Metal-organic Gels Research Articles

Metal-Organic Gels of Catechol-Based Ligands with Ni(II) Acetate for Dye Adsorption.

Metal organic gels (MOGs) are a class of supramolecular complexes, which have attracted widespread interest because of the coupled advantages of inorganic and organic building blocks. A new compound terminated with catechol was synthesized. This new compound can be used to coordinate with Ni2+ to form MOGs. These MOGs show favorable viscoelasticity and wormhole-shaped porous structures, which were confirmed by transmission electron microscope and scanning electronic microscope images. Taking the benefits of porosity into account, the xerogel could serve as an adsorbent to adsorb dye molecules from the aqueous media. The experimental results indicate that xerogels possess good adsorption effect both on anionic and cationic dyes. Exhaustive research has been performed on the adsorption kinetics and isotherms, revealing that the adsorption process accords with the pseudo-second-order model and the Langmuir model.

Metal‐organic gels of simple chemicals and their high efficacy in removing arsenic(V) in water

Metal‐organic gels (MOGs) have emerged as a class of functional materials that show great potential applications in the field of catalysis, energy storage, template synthesis, and environmental technology. The construction of functional MOGs and the control of functionality are still challenging due to complicated chemicals or routes involved in previous works. Here we report a series of tunable multifunctional MOGs by directly gelating between Fe3+ and simple chemicals, propanedioic acid (H2PA), succinic acid (H2SA), glutaric acid (H2GA), and fumaric acid (H2FA) in ethanol. The obtained MOGs exhibit self‐healing property and good conductivity, and were used for high efficacy removal of arsenic (As) in water. The ease, low cost, and scalability of the assembly process combined with multifunctionality make these MOGs be potentially applied in the fields of energy storage and sewage disposal. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3719–3727, 2018

MIL-100(Al) Gels as an Excellent Platform Loaded with Doxorubicin Hydrochloride for pH-Triggered Drug Release and Anticancer Effect.

Slow and controlled release systems for drugs have attracted increasing interest recently. A highly efficient metal-organic gel (MOGs) drug delivery carrier, i.e., MIL-100(Al) gel, has been fabricated by a facile, low cost, and environmentally friendly one-pot process. The unique structure of MIL-100(Al) gels has led to a high loading efficiency (620 mg/g) towards doxorubicin hydrochloride (DOX) as a kind of anticancer drug. DOX-loaded MOGs exhibited high stability under physiological conditions and sustained release capacity of DOX for up to three days (under acidic environments). They further showed sustained drug release behavior and excellent antitumor effects in in vitro experiments on HeLa cells, in contrast with the extremely low biotoxicity of MOGs. Our work provides a promising way for anticancer therapy by utilizing this MOGs-based drug delivery system as an efficient and safe vehicle.

Fe(III) and Cu(I) based metal organic gels for in situ drug loading and drug delivery of 5-fluorouracil

We report anticancer drug, 5-fluorouracil (5FU) loaded Iron(III)-fumaric acid (IN·FA@5FU) and Copper(I)-thiourea (CuTu@5FU) metal organic gels (MOGs). These 5FU loaded MOGs are synthesized by in-situ process at ambient conditions. The cumulative release of the loaded anticancer drug 5FU was investigated at pH 5 and physiological pH 7.4. Present studies have shown that the drug release was high at pH 5 compared to pH 7.4. Compared to IN·FA@5FU the drug release of CuTu@5FU is significantly less at pH 5. Due to high 5FU release at acidic pH, the IN·FA@5FU has more advantage than the CuTu@5FU to the treatment of cancer cells. The promising results of in-situ drug loading in the MOGs and drug release provides a good candidates for future drug delivery applications.

Rational Design of Metal-Organic Frameworks/Gels As Efficient Catalysts for Oxygen Reduction Reaction

