A Water-Stable Luminescent ZnII Metal-Organic Framework as Chemosensor for High-Efficiency Detection of CrVI -Anions (Cr2 O72- and CrO42- ) in Aqueous Solution

A Cd-MOF as a fluorescent probe for highly selective, sensitive and stable detection of antibiotics in water

Recently, the pollution and damage caused by antibiotics in water have aroused serious concerns. In this situation, it is extremely important to develop a highly effective approach to detect antibiotics in water. In this contribution, we built a Cd-MOF material with stable fluorescence properties, using bbi = 1,4-bis(2-methyl-imidazol-1-yl)butane and H2L = 1,2-phenylenediacetic acid as organic ligands and Cd(NO3)2·4H2O as the metal node. The highly selective response of this MOF probe to ceftriaxone sodium (an antibiotic) can reach up to the ppb level in water, along with a fast response time, acid and alkali resistance, and anti-interference ability.

Series of Cadmium(II) Coordination Polymers Based on a Versatile Multi-N-Donor Tecton or Mixed Carboxylate Ligands: Synthesis, Structure, and Selectively Sensing Property

Five Cd(II) metal-organic frameworks (MOFs), [Cd(HL)₂] (1), [Cd(HL)₂(H₂O)₂] (2), [Cd₃(HL)₂(obda)₂] (3), [Cd₂(HL)₂(ohmbda)(DMA)(H₂O)] (4), and [Cd₂(HL)(btc)(H₂O)₂]·3H₂O (5), were prepared by reactions of Cd(NO₃)₂·4H₂O with 1-(1H-imidazol-4-yl)-4-(4H-tetrazol-5-yl)benzene (H₂L) or mixed carboxylate ancillary ligands of 1,2-benzenedicarboxylic acid (H₂obda), 5-hydroxy-1,3-benzenedicarboxylic acid (H₂ohmbda), and 1,3,5-benzenetricarboxylic acid (H₃btc), respectively. Their structures have been characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy (IR), thermogravimetric analysis, and powder X-ray diffraction. Compounds 1 and 2 are supramolecular isomeric frameworks without consideration of the solvent molecules. Complex 1 exhibits a binodal (3, 5)-connected two-dimensional (2D) layer structure with the point (Schläfli) symbol of (5²·6)(5⁵·6⁴·7), while complex 2 shows a 2D + 2D → 3D (three-dimensional) framework. Complex 3 is a (3, 5, 6)-connected tetranodal 3D net with the point (Schläfli) symbol of (4·8²)₂(4⁵·6·8⁴)₂(4⁵·6⁵)₂(4⁸·6⁶·8). Compound 4 is a (3, 3, 8)-connected trinodal 3D net with the point (Schläfli) symbol based on a binuclear [Cd₂N₂O] subunit, while 5 is a 2-nodal (3, 4)-connected 2D V₂O₅-type network based on [Cd₂N₂(COO)₂] SBU. The studies of molecular sensing properties show that the luminescent MOFs can be employed as fluorescent sensors for the detection of Fe³⁺ and nitro compounds. Compound 1 and 3 exhibit quenching responses for Fe³⁺ in dimethylformamide solution with detection limits of 2.3 × 10^-6 and 8.6 × 10^-7 M, respectively. Meanwhile, compound 5 can sense 4-nitrophenol with a detection limit as low as 5.75 × 10^-7 M.

Effect of charge transfer and structural rigidity on divergent luminescence response of a metal organic framework towards different metal ions: luminescence lifetime decay experiments and DFT calculations

