Applications Of Covalent Organic Frameworks Research Articles

Recent Progress in Using Covalent Organic Frameworks to Stabilize Metal Anodes for Highly-Efficient Rechargeable Batteries.

Alkali metals (Li, Na, and K) and multivalent metals (Zn, Mg, Ca, and Al) have become star anodes for developing high-energy-density rechargeable batteries due to their high theoretical capacity and excellent conductivity. However, the inevitable dendrites and unstable interfaces of metal anodes pose challenges to the safety and stability of batteries. To address these issues, covalent organic frameworks (COFs), as emerging materials, have been widely investigated due to their regular porous structure, flexible molecular design, and high specific surface area. In this minireview, we summarize the research progress of COFs in stabilizing metal anodes. First, we present the research origins of metal anodes and delve into their advantages and challenges as anodes based on the physical/chemical properties of alkali and multivalent metals. Then, special attention has been paid to the application of COFs in the host design of metal anodes, artificial solid electrolyte interfaces, electrolyte additives, solid-state electrolytes, and separator modifications. Finally, a new perspective is provided for the research of metal anodes from the molecular design, pore modulation, and synthesis of COFs.

Recent Progress in Using Covalent Organic Frameworks to Stabilize Metal Anodes for Highly‐Efficient Rechargeable Batteries

AbstractAlkali metals (e.g. Li, Na, and K) and multivalent metals (e.g. Zn, Mg, Ca, and Al) have become star anodes for developing high‐energy‐density rechargeable batteries due to their high theoretical capacity and excellent conductivity. However, the inevitable dendrites and unstable interfaces of metal anodes pose challenges to the safety and stability of batteries. To address these issues, covalent organic frameworks (COFs), as emerging materials, have been widely investigated due to their regular porous structure, flexible molecular design, and high specific surface area. In this minireview, we summarize the research progress of COFs in stabilizing metal anodes. First, we present the research origins of metal anodes and delve into their advantages and challenges as anodes based on the physical/chemical properties of alkali and multivalent metals. Then, special attention has been paid to the application of COFs in the host design of metal anodes, artificial solid electrolyte interfaces, electrolyte additives, solid‐state electrolytes, and separator modifications. Finally, a new perspective is provided for the research of metal anodes from the molecular design, pore modulation, and synthesis of COFs.

Recent progress of covalent organic frameworks in high selective separation of radionuclides

The utilization of nuclear energy power and nuclear weapon tests not only releases large amounts of radionuclides into environment, but also needs 235U as nuclear fuel for nuclear energy generation. Covalent organic frameworks (COFs) have the advantages of tunable porous structures, adjustable active sites and enough special functional groups, which assure the high selective preconcentration of target radionuclides from complex solutions. In this perspective, the selective extraction of radionuclides (U(VI) as representative cationic ion, Tc(VII) as representative anionic ion, I2 as gaseous nuclide and other nuclides) by COFs through sorption, and photocatalytic strategies are described, and the results show the high efficiency of COFs in target radionuclides removal. The perspective and challenges for the real applications of COFs in future are discussed in the end.Graphical

In-situ construction of covalent organic frameworks membrane via interfacial polymerization and crosslinking modification using trimesoyl chloride for organic solvent nanofiltration

Organic solvent nanofiltration (OSN) is a modern technology for separating and purifying organic solvents. It has the advantages of both low energy consumption and low environmental pollution. In this work, we utilized an oligomer triggered interfacial polymerization (OT-IP) method and followed by a post-IP modification using trimesoyl chloride (TMC) to synthesize a kind of covalent organic frameworks (COFs)/TMC membrane. This process involves pre-mixing both COFs monomers in a same organic solvent to form oligomers, followed by conducting an IP reaction at the interface between the organic solvent phase and an aqueous phase solution containing acetic acid as a catalyst. Subsequently, a surface modification is conducted using TMC n-hexane solution, which effectively manipulates the surface hydrophilicity, average size, solute rejection, solvent permeance and solvent resistance of the membrane. Afterward, crosslinking and solvent activation are performed to improve its solvent resistance and separation permeance. The optimized OSN membrane exhibits an ethanol permeance of 72.5 L m−2 h−1 MPa−1 with an RDB rejection of 98.4 %. Its surface roughness is as low as 3.4 nm. Furthermore, it has high permeance for both polar solvents (MeOH permeance of 176.7 L m−2 h−1 MPa−1) and weakly polar solvents (EtOAc permeance of 183.0 L m−2 h−1 MPa−1). Moreover, the optimized OSN membrane demonstrates excellent solvent resistance and excellent catalyst recovery performance. Therefore, this work presents a promising avenue for the application of COFs in OSN membranes.

