General Route to High Surface Area Covalent Organic Frameworks and Their Metal Oxide Composites as Magnetically Recoverable Adsorbents and for Energy Storage

Interpenetrated Donor-Acceptor Heterojunctions in 2D Conjugated Dibenzo[g,p]chrysene-Based Kagome Covalent Organic Frameworks

Dibenzo[g,p]chrysene can be viewed as a constrained propeller-shaped tetraphenylethylene with reduced curvature and has been utilized to construct dual-pore kagome covalent organic frameworks (COFs) with tightly packed two-dimensional (2D) layers owing to its rigid and more planar structural characteristics. Here, we introduce 2D COFs based on the node 4,4',4″,4‴-(dibenzo[g,p]chrysene-2,7,10,15-tetraphenyl)tetraamine (DBCTPTA) featuring extended conjugation compared to the dibenzo[g,p]chrysene-3,6,11,14-tetraamine (DBCTA) node. We establish two exceptionally crystalline imine-linked 2D COFs with a hexagonal dual-pore kagome structure based on the DBCTPTA core. The newly synthesized thienothiophene (TT) and benzodithiophene (BDT)-based DBCTPTA COFs show a tight stacking behavior between adjacent layers. Furthermore, we obtained an unprecedented, interpenetrated electron-donor/acceptor host-guest system with an electron-donating BDT DBCTPTA COF synthesized in situ with the soluble fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) serving as molecular acceptor. The BDT DBCTPTA COF@PCBM film shows a much shorter amplitude-averaged PL lifetime of 7 ± 2 ps compared to 30 ± 4 ps of the BDT DBCTPTA COF film, indicating the light-induced charge transfer process. The successful in situ formation of interpenetrated donor-acceptor heterojunctions within 2D COFs offers a promising strategy for establishing D-A heterojunctions in diverse framework materials with open channel systems.

Generalized Model for Inhibitor-Modulated 2D Polymer Growth to Understand the Controlled Synthesis of Covalent Organic Frameworks

Two-dimensional (2D) polymers, also known as 2D covalent organic frameworks (COFs), are increasingly finding use in applications such as membrane separations, catalysis, and energy conversion. Current research is focused on the development of new synthesis routes for COFs and obtaining a mechanistic understanding of the growth process to control it in a better manner. In this regard, synthesis methods such as reversible polycondensation termination use monofunctional inhibitor species to achieve a controlled growth rate for COFs. However, so far, the role of the inhibitors in modulating the kinetics of COF growth is inadequately understood. In this work, inspired by the Mayo-Lewis framework, we develop a generalized kinetic model to describe the synthesis of a 2D COF monolayer. Our model involves six parameters corresponding to the rate constants of attachment and detachment of monomer and inhibitor species, as well as enhancement factors that quantify the effect of the local coordination environment of the attaching/detaching species on the reaction kinetics. We measure the inhibitor concentration-dependent growth kinetics of the COF experimentally and fit our model to experimental yield data, with the same parameters working across multiple inhibitor concentrations. As the growth process is inherently stochastic, we use this knowledge to develop a comprehensive kinetic Monte Carlo (KMC) simulation of 2D COF synthesis, demonstrating that scaled rate constants are required in the inherently local KMC simulations rather than those obtained from the global kinetic model. The KMC simulations point to an inverse flake size-inhibitor concentration relationship, in agreement with experiments, indicating that flake sizes could be precisely regulated by changing the inhibitor concentrations. Overall, our work promises to improve the understanding of 2D COF synthesis and will help in controlling the growth process to obtain the desired flake size distribution and product morphology.

Magnetic Covalent Organic Frameworks-Fundamentals and Applications in Analytical Chemistry

Magnetic covalent organic frameworks are new emerging materials which, besides many other applications, have found unique applications in analytical chemistry as separating media and adsorbents. They have outstanding features such as special morphology, chemical and thermal stability, high adsorption capacity, good magnetic response, high specific surface area, uniform pore size distribution, strong π-π interactions with analytes and high reusability that makes reported studies on their properties and applications increased in the recent years. After discussing the methods of synthesis of MCOFs with different geometries that cause their special physic-chemical properties, this review focuses on their high potential which has been exhibited in various applications in extraction and pre-concentration of different analytes such as organic compounds, heavy metal ions and biological samples. The article also highlights the applications of magnetic covalent organic frameworks in other chemical analysis such as adsorbent and being used in sensors.

