Covalent Organic Frameworks Materials Research Articles

Ionic liquid/covalent organic framework/silica composite material: Green synthesis and chromatographic evaluation

BackgroundDue to their large surface area and distinctive adsorption affinity, covalent organic frameworks (COFs) appear to be good candidates as liquid chromatographic separation materials with good application prospect. The development of COF materials in chromatographic science is currently in an exploratory stage. Especially, the practicability of COF@silica composite materials as liquid chromatographic stationary phases needs further exploration. Reasonably integrating a functional component such as ionic liquid (IL) into the COF@silica composite materials may provide customized functionality to achieve the purpose of synthesizing multi-functional COF based stationary phases. ResultsIn this study, an IL modified COF bonded silica composite material (IL-COF@SiO2) was successfully synthesized by using an environmentally friendly deep eutectic solvent as the reaction medium instead of the frequently-used organic solvent. The synthesized IL-COF@SiO2 composite material combines the excellent separation ability of COF and the excellent mass transfer function of spherical porous silica microsphere, and meanwhile, the introduction of IL endows COF@SiO2 with preferable separation performance. The slurry-packed IL-COF@SiO2 liquid chromatographic column could be applied to effectively separate hydrophobic and hydrophilic compounds with preferable separation selectivity and high column efficiency. By investigating the retention behavior and influencing factors, a mixed-mode retention mechanism was found. Multiple interaction forces endow the IL-COF@SiO2 with a hydrophilic-hydrophobic balance performance, demonstrating a good application prospect as a versatile liquid chromatographic separation material. SignificanceIn this study, a new strategy is proposed for greenly synthesizing a novel IL-COF@SiO2 composite material under mild conditions, which expands the potential application of COF materials in chromatographic science. One particular point to note is that the reaction medium in each step of the preparation process is low toxic and degradable deep eutectic solvent, which conforms to the concept of green chemistry.

Covalent organic framework enhanced aggregation-induced emission of berberine and the application for detection

In this work, we prepared TaTp-COF, a covalent organic framework material with porous and uniform spheres, by hydrothermally reacting 1,3,5-tris (4-aminophenyl) benzene (TaPb) with terephthalaldehyde (TpTa). TaTp-COF could significantly enhance the aggregation-induced emission (AIE) of berberine (BBR), a natural plant medicine, which was related to the porous structure, the suitable voids, and the hydrogen bonding between TaTp-COF and BBR that could limit the free movement of BBR. The unique emission properties of BBR on TaTp-COF were investigated and used for the sensitive detection of BBR based on the fluorescence intensity of AIE, with a linear range of 10–100 μ mol/L (R2 = 0.9991) and a detection limit of 0.0453 μ;mol/L. Finally, the TaTp-COF was successfully applied to the detection of BBR in real samples, achieving good recoveries and satisfactory relative standard deviations.

Host–guest interactions in framework materials: Insight from modeling

The performance of metal–organic and covalent organic framework materials in sought-after applications—capture, storage, and delivery of gases and molecules, and separation of their mixtures—heavily depends on the host–guest interactions established inside the pores of these materials. Computational modeling provides information about the structures of these host–guest complexes and the strength and nature of the interactions present at a level of detail and precision that is often unobtainable from experiment. In this Review, we summarize the key simulation techniques spanning from molecular dynamics and Monte Carlo methods to correlate ab initio approaches and energy, density, and wavefunction partitioning schemes. We provide illustrative literature examples of their uses in analyzing and designing organic framework hosts. We also describe modern approaches to the high-throughput screening of thousands of existing and hypothetical metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) and emerging machine learning techniques for predicting their properties and performances. Finally, we discuss the key methodological challenges on the path toward computation-driven design and reliable prediction of high-performing MOF and COF adsorbents and catalysts and suggest possible solutions and future directions in this exciting field of computational materials science.

