Development Of Covalent Organic Frameworks Research Articles

Construction of covalent organic frameworks membranes in situ through nonsolvent-induce phase separation for fast and accurate nanofiltration

With the development of covalent organic frameworks (COFs), their superior separation performance in membrane separation has gradually becoming apparent. The method of combining COFs with membrane materials is crucial for their applications prospect. In this study, inspired by the traditional Chinese mortise and tenon structure, we selected 1,3,5-triacetaldehyde mesityl phenol (TFP) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) as the reactive building monomers. P-Phenylenediamine (PDA) was introduced into the casting solution to construct Polyether-sulfone (PES) bottom membranes with amino ligand sites, utilizing the phase transition effect generated by the non-invasive solvent-induced method (NIPS). Subsequently, COFs composite nanofiltration membranes with two-dimensional layered structures were prepared through mild interfacial polymerization (IP) under optimized reaction conditions. The synthesis of COFs composite nanofiltration membranes was demonstrated through a series of characterizations, including scanning transmission electron microscopy and infrared spectroscopy. The COFs composite nanofiltration membranes synthesized by this method exhibited better alignment, greater chemical stability, and higher separation efficiency compared to traditional interracially polymerized COFs composite nanofiltration membranes. As the method involves the addition of additives, it can be more widely applied to a broad range of organic polymer membranes. Furthermore, we demonstrated the effectiveness of the COF composite nanofiltration membranes produced using this method in the separation of molecular dyes. They exhibited rejection exceeding 99% for 0.1 g L−1 methyl blue (MB), Congo red (CR) and chrome black-T (EBT). Additionally, they achieved separation fluxes of up to 300 L m−2 h−1 bar−1 for mixed solutions (dyes/salts) and proved to be effective under extreme conditions, such as 1 M HCl/NaOH. Moreover, COFs-NH2PES composite nanofiltration membranes exhibited the ability to efficiently separate dye molecules of different sizes. This work introduces new ideas for constructing stable and durable COF functional composite membrane materials for practical applications.

Opportunity and Challenge of Emerging COFs in Chemiresistive Sensing for Gas and Humidity

AbstractNovel 2D materials for chemiresistive sensors are attractive due to their large surface area and structure diversity. Covalent organic frameworks (COFs) have received much attention due to their unique properties, including the abundant choice of organic building units, permanent pore structure and crystallinity, which show huge potential of implement in gas and humidity detection in complex environment. Recently, the development of the synthesis and modification methods for COFs powder and film contributes to the sensitivity and compatibility in chemiresistive sensors and integrated devices. In the present review, the current synthesis methods of COFs powder and film as well as their application in the chemiresistive sensors are summarized. The current challenge and future modification strategy are discussed for the further development of COFs as active materials in gas and humidity sensors.

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 Framework-based Solid-State Electrolytes, Electrode Materials, and Separators for Lithium-ion Batteries.

The increasing global energy consumption has led to the rapid development of renewable energy storage technologies. Lithium-ion batteries (LIBs) have been extensively studied and utilized for reliable, efficient, and sustainable energy storage. Nevertheless, designing new materials for LIB applications with high capacity and long-term stability is highly desired but remains a challenging task. Recently, covalent organic frameworks (COFs) have emerged as superior candidates for LIB applications due to their high porosity, well-defined pores, highly customizable structure, and tunable functionalities. These merits enable the preparation of tailored COFs with predesigned redox-active moieties and suitable porous channels that can improve the lithium-ion storage and transportation. This review summarizes the recent progress in the development of COFs and their composites for a variety of LIB applications, including (quasi) solid-state electrolytes, electrode materials, and separators. Finally, the challenges and potential future directions of employing COFs for LIBs are also briefly discussed, further promoting the foundation of this class of exciting materials for future advances in energy-related applications.

