Europium Metal-organic Framework Research Articles

Sensitive detection of the antibiotic pollutants by a solvent-stable luminescent sensor based on a europium(III) metal-organic framework

The nitrofuran/nitroimidazole/sulfonamide antibiotics are significant chemotherapeutic agents for the prevention and treatment of infections by bacteria. However, the misuse of antibiotics can trigger antimicrobial resistance or even result in environmental pollution by antibiotic residues. In this regard, sensitive recognition of antibiotics associated with a quantitative platform is desirable. Herein, the antibiotic pollutants can be quantitatively detected by a new luminescent sensor derived from a stable europium(III) metal-organic framework, namely {[Eu2(FDA)3(H2O)3(DMF)·DMF·2H2O]}n (Eu-MOF, H2FDA ​= ​furan-2,5-dicarboxylic acid). The Eu-MOF features a 6,6-connected pcu alpha-Po primitive cubic topology with 1D channels occupied by lattice N,N-dimethylformamide and water molecules. More importantly, the Eu-MOF represents superior luminescent properties, which can be quenched by trace amounts of the nitrofuran/nitroimidazole/sulfonamide antibiotics at μM levels in water. The results indicate that Eu-MOF is qualified as a promisingly favorable sensor for the sensitive detection of the antibiotics in water, being potentially beneficial for monitoring water quality.

Eu(III)-based metal-organic-frameworks luminescent probe and its sensing properties for nitrobenzene and Cu(II)

A novel europium metal-organic frameworks (Eu-MOFs), based on 1,3,5-benzotricarboxylic acid (H3BTC), 4,4′-azopyridine (4,4′-AZ) and N,N-dimethyllformamide (DMF), was synthesized by the solvothermal method. The crystal structure, thermal stability, morphology and luminescent properties are characterized by the X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and optical spectroscopic techniques. The Eu-MOFs display a unique luminescence quenching effect to nitrobenzene (NB) and copper (Cu2+) ions. The turn-off luminescence can be induced by 210 ​ppm NB or by 1000 ​μM Cu2+ ions. Furthermore, the high sensitivities (KSV ​= ​0.039 ​ppm−1 for NB, and KSV =0.029 ​μM−1 for Cu2+) and low detection limits (0.656 ​ppm for NB, and 1.395 ​μM for Cu2+) are obtained. The sensing mechanisms are reasonably explained based on the electron and energy transfer. The experimental results show that the Eu-MOFs can be used as a potential sensing luminescence quenching probes for NB and Cu2+ ions.

A Europium-Organic Framework Sensing Material for 2-Aminoacetophenone, a Bacterial Biomarker in Water.

2-Aminoacetophenone (2-AA) is a metabolite produced in large quantities by the pathogenic bacteria Pseudomonas aeruginosa (PA), which is a biomarker for PA in water. State-of-the-art analytical techniques to detect PA usually require expensive instruments and a long analysis time which are not suitable for real-time water quality monitoring, especially for high-quality drinking water. Herein, we reported the application of a europium metal-organic framework (Eu-MOF) as a luminescent sensing material, which provides a facile, environmentally friendly and low-cost way for the fast detection of PA in water. Eu-MOF shows a high sensitivity toward 2-AA with a KSV value of 3.563 × 104 M-1, rapid luminescence response in 12 s and high-selectivity and anti-interference ability with the existence of common detection indexes in drinking water owing to the good match of the energy levels of Eu-MOF and 2-AA. A systematical optimization of the sensing conditions to enhance the sensing function of Eu-MOF for 2-AA was discussed in detail, to give fundamentals for the rational design of MOF-based sensing materials.

Structural Variation and Switchable Nonlinear Optical Behavior of Metal-Organic Frameworks.