Covalent Organic Frameworks Meet Titanium Oxide

In order to expand the applicability of materials and improve their performance, the combined use of different materials has increasingly been explored. Among these materials, inorganic-organic hybrid materials often exhibit properties superior to those of single materials. Covalent organic frameworks (COFs) are famous crystalline porous materials constructed by organic building blocks linked by covalent bonds. In recent years, the combination of COFs with other materials has shown interesting properties in diverse fields, and the composite materials of COFs and TiO2 have been investigated more and more. These two outstanding materials are combined through covalent bonding, physical mixing, and other methods and exhibit excellent performance in various fields, including photocatalysis, electrocatalysis, sensors, separation, and energy storage and conversion. In this Review, the current preparation methods and applications of COF-TiO2 hybrid materials are introduced in detail, and their future development and possible problems are discussed and prospected, which is of great significance for related research. It is believed that these interesting hybrid materials will show greater application value as research progresses.

Constructing ordered and tunable extrinsic porosity in covalent organic frameworks via water-mediated soft-template strategy

As one of the most attractive methods for the synthesis of ordered hierarchically porous crystalline materials, the soft-template method has not appeared in covalent organic frameworks (COFs) due to the incompatibility of surfactant self-assembly and guided crystallization process of COF precursors in the organic phase. Herein, we connect the soft templates to the COF backbone through ionic bonds, avoiding their crystallization incompatibilities, thus introducing an additional ordered arrangement of soft templates into the anionic microporous COFs. The ion exchange method is used to remove the templates while maintaining the high crystallinity of COFs, resulting in the construction of COFs with ordered hierarchically micropores/mesopores, herein named OHMMCOFs (OHMMCOF-1 and OHMMCOF-2). OHMMCOFs exhibit significantly enhanced functional group accessibility and faster mass transfer rate. The extrinsic porosity can be adjusted by changing the template length, concentration, and ratio. Cationic guanidine-based COFs (OHMMCOF-3) are also constructed using the same method, which verifies the scalability of the soft-template strategy. This work provides a path for constructing ordered and tunable extrinsic porosity in COFs with greatly improved mass transfer efficiency and functional group accessibility.

Progress and Perspectives on Promising Covalent-Organic Frameworks (COFs) Materials for Energy Storage Capacity

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

Efficient adsorption of organic pollutants phthalates and bisphenol A (BPA) utilizing magnetite functionalized covalent organic frameworks (MCOFs): A promising future material for industrial applications

The utilization of phthalates and bisphenol A (BPA) as the major component in plastic and its derivative industry has raised concerns among the public due to the harmful effects caused by these organic pollutants. These pollutants are found to exhibit unique physicochemical properties that allow the pollutants to have prolonged existence in the environment, thus causing damage to the environment. Since phthalates and bisphenol A are used in a variety of industrial applications, the industry must recover these compounds from its water before releasing the pollutants into the environment. As a result, these materials have a promising future in industrial applications. Therefore, the discovery of new quick and reliable abatement technologies is important to ensure that these organic pollutants can be detected and removed from the water sources. This review highlights the use of the adsorption method to remove phthalates and BPA from water sources by employing novel modified adsorbent magnetite functionalized covalent organic frameworks (MCOFs). MCOFs is a new class of porous materials that have demonstrated promising features in a variety of applications due to their adaptable structures, significant surface areas, configurable porosity, and customizable chemistry. The structural attributes, functional design strategies, and specialized for environmental applications before offering some closing thoughts and suggestions for further research were discussed in this paper in addition to developing an innovative solution for the industry to the accessibility for clean water.

