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 DCHB2- 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 (KSV = 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.

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+.

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.

Cd-Based Metal-Organic Framework Containing Uncoordinated Carbonyl Groups as Lanthanide Postsynthetic Modification Sites and Chemical Sensing of Diphenyl Phosphate as a Flame-Retardant Biomarker.

With the judicious selection of an appropriate semirigid polycarboxylate, 2,5-bis(3',5'-dicarboxylphenyl)benzoic acid (H5bdba), and an inorganic metal ion, a novel anionic framework, {[NH2(CH3)2]2·[Cd3.5(bdba)(Hbdba)(H2O)1.5]}n (Cd-MOF), has been synthesized solvothermally. Single-crystal measurement results show that the prepared Cd-MOF features a three-dimensional structure containing two types of one-dimensional channels, and as we expected, there exist accessible uncoordinated -COOH groups on Hbdba pointing toward the rhombus channels. Powder X-ray diffraction and thermogravimetric analysis measurements were performed for the thermal and chemical stability analysis of Cd-MOF. In addition, the lanthanide(III)-functionalized hybrids, Ln(III)@Cd-MOF, were initially prepared by coordinated postsynthetic modification to incorporate luminescent Ln(III) ions into the structure. The luminescence properties of the hybrids are studied, and the results show notable and specialized fluorescent sensitization of Cd-MOF to Tb(III) ions. Moreover, the Tb(III)@Cd-MOF hybrid with outstanding fluorescence properties was developed as a highly sensitive and selective luminescent probe for the biomarker diphenyl phosphate (DPP) based on multiquenching effects. Tb(III)@Cd-MOF is the first case to realize the detection of urinary DPP through lanthanide metal-organic framework fluorescence spectrometry and shows practical detection potential.

Methylated Eu(III) metal-organic framework as a fluorescent probe for constructing molecular logic gates and monitoring of F-, I-, and S2.

A novel fluorescent and electron-deficient hybrid, N-methylated [Eu (pddb)phen(ox)0.5]n (Eu-MOF-Me) has been prepared via post-synthetic modification. Considering its special luminescent properties and cationic framework, Eu-MOF-Me is developed as a visualized fluorescent probe. Notably, water-stable Eu-MOF-Me exhibits advantages like good structural and fluorescent stability in a wide range of pH value (3.39-10.86), excellent identification ability for F-, I-, and S2- (it can easily distinguish F- and I- from other halogen ions and can realize naked eye identification of F-, I-, and S2-), relatively low detection limits (6.61 µM for S2-, 7.57 µM for F-), and reusability. More importantly, it has been utilized for the construction of a Boolean logic gate system. In this system, Eu-MOF-Me serves as the gate, by taking F-, I-, and S2- as the inputs and fluorescence emission bands (UV380, B437, and R612) as the outputs; some primary logic gates (NOR, IMP, YES, NOT) and the combination of them have been realized. Moreover, we achieved a cascaded logic gate (NOR+OR). For further application, a molecular computing keypad-lock security system has been obtained. Graphical abstract A novel fluorescent and electron-deficient hybrid named Eu-MOF-Me has been prepared via post-synthetic methylation. Considering its special luminescent properties and cationic framework, Eu-MOF-Me was developed as a fluorescent probe for the visual monitoring of important anions. In addition, it was used for the construction of Boolean logic library and a keypad-lock system was achieved.

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

A novel three-dimensional microporous framework, [Tb(pddb)phen(ox)0.5] n (Tb-MOF), was synthesized hydrothermally with V-shaped 4,4'-(pyridine-2,6-diyl)dibenzoic acid (H2pddb), oxalate (ox), and 1,10-phenanthroline (phen). The framework of Tb-MOF features one-dimensional channels functionalized with pyridine-N Lewis base groups and the absence of coordinated and lattice water molecules in the structure. The Tb-MOF exhibits high thermostability (up to 385 °C) and chemical stability in a wide pH range (4-11) and common organic solvents as well as boiling water. The luminescence investigations of the Tb-MOF in common solvents, water with different pH values, and inorganic ions were performed. Results show that the Tb-MOF has high luminescence stability and the ability to probe Fe3+ ions. Significantly, the Tb-MOF with particularly high water stability can be first developed as a highly selective and sensitive luminescent sensor for the biomarker 2-thiazolidinethione-4-carboxylic acid (TTCA) via fluorescence quenching. The low detection limit (1 ppm), reusability, and high antidisturbance together make the Tb-MOF become a promising sensor for the practical detection of TTCA in urine systems, and for the first time realize the detection of urinary TTCA through fluorescence spectrometry based on an Ln-MOF sensor.

