Ln(III)-Functionalized Metal-Organic Frameworks Hybrid System: Luminescence Properties and Sensor for trans, trans-Muconic Acid as a Biomarker of Benzene

A gas-selective Zn-MOF exhibits selective sensing of Fe3+ ions by doping with Tb3

Here, a new Zn2+ metal organic framework, {[Me2NH2][Zn2(L)(DTZ)]·2DMF·3H2O}n (Zn-MOF), has been synthesized with low-symmetric carboxylic acid ligand 2,6 bis(2',5'-dicarboxyphenyl)pyridine (H4L) as the main ligand and 3,5-diamino-1,2,4-riazole (DTZ) containing an electron-rich N atom as an auxiliary ligand. Because of its high structural stability and adsorption properties, it can be used to efficiently separate CO2/CH4 and C2H2/CH4. In addition, Tb@Zn-MOF was obtained by doping with Tb3+ to partially replace Zn2+. A study of its luminescence sensing performance demonstrated that Tb@Zn-MOF showed intense luminescence properties and can be used for the directional detection of Fe3+ in aqueous solution. Furthermore, PXRD analysis, UV-vis spectroscopy and X-ray photoelectron spectroscopy (XPS) were also used to study possible luminescence sensing mechanisms. The recognition mechanism for Fe3+ ions is believed to be caused by electron transfer.

Visual ratiometric fluorescence sensing of L-lactate in sweat by Eu-MOF and the design of logic devices

Using 1, 4-H₂NDC as ligand and Eu as the center metal, the lanthanide MOF Eu-NDC was synthesized by hydrothermal method. The material showed a fast ratiometric response to L-lactate, and the fluorescence of the material varied from red to blue with the growth of lactate concentration, which can be used as a fluorescent sensor for L-lactate in sweat. The sensor exhibited good fluorescence stability to interfering components in human sweat and good detection limits for lactate in artificial sweat. Based on this, a visualized molecular logic gate that can monitor sweat lactate levels was constructed, and the material's characteristic of showing different colors with lactate concentration changes was used to indicate possible hypoxia during exercise, opening a new path for combining sweat lactate monitoring with smart molecular devices.

An Overview of the Design of Metal-Organic Frameworks-Based Fluorescent Chemosensors and Biosensors

Taking advantage of high porosity, large surface area, tunable nanostructures and ease of functionalization, metal-organic frameworks (MOFs) have been popularly applied in different fields, including adsorption and separation, heterogeneous catalysis, drug delivery, light harvesting, and chemical/biological sensing. The abundant active sites for specific recognition and adjustable optical and electrical characteristics allow for the design of various sensing platforms with MOFs as promising candidates. In this review, we systematically introduce the recent advancements of MOFs-based fluorescent chemosensors and biosensors, mainly focusing on the sensing mechanisms and analytes, including inorganic ions, small organic molecules and biomarkers (e.g., small biomolecules, nucleic acids, proteins, enzymes, and tumor cells). This review may provide valuable references for the development of novel MOFs-based sensing platforms to meet the requirements of environment monitoring and clinical diagnosis.

Design and Multiple Applications of Mixed-Ligand Metal-Organic Frameworks with Dual Emission

Herein, we revealed the factors that affect the emission in mixed-ligand metal-organic frameworks (MOFs) with the combination of terephthalic acid (BDC), 2-aminoterephthalic acid (BDC-NH₂), and 2,5-dihydroxylterephthalic acid [BDC-(OH)₂] as models. The -NH₂ and -(OH)₂ groups change the π-conjugation and luminescence behaviors than BDC, so the ligands show different optical behaviors. The Zn²⁺ ion with a 3d¹⁰ full electronic structure shows little effect on the emission of the ligand and is selected as the metal node. We found that the emission of BDC is weak and incompatible to that of BDC-NH₂, so only the emission of BDC-NH₂ was observed in the BDC/BDC-NH₂-MOF. Crosstalk occurs between the emissions from BDC and BDC-(OH)₂ for the single emission from BDC/BDC-(OH)₂-MOFs, even different ratios are selected. The MOFs prepared with BDC-NH₂ and BDC-(OH)₂ show dual emission at 450 and 550 nm, while the relative intensity was easily tuned with the ligand ratio and excitation wavelength. Thus, abundant optical behaviors and extensive applications were realized, including but not limited to (1) dual emission from single MOFs, (2) tunable color from blue to yellow with the excitation from 290 to 370 nm for information encryption and decryption, (3) white emission obtained under an excitation of 330 nm, and (4) response of -NH₂ groups to HCHO and Fe³⁺ ions for ratiometric fluorescence sensing and visual detection. This work revealed the factors that affect the emission in mixed-ligand MOFs, studied their optical behaviors, and realized different applications with single MOFs.

