Lanthanide Metal-organic Frameworks Research Articles

A fluorescent terbium-metal-organic framework material for high-sensitivity detection of vomitoxin and oxytetracycline hydrochloride in water.

A unique luminescent lanthanide metal-organic framework (LnMOF)-based fluorescence detection platform was utilized to achieve sensitive detection of vomitoxin (VT) and oxytetracycline hydrochloride (OTC-HCL) without the use of antibodies or biomolecular modifications. The sensor had a fluorescence quenching constant of 9.74 × 106 M-1 and a low detection limit of 0.68 nM for vomitoxin. Notably, this is the first example of a Tb-MOF sensor for fluorescence detection of vomitoxin. We further investigated its response to two mycotoxins, aflatoxin B1 and ochratoxin A, and found that their Stern-Volmer fluorescence quenching constants were lower than those of VT. In addition, the fluorescence sensor realized sensitive detection of OTC-HCL with a detection limit of 0.039 μM. In conclusion, the method has great potential as a sensitive and simple technique to detect VT and OTC-HCL in water.

Two-Dimensional Lanthanide Metal-Organic Framework Heterostructures for Noninvasively Photoresponsive High-Security Photonic Barcodes.

Stimuli-responsive micro/nanoscale photonic barcodes show great capacity for encryption and anticounterfeiting technologies due to multiple authentications, yet their application is commonly restricted by invasive stimuli. Herein, we report noninvasive light-stimulated high-security photonic barcodes based on spatially assembled photoresponsive two-dimensional (2D) 1,3,5-benzenetribenzoate (BTB)@Ln-MOF host-guest heterostructures. The photoluminescence (PL) spectra information on BTB@Ln-MOF heterostructures could be precisely controlled by the different wavelengths of ultraviolet (UV) light trigger. By using the PL properties and 2D heterostructures as cryptographic primitives, spatially resolved smart photonic barcodes based on both spectral and graphical coding are realized in BTB@Ln-MOF host-guest materials. These results will pave an avenue for the development of smart stimuli-responsive photonic barcodes for anticounterfeiting applications.

Lanthanide metal-organic framework-based surface molecularly imprinted polymers ratiometric fluorescence probe for visual detection of perfluorooctanoic acid with a smartphone-assisted portable device

Perfluorooctanoic acid (PFOA) poses a threat to the environment and human health due to its persistence, bioaccumulation, and reproductive toxicity. Herein, a lanthanide metal-organic framework (Ln-MOF)-based surface molecularly imprinted polymers (SMIPs) ratiometric fluorescence probe (Eu/Tb-MOF@MIPs) and a smartphone-assisted portable device were developed for the detection of PFOA with high selectivity in real water samples. The integration of Eu/Tb MOFs as carriers not only had highly stable multiple emission signals but also prevented deformation of the imprinting cavity of MIPs. Meanwhile, the MIPs layer preserved the fluorescence of Ln-MOF and provided selective cavities for improved specificity. Molecular dynamics (MD) was employed to simulate the polymerization process of MIPs, revealing that the formation of multiple recognition sites was attributed to the establishment of hydrogen bonds between functional monomers and templates. The probe showed a good linear relationship with PFOA concentration in the range of 0.02–2.8 μM, by giving the limit of detection (LOD) of 0.98 nM. Additionally, The red-green-blue (RGB) values analysis based on the smartphone-assisted portable device demonstrated a linear relationship of 0.1–2.8 μM PFOA with the LOD of 3.26 nM. The developed probe and portable device sensing platform exhibit substantial potential for on-site detecting PFOA in practical applications and provide a reliable strategy for the intelligent identification of important targets in water environmental samples.

Reticular Rare-Earth Metal–Organic Frameworks with High Stability and Defective Sites: Post-Functionalization for Hydrogen Peroxide Detection

Reticular Rare-Earth Metal–Organic Frameworks with High Stability and Defective Sites: Post-Functionalization for Hydrogen Peroxide Detection

Rare-Earth Metal-Organic Framework with Nonplanar Porphyrin Groups for High-Efficiency Photocatalysis.

