Trimetallic metal–organic frameworks and derived materials for environmental remediation and electrochemical energy storage and conversion

Enzymeless detection and real-time analysis of intracellular hydrogen peroxide released from cancer cells using gold nanoparticles embedded bimetallic metal organic framework

Abnormal cell growth and proliferation can lead to tumor formation and cancer, one of the most fatal diseases worldwide. Hydrogen peroxide (H2O2) has emerged as a cancer biomarker, with its concentration being crucial for distinguishing cancer cells from normal cells. Herein, a cost-effective and enzymeless electrochemical sensing system for the monitoring of intracellular H2O2 has been constructed. The sensor is fabricated using gold nanoparticles embedded bimetallic copper/nickel metal organic framework (Au-CNMOF) immobilized reduced graphene oxide (RGO) modified screen printed electrode (SPE). The synthesized materials were characterized and confirmed by XRD, FTIR, SEM with EDS, and electrochemical analysis. The fabricated sensor displayed a redox peak at a formal potential (E°) of -0.155 V, corresponding to CuII/I redox couple of CNMOF in 0.1 M phosphate buffer. Electrochemical investigations revealed that the proposed sensor has a large electrochemical active surface area (1.113 cm2) and a higher surface roughness (5.67). Additionally, the sensor demonstrated excellent electrocatalytic activity towards H2O2 at -0.3 V, over a wide linear detection range from 28.5 µM to 4.564 mM with a limit of detection of 4.2 µM (S/N=3). Furthermore, the proposed sensor exhibits excellent stability, repeatability, reproducibility, and good anti-interference activity. Ultimately, the sensor was validated through real-time analysis of H2O2 released from cancer cells, successfully quantifying the released H2O2. The developed sensor holds great promise for real-time H2O2 analysis, with potential applications in clinical diagnostics, biological research and environmental monitoring.

Multi-metallic MOF based composites for environmental applications: synergizing metal centers and interactions

The escalating threat of environmental issues to both nature and humanity over the past two decades underscores the urgency of addressing environmental pollutants. Metal-organic frameworks (MOFs) have emerged as highly promising materials for tackling these challenges. Since their rise in popularity, extensive research has been conducted on MOFs, spanning from design and synthesis to a wide array of applications, such as environmental remediation, gas storage and separation, catalysis, sensors, biomedical and drug delivery systems, energy storage and conversion, and optoelectronic devices, etc. MOFs possess a multitude of advantageous properties such as large specific surface area, tunable porosity, diverse pore structures, multi-channel design, and molecular sieve capabilities, etc., making them particularly attractive for environmental applications. MOF-based composites inherit the excellent properties of MOFs and also exhibit unique physicochemical properties and structures. The tailoring of central coordinated metal ions in MOFs is critical for their adaptability in environmental applications. Although many reviews on monometallic, bimetallic, and polymetallic MOFs have been published, few reviews focusing on MOF-based composites with monometallic, bimetallic, and multi-metallic centers in the context of environmental pollutant treatment have been reported. This review addresses this gap by providing an in-depth overview of the recent progress in MOF-based composites, emphasizing their applications in hazardous gas sensing, electromagnetic wave absorption (EMWA), and pollutant degradation in both aqueous and atmospheric environments and highlighting the importance of the number and type of metal centers present. Additionally, the various categories of MOFs are summarized. MOF-based composites demonstrate significant promise in addressing environmental challenges, and this review provides a clear and valuable perspective on their potential in environmental applications.

Recent advancements and prospects in noble and non-noble electrocatalysts for materials methanol oxidation reactions

The direct methanol fuel cell (DMFC) represents a highly promising alternative power source for small electronics and automobiles due to its low operating temperatures, high efficiency, and energy density. The methanol oxidation process (MOR) constitutes a fundamental chemical reaction occurring at the positive electrode of a DMFC. Pt-based materials serve as widely utilized MOR electrocatalysts in DMFCs. Nevertheless, various challenges, such as sluggish reaction rates, high production costs primarily attributed to the expensive Pt-based catalyst, and the adverse effects of CO poisoning on the Pt catalysts, hinder the commercialization of DMFCs. Consequently, endeavors to identify an alternative catalyst to Pt-based catalysts that mitigate these drawbacks represent a critical focal point of DMFC research. In pursuit of this objective, researchers have developed diverse classes of MOR electrocatalysts, encompassing those derived from noble and non-noble metals. This review paper delves into the fundamental concept of MOR and its operational mechanisms, as well as the latest advancements in electrocatalysts derived from noble and non-noble metals, such as single-atom and molecule catalysts. Moreover, a comprehensive analysis of the constraints and prospects of MOR electrocatalysts, encompassing those based on noble metals and those based on non-noble metals, has been undertaken.

Facile hydrothermal synthesis of a tri-metallic Cu-Mn-Ni oxide-based electrochemical pseudo capacitor

Transition metal oxide nanocomposites with heterostructures have gained a lot of attention for use in supercapacitors owing to their low cost, high surface area, fast transport of ions and electrons and high specific capacitance due to efficacious interplay between the electrode and the electrolytes. In this study, we fabricated tri-metallic Cu, Mn, Ni(CMNO), bi-metallic Mn, Ni(MNO) and mono-metallic Ni(NO) oxides through a facile hydrothermal route. All the fabricated materials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDX), and their electrochemical properties were studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD). The CMNO material showed remarkable electrochemical performance with a specific capacitance of 790.63 F g-1 at a current density of 1 A g-1, surpassing the performance of MNO (438.4 F g-1) and NO (290.82 F g-1). Furthermore, CMNO showed high cycling stability with a retention of 96.7% specific capacitance after 8000 cycles. Based on remarkable and unique properties, the CMNO material is regarded as a promising material for new-generation pseudo-capacitor applications.