Unearth the Luminescence Potential of Metal-Organic Frameworks: Adopting a Feasible Strategy to Fabricate One Ratiometric Fluorescence Sensor for Monitoring Both 1-Hydroxypyrene and Cu2

In this work, a novel luminescent hybrid material with double emission centers (Eu(TTA)_0.2@9-1-UMOF) is successfully prepared, adopting a feasible design strategy. Initially, the second ligand 1,2,4-benzenetricarboxylic acid (H₃BTC) is encapsulated based on a solid solution approach, which effectively improves the ligand-based emission intensity of the original LMOF and provides functional sites for introducing the second luminescent center; then, Eu³⁺ as the red emission source is loaded into the frameworks through a coordination post-synthetic modification method; finally, to balance the emission intensity at 613 nm (Eu³⁺) and 465 nm (1,4-naphthalenedicarboxylic acid (H₂NDC)), 2-thenoyltrifluoroacetone (TTA) as a powerful antenna is introduced. Given the outstanding luminescence properties and structural stability of Eu(TTA)_0.2@9-1-UMOF, it is further developed as a ratiometric sensor for detecting 1-hydroxypyrene (1-HP, the biomarker of polycyclic aromatic hydrocarbons (PAHs)) and Cu²⁺, which promotes the pre-diagnosis of human health. Notably, Eu(TTA)_0.2@9-1-UMOF exhibits excellent selective recognition ability for both 1-HP and Cu²⁺ with high sensitivity (LOD = 4.06 × 10^-6 mg/mL, 3.85 × 10^-7 mol/L, respectively) and fast response speed. In addition, Eu(TTA)_0.2@9-1-UMOF as a fluorescent probe shows great potential for the determination of 1-HP and Cu²⁺ in actual samples. More importantly, this work widens the road for the development of dual/multiple LMOF-based sensors for analytical applications.

The postsynthetic renaissance of luminescent lanthanide ions on crystalline porous organic framework materials

A series of crystalline porous organic framework materials (CPOFs), such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and hydrogen bonded organic frameworks (HOFs) have received extensive attentions due to...

Magnetic molecularly imprinted polymers for extraction of S-phenylmercapturic acid from urine samples followed by high-performance liquid chromatography

In this study, magnetic molecularly imprinted polymers (MMIPs) were prepared and used as sorbents for extraction of S-phenylmercapturic acid (S-PMA) from urine samples, followed by high-performance liquid chromatography ultraviolet-visible (HPLC-UV/Vis) analysis. The MMIPs were synthesized by the copolymerization reaction of (phenylthio) acetic acid (template molecule), methacrylic acid (functional monomers) and ethylene glycol dimethacrylate (cross-linkers). The morphology, structure property and surface groups of the prepared MMIPs were characterized by scan electron microscopy, transmission electron microscopy, infrared spectroscopy, X-ray diffraction pattern, thermogravimetric analyses, Brunauer-Emmett-Teller and vibrating sample magnetometer. The selectivity of the MMIPs was investigated in the presence of interferents. Various parameters affecting the S-PMA extraction efficiency were investigated, including MMIPs amount, pH, sample volume, desorption solvent, as well as extraction and desorption time. The obtained optimal parameters were as follows: MMIPs amount (20 mg), pH (3.0), sample volume (5 mL), desorption solvent (methanol/acetic acid [9/1, v/v]), extraction time (30 minutes) and desorption time (2 minutes). The method was validated according to the Food and Drug Administration Guidance for Industry on Bioanalytical Method Validation. The calibration curve for the analyte was linear in the concentration range of 0.030-1.0 mg/L (r = 0.9995). The LOD and LOQ of the method were 0.0080 and 0.0267 mg/L, respectively. The enrichment factor of the MMIPs was 5. The relative standard deviations of intra- and inter-day tests were in the range of 3.8-5.1% and 3.9-6.3%, respectively. The recoveries at three different concentrations of 0.10, 0.50 and 0.80 mg/L ranged between 95.2% and 98.6%. In addition, the MMIPs could be reused for at least eight times. The proposed method was successfully applied to the determination of S-PMA in urine samples. In addition, this developed method could be used as a tool in the early screening and clinical diagnosis of benzene intoxication.

