Lanthanide Metal-organic Frameworks Research Articles

A post-modified lanthanide metal-organic frameworks as ratiometric luminescent sensor for the visual detection of 5-hydroxytryptamine

5-Hydroxytryptamine (5-HT), a key neurotransmitter, is an important biomarker for carcinoid syndrome. We herein construct a ratiometric luminescent sensor by covalently coupling fluorescein 5-isothiocyanate (FITC) with lanthanide metal-organic frameworks (Ln-MOFs). In the presence of 5-HT, the emission of FITC increases while the emission of Eu3+ decreases, accompanied by a distinct color change of emission from orange to green. This sensor not only has the advantages of high sensitivity (LOD = 0.04μM), fast response (30s), excellent selectivity, and large ΔE⁎ab value (73), but can also be used for the detection of 5-HT in human serum and allow for instant visual detection with the assistant of smartphone. This ratiometric luminescent sensor offers an alternative avenue for early diagnosis of carcinoid syndrome.

A Luminescent Lanthanide MOF for the Selective and Ultra‐High Sensitivity Detection of Caffeic Acid

ABSTRACTA novel metal–organic framework (MOF) [Eu3L4(CH3COO) (H2O)7]·(CH3CN)5 (1) based on the ligand H2L (3′,5′‐di(1H‐1,2,4‐triazole‐1‐yl)‐[1,1′‐biphenyl]‐3,5‐dicarboxylic acid) has been synthesized by the hydrothermal method. A complete characterization of 1 was conducted, employing a range of techniques including crystallography, PXRD, SEM, FTIR spectroscopy, and TGA analysis. The fluorescence sensing behavior of 1 was examined in a solution of N,N‐dimethylformamide (DMF). The results demonstrated that 1 exhibited a pronounced “turn‐off” fluorescence phenomenon in the presence of caffeic acid (CA). Despite the interference of 11 potential substances, 1 was still capable of effectively recognizing CA. The luminescence intensity ratio of 1 showed a strong linear relationship with CA concentration in the range 0–5 μM. The Ksv value was 2.49 × 105 M−1. Additionally, the detection mechanism was studied using PXRD, SEM, UV–Vis, and fluorescence lifetime methods.

Pressure-Promoted Ligand to Metal Energy Transfer for Emission Enhancement of [Tb2(BDC)3(DMF)2(H2O)2]n Metal-Organic Framework

Abstract Lanthanide metal-organic frameworks (Ln-MOFs) have received extensive attention in the development of photoluminescent (PL) materials due to their stable structures and unique line-like emission spectroscopic properties. However, in order to prepare Ln-MOFs with high PL quantum yield (PLQY), further improving the sensitization efficiency of the “antenna effect” is essential. Herein, remarkably enhanced PL in [Tb2(BDC)3(DMF)2(H2O)2]n MOF is successfully achieved via high-pressure engineering at room temperature. Notably, the PL intensity continues to increase with the pressure increases, reaching its peak at 12.0 GPa, which is 4.4 times compared to the initial state. Detailed experimental and theoretical calculations have demonstrated that pressure engineering significantly narrows the bandgap of [Tb2(BDC)3(DMF)2(H2O)2]n, optimizing both singlet and triplet energy levels. Ultimately, higher “antenna effect” sensitization efficiency is achieved by promoting intersystem crossing and energy transfer processes. Our work provides a promising strategy for the development of high PLQY Ln-MOFs.

Polarity Sensor Based on Multivariate Lanthanide Metal-Organic Framework for Constructing Biosensing Platform.

