Metal-organic Framework Composites Research Articles

Unlocking Advanced Architectures of Single‐Crystal Metal–Organic Frameworks

AbstractThe synthesis of metal–organic frameworks (MOFs) with diverse geometries has captivated considerable interest due to their manifestation of novel and extraordinary properties. While much progress has been made in shaping regular polyhedral single‐crystal MOFs, the creation of more complex, topologically intricate nanostructures remains a largely unexplored frontier. Here, we present a refined site‐specific anisotropic assembly and etching co‐mediation approach to fabricate a series of hierarchical MOF nanohybrids and single‐crystal MOFs. This approach yields ZIF‐8&mSiO2 nanohybrids with diverse topologies, alongside derived single‐crystal MOF nanoparticles exhibiting intricate morphologies such as hexapods, nested nanocages, and octopods. Our method involves the selective growth of six mSiO2 nanoplates on the {100} facets of ZIF‐8 nanocubes, forming the cubic‐shaped ZIF‐8&mSiO2 nanohybrids, with the concurrent etching of the {110} facets of initial ZIF‐8 nanocubes. By fine‐tuning this balance between the growth and etching, we achieved precise morphological control, transforming cubic nanohybrids into intricate hexapods nanohybrids. Additionally, secondary epitaxial growth of homo‐ or hetero‐MOFs on these hybrids led to ZIF‐8&mSiO2&MOF composites with six mSiO2 inlays. Finally, selective alkaline etching of the mSiO2 compartments result in single‐crystal MOF nanoparticles with unprecedented and sophisticated morphologies, such as hexapods, nested nanocages, octopods. This work advances the field of MOF nanostructure design, opening new avenues for the development of sophisticated, multifunctional materials.

A decade of breakthroughs: MOF-graphene oxide catalysts for water splitting efficiency

Abstract Burning fossil fuels has significantly worsened environmental pollution, particularly due to the release of carbon dioxide emissions. The global efforts to promote renewable energy solutions, like electrocatalytic water splitting, have gained momentum. Scientists are focusing on the development of sustainable methods like water splitting to reduce dependence on conventional fuels. Developing affordable and effective electrocatalysts is crucial for multifunctional electrochemical water splitting (ECWS). In comparison to traditional electrocatalysts, metal-organic frameworks (MOFs) exhibit favorable catalytic performance for electrochemical water decomposition because of their plentiful porosity, surface area, and topologies for enhanced production of hydrogen (H2) and oxygen (O2) gas. When combined with MOF, graphene creates a synergistic hybrid nanomaterial that is more stable, adaptable, and durable. The primary goal of this review article is to conduct an in-depth investigation of the latest advancements in MOFs and MOF-GO electrocatalysts for water electrolysis. Herein, we have covered the plausible mechanism for the overall water-splitting electrocatalytic processes and several important factors influencing their electrocatalytic response. We also discussed the recent progress in the performance and stability of MOFs and MOF-GO electrocatalysts for water-splitting reactions. Finally, the article highlights the challenges and application of MOF and MOF-GO composites and the future preference for water-splitting applications.

MOF biochar composites for environmental protection and pollution control.

Research studies on Metal Organic Frameworks (MOF) based composites and their potential applications in environmental engineering and pollution control have recently emerged. An attractive material to form MOF composites is biochar (BC); a low-cost, highly porous carbonaceous by-product of biomass pyrolysis. This paper presents a critical review on MOF-biochar composites, focusing on fabrication, characterisation, modification, and applications in environmental protection and pollution control. The adsorption mechanisms and influential parameters are systematically examined to develop an insight into interactions between MOF and biochar in remedial process. The adsorption capacity of composites is generally doubled compared to the standalone biochar, while MOFs maintain their crystallinity, even over multiple regeneration cycles, indicating the composites' long-term applicability and sustainability. These findings highlight the potential of MOF-biochar composites for environmental applications and identify key areas for further research to enhance their sustainability in environmental protection and green energy.