We have thoroughly studied the luminescence behaviour of a cadmium based MOF, [Cd(C12N2H8)(C7N1O4H3)] {C12N2H8 = 1,10-phenanthroline, C7N1O4H3 = 2,5-pyridine dicarboxylate}, 1. Both steady-state and time-resolved luminescence spectroscopic experiments were performed to understand the dissimilar responses of compound 1 towards different metal ions in aqueous medium. Upon excitation at 280 nm, compound 1 showed a luminescence spectrum centered at 365 nm, which exhibited a three-fold turn-on in the presence of a trace amount of Zn2+ in aqueous solution, whereas in the presence of Co2+, Hg2+, Ni2+, Fe2+ and Cu2+ the luminescence of compound 1 got largely quenched. Compound 1 did not show any response in the presence of other common metal ions such as K+, Mg2+, Na+, Mn2+, and Cr3+. By analysing all the experimental results, we successfully explained the versatile luminescence behaviour of compound 1. The turn-on of luminescence in the presence of Zn2+ ions was due to coordination bond formation and enhancement of the rigidity of compound 1 which resulted in the reduction of non-radiative decay processes to a large extent. The quenching of luminescence in the presence of transition metal ions was found to be static in nature, and was due to the possibility of ligand to metal charge transfer using the vacant d-orbital of the metal ions. In the case of Hg2+ which is a closed cell heavy metal ion, the quenching of luminescence was also static in nature and was due to a two-way charge transfer mechanism. We have also performed density functional theory calculations and obtained supportive results for the proposed mechanisms of luminescence turn-on and quenching. Moreover, compound 1 could be established as a selective and efficient sensor of Zn2+ in aqueous solution even in the presence of Cd2+ and other metal ions.

Metal-Assembled, Resorcin[4]arene-Based Molecular Trimer for Efficient Removal of Toxic Dichromate Pollutants and Knoevenagel Condensation Reaction

Self-assembly of resorcin[4]arene-based coordination cages involving more than two resorcin[4]arenes poses significant challenges for the requirements of suitable functionalized resorcin[4]arene ligands and metals. Here, we report an unusual example of a metal-coordinated, resorcin[4]arene-based molecular trimer (1-NO₃), composed of three resorcin[4]arenes and three Cd(II) cations. In particular, 1-NO₃ features efficient and selective removal of environmentally toxic dichromate (Cr₂O₇^2-) anions. Moreover, the Knoevenagel condensation reaction was also explored by using 1-NO₃ as an efficient heterogeneous catalyst.

Two luminescent coordination polymers as highly selective and sensitive chemosensors for CrVI-anions in aqueous medium

Two luminescent coordination polymers with considerable stability in aqueous media were synthesized. Sensing experiments indicate that they can serve as highly selective and sensitive fluorescent probes toward Cr^VI-anions.

An excellently stable TbIII–organic framework with outstanding stability as a rapid, reversible, and multi-responsive luminescent sensor in water

A multi-response Tb-based metal–organic framework with excellent stability is used as a rapid and reversible luminescent sensor for Fe³⁺, Cr₂O₇²⁻, and nitrofurantoin in water.

Two CuxIy-based copper–organic frameworks with multiple secondary building units (SBUs): structure, gas adsorption and impressive ability of I2 sorption and release

Two Cu_xI_y-based copper–organic frameworks with multiple SBUs have been successfully synthesized. Both the compounds exhibit high performance for I₂ sorption and release.

A pyrazine core-based luminescent Zr(iv) organic framework for specific sensing of Fe3+, picric acid and Cr2O72−

A new Zr-MOF incorporating a pyrazine core-based tetracarboxylate was used for selective fluorometric sensing of Fe³⁺, picric acid and Cr₂O₇²⁻ with outstanding sensitivity.

Selective recognition of Fe3+ and CrO42− ions using a Zn(ii) metallacycle and a Cd(ii) coordination polymer and their heterogeneous catalytic application

A Zn(ii) metallacycle [Zn₂{(L)₂(DMF)₂(NO₃)₂}]·(NO₃)₂ (1) along with a Cd(ii) coordination polymer [{Cd(L)₂(DMF)₂}·(NO₃)₂]_n (2) have been synthesized, structurally characterized and exploited as a multifunctional material.

Two 2D multiresponsive luminescence coordination polymers for selective sensing of Fe3+, CrVI anions and TNP in aqueous medium

Zn(ii)/Cd(ii)-based 2D coordination polymers have been synthesized as luminescence sensors for the selective and reversible sensing of Fe³⁺, CrO₄²⁻, Cr₂O₇²⁻ and TNP in water.