It is significant but challenging to develop polarity sensors that can measure multiscenario polarity in a modular, customized, sensitive, and accurate manner. In this work, we proposed a polarity sensor based on multivariate lanthanide metal-organic framework (Ln-MOF) nanoclusters through the modular programming design of ligands. This multivariate Ln-MOF combines the advantages of modularity, ease of design, high flexibility and low cost, and can be precisely customized for different polarity systems. The MOF Eu0.1Tb0.9-isophthalic acid (IPA) and Eu0.3Tb0.7-o-phthalic acid (OPA) are suitable for the detection of trace water in dimethylsulfoxide (DMSO) and hyaluronidase activity, respectively. Especially, Eu0.3Tb0.7-OPA can achieve high-sensitivity detection of hyaluronidase activity within 8 min, with the limit of detection as low as 0.016 U/L. The results enable us to break through our previous understanding of polarity parameter, allowing us to develop more polarity-related biosensing platforms. Ln-MOFs are believed to utilize their adjustable polar intermolecular interactions to achieve the optimal compatibility and high sensitivity in polarity sensing systems, which is supported by experiments and density functional theory calculations. These polarity sensors based on multivariate Ln-MOF nanoclusters offer significant potential in biosensing and medical diagnostics, overcoming traditional biosensor limitations in synthesis and customization.

A NbO-type mixed lanthanide metal-organic framework for cryogenic temperature sensing.

A novel NbO-type Eu/Tb-mixed lanthanide metal-organic framework has been developed for the highly sensitive, self-calibrating detection of cryogenic temperature.

The Shastry–Sutherland lattice in two-dimensional magnetic lanthanide metal–organic frameworks

A detailed study on the relaxation dynamics of the SS lattice, using a targeted orthogonal-dimer dissolution–crystallization strategy, has shown this method to be highly effective for developing novel 2D lanthanide compounds for magnetic studies.

Accessing mixed cluster rare-earth MOFs with reduced connectivity via linker expansion and desymmetrization: co-assembly of 6-c and 10-c hexanuclear clusters in RE-stc-MOF-1

A desymmetrized 4-c linker directs the co-assembly of 6-c hexagonal and 10-c square bipyramidal rare-earth clusters, resulting in a unique six-nodal (3,3,3,3,6,10)-c net.

Conformation Regulation of Perylene Diimide Derivatives by Lanthanide Coordination for Turn-On Fluorescence Sensing of Sarin Simulants.

Fluorescent metal-organic frameworks (MOFs) are promising sensing materials that have received much attention in recent years, in which the organic ligand conformation changes usually lead to variations of their sensing behavior. Based on this, in the present work, perylene diimide (PDI) derivatives with excellent photochemical properties closely related to their conformation and molecule packing fashion were selected as organic linkers to detect sarin simulant diethyl chlorophosphate (DCP). By the coordination interactions with large lanthanide cations through terminal carboxylate groups from the PDI derivative, a series of one-dimensional coordination polymers, named [Ln(PDICl4-2COO)(μ2-O)0.5(DMF)1.5] (SNNU-112, Ln = Yb/Tb/Sm/Nd/Pr/Gd/Eu/Er/Ce, PDICl4-2COOH = N,N'-bis(4-benzoic acid)-1,2,6,7-tetrachlorohydrazone-3,4,9,10-tetracarboxylic acid diimide) were synthesized. Regulated by the coordination process, the ligand undergoes a certain degree of conformational turnover and thus leads to an electron distribution change compared to free PDICl4-2COOH. Notably, the contact with the DCP molecule triggered a further ligand conformational conversion of PDI ligands in SNNU-112 and thus caused a fluorescence turn-on phenomenon realizing a well-defined fluorescence detection performance for DCP on the basis of a photoinduced electron transfer process. Among nine lanthanide MOFs, Yb-MOF sensor exhibited the lowest detection limit (4.36 ppb), fast response, high selectivity, and good recyclability. Such molecular conformation regulation of PDI derivatives by metal coordination may provide a new way for the exploration of fluorescent sensors.

An Acid-Resistant Lanthanide Metal-Organic Framework Based on Tetraphenylethylene as an Electrochemical Nitrite Sensor.

