Polysulfide anchoring and charge transport in MOF materials need to be optimized for further performance enhancement. Well-designed pore geometries are critical as cage-like pores are typically better for physical encapsulation of sulfur species than straight channels.
MOFs with more Lewis acidic sites and N containing linkers show higher affinity for polysulfides.
Increasing the conductivity ionic and electronic of MOF hosts is another approach to achieve high-rate and high-capacity batteries. When utilized as separators, MOFs demonstrate advanced performance with fine-tuned crystallite morphology, well dispersed catalytically active sites and appropriate pore geometries. Lithium-oxygen Li-O 2 batteries, also referred to as lithium-air batteries, are typically made up of lithium metal anodes and porous carbon or composite cathodes where the ORR reaction occurs Fig. The efficiency and cyclability of Li-O 2 batteries are predominantly limited by the redox events at the cathode.
Owing to the reactivity of O 2 and its reduced species, a number of side reactions can take place that limit cell lifetime and capacity retention. In addition, the reduction products Li 2 O 2 and Li 2 O are poorly soluble in organic electrolytes, passivating the cathode surface and making recovery of these species difficult upon charging. MOFs have been well studied in heterogeneous catalysis for many different reactions including ORR and OER 76 , 77 , 78 , and their catalytic utility in Li-O 2 cathodes is just now being realized.
Overall, the results suggest proper metal selection for catalysis is crucial for designing cells with high capacity. The authors also suggested the channel-like pores of MOF contribute to increased accessibility of O 2 by the metal sites. In addition, it was found that smaller Co-MOF particles greatly enhanced cell capacity due to shorter and more efficient O 2 diffusion pathways and a higher density of exposed active sites The synthetic tunability of MOFs is opportune for multifunctional catalytic systems. Homogeneous dispersion of the Mn and Co cations was found to be important for accessibility of catalytic sites by oxygen species.
The authors explain that the Mn sites assist in the reduction of oxygen species while discharging, while the Co sites are able to efficiently reverse this process upon charging evidenced by reduced overpotentials Fig. Together, the two metals enhance both efficiency and reversibility of discharge and charge processes, suggesting that multi-metallic MOFs with targeted catalytic activity are promising candidates for Li-O 2 cathodes.
However, these molecules react with the lithium anode and diminish the deliverable capacity and cyclability. To resolve this issue, a film of HKUST-1 was grown on a Celgard separator to prevent the mediator from diffusing to the Li anode, allowing the battery to maintain cell function for over cycles Design criteria and opportunities : Overall, Li-O 2 batteries show promise for providing high-capacity energy storage to meet future energy consumption needs, and MOFs are outstanding materials to catalyze development of this technology.
Still a very nascent field, MOFs for Li-O 2 batteries should aim to address limitations to catalysis, ion transport, and pore structure modification. Future MOFs designed for Li-O 2 cathodes should possess open metal sites for catalysis, ideally using multiple metal species for optimized ORR and oxidation. However, care should be taken to ensure that the catalyst aids with favorable Li-O 2 reactions, rather than degradation of other organic species which may appear at the same voltages. Multi-metallic MOFs can be achieved during synthesis of the framework or through post-synthetic modification.
Defect engineering has yet to be utilized for MOF catalysis in Li-O 2 systems, but would be a promising method for enhanced porosity and catalytic activity. Both crystallite and pore morphologies should also be considered in the MOF selection to optimize delivery of O 2 to active redox sites. We envision MOFs capable of gas separation and storage selective to O 2 would also be useful for Li-O 2 batteries to prevent adverse reduction of H 2 O and CO 2 in non-aqueous electrolyte systems when air is the source of oxygen. Supercapacitors, or electrochemical double layer capacitors, operate by a voltage-driven accumulation and release of ions at electrode—electrolyte interfaces Fig.
The energy in a supercapacitor is stored in the electrostatic separation of charged ion pairs at the electrode surface, rather than through electrochemical conversion as in a battery. Therefore, free from the limitations of redox kinetics, supercapacitors exhibit superior cycling efficiency, device lifetime, high specific power, and rapid dis charging. Given that energy storage occurs only at the surfaces of the electrodes, porous electrode materials with high-surface areas are necessary.