Nonplanar porphyrins play crucial roles in many biological processes and chemical reactions as catalysts. However, the preparation of artificial nonplanar porphyrins suffers from complicated organic syntheses. Herein, we present a new rare-earth porphyrinic metal-organic framework (RE-PMOF), BUT-233, which is a three-dimensional (3D) framework structure with the flu topology consisting of 4-connected BBCPPP-Ph ligands H4BBCPPP-Ph = 5',5⁗-(10,20-diphenylporphyrin-5,15-diyl)bis([1,1':3',1″-terphenyl]-4,4'' dicarboxylic acid) and 8-connected Eu6 clusters. Noteworthily, the porphyrin cores of the BBCPPP-Ph ligands in BUT-233 are nonplanar with a ruffle-like conformation. In contrast, the porphyrin core in the free ligand H4BBCPPP-Ph is in a nearly ideally planar conformation, as confirmed by its single-crystal structure. BUT-233 is microporous with 6-8 Å pores and a Brunauer-Emmett-Teller (BET) surface area of 649 m2/g, as well as high stability in common solvents. The MOF was used as a photocatalyst for the oxidation degradation of a chemical warfare agent model molecule CEES (CEES = 2-chloroethyl ethyl sulfide) under the light-emitting diode (LED) irradiation and an O2 atmosphere at room temperature. CEES was almost completely converted into its nontoxic light-oxidized product CEESO (CEESO = 2-chloroethyl ethyl sulfoxide) in only 5 min with t1/2 = 2 min (t1/2: half-life). Moreover, the toxic deep-oxidized product 2-chloroethyl ethyl sulfone (CEESO2) was not detected. The catalytic activity of BUT-233 was high in comparison with those of some previously reported MOF catalysts. The results of photo/electrochemical property studies suggested that the high catalytic activity of BUT-233 was benefited from the presence of nonplanar porphyrin rings on its pore surface.

Fast fluorescence sensing of aflatoxin B1 employing a europium metal–organic framework avoiding self-fluorescence interference of target

Aflatoxin B1 (AFB1) easily contaminates grain, oil, and their products, and is strongly carcinogenic. Therefore, rapid, efficient and sensitive detection of aflatoxin plays a key role in the food industry. Here, we prepared a lanthanide metal-organic framework termed Eu-TCPP, in which the ligand can effectively sensitize Eu3+ with excellent photoluminescence properties. It is worth mentioning that the fluorescence intensity of Eu-TCPP is at 617 nm, which can avoid the interferences of AFB1 self-fluorescence emitting in the range of 400 nm–500 nm. Eu-TCPP can efficiently detect AFB1 without using antibody or biomolecular modifications, exhibiting a rapid response of 60 seconds and a limit of detection (LOD) at 11.63 ppb. The Eu-TCPP sensor also has satisfactory performance for determining AFB1 sensitively in real oil samples. In addition, the mechanism of the excellent detection performance of Eu-TCPP has been investigated using density-functional theory (DFT) calculations combined with experimental analysis. The results show that the LUMO energy level of the ligand is higher than that of the aflatoxin, which causes the electrons transfer toward the targets, and results in the reduction of the fluorescence intensity. Therefore, our proposed Eu-MOF materials based on the "antenna effect" have great potential for the development of simple, fast, and sensitive small-molecule sensors, and offer a promising prospect in POCT applications.

