Low background dual-ligand Cu-MOF nanoprobe for plant tissue imaging and fast screening as well as sensitive detection of glyphosate in environmental samples

The monitoring of glyphosate residue in environmental samples is critically important due to its high environmental risk. Here, we reported a low background dual-ligand and fast response copper-based metal organic framework (Cu-MOF) nanoprobe for imaging glyphosate in plant tissue, rapid screening of glyphosate-contaminated samples, and sensitive detection of glyphosate in environmental samples. The Cu-MOF nanoprobe was prepared with 2-Aminoisophthalic Acid (AIA) and trimesic acid (H3BTC) as ligands, and Cu2+ as a metal node. Thanking to both ligand-to-metal charge transfer (LMCT) and photoinduced electron transfer (PET) effects, the fluorescence of ligand AIA could be fully quenched in Cu-AIA/BTC probe. Upon the addition of glyphosate, it competed with the ligands in Cu-AIA/BTC probe, causing the collapse of MOF structure and the release of ligand AIA with obvious fluorescence recovery. This nanoprobe exhibited a desirable linear response for glyphosate in the concentration range of 0.1-80 μM, with a low detection limit of 33 nM, much lower than the maximum contaminant level (4.1 μM) set by the U.S. Environmental Protection Agency (EPA). Furthermore, it was also successfully applied for plant tissue imaging, fast screening of glyphosate-contaminated samples and monitoring of the degradation of glyphosate on tea leaves and in soil, indicating the broad application prospect of the nanoprobe.

Synthesis and applications of luminescent metal organic frameworks (MOFs) for sensing dipicolinic acid in biological and water samples: a review

The detection of trace quantities of 2,6-dipicolinic acid (DPA) in real-world samples is crucial for early disease diagnosis and routine health monitoring. Metal-organic frameworks (MOFs), recognized for their diverse structural architectures, have emerged as advanced multifunctional hybrid materials. One of the most notable properties of MOFs is their luminescence (L), which can arise from structural ligands, guest molecules, and emissive metal ions. Luminescent MOFs have shown significant promise as platforms for sensor design. This review highlights the application of luminescent MOFs in the detection of DPA in biological and aqueous environments. It provides a comprehensive discussion of the various detection strategies employed in luminescent MOF-based DPA sensors. Additionally, it explores the origins of L in MOFs, their synthesis, and the mechanisms underlying their sensing capabilities. The article also addresses key challenges and limitations in this field, offering practical insights for the development of efficient luminescent MOFs for DPA detection.

What Should be Considered While Designing Hole-Transporting Material for Perovskite Solar Cells? A Special Attention to Thiophene-Based Hole-Transporting Materials

The molecular design and conformations of hole-transporting materials (HTM) have unravelled a strategy to enhance the performance of environmentally sustainable perovskite solar cells (PSC). Several attempts have been made and several are underway for improving the efficiency of PSCs by designing an efficient HTM, which is crucial to preventing corrosion, facilitating effective hole transportation, and preventing charge recombination. There is a need for a potential alternative to the current market-dominating HTM due to its high cost of production, dopant requirements, moisture sensitivity, and low stability. Among several proposed HTMs, molecules derived from thiophene exhibit unique behaviour, such as the interaction with under-coordinated Pb2+, thereby facilitating the passivation of surface defects in the perovskite layer. In addition, coupling a suitable side chain imparts a hydrophobic character, eventually leading to the development of a moisture-sensitive and highly stable PSC. Furthermore, thiophene-backboned polymers with ionic pendants have been employed as an interfacial layer between PSC layers, with the backbone facilitating efficient charge transfer. This perspective article comprehensively presents the design strategy, characterization, and function of HTMs associated with thiophene-derived molecules. Hence, it is observed that thiophene-formulated HTMs have an enhanced passivation effect, good performance in an open-circuit environment, longevity, humidity resistance, thermostability, good hole extraction, and mobility in a dopant-free condition. For a better understanding, the article provides a comparative description of the activity and function of thiophene-based small molecules and polymers and their effect on device performance.

