Dual-Ligand Strategy to Construct Metal Organic Gel Catalyst with the Optimized Electronic Structure for High-Efficiency Overall Water Splitting and Flexible Metal-Air Battery.

Non-noble metal catalysts are known for their efficient catalytic performance for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Metal organic gels (MOGs) can be considered as a promising electrocatalyst owing to the diverse physicochemical properties but usually suffer from its poor electrical conductivity and catalytic stability. Here, a FeCo-MOG is constructed with considerable trifunctional activity. The optimal P-CoFe-H3 prepared by using phytic acid (PA) and 2,4,6-Tris[(p-carboxyphenyl)amino]-1,3,5-triazine benzoic acid (H3TATAB) as dual ligands), exhibits outstanding ORR, OER, and HER activities as well as stability, exceeding most of state-of-the-art catalysts. As expected, the flexible Zn-air battery applied with P-CoFe-H3 as air cathode displays considerable power density, discharge voltage plateau, and cycling stability. Impressively, it is also capable of driving the overall water-splitting device by applying the P-CoFe-H3 as anode and cathode. Furthermore, theoretical calculations reveal that dual ligands can optimize the coordination environment and charge density of active sites, thereby reducing the absorption energy of intermediate species and boosting the catalytic performance. This work endows the dual-ligands coordination strategy with great potentiality for MOGs-based electrocatalysts in energy conversion devices.

Comprehensive insight into adsorption of chlortetracycline hydrochloride by room-temperature synthesized water-stable Zr-based metal-organic gel/sodium alginate beads.

Chlortetracycline hydrochloride (CTC) is one of the prevailing antibiotic pollutants that harm both environmental ecosystem and human health. Herein, Zr-based metal-organic gels (Zr-MOGs) with lower-coordinated active sites and hierarchically porous structures are fabricated via a facile straightforward room-temperature strategy for CTC treatment. More importantly, we incorporated the powder Zr-MOGs into low-cost sodium alginate (SA) matrix to achieve shaped Zr-based metal-organic gel/SA beads for enhancing the adsorption ability and ameliorating the recyclability. The Langmuir maximum adsorption capacities of Zr-MOGs and Zr-MOG/SA beads could reach 143.9 mg/g and 246.9 mg/g, respectively. What's more, in the manual syringe unit and continuous bead column experiments, Zr-MOG/SA beads could achieve an eluted CTC removal ratio as high as 96.3% and 95.5% in the river water sample, respectively. On top of that, the adsorption mechanisms were put forward as a combination of pore filling, electrostatic interaction, hydrophilic-lipophilic balance, coordination, π-π interaction as well as hydrogen bonding interaction. This study outlines a workable strategy for the facile preparation of candidate adsorbents for wastewater treatment.

Competitive substitution in europium metal-organic gel for signal-on electrochemiluminescence detection of dipicolinic acid.

Metal-organic gels (MOGs) emerged as an attractive luminescent soft material for electrochemiluminescence (ECL). In this work, a cathodic ECL-activated europium metal-organic gel (Eu-MOG) has been synthesized by a facile mixing of Eu3+ with 4'-(4-carboxyphenyl)-2,2':6',2''-terpyridine (Hcptpy) under mild conditions. The prepared Eu-MOG is highly mesoporous for co-reactant permeation to produce an ultra-stable and high-efficient ECL, based on the antenna effect of Eu3+ coordinating with Hcptpy. Moreover, dipicolinic acid (DPA) can competitively coordinate with Eu3+ instead of water molecules, producing an enhanced ECL signal. Therefore, an ECL enhancement assay was developed for DPA detection. There was a linear relationship between the ECL intensity and the logarithmic concentration of DPA in the 0.01-1 µM range, and the detection limit is 7.35 nM. This work displays the promising application of Eu-MOG in the ECL field, opening a broad inspection for seeking a new generation of ECL luminophores.

Recent advances in process engineering and upcoming applications of metal-organic frameworks.