Exploration of the Performance and Mechanism of Uranium Adsorption by a Covalent Organic Framework Possessing the Thiazole Structure

This study prepared an active 2-D covalent organic skeleton (HDU-27) with a network structure, high crystallinity, considerable specific surface area, excellent pore structure, and excellent stability. Kinetic studies manifested that HDU-27 could effectively capture uranium as monolayer chemisorption within a very short kinetic equilibrium time (10 min). In particular, the temperature significantly and positively impacted the uranium adsorption performance of HDU-27. At 298, 313, and 328 K, the adsorption capacity reached 269.2, 488.8, and 576.2 mg g-1, respectively, suggesting the potential to treat high-temperature industrial wastewater containing uranium. HDU-27 had high stability and recoverability with an adsorption efficiency of 98.5% after five adsorption-desorption cycles. According to X-ray photoelectron spectroscopy, the mechanism of interaction between U(VI) and HDU-27 was mainly the chelation of UO22+ by the N atom in the thiazole structure and the strong coordination of the O atom in the keto structure with UO22+. More excitingly, HDU-27 could chemically reduce soluble U(VI) to insoluble U(IV) and release binding sites for the adsorption of additional U(VI). In conclusion, HDU-27 has outstanding potential for uranium adsorption from industrial wastewater containing uranium.

Mesoporous NiO/Ni2O3 nanoflowers for favorable visible light photocatalytic degradation of 4-chlorophenol

The present study highlights the treatment of industrial effluent, which is one of the most life-threatening factors. Herein, for the first time, two types of NiO (green and black) photocatalysts were prepared by facile chemical precipitation and thermal decomposition methods separately. The synthesized NiO materials were demonstrated with various instrumental techniques for finding their characteristics. The X-ray diffraction studies (XRD) and X-ray photoelectron spectroscopy (XPS) revealed the presence of Ni2O3 in black NiO material. The transmission electron microscopic (TEM) images engrained the nanospherical shaped green NiO and nanoflower shaped black NiO/Ni2O3 materials. Further, the band gap of black NiO nanoflower was 2.9 eV compared to green NiO having 3.8 eV obtained from UV-vis spectroscopy. Meanwhile, both NiO catalysts were employed for visible light degradation, which yields a 60.3% efficiency of black NiO comparable to a 4.3% efficiency of green NiO within 180 min of exposure. The higher degrading efficiency of black NiO was due to the presence of Ni2O3 and the development of pores, which was evident from the Barrett-Joyner-Halenda (BJH) method. Type IV hysteresis was observed in black NiO nanoflowers with high surface area and pore size measurements. This black NiO/Ni2O3 synthesized from the thermal decomposition method has promoted better photocatalytic degradation of 4-chlorophenol upon exposure to visible light and is applicable for other industrial pollutants.

Novel Biocompatible Trianglamine Networks for Efficient Iodine Capture

Herein, we report for the first time a biocompatible cross-linked trianglamine (Δ) network for the efficient iodine removal from the vapor phase, water, and seawater. In the vapor phase, the cross-linked network could capture 6 g g-1 of iodine, ranking among the most performant materials for iodine vapor capture. In the liquid phase, this cross-linked network is also capable of capturing iodine at high rates from aqueous media (water and seawater). This network displayed fast adsorption kinetics, and they are fully recyclable. This study reveals the high affinity of iodine for the intrinsic cavity of the trianglamine. The synthesized materials are extremely interesting since they are environmentally friendly and inexpensive and the synthesis could easily be scaled up to be used as the material of choice in response to accidents in the nuclear industry.

Magnetic Covalent Organic Framework Composites for Wastewater Remediation

Covalent organic frameworks (COFs) with high specific surface area, tailored structure, easy functionalization, and excellent chemical stability have been extensively exploited as fantastic materials in various fields. However, in most cases, COFs prepared in powder form suffer from the disadvantages of tedious operation, strong tendency to agglomerate, and poor recyclability, greatly limiting their practical application in environmental remediation. To tackle these issues, the fabrication of magnetic COFs (MCOFs) has attracted tremendous attention. In this review, several reliable strategies for the fabrication of MCOFs are summarized. In addition, the recent application of MCOFs as outstanding adsorbents for the removal of contaminants including toxic metal ions, dyes, pharmaceuticals and personal care products, and other organic pollutants is discussed. Moreover, in-depth discussions regarding the structural parameters affecting the practical potential of MCOFs are highlighted in detail. Finally, the current challenges and future prospects of MCOFs in this field are provided with the expectation to boost their practical application.

