Lanthanide Metal-organic Frameworks Research Articles

Lanthanide MOFs based portable fluorescence sensing platform: Quantitative and visual detection of ciprofloxacin and Al3+

In the current context of water environmental monitoring and pollution control, there's a crucial need for rapid and simple methods to detect multi-pollutant. We herein report an easy one-step hydrothermal synthesis method to produce Eu-based metal-organic frameworks (Eu MOFs), which was used as a fluorescent probe to detect the aquatic environmental pollutants of ciprofloxacin (CIP) and aluminum ions (Al3+). This fluorescent sensor enabled the cascade detection of CIP and Al3+ through fluorescence enhancement and ratio fluorescence response, respectively. The introduction of CIP significantly turned on the characteristic fluorescence of Eu MOFs at 595 nm and 616 nm through the “antenna effect”. Based on this, the sensor enables quantitative detection of CIP within a linear range of 0–120 μM with a LOD as low as 50.421 nM. In the presence of Al3+, the fluorescence emission of Eu MOFs-CIP was sharply turned off due to strong Al3+ coordination with CIP, while the blue fluorescence emission of CIP was remarkably enhanced. And thus allowing ratio fluorescence quantitative detection of Al3+ (LOD = 2.681 μM). The introduction of CIP and Al3+ in cascade resulted in distinct fluorescence color changes from colorless to red and eventually to blue, exhibiting pronounced fluorescence characteristics. This observable phenomenon enables the visual detection of CIP and Al3+ in both aqueous phase and paper test strips. By combining the analysis of fluorescence chromaticity with the use of a smartphone, the fluorescence color of test papers allows for simple quantitative determination, which provides a convenient and accessible approach for quantifying CIP and Al3+ in water environments.

Adsorptive separation of Xe/Kr mixtures by microporous lanthanide metal-organic frameworks with high thermal stability

Efficient separation of Xenon (Xe) and Krypton (Kr) is a significant process for their wide industrial applications and potential environmental concerns. Owing to the inert atomic gases (Xe and Kr) nature with similar physical and chemical properties, it is a great challenge to achieve efficient separation of the Xe/Kr mixture. Herein, we report a series of microporous lanthanide based metal-organic frameworks Ln (BTC) (H2O)·(DMF)1.1 (Ln-MOF) (Dy-BTC (1), Er-BTC (2), and Yb-BTC (3)) with ultrahigh thermal stability for adsorptive Xe/Kr separation. These three isostructural Ln-MOFs consisted of lanthanide metal ions and 1,3,5-benzene dicarboxylate ligands that possess a square channel with pore sizes of 6–7 Å. By substitution of Ln ions, Yb-BTC shows the smallest pore size among the three compounds which enables its obvious higher Xe/Kr selectivity compared with the other two Ln-MOFs. Yb-BTC exhibits a moderately high Xe uptake of 2.5 mmol/g (298 K and 1 bar), and a significantly high Xe/Kr uptake ratio of 3.8, indicative of its great potential for separation of Xe/Kr mixture. The effective Xe/Kr separation ability of Yb-BTC was also confirmed by a breakthrough experiment.

Construction of Multifunctional Luminescent Lanthanide MOFs for Luminescent Sensing of Temperature, Trifluoroacetic Acid Vapor and Explosives.

Metal-organic frameworks (MOFs) with multifunctional and tunable optical properties have unique advantages in the field of sensing, and the structure and properties of MOFs are significantly influenced by the ligands. In this study, a Y-type tricarboxylic acid ligand containing amide bonds was synthesized through functional guidance, and three isomorphic and heterogeneous three-dimensional MOFs (Eu-MOF, Tb-MOF, and Gd-MOF) were obtained by solvothermal reaction. Further studies revealed that both the Tb-MOF and Eu-MOF could selectively detect picric acid (PA). The luminescence quenching of the two MOFs by PA was attributed to competing absorption and photoelectron energy transfer mechanisms. In addition, due to the energy transfer between Tb and Rhodamine B, Rhodamine B was encapsulated into Tb-MOF. The obtained material exhibited a linear relationship between the temperature parameters I544/I584 and temperature within the range of 280-400 K, the correlation coefficient (R2) reached an impressive value of 0.999, and the absolute sensitivity of the sample used for temperature sensing was 1.534% K-1. What is more, the material exhibited a good response to trifluoroacetic acid vapor, which suggests the potential of the material for temperature sensing and detection of trifluoroacetic acid vapor. The designed and investigated strategy can also serve as a reference for further research on excellent multifunctional sensors.