Progress in metal-organic frameworks (MOFs) has advanced from fundamental chemistry to engineering processes and applications, resulting in new industrial opportunities. The unique features of MOFs, such as their permanent porosity, high surface area, and structural flexibility, continue to draw industrial interest outside the traditional MOF field, both to solve existing challenges and to create new businesses. In this context, diverse research has been directed toward commercializing MOFs, but such studies have been performed according to a variety of individual goals. Therefore, there have been limited opportunities to share the challenges, goals, and findings with most of the MOF field. In this review, we examine the issues and demands for MOF commercialization and investigate recent advances in MOF process engineering and applications. Specifically, we discuss the criteria for MOF commercialization from the views of stability, producibility, regulations, and production cost. This review covers progress in the mass production and formation of MOFs along with future applications that are not currently well known but have high potential for new areas of MOF commercialization.

Self-Foaming Metal-Organic Gels Based on Phytic Acid and Their Mechanical, Moldable, and Load-Bearing Properties.

A catalogue of metal-organic gels are synthesized from phytic acid (PA) and a diversity of metal ions (Fe3+ , Cr3+ , Al3+ , Ce3+ , Y3+ , Co2+ , Ni2+ , Mn2+ , Cu2+ , Zn2+ , Mg2+ ) upon heating at 80 °C. PA-M gels have various morphologies, including irregular granular (PA-Fe, PA-Al, PA-Ce, PA-Cr, PA-Ni, PA-Co), spongy (PA-Y), and hollow tremella-like (PA-Cu) morphologies. Interestingly for PA-Fe-1 : 4 (PA:Fe3+ =1 : 4) a large amount of gas is generated during the gelation process leading to a self-foaming gel. The PA-Fe-1 : 4 self-foaming gel shows reversible gel-sol phase transition. The gel is unusually weakened and transformed into a sol at room temperature, and the sol is reversed to gelation when heated again at 80 °C. PA-Fe-1 : 4 gel also shows shapeable and load-bearing properties, and it can bear up to 200 times of its weight, depending on the gas amount fixed in the foam gel and the aging time. This work provides a catalogue of self-foaming supramolecular gels with tunable properties based on naturally abundant resources.

Pathway Dependence in Redox-Driven Metal-Organic Gels.

Pathway dependence is common in self-assembly. Herein, the importance of pathway dependence for redox-driven gels is shown by constructing a FeII /FeIII redox-based metal-organic gel system is shown. In situ oxidation of the FeII ions at different rates results in conversion of a FeII gel into a FeIII organic gel, which controls the material properties, such as gel stiffness, gel strength, and an unusual swelling behaviour, is described. The rate of formation of FeIII ions determines the extent of intermolecular interactions and so whether gelation or precipitation occurs.

Molecularly Imprinted Polymers Doped with Carbon Nanotube with Aid of Metal-Organic Gel for Drug Delivery Systems.

PURPOSE: The incidence of breast cancer worldwide has been on the rise since the late 1970s, and it has become a common tumor that threatens women's health. Aminoglutethimide (AG) is a common treatment of breast cancer. However, current treatments require frequent dosing that results in unstable plasma concentration and low bioavailability, risking serious adverse reactions. Our goal was to develop a molecularly imprinted polymer (MIP) based delivery system to control the release of AG and demonstrate the availability of this drug delivery system (DDS), which was doped with carbon nanotube with aid of metal-organic gel. METHODS: Preparation of MIP was optimized by key factors including composition of formula, ratio of monomers and drug loading concentration. RESULTS: By using multi-walled carbon nanotubes (MWCNT) and metal-organic gels (MOGs), MIP doubled the specific surface area, pore volume tripled and the IF was 1.6 times than the reference. Compared with commercial tablets, the relative bioavailability was 143.3% and a more stable release appeared. CONCLUSIONS: The results highlight the influence of MWCNT and MOGs on MIP, which has great potential as a DDS.

Metal-Organic Gel-Derived Fex Oy /Nitrogen-Doped Carbon Films for Enhanced Lithium Storage.

