A stable and sensitive Au metal organic frameworks resonance Rayleigh scattering nanoprobe for detection of SO3 2- in food based on fuchsin addition reaction

A stable Au metal organic frameworks (AuMOF) nanosol was prepared. It was characterized by electron microscopy and molecular spectral techniques. In pH 6.8 PBS buffer solution, AuMOF nanoprobes exhibit a strong resonance Rayleigh scattering (RRS) peak at 330 nm. After basic fuchsin (BF) adsorbing on the surface of AuMOF, the RRS energy of the nanoprobe donor can be transferred to BF receptor, resulting in a decrease in the RRS intensity at 330 nm. Both sulfite and BF taken place an addition reaction to form a colorless product (SBF) that exhibit weak RRS energy transfer (RRS-ET) between AuMOF and SBF, resulting in the enhancement of the RRS peak. As the concentration of SO3 2-increases, the RRS peak is linearly enhanced. Thus, a new and sensitive RRS-ET method for the detection of SO3 2- (0.160-5.00 μmol/L) was developed accordingly using AuMOF as nanoprobes, with a detection limit of 0.0800 μmol/L. This new RRS method was applied to determination of SO3 2- in food and SO2 in air samples. The recoveries of food and air samples were 97.1-106% and 92.9-106%, and the relative standard deviation (RSD) was 2.10-4.80% and 2.10-4.50%, respectively.

Visual Hg(II) sensing in aqueous solution via a new 2,5-Bis(4-pyridyl)thiazolo[5,4-d]thiazole-based fluorescence coordination polymer

A new fluorescence coordination polymer [Zn(Py₂TTz)(5-OH-IPA)]_n (1) (Py₂TTz = 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole, 5-OH-IPA = 5-hydroxyisophthalic acid dianion) was synthesized, which exhibited the characteristics of fluorescence quenching and bathochromic shift toward Hg(II) in aqueous solution at pH 7.00. Mechanism study showed that the interactions between Hg(II) ions and Py₂TTz ligands in 1 were responsible for the fluorescence emission change. Thanks to the specific interactions between 1 and Hg(II), excellent selectivity was achieved both in aqueous solution and in solid test paper. The detection limit of 1 for Hg(II) sensing was 125.76 nmol L^-1 and a linear rang was 1.00-10.00 μmol L^-1. More importantly, satisfactory recovery and accuracy of 1 for Hg(II) sensing were also obtained in buffer-free real water samples.

Coordination Polymers as a Functional Material for the Selective Molecular Recognition of Nitroaromatics and ipso-Hydroxylation of Arylboronic Acids

We report the synthesis and structural characterization of two coordination polymers (CPs), namely; [{Zn(L)(DMF)₄ } ⋅ 2BF₄ ]_α (1) and [{Cd(L)₂ (Cl)₂ } ⋅ 2H₂ O]_α (2) (where L=N² ,N⁶ -di(pyridin-4-yl)naphthalene-2,6-dicarboxamide). Crystal packing of 1 reveals the existence of channels running along the b- and c-axis filled by the ligated DMF and lattice anions, respectively. Whereas, crystal packing of 2 reveals that the metallacycles of each 1D chain are intercalating into the groove of adjacent metallacycles resulting in the stacking of 1D loop-chains to form a sheet-like architecture. In addition, both 1 and 2 were exploited as multifunctional materials for the detection of nitroaromatic compounds (NACs) as well as a catalyst in the ipso-hydroxylation of aryl/heteroarylboronic acids. Remarkably, 1 and 2 showed high fluorescence stability in an aqueous medium and displayed a maximum 88% and 97% quenching efficiency for 4-NPH, respectively among all the investigated NACs. The mechanistic investigation of NACs recognition suggested that the fluorescence quenching occurred via electron as well as energy transfer process. Furthermore, the ipso-hydroxylation of aryl/heteroarylboronic acids in presence of 1 and 2 gave up to 99% desired product yield within 15 min in our established protocol. In both cases, 1 and 2 are recyclable upto five cycles without any significant loss in their efficiency.

Recent progresses in luminescent metal-organic frameworks (LMOFs) as sensors for the detection of anions and cations in aqueous solution

The discharge of excessive metal ions and anions into water bodies leads to the serious pollution of water and environment, which in turn has a certain impact on industry, agriculture, and human life. Because of the unique advantages of luminescent metal-organic frameworks (LMOFs), they have been successfully explored as various fluorescent probes to quickly and effectively detect these pollutants. This perspective not only introduces the design strategy and classification of LMOFs, especially the construction methods of water-stable LMOFs, but also reports the latest progresses in some LMOFs between 2016 and 2020 as well as expounds the mechanisms of LMOFs for detecting anions and cations. Moreover, the luminescence properties of LMOFs are related to the selection of metal ions, the structure of organic ligands, the pore size, and the interaction of guest molecules. Finally, the further development of LMOFs is summarized and prospected in this field.

A multi-functional two-dimensional Zn(ii)-organic framework for selective carbon dioxide adsorption, sensing of nitrobenzene and Cr2O72−

A novel two-dimensional coordination polymer {[(CH3)2NH2][Zn2(L)2]·DMF}n was synthesized. It exhibits good selective adsorption for CO2; moreover, it shows high selectivity and sensitivity for NB and Cr2O72− ions.