Nitrite (NO2-) is attracting increasing attention due to its harmful effect on human health. Thus, it is highly desirable to construct effective electrochemical sensors to detect the presence of NO2-. The majority of electrochemical NO2- detection is focused on alkaline or neutral electrolyte solutions and is rarely reported under acidic conditions. In this work, a tetraphenylethylene (TPE)-based 2D lanthanide metal-organic framework (Ln-MOF), (Me2NH2)[HoIII(tcbpe-F)DMF]•DMF•H2O (1) (tcbpe-F = 4',4‴,4″‴,4″″‴-(ethene-1,1,2,2-tetrayl)tetrakis(3-fluoro-[1,1'-biphenyl]-4-carboxylic acid, DMF = N,N-dimethylformamide)), has been successfully fabricated on carbon paper (CP) by an in situ hydrothermal method. As a NO2- sensor, the fabricated 1 electrode exhibited excellent electrochemical performance in the H2SO4 electrolyte (pH = 1) and offers high sensitivities of 1453.2 and 591.5 μA mM-1 cm-2, with a wide linear detection range of 0.1 μM to 9 M, a low detection limit of 60 nM, excellent specificity even in the presence of various analytes (metal ions, anions, and organic molecules) and real water samples, satisfactory stability, and reproducibility. This is the first report of TPE-based Ln-MOF as a NO2- sensor, and furthermore, a plausible sensing mechanism is confirmed by experiments and theoretical computations.

An Ultrasensitive Self‐Calibrating Terbium Metal Organic Framework for the Detection of Amphotericin B

ABSTRACTWe successfully synthesized a 3D porous lanthanide metal–organic framework, [Tb (obdb)][Tb1/3(H2O)7/3]·NMP (Tb‐MOF) with hydrated terbium ions in the pores by solvothermal method using 4′,4″′‐oxybis[1,1′‐biphenyl]‐3,5‐dicarboxylic acid (H4obdb) as ligand. It is worth mentioning that Tb‐MOF exhibits excellent performance in structural stability and fluorescence response. Even after soaking in various solvents and pH solutions for 3 months, Tb‐MOF can maintain its structural integrity and excellent stability. The fluorescence spectra show that Tb‐MOF not only exhibits the luminescence of the ligand centered at 368 nm (IL), but also emits the characteristic emissions of the metal terbium, among which the luminescence at 542 nm is the strongest. In the detection of antibiotic amphotericin B (AB), Tb‐MOF showed significant detection efficiency. Upon increasing the concentration of AB, the fluorescence intensity at 542 nm gradually decreased, whereas the fluorescence at 368 nm decreased rapidly. The I542/IL value showed a very high linear correlation with AB concentration, with the slope reaching 1.29 × 108 M−1 (0–100 μM). In the field of fluorescent sensors for AB detection, Tb‐MOF is notable not only for its impressively low LOD (limt of detection) of 0.072 nM but also for pioneering the application of a self‐calibrating ratio‐based detection method. To better elucidate this fluorescence sensing phenomenon, we also conducted a detailed discussion of the sensing mechanism for AB.

Dynamic Magnetic Control of Lanthanide Metal–Organic Framework Crystals and Their Polarized Emissions

Traditional barcode encoding methods are constrained by the inability to dynamically control crystal orientations, thereby limiting their applications. In this work, we investigate the dynamic magnetic control of lanthanide metal–organic framework crystals and their potential for advancing photonic barcode technology. A paramagnetic fluorescent Eu-MOF microcrystal with sizes ranging from 30 to 40 μm in length and 5 to 10 μm in width was synthesized, and its magnetic orientation and polarized emission were systematically investigated. Eu-MOF crystallizes in an orthorhombic space group, growing along the crystallographic b-axis and ultimately forming an anisotropic cuboid shape. Eu-MOF microcrystals exhibit significant magnetic anisotropy, causing the crystallographic c-axis of the crystal to align with the magnetic field when a uniaxial magnetic field of ~10 mT is applied. Furthermore, the Eu-MOF microcrystal exhibited characteristic Eu emissions with peaks at 594 nm, 616 nm, and 695 nm, and showed a high degree of polarization (DOP), reaching 0.904 at 616 nm. Therefore, the utilization of a rotating magnetic field not only enables precise and dynamic control over the crystal orientations but also results in a significant variation in the luminescence intensity. This capability enabled us to propose an innovative encryption barcode scheme in which the emission intensities of different luminescence peaks are converted into barcode widths, with the sequence of magnetic field directions serving as the encryption key. This approach presents a novel method for data storage and anti-counterfeiting, significantly enhancing the versatility and capacity of photonic barcodes.

