Use Of Covalent Organic Frameworks Research Articles

Microwave-assisted synthesis of triazine covalent organic frameworks via friedel-crafts reaction for use in treating brackish Water

Water scarcity is becoming an ever-growing problem in society. This is all due to the rapid increase in human population, harsh changes in the weather climate. New approaches for treating and recycling brine water into freshwater instead of discharging are needed, significantly large reduction in energy usage and decreasing harmful impact to the environment must be achieved in brine recovery. This study aims to introduced green technology into the reclamation of brine water by use of covalent organic frameworks (COFs) materials which will be used as part of a novel triazine-based COFs material which can be used as a nanomembrane for desalination of brine water from water treatment plants at Umgeni Water. Current technological approaches used are inefficient and unsuitable in 3rd world, developing countries including the republic of South Africa. This work focuses on a microwave-assisted synthesis involving Friedel Crafts reaction between monomers to yield a product of a triazine-based covalent organic frameworks (COFs) membranes. To confirm the products high resolution transmission electron microscopy (HRTEM), carbon NMR (13C NMR) with peaks at chemical shifts of 131, 143 and 172 ppm respectively. Fourier-transform infrared spectroscopy (FTIR) was employed and showed N-H stretches at a region of 3396 to 3050 cm-1. The COFs that were successfully synthesised are going to be incorporated on a polymeric substrate to fabricate a nanofiltration membrane and applied for nanofiltration or ultrafiltration purposes.

Recent advances in the fabrication of organic solvent nanofiltration membranes using covalent/metal organic frameworks.

Organic solvent nanofiltration (OSN) has evolved as a vital technological frontier with paramount significance in the separation and purification of organic solvents. Its implication is particularly prominent in industries such as pharmaceuticals, petrochemicals, and environmental remediation. This comprehensive review, meticulously navigates through the current state of research in OSN membranes, unveiling both the critical challenges and promising opportunities that beckon further exploration. The central focus of this review is on the unique utilization of covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) in OSN membrane design, leveraging their distinctive structural attributes-tunable porosity, robust chemical stability, and molecular sieving capabilities. These qualities position them as exceptional candidates for crafting membranes tailored to the intricacies of organic solvent environments. Our investigation extends into the fundamental principles that render COFs and MOFs adept in OSN applications, dissecting their varied fabrication methods while offering insights into the advantages and limitations of each. Moreover, we address environmental and sustainability considerations in the use of COF and MOF-based OSN membranes. Furthermore, we meticulously present the latest advancements and innovations in this burgeoning field, charting a course toward potential future directions and emerging research areas. By underscoring the challenges awaiting exploration, this review not only provides a panoramic view of the current OSN landscape but also lays the groundwork for the evolution of efficient and sustainable OSN technologies, specifically harnessing the unique attributes of COFs and MOFs.

Covalent Organic Frameworks: Opportunities for Rational Materials Design in Cancer Therapy

AbstractNanomedicines are extensively used in cancer therapy. Covalent organic frameworks (COFs) are crystalline organic porous materials with several benefits for cancer therapy, including porosity, design flexibility, functionalizability, and biocompatibility. This review examines the use of COFs in cancer therapy from the perspective of reticular chemistry and function‐oriented materials design. First, the modification sites and functionalization methods of COFs are discussed, followed by their potential as multifunctional nanoplatforms for tumor targeting, imaging, and therapy by integrating functional components. Finally, some challenges in the clinical translation of COFs are presented with the hope of promoting the development of COF‐based anticancer nanomedicines and bringing COFs closer to clinical trials.

Covalent Organic Frameworks: Opportunities for Rational Materials Design in Cancer Therapy.

Nanomedicines are extensively used in cancer therapy. Covalent organic frameworks (COFs) are crystalline organic porous materials with several benefits for cancer therapy, including porosity, design flexibility, functionalizability, and biocompatibility. This review examines the use of COFs in cancer therapy from the perspective of reticular chemistry and function-oriented materials design. First, the modification sites and functionalization methods of COFs are discussed, followed by their potential as multifunctional nanoplatforms for tumor targeting, imaging, and therapy by integrating functional components. Finally, some challenges in the clinical translation of COFs are presented with the hope of promoting the development of COF-based anticancer nanomedicines and bringing COFs closer to clinical trials.