Unlocking Advanced Architectures of Single-Crystal Metal-Organic Frameworks.

The synthesis of metal-organic frameworks (MOFs) with diverse geometries has captivated considerable interest due to their manifestation of novel and extraordinary properties. While much progress has been made in shaping regular polyhedral single-crystal MOFs, the creation of more complex, topologically intricate nanostructures remains a largely unexplored frontier. Here, we present a refined site-specific anisotropic assembly and etching co-mediation approach to fabricate a series of hierarchical MOF nanohybrids and single-crystal MOFs. This approach yields ZIF-8&mSiO2 nanohybrids with diverse topologies, alongside derived single-crystal MOF nanoparticles exhibiting intricate morphologies such as hexapods, nested nanocages, and octopods. Our method involves the selective growth of six mSiO2 nanoplates on the {100} facets of ZIF-8 nanocubes, forming the cubic-shaped ZIF-8&mSiO2 nanohybrids, with the concurrent etching of the {110} facets of initial ZIF-8 nanocubes. By fine-tuning this balance between the growth and etching, we achieved precise morphological control, transforming cubic nanohybrids into intricate hexapods nanohybrids. Additionally, secondary epitaxial growth of homo- or hetero-MOFs on these hybrids led to ZIF-8&mSiO2&MOF composites with six mSiO2 inlays. Finally, selective alkaline etching of the mSiO2 compartments result in single-crystal MOF nanoparticles with unprecedented and sophisticated morphologies, such as hexapods, nested nanocages, octopods.

Porosity Tunable Metal-Organic Framework (MOF)-Based Composites for Energy Storage Applications: Recent Progress.

To solve the energy crisis and environmental issues, it is essential to create effective and sustainable energy conversion and storage technologies. Traditional materials for energy conversion and storage however have several drawbacks, such as poor energy density and inadequate efficiency. The advantages of MOF-based materials, such as pristine MOFs, also known as porous coordination polymers, MOF composites, and their derivatives, over traditional materials, have been thoroughly investigated. These advantages stem from their high specific surface area, highly adjustable structure, and multifunctional nature. MOFs are promising porous materials for energy storage and conversion technologies, according to research on their many applications. Moreover, MOFs have served as sacrificial materials for the synthesis of different nanostructures for energy applications and as support substrates for metals, metal oxides, semiconductors, and complexes. One of the most intriguing characteristics of MOFs is their porosity, which permits space on the micro- and meso-scales, revealing and limiting their functions. The main goals of MOF research are to create high-porosity MOFs and develop more efficient activation techniques to preserve and access their pore space. This paper examines the porosity tunable mixed and hybrid MOF, pore architecture, physical and chemical properties of tunable MOF, pore conditions, market size of MOF, and the latest development of MOFs as precursors for the synthesis of different nanostructures and their potential uses.

Comparison of In Situ and Postsynthetic Formation of MOF-Carbon Composites as Electrocatalysts for the Alkaline Oxygen Evolution Reaction (OER).

Mixed-metal nickel-iron, NixFe materials draw attention as affordable earth-abundant electrocatalysts for the oxygen evolution reaction (OER). Here, nickel and mixed-metal nickel-iron metal-organic framework (MOF) composites with the carbon materials ketjenblack (KB) or carbon nanotubes (CNT) were synthesized in situ in a one-pot solvothermal reaction. As a direct comparison to these in situ synthesized composites, the neat MOFs were postsynthetically mixed by grinding with KB or CNT, to generate physical mixture composites. The in situ and postsynthetic MOF/carbon samples were comparatively tested as (pre-)catalysts for the OER, and most of them outperformed the RuO2 benchmark. Depending on the carbon material and metal ratio, the in situ or postsynthetic composites performed better, showing that the method to generate the composite can influence the OER activity. The best material Ni5Fe-CNT was synthesized in situ and achieved an overpotential (η) of 301 mV (RuO2η = 354 mV), a Tafel slope (b) of 58 mV/dec (RuO2b = 91 mV/dec), a charge transfer resistance (Rct) of 7 Ω (RuO2 Rct = 39 Ω), and a faradaic efficiency (FE) of 95% (RuO2 FE = 91%). Structural changes in the materials could be seen through a stability test in the alkaline electrolyte, and chronopotentiometry over 12 h showed that the derived electrocatalysts and RuO2 have good stability.

