Three coordination polymers based on 4,4'-bis(2-methylimidazol-1-yl)diphenyl ether: Synthesis, structure and selective fluorescent sensing properties

Three CPs [Zn2(PDA)2(BMIOPE)2·3H2O]n (1), [Co(Br-BDC)(BMIOPE)]n (2) and [Co(MIP)(BMIOPE)]n (3) were synthesized by solvothermal method based on dual-ligand strategy (H2PDA, Br-H2BDC, BMIOPE and H2MIP are 1,3-phenylenediacetic acid, 5-bromo-isophthalic acid, 4,4'-bis(2-methylimidazol-1-yl)diphenyl ether and 5-methylisophthalic acid, respectively). Complexes 1 and 3 exhibit twofold parallel interwoven sql nets. Complex 2 is 2D layer structure. The luminescence property investigations showed that complexes 1-3 could act as multi-responsive fluorescent sensors to detect UO22+, Cr2O72- and CrO42- and nitrofurantoin (NFT) through fluorescence turn-off process, presenting excellent sensitivity and selectivity. Finally, the possible fluorescent quenching mechanisms of complexes 1-3 toward the above pollutants are also further investigated by employing spectroscopic methods and quantum chemical calculations. The fluorescence lifetime measurements manifest the mechanism of fluorescence quenching is static quenching process.

Eu3+ Complex-Based Superhydrophobic Fluorescence Sensor for Cr(VI) Detection in Water

Cr(VI) compounds are bioaccumulative and highly toxic pollutants, and there is a need for simple and fast detection methods to monitor their trace levels. In this work, we developed a Eu3+ complex-based fluorescence sensor to easily detect Cr(VI) in water droplets. Our sensor consists of a nanofibrous membrane electrospun with a blend of polyvinylidene fluoride (PVDF), silica particles, and Eu3+ complex. Upon modifying the membrane surface with fluoroalkyl chemistry, the sensor displayed superhydrophobicity. When a water droplet with Cr(VI) was placed on such a superhydrophobic fluorescence sensor, the overlapping absorption of Cr(VI) and Eu3+ complex facilitated the inner filter effect, allowing the selective detection of Cr(VI) down to 0.44 µM (i.e., 45.76 µg L-1). We proposed and designed of new inexpensive and fast sensor for the detection of Cr(VI).

Surface modification of quartz sand: A review of its progress and its effect on heavy metal adsorption

Quartz sand (SiO₂) is a prevalent filtration medium, boasting wide accessibility, superior stability, and cost-effectiveness. However, its utility is often curtailed by its sleek surface, limited active sites, and swift saturation of adsorption sites. This review outlines the prevalent strategies and agents for quartz sand surface modification and provides a comprehensive analysis of the various modification reagents and their operative mechanisms. It delves into the mechanism and utility of surface-modified quartz sand for adsorbing heavy metal ions (HMIs). It is found that the reported modifiers usually form connections with the surface of quartz sand through electrostatic forces, van der Waals forces, pore filling, chemical bonding, and/or molecular entanglement. The literature suggests that these modifications effectively address issues inherent to natural quartz sand, such as its low superficial coarseness, rapid adsorption site saturation, and limited adsorption capacity. Regrettably, comprehensive investigations into the particle size, regenerative capabilities, and application costs of surface-modified quartz sand and the critical factors for its wider adoption are lacking in most reports. The adsorption mechanisms indicate that surface-modified quartz sand primarily removes HMIs from aqueous solutions through surface complexation, ion exchange, and electrostatic and gravitational forces. However, these findings were derived under controlled laboratory conditions, and practical applications for treating real wastewater necessitate overcoming further laboratory-scale obstacles. Finally, this review outlines the limitations of partially surface modified quartz sand and suggests potential venues for future developments, providing a valuable reference for the advancement of cost-effective, HMI-absorbing, surface-modified quartz sand filter media.

A Ni(II) Coordination Polymer as a Multifunctional Luminescent Sensor for Detection of UO22+, Cr2O72-, CrO42- and Nitrofurantoin

A new Ni coordination polymer [Ni(MIP)(BMIOPE)]_n (1) was constructed (BMIOPE = 4,4'-bis(2-methylimidazol-1-yl)diphenyl ether, and H₂MIP = 5-methylisophthalic acid), possessing two-dimensional (2D) twofold parallel interwoven net structure with a 4⁴∙6² point symbol. Complex 1 has been successfully obtained based on mixed-ligand strategy. The fluorescence titration experiments revealed that complex 1 could act as multifunctional luminescent sensor to simultaneously detect UO₂²⁺, Cr₂O₇^2- and CrO₄^2-, and NFT (nitrofurantoin). The limit of detection (LOD) values for complex 1 are 2.86 × 10^-5, 4.09 × 10^-5, 3.79 × 10^-5 and 9.32 × 10^-5 M for UO₂²⁺, Cr₂O₇^2-, CrO₄^2- and NFT. The K_sv values are 6.18 × 10³, 1.44 × 10⁴, 1.27 × 10⁴ and 1.51 × 10⁴ M^-1 for NFT, CrO₄^2-, Cr₂O₇^2- and UO₂²⁺. Finally, the mechanism of its luminescence sensing is studied in detail. These results manifest that complex 1 is a multifunctional sensor for sensitive fluorescent UO₂²⁺, Cr₂O₇^2-, CrO₄^2- and NFT detection.

