the entire sorption process is a monolayer-governed chemisorption. The Langmuir maximum sorption capacity was 129.7 mg g^-1 at 318 K (pH = 4). The adsorption mechanism involves ligand exchange, electrostatic interaction, and surface complexation. The best removal effect was reached at pH 4, and a removal effectiveness of 76.57% was obtained under strongly alkaline conditions (pH 10), indicating that the adsorbent has a wide range of applications. Ionic interference experiments showed that the presence of PO₄^3- and H₂PO₄^- in water have an inhibitory effect on defluoridation, whereas SO₄^2-, Cl^-, CO₃^2-, and NO₃^- are conducive to the adsorption of fluoride due to the ionic effect.

Overview on recent advances of magnetic metal-organic framework (MMOF) composites in removal of heavy metals from aqueous system

Developing a novel, simple, and cost-effective analytical technique with high enrichment capacity and selectivity is crucial for environmental monitoring and remediation. Metal-organic frameworks (MOFs) are porous coordination polymers that are self-assembly synthesized from organic linkers and inorganic metal ions/metal clusters. Magnetic metal-organic framework (MMOF) composites are promising candidate among the new-generation sorbent materials available for magnetic solid-phase extraction (MSPE) of environmental contaminants due to their superparamagnetism properties, high crystallinity, permanent porosity, ultrahigh specific surface area, adaptable pore shape/sizes, tunable functionality, designable framework topology, rapid and ultrahigh adsorption capacity, and reusability. In this review, we focus on recent scientific progress in the removal of heavy metal ions present in contaminated aquatic system by using MMOF composites. Different types of MMOFs, their synthetic approaches, and various properties that are harnessed for removal of heavy metal ions from contaminated water are discussed briefly. Adsorption mechanisms involved, adsorption capacity, and regeneration of the MMOF sorbents as well as recovery of heavy metal ions adsorbed that are reported in the last ten years have been discussed in this review. Moreover, particular prospects, challenges, and opportunities in future development of MMOFs towards their greener synthetic approaches for their practical industrial applications have critically been considered in this review.

Ionic liquid-based magnetic nanoparticles for magnetic dispersive solid-phase extraction: A review

Due to their highly tunable nature and outstanding physicochemical properties, ionic liquids (ILs) have been widely reported for use in the synthesis of multitudinous magnetic nanoparticles (MNPs). IL-based magnetic nanoparticles (IL-MNPs) have great potential in magnetic dispersive solid-phase extraction (MDSPE). At present, IL-MNPs have been successfully applied in the pretreatment of MDSPE samples from medicines, pesticides, veterinary drugs, heavy metals, dyes, additives, and proteins in agricultural products, foods and beverages, environmental water, and biological samples. In this review, the preparation of IL-MNPs and their application in MDSPE are comprehensively summarized. The structural characteristics of the introduced ILs used to prepare the IL-MNPs and the synthetic routes employed to obtain the IL-MNPs are described, including physical coating and chemical bonding methods. The IL-MNPs are then classified and described according to different modified materials, including silica-based materials, carbon-based materials, metal-organic frameworks, molecularly imprinted polymers and other interesting large/small molecules. Finally, the research prospects and development directions of IL-MNPs in the context of MDSPE are further identified.

Solid-phase extraction techniques based on nanomaterials for mycotoxin analysis: An overview for food and agricultural products

Mycotoxin contamination is a globally concerned problem for food and agricultural products since it may directly or indirectly induce severe threats to human health. Sensitive and selective screening is an efficient strategy to prevent or reduce human and animal exposure to mycotoxins. However, enormous challenges exist in the determination of mycotoxins, arising from complex sample matrices, trace-level analytes, and the co-occurrence of diverse mycotoxins. Appropriate sample preparation is essential to isolate, purify, and enrich mycotoxins from complicated matrices, thus decreasing sample matrix effects and lowering detection limits. With the cross-disciplinary development, new solid-phase extraction strategies have been exploited and integrated with nanotechnology to meet the challenges of mycotoxin analysis. This review summarizes the advance and progress of solid-phase extraction techniques as the methodological solutions for mycotoxin analysis. Emphases are paid on nanomaterials fabricated as trapping media of SPE techniques, including carbonaceous nanoparticles, metal/metal oxide-based nanoparticles, and nanoporous materials. Advantages and limitations are discussed, along with the potential prospects. This article is protected by copyright. All rights reserved.