Unveiling the Potential of Highly Porous Covalent Organic Frameworks for Water-Jet Rewritable Papers.

The massive use of paper has resulted in significant negative impacts on the environment. Fortunately, recent progress has been made in the field of rewritable paper, which has great potential in solving the increasing demand for paper while minimizing its environmental footprint. In this work, we report a green and economic strategy to develop ink-free rewritable paper by introducing hydrochromic covalent organic frameworks (COFs) in paper and using water as the sole trigger. When exposed to water or acidic solvents, two kinds of imino COFs change their colors reversibly from red to black. Additionally, a new visible absorption band appears, indicating that it can be transformed into another structure reversibly. This reversibility may be due to the isomerization from the diiminol to an iminol/cisketoenamine and its inability to doubly tautomerize to a diketoenamine. Specifically, we prepared the rewritable paper by loading these two COFs onto filter paper by using the decompression filtration method. When exposed to water, the paper undergoes a color change from red to black, which shows promising potential for applications in water-jet printing. Additionally, there is no significant performance degradation after 20 uses and 10 days between, further highlighting their potential as rewritable papers. To further improve its uniformity, we take the interface polymerization strategy to yield highly crystalline and more compact membranes, which are then transferred to paper to prepare writable papers. Our research has opened up a way for the application of COFs as a water-based printing material.

Recent Advancements in the Applications of Covalent Organic Frameworks for Cancer Therapeutics: A Review

Covalent organic frameworks (COFs) have gained significant attention in recent years as efficient cancer therapeutics owing to their uniform porosity, biocompatibility, diversified structures and stability in the biological medium. This review aimed to explore different synthetic strategies to obtain COFs for biomedical applications. Several synthetic procedures viz. solvothermal synthesis, ionothermal synthesis, microwave synthesis, mechanochemical synthesis, sonochemical synthesis have discussed been in terms of their applications in cancer therapy. The cancer therapeutics involves cancer drug delivery, photodynamic therapy (PDT), photo thermal therapy (PTT) and sonodynamic therapy (SDT). In some instances, single therapeutics treatments appear as inadequate effect and thus necessitate combination therapies for effective cancer termination with minimal side effects. The current study covers all the main synthetic techniques and uses of COFs in various cancer therapeutic treatments.

Amino-functional magnetic covalent organic framework as an effective adsorbent for the determination of neonicotinoids in food samples.

Recently, covalent organic frameworks have gained popularity in sample pretreatment. However, the application of covalent organic frameworks in the enrichment of hydrophilic compounds remains a challenge. Thus, a functionalized magnetic covalent organic framework equipped with amino groups was constructed using a bottom-up functionalization strategy. Considering the advantages of this novel adsorbent such as high porosity, large adsorption capacity, and hydrophilic surface, a sensitive magnetic solid-phase extraction coupled with high-performance liquid chromatography-tandem mass spectrometry method was established for the effective determination of neonicotinoids. This method exhibited good linearities with correlation coefficients ranging from 0.9983 to 0.9995, low detection limits in the range 0.003-0.009 ng g-1 and 0.001-0.013 ng mL-1, and limits of quantification in the range 0.010-0.031 ng g-1 and 0.004-0.044 ng mL-1. Furthermore, satisfactory repeatability with relative standard deviations ≤ 6.7% and spiked recoveries between 82.3 and 99.8% were obtained. This work not only provided a promising adsorbent for the sensitive determination of trace-level neonicotinoids but also represented a unique insight for effective enrichment of super hydrophilic hazards.