Hexaazatriphenylene‐Based Two‐Dimensional Conductive Covalent Organic Framework with Anisotropic Charge Transfer

AbstractThe development of covalent organic frameworks (COFs) with efficient charge transport is of immense interest for applications in optoelectronic devices. To enhance COF charge transport properties, electroactive building blocks and dopants can be used to induce extended conduction channels. However, understanding their intricate interplay remains challenging. We designed and synthesized a tailor‐made COF structure with electroactive hexaazatriphenylene (HAT) core units and planar dioxin (D) linkages, denoted as HD‐COF. With the support of theoretical calculations, we found that the HAT units in the HD‐COF induce strong, eclipsed π–π stacking. The unique stacking of HAT units and the weak in‐plane conjugation of dioxin linkages leads to efficient anisotropic charge transport. We fabricated HD‐COF films to minimize the grain boundary effect of bulk COFs, which resulted in enhanced conductivity. As a result, the HD‐COF films showed an electrical conductivity as high as 1.25 S cm−1 after doping with tris(4‐bromophenyl)ammoniumyl hexachloroantimonate.

Hexaazatriphenylene-based two-dimensional conductive covalent organic framework with anisotropic charge transfer.

The development of covalent organic frameworks (COFs) with efficient charge transport is of high immense interest for application in opto-electronic devices. To enhance COF charge transport properties, electroactive building blocks and dopants can be used to induce extended conduction channels. However, understanding their intricate interplay remains challenging. We designed and synthesized a tailor-made COF structure with electroactive hexaazatriphenylene (HAT) core units and planar dioxin (D) linkages, denoted as HD-COF. With the support of theoretical calculations, we found that the HAT units in the HD-COF induce strong, eclipsed π-π stacking. The unique stacking of HAT units and the weak in-plane conjugation of dioxin linkages leads to efficient anisotropic charge transport. We fabricated HD-COF films to minimize the grain boundary effect of bulk COFs, which resulted in enhanced conductivity. As a result, the HD-COF films showed an electrical conductivity as high as 1.25 S cm-1 after doping with tris(4-bromophenyl)ammoniumyl hexachloroantimonate.

Layered 3D Covalent Organic Framework Films Based on Carbon-Carbon Bonds.

The development of covalent organic frameworks (COFs) during the past decades has led to a variety of promising applications within gas storage, catalysis, drug delivery, and sensing. Even though most described synthesis methods result in powdery COFs with uncontrolled grain size, several approaches to grow COF films have recently been explored. However, in all COFs so far presented, the isolated materials are chemically homogeneous, with all functionalities homogeneously distributed throughout the entire material. Strategies to synthetically manipulate the spatial distribution of functionalities in a single film would be game changing. Specifically, this would allow for the introduction of local functionalities and even consecutive functions in single frameworks, thus broadening their synthetic versatility and application potential. Here, we synthesize two 3D crystalline COF films. The frameworks, the ionic B-based and neutral C-based COFs, have similar unit cell parameters, which enables their epitaxial stacking in a layered 3D COF film. The film growth was monitored in real time using a quartz crystal microbalance, showing linear growth with respect to reaction time. The high degree of polymerization was confirmed by chemical analysis and vibrational spectroscopy. Their polycrystalline and anisotropic natures were confirmed with grazing incidence X-ray diffraction. We further expand the scope of the concept by making layered films from COF-300 and its iodinated derivative. Finally, the work presented here will pave the path for multifunctional COF films where concurrent functionalities are embedded in the same crystalline material.

Beyond Solvothermal: Alternative Synthetic Methods for Covalent Organic Frameworks.

Covalent organic frameworks (COFs) are crystalline porous organic materials that hold a wealth of potential applications across various fields. The development of COFs, however, is significantly impeded by the dearth of efficient synthetic methods. The traditional solvothermal approach, while prevalent, is fraught with challenges such as complicated processes, excessive energy consumption, long reaction times, and limited scalability, rendering it unsuitable for practical applications. The quest for simpler, quicker, more energy-efficient, and environmentally benign synthetic strategies is thus paramount for bridging the gap between academic COF chemistry and industrial application. This Review provides an overview of the recent advances in alternative COF synthetic methods, with a particular emphasis on energy input. We discuss representative examples of COF synthesis facilitated by microwave, ultrasound, mechanic force, light, plasma, electric field, and electron beam. Perspectives on the advantages and limitations of these methods against the traditional solvothermal approach are highlighted.