Recent Functionalized Strategies of Metal-Organic Frameworks for Anode Protection of Aqueous Zinc-Ion Battery

The inherent benefits of aqueous Zn-ion batteries (ZIBs), such as environmental friendliness, affordability, and high theoretical capacity, render them promising candidates for energy storage systems. Nevertheless, the Zn anodes of ZIBs encounter severe challenges, including dendrite formation, hydrogen evolution reaction, corrosion, and surface passivation. These would result in the infeasibility of ZIBs in practical situations. To this end, artificial interfaces with functionalized materials are crafted to protect the Zn anode. They have the capability to modulate the zinc ion flux in proximity to the electrode surface and shield it from aqueous electrolytes by leveraging either size effects or charge effects. Considering metal-organic frameworks (MOFs) with tunable pore size, chemical composition, and stable framework structures, they have emerged as effective materials for building artificial interfaces, prolonging the lifespan, and improving the unitization of Zn anode. In this review, the contributions of MOFs for protecting Zn anode, which mainly involves facilitating homogeneous nucleation, manipulating selective deposition, regulating ion and charge flux, accelerating Zn desolvation, and shielding against free water and anions are comprehensively summarized. Importantly, the future research trajectories of MOFs for the protection of the Zn anode are underscored, which may propose new perspectives on the practical Zn anode and endow the MOFs with high-value applications.

An Oxalato-Bridged Cu(II)-Based 1D Polymer Chain: Synthesis, Structure, and Adsorption of Organic Dyes

In the current research, we prepared a polymeric framework, {[Cu(C2O4)(C10H8N2)]·H2O·0.67(CH3OH)]}n (1) (where C2O4 = oxalic acid; C10H8N2 = 2,2-bipyridine), and explored this compound for adsorption of methylene blue (MB) and methyl orange (MO). The crystal structure of the compound consists of a Cu(ox)(bpy) unit connected via oxalate to form a 1D polymeric chain. This polymeric chain has adsorption capacities of 194.0 and 167.3 mg/g for MB and MO, respectively. The removal rate is estimated to be 77.6% and 66.9% for MB and MO, respectively. The plausible mechanisms for adsorption are electrostatic, π-π interaction, and OH-π interaction for dye stickiness. The adsorbent surface exhibits a negative charge that produces the electrostatic interaction, resulting in excellent adsorption efficiency at pH 7 and 8. The pseudo-first-order kinetic model is selected for the adsorption of MB and MO on the adsorbent. The reported compound has remarkable efficiency for sorption of organic dyes and can be useful in wastewater treatment.

Boosting Urea-Assisted Natural Seawater Electrolysis in 3D Leaf-Like Metal-Organic Framework Nanosheet Arrays Using Metal Node Engineering

Metal node engineering, which can optimize the electronic structure and modulate the composition of poor electrically conductive metal-organic frameworks, is of great interest for electrochemical natural seawater splitting. However, the mechanism underlying the influence of mixed-metal nodes on electrocatalytic activities is still ambiguous. Herein, a strategic design is comprehensively demonstrated in which mixed Ni and Co metal redox-active centers are uniformly distributed within NH2-Fe-MIL-101 to obtain a synergistic effect for the overall enhancement of electrocatalytic activities. Three-dimensional mixed metallic MOF nanosheet arrays, consisting of three different metal nodes, were in situ grown on Ni foam as a highly active and stable bifunctional catalyst for urea-assisted natural seawater splitting. A well-defined NH2-NiCoFe-MIL-101 reaches 1.5 A cm-2 at 360 mV for the oxygen evolution reaction (OER) and 0.6 A cm-2 at 295 mV for the hydrogen evolution reaction (HER) in freshwater, substantially higher than its bimetallic and monometallic counterparts. Moreover, the bifunctional NH2-NiCoFe-MIL-101 electrode exhibits eminent catalytic activity and stability in natural seawater-based electrolytes. Impressively, the two-electrode urea-assisted alkaline natural seawater electrolysis cell based on NH2-NiCoFe-MIL-101 needs only 1.56 mV to yield 100 mA cm-2, much lower than 1.78 V for alkaline natural seawater electrolysis cells and exhibits superior long-term stability at a current density of 80 mA cm-2 for 80 h.

Bimetallic Organic Frameworks via In Situ Solvothermal Sol-Gel-Crystal and Sol-Crystal Transformation as Durable Electrocatalysts for Oxygen Reduction Reaction

The in situ solvothermal conversion of metal-organic gels (MOGs) to crystalline metal-organic frameworks (MOFs) represents a versatile and ingenious strategy that has been employed for the synthesis of MOF materials with specific morphologies, high yield, and improved functional properties. Herein, we have adopted an in situ solvothermal conversion of bimetallic MOGs to crystalline bimetallic MOFs with the aim of introducing a redox-active metal heterogeneity into the monometallic counterpart. The formation of bimetallic NiZn-MOF and CoZn-MOF via in situ solvothermal sol-gel-crystal and sol-crystal transformation is found to depend on the solvent systems used. The sol-to-gel-to-crystal transformation of NiZn-MOF via the formation of NiZn-MOG is found to occur through the gradual disruption of gel fibers leading to subsequent formation of microcrystals and single crystals of NiZn-MOF. These bimetallic MOFs and MOGs serve as promising electrocatalysts for oxygen reduction reaction (ORR) with an excellent methanol tolerance property, which can be attributed to the enhanced mass and charge transfer, higher oxygen vacancies, and bimetallic synergistic interactions among the heterometals. This work demonstrates a convenient strategy for producing bimetallic MOGs to MOFs through the introduction of a redox-active metal heterogeneity in the inorganic hybrid functional materials for fundamental and applied research. Our results connect MOGs and MOFs which have been regarded as having opposite physical states, that is, soft vs hard, and provide promising structural correlation between MOGs and MOFs at the molecular level.