SERS substrate based on COF@Ag for detecting amoxicillin in honey and lake water

This study presents the design of a Surface-enhanced Raman scattering (SERS) substrate, COF@Ag, for the sensitive detection of Amoxicillin (AMX) in lake water and honey. Furthermore, the study investigates the role of covalent organic frameworks (COFs) in SERS detection. The characterization results demonstrate the capability of COFs to efficiently enrich Ag nanoparticles (AgNPs), resulting in a more concentrated distribution of hotspots and an enhanced electromagnetic field on the substrate. By employing density functional theory (DFT) simulation, the frontier electronic orbitals of COFs and AMX were analyzed, and the chemical bonds and weak interactions in the system were examined using the Interaction Region Indicator (IRI) method to propose potential enhancement mechanisms. In aqueous solutions, the linear range is 1 μg/L-30 μg/L, with a limit of detection (LOD) 0.279 μg/L. In lake water, the linear range span from 100 μg/L to 500 μg/L, with a detection limit of 8.244 μg/L. For honey, the linear range extend from 20 ng/g to 100 ng/g, with a detection limit of 2.917 ng/g. This method holds key significance in facilitating the rapid detection of amoxicillin and advancing the application of COFs in SERS.

Covalent organic frameworks: spotlight on applications in the pharmaceutical arena.

Covalent organic frameworks (COFs) have much potential in the field of analytical separation research due to their distinctive characteristics, including easy modification, low densities, large specific surface areas and permanent porosity. This article provides a historical overview of the synthesis and broad perspectives on the applications of COFs. The use of COF-based membranes in gas separation, water treatment (desalination, heavy metals and dye removal), membrane filtration, photoconduction, sensing and fuel cells is also covered. However, these COFs also demonstrate great promise as solid-phase extraction sorbents and solid-phase microextraction coatings. In addition to various separation applications, this work aims to highlight important advancements in the synthesis of COFs for chiral and isomeric compounds.

Fabrication of p-n Heterostructured Photocatalysts with Triazine-Based Covalent Organic Framework and CuInS2 for High-Efficiency CO2 Reduction.

The application of covalent organic frameworks (COFs) for the photocatalytic reduction of CO2 is mostly limited by severe charge recombination and low sunlight utilization. Herein, a triazine-based COF with an electron-rich and large π-conjugated system (TCOF) was employed as a building block and integrated with CuInS2 (CIS) to construct a noble-metal-free and high-efficiency photocatalyst for CO2 reduction. The in situ growth of CIS nanosheets on TCOF creates a p-n heterojunction, named CIS@TCOF. Compared with TCOF, the CIS@TCOF heterostructure exhibits a dramatically boosted photocatalytic performance in the reduction of CO2. The produced HCOOH yield over 10 wt % CIS@TCOF can be up to 171.2 μmol g-1 h-1 under visible light irradiation with good reproducibility, which is about 3 times as high as that over TCOF. Further in-depth studies indicate that the introduction of CIS not only enhances the visible light utilization but also restrains the recombination of photogenerated electron-hole pairs efficiently and facilitates the photoinduced charge transfer via the p-n heterojunction system due to the unique structural and compositional features. This research shows the great potential of COFs as efficient photocatalytic carbon fixation materials and provides a versatile route to construct semiconductor-COF heterostructures for photocatalysis.

Progress on application of covalent organic frameworks for advanced lithium metal batteries

Since Li metal batteries (LMBs) theoretically possess high energy density, they are the most concerned rechargeable batteries at present. Whereas, poor safety and short cycling lives of the LMBs originate from various problems of LMBs components including cathode/anode materials, electrolytes, and separators have impeded their practical application. Covalent organic frameworks (COFs), which feature diverse structures, flexible frameworks, and versatile functions, have been extensively investigated as potential alternatives for above mentioned key components of LMBs. With the rational design and pre-/postsynthesis functionalization, COFs can be precisely customized for targeted functionalities, which can tackle the issues of LMBs. The current status of the application of COFs in LMBs, which covers working principles and strategies for improving electrochemical performance, will be discussed in this review. What's more, the challenges and potential directions for further developments of COFs in LMBs are presented in the final section.

