Recent strategies to improve MOF performance in solid phase extraction of organic dyes

Efficient Solid-Phase Extraction of Neonicotinoid Insecticides from Environmental Water and Drink Samples Using a Postmodified Metal-Organic Framework

Neonicotinoid insecticides (NNIs) are extensively utilized globally because of their efficient and broad-spectrum properties. However, their residues are also extensively distributed in the environment. Herein, MIL-101-SO3Na with abundant -NH- and sulfonate groups was synthesized via chloromethylation and nucleophilic substitution postmodification strategies and used to extract NNIs via solid-phase extraction. MIL-101-SO3Na was enhanced by introducing C-H···N hydrogen bonds to strengthen interaction forces and -SO3Na groups to adjust surface charge and enhance electrostatic attraction. This modification and the substantial specific surface area (998 m2·g-1) of the metal-organic framework markedly enhanced the enrichment efficiency of MIL-101. The proposed method based on MIL-101-SO3Na exhibited a minimal detection threshold (0.04-0.87 ng·L-1), an extensive linear spectrum (1-2000 ng·L-1), and notable accuracy (a variation of 3.02-11.8%) in water and drink samples. NNI concentrations between 0.25 and 24.2 ng·L-1 in fruit juice and tea samples were accurately identified using the proposed method, demonstrating its feasibility in practical applications. The postmodification of MIL-101-SO3Na is an exceptional and promising approach for the sensitive detection of ultratrace NNI levels in complex matrices.

Overview of Liquid Sample Preparation Techniques for Analysis, Using Metal-Organic Frameworks as Sorbents

The preparation of samples for instrumental analysis is the most essential and time-consuming stage of the entire analytical process; it also has the greatest impact on the analysis results. Concentrating the sample, changing its matrix, and removing interferents are often necessary. Techniques for preparing samples for analysis are constantly being developed and modified to meet new challenges, facilitate work, and enable the determination of analytes in the most comprehensive concentration range possible. This paper focuses on using metal-organic frameworks (MOFs) as sorbents in the most popular techniques for preparing liquid samples for analysis, based on liquid-solid extraction. An increase in interest in MOFs-type materials has been observed for about 20 years, mainly due to their sorption properties, resulting, among others, from the high specific surface area, tunable pore size, and the theoretically wide possibility of their modification. This paper presents certain advantages and disadvantages of the most popular sample preparation techniques based on liquid-solid extraction, the newest trends in the application of MOFs as sorbents in those techniques, and, most importantly, presents the reader with a summary, which a specific technique and MOF for the desired application. To make a tailor-made and well-informed choice as to the extraction technique.

Investigation of Eucalyptus camaldulensis and Tamarix aphylla species' capacities for methylene blue removal in wastewater and heavy metal remediation in soil

In the contemporary landscape, the reuse of wastewater holds paramount significance. Concurrently, wastewater carries an array of pollutants encompassing chemical dyes and heavy metals. This study delves into the potential of Tamarix aphylla (TA) and Eucalyptus camaldulensis (EC) species for mitigating heavy metals in soil and eliminating methylene blue dye (MB) from wastewater. The research begins with assessing the dye adsorption process, considering pivotal factors such as initial pH, adsorbent dosage, initial dye concentration, and contact time. Outcomes reveal EC's superiority in dye removal compared to TA. As a bioremediation agent, EC exhibits a 90.46% removal efficacy for MB within 15 min, with pH 7.0 as the operative condition. Equilibrium analysis employs Temkin (T), Freundlich (F), and Langmuir (L) isotherms, revealing an excellent fit with the L isotherm model. The study delves further by probing surface adsorption kinetics through pseudo-first-order (PFO) and pseudo-second-order (PSO) models. Furthermore, to discern the divergent impacts of EC and TA on soil heavy metal reduction, soil samples were collected from three distinct zones: an untouched control area, alongside areas where EC and TA were cultivated at the Yazd wastewater site in Iran. Heavy metal levels in the soil were meticulously assessed through rigorous measurement and statistical scrutiny. The findings spotlight TA-cultivated soil as having the highest levels across all examined factors. Ultimately, EC emerges as the superior contender, proficiently excelling in both MB eliminations from wastewater and heavy metal amelioration in the soil, positioning it as the preferred phytoremediation agent.

