Metal-organic Gels Research Articles

Ultrafast Degradation and High Adsorption Capability of a Sulfur Mustard Simulant under Ambient Conditions Using Granular UiO-66-NH2 Metal-Organic Gels.

Zirconium-based metal-organic frameworks (Zr-MOFs) have been considered as prospective materials for the degradation of nerve chemical warfare agents (CWAs) but show poor catalytic performance toward blister agents. Moreover, the powder issues and the poor adsorption capability also remain as the major challenges for the application of Zr-MOFs in practical CWA detoxification. Herein, a series of defected granular UiO-66-NH2 metal-organic gels are synthesized via adjusting the amount of added concentrated hydrochloric acid for the decontamination of 2-chloroethyl ethyl sulfide (2-CEES), a sulfur mustard simulant. The half-life of 2-CEES decontaminated by defected granular UiO-66-NH2 metal-organic gels can be shortened to 7.6 min, which is the highest reported value for MOFs under ambient conditions. The mechanism of decontamination is that the amino group on the linkers in UiO-66-NH2 MOGs undergoes a substitution reaction with 2-CEES to yield 2-(2-(ethylthio)ethylamino)terephthalic acid, which is less toxic and fixed in the frameworks. The recycling test corroborates that the granular UiO-66-NH2 xerogels possess good stability and reusability. Static adsorption and desorption tests show that UiO-66-NH2 xerogels possess a high 2-CEES vapor adsorption capacity of 802 mg/g after exposure for 1 d and only 28 wt % desorption capacity after air exposure for 7 d. The dual function of ultrafast degradation and high adsorption capability provide a firm foundation for using UiO-66-NH2 xerogels as a future protection media.

Adsorption and reutilization of Pb(II) based on acid-resistant metal-organic gel

Because of the serious threat of Pb(II) to human health and environment, the adsorption and removal of Pb(II) have attracted great attention. Herein, a novel zirconium-based metal-organic gel (MOGs, HNU-G3) was synthesized with splendid acid-resistant property in the pH 1–7. The gel showed remarkable selectivity and excellent adsorption capacity (475.88 mg g−1) for Pb(II). Benefitting from the merit of acid-resistant property, the removal of Pb(II) from spent lead-acid battery electrolytes was tested, and it exhibits good removal effect in other interference ions. The adsorption mechanism can be attributed to the interaction from COOH/NH of gel to Pb(II). The adsorption results proved that the gel can be served as an efficient, low-cost and environmentally friendly material for Pb(II) adsorption. For the sustainable development purpose, the adsorbed Pb(II) can be used to synthesize CsPbBr3, which pave a sustainable way for the effective utilization of waste Pb(II).

Lanthanide metal doped organic gel as ratiometric fluorescence probe for selective monitoring of ciprofloxacin

In this experiment, a novel ratio fluorescent gel probe based on double rare earth metal doped ‘Terbium-Europium-metal organic gel’ Tb-Eu-MOG was designed and successfully achieved the analysis and monitoring of ciprofloxacin (CIP). The dual emission probe (Tb-Eu-MOG) sensing is based on adjusting the energy and electronic conversion between the boronic acid-based ligand and Tb3+, Eu3+ ions. The 3,5-dicarboxybenzeneboronic acid (DBA) organic ligand not only used as the “antenna” to magnify the luminescence of Tb3+ and Eu3+ but also given strong support for the construction of the metal organic gel three-dimensional system. Dual fluorescence emission from lanthanide elements were generated at 545 nm and 615 nm under the excitation of 295 nm, respectively. Based on the photo-induced charge transfer (PET) and fluorescence resonance energy transfer (FRET) between the electron-donating group and the electron-withdrawing functional group, it provided a good test environment for the specific and high-sensitivity detection of CIP. Attributable to the porous structure formed by the intersecting of metal organic gel fiber bundles, as well as mutual attraction between the boron atomic orbital and CIP, the novel polymer probe exhibited outstanding characteristics for analysis of CIP including, fluorescence stabilization, rapid response, high selectivity and sensitivity. The doping ratiometric fluorescence monitoring strategy provided an alternative sensing method for the rapid and sensitive analytical determination of ciprofloxacin in complex biological matrix, and the reasonable doping of MOG provided some enlightenment.