The growing pollution and energy crisis emphasize the need for the development of clean energy, such as fuel cells and metal-air batteries, in order to reduce the dependence on fossil fuels. In such clean energy devices, oxygen reduction reaction (ORR) is a key process in determining practical performance. Unfortunately it suffers from sluggish kinetics, resulting in large overpotentials and high efficiency penalties. To address this issue, rational design of non-precious metal catalysts with ORR performance comparable or even superior to precious metal is much needed. Metal-organic frameworks (MOFs) are porous crystalline materials assembled from metal nodes and organic linkers. MOFs possess high surface areas, open metal sites, and tunable pore structures, and are therefore promising for ORR electrocatalysis, in pristine phases or as self-sacrificial templates (Fig. 1A). Besides MOFs, another class of metal-organic coordinated materials that are of great interest are metal-organic gels (MOGs). MOGs are viscoelastic solid-like materials assembled by metal-organic coordination in conjunction with other interactions. MOGs possess great inclusion properties, design flexibility and ease in synthesis, highlighting themselves as precursors for producing ORR electrocatalysts (Fig. 1A). Herein, a series of MOFs/MOGs has been synthesized for ORR electrocatalysis. The catalytic ORR performance of the catalysts was evaluated through a rotating disk electrode technique, and the corresponding voltammograms are summarized in Fig. 1B. Several catalysts exhibit ORR activity comparable or greater than that of a commercial Pt/C benchmark, suggesting rational design approach of MOFs/MOGs offers a general solution for production of highly effective non-precious ORR electrocatalysts. Figure 1

MOG-derived porous FeCo/C nanocomposites as a potential platform for enhanced catalytic activity and lithium-ion batteries performance

The transition metal alloy nanoparticles (NPs) have received significant attention because of their unique physicochemical properties as well as low cost. Herein, we report a facile and clean synthetic route to prepare porous FeCo/C bimetallic alloy nanocomposites by using metal-organic gels (MOGs) as precursors. The bimetallic MOGs based on iron and cobalt bridged by tri-carboxylate organic ligands were first synthesized by a general and fast solvothermal method. The desired FeCo/C nanocomposites were then obtained by a one-step annealing process in which MOGs served as both the precursor and the self-sacrificing template. Significantly, the as-synthesized FeCo/C nanocomposites exhibit excellent catalytic activity and lithium-ion batteries performance. This fast and clean synthetic strategy is extended to synthesis diversity and range of potential applications of porous carbon-coated transition-metal alloy nanocomposites.

Metathesis in Metal–Organic Gels (MOGs): A Facile Strategy to Construct Robust Fluorescent Ln‐MOG Sensors for Antibiotics and Explosives

It is essential to develop new effective sensor materials for the detection of antibiotics and organic explosives, due to their negative impacts on ecosystems and human health. In this work, guided by an in situ metal‐node metathesis approach, a fluorescent metal–organic gel [MOG(Eu) gel] has been synthesized for the first time by metal‐ion exchange between Eu3+ and Al3+ in the nonfluorescent MOG(Al) gel. More importantly, the postsynthetic MOG(Eu) xerogel shows remarkable selective detection ability towards ronidazole (RDZ), ornidazole (ODZ), metronidazole (MDZ), and dimetridazole (DTZ) antibiotics, as well as 4‐nitrophenol (4‐NP), with low detection limits of 1.205, 0.542, 0.999, 0.377, and 1.582 ppm, respectively. The high quenching efficiencies can be attributed to the decrease of effective energy transfer in the host–guest systems. The strategy of metathesis opens up new opportunities for synthetic methods and functional applications in MOGs materials.

Synthesis of novel nanoporous metal-organic gels with tunable porosity and sensing of aromatic compounds

Herein we report the bottom up design of novel porous metal-organic gels (MOGs) Fe-ndc (H2ndc – 2,6-naphthalene dicarboxylic acid) and Fe-btc (H4btc - 1,2,4,5-benzenetetracarboxylic acid) based on Fe3+. The effective strategy to obtain MOGs with controllable porosity by changing the concentrations of precursors was studied. The MOGs were dried in vacuum and the resultant xerogels were fully characterized using PXRD, TGA, FT-IR spectroscopy and SEM techniques. The resultant materials demonstrated a wide range of BET surface area 0–290 m2/g. Presence of micro (<2 nm), meso (2–50 nm) and macropores (>50 nm) in obtained xerogels was found. Furthermore, Fe-ndc demonstrated strong dependence of photoluminescence properties on the nature of the guest molecules. A unique enhancement effect of maximum luminescence intensity of the host framework Fe-ndc in the presence of toluene (862%). Introduction of benzene led to just 42% increase of luminescence intensity of material compared to Fe-ndc. Quenching effects of maximum luminescence intensity of the host framework upon introduction of nitrobenzene (67%) and 1,3-dinitrobenzene (46%) were found. These features make Fe-ndc an efficient fluorescent material for selective detection of hazardous highly energetic aromatic compounds.

