Lanthanide Metal-organic Frameworks Research Articles

Lanthanide Metal–Organic Frameworks with High Chemical Stability as Multifunctional Materials: Cryogenic Magnetic Cooler and Luminescent Probe

Lanthanide Metal–Organic Frameworks with High Chemical Stability as Multifunctional Materials: Cryogenic Magnetic Cooler and Luminescent Probe

Fluorescent lanthanide metal-organic framework for rapid and ultrasensitive detection of methcathinone in human urine

Methcathinone (MC), a new and easily abused psychoactive substance, not only has a rigorous impact on public security, but also endangers people's health. Herein, novel fluorescent europium metal-organic frameworks (Eu-MOF) were synthesized through a facile one-step solvothermal strategy and utilized as an effective “signal-off” sensing platform for rapid and ultrasensitive detection of MC. The as-fabricated Eu-MOF possessed superior optical properties encompassing bright red fluorescence and good photostability. In the presence of MC, the fluorescence of Eu-MOF was significantly quenched, mainly attributing to the internal filtering effect between Eu-MOF and MC. The fluorescent signal showed high selectivity for MC over other illicit drugs, and offered two linear ranges of 1–100 ng/mL and 100–4000 ng/mL with a detection limit of 0.40 ng/mL. Strikingly, the nanoprobe could be applied for the assay of MC in human urine with satisfactory recoveries and acceptable results. This work provides a promising route for MC detection to effectively control illicit drug pandemic worldwide.

Luminescent trade-off effect arising from Y3+ ion doping in rare earth metal–organic framework solid solutions Tb1-xYx-PTC (H3PTC = pyridine-2, 4, 6-tricarboxylate)

A series of rare earth solid solutions, Tb1-xYx-PTC with pyridine-2, 4, 6-tricarboxylic acid (H3PTC), have been prepared using a hydrothermal synthesis method and characterized by single crystal and powder X-ray diffraction, IR spectroscopy, and thermogravimetric analysis techniques etc. Tb1-xYx-PTC are isomorphous with 1D zigzag metal-oxide chains and 2D coordination polyhedral layers, which are further interlinked into 3D framework by the connection of PTC3− ligands. The photoluminescent behaviors of the solid solutions Tb1-xYx-PTC were carefully studied. The QY of Tb1-xYx-PTC with appropriate amount of Y3+ ion is obviously enhanced due to reducing dipole–dipole and quadrupole–quadrupole interaction between emitters of Tb3+ ions. This study demonstrates that the formation of solid solutions by introducing optically inactive ions is an efficient strategy to get improved photoluminescent materials.

Excitation wavelength-dependent continuous color-tunable luminescence of fluorescent dyes encapsulated into lanthanide metal-organic framework for anti-counterfeiting

Excitation dependent luminescent materials, which have attracted significant scientific attention in the field of information security owing to information storage and luminescence properties. However, it remains a formidable challenge in developing excitation dependent luminescent materials with a simple synthesis method and predictably modulated luminescent outputs. Herein, a novel Ln3+/Fluorescent dyes@MOFs strategy is developed to generate excitation dependent continuous color-changing luminescent materials via a hydrothermal method and post-synthetic modification (PSM), based on metal-organic frameworks (MOFs) matrix doped with lanthanide cations and fluorescent dyes encapsulated into the lanthanide MOFs. The continuous proportional emission of mixed luminescence appeared within a single matrix in response to the different excitation wavelength and the proportional emission control (PEC) mechanism between the two luminescent centers is proposed. In addition, the photoluminescence platform demonstrates a distinct security method based on covert color that are controlled by distinct excitation wavelengths and excellent luminescence stability have also been verified in these new materials.

Microwave-assisted synthesis to prepare metal-organic framework for luminescence thermometry

The lanthanide metal-organic framework, La1.23Na0.30(1,3-BDC)2(H2O)·4H2O (1,3-BDC: 1,3-benzenedicarboxylate), has been for the first time synthesized under microwave-assisted hydrothermal conditions with a synthesis duration of 5 min. The substitution of La3+ by Eu3+ and Tb3+ was possible until a maximal content of 10%.mol and the investigation of luminescence properties reveals that emitting cations can be located in the chains formed by the LnO10 polyhedra but also into the polar channels proposed by the structure, where some La3+ crystallographic sites are also available. Finally, when codoped by Eu3+ and Tb3+, the materials exhibit thermometric properties in the cryogenic range with a maximal relative thermal sensitivity around 1% K−1 at 80 K.

