Magnetic Magnetic Metal-organic Framework Research Articles

Magnetic Fe3O4@MOF@aptamer-mediated entropy-driven fluorescence biosensor for multiplexed and DNA extraction- and amplification-free detection of pathogenic bacteria

Rapid and early identification of pathogenic bacteria in food and clinical samples is critical for infectious disease control and precision medicine. In this study, we present a novel Magnetic metal–organic framework (MOF)@Aptamer-based Entropy-driven fluorescence biosensor combined with mesophilic Clostridium butyricumArgonaute (CbAgo) for multiplexed and DNA extraction- and amplification-free detection of pathogenic bacteria, termed the MAEA biosensor. In this study, magnetic zirconium-based MOF nanoparticles were modified with a phosphorylated aptamer as an efficient signal converter, which recognized the pathogens and released the complementary DNA to activate the entropy-driven circuit reaction. The highly efficient catalytic DNA circuit and isothermal enzyme-free format produce large amounts of guide DNA. CbAgo exerts precise and highly efficient endonuclease activity under the guidance of guide DNA, which makes the MAEA biosensor useful for multiplexed and DNA extraction- and amplification-free detection of pathogenic bacteria with high sensitivity (<102 CFU/mL). This study demonstrates a highly selective and reliable magnetic Fe3O4@MOF-@aptamer-based biosensor using CbAgo for simultaneously detecting multiple pathogenic bacteria, providing a potential tool for other infectious disease pathogens with convenient operation and high sensitivity.

Enhancing trimethoprim pollutant removal from wastewater using magnetic metal-organic framework encapsulated with poly (itaconic acid)-grafted crosslinked chitosan composite sponge: Optimization through Box-Behnken design and thermodynamics of adsorption parameters

Trimethoprim (TMP), an antibiotic contaminant, can be effectively removed from water by using the innovative magnetic metal-organic framework (MOF) composite sponge Fe3O4@Rh-MOF@PIC, which is shown in this study. The composite is made up of magnetite (Fe3O4) nanoparticles and a rhodium MOF embedded in a poly(itaconic acid) grafted chitosan matrix. The structure and characteristics of the synthesized material were confirmed by thorough characterization employing SEM, FTIR, XPS, XRD, and BET techniques. Notably, the composite shows a high magnetic saturation of 64emug-1, which makes magnetic separation easier, according to vibrating sample magnetometry. Moreover, BET analysis revealed that the Fe3O4@Rh-MOF@PIC sponge had an incredibly high surface area of 1236.48m2/g. Its outstanding efficacy was confirmed by batch adsorption tests, which produced a maximum adsorption capacity of 391.9mg/g for the elimination of TMP. Due to its high porosity, magnetic characteristics, and superior trimethoprim uptake, this magnetic MOF composite sponge is a promising adsorbent for effective removal of antibiotics from contaminated water sources. An adsorption energy of 24.5kJ/mol was found by batch investigations on the Fe3O4@Rh-MOF@PIC composite sponge for trimethoprim (TMP) adsorption. The fact that this value was up 8kJ/mol suggests that the main mechanism controlling TMP absorption onto the sponge adsorbent is chemisorption. Chemisorption requires creating strong chemical interactions between adsorbate and adsorbent surface groups, unlike weaker physisorption. The magnetic composite sponge exhibited strong removal capabilities and high adsorption capacities for the antibiotic pollutant. The Fe3O4@Rh-MOF@PIC composite sponge also showed magnetism, which allowed for easy magnetic separation after adsorption. Over the course of 6cycles, it showed outstanding reusability, and XRD confirmed that its composition was stable. The high surface area MOF's pore filling, hydrogen bonding, π-π stacking, and electrostatic interactions were the main trimethoprim adsorption mechanisms. This magnetic composite is feasible and effective for removing antibiotics from water because of its separability, reusability, and synergistic adsorption mechanisms via electrostatics, H-bonding, and π-interactions. The adsorption results were optimized using Box Behnken-design (BBD).