A water-stable Tb(iii)-based metal–organic gel (MOG) for detection of antibiotics and explosives

A luminescent Tb-based metal organic gel was prepared by in situ metal node metathesis and it exhibited sensitive detection ability effectively towards antibiotics and explosives in water.

Melamine formaldehyde–metal organic gel interpenetrating polymer network derived intrinsic Fe–N-doped porous graphitic carbon electrocatalysts for oxygen reduction reaction

Melamine formaldehyde metal organic gel interpenetrating networks for heteroporous Fe–N-doped carbon.

A metal–organic gel based on Fe(iii) and bi-pyridine ligand for template synthesis of core/shell composite polymer nanowires

In this study, a novel self-assembled metal-organic gel was synthesized from ferric nitrate and a di-topic ligand, bis(3-pyridyl)terephthalate. The gel consisted of a three dimensional network of uniform nanofibers. The gelation exhibited high selectivity to Fe(iii) based on metal-ligand coordination. The molar ratio of Fe3+ to ligand had a large influence on the assembly process and the morphology of the gel. The metallogel displayed multi-stimuli responsiveness and excellent heat resistance, thus was further applied as a thermo-stable template for the polymerization of N,N'-methylene bisacrylamide to produce the core/shell polymer composite nanowires. Subsequently, the polymer nanotubes were obtained after ammonia post-treatment, comfirming the feasibility of the template synthesis strategy. According to the rheological measurements, the gel-like products of the composite nanowires exhibited better mechanical strength compared to the gel template.

Carboxyphenyl-terpyridine-based series of gels for procedural visual recognition of multi-anions

The gelation of 4-[2,2′:6′,2′′-terpyridine]-4′-ylbenzoic acid (Hcptpy) occurred with various metal ions and specific anions. With the gel formation, corresponding metal ions and anions were recognized. Also, the metal–organic gels (MOGs) possess stimuli response property to anions. A step-by-step anion recognition progress was established based on one Hcptpy ligand and realized the selective identification 12 kinds of anions.

Porous metal–organic gel assisted by l-tartaric acid ligand for efficient and controllable drug delivery

The synthetic route for drug carriers based on porous Al-MOG.

Polyoxometalate encapsulated in metal‐organic gel as an efficient catalyst for visible‐light‐driven dye degradation applications

Contamination of industrial sewage by organic dye pollutants is one of the most common challenges to the daily life. Decontamination can be achieved by adsorption and photodegradation of the pollutants. Herein, an effective visible light‐driven photocatalyst of polyoxometalate encapsulated in metal–organic gel was presented. The resulting composite was named PMA@ MOG‐Cr [PMA= H3PMo12O40, MOG= metal‐organic gel]. Photodegradation of dye pollutants with PMA@ MOG‐Cr were tested. The introduction of Phosphomolybdic Acid significantly enhanced the light‐absorption properties of MOG‐Cr. The PMA@MOG‐Cr showed an excellent photodegradation efficiency of MB, RhB and MO as high as 99% and 97% in 60 min and 91% in 120 min of visible‐light irradiation with only 10 mg photocatalyst, which was the highest among the tested samples MOG‐Cr, PMA@ MOG‐Cr and Degussa P‐25. The mechanism of the photodegradation of dye pollutants with H2O2 over PMA@MOG‐Cr under the visible light was further illustrated. The introduction of PMA promotes effective separation of electron–hole pair by trapping and transferring photogenerated electron. Thus, the two components act in synergy to result in much improved adsorption of certain common organic dyes as well as enhanced oxidative degradation. This work provides a new approach to design MOG encapsulated Polyoxometalate for visible light‐induced photodegradation of organic contaminants for the environmental remediation.

A one-step in-situ assembly strategy to construct PEG@MOG-100-Fe shape-stabilized composite phase change material with enhanced storage capacity for thermal energy storage

A novel in-situ assembly strategy has been developed to synthesis polyethylene glycol (PEG)@iron-benzenetricarboxylate metal-organic gel (MOG-100-Fe) shape-stabilized composite phase change materials by regulating metal-to-ligand ratio. The PEG@MOG-100-Fe was prepared by an ingenious introduction of PEG into the traditional sol-gel prepared MOG-100-Fe. The composite exhibited high heat storage density and thermal stability. The PEG loading content reached up to 92% without any leakage above its melting point. The heat storage density reaches to 152.88 kJ kg−1 and is up to 95.8% of their theoretical value. These novel composite PCMs also exhibited excellent recyclability after 50 thermal cycles.