A graft-modified sponge with COFs for wastewater treatment and iodine adsorption

Azo dyes, used in large quantities in drinks, have become a threat to human health. In the treatment of dyes, the method of chemical adsorption is often used due to its simple and efficient features. Covalent organic frameworks (COFs) material with the characteristics of stability and porosity has great potential for the adsorption of azo dyes. However, the application of COFs is severely limited by their poor mechanical properties and hard recovery. By the strategy of in situ growth using the original functional groups of the sponge, COFs are successfully grafted onto melamine sponges to give rise to a porous sponge@COFs material. The material can adsorb up to 621 mg g−1 of Congo red, a common azo dye. In addition, it exhibits strong adsorption of iodine solution with the saturated adsorption of 1504.76 mg g−1. More importantly, sponge@COFs can selectively adsorb azo dyes with S–O- bond. The adsorption mechanism is inferred as the connect of S–O- in the Congo red molecule with O atom of sponge@COFs. Also, the mechanism of iodine adsorption is explained to be due to the coordination of C atoms in COFs with I atom. In addition, as an adsorbent, the material is recoverable, stable and heat resistant. Relying on the stronger performance and lower cost, sponge@COFs is expected to be developed as a new adsorbent.

Precise local functionalization of covalent organic framework for efficient carrier separation in photocatalytic H2 evolution

Improving carrier transport rate and suppressing carrier recombination are two huge challenges in the photocatalytic applications of covalent organic frameworks (COFs)-based semiconductors. In this study, we propose a strategy to enhance carrier transport efficiency by regulating the local microenvironment of the electronic characteristics in the acceptors through structural modification. Three different functional group-modified fluorenone-based COFs were successfully synthesized through precise design. The results demonstrate that the photocatalytic hydrogen evolution activities of COFs modified with electron-donating functional groups are significantly higher than that of COFs modified by electron-withdrawing functional groups. Specifically, the photocatalytic hydrogen evolution performance of phenyl-modified FOOPh-COF could reach 228.5 mmol h−1g−1, which is 11.8 times higher than that of Br atom-modified FOOBr-COF (19.3 mmol h−1g−1). Femtosecond time-resolved transient absorption spectroscopy (fs-TAS) results reveal that introducing phenyl groups into the acceptor significantly enhances its inhibitory effect on the carrier recombination. Density functional theory calculations further prove that modifying the acceptor by electron-donating functional groups can achieve the increased electron density in the CO active center. The electrons in the CO region in the phenyl-modified fluorenone structure are more enriched and delocalized, which can enhance the speed of electron migration, shorten the migration distance, and inhibit carrier recombination. After loading Pt, it has the lowest H* adsorption-free energy among three samples. This work clarifies the importance of the functionalization modification of COFs’ acceptors in regulating the local electronic environment and further provides new insights into the structure–activity relationship of fluorenone-based COF-based photocatalysts.

The Cutting‐Edge Progress in Covalent Organic Framework‐Based Nanomedicine

Covalent organic frameworks (COFs) are a class of porous crystalline materials with exceptional properties, constructed through covalently linked organic units. COFs are extensively applied in the field of biomedicine, particularly in the context of anticancer treatments. First, this review summarizes the diverse synthetic methods of COFs, including solvothermal synthesis, microwave‐assisted synthesis, room temperature synthesis, interface synthesis, ionothermal techniques, mechanical grinding, and electrochemical methods, and their impacts on the material's structure and performance. Second, COFs exhibit tremendous potential in the field of cancer therapy because of their orderly lattice structure, tunable pore sizes, high surface area, and excellent thermal and chemical stability. Therefore, the article deeply explores the applications of COFs in diverse cancer treatment modalities, encompassing early diagnostic bioimaging, drug delivery, various phototherapies, chemodynamic therapy, sonodynamic therapy, radiation therapy, and their combined therapeutic strategies. Finally, the article points out current research challenges and future directions in this field.