Bimetallic atom synergistic covalent organic framework for efficient electrochemical nitrate reduction

Electrochemical reduction has emerged as an effective method to remove nitrate from industrial wastewater. Nevertheless, this method has been largely restricted by the lack of low-cost and efficient electrocatalysts. Here, we demonstrate a porous two-dimensional covalent organic framework (2D COF) material as a promising electrocatalyst, which is obtained via a Schiff base reaction by combining copper phthalocyanine with bipyridine sites for precise copper coordination. The bidentate coordinated COF material has a robust framework and stable chemical property, allowing the isolated Cu sites to be embedded into the regular pores with controlled and uniformly dispersed active centers. The well-defined design of the reaction monomers makes the COF material to trap nitrate ions more easily from aqueous solution. By rationally combining the synergistic effect of 2D COF and Cu active sites, the CuTAPc-CuBPy-COF electrocatalyst shows much higher nitrate reduction efficiency than CuTAPc-BPy-COF under low superpotential and different nitrate concentrations. The high NO3− conversion (90.3 %) and NH3 selectivity (69.6 %) are achieved. To our best acknowledge, this is the first demonstration of bi-copper-based COF material for NO3−RR electrocatalysis, which provides a new direction for the rational design of COFs as significant electrocatalysts for nitrate reduction.

Research progress on preparation and applications of covalent organic framework-based chromatographic stationary phases

Given continuous developments in industrial and scientific research, the separation and analysis of complex systems with high sensitivity, throughput, and selectivity is facing new challenges. Chromatography plays an irreplaceable role in separation science and is widely applied in environmental monitoring, pharmaceutical analysis, and food safety. Owing to their outstanding advantages, such as high loading capacity, precise quantification, and good reproducibility, chromatographic separation techniques based on various retention mechanisms have been utilized to detect different analytes. The stationary phase is the core material of chromatographic columns and has an extremely important influence on their separation performance. The selectivity and efficiency of separation largely depend on the chromatographic stationary phase. However, traditional stationary phases, such as silicon-based matrices, are characterized by complex preparation processes, poor permeability, large mass transfer resistance, and a narrow pH range. In addition, polymer matrices show poor mechanical stability and susceptibility to swelling, which limit their applications in the field of separation. Therefore, the development of novel stationary phases with the advantages of traditional stationary phases has become a research emphasis in the field of analytical science in efforts to meet separation requirements under different environments. Various stationary phases based on novel porous materials, such as metal organic frameworks (MOFs), porous organic cages (POCs), and covalent organic frameworks (COFs), are used for chromatographic separation. As mesh crystalline porous materials, MOFs have the advantages of a large surface area, adjustable structure, and easy functionalization; thus, they are widely used as chromatographic stationary phases in reverse-phase chromatography, hydrophilic-mode chromatography, mixed-mode chromatography, and other separation modes. However, because the pore size of MOFs is small and most MOFs demonstrate poor chemical stability under acidic or alkaline conditions, their applications in chromatographic separation are greatly limited. COFs are porous, crystalline polymer materials composed of light elements (H, O, C, N, B, and Si) connected via covalent bonds. Their advantages include a low density, large specific surface area, high porosity, good chemical and thermal stability, regular pores, and adjustable pore sizes. Because of their unique structures and properties, COFs are widely used in many fields such as catalysis, enrichment, gas capture, and sensing. COF materials are also suitable for separation analysis and considered ideal materials for novel chromatographic stationary phases. This review summarizes the latest research progress on the preparation and applications of COF-based chromatographic stationary phases over the past five years. First, the preparation of COF-based stationary phases (SiO2@COFs stationary phase, COFs monolithic stationary phase, pure COFs stationary phase and COFs-coated stationary phase) is introduced. The latest applications of COF-based stationary phases in the separation of organic compounds, isomers, and chiral compounds are then described in detail. Finally, the future development trends and challenges of chromatographic stationary phases based on COFs are discussed to provide new ideas for the future design and development of novel chromatographic stationary phases based on COFs.