Construction of a novel Eu-MOF material based on different detection mechanisms and its application in sensing pollutants aniline, F- and Hg2+

Aniline is an organic pollutant with carcinogenicity and teratogenicity, while F- and Hg2+ are toxic ions that are easily soluble in water. When they are released to the environment, they will pose a threat to human health. Designing a material that can simultaneously detect three types of pollutants is of great significance. In this paper, a novel rare earth metal organic framework material (Eu-MOF) with three-dimensional structure based on 1-methylimidazole-4,5-dicarboxylic acid was synthesized for the first time through solvent thermal method. It has excellent luminescent performance and can be used as a multifunctional fluorescent probe to detect aniline, F-, and Hg2+ based on photoinduced electron transfer, energy competitive absorption, and ion exchange mechanisms, with detection limits of 1.79 × 10-8, 8.13 × 10-8, and 8.83 × 10-7 M, respectively. It is worth noting that Eu-MOF can detect F- and Hg2+ in real water samples, such as lake water and green tea water, with favorable recovery rates.

Dual-functional fluorescence sensors based on 3D lanthanide metal–organic framework and its mixed matrix membrane

A new lanthanide metal–organic framework (Ln-MOF) {[Eu(DPB)(H2O)](Me2NH2+)}n (1) (H4DPB = (1,1′:3′,1′’-terphenyl)-3,3′’,5,5′’-tetracarboxylic acid）was synthesized under solvothermal conditions and presented a fascinating three-dimensional (3D) framework with 4,8-connected diamond topology, which were built from Eu3+ ions and tetra carboxylate groups. 1 showed strong red luminescence emission in the solid state at room temperature and exhibited good stability in different solvents. 1 could be used as a multi-responsive luminescent sensor for hemin and p-Nitrophenol (4-NP) with detection limits of 3.91 × 10−6 M and 1.98 × 10−4 mM, respectively. Moreover, using 1 as a filler and poly (vinylidene difluoride) (PVDF) as matrix, a mixed matrix membrane 1@PVDF was successfully prepared. 1@PVDF also exhibited fluorescence emission comparable to that of 1 and could be used for hemin and 4-NP sensing with good selectivity and remarkable recyclability.

Luminescent Metal-Organic Framework Sensor for Detection of Biomarker 2-Thiothiazolidine-4-Carboxylic acid

Using terephthalic acid (BDC) as the organic ligand and zirconium chloride (ZrCl4) as the metal source, a lanthanide metal-organic framework (Tb/Zr-UiO-66) with excellent luminescence properties was successfully prepared by introducing the lanthanide ion Tb3+ in situ through a simple one-pot hydrothermal reaction, which was designed as an optical biosensor for 2-thiothiazolidine-4-carboxylic acid (TTCA), the urinary biomarker of human exposure to carbon disulfide (CS2). The fabricated Tb/Zr-UiO-66 exhibits high chemical and luminescent stability, making it competent for recognizing TTCA in aqueous environments. Significantly, its luminescence intensity change shows a good linearity relationship with the concentration of TTCA in the range of 0-110 μM, with a limit of detection (LOD) as low as 0.14 μM. Meanwhile, this sensor exhibits good selectivity and anti-interference ability towards TTCA among the various coexisting components in urine (Na+, K+, NH4+, SO42−, Cl −, creatine, creatinine, glucose, urea, etc.), and can quickly respond to TTCA within 2 minutes. The analysis results of PXRD, fluorescence lifetime and UV-vis spectrum demonstrate that the sensing mechanism can be ascribed to the competition absorption effect between TCAA and Tb/Zr-UiO-66. This biosensor with simple synthesis, stable framework, high sensitivity and selectivity, and rapid response has potential to become a powerful tool for diagnosing diseases associated with CS2 exposure.