Role of transition metals in coinage metal nanoclusters for the remediation of toxic dyes in aqueous systems

A difficult issue in chemistry and materials science is to create metal compounds with well-defined components. Metal nanoclusters, particularly those of coinage groups (Cu, Ag, and Au), have received considerable research interest in recent years owing to the availability of atomic-level precision via joint experimental and theoretical methods, thus revealing the mechanisms in diverse nano-catalysts and functional materials. The textile sector significantly contributes to wastewater containing pollutants such as dyes and chemical substances. Textile and fabric manufacturing account for about 7 × 105 tons of wastewater annually. Approximately one thousand tons of dyes used in textile processing and finishing has been recorded as being discharged into natural streams and water bodies. Owing to the widespread environmental concerns, research has been conducted to develop absorbents that are capable of removing contaminants and heavy metals from water bodies using low-cost technology. Considering this idea, we reviewed coinage metal nanoclusters for azo and cationic dye degradation. Fluorometric and colorimetric techniques are used for dye degradation using coinage metal nanoclusters. Few reports are available on dye degradation using silver nanoclusters; and some of them are discussed in detailed herein to demonstrate the synergistic effect of gold and silver in dye degradation. Mostly, the Rhodamine B dye is degraded using coinage metals. Silver nanoclusters take less time for degradation than gold and copper nanoclusters. Mostly, H2O2 is used for degradation in gold nanoclusters. Still, all coinage metal nanoclusters have been used for the degradation due to suitable HOMO-LUMO gap, and the adsorption of a dye onto the surface of the catalyst results in the exchange of electrons and holes, which leads to the oxidation and reduction of the adsorbed dye molecule. Compared to other coinage metal nanoclusters, Ag/g-C3N4 nanoclusters displayed an excellent degradation rate constant with the dye Rhodamine B (0.0332 min-1). The behavior of doping transition metals in coinage metal nanoclusters is also reviewed herein. In addition, we discuss the mechanistic grounds for degradation, the fate of metal nanoclusters, anti-bacterial activity of nanoclusters, toxicity of dyes, and sensing of dyes.

Design and Advanced Manufacturing of NU-1000 Metal-Organic Frameworks with Future Perspectives for Environmental and Renewable Energy Applications

Metal-organic frameworks (MOFs) represent a relatively new family of materials that attract lots of attention thanks to their unique features such as hierarchical porosity, active metal centers, versatility of linkers/metal nodes, and large surface area. Among the extended list of MOFs, Zr-based-MOFs demonstrate comparably superior chemical and thermal stabilities, making them ideal candidates for energy and environmental applications. As a Zr-MOF, NU-1000 is first synthesized at Northwestern University. A comprehensive review of various approaches to the synthesis of NU-1000 MOFs for obtaining unique surface properties (e.g., diverse surface morphologies, large surface area, and particular pore size distribution) and their applications in the catalysis (electro-, and photo-catalysis), CO2 reduction, batteries, hydrogen storage, gas storage/separation, and other environmental fields are presented. The review further outlines the current challenges in the development of NU-1000 MOFs and their derivatives in practical applications, revealing areas for future investigation.

Multiscale Structured Trimetal Oxide Heterojunctions for Urinary Metabolic Phenotype-Dependent Screening of Early and Small Hepatocellular Carcinoma

Developing a standardized screening tool for the detection of early and small hepatocellular carcinoma (HCC) through urinary metabolic analysis poses a challenging yet intriguing research endeavor. In this study, a range of intricately interlaced 2D rough nanosheets featuring well-defined sharp edges is fabricated, with the aim of constructing diverse trimetal oxide heterojunctions exhibiting multiscale structures. By carefully engineering synergistic effects in composition and structure, including improved adsorption, diffusion, and other surface-driven processes, the optimized heterojunctions demonstrate a substantial enhancement in signal intensity compared to monometallic or bimetallic oxides, as well as fragmented trimetallic oxides. Additionally, optimal heterojunctions enable the extraction of high-quality urinary metabolic fingerprints using high-throughput mass spectrometry. Leveraging machine learning, discrimination of HCC patients from high-risk and healthy populations achieves impressive performance, with area under the curve values of 0.940 and 0.916 for receiver operating characteristic and precision-recall curves, respectively. Six crucial metabolites are identified, enabling accurate detection of early, small-tumor, alpha-fetoprotein-negative HCC (93.3%-97.3%). A comprehensive screening strategy tailored to clinical reality yields precision metrics (accuracy, precision, recall, and F1 score) exceeding 95.0%. This study advances the application of cutting-edge matrices-based metabolic phenotyping in practical clinical diagnostics.

Ultrafine Iridium Nanoparticles Anchored on Co-Based Metal-Organic Framework Nanosheets for Robust Hydrogen Evolution in Alkaline Media

A highly promising electrocatalyst has been designed and prepared for the hydrogen evolution reaction (HER). This involves incorporating well-dispersed Ir nanoparticles into a cobalt-based metal-organic framework known as Co-BPDC [Co(bpdc)(H2O)2, BPDC: 4,4'-biphenyldicarboxylic acid]. Ir@Co-BPDC demonstrates exceptional HER activity in alkaline media, surpassing both commercial Pt/C and recent noble-metal catalysts. Theoretical results indicate that electron redistribution, induced by interfacial bonds, optimizes the adsorption energy of water and hydrogen, thereby enhancing our understanding of the superior properties of Ir@Co-BPDC for HER.

Current Progress of Mo-Based Metal Organic Frameworks Derived Electrocatalysts for Hydrogen Evolution Reaction

As an important half-reaction for electrochemical water splitting, electrocatalytic hydrogen evolution reaction suffers from sluggish kinetics, and it is still urgent to search high efficiency non-platinum-based electrocatalysts. Mo-based catalysts such as Mo2 C, MoO2 , MoP, MoS2 , and MoNx have emerged as promising alternatives to Pt/C owing to their similar electronic structure with Pt and abundant reserve of Mo. On the other hand, due to the adjustable topology, porosity, and nanostructure of metal organic frameworks (MOFs), MOFs are extensively used as precursors to prepare nano-electrocatalysts. In this review, for the first time, the progress of Mo-MOFs-derived electrocatalysts for hydrogen evolution reaction is summarized. The preparation method, structures, and catalytic performance of the catalysts are illustrated based on the types of the derived electrocatalysts including Mo2 C, MoO2 , MoP, MoS2 , and MoNx . Especially, the commonly used strategies to improve catalytic performance such as heteroatoms doping, constructing heterogeneous structure, and composited with noble metal are discussed. Moreover, the opportunities and challenges in this area are proposed to guide the designment and development of Mo-based MOF derived electrocatalysts.