Revealing Disorder, Sorption Locations and a Sorption-Induced Single Crystal-Single Crystal Transformation in a Rare-Earth fcu-Type Metal-Organic Framework.

Rare-earth metal-organic frameworks (RE-MOFs) formed in the presence of fluoride donors are a group of complex and applicable MOFs. Determining structural complexity is crucial in applying such MOFs and has been achieved to uncover framework disorders in the important fcu framework topology MOF, Y-ndc-fcu-MOF (1). 1 is found to contain F- groups disordered over the μ3-face-capping sites in its secondary building unit (SBU) and framework distortions upon sorption of different guest molecules. The favored location of the guests is within the octahedral cage of 1 where they interact with the Y3+ centers. The size, shape, and interactions of the different guests lead to subtle distortions within the SBU and adoption of specific orientations of the naphthalene group of the 1,4-naphthalenedicarboxylate framework linkers. The sorption of DMF(l)/H2O(l) lowers the symmetry from cubic Fm3̅m (for MeOH(l), N2(g), CO2(gorl)) to cubic Pa3̅ (for DMF(l)/H2O(l)) symmetry with retention of the fcu topology, and conversion between the Pa3̅ and Fm3̅m structures is induced by solvent exchange. Such disorder and sorption locations and transformation are important considerations during the optimization and application of MOFs for sorption-based technologies.

Co/Er2O3/C ternary nanocomposites derived from cobalt/erbium Prussian blue analogs for efficient microwave absorption

This study presents the synthesis of Er[Co(CN)6], a Prussian blue analog (ErCo-PBA) with varied morphology, fabricated by modulating the solvent ratio between C2H6O and H2O. This approach leverages the solubility characteristics of K3[Co(CN)6] and the consequential influence of C2H6O on the crystal growth. When the solvent ratios are 1:8, 8:1, and 1:1, the resulting ErCo-PBA precursors nanorods, irregular particles, and spindle-shaped particles, respectively. After annealing, these precursors in an Ar environment allowed the Co/Er2O3/C derivatives to retain the morphology of the precursor well. Electromagnetic parameters testing revealed that Co/Er2O3/C-1 exhibits superior electromagnetic wave-absorbing (EMWA) performance among the synthesized derivatives with an effective absorption bandwidth of 5.1 GHz at 1.85 mm and a minimum reflection loss of −56.7 dB at 2.9 mm. The incorporation of Er2O3 is an effective method for adjusting and optimizing the electromagnetic parameters of materials, thereby enhancing the EMWA performance of Co/Er2O3/C composite. This study highlights the potential of rare-earth oxide/Co/C composites, synthesized through direct annealing rare-earth metal–organic frameworks, as an absorber and are promising candidate to achieve high-efficiency electromagnetic wave absorption.

Multilevel Stimuli-Responsive Smart "Sandwich" Label with Physical Unclonable Functions Bionic Wrinkles and Space-Selective Fluorescence Patterns.