An electrochemiluminescence sensor based on lanthanide bimetallic MOFs with a “cascade sensitization mechanism” for the sensitive detection of CA242

Lanthanide metal-organic frameworks (Ln-MOFs) broaden the optical sensing applications of lanthanide ions due to the antenna effect between organic ligands and metals. However, the sensitization ability of the ligand to metal ions is limited, and maximizing the sensitization of the electrochemiluminescence behavior of Eu3+ is still a challenge for the application of Ln-MOFs. Therefore, under the guidance of the “cascade sensitization mechanism” based on the antenna effect sensitizing the electrochemiluminescence of bimetallic Ln-MOFs, we proposed Eu/Tb-MOFs with high luminescence intensity as a signal probe. According to the antenna effect, the conjugated structure and high extinction coefficient of the benzene ring of 2-amino terephthalic acid (NH2-BDC) can enhance the ECL luminescence intensity of Eu/Tb-MOFs. Tb3+ can act as an energy bridge between NH2-BDC and Eu3+, buffering the energy gap. The bimetallic sensitization is formed between Tb3+ and Eu3+, which can inhibit the reverse internal flow of energy and ensure the high luminous efficiency of Eu3+. In addition, the nanosphere mixed valence Fe3O4 as a co-reactant accelerator promotes the formation of transient free radical SO4•- through the valence change of Fe2+/Fe3+. The ECL immunosensor constructed by luminophores Eu/Tb-MOFs and nanosphere Fe3O4 provided a new explanation for the ECL self-luminous of Eu/Tb-MOFs.

Integration of lanthanide MOFs/methylcellulose-based fluorescent sensor arrays and deep learning for fish freshness monitoring

Preserving fish meat poses a significant challenge due to its high protein and low fat content. This study introduces a novel approach that utilizes a common type of lanthanide metal-organic frameworks (Ln-MOFs), EuMOFs, in combination with 5-fluorescein isothiocyanate (FITC) and methylcellulose (MC) to develop fluorescent sensor arrays for real-time monitoring the freshness of fish meat. The EuMOF-FITC/MC fluorescence films were characterized with excellent fluorescence response, ideal morphology, good mechanical properties, and improved hydrophobicity. The efficacy of the fluorescence sensor array was evaluated by testing various concentrations of spoilage gases (such as ammonia, dimethylamine, and trimethylamine) within a 20-min timeframe using a smartphone-based camera obscura device. This sensor array enables the real-time monitoring of fish freshness, with the ability to preliminarily identify the freshness status of mackerel meat with the naked eye. Furthermore, the study employed four convolutional neural network (CNN) models to enhance the performance of freshness assessment, all of which achieved accuracy levels exceeding 93 %. Notably, the ResNext-101 model demonstrated a particularly high accuracy of 98.97 %. These results highlight the potential of the EuMOF-based fluorescence sensor array, in conjunction with the CNN model, as a reliable and accurate method for real-time monitoring the freshness of fish meat.

Four Lanthanide(III) Metal-Organic Frameworks Fabricated by Bithiophene Dicarboxylate for High Inherent Proton Conduction.

Currently, it is still a challenge to directly achieve highly stable metal-organic frameworks (MOFs) with superior proton conductivity solely through the exquisite design of ligands and the attentive selection of metal nodes. Inspired by this, we are intrigued by a multifunctional dicarboxylate ligand including dithiophene groups, 3,4-dimethylthieno[2,3-b]thiophene-2,5-dicarboxylic acid (H2DTD), and lanthanide ions with distinct coordination topologies. Successfully, four isostructural three-dimensional lanthanide(III)-based MOFs, [Ln2(DTD)3(DEF)4]·DEF·6H2O [LnIII = TbIII (Tb-MOF), EuIII (Eu-MOF), SmIII (Sm-MOF), and DyIII (Dy-MOF)], were solvothermally prepared, in which the effective proton transport will be provided by the coordinated or free solvent molecules, the crystalline water molecules, and the framework components, as well as a large number of highly electronegative S and O atoms. As expected, the four Ln-MOFs demonstrated the highest proton conductivities (σ) being 0.54 × 10-3, 3.75 × 10-3, 1.28 × 10-3, and 1.92 × 10-3 S·cm-1 for the four MOFs, respectively, at 100 °C/98% relative humidity (RH). Excitingly, Dy-MOF demonstrated an extraordinary ultrahigh σ of 1 × 10-3 S·cm-1 at 30 °C/98% RH. Additionally, the plausible proton transport mechanisms were emphasized.