Zn(ii) and Cd(ii) coordination polymers with a new angular bis-pyridyl-bis-amide: synthesis, structures and sensing properties

Zn(ii) and Cd(ii) coordination polymers that show a 2D double layer with the rare (4⁶·6⁴)-5 L4 topology and a 3D framework with a new (4·5·6)(4⁵·5⁵·6⁹·7·8) topology, respectively, show good selectivity toward the detection of Fe³⁺ ions.

Lanthanide-based bis-(3,5-dicarboxy-phenyl)terephthalamide metal–organic frameworks: slow relaxation of magnetization and detection of trace Fe2+ and Fe3+

{[Dy₂(BDPT)_1.5(DMF)₄]·H₂O}_n (1) and [Sm₂(BDPT)_1.5(DMF)₄]_n (2) were prepared with highly sensitive fluorescent detection of trace Fe²⁺ and Fe³⁺. 1 exhibits weak antiferromagnetic interactions with signature of SMM behavior.

Tandem-like vanadium cluster chains in a polyoxovanadate-based metal–organic framework for efficient catalytic oxidation of sulfides

The vanadium cluster chain in V-Ni-MOF can efficiently catalyze the oxidation of sulfides with hydrogen peroxide as the oxidant, achieving the complete conversion from sulfides to sulfones within 1 hour at 40 °C.

Two cluster-based metal–organic frameworks with selective detection of Hg2+ ion and magnetic properties

Two cluster-based metal–organic frameworks have been synthesized—one exhibits highly selective fluorescent detection of trace Hg2+ and the other shows antiferromagnetic interactions between Mn3+ ions.

Two new NiII and ZnII metal-organic frameworks of glutarate and 1,4-bis[(2-methyl-1H-imidazol-1-yl)methyl]benzene ligands: syntheses, structures and luminescence sensing properties

Two new metal-organic frameworks (MOFs), namely, three-dimensional poly[diaquabis{μ₂-1,4-bis[(2-methyl-1H-imidazol-1-yl)methyl]benzene}bis(μ₂-glutarato)dinickel(II)] monohydrate], {[Ni₂(C₅H₆O₄)₂(C₁₆H₁₈N₄)₂(H₂O)₂]·H₂O}_n or {[Ni₂(Glu)₂(1,4-mbix)₂(H₂O)₂]·H₂O}_n, (I), and two-dimensional poly[[{μ₂-1,4-bis[(2-methyl-1H-imidazol-1-yl)methyl]benzene}(μ₂-glutarato)zinc(II)] tetrahydrate], {[Zn(C₅H₆O₄)(C₁₆H₁₈N₄)]·4H₂O}_n or {[Zn(Glu)(1,4-mbix)]·4H₂O}_n (II), have been synthesized hydrothermally using glutarate (Glu^2-) mixed with 1,4-bis[(2-methyl-1H-imidazol-1-yl)methyl]benzene (1,4-mbix), and characterized by single-crystal X-ray diffraction, IR and UV-Vis spectroscopy, powder X-ray diffraction, and thermogravimetric and photoluminescence analyses. Ni^II MOF (I) shows a 4-connected 3D framework with point symbol 6⁶, but is not a typical dia network. Zn^II MOF (II) displays a two-dimensional 4⁴-sql network with one-dimensional water chains penetrating the grids along the c direction. The solid-state photoluminescence analysis of (II) was performed at room temperature and the MOF exhibits highly selective sensing toward Fe³⁺ and Cr₂O₇^2- ions in aqueous solution.

Novel alkaline earth metal–organic frameworks with thiophene groups for selective detection of Fe3+

This work demonstrates that the alkaline earth ion radii play an important role in coordination numbers and topologies for constructing MOFs, and these MOFs can be used as fast-response fluorescence sensors for the detection of Fe³⁺.

Two novel lead-based coordination polymers for luminescence sensing of anions, cations and small organic molecules

A novel lead-based compound is reported as a multi-responsive luminescent sensor for detecting anions, cations and small organic molecules, especially Cr₂O₇²⁻, CrO₄²⁻, Fe³⁺ and nitrobenzene.

Three new ZnII coordination polymers constructed from a semi-rigid tricarboxylic acid: structural changes caused by flexibility and luminescence sensing for hexavalent chromate anions