A visual peroxidase mimicking aptasensor based on Pt nanoparticles-loaded on iron metal organic gel for fumonisin B1 analysis in corn meal

A visual colorimetric aptasensor combining platinum nanoparticles (Pt NPs) loaded on Fe-based metal organic gel (Fe-MOG) as peroxidase mimics with magnetic separation technique was designed for the detection of fumonisin B1 (FB1). Interestingly, based on the inherent properties of Fe-MOG such as porous nanostructures, abundant Fe2+/Fe3+ active metal centers and synergetic effect between Pt NPs and Fe-MOG, Pt NPs/Fe-MOG composites can be employed as excellent peroxidase mimetic enzyme to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2. This process was accompanied by a color variation of the solution from colorless to blue. Kinetic analysis showed that the Pt NPs/Fe-MOG composites make an effective peroxidase mimic with low Michaelis constant (Km), high substrate binding affinity and rapid catalytic velocity (Vm). Furthermore, the Pt NPs/Fe-MOG based colorimetric aptasensor was used to detect FB1. The prepared Pt NPs/Fe-MOG achieved lower detection limit (2.7 pg/mL, 3σ/k) with a wide linear range of 0.01–2000.0 ng/mL. Finally, as a proof of concept of the rapidity and the simplicity of this colorimetric aptasensor, Pt NPs/Fe-MOG was used for the detection of FB1 in real corn samples.

Dual channel detecting of CO in a metal complex gel system: Phase transition and fluorescence enhancement

A C3 symmetric molecule BTBM bearing benzimidazole moiety was design and synthesized. BTBM could form supramolecular gel in glacial acetic acid and exhibit fluorescent emission. By complexing with Pd2+, metal organic gel could be obtained and the fluorescent intensity of the benzimidazole moiety was weaken. When the metal organic gel was placed in CO gas atmosphere, the metal organic gel was collapsed and the fluorescence recovered again. This work provide a dual channel method including the phase transition and fluorescent intensity change to detect CO gas by naked eyes.

Introducing Zirconium Organic Gels for Efficient Radioiodine Gas Removal.

Iodine radioisotope, as one of the most important fission products of uranium, may cause severe damage to human health when it is accidentally discharged into the environment. Hence, efficient removal of radioactive iodine is one of the most critical issues for both used nuclear fuel (UNF) reprocessing and environmental remediation. In this work, three metal-organic gels (MOGs) were introduced for iodine removal. The presented zirconium-based MOGs, namely, CWNU, CWNU-NH2, and CWNU-2NH2, were prepared via moderate solvothermal reactions. These MOGs all exhibit excellent chemical stability and reusability, marked iodine sorption capability, and favorable machinability, which can even rival commercial ones. The sorption capacities are determined to be 3.36, 4.10, and 4.20 g/g, respectively. The increased amount of amino group is considered to be responsible for the elevated iodine sorption capacity and kinetics, as confirmed by combined sorption studies and XPS analysis. The presented work sheds light on the utilization of MOGs for radioiodine capture.

An Iron(III)-Based Metal-Organic Gel-Catalyzed Dual Electrochemiluminescence System for Cytosensing and In Situ Evaluation of the VEGF165 Subtype.

The recent surge of interest in metal-organic gels (MOGs) has emerged for their soft porous structure, large surface area, and abundant active metal sites, making them a promising candidate for building catalyst matrices. In this work, facilely synthesized Fe(III)-organic gel was directly used as a robust electrode matrix. Detailed studies illustrated that their Fe(III) centers can speed up the electro-oxidation/reduction of the H2O2 coreactant to produce reactive oxygen species for enhancing a potential-resolved dual electrochemiluminescence (ECL) emission. Among them, the anodic signal of luminol varied with the cell concentration based on the impedance ECL mechanism, while the cathodic signal of CdS quantum dots traced the VEGF165 subtype at cell surface by specific aptamer recognition. Based on this, a ratiometric strategy was proposed for accurate cytosensing by eliminating environmental interference. Moreover, by cooperating these two signals, a novel strategy was developed for direct evaluation of the VEGF165 subtype, further realizing rapid drug screening and subtype assessment on different cell lines. This work not only opens up the promising application of MOGs as an effective catalyst matrix but also develops reliable cell assays and protein subtype identification for clinical diagnosis and research.