Superlong Metal-Organic Framework Micro-/Nanofibers for Selective Vitamin Absorption

Superlong MOF-74-type micro/nanofibers, which have aspect ratios much higher than 200, are synthesized via nanoparticulate MOF-mediated recrystallization. Co-MOF-74 microfibers have high crystallinity, whereas Co-MOF-74-II nanofibers are composed of nanocrystals and amorphous phases, even though they have nanofibrous morphology. Both MOFs consist of plenty of micropores with diameters in the range of 1.0 to 2.0 nm, and they exhibit high thermal stability with a decomposition temperature higher than 260.0 °C. The MOFs are demonstrated for selective absorption of some vitamins including riboflavin, folic acid, and 5-methyltetrahydrofolate. Co-MOF-74-II nanofibers can efficiently absorb riboflavin and folic acid from their aqueous solution with absorption percentages approaching 90.0%, and they have enhanced capability for absorbing tocopherol in methanol. The micro/nanofibrous morphology, together with the capability for selective vitamin absorption, makes the novel MOFs highly promising for applications in micro-solid-phase extraction.

Synthesis of multiwalled carbon nanotubes/metal-organic framework composite for the determination of neonicotinoid pesticides in medicine and food homology products

A novel extraction adsorbent composite of MWCNTs/NH2-MIL-101(Fe) was synthesized, and was used to extract 6 kinds of neonicotinoid pesticides in medicine and food homology products. The composite was characterized by scanning electron microscope (SEM), fourier transform-infrared (FT-IR) spectroscopy, and X-ray powder diffraction (XRD). MWCNTs were enveloped around MOFs to provide physical support for the crystal structure. The adsorbent has higher adsorption capacity and reusability than pure NH2-MIL-101(Fe). Combined with UPLC-MS/MS, the method showed the low limit of detection (LOD) and limit of quantitation (LOQ) of 0.01-0.07 μg/kg and 0.04-0.22 µg/kg, respectively. It exhibited high extraction recovery of 77.86-101.10% for neonicotinoid pesticides in spiked samples. Meanwhile, this novel method could be successfully employed for the detection of other medicine and food homology products. Compared with previous reports, this method has advantages in detection limit and extraction recovery, indicating that it can be a preferential choice for the detection of neonicotinoid pesticides.

Determination of Lincomycin in Milk Using Cu-Based Metal-Organic Framework Adsorbent and Liquid Chromatography-Tandem Mass Spectrometry

Antibiotic drug residues can adversely affect the human body. Lincomycin is a common veterinary drug that can form residues in foods of animal origin. However, the detection of trace residue levels of lincomycin residues in real samples is challenging. Here, a simple solid phase extraction (SPE) method was developed for the enrichment of lincomycin from cow milk samples before its detection by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The adsorbent used in the SPE was a Cu-based metal-organic framework (Cu-MOF) prepared by the solvothermal synthesis approach. The prepared MOFs were characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), differential thermogravimetric analysis (TG-DTA), and N2 adsorption-desorption experiments. The adsorption capacity (adsorption equilibrium, extraction time, pH), and elution solvent parameters were investigated. Under the optimized conditions of the HPLC-MS/MS method, lincomycin was detected in the linear range of 10-200 g/L with a detection limit of 0.013 ng/mL. Commercial milk samples were spiked with lincomycin, and a recovery rate between 92.3% and 97.2% was achieved. Therefore, the current method can be successfully applied for the enrichment and determination of lincomycin from milk samples.

Phenylboronic acid-functionalized magnetic metal-organic framework nanoparticles for magnetic solid phase extraction of five benzoylurea insecticides

This research involves the construction of a phenylboronic acid-functionalized magnetic UiO-66 metal-organic framework (MOF) nanoparticle (CPBA@UiO-66@Fe₃O₄). Its design is primarily for the magnetic solid phase extraction (MSPE) of benzoylurea insecticides. An organic ligand, 2-amino terephthalic acid (2-ATPA), facilitated the introduction of amino groups while keeping the original crystal structure of UiO-66 intact. The constructed UiO-66 MOF showcases a porous structure and extensive surface area, thereby providing an optimal platform for further functionalization. The employment of 4-carboxylphenylboronic acid as a modifier notably amplified the extraction efficiency for benzoylureas. This improvement was due to the formation of B-N coordination and other secondary interactions. By integrating this with high-performance liquid chromatography (HPLC), we established a quantitative analytical method for benzoylurea insecticides. This method achieved a wide linear range (2.5-500 μg L^-1 or 5-500 μg L^-1), satisfactory recoveries (83.3-95.1%), and acceptable limits of detection (LODs: 0.3-1.0 μg L^-1). The developed method proved successful when applied to six tea infusion samples, representing China's six major tea categories. Semi-fermented and light-fermented tea samples demonstrated relatively higher spiking recoveries.