Preconcentration of Pb(II) by Magnetic Metal-Organic Frameworks and Analysis Using Graphite Furnace Atomic Absorption Spectroscopy.

In this study, a magnetic metal-organic framework (MOF) was synthesized based on magnetic Fe3O4, Cu(II), and benzene-1,3,5-tricarboxylic acid (Cu-BTC) as a sorbent for solid phase extraction (SPE) of trace amounts of Pb(II) in water and lettuce samples. Pb(II) ion was adsorbed on the magnetic MOF and easily separated by a magnet; therefore, no filtration or centrifugation was necessary. The analyte ions were eluted by HCl 0.5 mol·L-1 and analyzed via graphite furnace atomic absorption spectroscopy. The prepared sorbent was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and Fourier transform-infrared (FT-IR) spectroscopy. Under optimal experimental conditions, the method had a linear range of 0.1-50 μg·L-1. The limits of detection and quantitation for lead were found to be 0.026 and 0.08 μg·L-1, respectively. The results showed that the prepared sorbent has high selectivity for Pb2+ even in the presence of other interfering metal ions.

Magnetic Microrobots with Folate Targeting for Drug Delivery.

Untethered microrobots can be used for cargo delivery (e.g., drug molecules, stem cells, and genes) targeting designated areas. However, it is not enough to just reach the lesion site, as some drugs can only play the best therapeutic effect within the cells. To this end, folic acid (FA) was introduced into microrobots in this work as a key to mediate endocytosis of drugs into cells. The microrobots here were fabricated with biodegradable gelatin methacryloyl (GelMA) and modified with magnetic metal-organic framework (MOF). The porous structure of MOF and the hydrogel network of polymerized GelMA were used for the loading of enough FA and anticancer drug doxorubicin (DOX) respectively. Utilizing the magnetic property of magnetic MOF, these microrobots can gather around the lesion site with the navigation of magnetic fields. The combination effects of FA targeting and magnetic navigation substantially improve the anticancer efficiency of these microrobots. The result shows that the cancer cells inhibition rate of microrobots with FA can be up to 93%, while that of the ones without FA was only 78%. The introduction of FA is a useful method to improve the drug transportation ability of microrobots, providing a meaningful reference for further research.

A novel polymer coated magnetic porous carbon nanocomposite derived from a metal-organic framework for multi-target environmental pollutants preconcentration

This study describes the synthesis of a novel polymer (polypyrrole-polythiophene) coated magnetic porous carbon (MPC) composite derived from magnetic metal-organic framework (MOF) and its utilization in multi-target environmental pollutants preconcentration. In this regards, Fe3O4 nanoparticles (NPs) was used as magnetic core and Co-MOF-71 was coated on the surface of the NPs. Afterwards, magnetic MOF (MMOF) was carbonized under nitrogen atmosphere and finally MNC was coated with a polymer layer of the type polypyrrole-polythiophene to obtain the nanocomposite (MPC@PPy-PTh). Magnetic property, structure and morphology of MPC@PPy-PTh were explored via various characterization techniques. Applicability of MPC@PPy-PTh nanoadsorbent was investigated in multi-target environmental pollutants preconcentration using 4-chlorophenol 2-naphtol, 1-amino-2-naphthol, 2,4-dichloroaniline, 3,4-dichloroaniline, benzothiophene and naphthalene as the model analytes. Effect of experimental factors on the preconcentration of target pollutants was explored and optimized systematically. Under the optimized condition, LODs were obtained in the range of 0.06-0.18 µg L−1. The proposed method exhibited linearity within the range of 0.25-500 µg L−1. Repeatability of the new method based on the relative standard deviations (n = 5) was in the range of 3.4-9.0%. Finally, the analytical applicability of the optimized method was investigated in seawater and wastewater samples and satisfactory results were achieved.