Recent advances in covalent organic frameworks (COFs) for wound healing and antimicrobial applications

Covalent organic frameworks (COFs) are crystal-like organic structures such as cartography buildings prepared from appropriately pre-designed construction block precursors. Moreover, after the expansion of the first COF in 2005, numerous researchers have been developing different materials for versatile applications such as sensing/imaging, cancer theranostics, drug delivery, tissue engineering, wound healing, and antimicrobials. COFs have harmonious pore size, enduring porosity, thermal stability, and low density. In addition, a wide variety of functional groups could be implanted during their construction to provide desired constituents, including antibodies and enzymes. The reticular organic frameworks comprising porous hybrid materials connected via a covalent bond have been studied for improving wound healing and dressing applications due to their long-standing antibacterial properties. Several COF-based systems have been planned for controlled drug delivery with wound healing purposes, targeting drugs to efficiently inhibit the growth of pathogenic microorganisms at the wound spot. In addition, COFs can be deployed for combinational therapy using photodynamic and photothermal antibacterial therapy along with drug delivery for healing chronic wounds and bacterial infections. Herein, the most recent advancements pertaining to the applications of COF-based systems against bacterial infections and for wound healing are considered, concentrating on challenges and future guidelines.

Plasmonic Hybrid Nanostructures in Photocatalysis: Structures, Mechanisms, and Applications

(Sun)Light is an abundantly available sustainable source of energy that has been used in catalyzing chemical reactions for several decades now. In particular, studies related to the interaction of light with plasmonic nanostructures have been receiving increased attention. These structures display the unique property of localized surface plasmon resonance, which converts light of a specific wavelength range into hot charge carriers, along with strong local electromagnetic fields, and/or heat, which may all enhance the reaction efficiency in their own way. These unique properties of plasmonic nanoparticles can be conveniently tuned by varying the metal type, size, shape, and dielectric environment, thus prompting a research focus on rationally designed plasmonic hybrid nanostructures. In this review, the term "hybrid" implies nanomaterials that consist of multiple plasmonic or non-plasmonic materials, forming complex configurations in the geometry and/or at the atomic level. We discuss the synthetic techniques and evolution of such hybrid plasmonic nanostructures giving rise to a wide variety of material and geometric configurations. Bimetallic alloys, which result in a new set of opto-physical parameters, are compared with core-shell configurations. For the latter, the use of metal, semiconductor, and polymer shells is reviewed. Also, more complex structures such as Janus and antenna reactor composites are discussed. This review further summarizes the studies exploiting plasmonic hybrids to elucidate the plasmonic-photocatalytic mechanism. Finally, we review the implementation of these plasmonic hybrids in different photocatalytic application domains such as H₂ generation, CO₂ reduction, water purification, air purification, and disinfection.

Macroscale Conjugated Microporous Polymers: Controlling Versatile Functionalities Over Several Dimensions

Since discovered in 2007, conjugated microporous polymers (CMPs) have been developed for numerous applications including gas adsorption, sensing, organic and photoredox catalysis, energy storage, etc. While featuring abundant micropores, the structural rigidity derived from CMPs' stable π-conjugated skeleton leads to insolubility and thus poor processability, which severely limits their applicability, e.g., in CMP-based devices. Hence, the development of CMPs whose structure can not only be controlled on the micro- but also on the macroscale have attracted tremendous interest. In conventional synthesis procedures, CMPs are obtained as powders, but in recent years various bottom-up synthesis strategies have been developed, which yield CMPs as thin films on substrates or as hybrid materials, allowing to span length scales from individual conjugated monomers to micro-/macrostructures. This review surveys recent advances on the construction of CMPs into macroscale structures, including membranes, films, aerogels, sponges, and other architectures. The focus is to describe the underlying fabrication techniques and the implications which follow from the macroscale morphologies, involving new chemistry and physics in such materials for applications like molecular separation/filtration/adsorption, energy storage and conversion, photothermal transformation, sensing, or catalysis.