Disorder and Sorption Preferences in a Highly Stable Fluoride-Containing Rare-Earth fcu-Type Metal-Organic Framework.

Rare-earth (RE) metal-organic frameworks (MOFs) synthesized in the presence of fluorine-donating modulators or linkers are an important new subset of functional MOFs. However, the exact nature of the REaXb core of the molecular building block (MBB) of the MOF, where X is a μ2or3-bridging group, remains unclear. Investigation of one of the archetypal members of this family with the stable fcu framework topology, Y-fum-fcu-MOF (1), using a combination of experimental techniques, including high-field (20 T) solid-state nuclear magnetic resonance spectroscopy, has determined two sources of framework disorder involving the μ3-X face-capping group of the MBB and the fumarate (fum) linker. The core of the MBB of 1 is shown to contain a mixture of μ3-F- and (OH)- groups with preferential occupation at the crystallographically different face-capping sites that result in different internally lined framework tetrahedral cages. The fum linker is also found to display a disordered arrangement involving bridging- or chelating-bridging bis-bidentate modes over the fum linker positions without influencing the MBB orientation. This linker disorder will, upon activation, result in the creation of Y3+ ions with potentially one or two additional uncoordinated sites possessing differing degrees of Lewis acidity. Crystallographically determined host-guest relationships for simple sorbates demonstrate the favored sorption sites for N2, CO2, and CS2 molecules that reflect the chemical nature of both the framework and the sorbate species with the structural partitioning of the μ3-groups apparent in determining the favored sorption site of CS2. The two types of disorder found within 1 demonstrate the complexity of fluoride-containing RE-MOFs and highlight the possibility to tune this and other frameworks to contain different proportions and segregations of μ3-face-capping groups and degrees of linker disorder for specifically tailored applications.

Dual-emission lanthanide metal-organic framework as a luminescence sensor for nitrofuran antibiotics and pesticide detection

In recent years, there has been an increasing concern for health and food safety due to the severe environmental pollution caused by the overuse of antibiotics and pesticides. Effective and accurate detection of these species is of great importance in many fields. In this paper, a two-dimensional lanthanide organic framework [Tb(dobpdc)1.5(DEA)2]n (1) was synthesized using 4,4′-dihydroxy-3,3′-biphenyl dicarboxylic acid ligand (H2L) with Tb(III) ion in the atmosphere of N,N'-diethylacetamide (DEA) and deionized water as solvents by solvothermal method. Compound 1 displays a single excitation double emission in aqueous suspensions. The luminescence properties of 1 were exploited as a multi-responsive luminescence sensor for nitrofuran antibiotics (nitrofurazone, nitrofurantoin) and triazine pesticides (metamitron) with a low detection limit and high selectivity via dual emission “turn-off” luminescence quenching. 1 has also been successfully applied to the construction of portable test strips for the detection of antibiotics and pesticides. In addition, the mechanism of fluorescence quenching has also been further discussed.

Ln-MOF-Based Hydrogel Films with Tunable Luminescence and Afterglow Behavior for Visual Detection of Ofloxacin and Anti-Counterfeiting Applications.

Highly selective and sensitive quantitative detection of ofloxacin (OFX) at ultralow concentrations in aqueous media and development of new afterglow materials remains a challenge. Herein, a new 2D water-stable lanthanide metal-organic framework (NIIC-2-Tb) is proposed, which exhibits high selectivity towards OFX through the luminescence quenching with the lowest detection limit (1.1× 10-9 M) reported to date and a fast response within 6 s. In addition, the luminescent detection of OFX by NIIC-2-Tb is not affected by typical components of blood plasma and urine. The excellent sensing effect of NIIC-2-Tb is further utilized to prepare a composite functional sensing carrageenan hydrogel material for the rapid detection of OFX in meat in real time and the first discovery of impressive afterglow in MOF-based hydrogels. This study not only presents novel Ln-MOF materials and Ln-MOF-based hydrogel films for luminescent sensing of OFX, but also demonstrates color-tunable luminescent films with afterglow, which expands the application of composite luminescent materials for detection and anti-counterfeiting.