NiFe2O4@SiO2@Cu3(BTC)2 nanocomposite as a magnetic metal–organic framework

A new magnetic metal–organic framework (MOF), namely, NiFe2O4@SiO2@Cu3(BTC)2, was synthesized via an in situ method using Fe(NO3)3, Ni(NO3)2, CuN2O6, TEOS, (3‐aminopropyl)triethoxysilane, and benzene‐1,3,5‐tricarboxylic acid. Three different samples were fabricated according to a formula; xNiFe2O4@(100 − x)SiO2@Cu3(BTC)2, where x = 10, 30, and 50. The integration of the intrinsic characteristic of Cu3(BTC)2 as an MOF with strong magnetic properties of NiFe2O4 could lead to an exquisite material with specific behaviors. X‐ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), and simulated thermal analyzer (STA) were utilized to characterize the mentioned samples. Results approved that the synthesized compounds were composed of SiO2 and Cu‐MOF and NiFe2O4 crystalline phases with rod‐like morphology. The similarity between the morphology of the synthesized samples and Cu‐MOF approved that an appropriate fabrication method has been selected. This fact led to observe mesoporous composites with 38–90 m2 g−1 specific surface area. PL spectroscopy confirmed the near bandgap emission, ligand‐to‐metal charge transfer, and metal‐to‐ligand charge transfer. Although all the samples had magnetic hysteresis, the highest magnetization was seen in the 50NiFe2O4@SiO2@Cu3(BTC)2 sample. This composite compound with a magnetization value of 2 emu g−1 at 8000 Oe and a specific surface area of 90 m2 g−1 could be classified as a magnetic MOF (MMOF). STA results suggested that 400°C is the highest operating temperature for this compound.

Highly efficient removal of toxic lead ions from aqueous solutions using a new magnetic metal‐organic framework nanocomposite

A magnetic metal‐organic framework (MOF) nanocomposite was successfully prepared by a new and green strategy through reasonable design. Magnetic MOF of Fe3O4‐NHSO3H@HKUST‐1 nanocomposite use for removal of lead ions as an environmental pollutant. The experimental results indicated that the nano adsorbent of Fe3O4‐NHSO3H@HKUST‐1 can removed lead ions under optimum operational conditions. The dosage of the nanocomposite, pH of the sample solution, and contact time were obtained to be 10 mg, 7.0, and 90 min, respectively, while the initial concentration of Pb(II) ions of 400 mg/L was used. A kinetic study indicated that a pseudo‐second‐order model agreed well with the experimental data. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The maximum adsorption capacity of the adsorbent for the removal of lead under the optimum operational conditions of pH 7.0 and temperature 25°C was found to be 384.6 mg/g. The thermodynamic parameters indicate that the adsorption of lead is spontaneous and endothermic. The magnetic MOF nanocomposite could be recovered easily and reused many times without significant loss of its nano‐adsorbent activity. The proposed method is simple, eco‐friendly, low cost, and efficient in the removal of lead ions from aqueous solutions.

A composite prepared from a metal-organic framework of type MIL-101(Fe) and morin-modified magnetite nanoparticles for extraction and speciation of vanadium(IV) and vanadium(V).

A novel magnetic metal-organic framework (MOF) consisting of MIL-101(Fe) and morin-modified magnetite nanoparticles was synthesized and utilized for the extractive speciation analysis of V(IV) and V(V) at trace levels. The magnetic MOF exhibits selectivity toward V(V) at pH = 5.8. The concentration of V(IV) can be determined after its oxidation to V(V) and extracting total vanadium. After sorption and elution steps, vanadium can be determined by ETAAS. Under the optimal conditions, the limit of detection, linearity and the relative standard deviation for V(V) are 3.0ngL-1, 10-750ngL-1 and 6.0%, respectively. The new method was validated by employing two certified reference materials. Finally, the method was successfully utilized for fast and selective speciation analysis of V(IV) and V(V) in water and food samples. Graphical abstract A novel functionalized magnetic metal-organic framework was synthesized and used for the speciation and preconcentration of trace amounts of vanadium.

