Covalent organic frameworks for applications in lithium batteries

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

In recent years, a new class of highly crystalline advanced permeable materials covalent-organic frameworks (COFs) have garnered a great deal of attention thanks to their remarkable properties, such as their large surface area, highly ordered pores and channels, and controllable crystalline structures. The lower physical stability and electrical conductivity, however, prevent them from being widely used in applications like photocatalytic activities and innovative energy storage and conversion devices. For this reason, many studies have focused on finding ways to improve upon these interesting materials while also minimizing their drawbacks. This review article begins with a brief introduction to the history and major milestones of COFs development before moving on to a comprehensive exploration of the various synthesis methods and recent successes and signposts of their potential applications in carbon dioxide (CO2 ) sequestration, supercapacitors (SCs), lithium-ion batteries (LIBs), and hydrogen production (H2 -energy). In conclusion, the difficulties and potential of future developing with highly efficient COFs ideas for photocatalytic as well as electrochemical energy storage applications are highlighted.

Covalent organic frameworks (COFs) are a type of crystalline porous polymers that possess ordered structures and eternal pores. Because of their unique structural characteristics and diverse functional groups, COFs have been used in various application fields, such as adsorption, catalysis, separation, ion conduction, and energy storage. Among COFs, the fluorine-containing COFs (fCOFs) have been developed for special applications by virtue of special physical and chemical properties resulting from fluorine element, which is a nonmetallic halogen element and possesses strong electronegativity. In the organic chemistry field, introducing fluorine into chemicals enables those chemicals to exhibit many interesting properties, and fluorine chemistry increasingly plays an important role in the history of chemical development. The introduction of fluorine in COFs can enhance the crystallinity, porosity, and stability of COFs, making COFs having superior performances and some new applications. In this review, the synthesis and application of fCOFs are systematically summarized. The application involves photocatalytic production of hydrogen peroxide, photocatalytic water splitting, electrocatalytic CO2 reduction, adsorption for different substances (H2 , pesticides, per-/polyfluoroalkyl substances, polybrominated diphenyl ethers, bisphenols, and positively charged organic dye molecules), oil-water separation, energy storage (e.g., zinc-ion batteries, lithium-sulfur batteries), and proton conduction. Perspectives of remaining challenges and possible directions for fCOFs are also discussed.

Covalent organic frameworks (COFs) are a family of crystalline porous networks having applications in various fields, including gas and energy storage. Despite respectable progress in the synthesis of such crystalline materials, examples of the use of template-free methods to construct COFs having hollow nano- and microstructures are rare. Furthermore, all reported methods for synthesizing these hollow structural COFs have involved [4 + 2] and [3 + 2] condensations. Herein, we report the synthesis of hollow microspherical and microtubular carbazole-based COFs through template-free, one-pot, [3 + 3] condensations of the novel triamine 9-(4-aminophenyl)-carbazole-3,6-diamine (Car-3NH2) and triformyl linkers with various degrees of planarity. Depending upon the monomer's planarity, a unique morphological variety was observed. A time-dependent study revealed that each COF formed through an individual mechanism depended on the degree of planarity of the triformyl linker; it also confirmed that the hollow structures of these COFs formed through inside-out Ostwald ripening. Our COFs exhibited high Brunauer-Emmett-Teller surface areas (up to ca. 1400 m2 g-1), excellent crystallinity, and high thermal stability. Moreover, the CO2 uptake capacities of these COFs were excellent: up to 61 and 123 mg g-1 at 298 and 273 K, respectively. The high surface areas facilitated greater numbers of strong interactions with CO2 molecules, leading to high CO2 uptake capacities. Moreover, the prepared COFs exhibited redox activity because of their redox-active triphenylamine and pyridine groups, which can be utilized in electrochemical energy storages. Accordingly, such hollow COFs having high surface areas appear to be useful materials for industrial and biological applications.

Because of its high voltage, high specific energy, and other good qualities, lithium-ion batteries have recently become one of the most popular studies. In the context of nanomaterials, this research investigates the function of nanomaterials in the application of lithium-sulfur and lithium-air batteries. In addition to examining the classification, benefits and drawbacks, uses and advances of nanomaterials, this essay also examines the fundamentals of two batteries, as well as the uses of nanomaterials in both types of batteries. The results show that nanomaterials have a very large surface area and a sudden change in material properties because of their arrival at the nanoscale, and have very good mechanical and optical properties, which have a very good contribution to the performance of the batteries. However, it was discovered that nanomaterials in lithium-ion battery applications still have issues, such as high cost and challenging synthesis procedures, through the investigation of several nanomaterials in two batteries. In addition to offering fresh perspectives for society, this study seeks to better understand the economic and safety issues associated with two batteries used in practical production.