Fabrication of Magnetic Al-Based Fe3O4@MIL-53 Metal Organic Framework for Capture of Multi-Pollutants Residue in Milk Followed by HPLC-UV

The efficient capture of multi-pollutant residues in food is vital for food safety monitoring. In this study, in-situ-fabricated magnetic MIL-53(Al) metal organic frameworks (MOFs), with good magnetic responsiveness, were synthesized and applied for the magnetic solid-phase extraction (MSPE) of chloramphenicol, bisphenol A, estradiol, and diethylstilbestrol. Terephthalic acid (H₂BDC) organic ligands were pre-coupled on the surface of amino-Fe₃O₄ composites (H₂BDC@Fe₃O₄). Fe₃O₄@MIL-53(Al) MOF was fabricated by in-situ hydrothermal polymerization of H₂BDC, Al (NO₃)₃, and H₂BDC@Fe₃O₄. This approach highly increased the stability of the material. The magnetic Fe₃O₄@MIL-53(Al) MOF-based MSPE was combined with high-performance liquid chromatography-photo diode array detection, to establish a novel sensitive method for analyzing multi-pollutant residues in milk. This method showed good linear correlations, in the range of 0.05–5.00 μg/mL, with good reproducibility. The limit of detection was 0.004–0.108 μg/mL. The presented method was verified using a milk sample, spiked with four pollutants, which enabled high-throughput detection and the accuracies of 88.17–107.58% confirmed its applicability, in real sample analysis.

Fe 3 O 4 @PDA/MIL‐101(Cr) as magnetic solid‐phase extraction sorbent for mycotoxins in licorice prior to ultrahigh‐performance liquid chromatography‐tandem mass spectrometry analysis

Magnetic solid‐phase extraction (MSPE) strategy based on the Fe₃O₄@PDA/MIL‐101(Cr) has been proposed to separate and purify five common mycotoxins in licorice, including aflatoxin B₁, aflatoxin G₁, sterigmatocystin, zearalenone, and ochratoxin A. Integrating the MSPE and solid–liquid extraction/partitioning, a modified QuEChERS was established to adapt to the complex licorice samples. The Fe₃O₄@PDA/MIL‐101(Cr) was successfully synthesized and characterized by Fourier transform infrared spectroscopy (FT‐IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption–desorption isotherms. Sorbents with superior advantages for exclusion of matrix interference and extraction of target analytes in a short time were obtained, according to their ability of magnetic separation, high surface area (287.75 m²/g), large pore volume (0.61 cm³/g), and nanosized structure with mesopores. Prior to analysis with ultrahigh‐performance liquid chromatography‐tandem mass spectrometry (UHPLC‐MS/MS), several key parameters that would affect the sorbents’ extraction efficiency were extensively investigated. Under the optimized conditions, the practicality of the developed method for analysis of mycotoxins in licorice samples was confirmed by adequate linearity (R² ≥ 0.9967), high sensitivity (LODs and LOQs, respectively, in the ranges 0.01–0.09 and 0.02–0.30 μg/kg), acceptable recovery (78.53%–116.28%), satisfactory reusability, and good interbatch precision of the sorbents (RSDs in the ranges 6.70%–11.20% and 6.02%–10.35%, respectively). The results indicated that the established method was feasible and reliable for the environment‐friendly and rapid screening of mycotoxins in complex licorice samples.