Core-shell structured magnetic metal-organic framework composites for highly selective detection of N-glycopeptides based on boronic acid affinity chromatography

Boronic acid affinity chromatography (BAAC) is one of the most significant methods in glycoproteomics research due to its low bias towards glycopeptides and easy enrichment process. In this work, core-shell structured magnetic metal-organic framework (MOF) composites with abundant boronic acid groups were designed and synthesized for selective glycopeptide enrichment based on BAAC. The as-prepared core-shell structured magnetic MOF composites (denoted as Fe3O4@PVP/PEI@MOF (B)) inherited strong magnetic responsiveness from the Fe3O4 core as well as ultrahigh surface area and abundant boronic acid sites from the MOF shell. The affinity between boronic acid and cis-diols groups endowed the composites with improved sensitivity (0.5 fmol/μL) and selectivity (1:100) towards glycopeptides, achieving remarkable results in glycopeptides detection from standard glycoprotein digests as well as complex bio-samples. As a result, a total of 209 N-glycosylation peptides from 89 different glycoproteins were identified from human serum digests, indicating its broad prospect in glycoproteome study.

Pyrolytic in situ magnetization of metal-organic framework MIL-100 for magnetic solid-phase extraction

In this study, we report a facile, environmental friendly fabrication of a type of magnetic metal-organic framework (MOF) MIL-100 that can be used for magnetic solid-phase extraction (MSPE). The magnetic MOF composites were fabricated using in situ calcination method. The as-synthesized materials exhibited both high porosity and magnetic characteristics. They used for the MSPE of polycyclic aromatic hydrocarbons (PAHs) from water samples. Such MOF-based magnetic solid-phase extraction in combination with gas chromatography equipped with a flame ionization detector (GC-FID), exhibited wide linearity (0.02–250μgL−1), low detection limits (4.6-8.9ngL−1), and high enrichment factors (452–907) for PAHs. The relative standard deviations (RSDs) for intra- and inter-day extractions of PAHs were ranging from 1.7% to 9.8% and 3.8% to 9.2%, respectively. The recoveries for spiked PAHs (1μgL−1) in water samples were in the range of 88.5% to 106.6%. The results showed that the special anion-π orbital (electron donor-acceptor) interaction and π-π stacking between magnetic MIL-100 and PAHs play an important role in the adsorption of PAHs.

Synthesis and characterization of magnetic metal–organic framework for the adsorptive removal of Rhodamine B from aqueous solution

Adsorptive removal of Rhodamine B (RhB) on a novel kind of magnetic metal–organic framework (MOF) was studied in view of adsorption isotherm, thermodynamics and kinetics. The adsorbent was characterized by physical property measurement system, X-ray diffraction and scanning electron microscopy. The adsorption isotherm of RhB on magnetic MOF followed the Freundlich model. The resultant kinetics data was well described by the pseudo-second-order model. Most of the RhB was removed from the aqueous solution within 30min. Thermodynamic parameters including Gibbs free energy, enthalpy, and entropy of adsorption were obtained. The result confirmed that the adsorption is controlled by an entropy effect rather than an enthalpy change. The maximum removal has been achieved in the pH range of 4–8 at 150rpm. The sorbent can be used at least five times after washing with methanol including HCl (0.001molL−1). The π−π stacking interaction and electrostatic interaction may play an important role in the adsorption of RhB onto magnetic MOF. Compared with other adsorbents, this kind of magnetic material demonstrated a superior dye adsorption capability.

Synthesis of magnetic metal-organic framework (MOF) for efficient removal of organic dyes from water.

