Applications of multifunctional zirconium-based metal-organic frameworks in analytical chemistry: Overview and perspectives

Colorimetric sensor comprising metal-organic frameworks and molecularly imprinted polymers for aflatoxin B1 detection in agricultural commodities

A novel colorimetric sensor was developed by integrating cerium metal-organic frameworks with molecularly imprinted polymers (Ce-MOF@MIP) for the highly selective and sensitive detection of Aflatoxin B1. The resulting composite leverages the peroxidase-like activity of cerium metal-organic frameworks to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine in the presence of hydrogen peroxide, while imprinted cavities confer specificity toward Aflatoxin B1. Detection is facilitated by monitoring the inhibition of the composite's catalytic activity, manifesting as colorimetric changes that can be quantified using ImageJ. The sensor exhibits two linear detection ranges (0.5-5 ng mL-1 and 5-50 ng mL-1) and achieves a detection limit of 0.25 ng mL-1. When applied to agricultural samples (peanuts, chicken feed, and corn), recoveries ranged from 95.1 % to 109.4 %, surpassing high-performance liquid chromatography according to a paired t-test. Taken together, these findings highlight the sensor's high sensitivity, selectivity, and robustness, underscoring its promise in food safety applications and broader mycotoxin surveillance.

A fluorescent probe based on a luminescent metal-organic framework for the sensitive detection of histamine in aquatic products

An effective way to prevent histamine poisoning is to assess the safety of aquatic products, and hence, developing a new method for detecting histamine is particularly important. In this study, a fluorescence probe (AgNPs@PCN-224) was constructed for the sensitive detection of histamine by utilizing the mesoporous structure of a zirconium porphyrin metal-organic framework (PCN-224) loaded with silver nanoparticles (AgNPs). Because PCN-224 and AgNPs were close to each other, there was a fluorescence resonance energy transfer between the two substances, resulting in fluorescence quenching. At this point, under the action of diamine oxidase, the decomposition product of histamine (hydrogen peroxide) etched the silver nanoparticles onto the surface of PCN-224, and the fluorescence of PCN-224 was recovered. Under optimal conditions, it was confirmed that the fluorescence intensity of the probe was positively correlated with the histamine concentration in the range of 10-100 μM, with a correlation coefficient of 0.9527, and the detection limit was calculated to be 0.033 nM. The detection performance for hydrogen peroxide was also investigated, and the results demonstrated that the probe was suitable for dual-substance detection of both histamine and hydrogen peroxide. Finally, when used for the detection of grass carp samples, it was found that the recovery rate ranged from 98% to 110%, with a relative standard deviation below 8%. The findings confirmed the reliability of the AgNPs@PCN-224 fluorescent probe established in this study for the detection of histamine in aquatic samples.

Advancing analytical chemistry with carbon quantum dots: a comprehensive review

Carbon Quantum Dots (CQDs) have gained significant attention as versatile nanomaterials in analytical chemistry due to their strong fluorescence, high sensitivity, and biocompatibility features. This review explores the synthesis, functionalization, and broad applications of CQDs in various analytical domains, including bioimaging, diagnostics, and environmental monitoring. CQDs' unique properties, such as tunable emission and ease of surface modification, enhance their performance in fluorescence and electrochemical sensing. CQDs present emerging applications in single-cell analysis, point-of-care diagnostics, and food safety. Technological advancements in green synthesis and hybrid nanomaterial integration are paving the way for more sustainable, efficient, and scalable analytical tools. However, challenges related to reproducibility, stability, and large-scale production persist, highlighting the need for continued research. The present review provides a comprehensive overview of CQDs' impact, emphasizing their potential to transform analytical chemistry through innovative applications and future breakthroughs.