Thiophene derived sky-blue fluorescent probe for the selective recognition of mercuric ion through CHEQ mechanism and application in real time samples

A vibrant blue organic luminescent material with enhanced photophysical properties is in great demand for the generation of optoelectronic devices and luminescent sensors. In this context, the thiophene-benzimidazole probe TH-IMI was designed and synthesized by a simple condensation reaction. The synthesized probe has shown excellent photophysical properties like high FL intensity, a high quantum yield of 90% in the solution phase, a low optical bandgap of 2.84 eV, positive solvatochromic effect in emission spectra and Disaggregation Caused Quenching Effect (DCQE). Such a high luminescent probe was employed for the recognition of mercuric ions in the solution phase, solid state detection, and in tracking mercury in green gram sprouts. UV-visible absorption and emission spectra, 1H NMR titration, IR spectroscopic and ESI-MS techniques confirmed that the probe underwent a fluorescence quenching response via the CHEQ effect upon exposure to Hg2+. The stoichiometry was found to be 1:1 through Job's plot and has a fast response rate and relatively low limit of detection of about 6.13 × 10-11 M in a linear range between 0 and 110 µL.

A Tb3+ ion encapsulated anionic indium-organic framework as logical probe for distinguishing quenching Fe3+ and Cu2+ ions

We successfully synthesized a stable anionic microporous metal-organic framework (MOF) HDU-1 ([Me2NH2]2In2[(TATAB)4(DMF)4](DMF)4(H2O)4) and constructed a fluorescent probe Tb@HDU-1 by an exchange strategy. Because of its suspension distinct fluorescent response of Tb(III) characteristic transition and ligand emission, the Tb@HDU-1 can be used as fluorescent probe for sensing towards Fe3+ and Cu2+ ions. It is surprising that Tb@HDU-1 is used as a ratiometric fluorescent probe for Cu2+ ions while only single peak detection for Fe3+ ions, which describes a particular rare example of a sensor based on Ln-MOFs to distinguish quenching Fe3+ and Cu2+ ions. Hence we designed a molecular logic gate device for making the distinction of Fe3+ and Cu2+ ions more clearly and appropriately. In addition, the different quenching effect between Fe3+ and Cu2+ ions may be ascribed to the differences of competitive absorption and interaction between frameworks and metal ions.

Fluorescence sensing and device fabrication with luminescent metal-organic frameworks

Metal-organic frameworks (MOFs) are a novel class of hybrid porous multi-functional materials consisting of metal ions/clusters and organic ligands. MOFs have exclusive benefits due to their tunable structure and diverse properties. Luminescent MOFs (LMOFs) exhibit both porosity and light emission. They display abundant host and guest responses, making them conducive to sensing. Currently, LMOF sensing research is gaining more depth, with attention given to their device and practical applications. This work reviews recent advancements and device applications of LMOFs as chemical sensors toward ions, volatile organic compounds, biomolecules, and environmental toxins. Furthermore, the detection mechanism and the correlation between material properties and structure are elaborated. This analysis serves as a valuable reference for the preparation and efficient application of targeted LMOFs.

Differential fluorescent response to amino acids based on metal-organic framework Zn-PBC

A novel metal-organic framework (MOF) Zn-PBC (H2PBC = pyridine-3,5-bis(phenyl-4-carboxylic acid)) was designed and synthesized via a solvothermal reaction with the H2PBC ligand, and produced a strong fluorescence. The material exhibited good stability and an ideal luminescent property in water. In addition, it was found that Zn-PBC displayed a different fluorescent response to different types of amino acids, and the mechanism was investigated. This research might give insight to the interaction between MOFs and amino acids, which would provide a strategy to fabricate MOF-based sensors for biomolecules in future.

Optical Imaging Opportunities to Inspect the Nature of Cytosolic Iron Pools

The chemical nature of intracellular labile iron pools (LIPs) is described. By virtue of the kinetic lability of these pools, it is suggested that the isolation of such species by chromatography methods will not be possible, but rather mass spectrometric techniques should be adopted. Iron-sensitive fluorescent probes, which have been developed for the detection and quantification of LIP, are described, including those specifically designed to monitor cytosolic, mitochondrial, and lysosomal LIPs. The potential of near-infrared (NIR) probes for in vivo monitoring of LIP is discussed.