With the increasing popularity of the internet, it brings convenience to lives while also increases security risks. Physical Unclonable Functions (PUFs) can generate random, unclonable, and unique identifiers using their inherent physical characteristics, which have broad prospects in anti-counterfeiting. Herein, inspired by the irregular tree bark fissures and random skin wrinkles found in nature, a method for creating complex micro-wrinkles with unclonable random patterns is proposed by simply stretching hydrogels. The random texture information contained in the micro-wrinkles is digitized into binary codes using an adaptive threshold algorithm. Additionally, a novel "sandwich" label with a multilevel intelligent anti-counterfeiting system is proposed. The first-level involves photoluminescence encryption with adjustable luminescence within visible light range and modulated luminescence at different excitation wavelengths; the second-level includes strain-related mechanical encryption, and the third-level consists of highly random and unclonable micro-wrinkles. The certification difficulty increases as the anti-counterfeiting grade increases, thereby enhancing label security. Furthermore, space-selective doping of rare earth metal-organic framework (RE-MOF) fluorescent materials in hydrogels is achieved through the use of screen-printing technology. The concept of novel multilevel smart anti-counterfeiting PUF labels will further enhance current levels of counterfeiting prevention.

Luminescence Changeable CO2-Storage Cylinder: Triple-Stranded Helical Eu(III)/Tb(III) Fluorinated MOFs with Amide Linkers.

Triple-stranded helical lanthanide MOFs with CO2 adsorption properties were investigated. Lanthanide MOFs ([Eu0.1Tb0.9(hfa)3(dpa)]n) are composed of lanthanide luminophores (Eu(III) and/or Tb(III) ions), fluorinated antenna ligands (hfa: hexafluoroacetylacetonate), and polyamide-type linker ligands (dpa: 4-(diphenylphosphoryl)-N-(4-(diphenylphosphoryl)phenyl)benzamide). The cylindrical structure was characterized by single-crystal X-ray analysis, thermogravimetric analysis, and gas adsorption measurements. The inner surfaces of the cylindrical channels were covered with the fluorine atoms of the hfa ligands. The emission intensity ratio (IEu/ITb) in [Eu0.1Tb0.9(hfa)3(dpa)]n is affected by the CO2 gas adsorption behavior. The change in IEu/ITb value was caused by the intermolecular interactions between the CO2 gas molecules and the fluorinated ligands, resulting in an electronic structural change of the lowest triplet excited state in the photosensitized hfa ligands.

Regulating Ratiometric Fluorescence of Nanoporous Dual-Centered Lanthanide Metal–Organic Frameworks for Quantitative and Visual Detection of Anthrax Biomarkers

Regulating Ratiometric Fluorescence of Nanoporous Dual-Centered Lanthanide Metal–Organic Frameworks for Quantitative and Visual Detection of Anthrax Biomarkers

Epitaxial Growth of Multicolor Lanthanide MOFs by Ultrasound for Photonic Barcodes.

Epitaxially grown lanthanide metal-organic frameworks (Ln MOFs) exhibit multicolor and characteristic Ln emission with sharp emission bands, which are of great value in the field of information security and anti-counterfeiting. Epitaxial growth of Ln MOFs is generally achieved by solvothermal or hydrothermal methods, which suffer from challenges such as high reaction temperature and long growth time. Here, we report the fast epitaxial growth of multicolor lanthanide MOFs by an ultrasonic method at room temperature. The TbSmSQ shows a core-shell type structure with the Tb ion in the core and Sm in the shell within one crystal and exhibits the characteristic emission lines of Tb and Sm, respectively. The nonporous structure and large distance between lanthanide ions effectively avoid the influence of solvent vapor on the intensity and color of luminescence emission. Its application as photonic barcodes has been studied. This work demonstrates the feasibility of epitaxial growth of multicolor Ln MOFs by the ultrasonic method and its value for anti-counterfeiting and information security applications.