Mechanisms of interaction between metal-organic framework-based material and persulfate in degradation of organic contaminants (OCs): Activation, reactive oxygen generation, conversion, and oxidation

Metal-organic frameworks (MOFs)-based materials have been of great public interest in persulfate (PS)-based catalytic oxidation for wastewater purification, because of their excellent performance and selectiveness in organic contaminants (OCs) removal in complex water environments. The formation, fountainhead and reaction mechanism of reactive oxygen species (ROSs) in PS-based catalytic oxidation are crucial for understanding the principles of PS activation and the degradation mechanism of OCs. In the paper, we presented the quantitative structure-activity relationship (QSAR) of MOFs-based materials for PS activation, including the relationship of structure and removal efficiency, active sites and ROSs as well as OCs. In various MOFs-based materials, there are many factors will affect their performances. We discussed how various surface modification projects affected the characteristics of MOFs-based materials used in PS activation. Moreover, we revealed the process of ROSs generation by active sites and the oxidation of OCs by ROSs from the micro level. At the end of this review, we putted forward an outlook on the development trends and faced challenges of MOFs for PS-based catalytic oxidation. Generally, this review aims to clarify the formation mechanisms of ROSs via the active sites on the MOFs and the reaction mechanism between ROSs and OCs, which is helpful for reader to better understand the QSAR in various MOFs/PS systems.

Biosynthesis of ternary NiCoFe2O4 nanoflowers: investigating their 3D structure and potential use in gene delivery

Multicomponent nanoparticle systems are known for their varied properties and functions, and have shown potential as gene nanocarriers. This study aims to synthesize and characterize ternary nickel-cobalt-ferrite (NiCoFe2O4) nanoparticles with the potential to serve as gene nanocarriers for cancer/gene therapy. The biogenic nanocarriers were prepared using a simple and eco-friendly method following green chemistry principles. The physicochemical properties of the nanoparticles were analyzed by X-ray diffraction, vibrating sample magnetometer, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller. To evaluate the morphology of the nanoparticles, the field emission scanning electron microscopy with energy dispersive X-Ray spectroscopy, high-resolution transmission electron microscopy imaging, and electron tomography were conducted. Results indicate the nanoparticles have a nanoflower morphology with a mesoporous nature and a cubic spinel structure, where the rod and spherical nanoparticles became rose-like with a specific orientation. These nanoparticles were found to have minimal toxicity in human embryonic kidney 293 (HEK-293 T) cells at concentrations of 1 to 250 µg·mL-1. We also demonstrated that the nanoparticles could be used as gene nanocarriers for delivering genes to HEK-293 T cells using an external magnetic field, with optimal transfection efficiency achieved at an N/P ratio of 2.5. The study suggests that biogenic multicomponent nanocarriers show potential for safe and efficient gene delivery in cancer/gene therapy.

Water-Stable Fluorous Metal-Organic Frameworks with Open Metal Sites and Amine Groups for Efficient Urea Electrocatalytic Oxidation

Urea oxidation reaction (UOR) is one of the promising alternative anodic reactions to water oxidation that has attracted extensive attention in green hydrogen production. The application of specifically designed electrocatalysts capable of declining energy consumption and environmental consequences is one of the major challenges in this field. Therefore, the goal is to achieve a resistant, low-cost, and environmentally friendly electrocatalyst. Herein, a water-stable fluorinated Cu(II) metalorganic framework (MOF) {[Cu2 (L)(H2 O)2 ]·(5DMF)(4H2 O)}n (Cu-FMOF-NH2 ; H4 L = 3,5-bis(2,4-dicarboxylic acid)-4-(trifluoromethyl)aniline) is developed utilizing an angular tetracarboxylic acid ligand that incorporates both trifluoromethyl (-CF3 ) and amine (-NH2 ) groups. The tailored structure of Cu-FMOF-NH2 where linkers are connected by fluoride bridges and surrounded by dicopper nodes reveals a 4,24T1 topology. When employed as electrocatalyst, Cu-FMOF-NH2 requires only 1.31 V versus reversible hydrogen electrode (RHE) to deliver 10 mA cm-2 current density in 1.0 m KOH with 0.33 m urea electrolyte and delivered an even higher current density (50 mA cm-2 ) at 1.47 V versus RHE. This performance is superior to several reported catalysts including commercial RuO2 catalyst with overpotential of 1.52 V versus RHE. This investigation opens new opportunities to develop and utilize pristine MOFs as a potential electrocatalyst for various catalytic reactions.

Mesoporous MOF Based on a Hexagonal Bipyramid Co8-Cluster: High Catalytic Efficiency on the Cycloaddition Reaction of CO2 with Bulky Epoxides

A mesoporous cobalt-based metal-organic framework (LCU-606) was synthesized based on a hexagonal bipyramid Co8(μ4-O)3 cluster and an N,N,N',N'-tetrakis-(4-benzoic acid)-1,4-phenylenediamine ligand (H4TBAP). LCU-606 featuring large pore diameters of 21.7 Å and exposed Lewis-acid metal sites could serve as an excellent heterogeneous catalyst for CO2 cycloaddition reaction with various epoxide substrates under mild conditions (1 atm CO2, 60 °C, and solvent free). In particular, when extending the substrates to bulkier ones, LCU-606 still shows high catalytic efficiency on account of the large pore aperture. Also, LCU-606 demonstrates high recyclability and stability in consecutive catalytic runs. Therefore, the high efficiency, recyclability, and generality on CO2 catalytic cycloaddition make LCU-606 a very promising heterogeneous catalyst for CO2 chemical fixation.