Preparation of Highly Stable DUT-52 Materials and Adsorption of Dichromate Ions in Aqueous Solution

Highly stable DUT-52 materials were synthesized by the hydrothermal method and well-characterized by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). In order to systematically study the adsorption of dichromate ions in aqueous solution by the DUT-52 materials, a single factor experiment, kinetic experiment, thermodynamic experiment, competition ion experiment, and material regeneration experiment were designed. Based on the H-bond interaction between the dichromate ions and the H atoms of a NDC^2- ligand, the DUT-52 materials showed a maximum removal rate of 96.4% and a maximum adsorption capacity of 120.68 mg·g^-1 with excellent selective adsorption and material regeneration. In addition, the process of adsorption of dichromate ions by the DUT-52 materials is in accordance with the pseudo second-order kinetics and Langmuir models, and the adsorption mechanism and the important role of the H-bond interaction were reasonably explained using the XPS pattern and theoretical calculation. Accordingly, DUT-52 can be regarded as a multifunctional material for efficiently removing dichromate ions from the wastewater.

Deep-Red Luminescent Cuprous-Lead Bromide as a Dual-Responsive Sensor for Fe3+ and Cr2O72

Both optically active 1-tetrazole-4-imidazole-benzene (TIB) with bifunctional azole groups and heterometals were utilized to build a new type of one-dimensional (1-D) hybrid cuprous-lead bromide [PbCu₂Br₄(TIB)₂]_n (1), which exhibits infrequent deep-red luminescent emission at 704 nm with a large Stokes shift of 321 nm. Owing to the existence of rare free Lewis basic imidazole groups, 1 can be used as the sole dual-responsive luminescent sensor for the efficient and selective detection of Fe³⁺ and Cr₂O₇^2- in an aqueous solution.

Zero area thermal expansion of honeycomb layers via double distortion relaxation in (PPh4)[Cu2(CN)3]

The zero area TE of cyanide-bridged honeycomb layers occurs by complementary structural changes in the cation and anion counterparts.

Syntheses, structures, and luminescence properties of five new coordination polymers based on 3-carboxy-1-(3′-carboxybenzyl)-2-oxidopyridinium and neutral ligands

Five CPs have been synthesized by a new semi-rigid dicarboxyl ligand and neutral ligands under hydrothermal conditions, and their luminescent sensing experiments for different small molecules/ions were studied in detail.

Tunable hybrid perovskites with Narrow bandgap and Multistage phase transition properties: 2,2-difluoroethylamine·Antimony Hexabromide

Zero-dimensional perovskites have received extensive attention in recent years due to their unique structures, such as large exciton binding energy, strong quantum confinement effect, and good stability. Precisely construct target...

Two chemically robust Cd(II)-frameworks for efficient sensing of levofloxacin, benzaldehyde, and Fe3+ ions

Two luminescent Cd(II)-organic frameworks [Cd₂(L1)(tdc)₂(H₂O)]_n (1) and [Cd(L2)_0.5(tdc)]_n (2) (L1 = 1,5-bis(1-(pyridine-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)pentane, L2 = 1,6-bis(1-(pyridine-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)hexane, and H₂tdc = 2,5-thiophenedicarboxylic acid) were hydrothermally synthesized and characterized. 1 displays a rare binodal (3,4)-connected 2D cem-d network, while 2 exhibits a 3D mog (moganite) framework. The two MOFs are highly thermally durable and water-stable in a wide pH range from 3 to 12. Interestingly, 1 and 2 represent the first reported examples of multi-responsive probes based on MOFs for selectively detecting levofloxacin, benzaldehyde, and Fe³⁺ ions with reusability. The luminescence sensing mechanisms of the two CPs were explored in detail.