Adsorption of typical dyes in water by sponge based covalent organic frameworks: Pore size and mechanism

This study addressed the ambiguity surrounding the relationship between the pore size of covalent organic frameworks (COFs) and their adsorption capacity and rate. To achieve this, we synthesized COFs with five distinct pore sizes (COF1-COF5) and conducted a comprehensive analysis using kinetic models. Our findings indicated that the adsorption capacity and rate of methyl orange (MO) increased linearly with the pore size of COFs, from 1.25 nm to 2.57 nm. Notably, COF3, with a pore size of 2.57 nm, exhibited the highest adsorption performance for MO, boasting an impressive capacity of 43.07 mg/g. Furthermore, we tackled the challenge of COFs powder recovery by employing a one-pot synthesis method to create SP-COFs, where COFs powder was loaded onto polyurethane sponge. Through rigorous adsorption and analytical experiments, we demonstrated that SP-COF3 achieved rapid recovery while efficiently adsorbing MO, maintaining a high removal efficiency of over 95% even after 8 reuse cycles. The mechanism underlying MO adsorption on SP-COF3 was attributed to electrostatic interaction and hydrogen bonding, with the possibility of π-π interaction also being considered. Overall, this study provides valuable new insights into the tailored synthesis of COFs with specific structures and functionalities, shedding light on the crucial relationship between pore size and adsorption behavior. The development of SP-COFs presents a promising approach to enhance the practical application of COFs as highly efficient adsorbents.

Constructing bifunctional and robust covalent organic frameworks via three-component one-pot Doebner reaction for Cr(VI) removal

The integral part of covalent organic frameworks (COFs) is covalent bonds. Thus, stable and functional links must be developed to expand the potential applications of COFs. Herein, in situ linkage functionalization using a three-component irreversible Doebner reaction was achieved to fabricate chemically stable carboxylic acid-bearing COFs (Tp-Tta-COOH and Tp-Tapb-COOH), which have abundant chelating groups and ordered electron donor–acceptor moieties facilitating charge separation for effective Cr(VI) adsorption and photoreduction, respectively. These functionalized COFs are more effective at Cr(VI) removal via adsorption and photoreduction than their unfunctionalized counterparts (Tp-Tta and Tp-Tapb). The synergy of adsorption and photocatalysis is crucial to effectively remove Cr(VI) from aqueous solutions. This synergy empowers Tp-Tta-COOH to be used continuously for Cr(VI) removal without any elution after each cycle. Furthermore, Tp-Tta-COOH exhibits high chemical stability, durability, and recyclability. This study will promote the development of durable and useful COF materials for real-world applications.

Covalent Organic Frameworks: Their Composites and Derivatives for Rechargeable Metal-Ion Batteries.

Covalent organic frameworks (COFs) have attracted considerable interest in the field of rechargeable batteries owing to their three-dimensional (3D) varied pore sizes, inerratic porous structures, abundant redox-active sites, and customizable structure-adjustable frameworks. In the context of metal-ion batteries, these materials play a vital role in electrode materials, effectively addressing critical issues such as low ionic conductivity, limited specific capacity, and unstable structural integrity. However, the electrochemical characteristics of the developed COFs still fall short of practical battery requirements due to inherent issues such as low electronic conductivity, the tradeoff between capacity and redox potential, and unfavorable micromorphology. This review provides a comprehensive overview of the recent advancements in the application of COFs, COF-based composites, and their derivatives in rechargeable metal-ion batteries, including lithium-ion, lithium-sulfur, sodium-ion, sodium-sulfur, potassium-ion, zinc-ion, and other multivalent metal-ion batteries. The operational mechanisms of COFs, COF-based composites, and their derivatives in rechargeable batteries are elucidated, along with the strategies implemented to enhance the electrochemical properties and broaden the range of their applications.