Covalent organic frameworks as catalyst support: A case study of thermal, hydrothermal, and mechanical pressure stability of β-ketoenamine-linked TpBD-Me2

Covalent organic frameworks (COFs) are crystalline, ordered networks, that, due to their high surface areas and the opportunity for periodic placement of catalytically active sites, are interesting materials for catalysis. Despite the great interest in the use of COFs for this application, there is currently a lack of fundamental understanding on how catalytically relevant conditions affect the integrity of the materials. To gain insight into the stability of COFs as catalyst supports, we herein subjected a β-ketoenamine-linked COF to thermal treatment at high temperatures, to autogenous pressure in water at different temperatures, and to mechanical pressure during pelletizing, after which the materials were thoroughly characterized to gain insight into the structural changes occurring during these catalytically relevant treatments. The COF was largely stable under all hydrothermal conditions studied, highlighting the applicability of β-ketoenamine-linked COFs under aqueous and vapor conditions. On the other hand, thermal and pressure treatments led to a rapid decline in the surface area already at the lowest temperatures and pressures studied. Theoretical calculations indicated this loss to stem from interlayer rearrangement or buckling of the COF layers induced by the applied conditions. This study demonstrates the suitability of β-ketoenamine-linked COFs for use under hydrothermal conditions, and sheds light on the degradation pathways under thermal and pressure treatments, opening the path to the design of COFs with increased stability under such conditions.

A review on covalent organic frameworks for rechargeable zinc-ion batteries

In recent years, rechargeable zinc-ion batteries (ZIBs) are considered to be a promising alternative to lithium-ion batteries owing to their high safety and theoretical capacity with low cost. Nevertheless, the in-depth development of rechargeable zinc-ion batteries is restricted by a sequence of issues, such as the dissolution and structure collapse of cathode materials, the formation of by-products, severe anode corrosion, passivation, and the growth of zinc dendrites. The covalent organic frameworks (COFs) can solve the above problems to a certain extent owing to their ideal characteristics, such as rigid structure, insolubility, high porosity, and abundant active sites. COFs, as advanced materials for ZIBs, have attracted researchers’ attention. In this review, we systematically summarized the synthesis methods of COFs and discussed the application of several advanced characterization technologies in COFs, which would provide a reference for the in-depth research of COFs. In addition, we elucidated the use of COFs as cathode materials and anode protective layers in rechargeable ZIBs. Finally, we discussed the challenges and solutions in the development of COF materials, which would provide constructive insights into the future direction of COFs.

Flexible all-organic nanocomposite films interlayered with in situ synthesized covalent organic frameworks for electrostatic energy storage

Poly(vinylidene fluoride)-based terpolymers, known for having the largest dielectric constant among the existing dielectric polymers, are attractive materials for electrostatic film capacitors used in lightweight electrification systems. However, the potential of these terpolymers in film capacitor applications remains constrained by their low electrical insulating and mechanical strengths. To address these limitations, we introduced rigid covalent organic framework (COF) nanospheres into the thin films of soft terpolymers via in situ synthesis and a facile layer-by-layer solution casting method, whereby multilayer films consisting of two polymer outer layers and a COF-containing middle layer were readily obtained. The resultant all-organic thin films exhibit simultaneously high dielectric constant, enhanced breakdown strength, superior energy density (∼25 J cm–3) at efficiencies over 80%, along with greatly improved mechanical self-supporting capability and excellent mechanical flexibility. This work demonstrates the unprecedented use of COF for electrostatic energy storage, uncovering its potential for flexible electronic applications operating under high electric fields.

Recent Advances in the Use of Covalent Organic Frameworks as Heterogenous Photocatalysts in Organic Synthesis.

Organic photochemistryisintensely developed in the 1980s, in which the nature of excited electronic states and the energy and electron transfer processes arethoroughly studied and finally well-understood. This knowledge from molecular organic photochemistry can be transferred to the design of covalent organic frameworks (COFs) as active visible-light photocatalysts. COFs constitute a new class of crystalline porous materials with substantial application potentials. Featured with outstanding structural tunability, large porosity, high surface area, excellent stability, and unique photoelectronic properties, COFs are studied as potential candidates in various research areas (e.g., photocatalysis). This review aims to provide the state-of-the-art insights into the design of COF photocatalysts (pristine, functionalized, and hybrid COFs) for organic transformations. The catalytic reaction mechanism of COF-based photocatalysts and the influence of dimensionality and crystallinity on heterogenous photocatalysis performance are also discussed, followed by perspectives and prospects on the main challenges and opportunities in future research of COFs and COF-based photocatalysts.

Covalent Organic Frameworks for Atmospheric Water Harvesting

Atmospheric water harvesting using reticular materials is an innovation that has the potential to change the world. Using covalent organic frameworks (COFs) for capturing water holds great promise because COFs are metal-free, stable under working conditions, and their structure can be intentionally designed to meet the requirements for this application. To promote the chemistry and use of COFs for atmospheric water harvesting, important features for synthesizing suitable water-harvesting COFs are discussed. The achievements of using COFs as water harvesters are then highlighted, showing how the water harvesting properties are related to the structural design. Finally, perspectives and research directions for further studies in COF chemistry are provided.