Two europium metal-organic frameworks (MOFs) based on the same ligand, named as ZJU-23-Eu and ZJU-24-Eu, are selectively synthesized by fine-tuning solvent contents to tailor the coordination modes. Eu atoms are eight-coordinated and nine-coordinated in ZJU-23-Eu and ZJU-24-Eu respectively, and their frameworks vary in both spatial connectivity and symmetry. The ligand not only has multiphoton response but also suitable triplet energy level (19998cm-1 ) to sensitize Eu3+ . Thus ZJU-23-Eu exhibits characteristic emission of Eu3+ peaking at 614nm via the energy transfer from the two-/three-photon excited ligand to Eu3+ , with its bidimensional layered structure benefiting this process. In contrast, the changed spatial connectivity in tridimensional ZJU-24-Eu narrows the distances between adjacent Eu3+ ions and reduces the density, resulting in poor two-photon excited fluorescence. Besides, noncentrosymmetric ZJU-24-Eu shows second harmonic generation (SHG) response with an intensity of ≈6.2 times relative to KH2 PO4 (KDP) microcrystalline powder while centrosymmetric ZJU-23-Eu cannot. These results have established two nonlinear optical (NLO) models based on MOFs to synchronously analyze the effects of two structural variables on different NLO behaviors, and provide ingenious ways to design MOF-based NLO devices with function on demand.

A High Selectively and Sensitively Fluorescent Europium Metal-Organic Framework Sensor for Detecting Nitro Aromatic Compounds in Aqueous Media

A High Selectively and Sensitively Fluorescent Europium Metal-Organic Framework Sensor for Detecting Nitro Aromatic Compounds in Aqueous Media

Solid-state N,P-doped carbon dots conquer aggregation-caused fluorescence quenching and couple with europium metal-organic frameworks toward white light-emitting diodes

As a newly discovered photoluminescent material, carbon dots (CDs) have shown promising performance in many fields. However, due to aggregation-caused fluorescence quenching, most of CDs are poorly emissive in the solid state, which severely restricts their wide applications, especially in the optoelectronic devices. To overcome this problem, herein, we design a novel kind of self-quenching-resistant N,P-doped CDs, using polyethyleneimine (PEI), phosphoric acid, and ethanol as raw ingredients. The as-synthesized CDs are amorphous and contain abundant surface PEI chains which properly separate the individual carbon core and prevent the direct π–π interaction. Such a unique structure conquers self-quenching during aggregation, and gives CDs a bright blue fluorescence in solid state without any other additional matrices. By taking advantage of their excellent optical properties, the CD powers, combined with red emissive europium metal-organic frameworks, are successfully employed as hybrid phosphors for construction of white light-emitting diodes exhibiting a Commission Internationale de L'Eclairage (CIE) coordinate of (0.33, 0.33).

Europium metal-organic framework containing helical metal-carboxylate chains for fluorescence sensing of nitrobenzene and nitrofunans antibiotics

Food safety and environmental pollution have become prevalent concerns around the world. The development of a facile detection method towards nitroaromatic pollutants and antibiotics in the environment is exceedingly desirable for protecting human health and controlling the risks of sanitation pollution. Herein, a new europium metal-organic framework (Eu-MOF), which is built from helical rod-shaped europium carboxylate chains, has been synthesized and broadly explored. The compound exhibits intense red luminescence output of typical Eu3+ ions both in solid and in the alcohol solutions. Notably, it shows rapid and efficient fluorescence quenching effects towards the nitrobenzene (NB) and nitrofurans antibiotics (NFAs). As a dual-functional chemosensor, the Eu-MOF has a broad application prospect for its sensitive identification and visual detection in the future. The mechanism of the quenching effect was investigated in detail, and the density functional theory also proved the result.

Controllable Production of Micro-nanoscale Metal-Organic Frameworks Coatings on Cotton Fabric for Sensing Cu2+

Luminescent lanthanide metal-organic frameworks (ln-MOFs) is a promising materials for sensing. However, seeking ideal method to scale up in mass production and can be uniform on flexible substrate is still a great challenge. In this study, a novel and efficient process was employed for the fabrication of flexible and environmental copper ion-sensing materials using cotton fabric as a substrate. The micro-nanoscale Europium metal-organic frameworks (Eu-MOFs) was prepared through adding blocking reagent, and then cotton fabric was coated with the Eu-MOFs by hot pressing. The results show that controllable dense micro-nanoscale Eu-MOFs film was coated on the cotton fabric with different dipping and hot pressing times. The method is fast, simple, low-cost and suitable for production. The Eu-MOFs coated cotton fabric exhibits good photoluminescent properties. The selective sensing ability of Eu-MOFs coated fabric for Cu2+ over many other metal ions (K+, Cd2+, Ca2+, Pb2+, Na+, Zn2+, Ni2+, Mg2+, Al3+ and Co2+) is verified by emission spectra, and by the fact that the fluorescence intensity of the fabric significantly decreased with an increase in the concentration of Cu2+ (10−6—10−1 mol/L). This method provides a new path for the controllable production of MOFs-coated functional textiles for different applications, such as anti-counterfeiting, UV-protection, superhydrophobic, and sensing materials in the textile industry.