Effect of different lanthanide ions on the catalytic activation of peroxymonosulfate with lanthanide metal-organic frameworks (Ln-MOFs) with terephthalic acid

Ln-MOFs with four different Ln-ions (La, Ce, Gd, Tb) and terephthalic acid (H2BDC) were synthesised by solvothermal method. The crystals structure was confirmed by powder XRD and infrared spectroscopy (IR) corresponding to [Ln2(BDC)2(H2O)4]∞ and microstructural information of all samples was extracted by applying Rietveld refinement. By scanning electron microscopy (SEM) the morphology of the samples was revealed. First time applying Ln-MOFs for the catalytic activation of peroxymonosulfate (PMS) demonstrated their potential application as catalysts in a Fenton-like reaction for water purification from the antibiotic tetracycline hydrochloride (TCH). For the best performing Ce-MOF degradation of TCH reached 80% that’s why additional experiment for determination of activation energy and the mechanism of the catalytic reaction were performed. The stability of the catalyst was also confirmed by powder XRD after the reaction.

Energy transfer process, luminescence optimizing and various applications of lanthanide complexes

Modulating the spectroscopic overlap between the emission bands of donors and the absorption spectra of acceptors by various simulations, it is possible to systematically investigate the emission behaviors of lanthanide complexes under different conditions. To establish the relationships between emission behaviors and various external simulations, it is necessary to study the energy transfer rate and efficiency between the donor and acceptor under different conditions to clarify the luminescent mechanism of the complexes, providing a theoretical basis for high-performance smart materials. This review focuses on the recent progress of luminescence performance of lanthanide complexes, including energy transfer mechanisms, emission color modulation, the strategies for optimizing lanthanide luminescence, and finally, various applications based on luminescence performance of lanthanide complexes and lanthanide metal-organic frameworks.

Lanthanide metal organic frameworks as fluorescence sensors for temperature and antibiotics differentiation

Dual-emission ratiometric fluorescent sensors based on lanthanide metal-organic frameworks with excellent luminescent properties have become a class of emerging materials in luminescence. Herein, one three-dimensional lanthanide metal-organic framework [Eu2(NDC)3H2O] (CUST-619) (NDC: 1,4-naphthalenedicarboxylic acid) was successfully synthesized. Based on the excellent stability of CUST-619 in water environment, the fluorescent sensing and distinguishing for commonly used antibiotics in water is performed, in which tetracycline quenched the double fluorescence emission peaks of CUST-619, while tetracycline hydrochloride only causes the Eu emission peak in CUST-619 to quench. Subsequently, powder MOF crystals are physically mixed with the polymer polyvinylidene difluoride (PVDF) to prepare mixed matrix membranes (CUST-619@PVDF). CUST-619 and CUST-619@PVDF exhibits temperature sensing performance with consistent color changes under UV light and in CIE coordinates. This work provides a general approach to synthesize lanthanide metal-organic frameworks based materials for fluorescence sensing technology.

Highly sensitive sensing of DPA by lanthanide metal–organic frameworks and detection of fiber membranes

The detection of 2,6-pyridinecarboxylic acid (DPA), as a biomarker of Bacillus anthracis, has attracted wide attention. In previous reports of DPA detection, fluorescent probes may not have high specificity. Therefore, the rational design and development of fluorescent sensors with excellent performance is of great significance for the detection of DPA. In this study, two novel lanthanide metal–organic frameworks (Ln-MOFs) were synthesized by hydrothermal method using 3-polyfluorobiphenyl-3 ', 4,5 ' -tricarboxylic acid (H2FPTA) as ligand. Studies have shown that Ln-MOFs can detect DPA in real time, with detection limits of 0.54 μM and 0.67 μM, respectively, and have a high recovery rate (95 % −108 %) in fetal bovine serum. As a self-calibration sensor, other substances in the blood can be clearly distinguished by a two-dimensional fluorescence code diagram. After the Ln-MOFs were spun into nanofiber membranes, they responded quickly to DPA. This increases practicability and provides a promising idea for the development of simple and efficient ratio sensors.