A smartphone sensing platform for the sensitive and selective detection of clothianidin based on MIP-functionalized lanthanide MOF.

Anovel molecularly imprinted nanomaterial (Eu (BTC)-MPS@MIP) was synthesized on the surface of silanized europium-based metal-organic frameworks (Eu (BTC)-MPS) using 1, 3, 5-benzotrioic acid (H3BTC) as a ligand. The resulting Eu (BTC)-MPS@MIP was applied to constructing a smartphone sensing platform for the sensitive and selective detection of clothianidin (CLT) in vegetables. The synthesized Eu (BTC)-MPS@MIP demonstrated the successful formation of a typical core-shell structure featuring a shell thickness of approximately 70 - 80nm. The developed sensing platform based on Eu (BTC)-MPS@MIP exhibited sensitivity in CLT detection with a detection limit of 4µg/L and a linear response in the range 0.01 - 10mg/L at excitation and emission wavelengths of 365nm and 617nm, respectively. The fluorescence sensing platform displayed excellent specificity for CLT detection, as evidenced by a high imprinting factor of 3.1. This specificity is primarily attributed to the recognition sites in the molecularly imprinted polymer (MIP) layer. When applied to spiked vegetable samples, the recovery of CLT ranged from 78.9 to 102.0%, with relative standard deviation (RSD) values falling between 2.2 and 6.2%. The quenching mechanism of Eu (BTC)-MPS@MIP toward CLT can be attributed to the inner filter effect (IFE), resulting from the optimal spectral overlap between the absorption spectrum of CLT and the excitation spectra of Eu (BTC)-MPS@MIP. The proposed method has the potential for extension to the detection of other pesticides by replacing the MIP recognition probes.

Introduction of functionality into a Tb(III)-organic framework via mixed-ligand strategy for selective C2H2 capture and ratiometric Cr(VI) detection

Introduction of porosity and fluorescent properties into lanthanide metal–organic frameworks (MOFs) with rational design to achieve multifunctional use is of great significance from the energy and environmental viewpoint. In this study, a microporous Tb(III)-based MOF with the formula of {[Tb2(oba)3(Phen)2](DMF)2(H2O)4}n (1) was solvothermally prepared via using the mixed ligands of 1,10-phenanthroline (Phen) and 4,4′-oxybis(benzoic acid) (H2oba) as organic connecters. The structural evaluation results indicate that complex 1 is composed of binuclear Tb2(CO2)6(Phen)2 clusters which are extended by the oba2− ligands to afford a two-fold interpenetrated framework with one-dimensional microporous channels along the b-axis. Gas sorption studies show that the activated 1 demonstrates a high ideal adsorption solution theory (IAST) sorption selectivity of 7.4 toward C2H2 in a C2H2/CO2 gas mixture, which are further supported by the dynamic breakthrough experiments. The grand canonical Monte Carlo (GCMC) simulation results indicate that the synergistic effects of the H-bond interactions of C2H2 with oba2− ligands and the C–H···π interactions with Phen ligand contribute to the strong binding of the framework toward C2H2 molecules. What's more, the luminescent measurements reveal that the emission of 1 features both the characteristic peaks of Phen ligand and Tb(III) ion, which could be further applied as a self-calibrating sensor for the Cr(VI) detection in water. To the best of our knowledge, complex 1 represents the first example of Tb-MOF holding such a high C2H2/CO2 selectivity together with ratiometric Cr(VI) detection performances.