Engineering Covalent Organic Frameworks as Heterogeneous Photocatalysts for Organic Transformations.

Covalent organic frameworks (COFs) are an emerging category of organic polymers with highly porous crystalline structures. In the last decade, reports on the use of COFs as heterogeneous photocatalysts for organic transformations have shown significant progress. Still, comprehensive reviews on the mechanisms of the photocatalytic organic transformations using COFs are lacking. This Review provides a comprehensive and systematic overview of COF-based photocatalysts for organic transformations. Firstly, we discuss the photophysical properties and the characterization methods of COF-based photocatalysts. Then, the general photocatalytic mechanism, the advantages, and the strategies to improve the photocatalytic efficiency of COF-based photocatalysts are summarized. After that, advanced examples of COF-based photocatalysts for organic transformations are analyzed with regard to the underlying mechanisms. The Review ends with a critical perspective on the challenges and prospects.

Effect of Covalent Organic Frameworks Containing Different Groups on Properties of Sulfonated Poly(ether ether ketone) Matrix Proton Exchange Membranes.

The rich −SO3H groups enable sulfonated poly (ether ether ketone) (SPEEK) to possess excellent proton conductivities in proton exchange membrane (PEM), but cause excessive water absorption, resulting in the decline of dimensional stability. It is a challenge to resolve the conflict between conductivity and stability. Owing to its unique structural designability, covalent organic frameworks (COFs) have been used to regulate the performances of PEMs. The authors propose the use of COFs with acidic and basic groups for meeting the requirements of proton conductivity and dimensional stability. Herein, COFs containing different groups (sulfoacid, pyridine, and both) were uniformly dispersed into the SPEEK matrix by in situ synthesis, and the effects on the properties of SPEEK matrix PEMs were revealed. The sulfoacid group significantly improves proton conductivities. At 60 °C, under 95% RH, the conductivity of the SPEEK/TpPa−SO3H-20 composite membrane was 443.6 mS·cm−1, which was 3.3 times that of the pristine SPEEK membrane. The pyridine group reduced the swelling ratio at 50 °C from 220.7% to 2.4%, indicating an enhancement in dimensional stability. Combining the benefits of sulfoacid and pyridine groups, SPEEK/TpPa−(SO3H-Py) composite membrane has a conductivity of 360.3 mS·cm−1 at 60 °C and 95% RH, which is 1.86 times that of SPEEK, and its swelling ratio is 11.8%, about 1/20 of that of SPEEK membrane. The method of in situ combination and regulation of groups open up a way for the development of SPEEK/COFs composite PEMs.

Covalent Organic Framework (COF): A Drug and Carrier to Attenuate Retinal Ganglion Cells Death in an Acute Glaucoma Mouse Model

Purpose: We aim to investigate the use of covalent organic framework (COF) nanoparticles in the local treatment of glaucoma, both as a means of protecting retinal ganglion cells (RGCs), and as a carrier for delayed release of the medication rapamycin following a single intravitreal injection. Methods: a water-dispersible COF, and a COF-based nanoplatform for rapamycin release (COF-Rapa) was constructed. C57BL/6J mice were randomly divided into four groups: intravitreal injection of 1.5 µL normal saline (NS), COF (0.67 ng/µL), rapamycin (300 µM) or COF-Rapa (0.67 ng/µL-300 µM), respectively. The ischemia–reperfusion (I/R) model was established to mimic high intraocular pressure (IOP)-induced retinal injury in glaucoma. Labeling of RGCs by Fluoro-Gold and retinal electroretinogram were used to evaluate retinal function. Immunohistochemistry and Western blotting analyses of retinas were performed. Results: COF nanoparticles were delivered in vitro and in vivo. Six weeks after the COF injection, the number of RGCs was unaffected. In addition, the number of RBPMS-positive RGCs, GFAP-positive astrocytes and Iba1-positive microglia did not differ from the normal control. COF could effectively reduce RGCs death, improve phototransduction function and alleviate the overactivation of microglia compared to NS control after retinal I/R injury. Within six weeks, the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway in the retinas could be inhibited by a single intravitreal injection of COF-Rapa. Compared with single COF administration, COF-Rapa significantly reduced the inflammatory reaction after retinal I/R injury. Conclusions: COF may act as both an RGC protection agent and a carrier for prolonged rapamycin release. This research may lead to the development of novel RGC protection agents and drug delivery techniques, as well as the creation of multifunctional COF-based biomaterials for glaucoma retinopathy.