Covalent organic framework-based porous materials for harmful gas purification

Covalent organic frameworks (COFs) with 2D or 3D networks are a class of novel porous crystalline materials, and have attracted more and more attention in the field of gas purification owing to their attractive physicochemical properties, such as high surface area, adjustable functionality and structure, low density, and high stability. However, few systematic reviews about the application statuses of COFs in gas purification are available, especially about non-CO₂ harmful gases. In this review, the recent progress of COFs about the capture, catalysis, and detection of common harmful gases (such as CO₂, NO_x, SO₂, H₂S, NH₃ and volatile pollutants) were comprehensively discussed. The design strategies of COF functional materials from porosity adjustment to surface functionalization (including bottom-up approach, post-synthetic approach, and blending with other materials) for certain application were summarized in detail. Furthermore, the faced challenges and future research directions of COFs in the harmful gas treatment were clearly proposed to inspire the development of COFs.

Heterostructure Fe2O3 nanorods@imine-based covalent organic framework for long cycling and high-rate lithium storage

Fe₂O₃ as an anode for lithium-ion batteries has attracted intense attention because of its high theoretical capacity, natural abundance, and good safety. However, the inferior cycling stability, low-rate performance, and limited composite varieties hinder the application of Fe₂O₃-based materials. In this work, an Fe₂O₃@COF-LZU1 (FO@LZU1) anode was prepared via an imine-based covalent organic framework (COF-LZU1) covering on the exterior surface of Fe₂O₃ after rational optimization. With its unique heterostructure, the COF-LZU1 layer not only effectively alleviated the volume expansion during cycling but also improved the charge-transfer capability because of the π-conjugated system. Moreover, the organic functional group (CN, benzene ring) for COF-LZU1 provided more redox-active sites for Li⁺ storage. Under the contributions of both Fe₂O₃ nanorods and COF-LZU1, the FO@LZU1_50% exhibited an ultrahigh initial capacity and long-term cycling performance with initial discharge capacities of 2143 and 2171 mA h g^-1 after 300 cycles under 0.1 A g^-1, and rate performance of 1310 and 501 mA h g^-1 at 0.3 and 3 A g^-1, respectively. In addition, a high retention capacity of 1185 mA h g^-1 was achieved at 1 A g^-1 after 500 cycles. Furthermore, a full-cell with the FO@LZU1_50% anode and LiCoO₂ cathode exhibited superior cycling and rate performance, which still maintained a reversible capacity of 260 mA h g^-1 after 200 cycles even at a current density of 1 A g^-1. The proposed strategy offers a new perspective for exploring the high-rate capability and designability of Fe₂O₃-based electrode materials.

Adsorptive remediation of environmental pollutants using magnetic hybrid materials as platform adsorbents

Effective separation and remediation of environmentally hazardous pollutants are burning areas of research because of a constant increase in environmental pollution problems. An extensive number of emerging contaminants in the environmental matrices result in serious health consequences in animals, humans, and plants, even at trace levels. Therefore, it is of paramount significance to quantify these undesirable pollutants, even at a very low concentration, from the natural environment. Magnetic solid-phase extraction (MSPE) has recently achieved huge attention because of its strong magnetic domain and easy separation through an external magnetic field compared with simple solid-phase extraction. Therefore, MSPE appeared the most promising technique for removing and pre-concentration of emerging pollutants at trace level. Compared to the normal solid-phase extraction, MSPE as magnetic hybrid adsorbents offers the unique advantages of distinct nanomaterials and magnetic hybrid materials. It can exhibit efficient dispersion and rapid recycling when applying to a very complex matrix. This review highlights the possible environmental applications of magnetic hybrid nanoscale materials as effective MSPE sorbents to remediate a diverse range of environmentally toxic pollutants. We believe this study tends to evoke a variety of research thrust that may lead to novel remediation approaches in the forthcoming years.

Covalent Organic Framework (COF)-Based Hybrids for Electrocatalysis: Recent Advances and Perspectives

Developing highly efficient electrocatalysts for renewable energy conversion and environment purification has long been a research priority in the past 15 years. Covalent organic frameworks (COFs) have emerged as a burgeoning family of organic materials internally connected by covalent bonds and have been explored as promising candidates in electrocatalysis. The reticular geometry of COFs can provide an excellent platform for precise incorporation of the active sites in the framework, and the fine-tuning hierarchical porous architectures can enable efficient accessibility of the active sites and mass transportation. Considerable advances are made in rational design and controllable fabrication of COF-based organic-inorganic hybrids, that containing organic frameworks and inorganic electroactive species to induce novel physicochemical properties, and take advantage of the synergistic effect for targeted electrocatalysis with the hybrid system. Branches of COF-based hybrids containing a diversity form of metals, metal compounds, as well as metal-free carbons have come to the fore as highly promising electrocatalysts. This review aims to provide a systematic and profound understanding of the design principles behind the COF-based hybrids for electrocatalysis applications. Particularly, the structure-activity relationship and the synergistic effects in the COF-based hybrid systems are discussed to shed some light on the future design of next-generation electrocatalysts.