Enhancement of Luminescence from Lanthanide Metal–Organic Frameworks by Ytterbium and Calcium Doping: Application to Photonic Barcodes and Fingerprint Detection

AbstractEmission from metal–organic frameworks (MOFs) made from Eu3+ and 1,3,5‐benzenetricarboxylic acid (BTC) is enhanced eightfold by doping with Y3+ and Ca2+ ions. The Ca2+ ions are shown to substitute into the MOFs, and the MOFs structure is shown to be retained at high Y3+ doping levels. The emission enhancement is shown to be associated with variations in the local electric field at the Eu3+ centers in the MOFs. Calculations indicate that the HOMO and LUMO levels vary considerably with both Y3+ doping and with low‐level Ca2+ doping. These then modulates Eu3+ concentration quenching, ligand‐metal energy transfer processes, and the local electric field at the Eu3+ centers, qualitatively accounting for the primary observed features. For UV excitation (250, 295, and 393 nm, respectively), the greatest emission enhancement comes from the doped MOFs with 10% Eu3+, 89% Y3+, and 1% Ca2+. In a photonic barcode application, the doped MOFs are shown to facilitate increased information storage density, and in a fingerprinting application, they are displayed to lead to higher photostability and reduced materials demand.

Fluorescence turn off-on continuous response of dual lanthanide metal organic frameworks for selective detecting fluoroquinolone antibiotics

Eu3+ and Tb3+ as central ions and 1,4-phthalic acid (H2BDC) as ligand, a dual lanthanide metal-organic framework, Eu-Tb(BDC), was synthesized by co-precipitation method. The products performed stable crystal structure and adjustable fluorescence color. Eu0.15Tb2.85 (BDC) 3.0 was selected as an optimized probe to detect norfloxacin (NFX) in urine, and the fluorescence color was found to transfer from bright yellow to dark cyan and then to strong green with increasing NFX concentration. Mechanism analysis revealed that NFX with low concentration (10−6-10−3 M) stimulated light competition with BDC ligand due to internal filtration effect (IFE), resulting in the gradual fluorescence shutdown of Eu3+and Tb3+. While further increasing concentration of NFX to 10−3-10−2 M, the antibiotic molecules coordinated with lanthanide ions and transitioned their role from competitor to assistant. Where the energy transfer due to antenna effect overwhelmed IFE, the exciting light energy were retransferred to Eu3+ or Tb3+, and the probe's fluorescence restored. Generally, the Eu-Tb(BDC) probe performed fluorescence turn off-on response to norfloxacin with continuous concentration changing. Additionally, when detecting other fluoroquinolone antibiotics, the fluorescence of Eu0.15Tb2.85(BDC)3.0 changed from bright yellow to bright blue and eventually to dark red, which was attributed to the different coordination degrees of various antibiotic molecule with Tb3+ and Eu3+. It can be used to distinguish norfloxacin from other fluoroquinolone antibiotics.

On-Off Ratiometric Fluorescence Europium(III) Metal-Organic Framework for Quantitative Detection of the Inflammatory Marker Neopterin.

Benefiting from the unique photoluminescence behavior of the lanthanide(III) ions and organic ligands, a lanthanide(III) metal-organic framework (Ln-MOF) material can simultaneously demonstrate photoluminescence of lanthanide(III) cations and organic molecules and endow its superior applications of fluorescence sensing behaviors. Herein, we present a europium(III) MOF material {[Eu2(BPTA)·(CH3COO)2·3DMA]·0.5DMA·3H2O}n (1) (where H4BPTA is 3,3',5,5'-biphenyltetracarboxylic acid) for photoluminescence performance of quantitatively sensing the inflammatory marker neopterin (Neo). The obtained 1 comprises Eu2(COO)4 paddlewheel secondary building units, which could be bridged by BPTA4- ligands to extend a 2D framework. The fluorescence titration indicates 1 can achieve simultaneous fluorescence behavior of Eu3+ ions and Neo via on-off ratiometric effects and thus could be exploited as the ratiometric fluorescence sensor matrix. Such a fluorescence phenomenon of 1 as a ratiometric sensor for quantitative detection of Neo via an on-off ratiometric effect is never observed in MOF chemistry. Moreover, naked-eye visible color variations of the fluorescence for 1 could be observed from red to blue with increasing concentrations of Neo, confirmed by fluorescent test strips as well as portable fluorescent hydrogels. And 1 also shows a low detection limit of 15.11 nM. A synergetic contribution of the competitive absorption, fluorescence resonance energy-transfer, and photoinduced electron-transfer mechanisms between Neo and the framework of 1 realizes the on-off ratiometric fluorescence behavior for Neo detection, supported by the UV-vis spectral overlap experiment and DFT calculations.