Tunable rare-earth metal−organic frameworks for ultra-high selenite capture

Linkers and clusters with various conformations present challenges for the design and prediction of highly porous and stable rare-earth metal−organic frameworks (RE-MOFs) for trapping toxic ions in aqueous solutions. Herein, we designed and synthesized a series of RE-MOFs based on a malleable ligand to explore the effects of ligands, clusters, and configurations on structural stability. The results showed that the nonanuclear high-connected UPC-183 exhibited better stability than the hexanuclear low-connected RE-MOF (UPC-181/182 series). Due to the syngenetic effect of chemi- and physisorption, the adsorption capacity of UPC-183-Eu for selenite (SeO32-) is as high as 308.39 mg/g, recorded one of the highest ever reported for MOFs. Furthermore, we accurately analyzed the adsorption site of UPC-183-Eu for SeO32- through single-crystal structure and theoretical simulation. The ultra-high selenite adsorption capacity and removal efficiency endow UPC-183-Eu an excellent porous adsorbent for removing pollutants.

Accessing 14-Connected Nets: Continuous Breathing, Hydrophobic Rare-Earth Metal Organic Frameworks Based on 14-c Hexanuclear Clusters with High Affinity for Non-Polar Vapors.

Highly connected metal organic frameworks (MOFs) in which at least one building block has connectivity higher than twelve are very rare and much desirable. We report here the first examples of isostructural 14-connected MOFs, RE-frt-MOF-1, constructed from the assembly of 14-c hexanuclear rare-earth clusters, [RE6(μ3-X)8(COO)12]2- (RE: Y3+, Tb3+, Dy3+, Ho3+, Er3+, Yb3+ and X: OH-/F-) with a tritopic carboxylate-based organic linker. This linker serves as a 3-c and 4-c organic node resulting in the formation of a unique, trinodal (3,4,14)-c framework. RE-frt-MOF-1 are stable in air and alkaline aqueous solutions and show an intriguingly continuous, reversible breathing behavior, between a wide and a narrow-pore phase, upon guest removal. Crystallinity is retained during breathing, and single-crystal X-ray diffraction shed light into the associated structural transformation. Vapor sorption studies performed on Y-frt-MOF-1 revealed a high affinity for non-polar vapors such as n-hexane, cyclohexane, and benzene, displaying type I isotherms with high uptake at low relative pressures (<10-3 p/p0), associated with the hydrophobic nature of the 1D channels and also with their rhombic shape. In contrast, polar vapors such as acetonitrile and ethanol show type V isotherms due to favorable vapor-vapor interactions. Notably these vapors, except cyclohexane, trigger the transition from the narrow to the wide pore phase, accompanied by a remarkable increase in uptake, reaching 70.6, 109, 100.4, and 87.7% for n-hexane, benzene, acetonitrile, and ethanol, respectively.

Five Mesoporous Lanthanide Metal-Organic Frameworks: Syntheses, Structures, and Fluorescence Sensing of Fe3+, Cr2O72-, and H2O2 and Electrochemical Sensing of Trinitrophenol.

When a multicarboxylate aromatic ligand, 3,5-di(2',4'-dicarboxylphenyl)benzoic acid (H5L), was employed, five structurally similar lanthanide metal-organic frameworks (Ln-MOFs), {[Pr10L6(OH)3Cl(H2O)6]·4C2H8N}n (1), {[Nd10L6(OH)4 (H2O)9]·4C2H8N}n (2), {[Gd10L6(OH)4(H2O)3]·4C2H8N}n (3), {[Ho10L6(OH)4 (H2O)3]·4C2H8N}n (4) and {[Er10L6(OH)4(H2O)6]·4C2H8N}n (5), were synthesized and characterized. Single-crystal X-ray structural analyses disclosed that all five Ln-MOFs crystallize in the trigonal R3 space group. They have three-dimensional mesoporous structure featuring the coexistence of binuclear and tetranuclear species as inorganic building units. The mesoporous structure of 3 was verified by the gas adsorption experiment of N2. Fluorescence analysis showed that 3 can selectively detect Fe3+, Cr2O72-, and H2O2; furthermore, it can be used for the electrochemical detection of trinitrophenol. With the merit of an excellent highly sensitive detection performance, 3 has unpredictable application prospects in future research fields.