Construction of Ketoenamine-Based Covalent Organic Frameworks with Electron-Rich Sites for Efficient and Rapid Removal of Iodine from Solution.

Porous covalent organic frameworks (COFs) have been widely used for the efficient removal of iodine from solution due to their abundance of electron-rich sites. In this study, two kinds of ketoenamine-based COFs, TpBD-(OMe)2 and TpBD-Me2, are successfully synthesized via Schiff base reaction under solvothermal conditions using 1, 3, 5-triformylphoroglucinol as aldehyde monomer, o-tolidine and o-dianisidine as amino monomers. The ability of TpBD-(OMe)2 and TpBD-Me2 to adsorb iodine in cyclohexane or aqueous solutions has been quantitatively analyzed and interpreted in terms of adsorption sites. TpBD-Me2 possesses two adsorption sites, -NH- and -C=O, and exhibits an adsorption capacity of 681.67 mg/g in cyclohexane, with an initial adsorption rate of 0.6 g/mol/min with respect to COF unit cell. The adsorption capacity of TpBD-(OMe)2 can be as high as 728.77 mg/g, and the initial adsorption rate of TpBD-(OMe)2 can reach 1.2 g/mol/min in the presence of oxygen atoms between the methyl group and the benzene ring. Compared with TpBD-Me2, the higher adsorption capacity and adsorption rate of TpBD-(OMe)2 towards iodine are not only reflected in organic solvents, but also in aqueous solutions. It is proven through X-ray photoelectron spectroscopy and Raman spectroscopy that iodine exists in the form of I2, I3-, and I5- within TpBD-(OMe)2 and TpBD-Me2 after adsorption. This work not only expands the application of COFs in the field of iodine adsorption, but also provides research ideas and important an experimental basis for the optimization of iodine adsorption sites.

Recent Advances of Covalent Organic Frameworks as Water Splitting Electrocatalysts

Developing high-performance, durable, yet low-lost catalysts for electrocatalytic water splitting technology has been a research priority to tackle the global energy crisis. In this regard, covalent organic frameworks (COFs) have received great attention as promising water splitting electrocatalysts as they can provide an excellent platform for the settlement of electrocatalytic active site, high porosity, and good stability. In this review, recent advances on the design and application of COFs for water electrolysis, which are hydrogen and oxygen evolution reaction electrocatalysts, are briefly discussed. Among them, both noble and non-noble metals containing COFs as well as metal-free COF-based electrocatalysts are elaborated. Furthermore, a brief outlook on the development of COFs in the field of water splitting electrocatalysis is provided.

Covalent Organic Frameworks (COFs): Characteristics and Applications for Lithium-Ion Batteries (LIBs) and Sodium Ion Batteries (SIBs)

Covalent organic frameworks (COFs) belong to a family of porous organic materials that form 2D or 3D tuned structures via a covalent bond formation between organic blocks. COFs exhibit a remarkable array of characteristics that make them highly promising materials for various applications. COFs are characterized by their chemical and physical stability, their highly porous structure, and their easy structural tunability. They emerged as promising candidates for electrode materials in advanced energy storage devices such as sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs). COFs can be precisely customized for each application via pore engineering and framework functionalization as well as the pre- and post-synthesis. Research has been conducted to examine the effect of various functional groups, active redox sites, pore size, and interlayer distances on the performance of COFs as electrode materials. Herein, this review reports the most recent advances in using COFs as electrode materials in both LIBs and SIBs. It also discusses the synthesis of COFs, structural engineering, and pore engineering. The main advantages and challenges that arise with the application of COFs in rechargeable batteries are presented. This review concluded that COFs do have the potential as anode materials in both LIBs and SIBs by virtue of their crystalline structure and high porosity that enable efficient ion diffusion and storage. COFs provided enhanced battery electrochemical performance, improved energy density, and prolonged cycle life.