Owing to their high surface area, excellent electrolyte permeability and ample diffusion pathways for charge transport, porous and hollow-structured electrochemically active materials attract more attention as the electrodes. In general, the process of template preparation method is used to achieve hollow structured materials over the last few decades. However, the complicated preparation process including removal of template and surface modification often results in poor uniformity, low reproducibility, and high cost of porous structure. Moreover, it incorporates functional chemicals with specific homogeneity and dispersity into the hollow porous intercrystalline structure. These problems hinder the development and application in energy storage and conversion devices of the diversified porous and hollow-structured materials. The metal-organic frameworks (MOFs), consisting of organic linkers and coordinated inorganic clusters, appear as an excellent collection of porous crystal material series with high surface areas, high porosity, and tunable structures. However, their low conductivity and electrolyte instability limit the further use of MOFs in the field of LIBs. Recently, how electrode materials for Lithium–ion batteries (LIBs) are designed and prepare using MOFs has attracted more attention. The composite materials derived from MOFs including nanostructured porous carbons and metal oxide uaing self-sacrificial template synthetic route not only solves the problem of low conductivity but also maintains the high surface area and porous structure of MOFs, providing abundant active sites for insertion/deinsertion or adsorption/desorption; Furthermore, composite materials derived from MOFs increase the complexity of nanostructures in terms of structural units and chemical components. In particular, large pore volume and open pore structure are critical to loading guest species, accommodating mechanical strains and facilitating mass transport. In this paper, we briefly examined the production of MOF-derived materials for applications in LIBs. The optimization and modification of an MOFs morphology were implemented according to the electrode material requirement for LIBs. Moreover, the preparation of MOFs-derived electrode materials with porous, hollow, or complicated construction and their effects on electrochemical performance were described. Finally, the challenge and trend in production of electrode materials derived from MOFs were analyzed.

Covalent organic frameworks (COFs), an emerging class of layered, porous framework materials, have garnered significant recognition as electrode materials in metal-ion batteries. The electrostatic potential of the COF's pore is a fundamental yet underexplored aspect in the context of its role in electrochemical energy storage. Using density functional theory simulations, we have studied a set of experimentally relevant triazine-based COFs, considering 1,4-benzene, 1,4-naphthalene, 2,6-naphthalene, and 4,4'-biphenyl as linkers, which differ by aromaticity and connectivity, to quantify the effect of pore electrostatic potential (ESP) on the electrochemical performances of a Li-ion battery. Our results reveal that, upon tuning the linkers' aromaticity, the ESP of the pore can be tuned up to ∼2 eV, with a concomitant voltage modulation as high as 0.4 V. Our results also suggest that, due to the presence of different heteroatom-based binding motifs, the intercalation mechanism in the COF is significantly different compared to that of a conventional graphite electrode. Furthermore, we have investigated COF systems with pore walls functionalized by -F, -CN, and -OH groups, revealing a strong dependency of ESP of the pore on the electron-donating or -withdrawing substituent group, resulting in further modulation of voltage. We find that, while such thermodynamically controlled electrochemical behavior is determined by the ESP of the COF's pore, the Li-ion migration barrier is independent of ESP. Overall, our study provides an in-depth understanding of the impact of pore ESP in triazine-based COFs in determining their electrochemical energy storage performance, opening up a route map in linker engineering aspects of the COFs.

The demand to develop lithium-ion batteries (LIBs) is growing as their consumption in various applications rises. In this regard, it is very important to pay attention to materials with suitable properties for use in LIBs. The energy storage capacity, cycle life, weight, and recycling of aging batteries are expected to improve with these materials. Recently, covalent organic frameworks (COFs) have shown great promise for use in cathode, anode, electrolyte, and separators of LIBs due to their numerous properties, including porosity and excellent physical and chemical stability. This review discusses the application of COFs in the next-generation of LIBs. First of all, the Main components, working principles, and characteristics of LIBs are described. After that, the advantages, applications, and synthesis methods of COFs are discussed. Finally, the application of COFs in various parts of LIBs by key features and the associated challenges is highlighted. In this review, we focus on improving batteries by introducing and developing COFs as a new-generation of materials for energy storage applications to overcome the current limitations and provide promising alternatives for current LIBs.