A dual luminescent chemosensor derived from a europium(III) metal-organic framework for quantitative detection of phosphate anions and acetylacetone in aqueous solution

A luminescent europium(III) metal-organic framework (MOF) {[Eu(bcpt)(HCOO)]·0.5H2O}n (1) has been synthesized under solvothermal conditions by adopting a elongated ligand encompassing three aromatic rings groups, 3,5-bis(4′-carboxy-phenyl)-1,2,4-triazole (H2bcpt). This MOF demonstrates a binodal (4,10)-connected framework with a Schläfli symbol of {34·42}{38·414·516·67}, in which the adjacent Eu(III) ions can be bridged by HCOO− anions to form a 2D layer and further connected by H2bcpt as a pillar to generate a 3D pillared-layer structure. Notably, such a binodal (4, 10)-connected topological structure is rarely explored in MOF family, particular of lanthanide(III) MOF chemistry. Furthermore, 1 could be exploited as a dual luminescent chemosensor to probe PO43− anions and acetylacetone in aqueous solution with the average quenching Ksv values of 1.27 × 104 L mol−1 and 322 L mol−1, and the detection limits of 2.74 × 10−4 mol L−1 and 1.21 × 10−4 mol L−1, respectively.

Europium metal-organic framework for selective and sensitive detection of doxycycline based on fluorescence enhancement

Metal-organic framework is an extended coordination compound with repeating coordination entities and voids, which shows potential applications in gas storage, separation, catalysis, and etc. This work reports the synthesis of a new functional metal-organic framework of pyromellitic acid and europium, and its application in fluorescence sensing of doxycycline, a broad-spectrum polyketide antibiotic on the basis of fluorescence turn-on method. The metal-organic framework was initially non-fluorescent, however, with the addition of doxycycline, the system exhibited significant fluorescence enhancement at 526 nm and 617 nm, where both fluorescence intensities showed good linear correlations with the doxycycline concentration, suggesting the possibility for direct two-channel detection without any sensitization materials such as metal particles or surface-modified quantum dots. More interestingly, the unique fluorescence response of the system could discriminate doxycycline from other tetracycline antibiotics with high selectivity, and a limit of detection (LOD) was estimated to be 47 nM. It has been further demonstrated that the material has been successfully applied as sensing materials for selective determination of doxycycline in real samples of fish and urine.

Highly sensitive and selective detect of p‐arsanilic acid with a new water‐stable europium metal–organic framework

The p‐arsanilic acid (p‐ASA), as an aromatic organoarsenic compounds, had received considerable concerns for their potential toxicity and carcinogenic properties. It was essential to detect p‐ASA with a facile method. In this paper, an europium based fluorescent metal–organic framework (MOF) [Eu2(clhex)·2H2O)]·H2O (BUC‐69) was successfully prepared under hydrothermal conditions with 1,2,3,4,5,6‐cyclohexanehexacarboxylic acid (H6clhex) as organic linker. BUC‐69 displayed superior fluorescence capability to achieve selective and sensitive detection toward p‐ASA in water, which presented the first example of a MOF‐based sensor to detect p‐ASA. BUC‐69 showed excellent chemical stability in solutions under pH ranging from 4 to 12, which makes it be a potential sensor both in acidity and alkalinity condition. Significantly, BUC‐69 performed well in fluorescent sensing of p‐ASA at a low concentration (10−6 M) in the simulated wastewater prepared with real lake water, and the results were comparable to the values detected by Inductively Coupled Plasma Optical Emission Spectrometer (ICP‐OES). The corresponding mechanism of fluorescent sensing toward p‐ASA with BUC‐69 was proposed and affirmed.

Facile one-step solvothermal synthesis of a luminescent europium metal-organic framework for rapid and selective sensing of uranyl ions.