Rapid cold plasma synthesis of cobalt metal-organic framework/reduced graphene oxide nanocomposites for use as supercapacitor electrodes

Metal-organic frameworks (MOFs) are recognized as a desirable class of porous materials for energy storage applications, despite their limited conductivity. In the present study, Co-MOF-71 was fabricated as a high-performance supercapacitor electrode at ambient temperature using a fast and straightforward, one-pot cold plasma method. A supercapacitor electrode based on Co-MOF@rGO was also synthesized by adding reduced graphene oxide (rGO) during processing to increase the capacitance retention and stability after 4000 cycles from 80 to 95.4%. The Co-MOF-71 electrode provided a specific capacitance (Cs) of 651.7 Fg-1 at 1 Ag-1, whereas the Co-MOF@rGO electrode produced a Cs value of 967.68 Fg-1 at 1 Ag-1. In addition, we fabricated an asymmetric device (Co-MOF@rGO||AC) using Co-MOF-rGO as a high-rate positive electrode and activated carbon (AC) as a negative electrode. This hybrid device has a remarkable specific energy and power density. The combination of MOFs with reduced graphene oxide (rGO) in a cold plasma environment resulted in the formation of a three-dimensional nanostructure composed of nanosheets. This nanostructure exhibited an increased number of electroactive sites, providing benefits for energy storage applications.

Porous nanosheet-nanosphere@nanosheet FeNi2-LDH@FeNi2S4 core-shell heterostructures for asymmetric supercapacitors

Transition bimetallic sulphides have emerged as important electrode materials for supercapacitors owing to their low toxicity, environmental friendliness, cost-effectiveness, multiple oxidation states, high natural abundance, flexible structure, and high theoretical specific capacitance. Herein, a porous nanosheet-nanosphere@nanosheet FeNi2-LDH@FeNi2S4 (FNLDH@FNS) core-shell heterostructure was directly prepared on nickel foam (NF) via a two-step hydrothermal method. The prepared electrode material exhibits an outstanding electrochemical performance. The specific capacity (Cs) values are 806 and 450 C g-1 at current density (Dc) values of 1 and 6 A g-1, respectively, revealing a satisfactory magnification performance. In addition, the FNLDH@FNS electrode exhibits a long cycle life with an supercapacitor (SC) retention rate of 92.3% after 5000 cycles at a Dc of 6 A g-1. The FNLDH@FNS//activated carbon (AC) asymmetric SC assembled with FNLDH@FNS (positive electrode) and activated carbon (AC, negative electrode) displays an energy density (Ed) of 36.67 Wh kg-1 and a power density (Pd) of 775.17 W kg-1.

Construction of Well-Defined Two-Dimensional Architectures of Trimetallic Metal-Organic Frameworks for High-Performance Symmetric Supercapacitors

The high surface-to-volume ratio and extraordinarily large-surface area of two-dimensional (2D) metal-organic framework (MOF) architectures have drawn particular interest for use in supercapacitors. To achieve an excellent electrode material for supercapacitors, well-defined 2D nanostructures of novel trimetallic MOFs were developed for supercapacitor applications. Multivariate MOFs (terephthalate and trimesate MOF) with distinctive nanobrick and nanoplate-like structures were successfully synthesized using a straightforward one-step reflux condensation method by combining Ni, Co, and Zn metal species in equimolar ratios with two different ligands. Furthermore, the effects of the tricarboxylic and dicarboxylic ligands on cyclic voltammetry, charge-discharge cycling, and electrochemical impedance spectroscopy were studied. The derived terephthalate and trimesate MOFs are supported with stainless-steel mesh and provide a suitable electrolyte environment for rapid faradaic reactions with an elevated specific capacity, excellent rate capability, and exceptional cycling stability. It shows a specific capacitance of 582.8 F g-1, a good energy density of 40.47 W h kg-1, and a power density of 687.5 W kg-1 at 5 mA cm-2 with an excellent cyclic stability of 92.44% for 3000 charge-discharge cycles. A symmetric BDC-MOF//BDC-MOF supercapacitor device shows a specific capacitance of 95.22 F g-1 with low capacitance decay, high energy, and power densities which is used for electronic applications. These brand-new trimetallic MOFs display outstanding electrochemical performance and provide a novel strategy for systematically developing high-efficiency energy storage systems.

A Dual-Purpose Ce(III)-Organic Framework with Amine Groups and Open Metal Sites: Third-Order Nonlinear Optical Activity and Catalytic CO2 Fixation

The present work focuses on the synthesis and properties of a novel multifunctional cerium(III) MOF, [Ce2(data)3(DMF)4]·DMF (data2-: 2,5-diaminoterephthalate), abbreviated as NH2-Ce-MUM-2. Its crystal structure reveals an intricate 3D 4,5-connected framework with a xah topology. This MOF features unique properties, such as open metal sites, presence of free amino groups, and high stability. Two main applications of NH2-Ce-MUM-2 were investigated: (i) as a heterogeneous catalyst in the CO2 fixation into cyclic carbonates and (ii) as a material with third-order nonlinear optical activity. As a model reaction, the cycloaddition of CO2 to propylene oxide to give the corresponding cyclic carbonate was explored under mild conditions, at the atmospheric pressure of carbon dioxide and in the absence of cocatalyst and added solvent. Various reaction parameters were investigated toward optimization and exploration of substrate scope, revealing up to 99% product yields of cyclic carbonate products. Besides, the structure of NH2-Ce-MUM-2 is highly stable, permitting its recyclability and reusability in further catalytic experiments. The significant contributions of free amino groups and open metal sites within this catalyst were particularly considered when proposing a potential mechanism for the reaction. Z-Scan measurements were used to evaluate the nonlinear optical (NLO) properties of NH2-Ce-MUM-2 at various laser intensities. A high two-photon absorption (TPA) under greater incident intensities shows that NH2-Ce-MUM-2 might be applicable in optical switching devices. Besides, the self-focusing effects of NH2-Ce-MUM-2 under various incident intensities were highlighted by the nonlinear index of refraction (n2). By reporting the synthesis and characterization of a novel MOF, along with its highly promising catalytic and NLO behavior, the current study introduces an additional example of multifunctional material into a growing family of metal-organic frameworks.