Identification of folic acid and sulfaquinoxaline using a heterometallic Zn-Eu MOF as a sensor

A d-f heterometallic MOF using the 2,2'-bipyridine-4,4'-dicarboxylic acid ligand (H₂LZ) was obtained by solvothermal synthesis, namely [EuZn(LZ)₂(HCOO)(H₂O)₃]_n (1). The structure analysis shows that compound 1 comprises heterometallic Zn²⁺ and Eu³⁺ ions, which are connected by LZ^2- and HCOO^- anions to form a three-dimensional framework. MOF 1 exhibited high stability of fluorescence intensity in the scope of pH 2-11 in an aqueous solution. Furthermore, MOF 1 served as an excellent selective sensing material for the detection of folic acid in the presence of some imitating materials of the human body and discerned sulfaquinoxaline in sulfonamide drugs with high sensitivity, selectivity, and reusability. Moreover, we designed and manufactured a sensor paper based on MOF 1 as a portable device for the visual detection of folic acid and sulfaquinoxaline. More crucially, this is the first example in which luminescent MOF is used to identify sulfaquinoxaline molecules in an aqueous solution. In addition, the luminescence sensing mechanisms of MOF 1 for the detection of the above analytes were explored in detail.

The study of a novel high selectivity pyrenyl-based fluorescence probe with aggregation-induced emission characteristics for Fe3+ detection designed by a structure modulation strategy

The past decades have witnessed the feat of fluorescent probes for Fe³⁺ detection, where eliminating the interference by other metal ions plays a pivotal role in its detection by probes in complex environments. Herein, by taking advantage of the substituent effects, the electron-withdrawing group (EWG) -CF₃ and electron-donating group (EDG) -CH₃ were introduced to 2-(1-pyrenyl)pyridine (pypyr) to prepare two turn-off fluorescence probes, 5-trifluoromethyl-2-(1-pyrenyl)pyridine (pypyr-CF3) and 5-methyl-2-(1-pyrenyl)pyridine (pypyr-CH3). Intriguingly, both probes displayed novel aggregation-induced emission (AIE) characteristics in MeCN/H₂O mixtures and the size and morphology of the aggregated particles were studied via DLS and TEM. By the modulation strategy, pypyr-CF3 can detect Fe³⁺ in the presence of 29 different metal ions without interference. Comparatively, pypyr-CH3 experienced serious interference from other metal ions such as Hg²⁺ and Zr⁴⁺. Besides, pypyr-CF3 not only demonstrated a higher photoluminescence quantum yield (PLQY) of 65.25% and wider pH adaptability but is also capable of Fe³⁺ detection over a wide pH range of 2-11 with a short response time (5 seconds). A plausible quenching mechanism based on the inner filter effect has also been demonstrated. More importantly, the versatile applications of pypyr-CF3, such as the quantitative analysis of Fe³⁺ in actual water samples, anti-forgery ink, fingerprint identification, etc., further corroborate its superb capabilities. This study aims to lend concrete support to the design and selectivity modulation of probes.

A dual-channel visual sensing system for recognition of multiple metal ions

Here, we propose a simple, rapid, and effective colorimetric sensor array for discrimination of metal ions. The sensor array was constructed using two sensing channels, i.e., gold nanoparticles (AuNPs)- Tetramethylbenzidine (TMB)-H₂O₂ and AuNPs-O-phenylenediamine (OPD)-H₂O₂ reaction systems. The presence of metal ions with positive charges would lead to the corresponding surface charge change of negatively charged AuNPs, resulting in diverse catalytic performances of citrate-modified AuNPs, accompanied by a substantial colorimetric performance of oxidation products of TMB and OPD. Employing the diversity of colorimetric responses of metal ions to the two sensing channels, nine metal ions including Cr³⁺, Fe³⁺, Cu²⁺, Co²⁺, Ni²⁺, Pb²⁺, Mg²⁺, K⁺, and Cd²⁺ were well distinguished with a discrimination accuracy of 100% at a concentration as low as 50 nM. Further experiment showed that the sensor array was also capable of discriminating and quantifying metal ions at various concentrations, as well as the identification of metal ion mixtures. The feasibility of the sensor array was also verified by the successful identification of the nine metal ions in river water samples.