The Structure and Property of Two Different Metal-Organic Frameworks Based on N/O-Donor Mixed Ligands

Two different metal-organic frameworks (MOFs) [Cd2(AZN)(HAZN)(btc)(Hbtc)·4H2O]·2H2O (1), and [Zn3(AZN)2(btc)2·4H2O] (2) were synthesized by the reactions of different metal salts with mixed ligands of 1-(4-(1H-imidazol-5-yl)phenyl)-1H-1,2,4-triazole (AZN) and trimesic acid (H3btc). The different metal centers in the reaction condition have important impact on the resulting structures of MOFs 1 and 2. Compound 1 is a one-dimensional (1D) chain structure, while 2 features a three-dimensional (3D) framework with 3-fold interpenetration topology of Point (Schläfli) symbol of (6·82)4(62·82·102). Furthermore, the luminescent properties have been studied for MOFs 1 and 2.

A luminescent cationic MOF for bimodal recognition of chromium and arsenic based oxo-anions in water

Water pollution from heavy metals and their toxic oxo-anionic derivatives such as CrO42-, Cr2O72-, HAsO42-, and HAsO32- has become one of the most critical environmental issues. To address this, herein, we report a new hydrolytically stable luminescent Zn(ii) based cationic metal organic framework (MOF), iMOF-4C, which further successfully exhibited a rare dual "turn off/on" fluorescence response toward Cr(vi), As(v) and As(iii) based oxo-anions respectively in water medium. In addition, iMOF-4C was found to maintain its superior selectivity in the presence of other concurrent anions (e.g. SO42-, Cl-, Br-, ClO4-, NO3-, SCN- and CO32-). More importantly, iMOF-4C exhibited an excellent selective and sensitive luminescence "turn-off" response towards CrO42- and Cr2O72- anions in water medium with the quenching constant (Ksv) values as high as 1.31 × 105 M-1 (CrO42-) and 4.85 × 105 M-1 (Cr2O72-), which are found to be the highest among the values reported in the regime of MOFs. Interestingly, iMOF-4C showed fluorescence "turn-on" response toward HAsO42- and HAsO32- with an enhancement coefficient (Kec) of 1.98 × 104 M-1 and 3.56 × 103 M-1 respectively. The high sensitivity and low detection limits make iMOF-4C more feasible for real-time sensing of such toxic oxo-anions in an aqueous medium. Furthermore, the probable sensing mechanism has been investigated by DFT calculation studies and discussed in detail.

Visible-light excitable Eu3+-induced hyaluronic acid-chitosan aggregates with heterocyclic ligands for sensitive and fast recognition of hazardous ions

Water-soluble luminescent lanthanide complexes that can be excited with visible light could enable rapid detection of toxic anions and cations in biological systems. Eu³⁺-induced hyaluronic acid-chitosan aggregates (EIHCA) can improve the stability, biocompatibility, efficiency, and light absorption of luminescent Eu³⁺ complexes. Visible-range excitation may avoid phototoxicity associated with overexposure to UV light in biological and ecological applications. In this work, we synthesized and characterized series of EIHCA complexes having three N-donor heterocyclic ligands: 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (Dphen), 2,2': 6',2″-terpyridine (Tpy) and 1,10-phenanthroline monohydrate (Phen). These complexes possessed bright red fluorescence with a visible range excitation maximum. The photophysical properties of one formulation (we denote as EDL6) include fast quenching response (20 s) of the fluorescence, multi-selectivity, low limit of detection, and high quenching (K_sv) values, enabling selective, rapid and sensitive recognition of Cr₂O₇^2- and Fe³⁺ in aqueous solution. Furthermore, EDL6 exhibits cytocompatibility with mammalian cells that make these complexes promising biocompatible candidate as a safe replacement of organic fluorophores for fluorescence sensing applications. Thus, these new EIHCA complexes were successfully employed for the selective detection of hazardous materials in biological and aqueous environment samples.

Two porous Ni-MOFs based on 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine showing solvent determined structures and distinctive sorption properties toward CO2 and alkanes

By regulating the solvent used for synthesis, two porous Ni-MOFs, namely {[Ni3(BTC)2(TPT)2/3(H2O)4.08(MeOH)0.92]·2DMF·0.5H2O·0.5MeOH}n (1) and {[Ni3(BTC)2(TPT)2(H2O)6]·6DMF}n (2) (H3BTC = 1,3,5-benzenetricarboxylic acid, TPT = 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine, DMF = N,N-dimethylformamide, and MeOH = methanol) were obtained. Compound 1 reveals a rigid 3D framework, while compound 2 shows a flexible 3-fold interpenetrated framework. Compound 1 exhibits a selective adsorption of CO2 due to the sieving effect of the rigid framework containing two types of cages with small apertures. Noteworthily, the flexible compound 2 displays an obviously guest-induced structural transformation. The desolvated compound 2 reveals a much higher capacity toward CO2 and n-C4H10 than those of N2 CH4, C2H6 and C3H8.