Coordination polymers (CPs) with specific structures and functional luminescence have been widely designed as sensors for detecting small molecules and ions. In this study, with or without the help of an N-donor auxiliary linker, three new Zn^II CPs, namely, three-dimensional (3D) poly[[pentaaquabis[μ₃-5-(4-carboxybenzyloxy)isophthalato]bis[μ₆-5-(4-carboxylatobenzyloxy)isophthalato]di-μ₃-hydroxido-hexazinc(II)] trihydrate], {[Zn₆(C₁₆H₁₀O₇)₂(C₁₆H₉O₇)₂(OH)₂(H₂O)₅]·3H₂O}_n or {[Zn₆(μ₃-HL)₂(μ₆-L)₂(μ₃-OH)₂(H₂O)₅]·3H₂O}_n, (I), one-dimensional (1D) catena-poly[[[aqua(1,10-phenanthroline)zinc(II)]-μ₂-5-(4-carboxybenzyloxy)isophthalato] dihydrate], {[Zn(C₁₆H₁₀O₇)(C₁₂H₈N₂)(H₂O)]·2H₂O}_n or {[Zn(μ₂-HL)(phen)(H₂O)]·2H₂O}_n (phen is 1,10-phenanthroline), (II), and 3D poly[diaquatetrakis(4,4'-bipyridine)bis[μ₆-5-(4-carboxylatobenzyloxy)isophthalato]di-μ₃-formato-di-μ₃-hydroxido-pentazinc(II)], [Zn₅(C₁₆H₉O₇)₂(HCOO)₂(OH)₂(C₁₀H₈N₂)₄(H₂O)₂]_n or [Zn₅(μ₄-L)₂(bpy)₄(μ₂-OH)₂(μ₃-HCOO)₂(H₂O)₂]_n (bpy is 4,4'-bipyridine), (III), have been constructed from the semi-rigid tricarboxylic acid 5-(4-carboxybenzyloxy)isophthalic acid (H₃L) under hydrothermal conditions. CP (I) exhibits a twofold interpenetrated 3D+3D→3D skeleton with a 3,5-conn topology constructed from triangular trinuclear [Zn₃(COO)₄(μ₃-OH)] clusters, in which the H₃L ligand adopts three different coordination modes. CP (II) exhibits a 1D infinite chain and stacking that gives a 3D structure mediated by hydrogen bonds and weak interactions. CP (III) is an interesting 3D 3,4,8-conn network including linear tetranuclear [Zn₄(μ₂-OH)₂(HCOO)₂(COO)₂] clusters with a new {4·6²}₂{4·6⁴·8}{4⁶·6¹⁹·8³} topological symbol. The influences of the flexible -CH₂-O- linker of the H₃L ligand and subtle environmental factors, such as solvent, pH value and auxiliary ligands, on the formation of the final structures are also discussed. The solid-state fluorescence spectra of CPs (I)-(III) were recorded at room temperature and all show better fluorescence performances than H₃L. In particular, (II) can act as a potential multifunctional fluorescent material for sensing hexavalent chromium ions in aqueous solution with high stability, selectivity and sensitivity. Under ultraviolet light of 365 nm from a UV lamp, a signal response of fluorescence from turning on to off can be observed with the naked eye. It was found that the detection for hexavalent chromium (i.e. Cr₂O₇^2-) by (II) has a high selectivity [K_SV = 1.61 × 10⁴ M^-1 and limit of detection (LOD) = 0.434 µM] in aqueous solution. Quenching mechanisms were also studied in detail.

Two exceptionally stable luminescent MOFs for the selective and sensitive detection of Fe3+ ions in aqueous solution

Two exceptionally stable MOFs were selected as highly efficient sensors for the rapid, sensitive and selective detection of Fe³⁺ in aqueous solution.

Structural diversity, magnetic property, or luminescence sensing of Co(ii) and Cd(ii) coordination polymers derived from designed 3,3′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoic acid

Three Co(ii)-CPs and two Cd(ii)-CPs were synthesized and the Cd(ii)-CPs can detect CrO₄²⁻ and Cr₂O₇²⁻ anions in aqueous solution.

Two mixed-ligand Cd(ii)–organic frameworks with unique topologies: selective luminescence sensing of TNP and Cu2+ ions with recyclable performances

Two luminescent Cd(ii)–organic frameworks exhibit unprecedented (4,4,5,5)-c and (4,4,4,6,7)-c topologies, and highly sensitive and selective sensing of 2,4,6-trinitrophenol and Cu²⁺.

Assembly of metal–organic frameworks based on 4-connected 3,3′,5,5′-azobenzenetetracarboxylic acid: structures, magnetic properties, and sensing of Fe3+ ions

Three complexes based on 3,3′,5,5′-azobenzenetetracarboxylic acid were synthesized, showing potential applications in magnetism and excellent sensing properties towards Fe³⁺.

Antibacterial and aqueous dual-responsive sensing activities of monomeric complexes with uncoordinated imidazole sites

The butterfly-shaped monomeric complex is stable and slight soluble in water, which shows antibacterial and aqueous dual-responsive sensing activities.

Exploring the syntheses, structures, topologies, luminescence sensing and magnetism of Zn(ii) and Mn(ii) coordination polymers based on a semirigid tricarboxylate ligand

Two Zn(ii)-CPs and two Mn(ii)-CPs were constructed from metal salts, H₃cpota and N-heterocyclic group ligands. Their structures, magnetic properties and luminescence sensing properties have been studied in detail.

A multifunctional and recyclable terbium(iii) coordination polymer: displaying highly selective and sensitive detection of Fe3+ and CrVI anions, and picric acid in aqueous media

A multifunctional Tb-CP (1) as a recyclable luminescent probe to detect Fe³⁺ and Cr^VI anions, and picric acid in aqueous media.