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Metal–organic frameworks (MOFs) provide an ideal platform for the assembly of chromophores and thus show wide potential applications in optoelectronic devices. The spatial arrangement and interaction of the incorporated chromophores play a key role in the generation of coherent optical and electronic properties. In this work, two series of benzo-(1,2;3,4;5,6)-tristhiophene (BTT) based Ln–MOFs (Ln-1s and Ln-2s) were synthesized. These two series of MOFs present different assembly states of BTT chromophores, that is, BTT-containing ligands exist as separated monomers in Ln-1s but gather as dimers in Ln-2s. From the comparison between these two series of MOFs and theoretical calculations, we show for the first time that this chromophore assembly state difference could affect the crystallization selectivity of MOFs towards different Ln3+ ions. In addition, the interaction between BTT chromophores in the dimer also leads to the red-shifted photoluminescence and enhanced photocurrent of Ln-2s relative to those of Ln-1s. The results of this work demonstrate the multiple functions of interchromophoric interactions in the structures and optoelectronic properties of MOFs. [ABSTRACT FROM AUTHOR]

Paraquat is a highly toxic cationic agrochemical, and distinguishing it from other electron-deficient species is still a pending issue via fluorescence detection. In this work, taking advantage of the structural similarity, pyrene-based MOFs were applied in the analysis of paraquat in both aqueous and organic phases, and an anionic ligand was further introduced into the structures of MOF precursors in the hope of using electrostatic attraction to improve the sensing performance. Experimental observation showed that the backbone structure of the MOF has a profound effect on the response sensitivity, and the improvement by the anionic ligand depends heavily on the medium of the analysis. An anionic ligand installed derivative was screened for the detection of paraquat in the organic phase. The recognition of paraquat from a series of electron deficient agrochemicals and nM-scale detection limits were achieved in this system. [ABSTRACT FROM AUTHOR]

Polychlorophenols are widely distributed priority pollutants, but fluorescent sensor targeting of them has rarely been reported. In this work, a dye@MOF composite with dual emission was screened out for the ratiometric fluorescent detection of the two isomers of tetrachlorobenzenediol (o- and p-TCBDs). These two analytes could restrict the vibration of the MOF host through hydrogen bonds and thus enhance its emission, while the fluorescent dye guest was quenched via a photo-induced electron transfer mechanism. This sensor exhibited a good quantification ability (over 100 μM linear response ranges and sub-μM scale DLs) and selectivity (immune to the interference from other chlorophenols and chloroquinones) for TCBDs. It is interesting to observe that, in spite of the similar structures of the two analytes, using the overall intensity change of the two emission bands of the sensor as a criterion, they could be clearly discriminated over the whole tested concentration range. This sensor was successfully applied to TCBD analysis in clinical samples. [ABSTRACT FROM AUTHOR]

Aluminum is a widely distributed element with potential harm to human health, and the analysis of phenylpyruvic acid (PPA) is also routine in clinical uroscopy for metabolic disorders. In this work, we synthesized a UiO-66-backboned MOF, UiO-66-(OH)2, to construct an "off–on–off" platform for the sequential fluorescence detection of Al3+ and PPA. With incorporated hydroxyl groups, this MOF could capture Al3+ ions in aqueous solution and show enhanced fluorescence response through an excited-state intramolecular proton transfer mechanism. The binding affinity of PPA to Al3+ is stronger than that to the MOF; therefore, the further addition of this compound to UiO-66-(OH)2–Al3+ extracts the adsorbed Al3+ and restores the original weak emission of the MOF. UiO-66-(OH)2 exhibited good selectivity and sensitivity (DL = 47 nM for Al3+ and 100 nM for PPA) in both steps of detection and was successfully applied to the analysis of PPA in artificial urine. [ABSTRACT FROM AUTHOR]

