Highly Specific Sulfadiazine Detection Using a Two-Dimensional Europium-Organic Coordination Polymer

Sulfadiazine (SFZ) is an inexpensive large-consumption antibiotic used for treat bacterial infections but an excess of residues in food can be harmful. Fast and specific luminescence detection of SFZ is highly challenging because of the interference of structurally similar antibiotics. In this work, we develop a two-dimensional europium-organic coordination polymer with excellent luminescence and water stability for highly specific detection of SFZ in the range of 0-0.2 mM. Structural analysis shows that the high stability of coordination polymer is due to the high coordination number of europium ion and the special chelating coordination structure of ligand. The experiment results revealed that the high selectivity and effectively luminescence quenched behaviour of coordination polymer toward SFZ is caused by highly efficient inner filter effect.

An electrochemical impedimetric platform formed by a CNT@UiO-66 nanocomposite for quantitative analysis of oxytetracycline

Functional materials are considered one of the most critical factors in constructing high-performance electrochemical aptasensors in the sensing field. In this work, the microporous Zr-MOF UiO-66 (UiO = Universitetet i Oslo) is selected for assembly with carbon nanotubes (CNTs) to prepare a CNT@UiO-66 composite. The as-synthesized CNT@UiO-66 composite has a high surface area, excellent stability, good electrical conductivity, and abundant Zr(IV) sites, conferring it great potential for application in fabricating high-performance electrochemical aptasensors. It is gratifying that this electrochemical impedimetric aptasensor can detect trace oxytetracycline (OTC) from 0.01 to 0.7 pg mL-1 with a low limit of detection (LOD) of 1.48 fg mL-1. Meanwhile, this fabricated sensor based on CNT@UiO-66 has fine stability, excellent selectivity, and available reproducibility. In particular, the CNT@UiO-66-based aptasensor can quantitatively detect the OTC concentration in real samples.

Dual-Functional Eu-Metal-Organic Framework with Ratiometric Fluorescent Broad-Spectrum Sensing of Benzophenone-like Ultraviolet Filters and High Proton Conduction

The construction of attractive dual-functional lanthanide-based metal-organic frameworks (Ln-MOFs) with ratiometric fluorescent detection and proton conductivity is significant and challenging. Herein, a three-dimensional (3D) Eu-MOF, namely, [Eu4(HL)2(SBA)4(H2O)6]·9H2O, has been hydrothermally synthesized with a dual-ligand strategy, using (4-carboxypiperidyl)-N-methylenephosphonic acid (H3L = H2O3PCH2-NC5H9-COOH) and 4-sulfobenzoic acid monopotassium salt (KHSBA = KO3SC6H4COOH) as organic linkers. Eu-MOF showed ratiometric fluorescent broad-spectrum sensing of benzophenone-like ultraviolet filters (BP-like UVFs) with satisfactory sensitivity, selectivity, and low limits of detection in water/ethanol (1:1, v/v) solutions and real urine systems. A portable test paper was prepared for the convenience of actual detection. The potential sensing mechanisms were thoroughly analyzed by diversified experiments. The synergistic effect of the forbidden energy transfer from the ligand to Eu3+, the internal filtration effect (IFE), the formation of a complex, and weak interactions between the KHSBA ligand and BP-like UVFs is responsible for the ratiometric sensing effect. Meanwhile, Eu-MOF displayed relatively high proton conductivity of 2.60 × 10-4 S cm-1 at 368 K and 95% relative humidity (RH), making it a potential material for proton conduction. This work provides valuable guidance for the facile and effective design and construction of multifunctional Ln-MOFs with promising performance.

Size-controlling preparation of covalent organic framework nanospheres for electrochemical impedimetric aptasensing of oxytetracycline

Covalent organic framework (COF) nanospheres with controlled size of ∼500 and ∼1100 nm were successfully prepared by adjusting the HOAc amount in the synthetic system. The as-synthesized COFs have large conjugate aromatic skeleton, excellent stability, abundant pore, and uniform morphology. These advantages of COFs are benefit for immobilizing aptamers to fabricate the targeted electrochemical aptasensor. The commonly used oxytetracycline (OTC) is an analytic model to explore the sensing performance of the COF-based aptasensor, indicating that the smaller COF (∼500 nm) is more conducive to acquiring the sensitive sensor than that of the larger COF (∼1100 nm). Moreover, the limitation of detection of the COF (∼500 nm)-based aptasensor is calculated to be 7.4 fg mL^-1 using the response impedance signal. Additionally, the aptamer-based biosensor has fine reproducibility, good stability, excellent specificity, and available usability even in real samples.