Currently, electrolytes used in lithium-ion batteries are flammable and leaky, causing safety problems when used under high temperatures or extreme conditions. Solid electrolytes can fundamentally avoid the occurrence of such issues, at the same time, it can significantly increase the energy density of solid state lithium batteries. Solid electrolytes are classified into inorganic solid electrolytes and solid polymer electrolytes. Although inorganic solid electrolytes have the high mechanical strength and room temperature ionic conductivity, it has poor flexibility and complicated preparation process. In contrast, solid polymer electrolyte has good elasticity and good interface contact, which can overcome many disadvantages of the inorganic solid electrolyte. Among them, polyethylene oxide (PEO) is first proposed as a polymer electrolyte. Due to its excellent mechanical properties, electrochemical stability and thermal stability, it has been a hot topic for polymer solid electrolytes for decades. However, its low room temperature ionic conductivity limits practical application. Given the problems existing in PEO-based polymer electrolytes, several methods for improving ionic conductivity have been proposed. The primary methods include plasticization, the organic-inorganic composite, and polymer blending. Comparing these methods, it can be seen that adding plasticizers to the polymer can effectively increase the conductivity of the electrolyte, but at the same time it will cause a decrease in the mechanical properties, and the safety issues limit its application in lithium-ion batteries. Inorganic fillers can balance the problems of ionic conductivity and mechanical properties, but the construction of a good filler-polymer dispersion system is complicated in preparing such composite electrolytes, design a new type of multi-dimensional the ion transport network also face tremendous challenges. Undoubtedly, in the future research, inorganic fillers will be the dominant means in the modification of composite electrolytes. Compared with the former two modification methods, polymer blending is easy to operate and friendly to industry, but low ionic conductivity at room temperature still exist. To give full play to the advantages of polymer blending, using it as an auxiliary means to improve the performance of composite electrolytes will be the primary development direction of such modification methods. PEO is the most widely studied polymer electrolyte. Even though a large number of modification methods have emerged in its development history, the ionic conductivity at room temperature is still limited to a relatively low level. To meet the needs of the application in lithium-ion batteries, a high operating temperature (50−70℃) is still needed, the biggest problem remains exist. To solve the problems in polymer solid electrolytes, the research directions in the future may mainly focus on: Expanding the modification method of PEO to other polymer electrolyte host materials, broadening the scope of research, and finding the available polymer electrolytes at room temperature. Concerned about the preparation of ultra-thin polymer electrolytes, reducing the ion transmission path to increase the transmission efficiency of lithium ions between positive and negative electrodes. Effectively combines inorganic solid electrolytes and solid polymer electrolytes to give full play to their advantages. In addition, exploring the effect of inorganic filler morphology on the conductivity of the composite electrolyte will also deserve attention. Many one-dimensional, two-dimensional materials can build ion transport networks so that lithium ions can travel rapidly along the path. With the deepening of research, it is expected that PEO-based polymer electrolytes may replace liquid electrolytes and become an essential cornerstone for building the next generation of safe and reliable lithium-ion batteries.

Increasing global energy demand urgently requires a sustainable energy storage device. Lithium-ion battery (LIB) technology has gathered wide attention toward the development of reliable, efficient, and sustainable energy storage systems. Despite all these advantages, designing an electrode material of LIBs with large cycle life, high specific capacity, and rate performance all at the same time remains a major challenge. Very recently, covalent organic frameworks (in short COFs) have attracted immense attention as an electrode material for efficient Li storage in a LIB due to their incredibly diverse and tunable structures. Here, we have studied a highly porous and semiconducting COF, i.e., COF-IITI-0, as an electrode material for the storage of Li atoms in a LIB. A hybrid periodic density functional theory (DFT) method has been implemented to investigate the Li intercalation mechanism, framework and electronic properties, and its theoretical capacity and average voltage. We report the lithium atom intercalation in the pristine COF-IITI-0 material consisting of maximum active groups (C6H4, C3N3, BO2C2) when it is used as electrode materials for LIBs. It has the highest capacity among the most polymer-based electrode materials so far. For the highest amount of lithium (up to 10 Li) atoms intercalated in the unit cell of the pure COF-IITI-0, it has been computationally predicted that the material would have a large theoretical capacity of 369 mAh g–1 with the highest average voltage about 4.8 eV. Therefore, we can say that the pristine COF-IITI-0 porous COF may be an auspicious effective electrode material for LIBs with such superior capacity and cell voltage. This work lays the foundation for future experimental exploration of Li-intercalated COFs for Li storage applications.