Innovative Microstructural Transformation upon CO2 Supercritical Conditions on Metal-Nucleobase Aerogel and Its Use as Effective Filler for HPLC Biomolecules Separation.

This work contributes to enlightening the opportunities of the anisotropic scheme of non-covalent interactions present in supramolecular materials. It provides a top-down approach based on their selective disruption that herein has been employed to process a conventional microcrystalline material to a nanofibrillar porous material. The developed bulk microcrystalline material contains uracil-1-propionic acid (UPrOH) nucleobase as a molecular recognition capable building block. Its crystal structure consists of discrete [Cu(UPrO)2 (4,4′-bipy)2 (H2 O)] (4,4′-bipy=4,4′-bipyridine) entities held together through a highly anisotropic scheme of non-covalent interactions in which strong hydrogen bonds involving coordinated water molecules provide 1D supramolecular chains interacting between them by weaker interactions. The sonication of this microcrystalline material and heating at 45 °C in acetic acid–methanol allows partial reversible solubilization/recrystallization processes that promote the cross-linking of particles into an interlocked platelet-like micro-particles metal–organic gel, but during CO2 supercritical drying, the microcrystalline particles undergo a complete morphological change towards highly anisotropic nanofibers. This unprecedented top-down microstructural conversion provides a nanofibrillar material bearing the same crystal structure but with a highly increased surface area. Its usefulness has been tested for HPLC separation purposes observing the expected nucleobase complementarity-based separation.

Hierarchical porous metal-organic gels and derived materials: from fundamentals to potential applications.

Metal-organic gels (MOGs) emerged as a novel class of functional soft materials in which the scaffolding framework is fabricated by metal-ligand coordination in combination with other supramolecular interactions (for example, hydrogen bonding or π-π stacking). Through the combination of organic and inorganic (metal/metal-oxo clusters) building blocks, significant steps forward have been made in the development of new electrochemical sensors, superhydrophobic materials and ion storage devices, among others. These leaps forward are to some extend induced by the intrinsic hierarchical microporous/mesoporous pore structure of these metal-organic materials. Within this review we give an overview of recent developments of this growing field. First, we shed light onto the parallels to the well-established field of conventional gels and outline similarities and differences. Afterwards, we classify different types of MOGs according to their architectural/structural nature: (1) pristine MOGs, (2) hybrid MOGs, (3) crosslinking-based MOGs and (4) MOG-derived materials. Furthermore, we look at the different properties of MOGs and the requirements for the preparation of spatially patterned macro-structured MOGs by emerging additive manufacturing technologies. Moreover, different potential fields of application for MOGs and MOG derived materials are critically evaluated and potential improvements and pitfalls in comparison to traditional gel-based materials are given. Finally, a comprehensive outlook into future directions for the development of MOGs is provided.

Metal-organic gel as a fluorescence sensing platform to trace copper(II).

Metal-organic gel (MOG), as a novel type of metallic organic hybrid material, exhibits diverse properties. However, its application in fluorescence detection for specific metal ions has rarely been exploited. In this work, we have designed and synthesized a MOG based on Al-carboxylate coordination assemblies (denoted as MOG-Al). The resultant MOG-Al shows good specific fluorescence signal response to trace Cu2+. Under optimal conditions, the fluorescence quenching degrees (F0 - F) of the MOG-Al have a linear correlation with Cu2+ concentration ranging from 0.05 to 100 μM, and the limit of detection (LOD) is 45.00 nM. The proposed sensing platform was also applied for the detection of Cu2+ in real samples. Satisfactory recoveries (92-116%) for Cu2+ in rice, soybean milk powder and pork liver were obtained. These results indicate that MOG-Al is a promising material for the specific and sensitive sensing of Cu2+.