A novel, simple and efficient strategy for fabricating a magnetic metal-organic framework (MOF) as sorbent to remove organic compounds from simulated water samples is presented and tested for removal of methylene blue (MB) as an example. The novel adsorbents combine advantages of MOFs and magnetic nanoparticles and possess large capacity, low cost, rapid removal and easy separation of the solid phase, which makes it an excellent sorbent for treatment of wastewaters. The resulting magnetic MOFs composites (also known as MFCs) have large surface areas (79.52 m2 g−1), excellent magnetic response (14.89 emu g−1), and large mesopore volume (0.09 cm3 g−1), as well as good chemical inertness and mechanical stability. Adsorption was not drastically affected by pH, suggesting π–π stacking interaction and/or hydrophobic interactions between MB and MFCs. Kinetic parameters followed pseudo-second-order kinetics and adsorption was described by the Freundlich isotherm. Adsorption capacity was 84 mg MB g−1 at an initial MB concentration of 30 mg L−1, which increased to 245 mg g−1 when the initial MB concentration was 300 mg L−1. This capacity was much greater than most other adsorbents reported in the literature. In addition, MFC adsorbents possess excellent reusability, being effective after at least five consecutive cycles.

Synthesis and application of a novel magnetic metal-organic framework nanocomposite for determination of Cd, Pb, and Zn in baby food samples

This work describes the synthesis and application of a novel magnetic metal-organic framework (MOF) [(Fe3O4-2,5-dimercapto-1,3,4-thiadiazole)/Cu3(benzene-1,3,5-tricarboxylate)2] to preconcentrate trace amounts of Cd(II), Pb(II), and Zn(II) ions. A Box–Behnken design was used to find the parameters affecting the preconcentration procedure through response surface methodology. Three variables including sorption time, amount of the magnetic sorbent, and sample pH were selected as affecting factors in the sorption step, and four parameters including type, volume, concentration of the eluent, and elution time were selected in the elution step for the optimization study. These values were 33 mg, 11 min, 5.7 EDTA, 4.3 mL, 0.64 mol L–l EDTA solution, 16 min, for amount of the magnetic sorbent, sorption time, sample pH, type, volume, and concentration of the eluent, and elution time, respectively. Following the sorption and elution steps, the ions were quantified by FAAS. The limits of detection were 0.10, 0.15, and 0.75 ng mL−1 for Cd(II), Zn(II), and Pb(II) ions, respectively. The relative standard deviations (RSD) of the method were less than 8.3% for five separate batch experiments in the determination of 25 μg L−1 of Cd(II), Zn(II), and Pb(II) ions. The sorption capacity of the magnetic MOF nanocomposite was 155 mg g−1 for Cd(II), 173 mg g−1 for Pb(II), and 190 mg g−1 for Zn(II). Finally, the magnetic MOF nanocomposite was successfully applied to rapidly extract trace amounts of heavy metal ions in baby food samples.

Synthesis and Application of a Novel Functionalized Magnetic Metal–Organic Framework Sorbent for Determination of Heavy Metal Ions in Fish Samples

Abstract This work describes the synthesis and application of a novel magnetic metal–organic framework (MOF) [(Fe3O4-dipyridylamine)/MIL-101(Fe)] to preconcentrate trace amounts of Cd(II), Pb(II), Co(II), and Ni(II) ions and their determination by flame atomic absorption spectrometry. A Box–Behnken design was used to find the parameters affecting the preconcentration procedure through response surface methodology. Three factors including sorption time, amount of the magnetic sorbent, and pH of sample were selected as affecting factors in the sorption step, and four factors including type, volume and concentration of the eluent as well as the elution time were selected in the elution step for the optimization study. These values were obtained as 30 mg, 11 min, 6.5, EDTA + HNO3, 4.3 mL, 0.7 mol L−l EDTA in 0.13 mol L−l HNO3 solution, 14 min, for amount of the magnetic sorbent, sorption time, pH of sample, type, volume, and concentration of the eluent, and elution time, respectively. The limits of detection (LODs) were 0.13, 0.75, 0.3, and 0.5 ng mL−1 for Cd(II), Pb(II), Co(II), and Ni(II) ions, respectively. The relative standard deviations (RSDs) of the method were less than 9.2% for five separate batch experiments for the determination of 30 µg L−1 of Cd(II), Pb(II), Co(II), and Ni(II) ions. The sorption capacity of [(Fe3O4-dipyridylamine)/MIL-101(Fe)] was 188 mg g−1 for cadmium, 201 mg g−1 for lead, 173 mg g−1 for cobalt and 154 mg g−1 for nickel. Finally, the magnetic MOF nanocomposite was successfully applied to rapid extraction of trace amounts of heavy metal ions in fish samples.

