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

Dual Stimulus Responsive GO-Modified Tb-MOF toward a Smart Coating for Corrosion Detection

Smart-sensing coatings that exhibit multistimulus response, rapid indication, and reusability are in urgent need to effectively enhance the practicability of coatings while accurately detecting metal corrosion. In this work, a reusable corrosion self-reporting coating with multiple pH and Fe3+ stimulus responses was first constructed by the integration of a composite fluorescent probe into the resin matrix. This composite sensor was constructed by combining a lanthanide metal-organic framework (Ln-MOF) based on terbium and trimeric acid (H3BTC) with graphene oxide (GO) nanosheets (GO@Tb-BTC). The incorporation of GO formed a sea-urchin-like structure, thereby increasing the specific surface area and active sites of the probe. The coatings were characterized by using electrochemical impedance spectroscopy (EIS), visual observation, and fluorescence spectrophotometry. The surface morphology, wettability, and adhesion of the coating samples were analyzed using SEM, XPS, hydrostatic contact angle test, and an adhesion test. EIS measurements in 3.5 wt % NaCl solution for 72 h demonstrated the superior corrosion protection performance of the 0.3 wt %/GO@Tb-BTC/WEP coating compared to blank coating, with the charge-transfer resistance reaching 4.33 × 107 Ω·cm2, which was 9.5 times higher than that of the pure coating. The bright green fluorescence of GO@Tb-BTC/WEP coating exhibited a turn-off response when there was an excess of OH-/H+, but it demonstrated a reversible turn-on fluorescence when the ambient pH returned to neutral. Furthermore, such Fe3+-triggered fluorescence quenching responded to concentrations as low as 1 × 10-6 M. The fluorescence quenching rate of both intact and damaged coatings surpassed that of visual and EIS detection methods. Significantly, the fluorescence in scratches was effectively quenched within 25 min using 0.3 wt %/GO@Tb-BTC/WPU coating for visual observation. GO@Tb-BTC demonstrated exceptional corrosion self-reporting capabilities in both epoxy and polyurethane systems, making it a versatile option beyond single-coating applications.

Stretchable Tb-Tb Distance Regulates the Piezofluorochromic Behavior of Chiral Tb(III)-MOF upon Compression

Luminescent chiral Tb-MOF microcrystals with the Tb2(COO)4 subunit indicated strong green mechano-luminescence under compression. Furthermore, piezofluorochromic behavior in the diamond anvil cell was observed, with the intensity tendency of decreasing-increasing-decreasing and a shortened lifetime upon compression, due to the reversible stretchable Tb-Tb interactions. The Tb-Tb distance upon compression was refined through in situ high-pressure X-ray absorption spectra, which was consistent with the tendency of the piezofluorochromic intensity. In situ high-pressure UV-vis absorption spectra, Fourier transform infrared spectra, and powder X-ray diffraction demonstrated the full recovery of Tb-MOF after over 10 GPa compressions due to the semiflexible ligand. This work not only provided an ultrastable Tb-MOF but also illustrated the relationship of the piezofluorochromic behavior with the detailed structural transformation for the first time.

Stable Co(II)-based coordination polymer as fluorescence sensor for the discriminative sensing of biomarker methylmalonic acid

Three novel Co-based coordination polymers including {[Co(L)(μ3-O)1/3]2}n (1), {[Co(L)(bimb)]}n (2) and {[Co(L)(bimmb)1/2]}n (3) (H2L = 2,6-di(4-carboxylphenyl)-4-(4-(triazol-1-ylphenyl))pyridine), bimb = 1,4-bis(lmidazol) butane, bimmb = 1,4-bis(imidazole-1-ylmethyl)benzene) were successfully prepared under solvothermal conditions and characterized. Single-crystal X-ray diffraction analyses revealed that 1 possesses a 3D architecture composed of a trinuclear cluster [Co3N3(CO2)6(μ3-O)], 2 exhibits a 2D new topological framework with the point symbol (84·122)(8)2, whereas 3 shows a unique six-fold interpenetrated 3D framework with a (63·82·10)2(63)2(8) topology. Impressively, all of them can function as a highly selective and sensitive fluorescent sensor for the biomarker methylmalonic acid (MMA) via fluorescence quenching. The low detection limit, reusability and high anti-interference performance together make 1-3 become promising sensors for the practical detection of MMA. Furthermore, the successful application of MMA detection in urine sample was demonstrated, which may be a potential candidate for the further development of clinical diagnostic tools.