Metal-organic framework-801@MXene nanocomposites as a coating for headspace solid-phase microextraction of methadone and tramadol from biological samples via gas chromatography-mass spectrometry

MOF-801@MXene nanocomposites are introduced as a new solid-phase microextraction coating. This structure was easily prepared by one-pot solvothermal route. The MOF-801@MXene, MOF-801, and MXene were characterized by various analysis techniques such as field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray powder diffraction, and Brunauer-Emmett-Teller. The coating was used in the headspace solid-phase microextraction of methadone and tramadol in biological samples. The separation and determination of the analytes were performed by gas chromatography-mass spectrometry. The effective parameters on the extraction efficiency of the analytes, such as extraction time and temperature, desorption time and temperature, salt concentration, and NaOH concentration, were optimized by experimental design method. Under optimal conditions, low limits of detection in the range 0.03-0.15 µg L-1, wide linearity in the range 0.10-250.00 µg L-1, and good reproducibility (RSD = 5.3 to 7.4% for n = 3) were achieved. Under optimal conditions, microextraction of methadone and tramadol was performed in real hair, urine, and plasma samples, and satisfactory results were obtained.

Fabrication of a magnetic functionalized chitosan hydrogel for effective extraction of aflatoxins from cereals

A magnetic adsorbent was synthesized by coupling magnetic nanoparticles, UiO-66-NH2 and 1-butyl-trimethylimidazole bromide ([BMIM][Br]) to chitosan (CS)-based composite conveniently. A series of modern characterizations were employed to assess its properties. The results showed that UiO-66-NH2 was uniformly distributed within the composite via in-situ growth, which can enhance the porosity obviously. The introduction of various ligands enables the composite to exhibit excellent extraction performance for four aflatoxins (AFs) through multiple interactions. The adsorption mechanism was elucidated and the main factors affecting extraction efficiency were evaluated. Under optimal conditions, the limits of detection (LODs) ranged from 0.08 to 0.56 μg/kg. The established method was successfully utilized to determine AFs from cereal samples (rice, glutinous rice, wheat, soybean, paddy, and corn) with satisfactory recovery of 77% ∼ 119% with relative standard deviations (RSDs) of 1.0% ∼ 11.7% (n = 5). The adsorbent demonstrated sufficient robustness for repeated use at least six times without obvious damage of extraction property.

A zirconium metal-organic framework functionalized with a S/N containing carboxylic acid (MOF-808(Zr)-Tz) as an efficient sorbent for the ultrafast and selective dispersive solid phase micro extraction of chromium, silver, and rhodium in water samples

Metal-organic frameworks (MOFs) are good adsorbents for targeted chemicals with their adjustable properties. Herein, we prepared a zirconium based MOF (MOF-808(Zr)) and functionalized it employing 2-mercapto-4-methyl-5-thiazolacetic acid (MOF-808(Zr)-Tz). The prepared MOFs were characterized by XRD, FTIR, SEM-EDX, TGA, N2 sorption, zeta potential measurements, and elemental analysis. The surface area of MOF-808(Zr)-Tz was 1348 m2/g. Dispersive solid-phase micro-extraction (D-SPµE) method based on MOF-808(Zr)-Tz was firstly developed and applied to the extraction of chromium, silver, and rhodium in waters. The determination of the analytes was done by FAAS. The optimal pH and eluent for analytes were 7.0 and 3 mL of 2 mol L-1 HCl, respectively. The contact times were 1 min for adsorption and 3 min for elution. The LOD and PFs of the D-SPμE for analytes were 2.3 μg L-1 and 13.3 for chromium, 2.1 μg L-1 and 13.3 for silver, and 3.1 μg L-1 and 13.3 rhodium, respectively. The D-SPμE method was verified with analyses of NW-TMDA-54.6 Lake water and SPS-WW1 Batch 114 Wastewater and with spiked dam water, river water, well water, sea water, and wastewater. The recoveries of the analytes changed from 89 to 108 %. The results indicated that the method is selective, simple, effective, and rapid for extracting chromium(III), silver(I) and rhodium(III) in waters.