The development of cost-effective and flexible electrodes is demanding in the field of energy storage. Herein, flexible Fex Oy /nitrogen-doped carbon films (Fex Oy /NC-MOG) are prepared by facile electrospinning of Fe-based metal-organic gels (MOGs) followed by high-temperature carbonization. This approach allows the even mixing of fragile coordination polymers with polyacrylonitrile into flexible films while reserving the structural characteristics of coordination polymers. After thermal treatment, Fex Oy /NC-MOG films possess uniformly distributed Fex Oy nanoparticles and larger accessible surface areas than traditional Fex Oy -NC films without MOG. Taking advantage of the unique structure, Fex Oy /NC-MOG exhibits a superior rate performance (449.8 mA h g-1 at 5000 mA g-1 ) and long cycle life (629.3 mA h g-1 after 500 cycles at 1000 mA g-1 ) when used as additive-free anodes in lithium-ion batteries.

Effective Separation of Enantiomers Based on Novel Chiral Hierarchical Porous Metal-Organic Gels.

Metal-organic gel (MOG) matrices with tunable pore sizes ranging from micropore to macropore, derived from microporous metal-organic coordination polymers (PCPs), has attracted great attention for their enhanced pore accessibility compared with the multifunctional PCP materials themselves. The enhanced pore accessibility of chiral MOGs is especially imperative for mass transfer applications, including enantioseparations and purifications. Here, for the first time, a novel hierarchical porous MOG-coated SiO2 , derived from a chiral metal-organic coordination polymer, is employed as chiral stationary phase for effective high-performance liquid chromatography (HPLC) separation of enantiomers. The selected enantiomers with diverse functional groups are all efficiently separated in a few minutes with significantly higher resolution.

Self-Sorting of Metal-Organic Polymeric Assemblies in Gels: Selective Templation and Catalysis of Homodimers.

The development of generic strategy is essential for the construction of higher order supramolecular assemblies from the mixture of molecular components. Such higher order aggregations are possible through a self-sorting phenomenon, which is not well-explored in gel materials. Here, first examples of self-sorting in the coordination polymer (CP) based gels have been explored using three and four component systems. The self-sorting phenomenon has been monitored through a [2+2] photochemical reaction in the gel state and characterized by 1 H NMR, diffuse reflectance spectroscopy (DRS) and single crystal XRD analyses. Furthermore, AgI was shown to act as a supramolecular catalyst for the [2+2] photochemical reaction in gels.

An Encyclopedic Compendium on Chemosensing Supramolecular Metal-Organic Gels.

Chemosensing, an interdisciplinary scientific domain, plays a pivotal role ranging from environmental monitoring to healthcare diagnostics and (inter)national security. Metal-organic gels (MOGs) are recognized for their stability, selectivity, and responsiveness, making them valuable for chemosensing applications. Researchers have explored the development of MOGs based on different metal ions and ligands, allowing for tailored properties and sensitivities, and have even demonstrated their applications as portable sensors such as paper-based test strips for practical use. Herein, several studies related to MOGs development and their applications in the chemosensing field via UV-visible or luminance along with electrochemical approach are presented. These papers explored MOGs as versatile materials with their use in sensing bio or environmental analytes. This review provides a foundational understanding of key concepts, methodologies, and recent advancements in this field, fostering the scientific community.

Metal-Organic Gel Leading to Customized Magnetic-Coupling Engineering in Carbon Aerogels for Excellent Radar Stealth and Thermal Insulation Performances.