A smartphone-integrated bimetallic ratiometric fluorescent probe for specific visual detection of tetracycline antibiotics in food samples and latent fingerprinting

Designing and preparing highly sensitive and accurate fluorescent chemosensors for monitoring tetracycline antibiotics remains a challenge. Herein, a fluorescent chemosensor based on lanthanide metal-organic frameworks (Ln-MOFs) is proposed to realize high-precision monitoring by adjusting the ratio of lanthanide ions. Ln-MOFs with good aqueous stability were prepared by a solvothermal method using Eu3+, Tb3+ and the ligand 4,4′,4″-s-triazine-2,4,6-triyltribenzoic acid (H3TATB) in DMF/NMP/H2O. The Ln-MOFs could recognize oxytetracycline (OTC) and doxycycline (DOX), and the detection limits of OTC and DOX were as low as 8.6 and 4.8 nM, respectively. In particular, Eu(1.4 μM)-Tb-MOF sensors were used for visual detection of OTC and DOX in combination with smartphones with detection lines as low as 9.8 nM and 14.2 nM, respectively. Meanwhile, Eu-MOF, Tb-MOF and Eu(1.4 μM)-Tb-MOF can be used for latent fingerprint (LFP) visualization, demonstrating their potential applications in the field of criminal case investigation. The developed probes were successfully applied to determining OTC and DOX in milk, beef and pork with recoveries ranging from 92.0 % to 109.63 % and relative standard deviations (RSDs) ranging from 1.83 % to 4.56 %. Eu(1.4 μM)-Tb-MOF is believed to utilize its lanthanide metal ion coordination and photoinduced electron transfer (PET) mechanism to achieve highly selective and accurate OTC and DOX detection, which is supported by experimental and density functional theory (DFT) calculations.

High sensitivity distinguishing detection of fluoroquinolones with a cage-based lanthanide metal-organic framework in food

Sensitive and selective detection of fluoroquinolones, especially from different sources, is challenging. This study reported an uncommon three-cage lanthanide metal-organic framework (1-Eu) with a Eu3+ cluster as its structural primitive using a C2-symmetric 5,5-(Pyrazine-2,6-diyl) diisophthalic acid ligand. The 1-Eu probe effectively detected four fluoroquinolones through distinct color changes and spectral emission bands, demonstrating excellent performance with low detection limits: moxifloxacin (LOD: 9.3 nM), danofloxacin (LOD: 33.7 nM), gatifloxacin (LOD: 67.9 nM), and ofloxacin (LOD: 238.6 nM). Mechanistic studies revealed that internal filtration and photoinduced electron transfer (a-PET) effects were key factors. Furthermore, 1-Eu was successfully used to detect fluoroquinolones in food samples. Additionally, portable paper-based sensors were developed to quickly semi-quantify analyte concentrations using a smartphone color recognition app, underscoring the practical potential of this probe. This study introduces a novel methodology for the identification and detection of fluoroquinolones to enhance food safety.

An ultrasensitive and visual ratio fluorescence sensing platform for tannic acid in water based on boric acid functionalized lanthanide MOF

Tannic acid (TA) is a natural polyphenol that is widely used as a preservative and antioxidant in foods, beverages, health products and pharmaceuticals. In this study, a novel Eu-MOF skeleton was prepared using a simple solvothermal strategy and used as a ratio-metric fluorescence sensor for the ultra-sensitive detection of TA. The constructed Eu-MOF has excellent fluorescence properties and high stability in the aqueous phase. With the introduction of TA, a special covalent structure is formed between the o-diphenol group of TA and the boric acid hydroxyl group in ligand of the MOF, resulting in a gradual decrease in the red emission of Eu-MOF at 614 nm and a basically invariable blue emission at 420 nm. As the concentration of TA increased, the color of the system also changes from red to blue, thus achieving rapid and sensitive detection with a low limit of detection (LOD) of 75.6 nM through a ratiometric fluorescence strategy. What is more, Eu-MOF fluorescent probe combined with smart phone color detector is used to visually detect TA. The propose method is successfully applied in the target analysis in tea and beverage samples and the recovery is 95.6∼110.0 %, which is proved to be an effective strategy for the food safety and healthy monitoring.