Highly dispersive PEI-modified CDs@ZIF-L dual-emitting fluorescent sensor for detecting metal ions

The leaf-like zeolitic imidazolate framework (ZIF-L) is a promising porous nanomaterial that has attracted increasing attention as an ideal host material to encapsulate functional fluorescent nanoparticles for designing fluorescent sensors. However, owing to the large particle size, gravity readily facilitates the precipitation of the ZIF-L from the aqueous solution, and thus lead to imperfect experimental results. Herein, we report a simple and rapid synthetic method which uses the polyethyleneimine (PEI)-modified ZIF-L as a host to solve the precipitation problem and construct a dual-emitting system that combines its fluorescence with carbon dots (CDs). Furthermore, CDs@ZIF-L/PEI with dual-emitting centres could be utilised as a ratio fluorescence sensor to detect Hg2+ ions. The sensor exhibited excellent dispersibility and good selectivity for sensing Hg2+ ions, with a limit of detection (LOD) of 14.5 nM. Furthermore, experimental results reveal that the CDs@ZIF-L/PEI fluorescent sensor could be effectively dispersed into agarose and less polar organic solvents such as DMF, MeOH, EtOH and CH3CN, expanding the application scope of the fluorescent sensor.

Eu3+ Complex-Based Superhydrophobic Fluorescence Sensor for Cr(VI) Detection in Water

Cr(VI) compounds are bioaccumulative and highly toxic pollutants, and there is a need for simple and fast detection methods to monitor their trace levels. In this work, we developed a Eu3+ complex-based fluorescence sensor to easily detect Cr(VI) in water droplets. Our sensor consists of a nanofibrous membrane electrospun with a blend of polyvinylidene fluoride (PVDF), silica particles, and Eu3+ complex. Upon modifying the membrane surface with fluoroalkyl chemistry, the sensor displayed superhydrophobicity. When a water droplet with Cr(VI) was placed on such a superhydrophobic fluorescence sensor, the overlapping absorption of Cr(VI) and Eu3+ complex facilitated the inner filter effect, allowing the selective detection of Cr(VI) down to 0.44 µM (i.e., 45.76 µg L-1). We proposed and designed of new inexpensive and fast sensor for the detection of Cr(VI).

Brine available two-dimensional nano-architectonics of fluorescent probe based on phosphate doped ZIF-L for detection of Fe3

Herein, we propose a simple and effective strategy for designing a zeolitic imidazolate frameworks (ZIFs) fluorescent probe with a two-dimensional leaf-like structure. By doping ZIF-L with phosphate, we developed a fluorescent probe for iron (Fe3+) in systems with high salinity. The fluorescence of P-ZIF-L was quenched effectively with the presence of Fe3+. The physicochemical structure, surface morphology, selectivity, stability and composition of the probe were investigated. Under optimized conditions, the fluorescent probe had a detection limit of 0.5 μM. Furthermore, the results that the probe exhibited desirable salt-tolerance and was suitable for determination of Fe3+ in brine water samples with satisfactory results.