Dynamic Anticounterfeiting Through Novel Photochromic Spiropyran-Based Switch@Ln-MOF Composites.

Fluorescent materials presenting unique color changes in response to external stimuli have wide applications in information storage and anticounterfeiting. However, developing intelligent fluorescent materials with high security levels and dynamically displaying encrypted information is still a challenge. Herein, we report a new method for constructing excellent fluorescent materials by loading the photochromic molecule spiropyran into a lanthanide metal-organic framework. Controlling the isomerization of the spiropyran unit regulates the fluorescence resonance energy transfer (FRET) mechanism between the spiropyran acceptor and the lanthanide donor, leading to an exceptional reversible absorption/luminescence modulation ability. As the irradiation time is extended, the fluorescent color changes continuously from yellow-greenish to orange and then to red through the FRET process within 60 s. This composite system has great potential in anticounterfeiting because of the following advantages: (1) the materials have different fluorescence emissions and optical colors regulated by ultraviolet radiation, which is convenient for designing complex anticounterfeiting patterns; (2) the system can be repeatedly verified quickly and exhibit dynamic fluorescence color within 60 s, having great potential in advanced anticounterfeiting, where time is key in encryption/decryption. These unique advantages will greatly enhance the reliability of anticounterfeiting measures and increase the difficulty of anticounterfeiting.

Water-Stable Carborane-Based Eu3+/Tb3+ Metal-Organic Frameworks for Tunable Time-Dependent Emission Color and Their Application in Anticounterfeiting Bar-Coding.

Luminescent lanthanide metal–organic frameworks (Ln-MOFs) have been shown to exhibit relevant optical properties of interest for practical applications, though their implementation still remains a challenge. To be suitable for practical applications, Ln-MOFs must be not only water stable but also printable, easy to prepare, and produced in high yields. Herein, we design and synthesize a series of mCB-EuyTb1–y (y = 0–1) MOFs using a highly hydrophobic ligand mCBL1: 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane. The new materials are stable in water and at high temperature. Tunable emission from green to red, energy transfer (ET) from Tb3+ to Eu3+, and time-dependent emission of the series of mixed-metal mCB-EuyTb1–y MOFs are reported. An outstanding increase in the quantum yield (QY) of 239% of mCB-Eu (20.5%) in the mixed mCB-Eu0.1Tb0.9 (69.2%) is achieved, along with an increased and tunable lifetime luminescence (from about 0.5 to 10 000 μs), all of these promoted by a highly effective ET process. The observed time-dependent emission (and color), in addition to the high QY, provides a simple method for designing high-security anticounterfeiting materials. We report a convenient method to prepare mixed-metal Eu/Tb coordination polymers (CPs) that are printable from water inks for potential applications, among which anticounterfeiting and bar-coding have been selected as a proof-of-concept.

Stable Lanthanide Metal-Organic Frameworks with Ratiometric Fluorescence Sensing for Amino Acids and Tunable Proton Conduction and Magnetic Properties.

Four new isostructural lanthanide metal-organic frameworks (MOFs), namely {[Ln(DMTP-DC)1.5(H2O)3]·DMF}n [H2DMTP-DC = 2',5'-dimethoxytriphenyl-4,4″-dicarboxylic acid; LnIII = EuIII (1), GdIII (2), TbIII (3), and DyIII (4)], have been synthesized and characterized. Single-crystal structure analysis reveals that 1-4 are three-dimensional Ln-MOFs with rich H-bonding of coordinated H2O molecules in the network channels. The X-ray diffraction patterns indicate that Ln-MOF 1 displays good stabilities in organic solvents and aqueous solutions with distinct pH values. Both 1 and 3 show characteristic emission of LnIII ions. Ln-MOF 1 can be used as a ratiometric fluorescence sensor for arginine and lysine in aqueous solution, and the detection limits are 24.38 μM for arginine and 9.31 μM for lysine. All 1-4 show proton conductivity related to relative humidity (RH) and temperature, and the maximum conductivity values of 1-4 at 55 °C and 100% RH are 9.94 × 10-5, 1.62 × 10-4, 1.71 × 10-4, and 2.67 × 10-4 S·cm-1, respectively. The value of σ increases with the decrease in ionic radius, indicating that the radius of the LnIII ions can regulate the proton conductivity of these MOFs. Additionally, 2 exhibits a significant magnetocaloric effect (MCE) with a magnetic entropy change (-ΔSm) of 18.86 J kg-1 K-1 for ΔH = 7 T at 2 K, and 4 shows weak field-induced slow relaxation of magnetization. The coexistence of good fluorescence sensing capability, attractive proton conductivity, and relatively large MCE in Ln-MOFs is rare, and thus, 1-4 are potentially multifunctional MOF materials.