Ultrastable Tb-Organic Framework as a Selective Sensor of Phenylglyoxylic Acid in Urine

Industrial pollution and harmful chemicals seriously affect environment and human health. Styrene is a common air toxicant with widespread exposure sources, including smoking, automobile exhaust, and plastic pollutants. Phenylglyoxylic acid (PGA) is a typical biomarker for exposed styrene. Therefore, it is crucial to quickly identify and quantitatively detect PGA. Herein, an ultrastable terbium metal-organic framework (Tb-MOF 1) was developed, and the luminescence film (1/PLA) consisting of polylactic acid (PLA) and 1 was fabricated as a sensor for rapid detection of PGA. The sensor possesses the advantages of efficient detection [limit of detection (LOD) is 1.05 × 10^-4 mg/mL] and rapid response speed (less than 10 s) for PGA in urine. Furthermore, this sensor exhibits high stability, outstanding anti-interference ability, and excellent recyclability. Based on this film technology, a paper-based probe was then developed for portable and convenient detection. The probe could easily distinguish different concentrations of PGA under the naked eye toward practical sensing applications. Meanwhile, photoinduced electron transfer was demonstrated to be responsible for the luminescence sensing. Hence, this study indicates that Tb-MOF is a promising material to detect PGA for evaluating the effect of styrene on the body.

A Stable Cd(II)-Based Metal-Organic Framework: Synthesis, Structure, and Its Eu3+ Functionalization for Ratiometric Sensing on the Biomarker 2-(2-Methoxyethoxy) Acetic Acid

A novel two-dimensional Cd-based metal-organic framework (MOF), [Cd(pddb)H₂O]_n (Cd-MOF), has been hydrothermally synthesized using the V-shaped ligand 4,4'-(pyridine-2,6-diyl)-dibenzoic acid (H₂pddb) and structurally characterized. The framework exhibits fascinating one-dimensional in-plane channels functionalized with active pyridine-N sites. The as-synthesized Cd-MOF exhibits excellent water and chemical stability. Furthermore, a simple and nondestructive coordinated postsynthetic modification method has been applied to Cd-MOF to obtain a class of MOF hybrids functionalized by lanthanide ions. More interestingly, Eu³⁺@Cd-MOF can act as a dual-emissive ratiometric fluorescent probe for 2-(2-methoxyethoxy) acetic acid (MEAA), a metabolite of 2-(2-methoxyethoxy) ethanol, which could result in DNA damage and teratogenic and developmental toxicity. During the sensing process, the fluorescence sensor exhibits notable water tolerance, reusability, and a low detection limit (8.5 μg mL^-1). In addition, the chemical substances in human urine and serum do not interfere with the fluorescence quenching process, which makes it possible for the fluorescent probe to be applied in the detection of MEAA in human urine and serum systems. The possible sensing mechanism is also studied and discussed in detail.

A new strategy to fabricate multifunctional luminescent MOFs, extending their application range from pH sensing to amino acid information coding