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

By application of a straightforward postsynthetic modification strategy, a luminescent lanthanide-based MOFs hybrid material, Tb(III)@MOF-SO3-, is first fabricated by loading Tb(III) ions into the pores of Zn-based MOF-SO3-. This hybrid system is constructed on notable and specific luminous sensitization of MOF-SO3- to Tb(III) ions. The further study shows that bi-metal-loaded Eu(III)/Tb(III)@MOF-SO3- exhibits a Tb(III)-induced luminescence of Eu(III) ions, and the emissions of it all fall in the white region by altering the ratio of Eu(III)/Tb(III) ions and the excitation wavelengths. A kind of white-lighting thin film based on Eu(III)/Tb(III)@MOF-SO3- exhibits dazzling white light when excited at 295 nm ( X = 0.338, Y = 0.323). Furthermore, the Tb(III)@MOF-SO3- is first developed as a fluorescence sensor specifically toward biomarker of benzene, trans, trans-muconic acid ( tt-MA), based on fluorescence quenching. This reusable sensor with high water tolerance and photostability displays excellent selectivity and sensitivity with a detection limit as low as 0.1 ppm, while being provided with the high antijamming of other urinary chemicals. These results make the sensor has the potential for the practical detection of tt-MA in a urine system. The possible quenching mechanisms are also investigated in detail.

[Fluorescence Properties and the Detection of Nitrobenzene of Lanthanides Complex with 3,4-Thiophenedicarboxylic Acid and 1,10 Phenanthroline].

3,4-thiophenedicarboxylic acid (3,4-H2tdc) as the first ligand, 1,10-phenanthroline (phen) as the auxiliary ligand, three complexes Ln2(Htdc)2(tdc)2(phen)2(H2O)4(Ln=Eu 1, Gd 2, Tb 3) were synthesized with hydrothermal method. Single-crystal X-ray diffraction analysis reveals that complexes 1-3 were isostructural crystallize and both of complexes are binuclear molecules. In the complexes 1-3, the coordination number is nine. Each metal is bound to two 3, 4-tdc ligand, one 3,4-Htdc ligand, one phen and two water molecule. Complexes 1 and 3 display the red and green light under UV lamp, corresponding the characteristic peaks from 619 nm (5D0→7F2) and 545 nm (5D4→7F5). Complex 2 expresses a broad band at 425 nm is attributed to π*→π transition. Furthermore, under the excitation wavelength of 329 nm, the effects of different solvents on complex 1 was discussed and complex 1 could be a potential luminescent probe for detecting nitrobenzene through fluorescence quenching mechanism.

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.

Isostructural lanthanide-based metal-organic frameworks: structure, photoluminescence and magnetic properties.

A series of the anhydrous lanthanide-based metal-organic frameworks (Ln-MOFs) were successfully synthesized under hydrothermal conditions of Ln(iii) ions with 3,4'-oxybis(benzoate) (3,4'-oba), oxalate (ox) and 1,10-phenanthroline (phen). Structural analyses revealed that they are isostructural 3D open-frameworks with the formula of [Ln(3,4'-oba) (phen)(ox)0.5]n (Ln = Sm for 1, Eu for 2, Gd for 3, Tb for 4, and Dy for 5) and the topology of {33·43·58·6}. Within the 3D structure, the [LnO6N2] units are bridged by ox to form [Ln2ox] dimers and then are further connected by 3,4'-oba ligands. These complexes feature high chemical stabilities in common solvents, boiling water, and acidic (pH = 3) and alkaline (pH = 13) solutions and high thermal stability even up to 400 °C. The photoluminescence and magnetic properties were studied. Especially, 2 shows bright red emission with a high luminescence efficiency of 40.51%. We mainly discuss the luminescence properties of 2 in common solvents and inorganic ions. It shows luminescence stability in common solvents and the ability to detect ammonia and Fe3+ ions under a long excitation wavelength (350 nm). Significantly, magnetic studies reveal that the Dy-MOF, 5, shows a typical single-molecule magnetic behavior. Under zero dc field, compound 5 shows temperature and frequency dependent out-of-phase (χ''M) signals, indicating the existence of slow magnetic relaxation.

Correction: Isostructural lanthanide-based metal-organic frameworks: structure, photoluminescence and magnetic properties.

Correction for 'Isostructural lanthanide-based metal-organic frameworks: structure, photoluminescence and magnetic properties' by Li-Lin Luo et al., Dalton Trans., 2018, 47, 925-934.