Construction of High Quantum Yield Lanthanide Luminescent MOF Platform by In Situ Doping and Its Temperature Sensing Performance

Lanthanide luminescent MOF materials show excellent luminescent properties. However, obtaining lanthanide luminescent MOFs with high quantum yield is a challenging research. A novel bismuth-based metal-organic framework [Bi(SIP)(DMF)₂] was constructed by solvothermal method, utilizing 5-sulfoisophthalic acid monosodium salt (NaH₂SIP) and Bi(NO₃)₃·5H₂O. Thereafter, doped MOFs (Ln-Bi-SIP, Ln = Eu, Tb, Sm, Dy, Yb, Nd, Er) with different luminescent properties have been obtained by in situ doping with different lanthanide metal ions, among which Eu-Bi-SIP, Tb-Bi-SIP, Sm-Bi-SIP, and Dy-Bi-SIP have high quantum yield. What is special is that the doping amount of Ln³⁺ ions is very low, and the doped MOF can achieve high luminescence quantum yields. EuTb-Bi-SIP obtained by Eu³⁺/Tb³⁺ codoping and Dy-Bi-SIP exhibit good temperature sensing performance over a wide temperature range with the maximum sensitivity S_r of 1.6%·K^-1 (433 K) and 2.6%·K^-1, respectively (133 K), while the cycling experiments also show good repeatability in the assay temperature range. Finally, considering the practical application value, EuTb-Bi-SIP was blended with an organic polymer poly(methyl methacrylate) (PMMA) to produce a thin film, which shows different color changes at different temperatures.

Stable Lanthanide-Organic Frameworks: Crystal Structure, Photoluminescence, and Chemical Sensing of Vanillylmandelic Acid as a Biomarker of Pheochromocytoma

Several isostructural lanthanide metal-organic frameworks, viz. [Ln(DCHB)_1.5phen]_n (Ln-MOFs, where Ln = Eu for 1, Tb for 2, Sm for 3 and Dy for 4), are successfully synthesized through the hydrothermal reactions of 4'-di(4-carboxylphenoxy)hydroxyl-2, 2'-bipyridyl (H₂DCHB) and lanthanide nitrates as well as chelator 1,10-phenantroline (phen). These structures are characterized by single-crystal X-ray diffraction, and the representative Ln-MOF 1 is a fivefold interpenetrated framework with the uncoordinated Lewis base N sites form DCHB^2- ligands. The photoluminescence research studies reveal that Ln-MOFs 1-4 exhibit characteristic fluorescent emissions from ligand-induced lanthanide Ln(III) ions, while the single-component emission spectra of Ln-MOF 4 are all located in a white region under different excitations. The absence of coordinated water and the interpenetration property of the structures are conducive to the structure rigidity, and the results display that Ln-MOF 1 has high thermal/chemical stabilities in common solvents and a wide pH range as well as the boiling water. Notably, luminescent sensing studies reveal that Ln-MOF 1 with prominent fluorescence properties can perform in highly sensitive and selective sensing of vanillylmandelic acid (VMA) in aqueous systems (K_SV = 562.8 L·mol^-1; LOD = 4.6 × 10^-4 M), which can potentially establish a detection platform for the diagnosis of pheochromocytoma via multiquenching mechanisms. Moreover, the 1@MMMs sensing membranes comprised of Ln-MOF 1 and a poly(vinylidene fluoride) (PVDF) polymer can also be facilely developed for VMA detection in aqueous media, suggesting the enhanced convenience and efficiency of practical sensing applications.

Photothermal enhanced fluorescence quenching of Tb-norfloxacin for ultrasensitive human epididymal 4 detection

A fluorescence quenching enhanced immunoassay has been developed to achieve ultrasensitive recognition of human epididymal 4 (HE4) modifying the fluorescence quencher. The carboxymethyl cellulose sodium-functionalized Nb₂C MXene nanocomposite (CMC@MXene) was firstly introduced to quench the fluorescence signal of the luminophore Tb-Norfloxacin coordination polymer nanoparticles (Tb-NFX CPNPs). The Nb₂C MXene nanocomposite as fluorescent nanoquencher inhibits the electron transfer between Tb and NFX to quench the fluorescent signal by coordinating the strongly electronegative carboxyl group on CMC with Tb (III) of Tb-NFX complex. Simultaneously, due to the superior photothermal conversion capability of CMC@MXene, the fluorescence signal has been further weakened by the photothermal effect driven non-radiative decay of the excited state under near-infrared laser irradiation. The constructed fluorescent biosensor based on CMC@MXene probe finally realized the enhanced fluorescence quenching effect, and achieved ultra-high sensitivity and selective detection of HE4, exhibiting a wide linear relationship with HE4 concentration on the logarithmic axis in the range of 10^-5 to 10 ng/mL and a low detection limit of 3.3 fg/mL (S/N = 3). This work not only provides an enhanced fluorescent signal quenching method for the detection of HE4, but also provides novel insights for the design of fluorescent sensor toward different biomolecules.