Herein, we propose a new strategy for designing new types of wide range pH-sensitive metal-organic frameworks (MOFs) with double luminescent centers on UiO-66-2OH. The UiO-66-2OH has a ligands-based emission at 530 nm. To introduce another luminescent center, PMA (1,2,4,5-benzenetetracarboxylic acid), as the functional site, is used to substitute the initial ligand, BDC-2OH (2,5-dihydroxyterephthalic acid), of UiO-66-2OH. Eu³⁺ ions, another luminescent center at 613 nm, are coordinated to the free carboxyl group on PMA. Finally, TTA (2-Thenoyltrifluoroacetone) is coordinated with Eu³⁺ ions to balance the emission at 613 nm (Eu³⁺ ions) and 530 nm (BDC-2OH). For the sake of both strong emissions, we explored the loading levels of PMA. The optimized structure is Eu(TTA)@MUM5 ("MUM" is the abbreviation of "Mixed ligand UiO-66-2OH MOFs" and "5" represents the molar percentage of PMA is 50%), which exhibits strong emission at 530 nm (alkaline solution) and 613 nm (neutral solution). Remarkably, the synthesized material has an exponential relationship (R² = 0.9973) over the pH range of 1.87 to 9.65 and a linear relationship (R² = 0.9987) when pH = 11.01-13.35. Further experiments have proved that Eu(TTA)@MUM5 could distinguish different amino acids. Based on that, we build an information transferring circle with two coding modes on Eu(TTA)@MUM5 using aseptic acid and arginine as coding factors.

A bi-functionalized metal-organic framework based on N-methylation and Eu3+ post-synthetic modification for highly sensitive detection of 4-Aminophenol (4-AP), a biomarker for aniline in urine

4-Aminophenol (4-AP), which is a biomarker of aniline and represents the internal dose of aniline exposure in the human body, has attracted much attention for its detection in recent years. In this work, a bi-functionalized luminescent metal-organic framework (MOF), Eu@MOF-253-CH_3, is designed and prepared through encapsulating the methyl groups and the Eu³⁺ cations into MOF-253 based on post-synthetic modification strategy. This study shows that the bi-functionalized Eu@MOF-253-CH₃ can specifically recognize 4-AP upon luminescence quenching, while refraining from the interference of other coexisting species in urine. The Eu@MOF-253-CH₃ hybrid as a 4-AP sensor also displays excellent performances including high water tolerance, good pH-independent stability, fast response, great selectivity and elevated sensitivity (0.5 μg mL^-1) attributed to N-viologenized ligand. These results suggest the bi-functionalized Eu@MOF-253-CH₃ can act as a promising sensor to practically monitor 4-AP's concentrations in human urine system, and then to realize the screening and pre-diagnosis of human health. Moreover, the possible sensing mechanisms are further explored at length.

Covalent-coordination tandem functionalization of a metal-organic framework (UiO-66) as a hybrid probe for luminescence detection of trans,trans-muconic acid as a biomarker of benzene and Fe3

By means of post-synthetic treatment on the UiO-66 derivative with -SO3H, a novel luminescent hybrid material named Tb3+@UiO-66-SO3H has been prepared simply and efficiently. Given its wonderful luminescence properties like intense green emission, a long lifetime, a robust structure and photostability, it is further developed as a fluorescent probe for the sensing of trans,trans-muconic acid (tt-MA, a biomarker of benzene) and Fe3+, which are closely related to human health. Notably, Tb3+@UiO-66-SO3H shows an outstanding recognition ability for Fe3+ among common cations with a low detection limit (0.11 μM, 0.006 ppm). More importantly, Tb3+@UiO-66-SO3H can realize highly sensitive and selective detection of tt-MA (detection limit, 0.58 μM, 0.083 ppm). Besides, this rapid response probe is facilely prepared, non-toxic and reusable, showing the potential of Tb3+@UiO-66-SO3H in the practical monitoring of tt-MA and Fe3+.

Novel Multifunctional Samarium-Organic Framework for Fluorescence Sensing of Ag+, MnO4 -, and Cimetidine and Electrochemical Sensing of o-Nitrophenol in Aqueous Solutions

A novel Sm-metal-organic framework (MOF) sensor with the molecular formula Sm8(HDBA)6·H2O has been prepared based on a penta-carboxyl organic ligand (H5DBA = 3,5-di(2',4'-dicarboxylphenyl)benzoic acid) and samarium nitrate under solvothermal conditions. Sm-MOF is characterized by single-crystal X-ray diffraction analysis, elemental analysis, thermogravimetric analysis, and powder X-ray diffraction analysis. Structural analysis shows that the dimer metal units are alternately connected to form a one-dimensional chain, and this chain is connected by the bridging carboxyl oxygen of the ligand H5DBA to form a two-dimensional double-layer plane, which then expands into a three-dimensional microporous framework. Fluorescence detection studies show that Sm-MOF can detect Ag+ ions, MnO4 - anions, and cimetidine tablets with high sensitivity and selectivity and can also be used to electrochemically detect o-nitrophenol in water. High-sensitivity detection capability of the Sm-MOF can enrich the application of samarium complexes in multifunctional sensors.