Preparation of sulfonic acid functionalized covalent organic framework solid phase microextraction fibers and their application in the analysis of neurotransmitters in the mouse brain

Neurotransmitters (NTs) are essential for intercellular communication and primarily include monoamine, amino acid, and cholinergic NTs. These molecules play important roles in the body's stress response, motor coordination, neuronal communication, and homeostatic functions. Previous studies have shown that abnormal changes in NT levels are associated with various neurological disorders. Therefore, the development of accurate analytical methods for NT detection will enhance the current understanding on complex neuropathophysiology by providing functional knowledge and techniques for early diagnosis, thereby facilitating the development of new therapeutic options for the related diseases. The solid phase microextraction (SPME) technique combines sample preparation, separation, and enrichment in a single step and is minimally invasive, low cost, solvent free, and high throughput. SPME has been successfully applied to the in vivo analysis of target analytes in animal, human, and plant tissues. The coating material plays a significant role in the development of in vivo SPME methods and must meet various analytical requirements, including a suitable geometry for the SPME device, high extraction capacity, excellent selectivity, and wide extraction coverage for the target analytes. Covalent organic frameworks (COFs) are porous crystalline polymers constructed from organic framework units through strong covalent bonds; these materials are characterized with a low density, large specific surface area, permanent porosity, excellent chemical/thermal stability, and easy functionalization.In this study, a sulfonic acid-functionalized COF material (COF-SO3H) with good crystallinity, excellent chemical/thermal stability, strong hydrophobicity, a uniform mesoporous structure, and narrow pore size distribution was prepared using 2,4,6-triformylphloroglucinol and 1,4-diamino-2-nitrobenzene as monomers. Then, the COF-SO3H was coated onto the surface of stainless-steel fibers and used for in vivo enrichment of NTs. The structural properties of COF-SO3H were characterized using various techniques, such as scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), and X-ray diffraction (XRD), all of which showed that COF-SO3H had a good crystalline structure and uniform mesopore distribution with a specific surface area of 46.17 m2/g. Compared with the SPME fibers of HLB, C18, MCX, amino, and PXC columns, the prepared COF-SO3H fibers showed better extraction efficiency for the target NTs. Next, the factors affecting SPME efficiency were optimized. The optimal desorption solvent was formic acid-methanol-water (0.5∶49.5∶50, v/v/v), and the optimal extraction and desorption times were 15 min. A method for the in vivo analysis of NTs in the brains of mice was established by combining the COF-SO3H fibers with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) under optimal conditions. The NTs were separated on an Acquity UPLC BEH-C18 analytical column (100 mm×2.1 mm, 1.7 μm) with 0.1% formic acid aqueous solution (A) and acetonitrile (B) as the mobile phases. The flow rate was set to 0.2 mL/min, and the gradient elution procedure was as follows: 0-4 min, 5%B-6%B; 4-7 min, 6%B-5%B; 7-11 min, 5%B. Under optimal conditions, the method showed good linearity (r2>0.99). The limits of quantification (S/N≥5) were in the range of 0.003-0.005 μg/mL and 3-5 μg/mL for monoamine and amino acid NTs, respectively, with RSDs of less than 20%. The method showed good precision (0.80%-9.70%) and accuracy (2.08%-17.72%), with absolute matrix effects in the range of 82.22%-117.92%. These values reflect the good purification and enrichment abilities of the proposed fibers for the target analytes. Finally, the established SPME method was combined with UPLC-MS/MS and successfully applied to quantify target NTs in the brains of mice. The proposed strategy provides a practical method for the in vivo detection and quantitative analysis of NTs and expands the applications of functionalized COF materials for the analysis of various targets.

Function-Led Design of Covalent-Organic-Framework Membranes for Precise Ion Separation.