Samarium-Based Turn-Off Fluorescence Sensor for Sensitive and Selective Detection of Quinolinic Acid in Human Urine and Serum

Quinolinic acid (QA) is an index for some diseases, whose detection is of importance. This work presents a samarium metal-organic framework (Sm-MOF) containing 5-sulfoisophthalate ligand (SIP^3-). The fluorescence of Sm-MOF integrates the emission at 339 nm from the SIP^3- ligand and four characteristic ⁴G_5/2 → ⁴H_j (j = 5/2, 7/2, 9/2, and 11/2) transitions at 559, 596, 642, and 701 nm from Sm(III). Sm-MOF as a turn-off fluorescence sensor to QA exhibits high sensitivity, selectivity, and durability. The fluorescence quenching response to QA shows a linear relationship of I₀/I = 0.00496·C_QA + 1.12474 in the QA concentration of 0-500 μM and a limit of detection calculated as 4.11 μM. Sm-MOF shows the structural and fluorescent stabilities in five quenching-recovery cycles. The recoveries of close to 100% in human urine and serum indicate high reliability. The paper-based Sm-MOF sensor displays a rough QA quantitative analysis by recognizing red values in the on-site QA detection.

Terbium(iii)-based coordination polymer with millimeter-size single crystals and high selectivity and sensitivity for folic acid

Terbium(iii)-based coordination polymer with millimeter-size single crystals and high selectivity and sensitivity for folic acid.

A Novel Dual-Emission Fluorescence Probe Based on CDs and Eu3+ Functionalized UiO-66-(COOH)2 Hybrid for Visual Monitoring of Cu2

In this work, CDs@Eu-UiO-66(COOH)₂ (denoted as CDs-F2), a fluorescent material made up of carbon dots (CDs) and a Eu³⁺ functionalized metal-organic framework, has been designed and prepared via a post-synthetic modification method. The synthesized CDs-F2 presents dual emissions at 410 nm and 615 nm, which can effectively avoid environmental interference. CDs-F2 exhibits outstanding selectivity, great sensitivity, and good anti-interference for ratiometric sensing Cu²⁺ in water. The linear range is 0-200 µM and the limit of detection is 0.409 µM. Interestingly, the CDs-F2's silicon plate achieves rapid and selective detection of Cu²⁺. The change in fluorescence color can be observed by the naked eye. These results reveal that the CDs-F2 hybrid can be employed as a simple, rapid, and sensitive fluorescent probe to detect Cu²⁺. Moreover, the possible sensing mechanism of this dual-emission fluorescent probe is discussed in detail.

Solvo-thermal synthesis of a unique cluster-based nano-porous zinc(II) luminescent metal-organic framework for highly sensitive detection of anthrax biomarker and dichromate