With multiple signal channels, array sensing can effectively improve detection selectivity, but at the cost of increasingly complex analytical operation and decreased repeatability. Herein, we propose a "single MOF-based sensor array" in which a white-light-emitting MOF is used to provide multiple response channels with its manifold emission bands to overcome these drawbacks; the potential of this strategy was verified by the discrimination of berberine homologues (a sub-class of isoquinoline-type alkaloids). A white-light-emitting MOF was synthesized by the incorporation of three luminescent ligands into the UiO-66 backbone. With distinct response behaviors, these components could produce a three-channel signal pattern for the analyte. Thus, this MOF realized array sensing with a single measurement of its spectrum. Its discrimination limit for berberine homologues was as low as 2 μM, and by combination with chemical titration, this MOF could identify samples with unknown concentrations. This work demonstrates the advantage of white-light-emitting MOFs in array sensing. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have become an important class of fluorescence sensing materials. In spite of the application value of multi-responsive MOF sensors and the great efforts made on them, the simultaneous detection of multiple analytes in mixtures is still a big challenge due to the cross interference among different analytes. The incorporation of multiple responsive components to increase the signal channels is a promising way to solve this problem. In this work, a stable and dual emissive MOF was constructed by the incorporation of Tb3+ and 2-aminoterephthalate into the backbone of UiO-66. This MOF was used for the analysis of the two isomers of tetrachlorobenzoquinone (o- and p-TCBQs). It was observed that o-TCBQ could give a ratiometric fluorescence signal, while p-TCBQ quenches all the emission peaks equally. Because the signals of these two compounds are in different forms and could be split, this MOF was successfully applied to the simultaneous quantification of o- and p-TCBQs in their mixtures. [ABSTRACT FROM AUTHOR]

The sensing performance of metal–organic frameworks (MOFs), a novel kind of crystalline fluorescent sensing materials, would be profoundly affected by their backbone structures. The current understanding about the backbone effect is limited to the modulation of analyte accommodation through pore structures. Herein, three topologically different pyrene-based MOFs, including NU-1000, NU-901 and ROD-7, were investigated as potential fluorescent sensors for polycyclic aromatic hydrocarbons (PAHs). Although these MOFs are constructed by the same photoactive component, they exhibited distinct sensing behaviors. NU-1000 gave different forms of fluorescent response to acenaphthylene, pyrene and fluoranthene with detection limits at the ng L−1 level. In contrast, NU-901 and ROD-7 were unresponsive to all tested PAHs. Experimental and computational investigations illustrate that this distinction is due to the variance in the excited state energy. The strong inter-ligand interaction in NU-901 and ROD-7 lowers their excited state energy and thus thermodynamically inhibits the photo-induced electron transfer and excimer/exciplex formation, which works in the NU-1000 system. This work proves for the first time that the topological structure of MOFs could affect their sensing performance in an energetic way. [ABSTRACT FROM AUTHOR]

Antibiotics have been noted as an important class of emerging contaminants in the environment. Metal–organic frameworks (MOFs), which have been intensely investigated as a novel kind of sensing material, have been tentatively applied to the detection of antibiotics in recent years. In this work, a nanoscale MOF (In-sbdc) with a strong (quantum yield = 13%) and stable emission in water was synthesized. With its effective spectral overlap with tetracyclines, adsorption preconcentration and the usage of a masking agent, In-sbdc gave sensitive responses to a series of tetracycline antibiotics (tetracycline, chlorotetracycline and oxytetracycline) with detection limits of 0.28–0.30 μM, but another eight tested kinds of antibiotics did not cause a remarkable change in its emission (＜10% of the response caused by an equal amount of tetracyclines). This MOF-based sensing system was successfully applied to tetracyclines detection in a series of actual water and food samples. [ABSTRACT FROM AUTHOR]

An Fe(ii) metal–organic framework with micro-sized particles was synthesized. This material could serve as a visible responsive photo-Fenton catalyst to induce the mineralization of a series of organophosphates, and exhibited high activity, high stability and wide pH tolerance. The degradation mechanism of organophosphates in this photocatalytic system was illustrated by different methods. [ABSTRACT FROM AUTHOR]

As novel fluorescent-sensing materials, metal-organic frameworks (MOFs) have shown great potential in environmental monitoring. However, most of the researches are limited to traditional pollutants, whereas the application of MOFs to the detection of the pollutants with more complicated structures, such as endocrine disrupting chemicals (EDCs), has rarely been explored. The difficulties faced in the sensing of EDCs include their electronic stability and the structural similarity among homologues, which could be overcome by the incorporation of enzymatic reaction. In this work, the first example of enzyme-assisted MOF-fluorescent-sensing was developed for the analysis of diethylstilbestrol (DES, a synthetic estrogen). In this system, DES is first oxidized by HRP/H2O2 quantitatively to its quinone form, and then the quinone product is selectively captured by a stilbene based luminescent MOF to induce fluorescence response. By the tandem sensitization and filtration of enzymatic reaction and MOF adsorption, this method shows high sensitivity (DL=89 n m) and can distinguish DES from other similar-structured EDCs. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) are emerging in recent years as a kind of versatile fluorescent sensing materials, but their application to enzyme assays has rarely been studied. Here, the first example of a MOF-based label-free enzyme assay system is reported. A luminescent MOF was synthesized and applied to the activity analysis of polyphenol oxidase (PPO). With its distinct responses to the phenolic substrate and o-quinone product, this MOF could transduce the extent of PPO-catalyzed oxidation to fluorescence signal and enable the real-time monitoring of this reaction. Wide substrate adaptability and high sensitivity (detection limit=0.00012 U mL−1) were exhibited by this method, which meets the requirement of common bioanalysis. Interestingly, by the comparison with molecular capturing reagents, the heterogeneous nature of this MOF-based assay effectively preventing the interaction with the enzyme was proven, thus ensuring the authenticity of results. [ABSTRACT FROM AUTHOR]