Multi-emission metal-organic framework composites for multicomponent ratiometric fluorescence sensing: recent developments and future challenges

Ratiometric fluorescence sensors that are achieved via the ratiometric fluorescence intensity changes of emission peaks based on multi-emission fluorescence probes show a huge advantage. However, the preparation of these multi-emission fluorescence probes is a key challenge, as it is related to having more fluorescence groups with the same excitation but different emission wavelengths, and their assembly is not a simple mixing process. More fluorescent groups or molecules can be assembled into the multi-emission fluorescence probe by covalent bonds and coordination interactions, or by loading in metal-organic frameworks (MOFs). MOFs are excellent candidates for constructing complexes with the capability of multicomponent ratiometric fluorescence sensing, but there are some problems that need to be considered. For example, not all fluorophores can be stably loaded in the MOFs' pores, usually due to the size, surface charge and intrinsic properties of the fluorophore. In turn, it is also related to the structure of the MOF, metal nodes, and properties of the organic ligands. This review first introduces the advantages of the MOF-based multi-component fluorescence sensors, and then discusses the synthesis, classification and application of fluorescent MOFs or MOF composites for multi-component ratiometric fluorescence detection. Particular emphasis is focused on the potential, types and characteristics for sensing and biological applications, and the main challenges and limitations are further explored. This review might be helpful for those researchers interested in the application of multi-component ratiometric fluorescence sensing based on fluorescent MOFs or MOF composites.

Luminescence response mode and chemical sensing mechanism for lanthanide-functionalized metal–organic framework hybrids

This comprehensive review systematically summarizes the luminescence response mode and chemical sensing mechanism for lanthanide-functionalized MOF hybrids (abbreviated as LnFMOFH).

The construction of a novel luminescent lanthanide framework for the selective sensing of Cu2+ and 4-nitrophenol in water

Two water stable Ln-MOFs that take the (4,4,4)-connected nets with unprecedented topology symbol of {4²·6·8³}₂{4²·6²·8²}{4²·8⁴} were developed for sensing Cu²⁺ and 4-NP in aqueous media with high selectivity and sensitivity.

Terbium-based metal-organic frameworks: highly selective and fast respond sensor for styrene detection and construction of molecular logic gate

Volatile organic compounds (VOCs) are extremely harmful to the human body and environment, thus it is greatly meaningful and urgent to detect VOCs. In this work, terbium-based metal-organic frameworks (Tb-MOFs) have been prepared successfully via a facile and efficient route. These well-constructed Tb-MOFs architectures exhibit characteristic green emission of Tb³⁺ ion upon excitation of UV light. It is noteworthy that the Tb-MOFs can act as a convenient and efficient luminescent sensor for VOCs. Especially, the Tb-MOFs displayed high selectivity and superior sensitivity towards the sensing of styrene solution and vapor through fluorescence quenching mechanism. The Tb-MOFs can realize fast detection for styrene vapor with a response time of 30 s. The mechanism of fluorescence quenching of Tb-MOFs induced by styrene was also discussed. More importantly, we have designed a logic gate operation with the combination of the sensor for the intelligent detection of styrene. This developed type of lanthanide luminescent metal-organic frameworks (Ln-MOFs) based on the combination of fluorescence sensor and logic gate has a great application prospect in the detection of VOCs in daily life.

Dual-emission CdTe quantum dot@ZIF-365 ratiometric fluorescent sensor and application for highly sensitive detection of l-histidine and Cu2