Fabrication of a biochar-doped monolithic adsorbent and its application for the extraction and determination of coumarins from Angelicae Pubescentis Radix

A monolithic adsorbent was designed aiming to the structure of osthole and columbianadin, and fabricated using diallyl phthalate as the monomer and ethylene dimethacrylate as the crosslinker with the addition of bamboo biochar, via polymerization reaction in a stainless-steel tube. The prepared composite adsorbent packed in the tube was used as a solid-phase extraction column for the extraction and determination of two coumarins (osthole and columbianadin) in Angelicae Pubescentis Radix, combing with a C18 analytical column through an HPLC instrument, which show excellent matrix-removal ability and good selectivity to osthole and columbianadin. Furthermore, the present adsorbent shows good applicability, which was used for the extraction of osthole from Duhuo Jisheng Pill. Compared to the commercial C18 and phenyl adsorbent, the present adsorbent own better selectivity and higher resolution. These results attributed to the enhanced specific surface area (141 m2/g) and enriched interaction sites of the resulting composite adsorbent, due to the doping of bamboo biochar, which can produce hydrogen bond, dipole-dipole, π-π and hydrophobic force interactions with the osthole and columbianadin. The methodology validation indicated that the present method showed good precision and good accuracy, and the composite adsorbent showed good preparative repeatability, which can be reused for no less than 100 times with the relative standard deviation ≤4.6 % (n = 100). The present work provided a simple and efficient method for the extraction and determination osthole and columbianadin from Angelicae Pubescentis Radix.

Biosensors based on core-shell nanoparticles for detecting mycotoxins in food: A review

Mycotoxins are toxic metabolites produced by fungi in the process of infecting agricultural products, posing serious threat to the health of human and animals. Thus, sensitive and reliable analytical techniques for mycotoxin detection are needed. Biosensors equipped with antibodies or aptamers as recognition elements and core-shell nanoparticles (NPs) for the pre-treatment and detection of mycotoxins have been extensively studied. By comparison with monocomponent NPs, core-shell nanostructures exhibit unique optical, electric, magnetic, plasmonic, and catalytic properties due to the combination of functionalities and synergistic effects, resulting in significant improvement of sensing capacities in various platforms, such as surface-enhanced Raman spectroscopy, fluorescence, lateral flow immunoassay and electrochemical sensors. This review focused on the development of core-shell NPs based biosensors for the sensitive and accurate detection of mycotoxins in food samples. Recent developments were categorised and summarised, along with detailed discussion of advantages and shortcomings. The future potential of utilising core-shell NPs in food safety testing was also highlighted.

Metal-organic frameworks as promising solid-phase sorbents for the isolation of third-generation synthetic cannabinoids in biological samples

In this work, metal-organic frameworks (MOFs) were used for the first time as solid-phase extraction (SPE) sorbents for the isolation of synthetic cannabinoids (SCs) from oral fluids and subsequently quantified by LC-fluorescence detection (FLD). In this context, different MOF families were synthesized and tested under SPE mode. UiO-66 was the family selected, being the amino functionalized (NH₂-UiO-66) the best candidate in terms of extraction performance. After the method optimization, several analytical parameters of interest were obtained, reaching limits of detection (LODs) as low as 0.6-0.8 μg L^-1 and precision values (expressed as RSD) lower than 10.6%. The developed method was successfully applied to the determination of 8 SCs in different oral fluids at three spiked levels with recoveries between 67 and 114%. This method claims to be a real alternative for screening purposes, being a cost-effective procedure due to the price of the sorbent (<0.5 €/cartridge) and its recyclability (up to 12 uses), among others good features.