A Minireview for Recent Development of Nanomaterial-Based Detection of Antibiotics

Antibiotics are considered a new type of organic pollutant. Antibiotic residues have become a global issue due to their harm to human health. As the use of antibiotics is increasing in human life, such as in medicine, crops, livestock, and even drinking water, the accurate analysis of antibiotics is very vital. In order to develop rapid and on-site approaches for the detection of antibiotics and the analysis of trace-level residual antibiotics, a high-sensitivity, simple, and portable solution is required. Meanwhile, the rapid nanotechnology development of a variety of nanomaterials has been achieved. In this review, nanomaterial-based techniques for antibiotic detection are discussed, and some reports that have employed combined nanomaterials with optical techniques or electrochemical techniques are highlighted.

Rational Synthesis of a Stable Rod MOF for Ultrasensitive Detection of Nitenpyram and Nitrofurazone in Natural Water Systems

Overuse of nitenpyram and nitrofurazone in agricultural products poses enormous risks to ecosystems, and effective detection and quantification of these residual pollutants are of great concern. Although several strategies have been established for detecting nitenpyram and nitrofurazone in water, searching for a new sensor material with great sensitivity, selectivity, and recyclability remains challenging. Here, we design and synthesize a stable metal-organic framework (MOF) (Zn-CPTA) by employing an organic linker based on the coordination features of benzene-1,4-dicarboxylate and picolinic acid. Zn-CPTA is a 3D framework built from Zn-O-Zn chains called rod secondary building units, which contains 1D open channels modified by uncoordinated carboxyl O atoms and exhibits impressive chemical stability in aqueous solutions within a pH range from 2 to 12. Especially, fluorescent Zn-CPTA can quickly and sensitively detect nitenpyram and nitrofurazone in aqueous solutions with a high quenching constant and low detection limit (LOD) (K_SV values for nitenpyram and nitrofurazone are 1.67 × 10⁴ and 1.02 × 10⁵ M^-1 with LOD of 0.625 and 0.126 μM, respectively), as well as outstanding selectivity and recyclability. Notably, the LOD value is the lowest among the reported MOFs used for nitrofurazone detection. Besides, experiments and density functional theory calculations are combined to explain the quenching mechanism. Finally, the practical application of Zn-CPTA was further explored in real environment samples with satisfactory recoveries.

Recent Advances in Metal-Organic-Framework-Based Nanocarriers for Controllable Drug Delivery and Release

Metal-organic frameworks (MOFs) have a good designability, a well-defined pore, stimulus responsiveness, a high surface area, and a controllable morphology. Up to now, various MOFs have been widely used as nanocarriers and have attracted lots of attention in the field of drug delivery and release because of their good biocompatibility and high-drug-loading capacity. Herein, we provide a comprehensive summary of MOF-based nanocarriers for drug delivery and release over the last five years. Meanwhile, some representative examples are highlighted in detail according to four categories, including the University of Oslo MOFs, Fe-MOFs, cyclodextrin MOFs, and other MOFs. Moreover, the opportunities and challenges of MOF-based smart delivery vehicles are discussed. We hope that this review will be helpful for researchers to understand the recent developments and challenges of MOF-based drug-delivery systems.

Two Stable Cd-MOFs as Dual-Functional Materials with Luminescent Sensing of Antibiotics and Proton Conduction

Construction and investigation of dual-functional metal-organic frameworks (MOFs) with luminescent sensing and proton conduction provide widespread applications in clean energy and environmental monitoring fields. By selecting a phosphonic acid ligand 4-pyridyl-CH₂N(CH₂PO₃H₂)₂ (H₄L) and coligand 2,2'-biimidazole (H₂biim), two cadmium-based MOFs [Cd_1.5(HL)(H₂biim)_0.5] (1) and (H₄biim)_0.5·[Cd₂(L)(H₂biim)Cl] (2) with different structures and properties have been hydrothermally synthesized by controlling reaction temperature. Based on the excellent thermal and chemical stabilities, and good luminescent stabilities in water solution, 1 and 2 can serve as luminescent sensors of chloramphenicol (CAP) with different quenching constant (K_SV) values and detection limits (LODs) in water, simulated environmental system, and real fish water system. Meanwhile, different sensing effects and possible sensing mechanisms are analyzed in detail. Moreover, 1 and 2 can also serve as good proton-conducting materials. The proton conductivities can reach up to 1.41 × 10^-4 S cm^-1 for 1 and 1.02 × 10^-3 S cm^-1 for 2 at 368 K and 95% relative humidity (RH). Among them, 2 shows better luminescent sensing and proton conduction performance than 1, which indicates that different crystal structures have a great impact on the properties of MOFs. Through the discussion of the relationship between structures and properties in detail, the possible reasons for the differences in properties are obtained, which can provide theoretical guidance for the rational design of this kind of dual-functional MOFs in the future.