l-histidine acts as a semi-essential amino acid, which is medically used in the treatment of gastric ulcer, anemia, allergies. However, the overuse of l-histidine will result in terrible damage to heart disease, slow growth of animals and water pollution in the environment. In addition, Cu²⁺ pollution is common environmental pollution in the industry. It has the characteristics of high accumulation, migration, and persistence. Given this, through the post-synthesis strategy, CdTe quantum dots (QDs) were the first time to introduce into zeolitic imidazolate framework-ZIF-365 to synthesis dual-emission hybrid material CdTe@ZIF-365 with high quantum yield. TEM mappings and N₂ absorption tests are applied to confirm the combination mode between CdTe quantum dots and ZIF-365. It should be noted that CdTe@ZIF-365 can be successfully utilized as a bi-functional ratiometric sensor for highly sensitive discrimination of l-histidine and Cu²⁺. Firstly, CdTe@ZIF-365 is applied to a fluorescent ratiometric sensor for Cu²⁺ with high sensitivity (the K_sv value is 2.7417✕10⁷ [M^-1]) and selectivity in the mixed cation ions' solution. On the other hand, CdTe@ZIF-365 also behaved as the first example for an excellent ratiometric fluorescent senor for l-histidine with high sensitivity (the K_sv value is 6.0507✕10⁸ [M^-1]) and selectivity in the mixed amino acids' solutions.

Ln-CPs constructed from unsymmetrical tetracarboxylic acid ligand: Tunable white-light emission and highly sensitive detection of CrO42-, Cr2O72-, MnO4- in water

A series of isostructural lanthanide coordination polymers (Ln-CPs), [Ln(Hbptc)(H₂O)₄]·H₂O [Ln = Er (1), Pr (2), Dy (3), Sm (4), Gd (5), Nd (6) and Tb(7); H₄bptc = 2,3,3',4'-biphenyl tetracarboxylic acid] have been isolated based on an unsymmetrical tetracarboxylic acid. Single-crystal X-ray diffraction analysis reveals that all CPs featured a two dimensional (2D) layer with (6, 6, 6)-connected 6³ topology. Luminescent spectra demonstrate that CPs 1-7 exhibit impressive UV-visible luminescence in the solid state at room temperature. More significantly, a single-component white-light material with International Commission on Illumination (CIE) coordinates of (0.335, 0.334) for 4 (Sm-CP), very closing to the pure white-light of (0.333, 0.333) was obtained by finely tuning of the excitation wavelength. In addition, the luminescent detection for anions of 7 is investigated. Fluorescence measurements show that 7 can detect oxoanion pollutants Cr₂O₇^2-, CrO₄^2-, and MnO₄^- anions in aqueous solutions with high selectivity and sensitivity, which suggests that the Tb-CP is a promising functional luminescence probe for toxic oxoanions. The possible mechanisms of the quenching effect were also discussed in detail.

Lanthanide functionalized MOF thin films as effective luminescent materials and chemical sensors for ammonia

A series of Lanthanide functionalized MOF thin films on Al₂O₃ are fabricated using designed linkers, whose unique luminescence performance is shown to be a sensitive probe toward ammonia.

2D lanthanide coordination polymers constructed from a semi-rigid tricarboxylic acid ligand: crystal structure, luminescence sensing and color tuning

Three lanthanide polymers {[Ln(TMCA)(DEF)(H₂O)]·(CH₃CN)}_n (Ln = Eu 1; Tb 2; Gd 3; H₃TMCA = 4′,4′,4′-[(trimethylamino)]-tris[(1,1′-biphenyl)-2-carboxylic acid]) were synthesized under solvothermal conditions.

Design and properties of multiple-emitter luminescent metal–organic frameworks

This feature article reviews the design strategies by which multiple different emission sources could be combined for creating multi-emitter luminescent metal–organic frameworks (LMOFs).

A highly sensitive and selective "turn-on" fluorescent probe for detection of fleroxacin in human serum and urine based on a lanthanide functionalized metal-organic framework

Cation exchange, a facile and non-destructive post-synthetic modification method, is applied to [(Me)₄N]₂[Pb₆K₆(m-BDC)₉(OH)₂]·H₂O (1) (1,3-H₂BDC = 1,3-benzenedicarboxylic acid) to prepare a series of lanthanide functionalized metal-organic frameworks. The fluorescence properties of Ln³⁺@1 (Ln = Eu, Tb, Sm and Dy) are investigated. The results demonstrate that the framework of 1 is capable of sensitizing both Eu³⁺ and Tb³⁺ ions effectively. Remarkably, the rapid and stable fluorescence sensitization of Eu³⁺@1 can be observed in the presence of fleroxacin in aqueous solution, indicating that the hybrid system can be designed as a highly sensitive and selective probe for fleroxacin. As a novel "turn-on" fluorescent probe, Eu³⁺@1 is regarded as a promising candidate for applications in clinical diagnosis, due to its merits of high antidisturbance, chemical stability and a low detection limit (43.91 ng mL^-1). In this paper, the practical application of luminescent Eu³⁺@1 is highlighted, and its possible sensing mechanism is also described.