Metal-organic gel (MOG) derived composites are promising multi-functional materials due to their alterable composition, identifiable chemical homogeneity, tunable shape, and porous structure. Herein, stable metal-organic hydrogels are prepared by regulating the complexation effect, solution polarity and curing speed. Meanwhile, collagen peptide is used to facilitate the fabrication of a porous aerogel with excellent physical properties as well as the homogeneous dispersion of magnetic particles during calcination. Subsequently, two kinds of heterometallic magnetic coupling systems are obtained through the application of Kirkendall effect. FeCo/nitrogen-doped carbon (NC) aerogel demonstrates an ultra-strong microwave absorption of - 85 dB at an ultra-low loading of 5%. After reducing the time taken by atom shifting, a FeCo/Fe3O4/NC aerogel containing virus-shaped particles is obtained, which achieves an ultra-broad absorption of 7.44 GHz at an ultra-thin thickness of 1.59 mm due to the coupling effect offered by dual-soft-magnetic particles. Furthermore, both aerogels show excellent thermal insulation property, and their outstanding radar stealth performances in J-20 aircraft are confirmed by computer simulation technology. The formation mechanism of MOG is also discussed along with the thermal insulation and electromagnetic wave absorption mechanism of the aerogels, which will enable the development and application of novel and lightweight stealth coatings.

Modulation of defects in metal organic gels to enhance anhydrous proton conduction from subzero to moderate temperature.

Exploitation of solid-state proton-conducting materials with high anhydrous proton conductivity from subzero temperature (<273 K) to moderate temperature (>353 K) is a great challenge. Here, Brönsted acid-dopped zirconium-organic xerogels (Zr/BTC-xerogels) are prepared for anhydrous proton conduction from subzero to moderate temperature. Abundant acid sites and strong H-bonding interactions make the CF3SO3H (TMSA)-introduced xerogel gain high proton conductivity from 9.0 × 10-4 S cm-1 (253 K) to 1.40 × 10-2 S cm-1 (363 K) under anhydrous conditions, which are in the leading level. This provides a new possibility to develop wide-operating-temperature conductors.

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.

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.

Facile synthesis of dual-ligand terbium-organic gels as ratiometric fluorescence probes for efficient mercury detection.

Mercury (Hg) pollution can negatively impact ecosystems, and there is a need for simple Hg2+ monitoring platforms. Here, a dual-ligand fluorescence probe based on terbium-organic gels (Tb-L0.2P0.8 MOGs) was constructed for efficient Hg2+ detection. Tb-L0.2P0.8 MOGs were developed through a facile room-temperature gelation method, showing two emission peaks derived from luminol and Tb3+ at 424 nm and 544 nm, respectively. The aggregation-induced emission (AIE) effect between luminol and Tb3+ led to luminol with blue fluorescence. However, Hg2+ could dramatically quench the fluorescence signal of luminol at 424 nm because of the intense coordination interaction of Hg2+ with luminol and photo-induced electron transfer (PET). The Phen ligand could sensitize the luminescence of Tb3+ and offer a reference fluorescence, thus resulting in a unique ratiometric fluorescence response toward Hg2+. This novel nanoprobe had excellent linearity with Hg2+ concentrations range of 0.1-30 µM; the detection limit was 3.6 nM. The analysis of real samples showed the potential application of MOGs for measuring Hg2+ in porphyra and tap water. Mixed ligands were introduced for high-efficiency strategies to improve the analytical performance by regulating the emission behavior of MOGs.

Phytic Acid-Based FeCo Bimetallic Metal-Organic Gels for Electrocatalytic Oxygen Evolution Reaction.

Electrocatalysts have been developed to improve the efficiency of gas release for oxygen evolution reaction (OER), and finding a simple and efficient method for efficient electrocatalysts has inspired research enthusiasm. Herein, we report bimetallic metal-organic gels derived from phytic acid (PA) and mixed transition metal ions to explore their performance in electrocatalytic oxygen evolution reaction. PA is a natural phosphorus-rich organic compound, which can be obtained from plant seeds and grains. PA reacts with bimetallic ions (Fe3+ and Co2+ ) in a facile one-pot synthesis under mild conditions to form PA-FeCo bimetallic gels, and the corresponding aerogels are further partially reduced with NaBH4 to improve the electrocatalytic activity. Mixed valence states of Fe(II)/Fe(III) and Co(III)/Co(II) are present in the materials. Excellent OER performance in terms of overpotential (257 mV at 20 mA cm-2 ) and Tafel slope (36 mV dec-1 ) is achieved in an alkaline electrolyte. This reduction method is superior to the pyrolysis method by well maintaining the gel morphology structure. This strategy is conducive to the further improvement of the performance of metal-organic electrocatalysts, and provides guidance for the subsequent application of metal-organic gel electrocatalysts.