In this work a flexible multi-dentate 4,4'-(1H-1,2,4-triazole-1-yl) methylene-bis(benzonic acid) (H₂L) ligand has been employed, a unique cluster-based nano-porous luminescent zinc(II) metal-organic framework {[Zn(μ₆-L)]·(DMAC)₂}_n (1) (DMAC = Dimethylacetamide) has been isolated under solvo-thermal conditions. The H₂L ligand adopts hexa-dentate coordination modes via one triazole nitrogen atom and four aromatic carboxylate oxygen atoms, which bridge the neighboring six-coordinated Zn^II centers, leading to a three-dimensional (3D) nano-porous metal organic framework. A PLATON program analysis suggests the total potential solvent area volume is 2028.9 Å³, which occupy 62.5% percent of the unit cell volume (3248.4 Å³). PXRD Patterns of the as-synthesized samples 1 have been determined confirming the purity of the bulky samples. Photo-luminescent properties indicate strong fluorescent emissions of 1 at the room temperature. Further photo-luminescent measurements show that 1 can exhibit highly sensitive real-time luminescence sensing of anthrax biomarker dipicolinic acid (DPA) with high quenching efficiency (K_SV = 1.48 × 10⁵ M^-1) and low detection limit (0.298 μM (S/N = 3)). Meanwhile 1 also exhibits highly selective and sensitive luminescence sensing for Cr₂O₇^2- ions in aqueous solutions with high quenching efficiency K_SV = 1.22 × 10⁴ L·mol^-1 and low detection limit (0.023 μM (S/N = 3)). Therefore 1 can be used a unique multi-functional 3D cluster-based metal organic material in sensitive detection and effective detection of environment pollutants and biomarker molecules.

Facile fabrication of Tb3+-functionalized COF mixed-matrix membrane as a highly sensitive platform for the sequential detection of oxolinic acid and nitrobenzene

A novel Tb³⁺-functionalized covalent organic framework-based polymer mixed-matrix membrane (Tb³⁺@COF MMM) has been successfully fabricated by incorporating the highly stable Tb³⁺@PI-COF as filler into polyvinylidene fluoride (PVDF) solution. Compared with pure COF membrane, MMM exhibits its good flexibility, processability and high detection sensitivity. The obtained Tb³⁺@COF-MMM (M) can be employed as a highly sensitive sensing platform for the sequential detection of oxolinic acid (OA) and nitrobenzene (NB) based on a "off-on-off" process. M has performed its great selectivity, high sensitivity, and low detection limit for detecting OA with "turn-on" mechanism. Moreover, owing to the good chemical stability and anti-interference of M sensor, it is prospective to efficiently detect residues of OA in serum or river water. After the detection of M-15 toward OA, the obtained fluorescent M-15/OA exhibits the rapid quenching, facile manipulation, cycling utility and low detection limits for sensing NB solution and vapor. This work has proposed a typical case of developing flexible Ln³⁺-functionalized COF-based polymer mixed-matrix membrane as a highly sensitive sensing platform for detecting OA and NB, simultaneously revealed the applied potentiality of M for monitoring animal health and environmental pollution.

Design of an antenna effect Eu(III)-based metal-organic framework for highly selective sensing of Fe3

Highly selective sensing of Fe³⁺ is very important due to its great effect on biological systems. A novel ligand [1,1':4',1'':4'',1''':4''',1''''-quinquephenyl]-2,2'',2'''',5''-tetracarboxylic acid (H₄qptca) was designed and successfully obtained for the first time via three steps in high total yields according to the absorption spectrum of Fe³⁺. The europium(III)-based metal-organic framework derived from H₄qptca, {[Eu(qptca)_1/2(H₂qptca)_1/2(H₂O)₂]·DMF}_n (referred to as SLX-1), was then synthesized and used as a water-stable and highly selective luminescent sensor for Fe³⁺ in aqueous solution with a comparable detection limit using Ln-MOF probes (6.45 μM) through the antenna effect of SLX-1. Furthermore, the luminescence quenching mechanism was also proposed as a competitive absorption mechanism.

A Highly Stable Eu−MOF Multifunctional Luminescent Sensor for the Effective Detection of Fe3+, Cr2O72−/CrO42− and Aspartic Acid in Aqueous Systems

Heavy metal ions were common pollutants in water pollution. Amino acids, as important substances in organisms, participate in many life activities. The detection of heavy metal ions and amino acids...

A multi-responsive luminescent sensor based on a stable Eu(iii) metal–organic framework for sensing Fe3+, MnO4−, and Cr2O72− in aqueous solutions

A stable benzothiadiazole-based Eu(iii) metal–organic framework with cco topology has been successfully constructed, and represents the multifunctional fluorescence sensor toward Fe3+, MnO4− and Cr2O72− in aqueous solutions.