Nanocomposites of Copper Trimesinate and Graphene Oxide as Sorbents for the Solid-Phase Extraction of Organic Dyes

A nanocomposite based on graphene oxide and copper trimesinate was obtained by the in situ method. The samples have permanent porosity and a microporous structure with a large surface area corresponding to the adsorption type I. A study of the adsorption properties of the obtained composites with respect to organic dyes (malachite green, indigo carmine, brilliant green, Rose Bengal, crystal violet) showed that adsorption largely depends on the content of graphene oxide in the composites. The complex is an effective sorbent for the extraction of cationic and neutral organic dyes when the content of graphene oxide in the nanocomposite is 20% of the calculated copper trimesinate due to electrostatic forces of interaction. For anionic dyes, the maximum adsorption is achieved when using a composite containing 5% graphene oxide due to the predominance of physical sorption. Experimental results show that the obtained sorbent can be used for extraction in a wide pH range, illustrating the excellent pH window offered by this adsorbent. Kinetics data were properly fitted with the pseudo-second-order model. Equilibrium data were best correlated with the Freundlich model. The process was endothermic and spontaneous in nature. The composite makes it possible to achieve a maximum sorption of 393 mg/g, which is a sufficiently high value for the absorption of dyes.

Well-design and synthesis of a water- and heat-resistant UiO-67@CNTs composite for Congo red efficient capture

MOFs (metal-organic frameworks) significantly suffer from water- and heat instable issues, restricting their practical application, such as the capture of hazardous anionic dyes (e.g. Congo red, CR) from water. In the present contribution, a series of novel composites (UiO-67@CNTs) composed of microporous UiO-67 (Zr6O4(OH)4(CO2)12) and mesoporous CNTs (carbon nanotubes) have been innovatively synthesized by an in-situ hydrothermal reaction strategy. This UiO-67@CNT impressively retains structural integrity whether contacted with strong acid, distilled water, and strong alkali conditions even for 20 days. Due to the existence of CNT, its heat stability can reach up to 480 °C, which is superior to that of UiO-67. Open Zr(IV) sites, mesoporous, and high surface area in the structure of UiO-67@CNTs play associative effects for CR capture ability. CR uptakes over (5.0)UiO-67@CNTs can reach 1024 mg/g, exceeding some other previous adsorbents in literature. Importantly, UiO-67@CNTs could retain a remarkable CR capture ability even after the fifth cycle. This work expands views for water-heat resistant MOF-based composite with excellent ability of CR capture.

Series of Stable Anionic Lanthanide Metal-Organic Frameworks as a Platform for Pollutant Separation and Efficient Nanoparticle Catalysis

Eight new stable porous lanthanide metal-organic frameworks (Ln-OFs), namely, [Ln₂(BPTC)₂][(CH₃)₂NH₂]₂ [Ln = Ho (1), Eu (2), Gd (3), Dy (4), Er (5), Tm (6), Yb (7), Lu (8)], were prepared by 3,3',5,5'-biphenyltetracarboxylic acid (H₄BPTC) and lanthanide ions by solvothermal reactions. Complexes 1-8 show a three-dimensional (3D) 6,6-connected network {4¹²·6³}·{4⁸·6⁶·8} topology based on binuclear (Ln₂) clusters and feature a one-dimensional curving porous channel occupied by exchangeable dimethylamine cations ([(CH₃)₂NH₂]⁺) in the 3D anionic frameworks. The occupied [(CH₃)₂NH₂]⁺ in the anionic channels exhibited excellent ion-exchange ability, which is favorable to Pd²⁺ and cationic dye adsorption. Consequently, 1-8 were used to load Pd nanoparticles to catalyze the reduction of nitrophenols and adsorb and desorb methyl blue (MB). The catalytic reaction efficiencies of Pd@1-8 were higher than that of Pd/C (5 wt %) in the hydrogenation reaction of p-nitrophenol (p-NP). Moreover, Pd@1 exhibited good cycle stability and achieved nearly 100% p-NP conversion after eight cycles. Meanwhile, compound 1 also exhibited a high adsorption ability of MB, possessing an adsorption capacity of 1.41 g·g^-1 (second only to 1.49 g·g^-1 reported in the literature) selectively over rhodamine B (RhB) and methyl orange (MO) in aqueous solutions. Remarkably, the skeleton of 1 remained stable after four adsorption-desorption cycles of MB in aqueous solution.