Strategies employing MOFs within supercapacitor devices. Optimizing accessible surface area : Intrinsic crystallinity and high porosity render MOFs ideal for improving supercapacitor performance. The extensive synthetic control over MOF crystal structure, morphology, particle size, and surface composition provides a unique handle for combatting pore limitations and improving contact with the electrolyte. The reduced particle sizes of nMOFs are ideal for creating high-surface area electrodes with short diffusion paths.
The MOF was postulated to enhance charge storage by providing polar sites in the bipyridine linker for interacting with the separated ions. Similarly, supercapacitors that contained smaller UiO particles exhibited significantly higher charge storage than those with larger particles Controlling preferred crystalline facets can also dramatically improve storage capabilities, particularly in MOFs featuring pseudo-capacitive behavior. The higher concentration of exposed Ni atoms on the facet was postulated to improve the performance by providing additional redox sites and enhancing ionic conductivity.
The controlled morphology in this electrode material allows for greater pore accessibility, which boosts device performance. Together, these examples of MOFs with precise crystallographic control demonstrate yet another advantage of using frameworks for energy storage devices. Design criteria and opportunities : Supercapacitor electrode materials must have particular properties suited to both the electrolyte and operational conditions of the device. MOFs provide the variability and synthetic control to fine-tune these properties such as pore size, particle dimensions, and ionic conductivity to create reliable electrode materials.
For ongoing work in this field, the MOF pore size relative to the effective diameter of the selected electrolyte ions should be optimized, as this will greatly impact the transport of ions with or without their respective solvent shells within MOF pores and determine device capacitance. Similarly, pores should be made more accessible by reduction of particle size or exploration of high-surface area morphologies defects, hierarchically porous MOFs, etc. Electrode materials should be thermally and electrochemically stable within the operational conditions, as certain MOFs have been observed to dissolve under reductive potentials 86 , 87 , Finally, a few conductive MOFs have been tested in supercapacitors 89 , 90 , demonstrating early promise and room for development to circumvent the need for conductive carbon additives.
Ultimately, the inherent chemical and physical control and high porosity make MOFs highly advantageous for developing novel supercapacitor materials. The discovery of new materials is absolutely critical for the development of advanced energy storage devices. This section outlines bottlenecks in frontier technologies in which MOFs are uniquely suited to address Fig. Promising applications for MOFs to advance energy storage technologies MOFs are well suited to meet performance demands for high power devices, operation in extreme conditions, stabilizing the solid—electrolyte interface, and even serving as the electrolyte.
Traditional battery electrolytes are composed of flammable organic solvents, posing safety risks and reliability concerns for high energy density batteries. Replacement of solution electrolyte with solid-state electrolytes is of great interest. In addition, solid-state electrolytes must be electronically insulting to prevent shorting the battery and be mechanically and chemically robust with a reasonable operating temperature and electrochemical window. However, their brittleness and poor chemical stability under processing conditions limit their utility.
Furthermore, the lack of structural and atomistic control from top-down syntheses prevent rational materials design. MOFs, on the other hand, can potentially access good ion mobility from soft chemical interactions, solvent incorporation, and open channels. In addition, MOFs are more compatible with carbon-based electrodes than solid inorganic compounds. MOFs have been suggested for solid electrolytes previously 25 , 69 , 76 , 91 but have been scarcely employed in full device testing Gel electrolytes are also promising materials owing to high ionic conductivity and ease of preparation.
However, they have limited electrochemical stability under the high voltage and charge rate requirements of advanced energy storage devices. Gel polymers generally consist of ether, amine and ionic groups that facilitate in solvating ions for charge conduction. Such functional groups have already been incorporated into MOFs intrinsically or via post-synthetic modification 93 , An anionic framework obtained either through the use of tethered anionic functional groups or engineered anionic defect sites may similarly increase the ion transference number and positively impact rate capability.
In a battery, a native SEI is formed on the surface of the electrode from the deposition of the decomposed electrolyte components. This passivating layer generally protects against further degradation, but continuous cycling damages the SEI. An introduced MOF SEI can address these issues by preventing electrolyte decomposition, promoting ion transport, and accommodating volumetric changes.
MOF separators on top of Li metals have also been demonstrated to encourage even Li deposition to prevent dendrite formation Still in its infancy, the application of MOFs as protective layers will require ionically conductive and robust materials as well as the identification of compatible synthesis and deposition techniques upon the electrode surface. The multi-faceted nature of MOFs allows researchers to use varying in operando, in situ, and ex situ characterization techniques to study electrolyte and SEI chemistries.