Advantages of Bimetallic Organic Frameworks in the Adsorption, Catalysis and Detection for Water Contaminants

The binary metal organic framework (MOF) is composed of two heterometallic ions bonded to an organic ligand. Compared with monometallic MOFs, bimetallic MOFs have greatly improved in terms of structure, porosity, active site, adsorption, selectivity, and stability, which has attracted wide attention. At present, many effective strategies have been designed for the synthesis of bimetallic MOF-based nanomaterials with specific morphology, structure, and function. The results show that bimetallic MOF-based nanocomposites could achieve multiple synergistic effects, which will greatly improve their research in the fields of adsorption, catalysis, energy storage, sensing, and so on. In this review, the main preparation methods of bimetallic MOFs-based materials are summarized, with emphasis on their applications in adsorption, catalysis, and detection of target pollutants in water environments, and perspectives on the future development of bimetallic MOFs-based nanomaterials in the field of water are presented.

Chelating adsorption-engaged synthesis of ultrafine iridium nanoparticles anchored on N-doped carbon nanofibers toward highly efficient hydrogen evolution in both alkaline and acidic media

Developing highly efficient and stable precious metal electrocatalysts toward hydrogen evolution reaction (HER) is crucial for energy application, while it is still challenging to achieve highly dispersed ultrafine metal nanoparticles on some promising supports to synergistically promote their electrocatalytic performance. Herein, we propose a feasible chelating adsorption-engaged strategy by introducing de-doped polyaniline with abundant amino groups to immobilize ultrafine iridium (Ir) nanoparticles on their derived N-doped carbon nanofibers (Ir-NCNFs). Experimental results demonstrate that the synthesized Ir-NCNFs can effectively promote the charge transfer and expose more electrochemical active sites, which eventually accelerate the reaction kinetics. Thus, the synthesized Ir-NCNFs catalyst exhibits admirable HER activities in both alkaline and acidic conditions with overpotentials of only 23 and 8 mV, which are even superior or close to the benchmark Pt/C catalyst. Furthermore, the synthesized Ir-NCNFs catalyst also exhibits a long-term durability. This study affords a reliable means to construct high-performance supported ultrafine metal nanocatalysts for electrocatalytic applications to alleviate the growing demand for energy conversion.

Recent Advances in Carbon-Based Electrodes for Energy Storage and Conversion

Carbon-based nanomaterials, including graphene, fullerenes, and carbon nanotubes, are attracting significant attention as promising materials for next-generation energy storage and conversion applications. They possess unique physicochemical properties, such as structural stability and flexibility, high porosity, and tunable physicochemical features, which render them well suited in these hot research fields. Technological advances at atomic and electronic levels are crucial for developing more efficient and durable devices. This comprehensive review provides a state-of-the-art overview of these advanced carbon-based nanomaterials for various energy storage and conversion applications, focusing on supercapacitors, lithium as well as sodium-ion batteries, and hydrogen evolution reactions. Particular emphasis is placed on the strategies employed to enhance performance through nonmetallic elemental doping of N, B, S, and P in either individual doping or codoping, as well as structural modifications such as the creation of defect sites, edge functionalization, and inter-layer distance manipulation, aiming to provide the general guidelines for designing these devices by the above approaches to achieve optimal performance. Furthermore, this review delves into the challenges and future prospects for the advancement of carbon-based electrodes in energy storage and conversion.

A review of recent developments of metal-organic frameworks as combined biomedical platforms over the past decade

Metal-organic frameworks (MOFs), also called porous coordination polymers, represent a class of crystalline porous materials made up of organic ligands and metal ions/metal clusters. Herein, an overview of the preparation of different metal-organic frameworks and the recent advances in MOF-based stimuli-responsive drug delivery systems (DDSs) with the drug release mechanisms including pH-, temperature-, ion-, magnetic-, pressure-, adenosine-triphosphate (ATP)-, H₂S-, redox-, responsive, and photoresponsive MOF were rarely introduced. The combination therapy containing of two or more treatments can be enhanced treatment effectiveness through overcoming limitations of monotherapy. Photothermal therapy (PTT) combined with chemotherapy (CT), chemotherapy in combination with PTT or other combinations were explained to overcome drug resistance and side effects in normal cells as well as enhancing the therapeutic response. Integrated platforms containing of photothermal/drug-delivering functions with magnetic resonance imaging (MRI) properties exhibited great advantages in cancer therapy.

Efficient Eu3+-Integrated UiO-66 Probe for Ratiometric Fluorescence Sensing of Styrene and Cyclohexanone

The development of probes with sensitive and prompt detection of volatile organic compounds (VOCs) is of great importance for protecting human health and public security. Herein, we successfully prepared a series of bimetallic lanthanide metal-organic framework (Eu/Zr-UiO-66) by incorporating Eu³⁺ for fluorescence sensing of VOCs (especially styrene and cyclohexanone) using a one-pot method. Based on the multiple fluorescence signal responses of Eu/Zr-UiO-66 toward styrene and cyclohexanone, a ratiometric fluorescence probe using (I₆₁₇/I₃₂₀) and (I₆₁₇/I₃₃₀) as output signals was developed to recognize styrene and cyclohexanone, respectively. Benefitting from the multiple fluorescence response, the limits of detection (LODs) of Eu/Zr-UiO-66 (1:9) for styrene and cyclohexanone were 1.5 and 2.5 ppm, respectively. These are among the lowest reported levels for MOF-based sensors, and this is the first known material for fluorescence sensing of cyclohexanone. Fluorescence quenching by styrene was mainly owing to the large electronegativity of styrene and fluorescence resonance energy transfer (FRET). However, FRET was accounted for fluorescence quenching by cyclohexanone. Moreover, Eu/Zr-UiO-66 (1:9) exhibited good anti-interference ability and recycling performance for styrene and cyclohexanone. More importantly, the visual recognition of styrene and EB vapor can be directly realized with the naked eyes using Eu/Zr-UiO-66 (1:9) test strips. This strategy provides a sensitive, selective, and reliable method for the visual sensing of styrene and cyclohexanone.