Covalent Organic Frameworks for Energy Conversion in Photocatalysis.

Intensifying energy crises and severe environmental issues have led to the discovery of renewable energy sources, sustainable energy conversion and storage technologies. Photocatalysis is a green technology that converts eco-friendly and inexhaustible solar energy into high-energy chemicals. Covalent organic frameworks (COFs) are porous materials constructed by covalent bonds that show promising potential for converting solar energy into chemicals owing to their pre-designable structures, high crystallinity, and porosity. Herein, we highlight recent progress in the synthesis of COF-based photocatalysts and their applications in water splitting, CO2 reduction, and H2O2 production. The challenges and future opportunities for the rational design of COFs for advanced photocatalysts are discussed. This review is expected to promote further development of COFs toward photocatalysis.

Covalent Organic Frameworks for Energy Conversion in Photocatalysis

AbstractIntensifying energy crises and severe environmental issues have led to the discovery of renewable energy sources, sustainable energy conversion, and storage technologies. Photocatalysis is a green technology that converts eco‐friendly solar energy into high‐energy chemicals. Covalent organic frameworks (COFs) are porous materials constructed by covalent bonds that show promising potential for converting solar energy into chemicals owing to their pre‐designable structures, high crystallinity, and porosity. Herein, we highlight recent progress in the synthesis of COF‐based photocatalysts and their applications in water splitting, CO2 reduction, and H2O2 production. The challenges and future opportunities for the rational design of COFs for advanced photocatalysts are discussed. This Review is expected to promote further development of COFs toward photocatalysis.

Chiral-Induced Ultrathin Covalent Organic Frameworks Nanosheets with Tunable Circularly Polarized Luminescence.

Development of covalent organic frameworks (COFs) with circularly polarized luminescence (CPL) is still challenging. Here we first reported ultrathin COFs nanosheets (NS) based CPL materials using a chiral induced-synthesis strategy. Chiral amines served as chiral inducers to give COF TpBpy with chirality and participated in the modification of TpBpy, inhibiting the fluorescence quenching caused by π-π stacking to form ultrathin luminescent chiral COFs (chirCOFs) NS. The obtained chirCOFs R-/S-TpBpy NS had strong chirality and intense red CPL property with a |glum| of ∼0.02. Afterward, the carboxyl containing green and blue fluorescent dye molecules were postmodified onto the chirCOFs NS (chirCOFs/Dyes) to achieve color-adjustable CPL. Due to the chirality and energy transfer between chirCOFs and dye groups, the obtained chirCOFs/Dyes showed strong chirality and increased and tunable photoluminescence, exhibiting excellent, tunable, and amplified CPL performance with a maximum |glum| of ∼0.1, which was ∼5 times stronger than that of as-prepared chirCOFs NS. Moreover, the corresponding chirCOFs NS were dispersed into a polydimethylsiloxane (PDMS) matrix to form wafer size, highly transparent, and flexible COFs/PDMS films for practical CPL application. This study opens a new strategy to prepare ultrathin chirCOFs NS with strong and tunable CPL by chiral induction and provides a new approach for the preparation of transparent, large size, and flexible COFs composite films in chiral optical applications.

Spirobifluorene-Based Three-Dimensional Covalent Organic Frameworks with Rigid Topological Channels as Efficient Heterogeneous Catalyst

Although the past decade has witnessed tremendous progress in the development of covalent organic frameworks (COFs), three-dimensional (3D) COFs fabrications and characterizations are still much le...