Thiazole-Formulated Azomethine Compound for Three-Way Detection of Mercury Ions in Aqueous Media and Application in Living Cells

Heavy metal ions are extremely poisonous and cause long-term harm to living organisms. Among these ions, mercury is the most toxic metal and has no notorious purpose in the human body. In this regard, an elegant azomethine thiazole compound AM1 was synthesized, and it was found to be highly sensitive to three-way detection of mercury ions with detection limits of 0.1126 × 10^-9 M (FL) and 0.64 × 10^-6 M (UV-vis). AM1 highlighted the capability to detect mercury ions through the colorimetric method, the fluorometric method, and via the naked eye in three-way detection. In addition, the structure of AM1 was confirmed by single-crystal X-ray diffraction studies and crystallized in a monoclinic crystal system with a P21/c space group, and it shows numerous noncovalent interactions in the crystal packing. The high sensitivity of AM1 to Hg²⁺ ions was imputed to the quenching mechanism and was estimated by Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (¹H-NMR), high-resolution mass spectrometry (HRMS), ultraviolet-visible (UV-vis) absorbance, fluorescence (FL) emission, Job's plot, B-H plot, and DFT calculation. Naked eye color change of AM1 solution to yellow and turn-off FL by the addition of mercury ion is due to complex formation. In addition to mercury ions, the sensor displayed a new absorption peak at around 240 nm. Furthermore, an AM1-coated test strip is used as the solid support sensor, and real-time detection of Hg²⁺ ions in the HeLa cell line by fluorescence microscopy is performed.

Stable Cd Metal-Organic Framework as a Multiresponsive Luminescent Biosensor for Rapid, Accurate, and Recyclable Detection of Hippuric Acid, Nucleoside Phosphates, and Fe3+ in Urine and Serum

Detecting biomarkers associated with diseases has significant meaning for early prevention, diagnosis, and treatment of diseases. The development of luminescent biosensors for rapid and accurate detection in real urine and serum is urgently desired for human health monitoring. Herein, a luminescent cadmium metal-organic framework, {[Cd(L)(bpbix)]·x(solv)}_n (1), was successfully prepared by using a urea-functionalized dicarboxylate ligand, 5-(3-(pyridin-4-yl)ureido)isophthalic acid (H₂L), 4,4'-bis((1H-imidazol-1-yl)methyl)biphenyl (bpbix), and the Cd²⁺ ion. The structure of 1 presents a 2-fold interpenetrating three-dimensional pillared-layer framework. The complex 1 exhibits good stability in different-pH aqueous solutions and physiological fluids. Strikingly, the complex 1 shows quick response, high sensitivity, good anti-interference performance, and a recyclable ability for simultaneous sensing of hippuric acid (HA), nucleoside phosphates, and Fe³⁺ in water. More significantly, this sensor can realize the sensitive and accurate detection of HA, nucleoside phosphates, and Fe³⁺ in real urine and serum and meet the practical detection needs in clinical diagnosis. These results indicate that the complex 1 as a multiresponsive luminescent biosensor possesses great potential for practical detection of HA, nucleoside phosphates, and Fe³⁺ in biological samples.

Turn-up Luminescent Sensing of Ultraviolet Radiation by Lanthanide Metal-Organic Frameworks

Here, we report a series of two-dimensional lanthanide metal-organic frameworks Ln-DBTPA (where DBTPA = 2,5-dibromoterephthalic acid and Ln = Tb (1), Eu (2), or Gd (3)) showing a unique turn-up responsiveness toward ultraviolet (UV) radiation. The luminescence enhancement was derived from the accumulated radicals that can promote the intersystem crossing process. The compound 1 shows an ultralow detection limit of 9.1 × 10^-9 J toward UV radiation, representing a new type of luminescent UV detectors.