Tailoring multifunctional magnetic cationic metal-organic framework composite for synchronous enrichment of phosphopeptides/glycopeptides

Herein, for the first time, a multifunctional magnetic cationic MOF composite (Fe3O4@ILI-01@Ti4+) was successfully prepared for the synchronous enrichment of phosphopeptides/glycopeptides. The as-prepared Fe3O4@ILI-01@Ti4+ bears attractive properties like abundant surface...

Fe3O4@PAA@UiO-66-NH2 magnetic nanocomposite for selective adsorption of Quercetin

In the present study, a magnetic core-shell metal-organic framework (Fe₃O₄@PAA@UiO-66-NH₂) nanocomposite was synthesized by a facile step-by-step self-assembly technique and used for selective adsorption of the anti-cancer Quercetin (QCT) drug. The synthesized nanocomposite was well characterized using FTIR, XRD, BET, FESEM, and TEM techniques. The adsorption kinetics and isotherms of the magnetic nanocomposites for QCT were investigated in detail at different initial concentrations and temperatures. It was found that the experimental adsorption kinetic and isotherm data were precisely explained by the pseudo-second-order kinetic and Langmuir isotherm models. Moreover, the selective adsorption ability of the synthesized nanocomposite against various drugs in the single, binary, and ternary solutions containing QCT, Curcumin (CUR), and Methotrexate (MTX) drugs was also studied. The synthesized adsorbent showed good adsorption selectivity for QCT against CUR and MTX. The adsorption mechanism of QCT on the nanocomposite might be related to the hydrogen bonding and hydrophobic-hydrophobic interactions via π-π stacking interactions between the benzene ring skeleton of QCT and the aromatic structure of the adsorbent nanoparticles. The regeneration and reusability studies demonstrated that the developed adsorbent sustained good structural stability and adequate adsorption capacity for QCT after ten consecutive adsorption-desorption cycles.

Application of novel nanomagnetic metal-organic frameworks as a catalyst for the synthesis of new pyridines and 1,4-dihydropyridines via a cooperative vinylogous anomeric based oxidation

Herein, a new magnetic metal-organic frameworks based on Fe3O4 (NMMOFs) with porous and high surface area materials were synthesized. Then, NMMOFs were characterized by FT-IR, XRD, SEM, elemental mapping, energy dispersive X-ray (EDS), TG, DTG, VSM, and N2 adsorption-desorption isotherms (BET). Fe3O4@Co(BDC)-NH2 as a magnetic porous catalyst was applied for synthesis of novel fused pyridines and 1,4-dihydropyridines with pyrazole and pyrimidine moieties as suitable drug candidates under ultrasonic irradiation. The significant advantages of the presented methodology are mild, facile workup, high yields, short reaction times, high thermal stability, and reusability of the described NMMOFs catalyst.

New frontiers and prospects of metal-organic frameworks for removal, determination, and sensing of pesticides

Pesticides have been widely used in agriculture to control, reduce, and kill insects. Humans are also being using pesticides to control insidious animals in daily life. By these practices, a huge volume of pesticides is introduced to the environment. Despite broad-spectrum applicability, pesticides also have hazardous effects on both humans and animals at high and low concentrations. Long-term exposure to pesticides can cause different diseases, like leukemia, lymphoma, and cancers of the brain, breasts, prostate, testis, and ovaries. Reproductive disorders from pesticides include birth defects, stillbirth, spontaneous abortion, sterility, and infertility. Therefore, the application of determination and treatment methods for pre-concentration and removal of these toxic materials from the environment appears a vital concern. To date, different materials and approaches have been employed for these purposes. Among these approaches, multifunctional metal-organic frameworks (MOFs)-assisted adsorption and determination processes have always been in the spotlight. These facts are due to exclusive properties of MOFs in terms of the crystallinity, large surface area, high chemical, and physical stability, and controllable structure as well as unique features of adsorption and determination process in terms of simple, easy, cheap, available method and ability to use in large and industrial scales. In the present work, we illustrate the exceptional features of MOFs as well as the possible mechanism for the adsorption of pesticides by MOFs. The use of these fantastic materials for pre-concentration and removal of pesticides are extensively explored. In addition, the performance of MOFs was compared with other adsorbents. Finally, the new frontiers and prospects of MOFs for the determination, sensing, and removal of pesticides are presented.