Insufficient access to clean water and resources has emerged as one of the most pressing issues affecting people globally. Membrane-based ion separation has become a focal point of research for the generation of fresh water and the extraction of energy elements. This Review encapsulates recent advancements in the selective ion transport of covalent organic framework (COF) membranes, accomplished by strategically pairing diverse monomers to create membranes with various pore sizes and environments for specific purposes. We first discuss the merits of using COF materials as a basis for fabricating membranes for ion separation. We then explore the development of COF membranes in areas such as desalination, acid recovery, and energy element extraction, with a particular emphasis on the fundamental principles of membrane design. Lastly, we address both theoretical and practical challenges, as well as potential opportunities in the targeted design of ion-selective membranes. The goal of this Review is to stimulate future investigative efforts in this field, which is of significant scientific and strategic importance.

Design, synthesis, and properties of olefin‐linked covalent organic frameworks modified by heck coupling reaction

AbstractThe covalent organic frameworks (COFs) with olefin linkages are attractive materials for nonlinear optics due to their small energy band gap and large π‐electron separation domain. In this paper, a post‐synthetic modification (PSM) by applying a heck coupling reaction on olefin‐linked COFs was applied for the first time to obtain five functionalized triazine‐based covalent organic framework materials. The synthesized materials were tested for their relevant photophysical and electrochemical properties, and their third‐order nonlinear optical properties were tested using the Z‐scan technique. The experimental results indicate that the post‐modified COF (W4‐2) exhibits third‐order nonlinear polarizability χ3 that is 1.51 times higher than the unmodified COF (W4).

Lattice Shrinkage of 2D-COFs under Electron Beam Irradiation

Over the past two decades, covalent organic frameworks (COFs) have become the most widely studied porous crystalline materials. Their specific physical and chemical properties are determined by the arrangement of atoms (crystal structure). Therefore, the determination of their structure is arguably the most important characterization step for COFs. Although single-crystal X-ray diffraction is the most widely used method for structure determination, confirmation of the structure of COFs is limited to lattice fringes in transmission electron microscopy (TEM) because of their small crystal size (nanocrystals) or poor crystal quality. At present, many two-dimensional COFs (2D-COFs) have clear powder X-ray diffraction (PXRD) patterns, but specific lattice fringes are not available for all 2D-COFs. This severely hinders the development of the COF field. Here, we discovered the lattice shrinkage behavior of COFs under electron beam irradiation by comparing the lattice fringes of 2D-COFs under different conditions. By comparing the lattice fringes of a 1,3,5-tris-(4-aminophenyl)triazine-1,3,5-tris-(4-formylphenyl)triazine covalent organic framework (TAPT-TFPT COF) at room temperature and under liquid nitrogen freezing conditions, we found that the lattice fringes are in good agreement with the PXRD and the theoretical values of the COF (2.213 nm) under freezing conditions. However, the lattice fringe spacing is only 1.656 nm at room temperature. The discovery not only provides new insights into the TEM characterization of COFs, but also further expands the range of crystalline COF materials.

Assessing CO2 Adsorption Behavior onto Free-Standing, Flexible Organic Framework-PVDF Composite Membrane: An Empirical Modeling and Validation of an Experimental Data Set.

Covalent organic framework (COF) materials have greatly expanded their range in a variety of applications since the cognitive goal of a highly organized and durable adsorbent is quite rational. The characteristics of a conjugated organic framework are combined with an industrially relevant polymer to produce a composite membrane optimized for selectively adsorbing carbon dioxide (CO2) gas across a wide temperature range. Additionally, treatment of the composite membrane with cold atmospheric plasma (CAP) that specifically enhanced the parent membrane's surface area by 36% is established. Following CAP treatment, the membrane accelerates the CO2 uptake by as much as 66%. This is primarily due to a Lewis acid-base interaction between the electron-deficient carbon atom of CO2 and the newly acquired functionalities on the COFs@PVDF membrane's surface. In particular, the C-N bonds, which appear to be a higher electron density site, play a key role in this interaction. Moreover, the empirical model proposed here has confirmed CO2 adsorption phenomena in the COF@PVDF composite membrane, which closely matches the findings from the experimental data set under designated operating conditions. As a result, the current study may pave the way for future design work as well as refine the covalent framework polymer composite membrane's features, revealing a more sophisticated approach to addressing CO2 capture problems.