Metal-Organic Frameworks as Electrocatalysts

Transition metal complexes are well-known homogeneous electrocatalysts. In this regard, metal-organic frameworks (MOFs) can be considered as an ensemble of transition metal complexes ordered in a periodic arrangement. In addition, MOFs have several additional positive structural features that make them suitable for electrocatalysis, including large surface area, high porosity, and high content of accessible transition metal with exchangeable coordination positions. The present review describes the current state in the use of MOFs as electrocatalysts, both as host of electroactive guests and their direct electrocatalytic activity, particularly in the case of bimetallic MOFs. The field of MOF-derived materials is purposely not covered, focusing on the direct use of MOFs or its composites as electrocatalysts. Special attention has been paid to present strategies to overcome their poor electrical conductivity and limited stability.

Nanostructure Engineering of Sn-Based Catalysts for Efficient Electrochemical CO2 Reduction

Excessive anthropogenic CO₂ emission has caused a series of ecological and environmental issues, which threatens mankind's sustainable development. Mimicking the natural photosynthesis process (i.e., artificial photosynthesis) by electrochemically converting CO₂ into value-added products is a promising way to alleviate CO₂ emission and relieve the dependence on fossil fuels. Recently, Sn-based catalysts have attracted increasing research attentions due to the merits of low price, abundance, non-toxicity, and environmental benignancy. In this review, the paradigm of nanostructure engineering for efficient electrochemical CO₂ reduction (ECO₂ R) on Sn-based catalysts is systematically summarized. First, the nanostructure engineering of size, composition, atomic structure, morphology, defect, surficial modification, catalyst/substrate interface, and single-atom structure, are systematically discussed. The influence of nanostructure engineering on the electronic structure and adsorption property of intermediates, as well as the performance of Sn-based catalysts for ECO₂ R are highlighted. Second, the potential chemical state changes and the role of surface hydroxides on Sn-based catalysts during ECO₂ R are introduced. Third, the challenges and opportunities of Sn-based catalysts for ECO₂ R are proposed. It is expected that this review inspires the further development of highly efficient Sn-based catalysts, meanwhile offer protocols for the investigation of Sn-based catalysts.

Pillared-MOF@NiV-LDH Composite as a Remarkable Electrocatalyst for Water Oxidation

Oxygen evolution reaction (OER) represents a highly important electrochemical transformation in energy storage and conversion technologies. Considering the low rate of this four-electron half-reaction, there is a demand for efficient, stable, and noble-metal-free electrocatalysts to improve the kinetic and economical parameters. In this work, a new pillared-MOF@NiV-LDH nanocomposite based on a Co^II metal-organic framework (pillared-MOF) and heterometallic Ni/V-layered double hydroxide (NiV-LDH) was assembled via a simple protocol, characterized, and explored as an electrocatalyst in OER. A remarkable electrocatalytic efficiency of pillared-MOF@NiV-LDH in 1 M KOH is evidenced by a low overpotential (238 mV at 10 mA cm^-2 current density) and a small value of the Tafel slope (62 mV dec^-1). These parameters are very close to those of the reference IrO₂ electrocatalyst and are superior to the majority of the LDH- and MOF-based systems previously applied for OER. Excellent stability of pillared-MOF@NiV-LDH was confirmed by the chronopotentiometry tests for 70 h and linear-sweep voltammetry after 7000 cycles. Features such as rich electroactive sites, porous structure, high surface area, and synergic effect between pillared-MOF and NiV-LDH are likely responsible for the remarkable electrocatalytic efficiency of this electrocatalyst in OER. Despite prior reports on the application of NiV-LDH in OER, the present study describes the first example where this type of LDH is blended with MOF to generate a nanocomposite material. The interface between the two components of the composite can improve the electronic structure and, in turn, the electrocatalytic behavior. The introduction of this composite paves the way toward the synthesis of other multicomponent materials with potential applications in different energy fields.

Postsynthetic Modification of NU-1000 for Designing a Polyoxometalate-Containing Nanocomposite with Enhanced Third-Order Nonlinear Optical Performance

For the advancement of laser technologies and optical engineering, various types of new inorganic and organic materials are emerging. Metal-organic frameworks (MOFs) reveal a promising use in nonlinear optics, given the presence of organic linkers, metal cluster nodes, and possible delocalization of π-electron systems. These properties can be further enhanced by the inclusion of solely inorganic materials such as polyoxometalates as prospective low-cost electron-acceptor species. In this study, a novel hybrid nanocomposite, namely, SiW₁₂@NU-1000 composed of SiW₁₂ (H₄SiW₁₂O₄₀) and Zr-based MOF (NU-1000), was assembled, completely characterized, and thoroughly investigated in terms of its nonlinear optical (NLO) performance. The third-order NLO behavior of the developed system was assessed by Z-scan measurements using a 532 nm laser. The effect of two-photon absorption and self-focusing was significant in both NU-1000 and SiW₁₂@NU-1000. Experimental studies suggested a much superior NLO performance of SiW₁₂@NU-1000 if compared to that of NU-1000, which can be assigned to the charge-energy transfer between SiW₁₂ and NU-1000. Negligible light scattering, good stability, and facile postsynthetic fabrication method can promote the applicability of the SiW₁₂@NU-1000 nanocomposite for various optoelectronic purposes. This research may thus open new horizons to improve and enhance the NLO performance of MOF-based materials through π-electron delocalization and compositing metal-organic networks with inorganic molecules as electron acceptors, paving the way for the generation of novel types of hybrid materials for prospective NLO applications.