A simple, cost-effective, and portable uranium sensory material with adequate selectivity is increasingly urgent and would be of great importance in environmental monitoring of radionuclides. Herein, we report a novel luminescent europium metal-organic framework (Eu-MOF) with plenty of Lewis basic sites for binding uranyl ions (UO22+), the most common form of uranium in solution, through a facile one-step solvothermal synthetic route. The mesoporous structure consists of europium nodes and flexible nitrogen-containing ligands with a 29.2 × 20.5Å2 channel along the c-axis. Furthermore, the obtained material displays characteristic fluorescence of trivalent Eu3+ and could be applied as a turn-off sensory probe targeting UO22+ in solution. Differential fluorescent quenching occurred upon a series of potential interfering ions compared to UO22+ and the detection limit as low as 0.9μM was achieved with a rapid response. Graphical abstract.

Efficient and selective sensing of Cu2+ and UO22+ by a europium metal-organic framework

We report here the investigation of using a luminescent europium organic framework, [Eu2(MTBC)(OH)2(DMF)3(H2O)4]·2DMF·7H2O (denoted as compound 1), for detecting of both Cu2+ and UO22+ with high sensitivity. Based on the spectroscopy analysis, compound 1 could selectively respond to Cu2+ and UO22+ ions among other selected monovalent, divalent, trivalent metal cations based on a turn-off mechanism. The detection limit of compound 1 towards Cu2+ ion was as low as 17.2 μg/L, which is much lower than the maximum tolerable concentration of Cu2+ in drinking water (2 mg/L) defined by United States Environmental Protection Agency. On the other hand, the detection limit towards UO22+ ions is 309.2 μg/L, which could be used for detecting uranium in relative severely contaminated areas. The concentration-dependent luminescence intensity evolution process could be fully understood by the absorption kinetics and isotherm investigations. Furthermore, the quenching mechanism was elucidated by the UV-vis, excitation, luminescence, and lifetime studies. Compound 1, as the first MOF based luminescence probe for both Cu2+ and UO22+ ions, provides insight into developing MOF-based multifunctional sensors for both nonradioactive and radioactive elements.

Dual-emission of Eu based metal-organic frameworks hybrids with carbon dots for ratiometric fluorescent detection of Cr(VI)

A novel blue fluorescence nitrogen and cobalt(II) co-doped carbon dots (CDs) encapsulated in europium metal-organic frameworks (CDs@Eu-MOFs) were synthesized to form a ratiometric fluorescent sensor for the detection of Cr(VI). The CDs@Eu-MOFs were characterized by transmission electron microscopic (TEM), scanning electron microscopic (SEM), Fourier transform infrared (FT-IR) and X-ray powder diffraction (XRD) techniques. The as-prepared CDs@Eu-MOFs not only kept the fascinating optical properties of CDs and Eu3+ to give dual-emission but also had good stability in an aqueous solution. In the presence of Cr(VI), the fluorescence intensity of the CDs decreased and the intensity of the Eu-MOFs remained. Under optimized conditions, the synthesized CDs@Eu-MOFs showed high sensitivity and selectivity with a linear range from 2 to 100 μM and a detection limit of 0.21 μM for the detection of Cr(VI). The possible mechanism is discussed. Meanwhile, the fluorescence sensor was successfully utilized to detection of Cr(VI) in natural samples with good recoveries ranges.

The mixed-ligand strategy to assemble a europium metal-organic framework with a 2-fold-interpenetrated network

A novel europium complex with the mixed ligands of 1-methyl-3,5-bis(4′-carboxy-phenyl)-1,2,4-triazole (mbcpt) and p-phthalic acid (pa), [Eu2Cl2(H3O)2(μ4-mbcpt)2(μ4-pa)]n (1), has been synthesized under the solvothermal conditions and structurally characterized by single-crystal X-ray diffraction. Complex 1 exhibits a three-dimensional (3-D) metal-​organic framework. The 3-D open framework features a 2-fold-interpenetrated network. Solid-state diffuse reflectance spectroscopy uncovers the presence of a wide optical band gap of 3.56 eV, indicating that it is a wide band gap organic semiconductor material. Solid-state photoluminescence measurement reveals that complex 1 shows red light emission bands locating at 602, 611, 642 and 690 nm, which can be assigned to the 5D0 → 7FJ (Eu3+) with the value of J = 1, 2, 3 and 4, respectively. Magnetic measurements reveal that complex 1 shows an antiferromagnetic behavior.