Metal–organic frameworks (MOFs) as fluorescence sensors: principles, development and prospects

This review classifies the latest developments of MOF-based fluorescence sensors according to the analytes, and discusses the challenges faced by MOF-based fluorescence sensors and promotes some directions for future research.

Fabrication of a Stable Europium-Based Luminescent Sensor for Fast Detection of Urinary 1-Hydroxypyrene Constructed from a Tetracarboxylate Ligand

A novel europium-centered metal-organic framework fabricated from a symmetric and rigid ligand with tetracarboxylate groups, 2,6-di(2',5'-dicarboxylphenyl)pyridine (H₄ddpp), has been synthesized solvothermally. Characterized by single-crystal X-ray diffraction, compound 1 features a 3D microporous structure with a butterfly-shaped trinuclear Eu₃(COO)₆ secondary building unit. Interestingly, three kinds of 1D open channels viewed in different directions in compound 1 are discovered, and the void ratio is calculated to be 47.5% by PLATON software. Solid-state luminescent experiments at 298 K reveal that compound 1 displays naked-eye characteristic red emission of Eu³⁺ ions monitoring the typical ⁵D₀ → ⁷F₂ transition. The exploration of luminescent sensing tests discloses that compound 1 has an outstanding capacity for recognizing urinary 1-hydroxypyrene (1-HP) with a quite fast response and high sensitivity, giving the quenching efficiency of 98.2% after the immersion time for just 1 min and 73.2% with the amount of 1-HP only 0.05 mg/mL. To our knowledge, it is the first reported Eu-MOF as an extremely fast-responsive and highly sensitive luminescent sensor for 1-HP which is interference-free from other urinary components. Furthermore, the successful preparation of the luminescent test papers makes compound 1 convenient, easy, and real-time in the application for sensing 1-HP in biomedical and biological fields.

New Ln-MOFs based on mixed organic ligands: synthesis, structure and efficient luminescence sensing of the Hg2+ ions in aqueous solutions

In view of Hg²⁺ ion sensing by luminescence, a series of new, phenanthroline-decorated 3D lanthanide metal organic frameworks (Ln-MOFs) valorising an original combination of four different lanthanides and two organic ligands, i.e. thiobis(4-methylene-benzoic acid) (H₂tmba) and 1,10-phenanthroline (phen), have been successfully synthesized, namely {[Ln₄(tmba)₆(phen)₄]·m(H₂O)(phen)}_n [Ln = Ce, m = 3 (1); Pr, m = 1 (2); Eu, m = 3 (3); and Tb, m = 3 (4)]. Compounds 1-4 were characterised by single-crystal X-ray diffraction, elemental and thermogravimetric analyses, and powder X-ray diffraction. The luminescence properties of complexes 3 and 4 were thoroughly investigated. It is herein proved that compound 3 sensitively and selectively acts as an excellent luminescent probe for the detection of Hg²⁺ ions in waters, with a detection limit of 1.00 μM. As additional assets, 3 displays superb stability over a wide pH range (3-12) of the aqueous media, as well as convenient recycling after completion of the detection experiments. The rationale for the observed luminescence quenching effect of mercury might be a strong interaction arising between Hg²⁺ ions and the carboxylate oxygen atoms of the tmba^2- ligand. The results open new perspectives for applications in environmental remediation.

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 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.

Ln-MOFs with window-shaped channels based on triazine tricarboxylic acid as a linker for the highly efficient capture of cationic dyes and iodine

Seven isostructural complexes were synthesized under solvothermal condition by the 4,4′,4′′ ((1,3,5-triazine-2,4,6-triyl)tri(azanediyl))tribenzoic acid and rare earth metal ions. It is found that 1 exhibits the adsorption capacity of 758.72 mg g⁻¹ to iodine.

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).