pH-Stable Luminescent Metal-Organic Frameworks for the Selective Detection of Aqueous-Phase FeIII and CrVI Ions

The development of chemically stable metal-organic framework (MOF)-based luminescent platforms for toxic ion detection in an aqueous medium is highly challenging because most of the classical MOFs are prone to water degradation, and that is the reason why most of the MOF-based luminescent sensors use a nonaqueous medium for sensing. In this contribution, we report two new water-stable luminescent MOFs (Zn-MOF-1 and Zn-MOF-2), assembled from a mixed-ligand synthesis approach. Because of the presence of a hydrophobic trifluoromethyl group to the backbone and stronger metal-N coordination, these MOFs exhibit excellent stability not only in water but also in acidic/alkaline aqueous solutions (pH = 3-10). Here, we report a green sensing approach by exploiting the significant reduction in photoluminescence of these MOFs in the presence of toxic ions. Fe³⁺ and CrO₄^2-/Cr₂O₇^2- ions could be traced with a detection limit (LOD) in the micromolar range (0.045 and 0.745/0.33 μM for Zn-MOF-1; 125.2 and 114.2/83.5 μM for Zn-MOF-2). The mechanistic study reveals that competitive absorption of the excitation energy coupled with fluorescent resonance energy transfer are responsible for the turn-off quenching. The anti-interference ability and recyclability along with the pH stability gave these MOFs high potential to be used as practical sensors toward Fe^III and Cr^VI ions in water as a greenest medium.

A new three-dimensional zinc(II) metal-organic framework as a fluorescence sensor for sensing the biomarker 3-nitrotyrosine

3-Nitrotyrosine (3-NT), an oxidative stress biomarker, is closely associated with various diseases. Thus, rapid and sensitive detection of 3-NT is of great significance for preventing and treating diseases. Herein, we reported a new 3D zinc-based metal-organic framework (Zn-MOF) [Zn(L)(HBTC)] (L = (E)-4,4'-(ethene-1,2-diyl)bis[(N-pyridin-3-yl)benzamide], H₃BTC = 1,3,5-benzenetricarboxylic acid), which was structurally characterized by single crystal X-ray diffraction, IR, PXRD and TG. The Zn-MOF can be used as a highly efficient fluorescence sensing material to provide a direct and low-cost method for the rapid detection of 3-NT and shows high sensitivity with a K_SV value of 6.596 × 10⁴ M^-1, a rapid luminescence response within 24 s, excellent selectivity, high anti-interference ability and good recyclability. It is the first example of a MOF being used to directly detect 3-NT as a luminescence sensor to our knowledge. The sensing mechanism of the Zn-MOF towards 3-NT is discussed in detail, which provides a basis for the rational design of MOF sensing materials and their application in biomarker detection.

Stable Metal-Organic Frameworks for Fluorescent Detection of Tetracycline Antibiotics

The rapid detection of antibiotics in agricultural products is of great significance. In this work, two stable fluorescent metal-organic frameworks (MOFs), BUT-178 and BUT-179, are synthesized and used to detect tetracycline antibiotics. Among them, BUT-179 exhibits better performance in the detection of different tetracycline antibiotics in water and eggs. The limits of detection of BUT-179 toward tetracycline, aureomycin, oxytetracycline, and doxycycline all reach the nanomolar level. Furthermore, the cycling tests confirm that BUT-179 can be easily recovered and repeatedly used without an obvious performance loss. This work demonstrates the excellent application potential of MOFs for food safety, especially the fluorescence detection of antibiotics in foods.