Instrument-free and rapid Vibrio parahaemolyticus biosensing based on coupled dual-signal of paper-needle and LnMOF

At present, most reported studies on paper-based sensing devices for food-borne pathogens usually rely on a single signal as the basis for judging the results, accompanied with inaccurate detection results. In this study, we used the lanthanide MOFs being covalently modified with aptamers (Apt-LnMOFs) as the sensing and recognition element of Vibrio parahaemolyticus (VP), and the paper-based needle shape device (paper-needle) as the visual signal output carrier. Finally, an accurate detection strategy for VP was successfully constructed. In terms of signal output, the two signal styles of Apt-LnMOFs diffusion distance on the paper-needle and R value (measured by the RGB analysis software of smartphone) are coupled to jointly improve the accuracy of detection results. The method is simple and fast, and the detection accuracy in real samples is 91%. This strategy is very suitable for on-site rapid detection of pathogens, and does not require large professional instruments.

Improved performance of lanthanide-doped UIO-66/Nafion hybrid proton exchange membrane for water electrolyzer

Incorporating metal-organic frameworks (MOFs) especially the ones with protic functional groups into proton exchange membrane (PEM) can effectively improve its proton conductivity. Lanthanide MOFs (Ln-MOFs) have been recognized as more potential candidates exhibiting proton dissociation capability. However, the performance of PEM upon integrating Ln-MOFs in water electrolyzer has yet to be investigated. In this study, Nafion composites with different loadings of lanthanide Ce-UiO-66 were prepared, characterized and tested by comparing with the non-lanthanide Zr-UiO-66. It was revealed that the proton conductivity of Ce-UiO-66/Nafion composite membrane was higher than pristine Nafion and Zr-UiO-66/Nafion membrane, which was attributed to the fact that the Ce-UiO-66 doping contributed to the construction of the hydrogen-bonded network to enhance the proton conductivity. At 3 wt% Ce-UiO-66 doping, the proton conductivity of the composite membrane can reach 124.45 mS/cm, which is significantly improved by 17 % compared with Zr-UiO-66/Nafion. Such a trend is mainly contributed by the lower proton affinity and proton transfer capability of Ce atoms in Ce-UiO-66, and the higher number of water molecules around Ce atoms favors the reduced tortuosity of the proton conduction pathway in membranes. Single electrolytic cell tests demonstrated the enhancement of electrolysis efficiency upon Ce-UiO-66 doping was improved from 58.77 % to 65.37 % at a current density of 2 A cm−2.

Linker installation transformations in a 2-D rare earth MOF: increase of the dimensionality and turn on of the temperature sensing capability

A new 2-D 8-connected rare earth (RE) MOF based on a hexanuclear (RE3+)6 SBU, the increase of the dimensionality through SCSC linker installation reactions and the turn-on of the temperature sensing capability upon these reactions are reported.

Lanthanide MOF-based luminescent sensor arrays for the detection of castration-resistant prostate cancer curing drugs and biomarkers.

In recent years, castration-resistant prostate cancer (CRPC) has profoundly impacted the lives of many men, and early diagnosis of medication and illness is crucial. Therefore, a highly efficient detection method for CRPC biomarkers and curing drugs is required. However, the complex and diverse structures of CRPC drugs pose significant challenges for their detection and differentiation. Lanthanide metal-organic frameworks (Ln-MOFs) show great potential for sensing applications due to their intense and characteristic luminescence. In this work, a series of new bimetallic Ln-MOFs (EuxTb1-x-MOF) based luminescent sensor arrays have been developed to identify CRPC drugs, including in mixtures, via principal component analysis (PCA) and hierarchical cluster analysis (HCA) methods. These Ln-MOFs are built with a highly conjugated H2L linker (H2L = 5-(4-(triazole-1-yl)phenyl)isophthalic acid) and exhibit robust strong luminescence emissions (mainly located at 543 and 614 nm) and high energy transfer efficiencies. More specifically, Eu0.096Tb0.904-MOF (MOF 3) has demonstrated good sensing performances for CRPC curing drugs in real human serum samples. Furthermore, the curing drug hydroxyflutamide has been combined with MOF 3, to construct a robust composite sensing platform MOF 3@hydroxyflutamide for highly efficient detection of CRPC biomarkers such as the androgen receptor (AR) and prostate-specific antigen (PSA). Finally, luminescence lifetime measurements, zeta potential measurements, and density functional theory (DFT) calculations were performed to gain insights into the sensing mechanism.