Recent progress on porous MOFs for process-efficient hydrocarbon separation, luminescent sensing, and information encryption

Metal-organic frameworks (MOFs), as an emerging class of porous materials, excel in designability, regulatability, and modifiability in terms of their composition, topology, pore size, and surface chemistry, thus affording a huge potential for addressing environment and energy-related challenges. In particular, MOFs can be applied as porous adsorbents for the purification of industrially important hydrocarbons through certain process-efficient separation schemes based on selectivity-reversed adsorption and multicomponent separation. Moreover, the vast combination possibilities and controllable and engineerable luminescent units of MOFs make them a versatile platform to develop functionally tailored materials for luminescent sensing and optical data encryption. In this feature article, we summarize the recent progress in the use of porous MOFs for the separation and purification of acetylene (C₂H₂) and ethylene (C₂H₄) based on selectivity-reversed adsorption and multicomponent separation strategies. Moreover, we highlight the advances over the past three years in the field of MOF-based luminescent materials for thermometry, turn-on sensing, and information encryption.

Lanthanide-MOFs as Multifunctional luminescence Sensors

Five isostructural lanthanide metal-organic frameworks, [Ln(BDPO)(H2O)4] (Ln= Eu for CUST-623, Tb for CUST-624, Gd for CUST-625, Dy for CUST-626, Sm for CUST-627, BDPO = N, N' bis (3,5 - dicarboxyphenyl)-oxalamide)...

A Eu(iii) metal–organic framework based on anthracenyl and alkynyl conjugation as a fluorescence probe for the selective monitoring of Fe3+ and TNP

In this work, a luminescent metal–organic framework (Eu-MOF {[Eu₆L₆(μ₃-OH)₈(H₂O)₃]₈·H₂O}_n) was constructed by a solvothermal method with a linear organic ligand L (10-[(2-amino-4-carboxyl-phenyl)ethynyl]anthracene-9-carboxylic acid) based on anthracene and alkyne groups and using Eu³⁺ as the metal center. The MOF exhibits a stable UiO-66 crystal structure, and a six-core cluster twelve-linked secondary structural unit was successfully synthesized using 2-fluorobenzoic acid as a modulator, forming a classical fcu topology. Moreover, it exhibits good chemical stability. Interestingly, Eu-MOF exhibited high selectivity and sensitive fluorescence burst properties towards Fe³⁺ ions and 2,4,6-trinitrophenol (TNP) in DMF solution. For Fe³⁺, the K_SV value is 5.06 × 10⁵ M⁻¹ and the LOD value is 5.1 × 10⁻⁷ M. For TNP, the K_SV value is 1.92 × 10⁴ M⁻¹ and the LOD value is 1.93 × 10⁻⁶ M. In addition, Eu-MOF showed good anti-interference ability and fast response. This work provides an excellent fluorescent sensor for the detection of Fe³⁺ and 2,4,6-trinitrophenol (TNP) residues in contaminants.

In this work, Eu-MOF has been synthesized and has excellent luminescence recognition ability for Fe³⁺ and TNP with good selectivity and high sensitivity via luminescence quenching.

Phototriggered Aggregation-Induced Emission and Direct Generation of 4D Soft Patterns

Microscopic control of macroscopic phenomena is one of the core subjects in materials science. Particularly, the spatio-temporal control of material behaviors through a non-contact way is of fundamental importance but is difficult to accomplish. Herein, a strategy to realize remote spatio-temporal control of luminescence behaviors is reported. A multi-arm salicylaldehyde benzoylhydrazone-based aggregation-induced emission luminogen (AIEgen)/metal-ion system, of which the fluorescence can be gated by the UV irradiation with time dependency, is developed. By changing the metal-ion species, the fluorescence emission and the intensity can also be tuned. The mechanism of the UV-mediated fluorescence change is investigated, and it is revealed that a phototriggered aggregation-induced emission (PTAIE) process contributes to the behaviors. The AIEgen is further covalently integrated into a polymeric network and the formed gel/metal-ion system can achieve laser-mediated mask-free writing enabled by the PTAIE process. Moreover, by further taking advantage of the time-dependent self-healing property of hydrazone-based dynamic covalent bond, transformable 4D soft patterns are generated. The findings and the strategy increase the ways to manipulate molecules on the supramolecule or aggregate level. They also show opportunities for the development of controllable smart materials and expand the scope of the materials in advanced optoelectronic applications.