Colorimetric detection of chromium (VI) ion using poly(N-phenylglycine) nanoparticles acting as a peroxidase mimetic catalyst

This paper reports on enzyme-like catalytic properties of polyethylene glycol-functionalized poly(N-phenylglycine) (PNPG-PEG) nanoparticles, which have not been explored to date. The developed nanoparticles have the ability to display great inherent peroxidase-like activity at very low concentrations, and are able to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) substrate in presence of hydrogen peroxide (H₂O₂). The oxidized product of TMB has a deep blue color with a maximum absorbance at ~655 nm. The PNPG-PEG nanoparticles exhibit K_m values of 0.2828 for TMB and 0.0799 for H₂O₂, indicating that TMB oxidation takes place at lower concentration of H₂O₂ in comparison to other nanozymes. Based on the known mechanism of H₂O₂ oxidation by hexavalent chromium [Cr(VI)] ions to generate hydroxyl radicals (^•OH), these nanoparticles were successfully applied for the colorimetric sensing of Cr(VI) ions. The sensor achieved good performance for Cr(VI) sensing with detection limits of 0.012 μM (0.01-0.1 μM linear range) and 0.52 μM (0.05-12.5 μM linear range). The detection scheme was highly selective, and successfully applied for the detection of Cr(VI) in real water samples.

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.

Syntheses of a series of lanthanide metal–organic frameworks for efficient UV-light-driven dye degradation: experiment and simulation

Three Ln-MOFs show unique 3,8-connected 3D networks and have been used as photocatalysts for the degradation of organic dye methyl violet under UV light.

A pillar-layered binuclear 3D cobalt(ii) coordination polymer as an electrocatalyst for overall water splitting and as a chemosensor for Cr(vi) anion detection

A 3D pillar-layered cobalt(ii) CP with a 3D (4,6)-connected {44·610·8}{44·62} fsc net was designed and it showed great potential as an electrocatalyst in the overall water splitting and as a chemosensor for Cr(vi) anion detection.

Luminescence sensing and photocatalytic activities of four Zn(ii)/Co(ii) coordination polymers based on a pyridinephenyl bifunctional ligand

Four Zn(ii)/Co(ii) CPs act as bifunctional materials in the detection of Fe(iii) cation, Cr(vi) anion, and nitrofuran antibiotics and removal of methylene blue in aqueous media.

Application of Various Metal-Organic Frameworks (MOFs) as Catalysts for Air and Water Pollution Environmental Remediation

The use of metal-organic frameworks (MOFs) to solve problems, like environmental pollution, disease, and toxicity, has received more attention and led to the rapid development of nanotechnology. In this review, we discuss the basis of the metal-organic framework as well as its application by suggesting an alternative of the present problem as catalysts. In the case of filtration, we have developed a method for preparing the membrane by electrospinning while using an eco-friendly polymer. The MOFs were usable in the environmental part of catalytic activity and may provide a great material as a catalyst to other areas in the near future.

Five water-stable luminescent CdII-based metal–organic frameworks as sensors for highly sensitive and selective detection of acetylacetone, Fe3+ and Cr2O72− ions

Five Cd^II-based MOFs with different topologies were prepared, in which 2 and 3 are rare examples which display excellent sensitivity, selectivity, recyclability and structural stability for detection of acac/Fe³⁺ and acac/Cr₂O₇²⁻, respectively.

Selective fluorescence sensing properties of a novel two-fold interpenetrating coordination polymer

One novel 3D interpenetrated Zn(ii) CP acts as multi-functional chemosensors in detection of acetone, Fe³⁺, Cu²⁺, Cr₂O₇²⁻, CrO₄²⁻ and nitrofurantoin (NFT).

Three water-stable luminescent two-dimensional CdII-based coordination polymers as sensors for highly sensitive and selective detection of Cr2O72− and CrO42− anions

Three 2D Cd^II-CPs with different topologies were prepared, in which 1 and 3 are rare examples which display excellent sensitivity, selectivity, recyclability and structural stabilities for the detection of Cr₂O₇²⁻/CrO₄²⁻.

Functional group induced structural diversities and photocatalytic, magnetic and luminescence sensing properties of four cobalt(ii) coordination polymers based on 1,3,5-tris(2-methylimidazol-1-yl)benzene

Based on the designed tripodal linker timb, four cobalt(ii) coordination polymers, {[Co₄(timb)₂(Br–IPA)₄]·5H₂O}_n (1), {[Co(timb)_0.5(NH₂–IPA)]·4H₂O}_n (2), {[Co₅(timb)₄(OH–IPA)₄]·2NO₃·2DMA·2H₂O}_n (3), and {[Co₃(timb)₂(SO₃–IPA)₂(H₂O)₂]·8H₂O}_n (4), have been obtained.