Determination of heavy metal ions in vegetable samples using a magnetic metal–organic framework nanocomposite sorbent

This paper describes the synthesis and application of a novel magnetic metal–organic framework (MOF) [(Fe3O4-benzoyl isothiocyanate)/Cu3(benzene-1,3,5-tricarboxylate)2] to pre-concentrate trace amounts of Cd(II), Pb(II), Zn(II) and Cr(III) ions and their determination by flame atomic absorption spectrometry. A Box–Behnken design was used to find the parameters affecting the pre-concentration procedure through response surface methodology. Three factors including uptake time, amount of the magnetic sorbent and pH of the sample were selected as affecting factors in the sorption step, and four factors including type, volume and concentration of the eluent as well as the elution time were selected in the elution step for the optimisation study. The opted values were 30 mg, 10.1 min, 5.9, EDTA, 4.0 ml, 0.57 mol l–1 EDTA solution and 13.0 min for the amount of the magnetic sorbent, uptake time, pH of the sample, type, volume, concentration of the eluent, and elution time, respectively. The limits of detection (LODs) were 0.12, 0.7, 0.16, and 0.4 ng ml−1 for Cd(II), Pb(II), Zn(II) and Cr(III) ions, respectively. The relative standard deviations (RSDs) of the method were less than 7.2% for five separate batch experiments for the determination of 30 μg l−1 of Cd(II), Pb(II), Zn(II) and Cr(III) ions. The sorption capacity of the [(Fe3O4-benzoyl isothiocyanate)/MOF] was 175 mg g−1 for Cd(II), 168 mg g−1 for Pb(II), 210 mg g−1 for Zn(II) and 196 mg g−1 for Cr(III). It was found that the magnetic MOF nanocomposite demonstrated a higher capacity compared with Fe3O4-benzoyl isothiocyanate. Finally, the magnetic MOF nanocomposite was successfully applied to the rapid extraction of trace amounts of the heavy metal ions from vegetable samples.

Facile synthesis of magnetic metal organic frameworks for the enrichment of low‐abundance peptides for MALDI‐TOF MS analysis

In this work, core-shell magnetic metal organic framework (MOF) microspheres were successfully synthesized by coating magnetite particles with mercaptoacetic acid and subsequent reactions with ethanol solutions of Cu(OAc)2 and benzene-1,3,5-tricarboxylic acid (designated as H3 btc) alternately. The resulting Fe3 O4 @[Cu3 (btc)2 ] possess strong magnetic responsiveness. We applied the novel nanocomposites in the enrichment of low-concentration standard peptides, peptides in MYO and BSA tryptic digests and in human urine in combination with MALDI-TOF MS analysis for the first time. In addition, the Cu3 (btc)2 MOF shells exhibit strong affinity to peptides, thus providing a rapid and convenient approach to the concentration of low-abundance peptides. Notably, peptides at an extremely low concentration of 10 pM could be detected by MALDI-TOF MS after enrichment with the magnetic MOF composites. In brief, the facile synthesis and efficient enrichment process of the Fe3 O4 @[Cu3 (btc)2 ] microspheres make them promising candidates for the isolation of peptides in even complex biological environments.