Metal Organic Frameworks Based Materials for Heterogeneous Photocatalysis

The increase in environmental pollution due to the excessive use of fossil fuels has prompted the development of alternative and sustainable energy sources. As an abundant and sustainable energy, solar energy represents the most attractive and promising clean energy source for replacing fossil fuels. Metal organic frameworks (MOFs) are easily constructed and can be tailored towards favorable photocatalytic properties in pollution degradation, organic transformations, CO₂ reduction and water splitting. In this review, we first summarize the different roles of MOF materials in the photoredox chemical systems. Then, the typical applications of MOF materials in heterogeneous photocatalysis are discussed in detail. Finally, the challenges and opportunities in this promising field are evaluated.

Dual-Emission SG7@MOF Sensor via SC-SC Transformation: Enhancing the Formation of Excimer Emission and the Range and Sensitivity of Detection

In this study, a water stable metal-organic framework FIR-53 is applied as a single-crystal container for anion exchange. The exceptional chemical stability and low crystallographic symmetry of FIR-53 makes it possible to determine anionic guests. Through ion exchange and single-crystal to single-crystal (SC-SC) transformation, 8-hydroxypyrene-1,3,6-trisulfonate (SG7, solvent green 7, ion form as SG7^3-) is introduced into the pores of FIR-53 to obtain SG7@FIR-53. Because of the spatial confinement and partition effect, SG7@FIR-53 shows the bright exciter emission of SG7 ions. Interestingly, the composite SG7@FIR-53 exhibits a sensitive fluorescence quenching response against Cr₂O₇^2- and MnO₄^- in aqueous solution. Especially, the detection limit toward MnO₄^- is as low as 0.12 ppb, which is the smallest value to date. Moreover, the prepared SG7@FIR-53 film also displays a broad response to nitro explosives in vapor/aqueous phase. Compared with the results of FIR-53, the range and sensitivity were greatly improved.

Nanoscale zeolitic imidazole framework-90: selective, sensitive and dual-excitation ratiometric fluorescent detection of hazardous Cr(vi) anions in aqueous media

Toxic Cr(vi) anions sensing in aqueous solution has been achieved by virtue of fluorescent nanoscale ZIF-90 and RhB@ZIF-90.

A ZnII-MOF Assembled by Triazine-Based Polycarboxylate and 4,4′-Bipy: Structure, Fluorescent Properties, and Water Vapour Adsorption

A new flexible triazine-based polycarboxylate metal–organic framework, {[Zn4(TTHA)(4, 4′-bipy)2(OH)2(H2O)]·H2O}n (1), H6TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid, has been synthesised under hydrothermal conditions and structurally characterised by X-ray diffraction, infrared spectroscopy, elemental analysis, and X-ray single-crystal diffraction. Structural studies indicate that 1 exhibits a 3D network with a 4,6-connected topology, formed by the interconnection of tetranuclear units and the ligands. The fluorescence emission properties of 1 and the free ligands were investigated in the solid state at room temperature. Moreover, the fluorescence lifetime (τ) and quantum yield (Φf) were obtained to further characterise the fluorescence properties. In addition, the water vapour adsorption of 1 was first studied for H6TTHA based complexes, which shows a general water adsorption capacity.

From 2D → 3D interpenetration to packing: N coligand-driven structural assembly and tuning of luminescent sensing activities towards Fe3+ and Cr2O72− ions

Three complexes were hydrothermally synthesized and exhibited excellent selectivity towards Fe³⁺ and Cr₂O₇²⁻.

Two MOFs as dual-responsive photoluminescence sensors for metal and inorganic ion detection

Two MOFs were synthesized and explored as dual-responsive photoluminescent sensors: 1 for Fe³⁺ and Cr₂O₇²⁻ ions, and 2 for Hg²⁺ and Cr₂O₇²⁻ ions.

A new stable luminescent Cd(ii) metal–organic framework with fluorescent sensing and selective dye adsorption properties

A stable Cd-MOF with free carboxyl groups in the channels has been synthesized, showing luminescent sensitivity for Fe³⁺, CrO₄²⁻ and Cr₂O₇²⁻ ions in aqueous solution, and selective adsorption of Congo red dye.

Fabrication of amine and imine-functionalized isoreticular pillared-layer metal–organic frameworks for the highly selective detection of nitro-aromatics

Chemical sensors for the rapid and selective detection of explosives such as 2,4,6-trinitrotoluene (TNT) are very important.