Rare-earth UiO-66 for temperature sensing near room temperature

Rare-earth UiO-66 for temperature sensing near room temperature

Eu3+-MOF fluorescence sensor based on a dual-ligand strategy for visualised detection of an anthrax biomarker 2,6-pyridine dicarboxylic acid

A dual-ligand ratiometric fluorescence sensor based on lanthanide–metal–organic frameworks was successfully synthesised for the sensitive and convenient detection of DPA.

A lanthanide metal–organic framework containing a hydrazine group for highly sensitive luminescent sensing of formaldehyde gas

A hydrazine-functionalized LnMOF was developed for highly sensitive formaldehyde gas detection with a low detection limit of 41.7 ppb.

Visible light mediated photocatalysis by lanthanide metal-organic frameworks: enhanced specificity and mechanistic insights.

The utilization of earth-abundant photosensitizers with visible light absorption to enable sustainable photocatalysis is a long-standing challenge. Overcoming such a challenge, in this work, two lanthanide (Ln3+ = Tb, Eu) based metal-organic frameworks (Ln-MOFs) have been synthesized utilizing a Co3+-based metalloligand. Both Ln-MOFs function as remarkable photocatalysts for the selective oxidation of assorted alcohols and sulfides to their corresponding aldehydes/ketones and sulfoxides using visible light. The photophysical behavior of both Ln-MOFs and mechanism of photocatalysis is comprehensively investigated using time-resolved transient absorption spectroscopy, electrochemical impedance spectroscopy, electron paramagnetic resonance spectroscopy, photoluminescence and phosphorescence studies. In both Ln-MOFs, a metalloligand acts as a light-harvester, being excited by visible light, while Ln3+ ions endow the resulting MOFs with long-lived triplet excited states. Ultrafast transient absorption spectroscopy, further supported by electron paramagnetic resonance spectra, revealed excited-state electron transfer from metalloligands to the Ln3+ ions and transient generation of Ln2+ sites alongside the facilitation of intersystem crossing. The excited Ln2+ ions transfer energy to the ground-state triplet oxygen (3O2) to generate singlet oxygen (1O2). The HOMO-LUMO positions of both Ln-MOFs support the generation of ˙O2 - and 1O2 but inhibit strongly-oxidizing yet non-selective ˙OH radicals. Scavenger experiments, 1O2 traps and electron paramagnetic resonance spectra confirmed the generation of singlet oxygen. The heavy-metal effect of a lanthanide ion in Ln-MOFs for the generation of triplet excitons is confirmed by the synthesis of a non-heavy-metal analogue involving a zinc ion via a single-crystal-to-single-crystal transformation strategy. The present results are noteworthy and may aid in the development of other earth-abundant metalloligand-based photocatalysts for challenging yet sustainable catalysis.

A novel 2D Eu-MOF as a dual-functional fluorescence sensor for detection of benzaldehyde and Fe3.

Lanthanide metal-organic frameworks (Ln-MOFs) have unique advantages in sensing due to their excellent optical properties. In this study, we synthesized a dicarboxylic acid ligand with amide groups and successfully synthesized a novel two-dimensional (2D) MOF with the molecular formula C42H31EuN4O10 (Eu-MOF) by a solvothermal method. Single-crystal X-ray diffraction showed that amide groups are exposed on the outside of the two-dimensional coordination layer, with the possibility of recognizing specific molecules through hydrogen bonding interactions. The ligand's "antenna effect" enables Eu-MOF to emit a strong luminescence characterized by the "f-f" transition. Further studies have revealed that Eu-MOF could be used as a bifunctional fluorescent probe for the selective detection of benzaldehyde and Fe3+. The sensing mechanism has been analyzed in detail through powder X-ray diffraction (PXRD) analysis, UV-vis spectroscopy, fluorescence lifetime measurement, and density functional (DFT) theory calculation. This design and research can provide a reference for subsequent related work.

Dimensional regulation of lanthanide metal-organic frameworks and their application in bacterial detection.

Low-dimensional (LD) lanthanide metal-organic frameworks (Ln-MOFs) have attracted considerable attention in different fields due to their exceptional optical properties and numerous accessible active sites. Through the dimensional regulation effect of dipicolinic acid (DPA), a new LD Ln-MOF crystal is synthesized to monitor nitroreductase (NTR) activity in living bacteria.