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.

Recent progress in the development of MOF-based optical sensors for Fe3

Fe(iii) is a common pollutant released into our ecosystem from various industrial and anthropogenic activities which when in excess interferes with human health. A plethora of sensors based on various designs and working principles are being continuously synthesized and improvised for its facile detection. In the present review, we have provided a brief overview of the developments made in the field of metal organic framework (MOF) based optical sensors for Fe3+. MOFs have exponentially emerged in the field of research due to their high porosity, modular construction and easy tunability. These inorganic-organic hybrid porous materials are being essentially promoted as optical sensors because of their unique photophysical properties and potential sensing applications.

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+.

Metal-Organic Frameworks for Liquid Phase Applications

In the last two decades, metal-organic frameworks (MOFs) have attracted overwhelming attention. With readily tunable structures and functionalities, MOFs offer an unprecedentedly vast degree of design flexibility from enormous number of inorganic and organic building blocks or via postsynthetic modification to produce functional nanoporous materials. A large extent of experimental and computational studies of MOFs have been focused on gas phase applications, particularly the storage of low-carbon footprint energy carriers and the separation of CO2-containing gas mixtures. With progressive success in the synthesis of water- and solvent-resistant MOFs over the past several years, the increasingly active exploration of MOFs has been witnessed for widespread liquid phase applications such as liquid fuel purification, aromatics separation, water treatment, solvent recovery, chemical sensing, chiral separation, drug delivery, biomolecule encapsulation and separation. At this juncture, the recent experimental and computational studies are summarized herein for these multifaceted liquid phase applications to demonstrate the rapid advance in this burgeoning field. The challenges and opportunities moving from laboratory scale towards practical applications are discussed.

Tuning the Conduction Band Potential of Bi-based Semiconductors Using a Combination of Organic Ligands

Most Bi-based semiconductors are incapable of photocatalytic reduction reaction from a thermodynamic view, owing to relatively positive conduction band potentials (E_CB ). Here, a novel Bi-based metal-organic framework (Bi-MBA, MBA=4-mercaptobenzoic acid) with excellent photocatalytic reduction activities is developed. The E_CB of Bi-MBA locates at -1.38 eV, which is able to efficiently reduce O₂ , Cr^VI and CO₂ . Theoretical calculations reveal the significant contribution of organic ligand (MBA) to the conduction band. Our results provide an effective route to improve the photocatalytic reduction activities of Bi-based photocatalysts.

Porphyrin-Based Metal-Organic Framework Probe: Highly Selective and Sensitive Fluorescent Turn-On Sensor for M3+ (Al3+, Cr3+, and Fe3+) Ions

The development of porphyrin-based metal-organic frameworks (MOFs) has attracted significant interest in the scientific community in recent years because of their versatile applications particularly in optical and electronic fields. In this study, a highly selective and sensitive fluorescent turn-on sensor using a porphyrinic MOF, Tb-TCPP, is presented, which displays a 10-fold fluorescence enhancement in the presence of Al³⁺, Cr³⁺, and Fe³⁺ ions. The detection limit is in the nM region. For the Al³⁺ ion, it could be visually detected at concentrations as low as 5 mM within 15 min. Tb-TCPP could also be used as an indicator for acidic or alkaline solutions at pH values of >9 and <3. The studies on the detection mechanism illustrate that cation exchange proceed between Tb-TCPP and these M³⁺ ions, and consequently, energy transfer from TCPP to Tb³⁺ is suppressed and π*-π energy transfer of the porphyrin ligand is significantly enhanced.