High Salt Removal Capacity of Metal–Organic Gel Derived Porous Carbon for Capacitive Deionization

Fresh water shortage poses serious threats to humanity. Capacitive deionization (CDI) holds promise for water desalination. Here, porous carbon derived from Al-based metal–organic gels (MOGs) upon calcination has been originally developed as electrodes for capacitive deionization. The obtained material with a large specific surface area, a large percentage of micropore, and a suitable pore size distribution favors slat ion accessibility. Its desalination performance is investigated under various operation conditions. Excitingly, this material displays a remarkable salt removal capacity of 25.16 mg g–1 in a 500 mg L–1 aqueous sodium chloride solution at 1.4 V, superior to those of the recently reported carbon materials. Moreover, the obtained electrode material also exhibits a high salt removal rate and an excellent recycling stability. The results demonstrate that MOG-derived carbon is an appealing candidate as an efficient electrode material in the CDI process for brackish and seawater desalination.

Metal-organic gel enhanced fluorescence anisotropy for sensitive detection of prostate specific antigen

In this contribution, we demonstrated that Cu-based metal-organic gel (Cu-MOG) was able to serve as a novel amplification platform for fluorescence anisotropy (FA) assay for the first time, which was confirmed by the sensitive detection of a common cancer biomarker, prostate specific antigen (PSA). The dye-labeled probe aptamer (PA) product was adsorbed onto the benzimidazole derivative-containing Cu-MOG via electrostatic incorporation and strong π-π stacking interactions, which significantly increased the FA value due to the enlargement of the molecular volume of the PA/Cu-MOG complex. With the introduction of target PSA, the FA value was obviously decreased on account of the specific recognition between PSA and PA which resulted in the detachment of PA from the surface of MOG. The linear range was from 0.5–8ng/mL, with a detection limit of 0.33ng/mL. Our work has thus helped to demonstrate promising application of MOG material in the fields of biomolecules analysis and disease diagnosis.

Tb-containing metal-organic gel with high stability for visual sensing of nitrite

A Tb-containing metal-organic gel (Tb-MOG) with excellent photoluminescence properties was synthesized via simple mixing of Tb3+ as the central metal ions and 4-[2, 2′:6′, 2″-terpyridine]-4′-ylbenzoic acid (Hcptpy) as the ligands under a mild condition. The Tb-MOG exhibits mechano reversibility, thermal stability, acid and alkali tolerance. Moreover, the MOG shows a specific sensing to nitrite based on energy transfer. Test papers containing Tb-MOG were prepared and successfully realised the selective visual recognition of nitrite, which makes the MOG as a sensor more adaptive to practical application.

Chitosan Intercalated Metal Organic Gel as a Green Precursor of Fe Entrenched and Fe Distributed N-Doped Mesoporous Graphitic Carbon for Oxygen Reduction Reaction

Chitosan Intercalated Metal Organic Gel as a Green Precursor of Fe Entrenched and Fe Distributed N-Doped Mesoporous Graphitic Carbon for Oxygen Reduction Reaction

Novel Iron(III)-Based Metal-Organic Gels with Superior Catalytic Performance toward Luminol Chemiluminescence.

Novel metal-organic gels (MOGs) consisting of iron (Fe3+) as the central ion and 1,10-phenanthroline-2,9-dicarboxylic acid (PDA) as the ligand were synthesized by a mild facile strategy. The Fe(III)-containing metal-organic xerogels (Fe-MOXs), obtained after removing the solvents in MOGs, were found to exhibit outstanding performance in the catalysis of luminol chemiluminescence (CL) for the first time even in the absence of extra oxidants such as hydrogen peroxide. The possible CL mechanism was discussed according to the electro/optical measurements, including electron paramagnetic resonance (EPR), UV-vis absorption, and CL spectra, as well as the effects of radical scavengers on Fe-MOXs-catalyzed luminol CL system, suggesting that the CL emission of luminol might originate from the intrinsic oxidase-like catalytic activity of Fe-MOXs on the decomposition of dissolved oxygen. Additionally, the potential practical application of the resulting luminol-Fe-MOXs system was evaluated by the quantitative analysis of dopamine. Good linearity over the range from 0.05 to 0.6 μM was obtained with the limit of detection (LOD, 3σ) of 20.4 nM and acceptable recoveries ranging from 98.6 to 105.4% in human urine. These results may open up the promising application of novel metal-organic gels as highly effective catalysts in the field of chemiluminescence.