Triptycene Based 3D Covalent Organic Frameworks (COFs)—An Emerging Class of 3D Structures

Covalent Organic Frameworks (COFs) are a newly emerged class of porous materials consisting of organic building blocks linked by strong covalent bonds. The physical and chemical properties of COFs, i.e., modularity, porosity, well-developed specific surface area, crystallinity, and chemical-thermal stability, make them a good application material, especially in the aspects of adsorption and gas separation. The organic compositions of their building blocks also render them with biocompatible properties; therefore, they also have potential in biomedical applications. Depending on the symmetry of the building blocks, COF materials form two-dimensional (2D COF) or three-dimensional (3D COF) crystal structures. 3D COF structures have a higher specific surface area, they are much lighter due to their low density, and they have a larger volume than 2D COF crystals, but, unlike the latter, 3D COF crystals are less frequently obtained and studied. Selecting and obtaining suitable building blocks to form a stable 3D COF crystal structure is challenging and therefore of interest to the chemical community. Triptycene, due to its 3D structure, is a versatile building block for the synthesis of 3D COFs. Polymeric materials containing triptycene fragments show good thermal stability parameters and have a very well-developed surface area. They often tend to be characterized by more than one type of porosity and exhibit impressive gas adsorption properties. The introduction of a triptycene backbone into the structure of 3D COFs is a relatively new procedure, the results of which only began to be published in 2020. Triptycene-based 3D COFs show interesting physicochemical properties, i.e., high physical stability and high specific surface area. In addition, they have variable porosities with different pore diameters, capable of adsorbing both gases and large biological molecules. These promising parameters, guaranteed by the addition of a triptycene backbone to the 3D structure of COFs, may create new opportunities for the application of such materials in many industrial and biomedical areas. This review aims to draw attention to the symmetry of the building blocks used for COF synthesis. In particular, we discussed triptycene as a building block for the synthesis of 3D COFs and we present the latest results in this area.

Water-assisted hydrogen spillover in Pt nanoparticle-based metal–organic framework composites

Hydrogen spillover is the migration of activated hydrogen atoms from a metal particle onto the surface of catalyst support, which has made significant progress in heterogeneous catalysis. The phenomenon has been well researched on oxide supports, yet its occurrence, detection method and mechanism on non-oxide supports such as metal–organic frameworks (MOFs) remain controversial. Herein, we develop a facile strategy for efficiency enhancement of hydrogen spillover on various MOFs with the aid of water molecules. By encapsulating platinum (Pt) nanoparticles in MOF-801 for activating hydrogen and hydrogenation of C=C in the MOF ligand as activated hydrogen detector, a research platform is built with Pt@MOF-801 to measure the hydrogenation region for quantifying the efficiency and spatial extent of hydrogen spillover. A water-assisted hydrogen spillover path is found with lower migration energy barrier than the traditional spillover path via ligand. The synergy of the two paths explains a significant boost of hydrogen spillover in MOF-801 from imperceptible existence to spanning at least 100-nm-diameter region. Moreover, such strategy shows universality in different MOF and covalent organic framework materials for efficiency promotion of hydrogen spillover and improvement of catalytic activity and antitoxicity, opening up new horizons for catalyst design in porous crystalline materials.

Magnetoresistance in Organic Spin Valves Based on Acid‐Exfoliated 2D Covalent Organic Frameworks Thin Films