A selective dual-response biosensor for tyrosinase monophenolase activity based on lanthanide metal-organic frameworks assisted boric acid-levodopa polymer dots

Tyrosinase (TYR) monophenolase activity plays a key role in the development of diseases such as melanoma. The selective and sensitive detection of TYR monophenolase activity is a persistent challenge. Here, by integrating fluorescent polymer dots and a luminescent lanthanide metal-organic framework (Ln-MOF), we proposed an on-off dual-response biosensor for the sensitive and selective detection of TYR monophenolase. The Ln-MOF was prepared with Eu3+ and monoaromatic ligand dipicolinic acid (DPA), and it plays multiple functions such as fluorescent internal standard, chromaticity shift enhancement and fluorescence sensing. In alkaline boric acid (BA) buffer, L-tyrosine is converted into BA-levodopa by TYR monophenolase. Then, with the assistance of Eu-DPA, BA-levodopa is initiated by diethylaminepropyltrimethoxysilane (DAMO) to generate BA-levodopa polymer dots, which turn on strong blue fluorescence (crosslink-enhanced emission) and meanwhile quench the red fluorescence of Eu-DPA through enhanced photo-induced electron transfer. Thus, the sensitive and selective dual-response sensing to TYR monophenolase is achieved. Both DAMO and BA play significant roles in the synthesis of strong fluorescence polymer dots, and another key role of BA is to inhibit TYR diphenolase activity. Furthermore, chromaticity shift value-based quantification greatly improves the response linearity. The linear range is 0.05–2 U mL−1 (r = 0.9966), and the limit of detection is 0.004 U mL−1. The precise and accurate quantification of TYR monophenolase activity in saliva samples is realized (recovery of 96.9–102.0%, relative standard deviation < 9.56%). To our knowledge, it is the first highly-sensitive double-response biosensor for TYR monophenolase activity.

Lanthanide-Organic Frameworks with Uncoordinated Lewis Base Sites: Tunable Luminescence, Antibiotic Detection, and Anticounterfeiting.

Several new isostructural lanthanide metal-organic frameworks (Ln-MOFs), {[Ln2(L)3DMA4]·2DMA}n (1-Ln, where Ln = Eu, Tb, or EuxTb1-x), were first constructed via the solvothermal reactions of 4,6-di(4-carboxyphenyl)pyrimidine and Ln3+ ions. 1-Ln exhibits a 4-connected two-dimensional framework endowed with uncoordinated Lewis base sites. An exploration of luminescence sensing demonstrated 1-Eu can be used for the selectivity detection of dimetridazole and metronidazole antibiotics in other antibiotics, blood plasma, and urine, acting as an exceptional recyclable luminescent probe. More importantly, the luminescent inks of 1-Ln are invisible, color adjustable, and stabilized, which may greatly improve their anticounterfeiting applications.

Label-free and highly selective MOFs-based dopamine detection in urine of Parkinson’s patients