Two Multiresponsive Luminescent Zn-MOFs for the Detection of Different Chemicals in Simulated Urine and Antibiotics/Cations/Anions in Aqueous Media

Two Zn-MOFs, namely, {[Zn(L)_0.5(bpea)]·0.5H₂O·0.5DMF}_n [LCU-113 (for Liaocheng University)] and {[Zn(L)_0.5(ibpt)]·H₂O·DMF}_n (LCU-114), were synthesized based on flexible tetracarboxylic acid 1,3-bis(3,5-dicarboxyphenoxy)benzene (H₄L) and different N-ligands [bpea = 1,2-dipyridyl ethane; ibpt = 3-(4'-imidazolobenzene)-5-(pyridine-4'-yl)-1,2,4-triazole]. LCU-113 and LCU-114 possess twofold interpenetrating three-dimensional pillared layer structures, in which a two-dimensional layer formed by carboxylic acid and Zn²⁺ ions was pillared by bpea and ibpt, respectively. The two complexes show high water stability and high luminescence sensing performance toward organic solvents, ions, and antibiotics, as well as chemicals, in simulated urine. The investigation showed that (1) LCU-113 and LCU-114 could detect uric acid (UA, 2,6,8-trihydroxypurine, metabolite of purine) and p-aminophenol (PAP, biomarker of phenamine) in simulated urine by luminescence quenching, respectively, and (2) luminescence quenching of LCU-113 and LCU-114 occurred in aqueous solutions of nitrofurazone (NZF), Fe³⁺, and CrO₄^2-/Cr₂O₇^2-. All the above detections have excellent anti-interference ability and recyclability. The luminescence mechanism analysis indicates that weak interactions between the framework structures and the target analytes as well as the energy competition (inner filter effect) play an important role in sensing the above analytes. The practical application for monitoring NZF/Fe³⁺ in water samples was also tested.

In situ optical spectroscopy for monitoring plasma-assisted formation of lanthanide metal-organic frameworks

A novel system was designed, which integrated in situ spectral monitoring with facile synthesis of lanthanide metal-organic frameworks in dielectric barrier discharge (DBD) plasma. It features miniaturization, cost-effectiveness and universality, for in situ spectral information of scattering and luminescence to gain insight into the reactive processes.

Two bis-ligand-coordinated Zn(ii)-MOFs for luminescent sensing of ions, antibiotics and pesticides in aqueous solutions

Two organometallic complexes with two and three-dimensional architectures were constructed by using multiple ligands and Zn(ii) ions: [Zn₃(BTC)₂(DTP)₄(H₂O)₂]·(H₂O)₄ (Zn-1) (BTC = benzene-1,3,5-tricarboxylic acid and DTP = 3,5-di(1,2,4-triazol-1-yl)pyridine) and [Zn₂(NTD)₂(DTP)] (Zn-2) (NTD = 1,4-naphthalenedicarboxylic acid). The as-prepared complexes were characterized by single-crystal X-ray diffraction (SCXRD), elemental analysis, powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and fluorescence analysis. Fluorescence sensing tests revealed that the two complexes are effective, sensitive and selective toward cationic Fe³⁺ and anionic MnO₄ ^- and Cr₂O₇ ^2-. During the antibiotic sensing process, cefixime (CFX) for Zn-1 and nitrofurantoin (NFT) for Zn-2 exhibited the highest quenching efficiencies. For sensing pesticides, the highest quenching efficiencies were exhibited by imidacloprid (IMI) toward Zn-1 and Zn-2. The fluorescence quenching of the complexes that was induced by antibiotics, pesticides and MnO₄ ^- was attributed to both the inner filter effect (IFE) and the fluorescence resonance energy transfer (FRET) effect.

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.

Incorporating Fullerenes in Nanoscale Metal-Organic Matrixes: An Ultrasensitive Platform for Impedimetric Aptasensing of Tobramycin

The rational design and preparation of available fullerene@metal-organic matrix hybrid materials are of profound significance in electrochemical biosensing applications due to their unique photoelectric properties. In this work, C₆₀@UiO-66-NH₂ nanocomposites serve as greatly promising materials to modify electrodes and fix aptamers, resulting in a remarkable electrochemical aptasensor for impedimetric sensing of tobramycin (TOB). Nanoscale composites have preferable electroactivity and small particle size with more exposed functional sites, such as Zr(IV) and -NH₂, to immobilize aptamers for enhanced detection performance. As we know, most of the electrochemical impedance aptasensors require a long time to complete the detection process, but this prepared biosensor shows the rapid quantitative identification of target TOB within 4 min. This work expands the synthesis of functional fullerene@metal-organic matrix hybrid materials in electrochemical biosensing applications.