Application of β-Cyclodextrin metal-organic framework/titanium dioxide hybrid nanocomposite as dispersive solid-phase extraction adsorbent to organochlorine pesticide residues in honey samples

A simple and efficient dispersive solid-phase extraction (D-SPE) method combined with gas chromatography tandem mass spectrometry (GC-MS/MS) was developed to determine organochlorine pesticides (OCP) in honey. Firstly, a type of hybrid nanocomposite (CD-MOF/TiO₂) was prepared by grafting a metal-organic framework material synthesized with cyclodextrin as an organic ligand onto titanium dioxide. Then, the CD-MOF/TiO₂ was used as a D-SPE adsorbent to extract the OCP, and the effects of the amount of adsorbent, ultrasonic time, vortex time, pH, and salinity on the extraction were investigated using Plackett-Burman design and Box-Behnken Design. Under the optimized adsorption and desorption conditions, an analysis method that combined D-SPE with GC-MS/MS was established. The linear ranges of 14 OCP are 1-500 μg kg^-1 and the correlation coefficients are between 0.9991 and 1.000. The limits of detection and quantification vary from 0.01 to 0.04 μg kg^-1 and 0.04 to 0.12 μg kg^-1, respectively. The intra-day and inter-day precision of this method are suitable (RSDs% less than 11.3%). The established CD-MOF/TiO₂ / D-SPE method was used for the extraction of OCP in honey samples with recovery in the range of 76.4 to 114.3%. The results demonstrate that the CD-MOF/TiO₂ has a good selective enrichment ability for OCP and is suitable for the D-SPE pretreat of honey sample analysis.

A new cotton functionalized with iron(III) trimer-like metal framework as an effective strategy for the adsorption of triarylmethane dye: An insight into the dye adsorption processes

A new Cotton@Fe-BTC composite formed by Fe-BTC (BTC-H3: trimesic acid) metal framework (Fe-BTC MOF loading as high 38 wt %) supported by cellulose fiber is synthesized in aqueous media using a simple and green preparation method, described for the first time in this manuscript. This new strategy relies on the synergetic effect of the pure cellulose and MOFs frameworks resulting in hybrid nanofibers of MOFs@cellulose composite. A complete characterization of the composite material reveals its structural similarity to MIL-100(Fe), a Fe-BTC material. The Cotton@Fe-BTC composite potential use as an eco-friendly and low-cost adsorbent was evaluated for its adsorptive performance for the removal of dye belonging to the triarylmethane dye family (Malachite Green (MQ), Brilliant Green (BG), Pararosaniline (PR), Basic Fuchsine (BF), Crystal Violet (CV), Methyl Green (Met-G), Victoria Blue B (VB), Acid Fuchsin (AF) and Aniline Blue (AB)) in aqueous solution. The fast kinetics and high dye removal efficiencies (>90%) obtained in aqueous solutions. The structure of Cotton@Fe-BTC network, contributed to the remarkable adsorption properties towards a variety of triphenylmethanedye. The interparticle studies showed two main steps in the dye adsorption processes, with the exception of AF and BG. The equilibrium adsorption capacities qe (mg/g) follow the order: AF (3.64) Collapse

Key Words

• Adsorption
• Fe-BTC
• Natural cotton
• Solvation/desolvation penalty processes
• Triphenylmetane dye
• Water

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Affiliation(s)

J.E. Conde-González Departamento de Química, Unidad Departamental de Química Analítica, Facultad de Ciencias, Universidad de La Laguna, Tenerife, Spain
P. Lorenzo-Luis Inorganic Chemistry Area, Section of Chemistry Faculty of Science, Tenerife, Spain Instituto Universitario de Bio-Orgánica “Antonio González”, University of La Laguna, Tenerife, Spain
V. Salvadó Department de Química, Facultat de Ciències, Universitat de Girona, C/ M Aurèlia Capmany, 69, 17003 Girona, Spain
J. Havel Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5/A14, 625 00 Brno, Czech Republic
E.M. Peña-Méndez Departamento de Química, Unidad Departamental de Química Analítica, Facultad de Ciencias, Universidad de La Laguna, Tenerife, Spain

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