Advanced Alkali Metal Batteries Based on MOFs and Their Composites.

The integration of metal-organic frameworks (MOFs) with functional materials has established a versatile platform for a wide range of energy storage applications. Due to their large specific surface area, high porosity, and tunable structural properties, MOFs hold significant promise as components in energy storage systems, including electrodes, electrolytes, and separators for alkali metal-ion batteries (AIBs). Although lithium-ion batteries (LIBs) are widely used, their commercial graphite anode materials are nearing their theoretical capacity limits, and the scarcity of lithium and cobalt resources increases costs. Although zinc-ion batteries (ZIBs) suffer from limited cycling stability, they are attractive for their low cost, high capacity, and excellent safety. Meanwhile, potassium-ion (PIBs) and sodium-ion batteries (SIBs) show promise due to their affordability and abundant resources, but they encounter issues such as short cycle life and low energy density. This review outlines the applications of MOF composites in LIBs, SIBs, and ZIBs, introduces common synthesis methods, and forecasts future development directions and challenges in energy storage applications. We emphasize how the understanding can lay the foundation for developing MOF composites with enhanced functionalities.

Metal-organic framework catalysed multicomponent reactions towards the synthesis of Pyrans.

Metal-Organic Frameworks (MOFs) gaining increasing interest in heterogeneous catalysis owing to their advantageous properties such as superior porosity, high surface area, ample catalytic sites. Their properties can be tailored by varying the metal ions or metal clusters (nodes) and organic linkers. Magnetically active nano core-shell MOF composites are also discovered for easy separation and reuse of catalyst. MOF catalysed multicomponent reactions (MCRs) satisfy several green chemistry principles and thus can be considered as a sturdy step towards sustainable chemical synthesis. In this article, synthesis of biologically potent pyran scaffolds through MOF catalysed MCR approaches have been reviewed. Preparation of MOF catalyst, its catalytic performance in pyran synthesis, reusability has been discussed with reaction for each example.

Boosting peroxymonosulfate activation for complete removal of gatifloxacin by a bead-chain zeolitic imidazolate framework composite.

A bead-chain metal-organic framework composite was designed and synthesized by assembling a zeolitic imidazolate framework (ZIF) onto manganese dioxide (MnO2) nanowires. The prepared catalyst MnO2@ZIF-X (X = 1, 2 and 3) was used to facilitate gatifloxacin (GAT) degradation by using potassium peroxymonopulfate (PMS) as an activator. MnO2@ZIF-2 exhibited excellent catalytic performance, achieving 100% degradation of GAT (10mg/L) in the presence of PMS (1mM) in 15min, and the toxicity of the majority of degradation intermediates decreased. Furthermore, the removal efficiency was maintained above 90% throughout a wide pH range (3-11) and in the coexistence of anions ( [Formula: see text] , Cl-, SO42-). The main mechanism of the MnO2@ZIF-2/PMS system involves the synergistic effect of radicals and non-radicals (single linear oxygen and electron-mediated transfer), making the system highly resistant to interference from environmental matrices. Moreover, the GAT degradation pathway was elucidated through intermediate analysis and theoretical calculations. In particular, MnO2@ZIF-2 was well dispersed on a microporous filter membrane to create an immobilized membrane reactor that displayed excellent catalytic performance for the continuous degradation of GAT for 300min. This work offers an avenue for the design of catalysts with good catalytic activity, particularly for PMS activation in antibiotic wastewater remediation.