The amount of dopamine (DA) in the body is closely related to the occurrence and development of Parkinson's disease. However, DA detection in real body fluids is still challenging. Here, we developed a high-selectivity and high-sensitivity label-free lanthanide metal organic frameworks (MOFs) to monitor DA in urine samples from Parkinson’s patients. The fluorescent MOF Eu-α-cyclodextrin (CD), prepared by biomineralization under mild conditions, exhibited DA concentration-dependent fluorescence intensity via host–guest complexation. Furthermore, molecular dynamics (MD) simulation analyses quantitatively dissect thermodynamic interactions of cyclodextrin and guest molecules, which systematically reveals the specific recognition mechanism of cyclodextrin and dopamine molecules. A good response for DA in the range of 10-9 to 10-4 M and a limit of detection (LOD) of 0.65 nM were obtained, consistent with the detection range of DA in a variety of biological fluids. Because of the good anti-interference properties of this complex, visual test strips were prepared by the in-situ growth of Eu-αCD nanoparticles on a nitrocellulose (NC) membrane at room temperature, owing to the protein absorbability of NC membranes. The resultant test strips possess the potential for semiquantitative detection of DA by the naked eye. Moreover, we applied Eu-αCD nanoparticles to analyze clinical urine samples from Parkinson's patients, and achieved a low relative error compared with those of commercial HPLC methods. Our work offers an efficient strategy for visual and on-site detection of DA in the clinic, which can assist in early diagnosis of Parkinson's disease.

Portable visual assay of Bacillus anthracis biomarker based on ligand-functionalized dual-emission lanthanide metal-organic frameworks and smartphone-integrated mini-device

A single-functionalized ligand single-Ln3+ based dual-emission Ln-MOF fluorescent sensor was established for portable and visual dipicolinic acid (DPA, Bacillus anthracis biomarker) detection. First, a theory calculation-based prediction model was developed for designing single-functionalized ligand single-Ln3+ dual-emission Ln-MOFs. The model consisted of three calculation modules: intramolecular hydrogen bonds, excited state energy levels, and coordination stability with Ln3+ of ligands. Tb3+ and Eu3+ were selected as metal luminescence centers, PTA-X (PTA: p-phthalic acid, X = NH2, CH3, H, OH) with different functional groups as one-step functionalization ligands, and the luminescent feature of four Tb-MOFs and four Eu-MOFs was predicted with the model. Coupled with prediction results and experimental verification results, Tb-PTA-OH was rapidly determined to be the sole dual-emission Ln-MOF. Then, Tb-PTA-OH was applied to DPA detection by ratiometric fluorescence, and an ultra-low limit of detection (13.4 nM) was obtained, which is much lower than the lowest anthrax infectious dose (60 μM). A portable visual assay method based on paper-microchip and smartphone integrated mini-device was further established (limit of qualification 0.48 μM). A new sensing mechanism and a "triple gates" selectivity mechanism to DPA were proposed. This work reveals guidelines for material design and mini-device customization in detecting hazardous substances.

Confined and synergistic effects between protonated amines and gases in the frameworks of lanthanum 1,3-propanediaminetetraacetates

Lanthanum microporous frameworks (Hdma) 2n [La 2 (1,3-pdta) 2 (H 2 O) 2 ] n ·5nH 2 O ( 1 , dma = dimethylamine, 1,3-pdta = 1,3-propanediaminetetraacetic acid) and (H 2 pn) n [La 2 (1,3-pdta) 2 (H 2 O) 2 ] n ·5nH 2 O ( 2 , pn = 1,3-propanediamine) with double channels have been template-synthesized by protonated dimethylamines and 1,3-propanediamines, respectively. While bulky product (H 2 bn)[La 2 (1,3-pdta) 2 (H 2 O) 4 ]·10H 2 O ( 3 , bn = 1,4-butanediamine) is isolated as a dinuclear species with tetrahydrates, whose main anion can be served as a precursor for 1 and 2 . Materials 1 – 3 are able to maintain their chemical and thermal stabilities to 200 °C based on TG and XRD analyses. Gas adsorptions demonstrate that MOFs 1 and 2 are amicable for O 2 and CO 2 , while no adsorption has been observed for CH 4 , N 2 or H 2 respectively. The amounts of encapsulated CO 2 in hydrophobic pores are dependent on the alkalinities of the diamines in the next confined hydrophilic holes, showing synergistic effects between double channels. For protonated dimethylamines and 1,3-propanediamines in 1 and 2 , obvious downfield shifts have been found by solid-state 13 C NMR spectroscopies, along with clear red shifts in FT-IR spectra compared with free species. Moreover, captured CO 2 inside 1 can be quantized by NMR measurements and IR spectroscopies under ambient condition. These all reflect the confinement effects of nano-environments. • Synergistic and confined effects in lanthanide MOFs with gases are quantized and discussed. • An interesting precursor is obtained when the synthetic template is 1,4-butanediamine. • CO 2 uptake and conversion in the hydrophobic channels can also be spectroscopic characterized.