Crystalline, porous, covalent polyoxometalate-organic frameworks for lithium-ion batteries

Abstract The development of covalent organic frameworks (COFs) with new building units is of critical importance for enriching the structural diversity and expanding their functions. However, the construction of COFs has been thus far limited primarily to traditional organic linkers. Herein, we report three-dimensional porous crystalline covalent polyoxometalate-organic frameworks (CPOFs) constructed from both inorganic and organic building blocks with reversible covalent bonds. These highly crystalline CPOFs exhibited 3-fold interpenetrated diamondoid topology, permanent porosity and high stability. Furthermore, these CPOFs could be directly applied as anode materials for lithium-ion batteries (LIBs) and displayed high reversible capacity (as high as 550 mA h g−1), rate performance, and cycling stability (up to 500 cycles).

Recent development of covalent organic frameworks (COFs): synthesis and catalytic (organic-electro-photo) applications

The review focuses on recent developments in the synthetic methodologies of COFs and their applications in the field of organocatalysis, electrocatalysis and photocatalysis. Future scope of COFs in the field are also described.

Crystalline Covalent Organic Frameworks from Triazine Nodes as Porous Adsorbents for Dye Pollutants

The development of covalent organic frameworks (COFs) with nodes and spacers, designed to maximize their functional properties, is a challenge. Triazines exhibit better electron affinity than benzene-based aromatic rings; therefore, structures based on 1,3,5-substituted triazine-centered nodes are more stable than those from 1,3,5-benzene-linked COFs. Compared to COFs prepared from flat, rigid sp2 carbon-linked triazine nodes, the O-linked flexible tripodal triazine-based COF demonstrates several unpredictable properties such as an increase in crystallinity and cavity size. In this study, the COF prepared from O-linked flexible 2,4,6-tris(p-formylphenoxy)-1,3,5-triazine serves as an excellent absorbent for removing methylene blue from water. Our results demonstrate that COF is highly stable in water and functions as a robust adsorbent. Its adsorption isotherm is consistent with the Langmuir model and its adsorption kinetics follows a pseudo-second order model. Moreover, the COF was characterized using elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, solid-state ultraviolet–visible spectroscopy, and X-ray diffraction. It exhibited permanent porosity, a high specific surface area (279.5 m2·g–1), and was chemically and thermally stable. Photophysical studies revealed that the COF exhibits a low bandgap energy value of 3.07 eV, indicating its semiconducting nature.

Electronic Structure of Two-Dimensional π-Conjugated Covalent Organic Frameworks

Increasing attention is being given to the development of covalent organic frameworks (COFs) that are based on monolayers of fully π-conjugated structures. At first glance, such two-dimensional (2D) polymer networks could simply be viewed as a mere extension into a second dimension of the quasi-one-dimensional (1D) conjugated polymers at the origin of the field of organic electronics. However, such a view misses essential characteristics coming specifically from 2D lattice symmetry. Our aims in this Perspective are twofold. We seek (i) to provide a conceptual, chemistry-oriented theoretical description of the impact on the electronic structure of this extension from 1D to 2D and (ii) to establish chemical structure–symmetry–electronic property relationships for this class of 2D π-conjugated COFs.

Covalent organic frameworks (COFs): perspectives of industrialization

In this highlight, we review the state-of-the-art development of COFs from an industrial point of view in five aspects, including their types, growth mechanisms, synthetic methods, processability and applications.

Homochiral 2D Porous Covalent Organic Frameworks for Heterogeneous Asymmetric Catalysis.

There have been breakthroughs in the development of covalent organic frameworks (COFs) with tunability of composition, structure, and function, but the synthesis of chiral COFs remains a great challenge. Here we report the construction of two-dimensional COFs with chiral functionalities embedded into the frameworks by imine condensations of enantiopure TADDOL-derived tetraaldehydes with 4,4'-diaminodiphenylmethane. Powder X-ray diffraction and computer modeling together with pore size distribution analysis show that one COF has a twofold-interpenetrated grid-type network and the other has a non-interpenetrated grid network. After postsynthetic modification of the chiral dihydroxy groups of TADDOL units with Ti(O(i)Pr)4, the materials are efficient and recyclable heterogeneous catalysts for asymmetric addition of diethylzinc to aldehydes with high enantioselectivity. The results reported here will greatly expand the scope of materials design and engineering for the creation of new types of functional porous materials.