Coordination Polymers Constructed from an Adaptable Pyridine-Dicarboxylic Acid Linker: Assembly, Diversity of Structures, and Catalysis

4,4'-(Pyridine-3,5-diyl)dibenzoic acid (H2pdba) was explored as an adaptable linker for assembling a diversity of new manganese(II), cobalt(II/III), nickel(II), and copper(II) coordination polymers (CPs): [Mn(μ4-pdba)(H2O)]n (1), {[M(μ3-pdba)(phen)]·2H2O}n (M = Co (2), Ni (3)), {[Cu2(μ3-pdba)2(bipy)]·2H2O}n (4), {[Co(μ3-pdba)(bipy)]·2H2O}n (5), [Co2(μ3-pdba)(μ-Hbiim)2(Hbiim)]n (6), and [M(μ4-pdba)(py)]n (M = Co (7), Ni (8)). The CPs were hydrothermally synthesized using metal(II) chloride precursors, H2pdba, and different coligands functioning as crystallization mediators (phen: 1,10-phenanthroline; bipy: 2,2'-bipyridine, H2biim: 2,2'-biimidazole; py: pyridine). Structural networks of 1-8 range from two-dimensional (2D) metal-organic layers (1-3, 5-8) to three-dimensional (3D) metal-organic framework (MOF) (4) and disclose several types of topologies: sql (in 1), hcb (in 2, 3, 5), tfk (in 4), 3,5L66 (in 6), and SP 2-periodic net (6,3)Ia (in 7, 8). Apart from the characterization by standard methods, catalytic potential of the obtained CPs was also screened in the Knoevenagel condensation of benzaldehyde with propanedinitrile to give 2-benzylidenemalononitrile (model reaction). Several reaction parameters were optimized, and the substrate scope was explored, revealing the best catalytic performance for a 3D MOF 4. This catalyst is recyclable and can lead to substituted dinitrile products in up to 99% product yields. The present study widens the use of H2pdba as a still poorly studied linker toward designing novel functional coordination polymers.

Advances in Titanium Carbide (Ti3C2T x ) MXenes and Their Metal-Organic Framework (MOF)-Based Nanotextures for Solar Energy Applications: A Review

Introducing new materials with low cost and superior solar harvesting efficiency requires urgent attention to solve energy and environmental challenges. Titanium carbide (Ti3C2T x ) MXene, a 2D layered material, is a promising solution to solve the issues of existing materials due to their promising conductivity with low cost to function as a cocatalyst/support. On the other hand, metal-organic frameworks (MOFs) are emerging materials due to their high surface area and semiconducting characteristics. Therefore, coupling them would be promising to form composites with higher solar harvesting efficiency. Thus, the main objective of this work to disclose recent development in Ti3C2T x -based MOF nanocomposites for energy conversion applications to produce renewable fuels. MOFs can generate photoinduced electron/hole pairs, followed by transfer of electrons to MXenes through Schottky junctions for photoredox reactions. Currently, the principles, fundamentals, and mechanism of photocatalytic systems with construction of Schottky junctions are critically discussed. Then the basics of MOFs are discussed thoroughly in terms of their physical properties, morphologies, optical properties, and derivatives. The synthesis of Ti3C2T x MXenes and their composites with the formation of surface functionals is systematically illustrated. Next, critical discussions are conducted on design considerations and strategies to engineer the morphology of Ti3C2T x MXenes and MOFs. The interfacial/heterojunction modification strategies of Ti3C2T x MXenes and MOFs are then deeply discussed to understand the roles of both materials. Following that, the applications of MXene-mediated MOF nanotextures in view of CO2 reduction and water splitting for solar fuel production are critically analyzed. Finally, the challenges and a perspective toward the future research of MXene-based MOF composites are disclosed.

Metal-Organic Framework with Near-Infrared Luminescence for "Switch-on" Determination of Kaempferol and Quercetin by the Antenna Effect

The establishment of a reliable and sensitive method for the detection of flavonoids, such as kaempferol (Kae) and quercetin (Que), is important and challenging in food chemistry and pharmacology because numerous structural analogues may interfere with the detection. Until now, designing an efficient switch-on fluorescence sensing strategy for Kae and Que was still in the unachievable stage. In this work, a switch-on near-infrared (NIR) luminescence sensing assay for Kae and Que was fabricated based on a metal-organic framework (MOF) called IQBA-Yb for the first time. The fluorescence enhancing mechanism was that analytes served as additional "antenna" of Yb³⁺, leading to the efficient switch-on NIR emission under excitation at 467 nm. Meanwhile, the combination results of experiment and theoretical calculation revealed that there existed hydrogen bonds between Kae, Que, and the MOF skeleton, further promoting the energy transfer between the analyte and Yb³⁺ and facilitating fluorescence enhancement response. The developed probe possessed excellent sensing capability for Kae and Que, accompanied by a wide linear range (0.04-70, 0.06-90 μM), low detection limit (0.01, 0.06 μM), and short response time (20 min, 6 min), which was used to determine the Kae and Que contents in Green Lake and eatable Que samples with satisfactory results.

Biological Effects of EGCG@MOF Zn(BTC)4 System Improves Wound Healing in Diabetes

Tea contains high levels of the compound epigallocatechin gallate (EGCG). It is considered an important functional component in tea and has anti-cancer, antioxidant, and anti-inflammatory effects. The eight phenolic hydroxyl groups in EGCG’s chemical structure are the basis for EGCG’s multiple biological effects. At the same time, it also leads to poor chemical stability, rendering EGCG prone to oxidation and isomerization reactions that change its original structure and biological activity. Learning how to maintain the activity of EGCG has become an important goal in understanding the biological activity of EGCG and the research and development of tea-related products. Metal–organic frameworks (MOFs) are porous materials with a three-dimensional network structure that are composed of inorganic metals or metal clusters together with organic complexes. MOFs exploit the porous nature of the material itself. When a drug is an appropriate size, it can be wrapped into the pores by physical or chemical methods; this allows the drug to be released slowly, and MOFs can also reduce drug toxicity. In this study, we used MOF Zn(BTC)₄ materials to load EGCG and investigated the sustained release effect of EGCG@MOF Zn(BTC)₄ and the biological effects on wound healing in a diabetic mouse model.