A novel magnetic metal organic framework nanocomposite for extraction and preconcentration of heavy metal ions, and its optimization via experimental design methodology

We describe a novel magnetic metal-organic framework (MOF) prepared from dithizone-modified Fe3O4 nanoparticles and a copper-(benzene-1,3,5-tricarboxylate) MOF and its use in the preconcentration of Cd(II), Pb(II), Ni(II), and Zn(II) ions. The parameters affecting preconcentration were optimized by a Box-Behnken design through response surface methodology. Three variables (extraction time, amount of the magnetic sorbent, and pH value) were selected as the main factors affecting adsorption, while four variables (type, volume and concentration of the eluent; desorption time) were selected for desorption in the optimization study. Following preconcentration and elution, the ions were quantified by FAAS. The limits of detection are 0.12, 0.39, 0.98, and 1.2 ng mL−1 for Cd(II), Zn(II), Ni(II), and Pb(II) ions, respectively. The relative standard deviations were <4.5 % for five separate batch determinations of 50 ng mL−1 of Cd(II), Zn(II), Ni(II), and Pb(II) ions. The adsorption capacities (in mg g−1) of this new MOF are 188 for Cd(II), 104 for Pb(II), 98 Ni(II), and 206 for Zn(II). The magnetic MOF nanocomposite has a higher capacity than the Fe3O4/dithizone conjugate. This magnetic MOF nanocomposite was successfully applied to the rapid extraction of trace quantities of heavy metal ions in fish, sediment, soil, and water samples.

Solid phase extraction of Cd(II) and Pb(II) using a magnetic metal-organic framework, and their determination by FAAS

We describe a novel magnetic metal-organic framework (MOF) for the preconcentration of Cd(II) and Pb(II) ions. The MOF was prepared from the Fe3O4-pyridine conjugate and the copper(II) complex of trimesic acid. The MOF was characterized by IR spectroscopy, elemental analysis, SEM and XRD. A Box-Behnken design through response surface methodology and experimental design was used to identify the optimal parameters for preconcentration. Extraction time, amount of magnetic MOF and pH value were found to be critical factors for uptake, while type, volume, concentration of eluent, and elution time are critical in the elution step. The ions were then determined by FAAS. The limits of detection are 0.2 and 1.1 μg L−1 for Cd(II), and Pb(II) ions, respectively, relative standard deviations are <4.5% (for five replicates at 50 μg L−1 of Cd(II) and Pb(II) ions), and the enrichment capacity of the MOF is at around 190 mg g−1 for both ions which is higher than the conventional Fe3O4-pyridine material. The magnetic MOF was successfully applied to the rapid extraction of trace quantities of Cd(II) and Pb(II) ions in fish, sediment, and water samples.

Synthesis and characterization of magnetic metal-organic framework (MOF) as a novel sorbent, and its optimization by experimental design methodology for determination of palladium in environmental samples

This paper describes the synthesis and application of novel magnetic metal-organic framework (MOF) [(Fe3O4–Pyridine)/Cu3(BTC)2] for preconcentration of Pd(II) and its determination by flame atomic absorption spectrometry (FAAS). A Box–Behnken design was used to find the optimum conditions for the preconcentration procedure through response surface methodology. Three variables including amount of magnetic MOF, extraction time, and pH of extraction were selected as factors for adsorption step, and in desorption step, four parameters including type, volume, and concentration of eluent, and desorption time were selected in the optimization study. These values were 30mg, 6min, 6.9, K2SO4+NaOH, 6mL, 9.5 (w/v %)+0.01molL−1, 15.5min, for amount of MOF, extraction time, pH of extraction, type, volume, and concentration of the eluent, and desorption time, respectively. The preconcentration factor (PF), relative standard deviation (RSD), limit of detection (LOD), and adsorption capacity of the method were found to be 208, 2.1%, 0.37ngmL−1, and 105.1mgg−1, respectively. It was found that the magnetic MOF has more capacity compared to Fe3O4–Py. Finally, the magnetic MOF was successfully applied for rapid extraction of trace amounts of Pd (II) ions in fish, sediment, soil, and water samples.