Cerium Metal-Organic Framework Composites for Supercapacitor Energy Storage

Supercapacitors have emerged as efficient energy storage devices, offering high power density, long cycle life, and rapid charge-discharge capabilities. Advanced materials such as carbon nanotubes (CNTs) and graphene oxide (GO) stand out due to their exceptional electrochemical properties, including open structures and chirality, with capacities ranging from 300 to 1300 mAh g-1. However, the search for cost-effective and highly conductive materials continues to challenge researchers. Metal-Organic Frameworks (MOFs) have surfaced as strong candidates due to their vast surface area, inherent conductivity, and affordability. Nonetheless, the relatively low conductivity of pristine MOFs necessitates composite integration for optimal performance. This review focuses on cerium-based MOF (Ce-MOF) composites, analyzing their structural and electrochemical properties. Key aspects, including synthesis methods, structural characterization, and electrochemical evaluation through cyclic voltammetry and galvanostatic charge-discharge techniques, are discussed in detail. The integration of functional composites into MOFs enhances cycling stability and minimizes capacitance loss over extended use. This review aims to inspire further research into Ce-MOF composites, underscoring their potential as high-performance materials for supercapacitor applications.

Non-Aqueous Electrochemical CO2 Reduction to Multivariate C2-Products Over Single Atom Catalyst at Current Density up to 100mAcm-2.

Electrochemical CO2 reduction reaction (CO2-RR) in non-aqueous electrolytes offers significant advantages over aqueous systems, as it boosts CO2 solubility and limits the formation of HCO3 - and CO3 2- anions. Metal-organic frameworks (MOFs) in non-aqueous CO2-RR makes an attractive system for CO2 capture and conversion. However, the predominantly organic composition of MOFs limits their electrical conductivity and stability in electrocatalysis, where they suffer from electrolytic decomposition. In this work, electrically conductive and stable Zirconium (Zr)-based porphyrin MOF, specifically PCN-222, metalated with a single-atom Cu has been explored, which serves as an efficient single-atom catalyst (SAC) for CO2-RR. PCN- 222(Cu) demonstrates a substantial enhancement in redox activity due to the synergistic effect of the Zr matrix and the single-atom Cu site, facilitating complete reduction of C2 species under non-aqueous electrolytic conditions. The current densities achieved (≈100mAcm- 2) are 4-5 times higher than previously reported values for MOFs, with a faradaic efficiency of up to 40% for acetate production, along with other multivariate C2 products, which have never been achieved previously in non-aqueous systems. Characterization using X-ray and various spectroscopic techniques, reveals critical insights into the role of the Zr matrix and Cu sites in CO2 reduction, benchmarking PCN-222(Cu) for MOF-based SAC electrocatalysis.

Palladium Nanoparticle-Decorated Copper-Hemin Metal Organic Framework for Enzymatic Electrochemical Detection of Creatinine in Human Urine.

Creatinine is indeed a crucial biomarker for kidney diseases. In this work, a novel electrochemical biosensor based on a copper-hemin metal organic framework [Cu-hemin metal-organic framework (MOF)] nanoflake decorated with palladium (Pd) (Pd/Cu-hemin MOF) was fabricated and incorporated with creatinine deiminase (CD) on a glassy carbon electrode (GCE) for creatinine detection. The formation of a Pd/Cu-hemin MOF composite was confirmed by X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The formation of the composite as nanoflakes is evident from the scanning electron microscopy image. The transmission electron microscopy image clarifies the decoration of palladium nanoparticles on Cu-hemin MOF surfaces. Thus, the proposed biosensor (Pd/Cu-hemin MOF/CD/GCE) electrochemical performances were studied with cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. As a result, the Pd/Cu-hemin MOF/CD/GCE-based electrochemical detection of creatinine exhibits a broad linear range from 0 to 130 μM (R2 = 0.99), a low limit of detection 0.08 μM, and an excellent sensitivity of 3.2 μA μM-1 cm-2. The biosensor also determines creatinine in samples of human urine with a good recovery from 99.4 to 100.8%. Thus, in this study, an electrochemical biosensing platform based on Pd/Cu-hemin MOF/CD/GCE has been designed practically for creatinine.