A europium(III) metal-organic framework as ratiometric turn-on luminescent sensor for Al3+ ions

本文制备了三种同构镧系金属有机框架材料(Me2NH2)[Ln2L2(NO3)2(μ3-OH)(H2O)]·2H2O·2DMA, (Ln = Eu( 1 ), Gd( 2 ), Tb( 3 ), H2L = 9-甲基-9-羟基-2,7-芴二羧酸, DMA = 二甲基乙酰胺). 研究结果显示它们具有三维阴离子型框架结构, 该结构可简化为含有单一的8连接型节点的体心立方(bcu)型拓扑结构. 化合物 1 表现出基于配体的荧光发射峰以及铕离子的特征荧光发射峰. 荧光实验表明在DMF溶液中Al3+会明显增强配体的荧光强度, 而对Eu3+的荧光强度影响却很小, 这使得 1 成为了优秀的比率式发光Al3+传感器. 在Al3+浓度处于 0.02–0.1 mmol L−1 范围内时, 配体与Eu3+荧光强度的比值与Al3+浓度成正比(斜率为 18502 mol−1 L). 本文证实了配体9位的羟基与Al3+之间的相互作用是引起配体荧光增强的主要原因.

A new europium metal–organic framework with both high proton conductivity and highly sensitive detection of ascorbic acid

The highest proton conductivity of the new Eu-MOF reaches up to 1.0 × 10−4 S cm−1. Furthermore, it is an excellent luminescence-based sensor for detection of ascorbic acid (AA) in aqueous solutions.

3D water-stable europium metal organic frameworks as a multi-responsive luminescent sensor for high-efficiency detection of Cr2O72−, MnO4−, Cr3+ ions and SDBS in aqueous solution

A 3D water-stable europium metal organic framework has been synthesized. Fluorescence measurements show that the MOF can selectively and sensitively detect Cr2O72−, MnO4−, Cr3+ ions and SDBS in aqueous solutions.

A novel near monochromatic red emissive europium(III) metal-organic framework based on 1,2,4,5-benzenetetracarboxylate: From synthesis to photoluminescence studies

This work presents the synthesis, solid state characterization (infrared spectroscopy, thermal analysis (TGA/DTA), powder and single crystal X-ray diffraction) and photoluminescence studies of a new europium metal-organic framework (MOF), [Eu2(Btec)1,5(H2O)]n (Btec4−=1,2,4,5-benzenetetracarboxylate anion). Single crystal X-ray diffraction analysis reveals that the material has a three-dimensional network, with two crystallographically independent Eu(III) ions adopting different coordination geometries. This structure presents one of the Btec4− anions acting as a μ8-bridging linker, with the carboxylate groups in distinct connection to Eu(III) ions, culminating into an unknown coordination mode for the linker. The results of thermogravimetric analyses indicate that the MOF has high thermal stability, with this characteristic being of great interest for the application of these compounds in several fields such as catalysis and photonics. The luminescent properties showed that the Eu(III) ions are a local-spectroscopic probe, with the compound presenting a red emission when excited in the UV spectral region with absolute emission quantum yield values of 0.48 ± 0.05. The thermal dependence on the intensity of the transitions originating from the 7F1 level, especially the 7F1 → 5D1 transition, was studied. These results opens the possibility to test this MOF [Eu2(Btec)1.5(H2O)]n in the field of molecular thermometry.

Synthesis and characterization of Tb3+ and Eu3+ metal-organic frameworks with TFBDC2− linkers

In this study, terbium Tb3+ and europium Eu3+ metal-organic frameworks (MOFs) based on 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylic acid (TFBDC) were synthesized by precipitation and diffusion-controlled precipitation methods. The powders insoluble in aqueous media and polar solvents were obtained. The phase and chemical composition, microstructure and properties of Tb3+ and Eu3+ MOFs were evaluated and discussed. The synthesized terbium and europium metal-organic frameworks were characterized by thermal (TG/DSC) analysis, X-ray diffraction (XRD) analysis, infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and fluorescence spectroscopy (FLS).