Design of a dual-mode ratiometric fluorescent probe via MOF-on-MOF strategy for Al (III) and pH detection

BackgroundThe construction of ratiometric fluorescent MOF sensors with integrated self-calibration and dual-channel detection can efficiently overcome the deficiencies of single-signal sensing. In this regard, the rational design of structurally functionalized MOFs is paramount for enhancing their performance in ratiometric fluorescent sensors. Lately, the concept of MOF-on-MOF design has garnered notable interest as a potential strategy for regulating the structural parameters of MOFs by integrating two or more distinct MOF types. Great efforts have been dedicated to exploring new MOF-on-MOF hybrids and developing their applications in diverse fields. Even so, these materials are still in the stage of advancement in the sensing field. ResultsHerein, a Zr-based metal-organic framework anchored on a rare-earth metal-organic framework (UiO-66(OH)2@Y-TCPP) was prepared for the ratiometric fluorescence detection toward Al (III) and pH. In this probe, the UiO-66(OH)2 featured hydroxyl active sites for Al (III), leading to a significant enhancement in fluorescence intensity upon the addition of Al (III), while the signal emitted by the red-emitting Y-TCPP, serving as the reference, remained constant. UiO-66(OH)2@Y-TCPP exhibited excellent selectivity for Al (III) sensing with a wider linear range of 0.1–1000 μM, and a lower detection limit of 0.06 μM. This probe has also been utilized for the quantitative determination of Al (III) in hydrotalcite chewable tablets with satisfactory results. In addition, the probe realized ratiometric pH sensing in the range of 7–13 using UiO-66(OH)2 as an interior reference. The paper-based probe strip was developed for visual pH sensing. By installing color recognition and processing software on a smartphone, real-time and convenient pH sensing could be achieved. SignificanceThis is the first ratiometric fluorescent sensor for Al (III) and pH detection based on a MOF-on-MOF composite probe, which yields two different response modes. The detection results of Al (III) in hydrotalcite chewable tables and smartphone imaging for pH test paper demonstrate the practicability of the probe. This work opens up a new outlook on constructing a multi-functional application platform with substantial potential for employment in environmental and biological analysis tasks.

A multifunctional Eu-MOF with multi-color and proton conduction switching and its anti-counterfeiting applications

Lanthanide metal-organic frameworks (Ln-MOFs) have exhibited remarkable capabilities in color change, luminescence, proton conduction through the strategic modification of metal nodes, organic ligands and channels or pores. By modifying the electron-deficient bipyridinium to contain carboxylic acid moieties and coordinating them with the luninescent Eu3+ ion, a unique and versatile Eu-MOF has been synthesized. Under UV light conditions, the complex shows an obvious color change from colorless to blue, which is due to the formation of viologen radicals after photoinduced electron transfer (PIET) process. As we all know, the changed color is caused by the alteration of absorption intensity, ultimately impacting its luminescence as well. Thus, the bright and strong red fluorescence of this complex is quenched upon continuous UV light irradiation, which may be attributed to intramolecular energy transfer from the excited state of the europium ion to the colored state of the CV ligand. Based on the control of multiple colors of the complex, the designed encryption model can realize multiple anti-counterfeiting of real numbers. In addition, the conductivity of this compound increases significantly after UV illumination, showing excellent photo-modulated proton conductivity. In short, our work has proposed a multifunctional bipyridinium-based Ln-MOF with photochromism, photo-switchable photoluminescence and proton conduction, which offers valuable insights for the creation of versatile switchable materials based on MOFs.

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.