Two chemosensors with large hexaazatriphenylene-pyrene chromophores were designed and synthesized. Both of them exhibit a selective fluorescence quenching response to Hg2+ in aqueous acetonitrile solution, and their detection limits are lower than the toxic level of Hg2+. Additionally, these compounds were successfully used for test paper detection. [ABSTRACT FROM AUTHOR]

Two luminescent coordination polymers were constructed with a fluorescent ligand. The emissions of these compounds could be effectively and selectively quenched by acetone, showing their potential as acetone sensors. The formation of a coordination polymer structure is proven to be responsible for their strong emission and sensing properties. [ABSTRACT FROM AUTHOR]

With a flexible aromatic ligand, bis-(3,5-dicarboxy-phenyl)terephthalamide (H4L), two metal–organic frameworks, Cd(L)·(HDMA)2(DMF)(H2O)3 (1) and Zn(L)·(HDMA)2(DMF)(H2O)6 (2), were synthesized using a solvothermal method. Both 1 and 2 possess a 3D open framework. These two compounds exhibit strong photoluminescence in suspensions, and their luminescence could be efficiently and selectively quenched by a series of nitroaromatics. Thus, 1 and 2 could be used as excellent luminescent probes for nitroaromatic explosives. Additionally, 1 and 2 could also be utilized as the sensing platforms for DNA strands, which is attributed to their different affinities for single- and double-stranded DNAs. With this method, 0.05 nM of target DNA could be detected, and the selectivity could be down to a single nucleotide mismatch. This work shows the potential of MOFs for the sensing of versatile chemicals. [ABSTRACT FROM AUTHOR]

A luminescent two-dimensional (2D) coordination polymer is demonstrated to be a selective sensing material for the straightforward detection of nitrobenzene via a redox fluorescence quenching mechanism. [ABSTRACT FROM AUTHOR]

From the condensation of the Schiff base (HMBP–PHEN) prepared from 5-methyl-2-hydroxybenzophenone (HMBP) and o-phenylenediamine (PHEN) in the 1:1 mole ratio with substituted salicylaldehydes, a series of homo-binuclear metal complexes with non-symmetrical tetradentate Schiff base ligands have been synthesized by the template method. These new types of binuclear metal complexes have been characterized by elemental analyses, IR, UV, FAB and EPR spectroscopy and magnetic properties. [ABSTRACT FROM AUTHOR]

Cobalt(III) complexes containing both optically active tetradentate Schiff base ligands, (SB=Salen, MeOSalen, t-Bu-Salen) with axial ligands (L) [Co(SB)L2]ClO4 (L=imidazole (Im), 2-methylimidazole (2-MeIm), 1-methylimidazole (MeIm)) have been prepared and characterized. In addition, the crystal structures of [Co(Salen)(MeIm)2]ClO4 (1c), [Co(MeOSalen)(MeIm)2]ClO4 (2c), and [Co(t-Bu-Salen)(MeIm)2]ClO4 (3c) have been determined by X-ray structure analysis. The properties of these hexacoordinate complexes, such as electronic absorption, circular dichroism spectra, and 1H NMR spectra, have been studied. [Copyright &y& Elsevier]

A MOF ‐ based label ‐ free enzyme assay was designed in this work. To analyze polyphenol oxidase (PPO) activity, a luminescent MOF in which the emission could be selectively quenched by the o ‐ quinone product was synthesized. With it, the kinetics of PPO ‐ catalyzed oxidation could be reflected with the fluorescence signal. This method exhibits the advantages of high sensitivity, wide substrate adaptability, and minimal effects on the enzymatic reaction. More information can be found in the Full Paper by W. ‐ J. Ruan, et al. on page 6562 ff. [ABSTRACT FROM AUTHOR]