High power applications, such as batteries for electric vehicles, necessitate rapid delivery of energy in a short period of time and intermittent usage. Moreover, high-rate batteries present serious safety issues as improper choice of materials can result in cell damage via dendrite formation, volumetric expansion, and thermal runaway. To counteract these concerns, flexible and durable MOFs can accommodate structural changes of cell components to inhibit dendrite growth and maintain electrode contact. In addition, their open channels can be infiltrated with electrolyte to diminish large ion concentration gradients.
In addition to demanding charge rates, there is also a growing need for energy storage devices to reliably deliver power in extreme environmental conditions. However, current battery technologies are often unsafe and unreliable when these environmental limits are pushed. For instance, the use of flammable electrolytes under increased temperatures can lead to catastrophic cell failure, while cells operating at low temperatures face severely limited power output primarily due to sluggish mass and charge transport.
Owing to their thermal and mechanical stability, MOFs used as solid-state electrolytes or separators may expand the limits of battery technology to function safely and proficiently in extreme conditions. The electronically insulating nature of most MOFs, in combination with tunable porosity and ionic conductivity, make them natural fits to act as battery separators. Catalytic MOF cathode materials or additives may also expand thermal operation ranges of batteries, for example, by reducing the charge transfer barriers at low temperatures or controlling reactions to prevent runaway at higher temperatures.
A large number of the devices discussed in this review employ MOF composite slurries, which can have limited charge conduction pathways. To address this, improved interfacial contact can be obtained using deposition methods to form uniform MOF films. Direct deposition onto a substrate ensures homogeneity and precise control of layer thickness.
Furthermore, the ability to use soft materials like polymers as substrates will permit emergent flexible electrodes. As direct deposition techniques have been explored from other classes of materials, design strategies from devices and processes that employ polymers, porous carbons and metal-oxides will likely find applicability in MOF-based devices.
The vast opportunities for new functionalities in MOFs have led to efforts to create frameworks with ordered structures at meso- and macroscale lengths 98 , 99 , Crystallographic control of MOF components can enhance porosity and availability of metal sites, ultimately benefitting device performance. New physical properties of synthesized MOFs will also expand their applications in energy storage devices.
Amorphous MOF gels and glasses have recently gained interest , , , , In particular, they show promise as novel transparent materials that possess favorable MOF properties. Glasses and gels generally do not exhibit large grain boundary resistances, are less brittle, and can be geometrically shaped. Thus, amorphous MOF materials may fill a new niche in electronic applications where enhanced flexibility, transparency, and high charge mobility are priorities. Our review has highlighted some of the most promising strategies for employing MOFs in electrochemical energy storage devices.
The characteristic properties of MOFs—porosity, stability, and synthetic tunability—provide ample design criteria to target specific bottlenecks in electrode and electrolyte development. Future identification, utilization, and development of strategies to promote charge storage and transport will set MOFs apart from porous carbons, polymer, and inorganic materials.
Despite their potential, there is still much to be learned about effective applications of MOFs in energy storage devices. Design strategies employed in polymers, carbons, ionic liquids, and solid inorganic compounds can serve as inspiration for identifying and discovering new MOF architectures for superior storage capabilities.
History and Background
Fundamental and applied knowledge gained from MOF-based devices will thus be invaluable for designing next-generation materials for emerging technologies in flexible and transparent electronics, solid-state electrolytes, and advanced energy storage devices in moderate and extreme environments. Wu, H. Metal-organic frameworks and their derived materials for electrochemical energy storage and conversion: promises and challenges.
Cao, X. Liu, J. Design strategies toward advanced mof-derived electrocatalysts for energy-conversion reactions. Energy Mater. Zheng, D. Reduction mechanism of sulfur in lithium-sulfur battery: from elemental sulfur to polysulfide. Power Sources , — Mehtab, T. Metal-organic frameworks for energy storage devices: batteries and supercapacitors.
Energy Storage 21 , — Wu, Y. Electron highways into nanochannels ofcovalent organic frameworks for high electrical conductivity and energy storage. ACS Appl. Interfaces 11 , — Xu, G. Exploring metal organic frameworks for energy storage in batteries and supercapacitors. Today 20 , — Bon, V. Metal-organic frameworks for energy-related applications.
