A family of Cd(II) coordination polymers constructed from 6-aminopicolinate and bipyridyl co-linkers: study of their growth in paper and photoluminescence sensing of Fe3+ and Zn2+ ions

In this work, we report on five novel coordination polymers (CPs) based on the linkage of the [Cd(6apic)2] building block [where 6apic = 6-aminopicolinate] by different bipyridine-type organic spacers, forming different coordination compounds with the following formulae: [Cd(μ-6apic)2]n (1), {[Cd(6apic)2(μ-bipy)]·H2O}n (2), {[Cd(6apic)2(μ-bpe)]·2H2O}n (3), [Cd(6apic)(μ-6apic)(μ-bpa)0.5]n (4) and {[Cd2(6apic)4(μ-tmbp)]·7H2O}n (5) [where bipy = 4,4'-bipyridine, bpe = 1,2-di(4-pyridyl)ethylene, bpa = 1,2-di(4-pyridyl)ethane (bpa) and tmbp = 1,3-di(4-pyridyl)propane]. Most of the synthesized compounds form infinite metal-organic rods through the linkage of the building block by the bipyridine-type linker, except in the case of compound 4 whose assembly forms a densely packed 3D architecture. All compounds were fully characterized and their photoluminescence properties were studied experimentally and computationally through density functional theory (DFT) calculations. All compounds display, upon UV excitation, a similar blue emission of variable intensity depending on the linker employed for the connection of the building units, among which compound 2 deserves to be highlighted for its room temperature phosphorescence (RTP) with an emission lifetime of 32 ms that extends to 79 ms at low temperature. These good photoluminescence properties, in addition to its stability in water over a wide pH range (between 2 and 10), motivated us to study compound 2 as a sensor for the detection of metal ions in water, and it showed high sensitivity to Fe3+ through a fluorescence turn-off mechanism and an unspecific turn-on response to Zn2+. Furthermore, the compound is processed as a paper-based analytical device (PAD) in which the phosphorescence emission is preserved, improving the sensing capacity toward Fe3+ ions.

A novel quinoline derivative as a highly selective and sensitive fluorescent sensor for Fe3+ detection

In this research, a novel selective and sensitive fluorescent sensor for detecting Fe³⁺ was designed and synthesized; it revealed an obvious fluorescence quenching effect upon addition of Fe³⁺, and possessed the quantitative analysis ability on account of the formation of a 1 : 1 metal–ligand complex. Furthermore, the density functional theory calculations were utilized to study the molecular orbitals as well as the spatial structure. Simultaneously, the cell experiments and zebra fish experiments verified the application value of the sensor in the biological field.

A novel selective and sensitive fluorescent sensor for detecting Fe³⁺ was designed and synthesized; it revealed obvious fluorescence quenching effect upon addition of Fe³⁺, and possessed the quantitative analysis ability on account of the formation of a 1 : 1 metal–ligand complex.

A Cd(ii)-organic framework as a highly sensitive and rapid fluorometric sensor for ascorbic acid in aqueous medium

A new Cd(ii) MOF was used as a fluorometric sensor for ascorbic acid in water, fruits, vegetables and human urine.

A series of bis-pyridyl-bis-amide-modulated metal–organic frameworks: formation, transformation and selectivity for the efficient detection of multiple analytes

A series of LMOFs have been structurally characterized, which display a remarkable fluorescence behavior and can be used as outstanding candidates in the selective sensing of multiple analytes with low limits of detection.

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·[Cd_3.5(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.

A fourfold interpenetrating diamond-like three-dimensional zinc(II) coordination polymer: synthesis, crystal structure and physical properties

Excellent fluorescence properties are exhibited by d¹⁰ metal compounds. The novel three-dimensional Zn^II coordination framework, poly[[{μ₂-bis[4-(2-methyl-1H-imidazol-1-yl)phenyl] ether-κ²N³:N^3'}(μ₂-furan-2,5-dicarboxylato-κ²O²:O⁵)zinc(II)] 1.76-hydrate], {[Zn(C₆H₂O₅)(C₂₀H₁₈N₄O)]·1.76H₂O}_n, has been prepared and characterized using IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. The crystal structure analysis revealed that the compound exhibits a novel fourfold interpenetrating diamond-like network. This polymer also displays a strong fluorescence emission in the solid state at room temperature.

A new two-dimensional CoII coordination polymer based on bis[4-(2-methyl-1H-imidazol-1-yl)phenyl] ether and biphenyl-4,4′-diyldicarboxylic acid: synthesis, crystal structure and photocatalytic degradation activity

A novel two-dimensional CoII coordination framework, namely poly[(μ2-biphenyl-4,4′-diyldicarboxylato-κ2 O 4:O 4′){μ2-bis[4-(2-methyl-1H-imidazol-1-yl)phenyl] ether-κ2 N 3:N 3′}cobalt(II)], [Co(C14H8O4)(C20H18N4O)] n , has been prepared and characterized by IR, elemental analysis, thermal analysis and single-crystal X-ray diffraction. The crystal structure reveals that the compound has an achiral two-dimensional layered structure based on opposite-handed helical chains. In addition, it exhibits significant photocatalytic degradation activity for the degradation of methylene blue.

Synthesis, Structure and Fluorescence Properties of Two Metal-Organic Frameworks Based on a Benzimidazole-Derived Ligand

The luminescent complexes [Cd(BIMP)2(NDC)2]n and [Zn(BIMP)2(NDC)]n (where (3-BIMP) = 3-(1H-benzoimidazol-2-yl)pyridin-2(1H)-one and NDC = 2,6-naphthalenedicarboxylic acid) have been synthesised under hydrothermal conditions and their crystal structures determined. [Cd(BIMP)2(NDC)2]n exhibited a 1D → 2D → 3D framework structure and [Zn(BIMP)2(NDC)]n has a 3D porous structure. Under the same excitation energy (λex = 389 nm), [Zn(BIMP)2(NDC)]n showed a stronger fluorescence emission than the free 3-BIMP ligand, the NDC ligand and [Cd(BIMP)2(NDC)2]n.

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.

The conformational behavior of multivalent tris(imidazolium)cyclophanes in the hybrids with metal (pseudo)halides or polyoxometalates

Three 3D imidazole or benzimidazole-bearing cages as trivalent cationic templates react with metal (pseudo)halides or polyoxometalates to obtain a series of different organic–inorganic hybrids in which the cages exhibit breathing behavior of expansion and contraction.

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

Highly stable 3D Ln-MOFs were constructed. The Eu-MOF shows good luminescence properties while the Dy-MOF shows a typical single-molecule magnetic behavior with a slow relaxation of magnetization.

Selective chiral symmetry breaking and luminescence sensing of a Zn(ii) metal–organic framework

The non-random handedness excess is observed in a chiral metal–organic framework [(CH₃)₂NH₂]₅[Zn_1.5(Zn₃O)(TATAT)₂]·9DMF·17H₂O (1, 1P ≫ 1M) without any chiral sources.

Cadmium(ii) carboxyphosphonates based on mixed ligands: syntheses, crystal structures and recognition properties toward amino acids

Three novel cadmium(ii) carboxyphosphonates have been hydrothermally synthesized. The luminescence properties of compounds 1–3 have been investigated. Meanwhile, the excellent abilities of compounds 2 and 3 for selective recognition of tryptophan (Trp) have been demonstrated.