Synthesis of reusable hierarchical Pore PVDF-MIL-101(Cr) foam for Solid phase extraction of fluoroquinolones from water and its adsorption behavior for anionic and cationic dyes

In this study, a novel hierarchical pore MIL-101(Cr) foam (HPF-MIL-101) was designed and prepared using the sacrificial template method with NaCl as the sacrificial template. This method involved grinding, heating, and washing the NaCl template to produce HPF-MIL-101, with PVDF as the binder and MIL-101(Cr) as the adsorbent. This preparation process is both straightforward and cost-effective, avoiding the use or generation of any organic reagents, thereby offering an environmentally sustainable approach for producing metal-organic framework (MOF) composites. The prepared HPF-MIL-101 exhibited excellent adsorption capabilities for both anionic dye (methyl orange, MO) and cationic dye (methylene blue, MB). The adsorption process followed a pseudo-second-order kinetic model and Friedrich isotherm model, indicating a multilayer adsorption. This is further supported by the Weber-Morris intraparticle diffusion model, which divided the adsorption process into three stages. Furthermore, the adsorption process was consistent with the Freundlich isotherm model, with a correlation coefficient (r) greater than 0.96. HPF-MIL-101 can also be used as an adsorbent for solid phase extraction (SPE). Therefore, an SPE method combined with high-performance liquid chromatography (HPLC) was developed using HPF-MIL-101 as the adsorbent to analyze five fluoroquinolones (FQs) in water samples. This analytical method showed good linearity in the range of 30–2000 ng·mL−1, with excellent linear correlation coefficient (r = 0.9991–0.9999), reasonable extraction recoveries ranging from 80.39 to 112.7 % (RSD ≤ 7.9 %), and low limits of detection (8–30 ng·mL−1). Overall, the results indicated that HPF-MIL-101 not only had a simple, environment-friendly, and pollution-free preparation process but also can be reused for enrichment and detection of trace FQs in water. Thus, HPF-MIL-101 exhibits immense application potential in environmental pollutant removal and also provides a valuable reference for the preparation and application of other MOF composites.

Electrochemical immunosensor for the predictive cancer biomarker SLFN11 using reduced graphene oxide/MIL-101(Cr)-NH2 composite

SLFN11 is a predictive cancer biomarker essential for identifying tumors that are sensitive to DNA-damaging agents, facilitating more personalized and effective treatment approaches. Detecting this biomarker can guide therapeutic decisions and improve outcomes for cancer patients. However, existing detection methods for SLFN11 are complex and require advanced techniques. In this study, we introduce the first immunosensor designed for on-site detection of SLFN11. An advanced electrochemical immunosensor platform utilizing a composite of graphene oxide (GO) and chromium-based metal organic framework (MIL-101 (Cr)-NH2) was developed. The integration of GO and MIL-101(Cr)-NH2 was characterized through FT-IR, XRD, SEM, and XPS, affirming the formation of the composite. The subsequent electrochemical reduction to rGO/MIL-101(Cr)-NH2 significantly improved the electrochemical performance and stability. A glutaraldehyde cross-linker was then utilized to attach the SLFN11-specific antibody to the amine groups of the MOF-modified electrodes. This led to the development of rapid, sensitive, portable, and cost-effective immunosensor for SLFN11 at concentrations as low as 8.9 pg/mL which holds promise for early cancer diagnosis. High specificity was achieved, with minimal cross-reactivity observed with other cancer biomarkers such as pepsinogen I, claudin 18.2 and Programmed cell death protein 1. Demonstrating practical applicability, the electrochemical immunosensor validated by commercial ELISA kit showed successful detection in serum samples with high recovery rates and reproducibility. This research highlights the potential of rGO/MOFs composites in electrochemical biosensors developments for early cancer diagnostics and personalized medicine.

Elucidating the synergistic effect of oxygen vacancies and Z-scheme heterojunction in NU-1000/BiOCl-Ov composites towards enhanced photocatalytic degradation of tetracycline hydrochloride.