Rational design of a novel MOF-based ternary nanocomposite for effectively monitoring harmful organophosphates in foods and the environment

Methyl parathion (MP) is a widely used organophosphate insecticide that is extremely toxic due to its ability to irreversibly inhibit acetylcholinesterase in the body and persistently accumulate in the environment. Timely detection of MP can prevent harmful residue exposure to humans. Therefore, the development of fast, efficient electrochemical methods to detect trace MP has been highly beneficial for monitoring harmful residues in foods and environment to ensure food safety and ecological conservation. Herein, a novel hybrid metal-organic framework (MOF) nanocomposite composed of Pt nanoparticles (PtNPs), multi-walled carbon nanotubes (MWCNTs), and UiO-66-NH₂ (PtNPs/UiO-66-NH₂/MWCNTs) was rationally designed and prepared by a facile two-step strategy for the sensitive determination of MP. The synergistic effects are illustrated in detail using XRD, XPS, FTIR, TEM, and SEM studies as well as electrochemical technologies such as CV, EIS, and DPV. In addition, the performance of the ternary nanocomposite for detecting MP was investigated by comparing it with the binary-component one. The results showed that the PtNPs/UiO-66-NH₂/MWCNT-based electrochemical sensor exhibited outstanding sensitivity of 21.9 μA μM^-1 cm^-2, satisfactory low detection limit of 0.026 μM and wide linear range of 0.11-227.95 μM for MP analysis. Furthermore, the fabricated sensor delivered distinguished freedom from interferences, outstanding regeneration ability, and adequate recoveries for fresh foods and river water samples. In conclusion, the proposed PtNPs/UiO-66-NH₂/MWCNT-based sensor provides a potentially useful analytical tool for determining hazardous residues of OPs in foods and the environment.

Lotus-like Ni@NiO nanoparticles embedded porous carbon derived from MOF-74/cellulose nanocrystal hybrids as solid phase microextraction coating for ultrasensitive determination of chlorobenzenes from water

Lotus-like Ni@NiO embedded porous carbons (Ni@NiO/PCs) were fabricated by pyrolysis of MOF-74/cellulose nanocrystal hybrids, and used as a solid phase microextraction (SPME) coating for ultrasensitive determination of chlorobenzenes (CBs) from water combined with gas chromatography-mass spectrometry. Owing to its abundant chemical groups, high porosity, and excellent thermal stability, the as-prepared Ni@NiO/PCs presented superior extraction performance compared to commercial SPME coatings. Notably, Ni@NiO/PCs derived from MOF-74/CNC hybrids presented higher extraction efficiencies towards CBs than that derived from pristine CNC and MOF-74 due to the formation of micro/mesopores and more abundant oxygen-containing groups. Under the optimum extraction conditions, the proposed analytical method presented wide linearity range (0.5-1500 ng L^-1), ultra-low detection of limit (0.005-0.049 ng L^-1), and excellent precision with relative standard deviations of 4.7-9.2% for a single fiber and 8.8-10.9% for 5 fibers, and long lifetime (≥160 times). The proposed analytical method was finally applied for determination of CBs from real water samples, and the recoveries were in the range of 93.2-116.8% towards eight CBs. This study delivered a novel and efficient sorbent as SPME coating to extraction and determination of CBs from water.

Metal-Organic Framework-Based Materials for Adsorption and Detection of Uranium(VI) from Aqueous Solution

The steady supply of uranium resources and the reduction or elimination of the ecological and human health hazards of wastewater containing uranium make the recovery and detection of uranium in water greatly important. Thus, the development of effective adsorbents and sensors has received growing attention. Metal-organic frameworks (MOFs) possessing fascinating characteristics such as high surface area, high porosity, adjustable pore size, and luminescence have been widely used for either uranium adsorption or sensing. Now pertinent research has transited slowly into simultaneous uranium adsorption and detection. In this review, the progress on the research of MOF-based materials used for both adsorption and detection of uranium in water is first summarized. The adsorption mechanisms between uranium species in aqueous solution and MOF-based materials are elaborated by macroscopic batch experiments combined with microscopic spectral technology. Moreover, the application of MOF-based materials as uranium sensors is focused on their typical structures, sensing mechanisms, and the representative examples. Furthermore, the bifunctional MOF-based materials used for simultaneous detection and adsorption of U(VI) from aqueous solution are introduced. Finally, we also discuss the challenges and perspectives of MOF-based materials for uranium adsorption and detection to provide a useful inspiration and significant reference for further developing better adsorbents and sensors for uranium containment and detection.