Temperature-induced 1D lanthanide polymeric frameworks based on Ln(n) (n = 2, 2, 4, 6) cores: synthesis, crystal structures and luminescence properties.

The hydrothermal reaction of the same reactive system containing Ln(NO3)3·6H2O, tetrafluorophthalic acid (H2TFPht), and 1,10-phenanthroline (phen) at different temperatures yielded coordination polymers, [Ln2(TFPht)3(phen)2(H2O)2]·H2O (Ln = Sm 1, Eu 2, Gd 3, Tb 4, Dy 5; at 120 °C), La(TFPht)(TFBA)(phen)(H2O) (6; at 160 °C), Ln3(TFPht)4(TFBA)(phen)3(H2O)3 (Ln = Dy 7, Tb 8, Yb 9; at 160 °C), and Ln2(TFBA)6(phen)2 (Ln = Eu 10, Tb 11; at 180 °C). 2,3,4,5-Tetrafluorobenzoic acid (TFBA) was produced from the decarboxylation of TFPht. X-ray structural analysis reveals that these compounds contain different structural motifs. Complexes 1-5 exhibit zigzag chain structures based on the center-related tetranuclear [Ln4] as SBUs (Secondary Building Units) with two crystallographically independent Ln(3+) ions. Complex 6 contains a double chain structure with center-related binuclear [La2] as SBUs. Complexes 7-9 show single chain structures involving center-related hexanuclear [Ln6] as SBUs with three crystallographically independent Ln(3+) ions. Complexes 10 and 11 have ribbon chain structures involving binuclear [Ln2] as SBUs with two crystallographically independent Ln(3+) ions. The photoluminescence properties of complexes 1-5 were studied. The Eu(3+) and Tb(3+) complexes exhibit bright red and green emissions with quantum yields of 15.87% for 2 and 23.82% for 4. The two-component Dy:Eu- and three-component Gd:Dy,Eu-doped complexes provided white light emission. Moreover, 2 could be a potential luminescent probe for detecting nitrobenzene and Ni(2+) ion through significant fluorescence decrease of Eu(3+).

A Cd(II)-based metal-organic framework as a luminance sensor to nitrobenzene and Tb(III) ion.

A Cd(II)-based metal-organic framework, [Cd2(DPDC)2(BTB)]∞ (Cd-MOF, DPDC = 2,2'-diphenyldicarboxylate and BTB = 1,4-bis(1,2,4-triazol-1-yl)butane) was successfully constructed via a hydrothermal reaction. Structural analysis shows that the synthesized Cd-MOF is a three-dimensional (3D) architecture crystallized in the hexagonal system with a chiral space group P61. Powder X-ray diffraction experiments and thermogravimetric analysis reveal that the constructed Cd-MOF has a high chemical and thermal stability. A study of additional mechanical properties indicates that it exhibits a moderate stiffness with the average values of Young's modulus (E) and H as 11.3(2) and 0.9(7) GPa, respectively. The luminescence properties of the Cd-MOF were further studied. The result shows that it could be an effective sensor to the organic nitrobenzene molecule via a strong quenching effect, and also to the inorganic Tb(III) ion by a strong green emission effect. Moreover, when loading bimetal ions (Eu(III) and Tb(III) into the Cd-MOF/methanol suspension, tunable visible luminescence can also be achieved by carefully adjusting the excitation wavelengths.

[Concentrations and distribution of tetracycline antibiotics in vegetable field soil chronically fertilized with manures].

Occurrence of antibiotics in the soils substantially fertilized with antibiotics-enriched animal manures is very of concern. This paper investigated the concentration and distribution of four tetracycline antibiotics in soils from vegetable field chronically fertilized with manures in subtropical area using solid-phase extraction followed by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-MS/MS). The sum concentrations of four tetracycline compounds ranged from 1.35 microg/kg to 22.52 microg/kg with an average of 7.35 microg/kg. There were thirty one to one hundred percent of the soil samples were detected with average concentrations of 0.63- 3.11 microg/kg for four tetracycline compounds which dominated mostly with oxytetracycline and secondly with deoxytetracycline. Composition and levels of tetracycline compounds varied obviously in both horizontal and vertical soils. The concentration of tetracycline compounds in soil profile decreased rapidly with the depth and some of the compounds were still detected in 60 to 80 centimeter depth of soil. It is concluded that tetracycline antibiotics in soils from vegetable field chronically fertilized with manures in subtropical area were generally lower and less ecotoxic risk for soil ecosystem. But it should not be ignored in view of combined toxic effect and resistance of various compounds.