This review explores recent advances in lithium-sulfur (Li-S) batteries, promising next-generation energy storage devices known for their exceptionally high theoretical energy density (∼2500 W h kg-1), cost-effectiveness, and environmental advantages. Despite their potential, commercialization remains limited by key challenges such as the polysulfide shuttle effect, sulfur's insulating nature, lithium metal anode instability, and thermal safety concerns. This review provides a comprehensive and forward-looking perspective on emerging material strategies-focusing on cathode, electrolyte, and anode engineering-to overcome these barriers. Special emphasis is placed on advanced sulfur-carbon composites, including three-dimensional graphene frameworks, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and MXene-based materials, which have demonstrated significant improvements in sulfur utilization, redox kinetics, and cycling stability. Innovations in electrolytes-particularly solid-state and gel polymer systems-are discussed for their roles in suppressing polysulfide dissolution and enhancing safety. This review also examines lithium metal anode protection strategies, such as use of artificial SEI layers and 3D lithium scaffolds and lithium alloying. Finally, it discusses critical issues related to large-scale manufacturing, safety, and commercial scalability. With ongoing innovation in multifunctional materials and electrode design, Li-S batteries are well positioned to transform energy storage for electric vehicles, portable electronics, and grid-scale systems.

Covalent organic frameworks (COFs) are emerging as promising electrode materials due to their high surface area, tunable porosity, and design flexibility. However, their practical use in energy storage remains limited by their poor stability and electrochemical performance. Here, we report a nitrogen-rich COF, synthesized via an irreversible aromatic nucleophilic substitution between hexaazatriphenylenehexacarbonitrile and 3,3′-diaminobenzidine (HAT-DAB COF), forming stable – C═N– and −C–N– linkages. The framework integrates redox-active phenazine and arylamine units, offering a porous, crystalline, and nitrogen-rich architecture. Structural and morphological analyses confirm its robust and porous nature. As a bifunctional electrode, HAT-DAB COF shows excellent performance in lithium-ion batteries, with a specific capacity of 265 mAh/g, an energy density of ∼607 Wh/kg, and ∼98% Coulombic efficiency over hundreds of cycles. As a supercapacitor, it delivers 110.5 mF/cm2 at 1 mV/s, with ∼95% capacitance retention and 100% Coulombic efficiency over 8000 cycles. Capacitance arises from a synergy of electric double-layer and redox (Faradaic) processes, with the diffusive component retained even at high scan rates, indicating strong pseudocapacitor behavior. This work demonstrates the value of irreversible linkages and rational redox-active design in achieving durable, high-performance COFs for next-generation energy storage applications.

Metal-covalent organic frameworks (MCOFs), a novel class of organic electrode materials that integrate the electrical conductivity of metal–organic frameworks (MOFs) with the structural stability of covalent organic frameworks (COFs), demonstrate remarkable potential for lithium-ion battery (LIBs) applications. In this study, a novel iron-coordinated MCOF of DHBD-TFP-Fe-COF was synthesized via a one-step coordination strategy using 3,3′-dihydroxybenzidine (DHBD) and 2,4,6-triformylphloroglucinol (TFP) as precursors in the presence of FeCl3·6H2O, which exists in an enol-imine form due to the coordination of iron ions. Compared with the counterpart of DHBD-TFP-COF without Fe3+-coordination, DHBD-TFP-Fe-COF exhibits superior electrochemical performance as an anode material for LIBs, retaining the specific capacities of 400 mAh g–1 after 3000 cycles at 1 A g–1 and 200 mAh g–1 after 12,000 cycles at 5 A g–1. The Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) characterizations indicate the involvement of Fe3+ in charge storage, contributing to improved electrochemical performance.

Vinyl-bearing sp2 carbon-conjugated covalent organic framework composites for enhanced electrochemical performance in hydrogen evolution reaction and lithium–sulfur batteries

Covalent organic frameworks (COFs) have attracted increasing interest for their use as electrode materials for lithium-ion batteries (LIBs) by virtue of their microporous crystalline structures and robust networks. However, the tightly stacked bulk COFs and their intrinsic low conductivity inevitably result in an inefficient utilization of redox-active sites so as to lower the electrochemical performance. Herein, we proposed a general strategy to improve the energy storage capability of polyimide (PI)-COF based cathode materials, which included the decrease of their stacked layer numbers to a few layers via a mechanical milling method for the efficient utilization of redox-active sites and the incorporation of few-layer COF sheets with chemically reduced graphene oxide (rGO) to increase the charge transfer. The excellent electrochemical performance of the composite few-layer PI-COFs with rGO cathodes indicated that reducing the layer number of COFs and incorporating rGO may pave the way for the successful development of COF-based organic electrodes for LIBs.