An yttrium-organic framework based on a hexagonal prism second building unit for luminescent sensing of antibiotics and highly effective CO2 fixation

An yttrium-organic framework based on a hexagonal prism second building unit was constructed from nonanuclear yttrium(iii) and 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine for the luminescent sensing of antibiotics and highly effective CO2 fixation.

Current status and future prospects of nanoscale metal–organic frameworks in bioimaging

The importance of diagnosis and in situ monitoring of lesion regions and transportation of bioactive molecules has a pivotal effect on successful treatment, reducing side effects, and increasing the chances of survival in the case of diseases.

UiO-67-derived bithiophene and bithiazole MIXMOFs for luminescence sensing and removal of contaminants of emerging concern in wastewater

The UiO-67-type MIXMOF [Zr6O4(OH)4(PhPh)5(TzTz)], containing a blue-emitting bithiazole linker, is a potential multifunctional material for environmental remediation, being both a luminescent sensor and an adsorbent for diclofenac in aqueous solutions.

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.

Reversible Structural Transformation of CuI-TbIII Heterometallic MOFs with Highly Efficient Detection Capability toward Penicillin

A Cu^I-Tb^III heterometallic MOF, namely 1·DMF, was obtained via a coordination assembly process of isonicotinic acid with Cu^I and Tb^III. 1·DMF can be switched to 1·MeOH in methanol with a luminescent emission response. Meanwhile, 1·MeOH exhibits a reversible single-crystal transformation to 1·DMF after immersion in DMF. Both MOFs have superior physicochemical stability. The 1·DMF-based biosensor has a remarkable sensing performance toward penicillin.

Enhancing Demulsification Performance for Oil-Water Separation through Encapsulating Ionic Liquids in the Pore of MIL-100(Fe)

Emulsion poses a greater challenge for the remediation of oily wastewater, which can be effectively resolved by the metal-organic framework of MIL-100(Fe). The formula Fe₃O(H₂O)₂(OH) (BTC)₂ pronounces that MIL-100(Fe) suffers from an intrinsic defect of less charged atoms, which limits its demulsification performance for oil-water separation. Herein, cations of the ionic liquid (1-allyl-3-methylimidazolium, Amim⁺) were encapsulated in the micropore of MIL-100(Fe) in situ to increase the positive charge density of MIL-100(Fe). Zeta potential demonstrated that the encapsulation of Amim⁺ increased the positive charge amount of MIL-100(Fe). N₂ probe isothermal adsorption/desorption and spectral measurements (X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflection spectroscopy, and attenuated total-reflectance infrared spectroscopy) revealed the host-guest interactions of π···Fe complexation and π···cation electrostatic attraction between Amim⁺ and MIL-100(Fe) for the composite materials. Amim⁺ encapsulation greatly enhanced the demulsification performance of MIL-100(Fe) for oil-in-water (O/W) emulsion stabilized by sodium dodecyl sulfate. Amim⁺-encapsulated MIL-100(Fe) with an Amim⁺/Fe³⁺ molar ratio of 1:1 [Amim@MIL-100(Fe)-3:3] showed a demulsification efficiency (DE) of 94% within 30 s, compared with MIL-100(Fe) within 30 min. The maximum DE of Amim@MIL-100(Fe)-3:3 was found to be more than 98% within 5 min. The DE lost by MIL-100(Fe) at the third run decreased from 36 to 17% after encapsulating Amim⁺. The analysis of surface charge and interfacial tension implied a demulsification mechanism of capturing-fusion, which could be promoted by the greater electrostatic attraction. Finally, the role of Amim⁺ on the outstanding demulsification performance by Amim⁺-encapsulated MIL-100(Fe) could be explained by the enhanced nonbonded interaction of electrostatic attraction and van der Waals based on the molecular dynamics simulation.