Diagnosis of penicillin allergy: a MOFs-based composite hydrogel for detecting β-lactamase in serum

A MOFs-based composite hydrogel 1@SA is presented for the diagnosis of penicillin anaphylaxis. This composite hydrogel reflects the enzymatic hydrolysis profiles of penicillin via β-lactamase. The determination of β-lactamase by this hydrogel was achieved through an “ON–OFF–OFF–ON” fluorescence trigger pattern. The potency of 1@SA was further demonstrated for its selectivity, sensitivity and convenient visual detection.

3D LnIII-MOFs: displaying slow magnetic relaxation and highly sensitive luminescence sensing of alkylamines

Six isomorphous Ln-based MOFs with 3D structures have been synthesized under solvothermal conditions. Dy-MOF (5) shows slow magnetic relaxation behaviors. Eu-MOF (3) can serve as a recyclable sensor towards alkylamines in water systems.

A heterometallic sodium(i)–europium(iii)-organic layer exhibiting dual-responsive luminescent sensing for nitrofuran antibiotics, Cr2O72− and MnO4− anions

A red-emitting layer constructed from {Eu₂Na(CH₃COO)₂} chains and 4,4′-(pyridine-2,6-diyl)dibenzolate linkers exhibits luminescent discriminations for three nitrofuran antibiotics and toxic Cr₂O₇²⁻ and MnO₄⁻ anions.

Stable Tb(III)-Based Metal-Organic Framework: Structure, Photoluminescence, and Chemical Sensing of 2-Thiazolidinethione-4-carboxylic Acid as a Biomarker of CS2

A novel three-dimensional microporous framework, [Tb(pddb)phen(ox)_0.5] _n (Tb-MOF), was synthesized hydrothermally with V-shaped 4,4'-(pyridine-2,6-diyl)dibenzoic acid (H₂pddb), oxalate (ox), and 1,10-phenanthroline (phen). The framework of Tb-MOF features one-dimensional channels functionalized with pyridine-N Lewis base groups and the absence of coordinated and lattice water molecules in the structure. The Tb-MOF exhibits high thermostability (up to 385 °C) and chemical stability in a wide pH range (4-11) and common organic solvents as well as boiling water. The luminescence investigations of the Tb-MOF in common solvents, water with different pH values, and inorganic ions were performed. Results show that the Tb-MOF has high luminescence stability and the ability to probe Fe³⁺ ions. Significantly, the Tb-MOF with particularly high water stability can be first developed as a highly selective and sensitive luminescent sensor for the biomarker 2-thiazolidinethione-4-carboxylic acid (TTCA) via fluorescence quenching. The low detection limit (1 ppm), reusability, and high antidisturbance together make the Tb-MOF become a promising sensor for the practical detection of TTCA in urine systems, and for the first time realize the detection of urinary TTCA through fluorescence spectrometry based on an Ln-MOF sensor.

Novel "Turn-On" Fluorescent Probe for Highly Selectively Sensing Fluoride in Aqueous Solution Based on Tb3+-Functionalized Metal-Organic Frameworks

A Zr-based metal-organic framework (Zr-MOF) which has free carbonyl groups is synthesized successfully through mix-ligand strategy. Subsequently, Tb³⁺ is encapsulated into a Zr-MOF by postcoordinated modification. The Tb³⁺@Zr-MOF exhibits the characteristic emission of Tb³⁺ because of efficient sensitization through antenna effects. The Tb³⁺@Zr-MOF is further developed as a novel "turn-on" fluorescent probe to detect fluoride ions in aqueous solution. The results show that Tb³⁺@Zr-MOF exhibits excellent selectivity, high stability, low detection limits, and good anti-interference for sensitizing fluoride ions. In addition, the possible sensing mechanism that the induced luminescence properties may be attributed to Lewis acid-base interactions is discussed.