AbstractCovalent organic frameworks (COFs), as a burgeoning class of crystalline porous materials, have made significant progress in their application to optoelectronic devices such as field‐effect transistors, memristors, and photodetectors. However, the insoluble features of microcrystalline two‐dimensional (2D) COF powders limit development of their thin film devices. Additionally, the exploration of spin transport properties in this category of π‐conjugated skeleton materials remains vacant thus far. Herein, an imine‐linked 2D Py‐Np COF nanocrystalline powder was synthesized by Schiff base condensation of 4,4′,4′′,4′′′‐(pyrene‐1,3,6,8‐tetrayl)tetraaniline and naphthalene‐2,6‐dicarbaldehyde. Then, we prepared a large‐scale free‐standing Py‐Np COF film via a top‐down strategy of chemically assisted acid exfoliation. Moreover, high‐quality COF films acted as active layers were transferred onto ferromagnetic La0.67Sr0.33MnO3 (LSMO) electrodes for the first attempt to fabricate organic spin valves (OSVs) based on 2D COF materials. This COF‐based OSV device with a configuration of LSMO/Py‐Np COF/Co/Au demonstrated a remarkable magnetoresistance (MR) value up to −26.5 % at 30 K. Meanwhile, the MR behavior of the COF‐based OSVs exhibited a highly temperature dependence and operational stability. This work highlights the enormous application prospects of 2D COFs in organic spintronics and provides a promising approach for developing electronic and spintronic devices based on acid‐exfoliated COF thin films.

Magnetoresistance in Organic Spin Valves Based on Acid-Exfoliated 2D Covalent Organic Frameworks Thin Films.

Covalent organic frameworks (COFs), as a burgeoning class of crystalline porous materials, have made significant progress in their application to optoelectronic devices such as field-effect transistors, memristors, and photodetectors. However, the insoluble features of microcrystalline two-dimensional (2D) COF powders limit development of their thin film devices. Additionally, the exploration of spin transport properties in this category of π-conjugated skeleton materials remains vacant thus far. Herein, an imine-linked 2D Py-Np COF nanocrystalline powder was synthesized by Schiff base condensation of 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl)tetraaniline and naphthalene-2,6-dicarbaldehyde. Then, we prepared a large-scale free-standing Py-Np COF film via a top-down strategy of chemically assisted acid exfoliation. Moreover, high-quality COF films acted as active layers were transferred onto ferromagnetic La0.67 Sr0.33 MnO3 (LSMO) electrodes for the first attempt to fabricate organic spin valves (OSVs) based on 2D COF materials. This COF-based OSV device with a configuration of LSMO/Py-Np COF/Co/Au demonstrated a remarkable magnetoresistance (MR) value up to -26.5 % at 30 K. Meanwhile, the MR behavior of the COF-based OSVs exhibited a highly temperature dependence and operational stability. This work highlights the enormous application prospects of 2D COFs in organic spintronics and provides a promising approach for developing electronic and spintronic devices based on acid-exfoliated COF thin films.

Covalent Organic Framework-Based Electrolytes for Lithium Solid-State Batteries—Recent Progress

Covalent organic frameworks (COFs) have emerged as a promising platform of materials for solid-state battery electrolytes due to their porous and robust structures, and their special spaces such as 1D and 3D, as well as their ability to be modified with functional groups. This review focuses on the use of COF materials in solid-state batteries and explores the various types of bonds between building blocks and the impact on key properties such as conductivity, transfer number, and electrochemical stability. The aim is to provide an overview of the current state of COF-based electrolytes for solid-state batteries and to highlight the prospects for future development in this field. The use of COF materials in solid-state batteries has the potential to overcome limitations such as low theoretical energy density, limited temperature stability, and the risk of fire and explosion associated with traditional liquid electrolyte batteries. By providing a more in-depth understanding of the potential applications of COF-based electrolytes in solid-state batteries, this review seeks to pave the way for further advancements and innovations in this field.