Advancement in functionalized luminescent frameworks and their prospective applications as inkjet-printed sensors and anti-counterfeit materials

Supramolecular luminescent frameworks with conjugated architectures exhibits interesting photophysical properties with phenomenal chemical and thermal stability. This has instigated global researchers towards its extensive application in toxic analyte detection and the formulation of anti-counterfeit materials. In correlation with this present scenario, luminescent metal-organic frameworks (LMOFs), possessing tailorable structural and functional properties and exceptional physicochemical features, have been categorized as emerging 'smart materials'. Interestingly, LMOFs have assisted in the rapid development of an effectual sensing platform and swift fabrication of anti-counterfeit materials on desirable substrates with the aid of 'Inkjet Printing', which is a viable, low-cost, and high-resolution technology. Inkjet printing is an excellent material deposition technique in the modern era owing to its easy settling over flexible substrates, simplistic emergence of large area image patterns with improved throughput, minimal cost, explicit resolution, and least waste generation. The present review provides state-of-the-art progress on LMOFs based (i) luminescent security ink fabrication with static and dynamic multinodal luminescent materials and (ii) sensory device formulation for the easy and instantaneous recognition of hazardous analytes through the 'Inkjet Printing' technology. This techno-chemical integration will be certainly beneficial to prevent the growth of counterfeit materials and monitor the bioaccumulation of hazardous analytes in our ecological system.

A Water-Stable Tb-MOF As a Rapid, Accurate, and Highly Sensitive Ratiometric Luminescent Sensor for the Discriminative Sensing of Antibiotics and D2O in H2O

The design and development of self-calibrating ratiometric luminescent sensors for the fast, accurate, and sensitive discrimination and determination of pollutants in wastewater is highly desirable for public and environmental health. Herein, a 3D porous Tb(III)-based metal-organic framework (MOF), {[Tb(HL)(H₂O)₂]·x(solv)}_n (1), was facilely synthesized using a urea-functionalized tetracarboxylate ligand, 5,5'-(((1,4-phenylenebis(azanediyl))bis(carbonyl))bis(azanediyl))diisophthalic acid (H₄L). The activated framework showed a good water stability in both aqueous solutions at a wide pH range of 2-14 and simulated antibiotic wastewaters. Interestingly, this Tb-MOF exhibited dual luminescence owing to the partial energy transfer from the antenna H₄L to Tb³⁺. More importantly, activated 1 (1a) that was dispersed in water showed a fast, accurate, and highly sensitive discrimination ability toward antibiotics with a good recyclability, discriminating three different classes of antibiotics from each other via the quenching or enhancement of the luminescence and tuning the emission intensity ratio between the H₄L ligand and the Tb³⁺ center for the first time. Simultaneously, 1a is a ratiometric luminescent sensor for the rapid, accurate, and quantitative discrimination of D₂O from H₂O. Furthermore, this complex was successfully used for the effective determination of antibiotics and D₂O in real water samples. This work indicates that 1a represents the first ever MOF material for the discriminative sensing of antibiotics and D₂O in H₂O and promotes the practical application of Ln-MOF-based ratiometric luminescent sensors in monitoring water quality and avoiding any major leak situation.

Stimuli -triggered fluoro-switching in metal-organic frameworks: applications and outlook

The design and synthesis of efficient sensor materials with fast-responsive and ultrasensitive detection ability is critical to monitor ecological safety, supervise human health, control industrial wastes, and govern food quality among others. Metal-organic frameworks (MOFs) or coordination polymers (CPs) are a new class of porous crystalline materials that have emerged in several potential applications in last two decades. In particular, applications of MOFs as sensory scaffolds for the detection of hazardous pollutants have attracted researchers due to their fabulous structural characteristics and wide range of pore environment tunability. Among several transducer procedures, the luminescence detection of a particular analyte is immensely desirable as it is easy to handle and cost effective, where visual changes in physicochemical attributes can be comprehended via a quick naked eye detection. The porous nature of MOFs facilitates the pre-concentration of target analytes within the pore structure and provides superior host-guest interaction with good detection limits when compared to conventional materials. To this end, guest-induced fluorescence switching in sensory MOFs with good recyclability and unique detectable fingerprints are of particular importance to benefit futuristic monitoring aptitudes and promises environmental remediation. In this review, we present the latest literature based on the analyte-responsive modulation of fluorescence intensity in MOFs towards the detection of target pollutants and discuss the underlying sensing mechanism, which can assist in developing new useful nano-scale devices and sensors.

Photoinduced versus spontaneous host–guest electron transfer within a MOF and chromic/luminescent response

The MOF shows charge-transfer sensitized Eu(iii) emission and spontaneous/photoinduced guest-to-host electron transfer, which allow chromic and luminescent sensing of NH3 (luminescence turn-off) and O2 (luminescence turn-on).

Luminescent metal–organic frameworks as chemical sensors based on “mechanism–response”: a review

The comprehensive review systematically summarizes the recent developments in the study of LMOFs as chemical sensors based on “mechanism–response”.