Metal–organic gel coupled entropy-driven circuit for fluorescence detection of miR-155

We reported a novel strategy that combined a Cu-based metal–organic gel (Cu-MOG) with an entropy-driven circuit (EDC) to detect miR-155 as a proof-of-principle target.

Dye contaminated wastewater treatment through metal–organic framework (MOF) based materials

A complete discussion of MOFs and MOF composites such as MOF-based membranes, magnetic MOFs, and metal–organic gels (MOGs) used for dye removal along with their adsorption efficiency has been done.

A Nanostructured Cu(II) Coordination Polymer Based on Alanine as a Trifunctional Mimic Enzyme and Efficient Composite in the Detection of Sphingobacteria.

This research raises the potential use of coordination polymers as new useful materials in two essential research fields, allowing the obtaining of a new multiartificial enzyme with the capacity to inhibit the growth of bacteria resistance. The fine selection of the ligands allows the design of a new 2D coordination polymer (CP), with the formula [Cu2(IBA)2(OH2)4]n·6nH2O, by the combination of Cu (II) as the metal center with a pseudoamino acid (H2IBA = isophthaloyl bis β-alanine). Quantitative total X-ray fluorescence (TXRF) analyses show that the obtained CP can gradually release Cu (II) ions. Additionally, this CP can be nanoprocessed and transformed into a metal-organic gel (MOG) by using different Cu (II) salt concentrations and the application of ultrasounds. Considering its nanometric dimensions, the slow Cu (II) release and its simple processability, its performance as an artificial enzyme, and its antibacterial ability were explored. The results obtained show the first nanocoordination polymer acting as an artificial multienzyme (peroxidase, catalase, and superoxodismutase) exhibiting antibacterial activity in the presence of hydrogen peroxide, with selective behavior for three bacterium strains (S. spiritovirum, A. faecales, and B. cereus). Indeed, this CP shows a more robust inhibition capacity for Sphingobacterium. Going beyond that, as there are no comfortable and practically clinical tests capable of detecting the presence of Sphingobacteria, the compound can be easily embedded to form moldable gelatin that will facilitate the handling and low-cost commercial kits.

Luminescent porous metal–organic gels for efficient adsorption and sensitive detection of chlortetracycline hydrochloride assisted by smartphones and a test paper-based analytical device

Three porous and luminescent JLUE-MOGs are fabricated for the efficient removal of CTC, and on-site rapid and sensitive detection of CTC with the help of paper and a smartphone is realized.

Toxic metal–organic gels using a unique pyridine–pyrazole based ligand with Pb(ii), Cd(ii) and Hg(ii) salts: multi-stimuli responsiveness and toxic dye adsorption

The work presents herein the LMWG property of pyridine–pyrazole containing Schiff base ligand in presence of toxic heavy metals like Pb, Cd and Hg. These MOGs exhibited gel based remarkable toxic dye adsorption and multi-stimuli responsiveness.

In situ conversion of a MOG to a crystalline MOF: a case study on solvent-dependent gelation and crystallization.

Herein, we report in situ transformation of a metal-organic gel (MOG) to a crystalline metal-organic framework (MOF) and solvent-dependent gelation/crystallization via solvothermal reactions of a tetracarboxylic acid, namely 4,4'-dinitro-2,2',6,6'-tetracarboxybiphenyl, and ZnSO4. The results provide structural insights into MOGs at the molecular level and also help in the synthesis of crystalline MOFs that are otherwise difficult to obtain.