Eu3+ functionalized robust membranes based on the post-synthetic copolymerization of a metal-organic framework and ethyl methacrylate

Metal-organic frameworks (MOFs) are recognized as a class of promising crystalline materials. However, their subsequent processing and shaping still remain a challenge, and one emerging strategy is to hybridize MOFs with flexible polymers. Herein, by utilizing a simple and cost-effective post-synthetic polymerization method, under mild conditions, MOF particles with olefin bonds are covalently linked to polymer chains. Moreover, photoactive europium ions are also introduced into this system during the polymerization process. Importantly, the resulting MOF-based membrane (MOF1-Eu3+@PEMA) is uniform, showing great structural and fluorescence stability against strict conditions (aqueous solutions with pH 0.98-13.11). Besides, given its good luminescence properties, the membrane is employed for the identification of common volatile organic compounds and a selective response to toluene was achieved. This work accelerates the practical applications of MOF-based membranes and enriches the methods for MOF modification.

Eu-MOF and its mixed-matrix membranes as a fluorescent sensor for quantitative ratiometric pH and folic acid detection, and visible fingerprint identifying

The integration of 1 and polymer matrices leads to the fabrication of 1@polymer MMMs, which can be used in the detection of pH and folic acid. Powder samples of 1 also show potential for application in fingerprint identification.

Solvothermal and Ultrasonic Preparation of Two Unique Cluster-Based Lu and Y Coordination Materials: Metal-Organic Framework-Based Ratiometric Fluorescent Biosensor for an Ornidazole and Ronidazole and Sensing Platform for a Biomarker of Amoeba Liver Abscess

Through powerful solvothermal and facile ultrasonic synthetic strategies, two unique cluster-based lanthanide Lu and Y nanoporous metal organic frameworks (MOFs) have been successfully prepared, namely, {[Lu₂(L)₂]·2DMF·H₂O}_n (Lu-MOF) and [Y(L)(DMF)_0.75]_n (Y-MOF) (H₃L = terphenyl-3,4'',5-tricarboxylic acid). In addition, both the morphologies and nanosizes of Lu-MOF and Y-MOF materials also have been deliberately tuned by adjustable ultrasonic conditions including irradiation time (40, 60, and 80 min) and power (70 w, 100 w). Currently, it is noted that the abuse of antibiotics such as ornidazole and ronidazole leads to great damage to human health, and therefore the development of highly effective and facile detection methods for ornidazole and ronidazole is quite important. Herein, to improve the fluorescent sensing sensitivity of antibiotics, Eu³⁺ and Tb³⁺ have been introduced into Lu-MOF (under a solvothermal preparation method) to fabricate a dual-emission hybrid material Eu³⁺/Tb³⁺@Lu-MOF through a postsynthesis strategy, which can be successfully applied as a self-calibrated ratiometric fluorescent sensor for ornidazole and ronidazole with high selectivity and sensitivity (the K_sv value for ornidazole is 1.0854 × 10⁶ [M^-1], and the K_sv value for ronidazole is 1.0595 × 10⁷ [M^-1]) and low detection limit values (2.85 nM for ornidazole and 26.7 nM for ronidazole). On the other hand, amoeba liver abscess (ALA) will easily lead to irregular fever, night sweats, and other tortured symptoms; C-reactive protein autoantibody (CRP Ab) is the important biomarker for the detection of ALA. Given this, Y-MOF (under the solvothermal preparation method) also has been successfully designed to combine FAM-labeled NH-ssDNA to construct the scarcely reported excellent hybrid FAM-labeled NH-ssDNA/Y-MOF sensing platform for the highly effective discrimination of CRP Ab with excellent sensitivity and selectivity in real samples such as human serum solution.

Functional metal–organic frameworks as effective sensors of gases and volatile compounds

This review summarizes the recent advances of metal organic framework (MOF) based sensing of gases and volatile compounds.

3D lanthanide-coordination frameworks constructed by a ternary mixed-ligand: crystal structure, luminescence and luminescence sensing

Highly stable 3D Ln-MOFs were constructed by a ternary mixed-ligand. The Sm/Dy-MOFs present dual-emission while the Tb/Eu-MOFs exhibit red/green MC emission. The detection of quercetin and Fe³⁺ion was realized based on the luminescence Eu-MOF under the excitation of 358 nm.

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.