Fluorescent nucleotide-lanthanide nanoparticles for highly selective determination of picric acid

A new method based on coordination polymer nanoparticles (CPNs) derived from nucleotides and Tb³⁺ ions (GMP/Tb) for the selective and sensitive determination of aqueous 2,4,6-trinitrophenol (TNP) (picric acid) is established. The fluorescence of GMP/Tb nanoparticles is effectively quenched by TNP via photo-induced charge transfer (PCT), thus achieving its selectivity toward TNP over other nitroaromatic explosives. The decreased fluorescence of GMP/Tb shows a good linear relationship to the concentrations of TNP ranging from 5.0 to 40.0 μM, and the limit of detection is 26.0 nM (5.96 ppb). The proposed GMP/Tb probe also achieves satisfactory results in real samples. The obtained recoveries of this method in river water samples are in the range 93.15-106.10%. The relative standard deviation (RSD) are 0.57 to 1.01% based on three repeated determinations. This fabricated detector provides a feasible path for determination of ppb-level TNP in natural water samples, which can help humans to avoid TNP-contaminated drinking water. Graphical abstract.

A highly stable Zn coordination polymer exhibiting pH-dependent fluorescence and as a visually ratiometric and on–off fluorescent sensor

A thermally and chemically stable Zn coordination polymer exhibiting pH-dependent fluorescence behaves as a multi-responsive fluorescent sensor for ratiometric and on–off detection of multiple analytes.

The influence of linker substitution on the fluorescence responsive sensing of isostructural coordination polymers: visual turn-on, ratiometric, and turn-off sensing in water

Linker substituents show great impacts on the luminescence properties and sensing performances of isostructural coordination polymers, causing turn-on or ratiometric sensing of Fe³⁺, Al³⁺, and Cr³⁺ and turn-off sensing of CrO₄²⁻ and Cr₂O₇²⁻.

Two-dimensional lanthanide(III) coordination polymers: solvothermal synthesis, crystal structure, and stability

Based on 2-(4-pyridyl)-terephthalate (H2pta) and oxalate ligands, two new lanthanide-containing coordination polymers (CPs), [Tb(pta)(C2O4)0.5(H2O)2)]·2H2O (1) and [Sm(pta)(C2O4)0.5(H2O)2)]·2H2O (2), have been synthesized under solvothermal conditions. The structures of both 1 and 2 have been determined by single-crystal X-ray diffraction. Infrared, elemental analysis, powder X-ray diffraction and thermogravimetric analysis data are also presented. The crystals of 1 and 2 exhibit isostructural layer-like networks, crystallizing in the triclinic space group P 1 ‾ $&#x203e;{1}$ . The layers are further stabilized and associated into 3D architectures through hydrogen bonding. Remarkably, the CPs 1 and 2 exhibit excellent water stability and remarkable thermostability with thermal decomposition temperatures of more than 420 °C.

Multifunctional fluorescence responses of phenyl-amide-bridged d10 coordination polymers structurally regulated by dicarboxylates and metal ions

Metal/carboxylate co-induced 1D → 3D phenyl-amide-bridged d¹⁰ coordination polymers that show multifunctional fluorescent responses for cations, anions and pesticides.

A water-stable terbium metal–organic framework with functionalized ligands for the detection of Fe3+ and Cr2O72− ions in water and picric acid in seawater

A novel Tb-MOF-A was fabricated by functionalized ligands and Tb³⁺, which displays high fluorescence, water stability up to 21 days and rapid, cyclic, simultaneous detection of Fe³⁺, Cr₂O₇²⁻ ions in water and picric acid in seawater.

The role of photoinduced charge transfer for photocatalysis, photoelectrocatalysis and luminescence sensing in metal–organic frameworks

Understanding PCT taking place within MOFs is crucial for designing porous photo/electrocatalysts and luminescent sensors. Unique features of PCT in MOFs and recent progress along with state-of-the-art characterization methods are discussed in the context of its applications.

Solvent triggering structural changes for two terbium-based metal–organic frameworks and their photoluminescence sensing

TbPDBA-8 and TbPDBA-9 have been obtained based on the same ligand, and have different structures and luminescence properties.