Graphical abstract Luminescent MOF nanosheets with thicknesses of only 4 nm were used as fluorescent sensor to construct the sensing systems of H 2 O 2 and glucose and activity assay of glucose oxidase. Highlights • A cation-exchange mediated sonication method is used to exfoliate MOF to nanosheets. • The thickness of MOF nanosheets is only 4 nm, ensuring their good dispersibility. • With MOF nanosheets as sensor, an enzyme assisted method is designed to analyze H 2 O 2. • This method can be advanced by multi-enzyme catalysis to sense H 2 O 2 related species. • A glucose detection method and a glucose oxidase assay are developed based on it. Abstract 2D metal-organic framework (MOF) nanosheets have emerged as a novel kind of sensing materials due to the large external surface area and accessible active sites on the surface. In this work, we successfully prepared luminescent MOF nanosheets (In-aip) with thickness of 4 nm by the cation-exchange mediated sonication of a 2D connected anionic MOF. Using In-aip as fluorescent sensor, an enzyme assisted system was established for the analysis of H 2 O 2 with the quenching effect of the oxidation product on its emission. The nanosheet morphology of In-aip ensures its high capture efficiency of unstable intermediate, so high sensitivity was achieved (detection limit = 0.87 μM). With high sensitivity and wide quantitative range, this H 2 O 2 sensing system could be used as a universal platform for the analysis of H 2 O 2 related biomolecules and enzymes. By multi-enzyme cascade catalysis, a detection method of glucose and an activity assay of glucose oxidase were developed based on it. This work is the first example of using luminescent MOF nanosheets to bioanalysis and shows their wide application potential. [ABSTRACT FROM AUTHOR]

Highlights: [•] DFT calculations on porphine/C60 bisadducts were carried out. [•] Pyrrolidine ring appended on C60 has influence on its interaction with porphine. [•] Interaction was found between pyrrolidine ring appended on C60 and porphyrin. [•] Charger transfer between pyrrolidine ring and porphine was observed. [•] The red shift of absorption was predicted for fullerene/porphine complexes. [ABSTRACT FROM AUTHOR]

Abstract: Two C 2-symmetrical hexaazatriphenylene (HAT) derivatives, 2,3-diphenyl-6,7,10,11-tetra(pyridin-2-yl)dipyrazino[2,3-f:2′,3′-h]quinoxaline (1) and 2,3,6,7-tetraphenyl-10,11-di(pyridin-2-yl)dipyrazino[2,3-f:2′,3′-h]quinoxaline (2), were designed and synthesized by the condensation reaction of 1,2-diamines and 1,2-diketones. Both compounds 1 and 2 exhibit sensitive, ratiometric and colorimetric fluorescence selectivity for Zn2+ ion over alkali ions, alkaline earth ions and a wide range of transition metal ions upon excitation at 350nm in acetonitrile/water. The interactions between 1 or 2 and Zn2+ can be observed by naked eyes with an obvious color change of the solution from colorless to yellow. For fluorescence intensity of 2 toward Zn2+, a good linearity (correlation coefficient R 2=0.993) was established with a detection limit of 0.095μM, which is more sensitive than that of 1 (0.2μM). The binding modes of the free ligands 1 and 2 with Zn2+ are discussed in context to their photophysical and electrochemical properties as well as single X-ray crystallographic structures of 1, 2 and 1-Zn. [Copyright &y& Elsevier]

Metal-organic frameworks (MOFs) provide an ideal platform for the assembly of chromophores and thus show wide potential applications in optoelectronic devices. The spatial arrangement and interaction of the incorporated chromophores play a key role in the generation of coherent optical and electronic properties. In this work, two series of benzo-(1,2;3,4;5,6)-tristhiophene (BTT) based Ln-MOFs (Ln-1s and Ln-2s) were synthesized. These two series of MOFs present different assembly states of BTT chromophores, that is, BTT-containing ligands exist as separated monomers in Ln-1s but gather as dimers in Ln-2s. From the comparison between these two series of MOFs and theoretical calculations, we show for the first time that this chromophore assembly state difference could affect the crystallization selectivity of MOFs towards different Ln 3+ ions. In addition, the interaction between BTT chromophores in the dimer also leads to the red-shifted photoluminescence and enhanced photocurrent of Ln-2s relative to those of Ln-1s. The results of this work demonstrate the multiple functions of interchromophoric interactions in the structures and optoelectronic properties of MOFs.