Although Z-scheme heterojunction composites have been widely studied in photocatalysis, in-depth investigation of oxygen vacancies (Ov) in the Z-scheme photocatalysts is still rare. Herein, an oxygen vacancies modified NU-1000/BiOCl-Ov composite with Z-scheme heterojunction was rationally designed and fabricated. The combination of X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) experiment verified the presence of oxygen vacancies, meanwhile the Z-scheme charge transfer across the heterojunction interface was confirmed in detail by the in situ-XPS, Kelvin probe force microscope (KPFM) studies, ultraviolet photoelectron spectroscopy (UPS), EPR radical capture experiment, as well as density functional theory (DFT) calculation. Importantly, compared to pristine NU-1000 and BiOCl, the optimized NU-1000/BiOCl-Ov composite displayed enhanced photocatalytic performance in the degradation of tetracycline hydrochloride (TCH) under visible light (λ≥400nm). Theoretical calculations reveal that the oxygen vacancies could induce electron redistribution, facilitating the activation of O2 and TCH molecules, thereby promoting the photodegradation efficiency. Moreover, mechanism studies suggested that the synergistic effect of oxygen vacancies and Z-scheme heterojunction could facilitate the effective separation of photogenerated carriers. At last, the degradation routes of TCH were proposed and the toxicity of degradation intermediates was assessed. This work underlines the cooperative functions of oxygen vacancies and Z-scheme heterojunction towards improved photocatalytic performance, which offers new perspectives on the design of metal-organic frameworks (MOFs) composites for efficient photocatalysis.

Metal-organic framework-based materials for solar-driven interfacial evaporation

As a sustainable and green approach, solar-driven interfacial water evaporation (SIE) can recover clean water from diverse water resources such as seawater and wastewater by converting solar energy into heat energy, paving the way to addressing the increasingly severe water shortage. In recent years, metal–organic frameworks (MOFs) have been applied for constructing the evaporator for SIE, considering their merits such as large specific surface area, tunable component and structure, and high porosity. More importantly, MOFs materials have expanded their application in the synthesis of porous carbon, metal oxides/sulfides/carbides, and MOFs composites, which not only may preserve the merits of MOFs but also possess other functions. In this review, the latest developments regarding the solar evaporators designed by MOFs-based materials (including MOFs, MOFs-derivatives, and MOFs composites) is summarized and systematically discussed. The roles of MOFs-based materials in evaporation systems and the emerging applications of the evaporation systems are also highlighted. Ultimately, the challenges and perspectives of the MOFs-based materials used for designing of SIE systems are also presented.

Phonon confinement in TiO2 sandwiched MOF particles for high temperature dielectric energy storage

For promising energy storage applications, high surface area materials containing both ionic and organic components are ideal candidates. While Metal Organic Frameworks (MOFs) exhibit the desired characteristic, they generally lack high-temperature structural stability observed in conventional inorganic metal-based compounds. Here we propose a novel composite material comprising TiO2- incorporated and encapsulated carbonized ZIF-67 (TZT), showing stable dielectric and energy storage performance at elevated temperatures than other MOF composites. By integrating TiO2 within the ZIF-67 framework, the composite achieves significant phonon confinement for enhanced dielectric polarization, with permittivity achieving a value of 50, while the external coating gives the imidazole structure temperature sustainability. The current density shows a prominent increase with the increase of temperature and frequency and hence lowering of activation energy and Schottky barrier potential, that results in a prominent rise of polarization with respect to electric filed. The study elucidates the underlying mechanisms of phonon-modulated polarization dynamics, demonstrating dual Debye relaxations at low temperatures and Maxwell-Wagner relaxations at high temperatures. These findings highlight the crucial role of phonon dynamics in enhancing the energy storage capabilities and dielectric performance of the composite material, making TZT a superior candidate for advanced high-temperature energy storage devices.