Amidoxime-functionalized covalent organic framework as simultaneous luminescent sensor and adsorbent for organic arsenic from water

Organoarsenic compounds are widely used as feed additives in the poultry industry. However, the release of organoarsenic-containing wastewater can cause serious poisoning to the ecosystem. For this reason, detection and adsorption of organic arsenic from wastewater is crucial but also very challenging. Here, the use of covalent organic frameworks (COFs) as fluorescence sensors and adsorbents for the detection and adsorption of organic arsenic from water has been investigated for the first time. Two isoreticular crystalline and highly porous sp2 carbon-conjugated COFs were synthesized, and amidoxime-functionalized via post-synthetic modification (PSM). The long-range order and π-conjugated system ensure that both COFs act as fluorescent sensors for detecting the representative organic arsenic, roxarsone (ROX). The fluorescence quenching efficiencies of ROX on both COFs are over 98%. The limits of detection (LOD) for ROX by both COFs are estimated to be 6.5 and 12.3 nM. Additionally, the regular pores and the abundantly decorated amidoxime moiety exhibit extraordinary accessibility, which facilitates the adsorption of ROX. High adsorption capacities were obtained for both materials which amounts are up to 732 and 787 mg g−1. After five times of recycling, a negligible decrease in the adsorption capacity was noted, which reveals the excellent regeneration ability of those two amidoxime-functionalized COFs. These results indicate that the state-of-the-art sp2 carbon-conjugated amidoxime-functionalized COFs exhibit a high potential for the practical detection and adsorption of organoarsenic compounds from wastewater.

Cationic Covalent Organic Framework as an Ion Exchange Material for Efficient Adsorptive Separation of Biomolecules.

Although covalent organic frameworks (COFs) have earned significant interest in separation applications, the use of COFs in biomolecule separation remains unexplored. We examined the ionic COF Py-BPy2+-COF as an ion exchange material for biomolecule separation. After characterizing the properties of the synthesized COF with a variety of techniques, binding experiments with both large and small biomolecules were performed. High adsorption capacities of amino acids with different hydrophobicity and charge, as well as proteins of different isoelectric points and molecular weights, were determined in batch equilibrium experiments. Desorption experiments with mixtures of model proteins demonstrated an ability to successfully separate one protein from another with the selectivity hypothesized to be a combination of the isoelectric point, hydrophobicity, and ability to penetrate the crystalline material. Overall, the results demonstrated that Py-BPy2+-COF can be exploited as a robust crystalline anion exchange biomolecule separation material.

Photocatalytic Oxidation Reactions Mediated by Covalent Organic Frameworks and Related Extended Organic Materials

Covalent Organic Frameworks (COFs) and related extended organic materials have been widely used as photocatalysts in the last few years. Such interest arises from the wide range of covalent linkages employed in their construction, which offer many possibilities to design extended frameworks and to link photoactive building blocks. Thus, the potential utility of predesigned organic photoactive fragments can be synergistically added to the inherent advantages of heterogeneous catalysis, such as recyclability and easy separation of catalyst. In this overview, the current state of the art on the design of organic materials for photocatalytic oxidation reactions will be presented. The designing process of these materials is usually conditioned by the generally accepted concept that crystallinity and porosity defines the quality of the heterogeneous catalysts obtained. The care for the structural integrity of materials obtained is understandable because many properties and applications are intimately related to these features. However, the catalytic activity does not always directly depends on these characteristics. A critical compilation of the available literature is performed in order to offer a general perspective of the use of COFs and Covalent Triazine Frameworks (CTFs) in photocatalytic oxidation processes, including water oxidation, which constitute an important outcome relevant to artificial photosynthesis.

A Perspective on the Application of Covalent Organic Frameworks for Detection and Water Treatment.

Global population growth and water resource scarcity are significant social problems currently being studied by many researchers focusing on finding new materials for water treatment. The aim is to obtain quality water suitable for drinking and industrial consumption. In this sense, an emergent class of crystalline porous materials known as Covalent-Organic Frameworks (COFs) offers a wide range of possibilities since their structures can be designed on demand for specific applications. Indeed, in the last decade, many efforts have been made for their use in water treatment. This perspective article aims to overview the state-of-the-art COFs collecting the most recent results in the field for water detection of pollutants and water treatment. After the introduction, where we overview the classical design strategies on COF design and synthesis for obtaining chemically stable COFs, we summarize the different experimental methodologies used for COFs processing in the form of supported and free-standing membranes and colloids. Finally, we describe the use of COFs in processes involving the detection of pollutants in water and wastewater treatment, such as the capture of organic compounds, heavy metals, and dyes, the degradation of organic pollutants, as well as in desalination processes. Finally, we provide a perspective on the field and the potential technological use of these novel materials.