Metal-Organic Frameworks and Metal-Organic Gels for Oxygen Electrocatalysis: Structural and Compositional Considerations.

Increasing demand for sustainable and clean energy is calling for the next-generation energy conversion and storage technologies such as fuel cells, water electrolyzers, CO2 /N2 reduction electrolyzers, metal-air batteries, etc. All these electrochemical processes involve oxygen electrocatalysis. Boosting the intrinsic activity and the active-site density through rational design of metal-organic frameworks (MOFs) and metal-organic gels (MOGs) as precursors represents a new approach toward improving oxygen electrocatalysis efficiency. MOFs/MOGs afford a broad selection of combinations between metal nodes and organic linkers and are known to produce electrocatalysts with high surface areas, variable porosity, and excellent activity after pyrolysis. Some recent studies on MOFs/MOGs for oxygen electrocatalysis and their new perspectives in synthesis, characterization, and performance are discussed. New insights on the structural and compositional design in MOF/MOG-derived oxygen electrocatalysts are summarized. Critical challenges and future research directions are also outlined.

Cu (II)-based metal-organic xerogels as a novel nanozyme for colorimetric detection of dopamine.

Cu (II)-based metal-organic gels (Cu-MOGs), which are formed by 4-[2,2':6',2″-terpyridine]-4'-ylbenzoic acid (Hcptpy) and Cu (II) through ionic interactions, π-π stacking, van der Waals and hydrogen bonding, have been simply synthesized and used for the preparation of Cu (II)-based metal-organic xerogels (Cu-MOXs). Owing to the metal active sites in Cu-MOXs, Cu-MOXs were successfully applied to chromogenic experiment. The peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB), which could be catalyzed by Cu-MOXs from TMB to the oxidation state of TMB (oxTMB) and the color of TMB could be changed from colorless to blue with maximum absorbance at 657 nm, was selected as chromogenic agent. Thus, the Cu-MOXs-TMB-H2O2 system based on MOXs was established. Due to the inhibitory effect of dopamine (DA) on oxidation process of TMB, the characteristic absorption peak intensity of oxTMB decreased when the DA was added into the mixed solution. Subsequently, the Cu-MOXs-TMB- H2O2 system was used for DA detection. The linear range for DA was 0.5 µM-20 µM and the detection limit was 85.76 nM. Our work has helped to develop the promising application of Cu-MOGs material in the field of nanozymes property.

Silver-based metal-organic gels as novel coreactant for enhancing electrochemiluminescence and its biosensing potential.

Metal-organic gels (MOGs), a kind of soft materials, were reported as a brand new category of novel solid coreactants for enhancing electrochemiluminescence (ECL) of Ru (bpy)32+ and derivatives. In this work, silver-based MOGs (Ag-MOGs) prepared by a one-step mixing and heating approach were demonstrated as novel efficient solid-state coreactants which differ from the previous research on ECL coreactant nanomaterials. It was discussed that the possible enhancement mechanism was due to the amino-rich groups and the electro-catalytic effect of Ag-MOGs, endowing them promising coreactants for the enhancement of Ru (bpy)32+ ECL. Interestingly, Ag-MOGs can also enhance the ECL signal of Ru (phen)32+, a derivative of Ru (bpy)32+ that can specifically insert into double strand DNA, further manifesting the as-prepared Ag-MOGs can be served as ideal coreactant materials. Based on the Ru (phen)32+/Ag-MOGs system, a label-free signal-on ECL biosensor for detecting of target DNA was constructed to illustrate the potential application of Ag-MOGs. This research presents an effective coreactant for Ru luminophore-based ECL systems, which not only broadens the potential application of MOGs, but also offers a unique insight into the coreactant materials.