Magnetic Porphyrin-Based Metal Organic Gel for Rapid Rhb Removal and Enhanced Antibacterial Activity by Heterogeneous Photo-Fenton Reaction Under Visible Light

Magnetic Porphyrin-Based Metal Organic Gel for Rapid Rhb Removal and Enhanced Antibacterial Activity by Heterogeneous Photo-Fenton Reaction Under Visible Light

Novel self-supporting multilevel-3D porous NiO nanowires with metal-organic gel coating via “like dissolves like” to trigger high-performance binder-free lithium-ion batteries

In this work, we put forward a concept of novel self-supporting multilevel-3D porous NiO nanowires and successfully synthesize them to be used as binder-free electrode for lithium-ion batteries (LIBs). According to the “like dissolves like” rule, Zr-based metal-organic gel (Zr-MOG) with the same organic ligand of the precursor of NiO is in situ coated on the surface of novel multilevel-3D porous nanowires, which not only effectively stabilizes the multilevel-3D porous network structure, but also adheres the electrode material to the surface of the Cu foil effectively and prevents electrode pulverization or shedding due to its own viscosity without adding binder (PVDF) in the process of fabricating electrode. Contact angle analysis illustrates Zr-MOG possesses potential to provide cementation power. Through theoretical simulation, the binding energy of NiO@Zr-MOG is lower than NiO, demonstrating the superiority to occur the redox reaction. The novel self-supporting multilevel-3D porous NiO nanowires coated by Zr-MOG possess superior electrochemical performance of LIBs (the specific capacity reached 1816.3 mAh g −1 at the current density of 100 mA g −1 , remained at 1318.7 mAh g −1 after 150 cycles). This work will provide a new perspective for the fabrication of high-performance binder-free LIB electrodes. • Put forward the concept of novel multilevel-3D porous nanowires. • Binder-free lithium-ion battery anode by “like dissolves like” coating. • The superiority of NiO@Zr-MOG was demonstrated by theoretical simulation. • The fabrication method is applicable to other transition metal oxides.

In situ hydrothermal growth of metal-organic gels coating for efficient solid-phase microextraction of pesticide residues

In this study, a metal-organic gels (MOGs)-coated solid-phase microextraction (SPME) fiber was developed and coupled with gas chromatography-mass spectrometer (GC–MS) for highly sensitive detection of pesticide residues in fruit samples. The MOGs-coated fiber was prepared using a simple in situ hydrothermal growth method, and the influencing factors in preparation process were investigated in detail. The prepared fiber showed high extraction efficiency, and excellent acid and alkali resistance. Under the optimized conditions, the developed SPME-GC–MS method showed wide linearity in the range of 0.01–10.00 ng mL−1 for eleven pesticides. The limits of detection (LODs, S/N=3) and quantification (LOQs, S/N = 10) were in the range of 0.001–0.052 ng mL−1 and 0.005 -0.094 ng mL−1, respectively. The relative standard deviations (RSDs, n = 5) of single steel wire and steel wire to steel wire were all below 10.7%. The method was successfully applied to determine pesticide residues in fruit samples with satisfactory recovery of 79.3% -117.7% and RSDs varying from 2.9% to 9.6%. The MOGs-coated fiber stayed stable after 100 times extractions without significant changes in extraction capacity. The results indicated that the MOGs provided a promising coating for SPME of pesticide residues in complicated matrix.

A new type of porous Zn (II) metal-organic gel designed for effective adsorption to methyl orange dye

Metal-organic gels, which have attracted much attention and research due to their novel properties, were usually prepared with organic solution. In this paper, a new metal-organic gel was assembled by mixing proper amount of xanthine and zinc acetate in pure water with the assistance of triethylamine. The results of FTIR and XRD indicated that the hydrogel was self-assembled through coordination, hydrogen bond and π-π stacking. The hydrogel exhibited thixotropic property and good resistance to acid, alkali and heat. The xerogel obtained by freeze-drying had a porous structure with pore size ranging from several nanometers to several hundred nanometers as shown in the SEM images. The xerogel had the effectively adsorption properties for methyl orange in aqueous solution, and the adsorption efficiency is up to 80.63%. The model of adsorption kinetics and adsorptions isotherm show that the adsorption data were consistent with the Freundlich equation and the pseudo-second-order model, which mainly attribute to the chemisorption of methyl orange on multilayer heterogeneous surface of the xerogel. Prepared by a simple and mild method, the xerogel is a promising adsorbent for dye wastewater treatment.