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.

Polydopamine-Modified Metal-Organic Frameworks, NH2-Fe-MIL-101, as pH-Sensitive Nanocarriers for Controlled Pesticide Release

Recently, metal-organic frameworks (MOFs) have become a dazzling star among porous materials used in many fields. Considering their intriguing features, MOFs have great prospects for application in the field of sustainable agriculture, especially as versatile pesticide-delivery vehicles. However, the study of MOF-based platforms for controlled pesticide release has just begun. Controlled pesticide release responsive to environmental stimuli is highly desirable for decreased agrochemical input, improved control efficacy and diminished adverse effects. In this work, simple, octahedral, iron-based MOFs (NH2-Fe-MIL-101) were synthesized through a microwave-assisted solvothermal method using Fe3+ as the node and 2-aminoterephthalic acid as the organic ligand. Diniconazole (Dini), as a model fungicide, was loaded into NH2-Fe-MIL-101 to afford Dini@NH2-Fe-MIL-101 with a satisfactory loading content of 28.1%. The subsequent polydopamine (PDA) modification could endow Dini with pH-sensitive release patterns. The release of Dini from PDA@Dini@NH2-Fe-MIL-101 was much faster in an acidic medium compared to that in neutral and basic media. Moreover, Dini@NH2-Fe-MIL-101 and PDA@Dini@NH2-Fe-MIL-101 displayed good bioactivities against the pathogenic fungus causing wheat head scab (Fusarium graminearum). This research sought to reveal the feasibility of versatile MOFs as a pesticide-delivery platform in sustainable crop protection.

Recent Applications of Magnetic Nanoparticles in Food Analysis

Nanotechnology has become a topic of interest due to the outstanding advantages that the use of nanomaterials offers in many fields. Among them, magnetic nanoparticles (m-NPs) have been one of the most widely applied in recent years. In addition to the unique features of nanomaterials in general, which exclusively appear at nanoscale, these present magnetic or paramagnetic properties that result of great interest in many applications. In particular, in the area of food analysis, the use of these nanomaterials has undergone a considerable increase since they can be easily separated from the matrix in sorbent-based extractions, providing a considerable simplification of the procedures. This allows reducing cost and giving fast responses, which is essential in the food trade to guarantee consumer safety. These materials can also be easily tunable, providing higher selectivity. Moreover, their particular electrical, thermal and optical characteristics allow enhancing sensor signals, increasing the sensitivity of the approaches based on this type of device. The aim of this review article is to summarise the most remarkable applications of m-NPs in food analysis in the last five years (2016–2020) showing a general view of the use of such materials in the field.

Role of Ionic Liquids in Composites in Analytical Sample Preparation

Ionic liquids (ILs) are a group of non-conventional salts with melting points below 100 °C. Apart from their negligible vapor pressure at room temperature, high thermal stability, and impressive solvation properties, ILs are characterized by their tunability. Given such nearly infinite combinations of cations and anions, and the easy modification of their structures, ILs with specific properties can be synthesized. These characteristics have attracted attention regarding their use as extraction phases in analytical sample preparation methods, particularly in liquid-phase extraction methods. Given the liquid nature of most common ILs, their incorporation in analytical sample preparation methods using solid sorbents requires the preparation of solid derivatives, such as polymeric ILs, or the combination of ILs with other materials to prepare solid IL-based composites. In this sense, many solid composites based on ILs have been prepared with improved features, including magnetic particles, carbonaceous materials, polymers, silica materials, and metal-organic frameworks, as additional materials forming the composites. This review aims to give an overview on the preparation and applications of IL-based composites in analytical sample preparation in the period 2017–2020, paying attention to the role of the IL material in those composites to understand the effect of the individual components in the sorbent.