A novel thiazole-based covalent organic framework as turn-off fluorescent sensor for detection of aniline and triethylamine in liquid and vapor phase

Due to the diverse chemical structures and varying basicity of amines, the development of rapid, portable, and reversible methods for the selective recognition of trace organic amines in the environment remains a challenge. Herein, a novel recyclable and selective turn-off fluorescent sensor for organic amines detection based on covalent organic framework (COF) was developed. As-synthesized COF, TAPB-BTDD exhibits good crystallinity, high chemical stability and strong fluorescence, which can selectively recognize triethylamine (TEA) and aniline in both liquid and vapor phase. The COF material demonstrates impressively low LOD values for aniline and triethylamine in solution, estimated to be 27 nM and 170 nM, respectively. Moreover, when detecting aniline and triethylamine vapors, the calculated LOD values are 20.1 ppb and 106.4 ppb, respectively. In addition, TAPB-BTDD showed basically unchanged emission intensities and rapid response to the amines after ten recycling tests, suggesting that the COF has high stable recycle repeatability. The combination of experimental analysis and density functional theory (DFT) calculations demonstrates that the unique fluorescence-quenching response of TAPB-BTDA can be attributed to the photoinduced electron transfer (PET) between the amines and the COF. This COF-based sensor offers a promising solution for the accurate and reliable detection of organic amines in various environmental settings.

Synthesis of covalent organic framework materials and their application in the field of sensing

Synthesis of covalent organic framework materials and their application in the field of sensing

Vinylene-Linked Emissive Covalent Organic Frameworks for White-Light-Emitting Diodes.

Covalent organic frameworks (COFs) have gained considerable attention due to their highly conjugated π-skeletons, rendering them promising candidates for the design of light-emitting materials. In this study, we present two vinylene-linked COFs, namely, VL-COF-1 and VL-COF-2, which were synthesized through the Knoevenagel condensation of 2,4,6-trimethyl-1,3,5-triazine with terephthalaldehyde or 4,4'-biphenyldicarboxaldehyde. Both VL-COF-1 and VL-COF-2 exhibited excellent chemical and thermal stability. The presence of vinylene linkages between the constituent building blocks in these COFs resulted in broad excitation and emission properties. Remarkably, the designed VL-COFs demonstrated bright emission, fast fluorescence decay, and high stability, making them highly attractive for optoelectronic applications. To assess the potential of these VL-COFs in practical devices, we fabricated white-light-emitting diodes (WLEDs) coated with VL-COF-1 and VL-COF-2. Notably, the WLEDs coated with VL-COF-1 achieved high-quality white light emission, closely approximating standard white light. The promising performance of VL-COF-coated WLEDs suggests the feasibility of utilizing COF materials for stable and efficient lighting applications.

Functional COFs for Electrochemical Sensing: From Design Principles to Analytical Applications

AbstractAt present, applications of covalent organic frameworks (COFs), a class of novel crystalline porous materials fabricated by organic structural blocks only containing light elements such as C, H, N, O and B through strong covalent bonds, in electrochemical sensing have entered a period of rapid development and showed great potential in various analytical fields such as environmental analysis, food analysis, pharmaceutical analysis, biological and clinical analysis owing to their unique advantages including regular porosity, large specific surface area, periodical ordered structure, extended π‐conjugated system, abundant functional groups and outstanding thermal and chemical stability. But there are still many concerns that need to be urgently solved for further electrochemical sensing application including improvement of electric conductivity and enhancement of selectivity. Limited by poor conductivity and low recognition ability of primitive COFs, they always need to be further functionalized. To further promote the development of COFs‐based electrochemical sensing technology, here, we summarize and review the recent advances on construction of two‐dimensional functional COFs materials for electrochemical sensing applications and related sensing device setups in detail, including design strategies, preparation methods, modification considerations, sensing principles and analytical applications, and tentatively propose development prospects and outlooks in future.

Application of New COF Materials in Secondary Battery Anode Materials.

Covalent organic framework materials (COFs), as a new type of organic porous material, not only have the characteristics of flexible structure, abundant resources, environmental friendliness, etc., but also have the characteristics of a regular structure and uniform pore channels, so they have broad application prospects in secondary batteries. Their functional group structure, type, and number of active sites play a crucial role in the performance of different kinds of batteries. Therefore, this article starts from these aspects, summarizes the application and research progress of the COF anode materials used in lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries in recent years, discusses the energy storage mechanism of COF materials, and expounds the application prospects of COF electrodes in the field of energy storage.