Research Progress of UiO-66-Based Electrochemical Biosensors

UiO-66, as a member of the MOFs families, is widely employed in sensing, drug release, separation, and adsorption due to its large specific surface area, uniform pore size, easy functionalization, and excellent stability. Especially in electrochemical biosensors, UiO-66 has demonstrated excellent adsorption capacity and response signal, which significantly improves the sensitivity and specificity of detection. However, the existing application research remains in its infancy, lacking systematic methods, and recycling utilization and exclusive sensing of UiO-66 still require further improvement. Therefore, one of the present research objectives is to explore the breakthrough point of existing technologies and optimize the performance of UiO-66-based electrochemical biosensors (UiO-66-EBs). In this work, we summarized current experimental methods and detection mechanisms of UiO-66-EBs in environmental detection, food safety, and disease diagnosis, analyzed the existing problems, and proposed some suggestions to provide new ideas for future research.

Group 4 Metal-Based Metal—Organic Frameworks for Chemical Sensors

Metal-organic frameworks (MOFs) have attracted great attention for their applications in chemical sensors mainly due to their high porosity resulting in high density of spatially accessible active sites, which can interact with the aimed analyte. Among various MOFs, frameworks constructed from group 4 metal-based (e.g., zirconium, titanium, hafnium, and cerium) MOFs, have become especially of interest for the sensors requiring the operations in aqueous media owing to their remarkable chemical stability in water. Research efforts have been made to utilize these group 4 metal-based MOFs in chemosensors such as luminescent sensors, colorimetric sensors, electrochemical sensors, and resistive sensors for a range of analytes since 2013. Though several studies in this subfield have been published especially over the past 3–5 years, some challenges and concerns are still there and sometimes they might be overlooked. In this review, we aim to highlight the recent progress in the use of group 4 metal-based MOFs in chemical sensors, and focus on the challenges, potential concerns, and opportunities in future studies regarding the developments of such chemically robust MOFs for sensing applications.

High-Efficiency and Versatile Approach To Fabricate Diverse Metal-Organic Framework Coatings on a Support Surface as Stationary Phases for Electrochromatographic Separation

A large number of metal-organic frameworks (MOFs) have exhibited increasingly wide utilization in the field of chromatographic separation owing to their intrinsic fascinating properties. However, the previous studies on supported MOF coating-based chromatographic separation focused only on the synthesis and chromatographic performance of a certain kind of supported MOF coatings as stationary phases using the multiple-step, complicated, and time-consuming modification methods, which severely impeded the widespread application of MOFs in separation science. Herein, a high-efficiency and versatile methodology toward diverse supported MOF coating-based stationary phases to achieve high-efficiency chromatographic separation was first reported based on the immobilized cysteine (Cys)-triggered in situ growth (ICISG) strategy. As a proof-of-concept demonstration, four types of MOF crystals consisting of different ligands and metal ions (Zn²⁺, Cu²⁺, Fe³⁺, and Zr⁴⁺) were conveniently and firmly grown on a Cys-modified capillary using the ICISG strategy and employed as the functional stationary phase for electrochromatographic separation. A broad variety of neutral, acidic, and basic compounds were all separated in a highly efficient manner on the developed four MOF-coated columns. The maximum theoretical plate number for Cys-MIL-100(Fe)@capillary was close to 1.0 × 10⁵ plates/m, and the intraday, interday, and column-to-column repeatabilities of retention times for the four MOF-modified columns were all less than 5.25%. More interestingly, the diversified separation performance of the developed MOF-coated columns indicated that the preparation strategy and the skeletal structure of the MOF coating-based stationary phases have a significant influence on the electrochromatographic separation performance and column capacity. Benefiting from the strong universality and high applicability of the developed ICISG strategy, the present study provides an effective route to facilitate the design and fabrication of novel functional MOF-based chromatographic stationary phases.