Rapid detection of lamotrigine by a water stable fluorescent lanthanide metal–organic framework sensor

Lamotrigine (LTG) is an antiepileptic drug, but excessive use of LTG can cause life-threatening skin rashes. Herein, a new type of Tb-MOF with two emitting centers for LTG detection was designed and synthesized. The unique crystal structure is derived from a hexacarboxylic acid ligand and lanthanide Tb3+ ion. The application of ratiometric fluorescence sensing improves the accuracy for detecting LTG. The Tb-MOF also displays excellent sensitivity with fast response within 40 s, low detection limit of 1.66 μM and high recyclability. This research provides important significance for using lanthanide metal–organic framework (Ln-MOF) as the platform for fluorescent sensing.

A multiemissive lanthanide metal-organic framework for selective detection of l-tryptophan

Amino acids are one of the essential components of the human body. Lack of amino acids can lead to poor concentration, fat gain, memory loss and so on. Herein, a novel lanthanide metal-organic framework (Sm-MOF) was prepared for self-calibrated luminescent recognition of amino acids. Each amino acid is significantly correlated to a unique combination of the two emission intensity ratios of the characteristic peaks of the ligand to Sm3+ ion, making two-dimensional fingerprint recognition possible. It is worth mentioning that the new self-calibrated sensor can detect l-tryptophan (Trp) with excellent sensitivity and selectivity, rapid response (<32 s) and low detection limit (1.32 μM). The luminescence mechanism mainly derived from the energy transfer between Trp and ligand, Sm3+ ions. Furthermore, satisfactory recoveries of 95–107% were obtained in plasma, suggesting the potential application of Sm-MOF in the detection of Trp in plasma.

2D paddle wheel lanthanide metal-organic framework: Synthesis, structure and exploration of catalytic N-arylation reaction

Novel lanthanide based two-dimensional metal–organic framework (MOF) compound [Dy(NDC)(NO3)(DMA)2]n (1) [H2NDC = 2,6-naphthalenedicarboxylic acid and DMA = N,N-dimethylacetamide] has been synthesized through solvothermal route and structurally characterized. Structural analysis reveals that compound is crystallized in the orthorhombic crystal system with space group Pbca. MOF features “paddle-wheel” (PW) core building units which are constructed via carboxylato oxygen coordinated to lanthanide atoms. Remaining coordination sites of the octa-coordinated metal center are occupied by oxygen atoms of DMA and NO3− ions. Paddle-wheel cores of 1 are interconnected to each other to give rise to layered network structure. The morphology of the MOFs as well as different types of weak interactions possessed by the framework have been assessed using Hirshfeld surface analysis and fingerprint plots have been drawn to understand various interactions. Notably, compound 1 can efficiently catalyze the N-arylation reaction heterogeneously.

Lanthanide metal−organic frameworks based on planar π-conjugated ligands for white light emission, temperature and chemical sensing

Two stable three-dimensional lanthanide metal-organic frameworks, Ln-MOFs of [M2O(BDCPO)1.5(H2O)7]·2H2O (Eu for CUST-621, Tb for CUST-622) are successfully constructed using π-electron riched ligand N,N′-bis(2,4-dicarboxyphenyl)-oxalamide (H6BDCPO) and Eu and Tb metal ions under solvothermal conditions. The appropriate chromophores in ligands can effectively sensitize Ln3+ ions, resulting in luminescence emission. The crystal structures are determined by single X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, infrared spectrophotometer and luminescence measurements. Triple emission centers are successfully designed and realized the solid-state white light (SSWL) performance, whose CIE coordinates are close to ideal white light (0.32, 0.33). Furthermore, the temperature sensitivity tests indicate that the two materials can be used to sense the temperature in the range of 303–423 K with remarkable color change. The maximum sensitivity are 6.86% K−1 and 7.73% K−1 at 423 K, respectively. Moreover, CUST-621 and CUST-622 can be used as multi-responsive luminescence sensors to Fe3+ and Cr2O72−, with high sensitivity, long-time stability and remarkable selectivity with resistance to interference from other ions. This work supply a general way to construct Ln-MOFs materials for multifunctional luminescence properties for sensing fields.