Zhao, R. Metal-organic frameworks for batteries. Joule 2 , — Furukawa, H. The chemistry and applications of metal-organic frameworks. Science , — Yuan, S. Stable Metal—organic frameworks: design, synthesis, and applications. Lu, W. Tuning the structure and function of metal-organic frameworks via linker design. Seoane, B. Multi-scale crystal engineering of metal organic frameworks. Halder, A. Structure and properties of dynamic metal-organic frameworks: A brief accounts of crystalline-to-crystalline and crystalline-to-amorphous transformations. CrystEngComm 20 , — Eddaoudi, M.
Systematic design of pore size and functionality in isoreticular MOFs and their application in methane storage. Zhou, H. Chen, Z. Reticular chemistry in the rational synthesis of functional zirconium cluster-based MOFs. Sun, L. Kung, C. Interfaces 10 , — Wang, T. Rendering high surface area, mesoporous metal-organic frameworks electronically conductive.
Interfaces 9 , — Phang, W. Superprotonic conductivity of a UiO framework functionalized with sulfonic acid groups by facile postsynthetic oxidation. Chemie Int.
Baumann, A. Lithiated defect sites in Zr metal—organic framework for enhanced sulfur utilization in Li—S batteries. Kim, S. Achieving superprotonic conduction in metal-organic frameworks through iterative design advances. Fischer et al. Is iron unique in promoting electrical conductivity in MOFs? Sci 8 , — Shen, L. Creating lithium-ion electrolytes with biomimetic ionic channels in metal—organic frameworks. Electrolyte anions are coordinated to the MOF structure to create ion channels with high lithium-ion conductivities.
Ren, J. Review on the current practices and efforts towards pilot-scale production of metal-organic frameworks MOFs. Silva, P. Multifunctional metal-organic frameworks: from academia to industrial applications.kinun-mobile.com/wp-content/2020-11-20/myzow-how-to-locate.php
Metal-Organic Frameworks: Design and Application
Rubio-Martinez, M. New synthetic routes towards MOF production at scale. Isaeva, V. Microwave activation as an alternative production of metal-organic frameworks. Thomas-Hillman, I. Realising the environmental benefits of metal-organic frameworks: Recent advances in microwave synthesis. A 6 , — Khan, N. Synthesis of metal-organic frameworks MOFs with microwave or ultrasound: Rapid reaction, phase-selectivity, and size reduction.
Ameloot, R. Patterned growth of metal-organic framework coatings by electrochemical synthesis. Fang, C. Routes to high energy cathodes of sodium-ion batteries. Where the content of the eBook requires a specific layout, or contains maths or other special characters, the eBook will be available in PDF PBK format, which cannot be reflowed.
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Close Preview. Toggle navigation Additional Book Information. Summary Metal-organic frameworks MOFs have emerged as a new family of nanoporous materials. Reviews " The worldwide community of chemists and chemical engineers is grateful to the authors of these assembled articles and especially to Jianwen Jiang for his diligent service as editor of this timely volume. John Prausnitz, University of California, Berkeley, USA " The importance of metal—organic frameworks has grown explosively in the past decade, and molecular modeling is playing an important role in this development.
Randall Q. Snurr, Northwestern University, USA " In this comprehensive, information-packed edited volume, Jianwen Jiang brings together a collection of chapters on different aspects of modeling metal-organic frameworks. Panagiotopoulos, Princeton University, USA " This chapter book introduces high-priority subjects on metal-organic frameworks such as their structure and adsorption, separation, and catalytic properties. Katsumi Kaneko, Shinshu University, Japan. Request an e-inspection copy.
MOF books | The Fascination of Crystals and Symmetry
Added to Your Shopping Cart. View on Wiley Online Library. This is a dummy description. Metal-organic frameworks represent a new class of materials that may solve the hydrogen storage problem associated with hydrogen-fueled vehicles. In this first definitive guide to metal-organic framework chemistry, author L.
MacGillivray addresses state-of-art developments in this promising technology for alternative fuels. Providing professors, graduate and undergraduate students, structural chemists, physical chemists, and chemical engineers with a historical perspective, as well as the most up-to-date developments by leading experts, Metal-Organic Frameworks examines structure, symmetry, supramolecular chemistry, surface engineering, metal-organometallic frameworks, properties, and reactions.
About the Author Leonard R.