Preparation and Electrocatalytic Properties of One-Dimensional Nanorod-Shaped N, S Co-Doped Bimetallic Catalysts of FeCuS-N-C

Metal air batteries have gradually attracted public attention due to their advantages such as high power density, high energy density, high energy conversion efficiency, and clean and green products. Reasonable design of oxygen reduction reaction (ORR) catalysts with high cost-effectiveness, high activity, and high stability is of great significance. Metal organic frameworks (MOFs) have the advantages of large specific surface area, high porosity, and designability, which make them widely used in many fields, especially in catalysis. This paper starts with regulating and optimizing the composition and structure of MOFs. A series of N, S co-doped electrocatalysts FeCuS-N-C were prepared by two high-temperature pyrolysis processes using N-doped carbon hollow nanorods derived from ZIF-8 as the substrate. The one-dimensional nanorod material derived from this MOF exhibits excellent electrocatalytic ORR performance (Eonset = 0.998 V, E1/2 = 0.874 V). When used as the air cathode catalyst for zinc air batteries and assembled into liquid ZABs, the battery discharge curve was calculated and found to have a maximum power density of 142.7 mW cm−2, a specific capacity of 817.1 mAh gZn−1, and a cycling stability test of over 400 h. This study provides an innovative approach for designing and optimizing non-precious metal catalysts for zinc air batteries.

Expanding the Scope of ZIF-Derived Carbons Towards Tailored Architectures and Compositions

Proton exchange membrane fuel cells (PEMFCs) represent a promising technology for clean energy conversion. The key chemical transformation within a fuel cell is conducted by catalyst nanoparticles tethered to a carbon support. Although the carbon support plays a critical role in maximizing the performance and durability of the catalyst nanoparticles and mass transport, predictably tuning the chemical environment and pore architecture of the carbon support remains a challenge. Metal–organic frameworks are a class of crystalline porous coordination polymers known for their structural and chemical tunability. Recently, metal–organic frameworks (MOFs), almost exclusively zeolitic imidazolate framework-8 (ZIF-8), have been used as precursors to generate carbon supports where the MOF architecture serves as a template to generate the carbon skeleton. As a result, these materials have an improved homogeneous porous landscape and, encouragingly, superior PEMFCs performance and durability. Herein, we leverage the vast library of MOFs and report design principles for generating precisely tuned carbon support architectures through systematic changes to the structure and chemical composition of MOFs. Advanced fuel cell testing of PEMFCs featuring these novel carbon architectures offers fine level insight into the effects of pore size, connectivity and chemistry on the performance of PEMFCs.Acknowledgement: This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.

Strategic design of cobalt-based bimetallic compounds using NH4BF4 as a structure-directing agent for enhancing energy storage ability of battery supercapacitor hybrids

Modifying morphology and composition of metal-organic frameworks (MOFs) can enhance their electrical conductivities and redox states. Structure-directing agents (SDAs) play a key role in shaping surface properties of materials. Ammonium fluoride-based complexes are useful in designing MOF derivatives with excellent energy storage capabilities. Metal species involved also affect redox reactions, which are crucial for energy storage in battery-type electrodes. In this study, cobalt-based bimetallic compounds derived from ZIF-67 are synthesized using 2-methylimidazole and the SDA of NH4BF4. The secondary metal species contain Cu, Al, Zn and Mn, and resulting compositions include hydroxides and hydroxide nitrates. With the optimal 2-methylimidazole to NH4BF4 ratio, the best-performed cobalt-based compound is related to Ni (MB21-CoNi) which demonstrates the highest specific capacitance (CF) of 763.2 F/g at 20 mV/s, attributed to high theoretical capacities and sheets-assembled flower-like structures. A battery-supercapacitor hybrid (BSH) composed of carbon and MB21-CoNi electrodes achieves a maximum energy density of 17.2 Wh/kg at 650 W/kg. A CF retention of 94.9% and a Coulombic efficiency of 88.9% after 10,000 cycles are attained for this BSH. This work provides a blueprint for designing novel active materials with helps of 2-methylimidazole and NH4BF4, and for discussing significant parameters to achieve excellent energy storage ability.