Macroscopic Ultralight Aerogel Monoliths of Imine‐based Covalent Organic Frameworks

AbstractThe use of covalent organic frameworks (COFs) in practical applications demands shaping them into macroscopic objects, which remains challenging. Herein, we report a simple three‐step method to produce COF aerogels, based on sol‐gel transition, solvent‐exchange, and supercritical CO2 drying, in which 2D imine‐based COF sheets link together to form hierarchical porous structures. The resultant COF aerogel monoliths have extremely low densities (ca. 0.02 g cm−3), high porosity (total porosity values of ca. 99 %), and mechanically behave as elastic materials under a moderate strain (<25–35 %) but become plastic under greater strain. Moreover, these COF aerogels maintain the micro‐ and meso‐porosity of their constituent COFs, and show excellent absorption capacity (e.g. toluene uptake: 32 g g−1), with high removal efficiency (ca. 99 %). The same three‐step method can be used to create functional composites of these COF aerogels with nanomaterials.

Macroscopic Ultralight Aerogel Monoliths of Imine-based Covalent Organic Frameworks.

The use of covalent organic frameworks (COFs) in practical applications demands shaping them into macroscopic objects, which remains challenging. Herein, we report a simple three-step method to produce COF aerogels, based on sol-gel transition, solvent-exchange, and supercritical CO2 drying, in which 2D imine-based COF sheets link together to form hierarchical porous structures. The resultant COF aerogel monoliths have extremely low densities (ca. 0.02 g cm-3 ), high porosity (total porosity values of ca. 99 %), and mechanically behave as elastic materials under a moderate strain (<25-35 %) but become plastic under greater strain. Moreover, these COF aerogels maintain the micro- and meso-porosity of their constituent COFs, and show excellent absorption capacity (e.g. toluene uptake: 32 g g-1 ), with high removal efficiency (ca. 99 %). The same three-step method can be used to create functional composites of these COF aerogels with nanomaterials.

Structural Characteristics and Environmental Applications of Covalent Organic Frameworks

Covalent organic frameworks (COFs) are emerging crystalline polymeric materials with highly ordered intrinsic and uniform pores. Their synthesis involves reticular chemistry, which offers the freedom of choosing building precursors from a large bank with distinct geometries and functionalities. The pore sizes of COFs, as well as their geometry and functionalities, can be pre-designed, giving them an immense opportunity in various fields. In this mini-review, we will focus on the use of COFs in the removal of environmentally hazardous metal ions and chemicals through adsorption and separation. The review will introduce basic aspects of COFs and their advantages over other purification materials. Various fabrication strategies of COFs will be introduced in relation to the separation field. Finally, the challenges of COFs and their future perspectives in this field will be briefly outlined.

Study on the efficiency of a covalent organic framework as adsorbent for the screening of pharmaceuticals in estuary waters

Herein, we demonstrate, for the first time, that covalent organic frameworks (COFs) can be efficient adsorbents for the screening of pharmaceuticals in real water samples, obtaining highly representative data on their occurrence and avoiding the cost of carrying high volume samples and tedious and costly clean-up and preconcentration steps. Of the 23 pharmaceuticals found present in the water samples from the Tagus river estuary using state-of-the-art solid-phase extraction (SPE), 22 were also detected (adsorbed and recovered for analysis) using a COF as the adsorbent material with adsorption efficiency of over 80% for nearly all compounds. In specific cases, acidification of the water samples was identified to lead to a dramatic loss of adsorption efficiency, underlining the effect of sample pre-treatment on the results. The COF efficiently adsorbed (>80%) 19 pharmaceuticals without acid treatment of the sample, highlighting the potential of this class of materials for representative in situ passive adsorption of pharmaceuticals, making this material suitable for being used in water monitoring programs as a simple and cost-efficient sample preparation procedure. In the case of α-hydroxyalprazolam and diclofenac, the COF outperformed the SPE procedure in the recovery efficiency. Although further efforts should be made in tailoring the desorption of the pharmaceuticals from the COF by using different solvents or solvent mixtures, we propose COFs as convenient adsorbent for broad-scope screening and as an efficient adsorbent material to target specific classes of pharmaceuticals. To the best of our knowledge, this is the first study on the use of COFs for contaminant screening in real, naturally contaminated water samples.