Two-Dimensional Polymers and Polymerizations

Synthetic chemists have developed robust methods to synthesize discrete molecules, linear and branched polymers, and disordered cross-linked networks. However, two-dimensional polymers (2DPs) prepared from designed monomers have been long missing from these capabilities, both as objects of chemical synthesis and in nature. Recently, new polymerization strategies and characterization methods have enabled the unambiguous realization of covalently linked macromolecular sheets. Here we review 2DPs and 2D polymerization methods. Three predominant 2D polymerization strategies have emerged to date, which produce 2DPs either as monolayers or multilayer assemblies. We discuss the fundamental understanding and scope of each of these approaches, including: the bond-forming reactions used, the synthetic diversity of 2DPs prepared, their multilayer stacking behaviors, nanoscale and mesoscale structures, and macroscale morphologies. Additionally, we describe the analytical tools currently available to characterize 2DPs in their various isolated forms. Finally, we review emergent 2DP properties and the potential applications of planar macromolecules. Throughout, we highlight achievements in 2D polymerization and identify opportunities for continued study.

Contiguous layer based metal-organic framework with conjugated π-electron ligand for high iodine capture

Herein, a novel 3-dimensional (3D) Cu(II) metal-organic framework (MOF), [Cu₃(μ₂-O)₂(p-tr₂Ph)₂(HCOO)][NO₃]·3DMF·3H₂O (compound 1), which is constructed by directly interlocking regionalized hollow two-dimensional (2D) layers, has been conceived and solvothermally synthesized. Such a distinctive regionalized pore system effectively maintains the uniformity of the pore structure, isolates the counterions and bridging ligands in the partition layer, and endows compound 1 with high porosity. In consequence, compound 1 exhibits excellent adsorption ability of iodine in cyclohexane. The removal efficiency in cyclohexane solution (0.01 mol L^-1) can reach up to 80% in 8 min, and the absorption ability towards iodine can reach about 1.15 g g^-1. Moreover, iodine can also be controllably released in ethanol. The release rate was up to 4 × 10^-5 mol L^-1 min^-1. Furthermore, compound 1 also showed prominent recyclability due to the high stability, and the maximum sorption amount could be retained after 3 cycles. This study paves a new way towards opening up MOFs' potential application in capturing radioactive iodine to protect the environment.

High iodine uptake in two-dimensional covalent organic frameworks

Two 2-dimensional covalent organic frameworks (COFs; TJNU-203 and TJNU-204) with high crystallinity and large specific surface area are rationally fabricated using a three-connected distorted building block and linear linkers. The two COFs show high iodine uptake (5.885 g g-1 for TJNU-203 and 5.335 g g-1 for TJNU-204) on account of physical-chemical adsorption, which make them one among the best porous materials for iodine adsorption.

Covalent Organic Framework Composites: Synthesis and Analytical Applications

In the recent years, composite materials containing covalent organic frameworks (COFs) have raised increasing interest for analytical applications. To date, various synthesis techniques have emerged that allow for the preparation of crystalline and porous COF composites with various materials. Herein, we summarize the most common methods used to gain access to crystalline COF composites with magnetic nanoparticles, other oxide materials, graphene and graphene oxide, and metal nanoparticles. Additionally, some examples of stainless steel, polymer, and metal-organic framework composites are presented. Thereafter, we discuss the use of these composites for chromatographic separation, environmental remediation, and sensing.

AgI modified covalent organic frameworks for effective bacterial disinfection and organic pollutant degradation under visible light irradiation

Covalent organic frameworks (COFs) have recently been demonstrated to have great application potentials in water treatment. Their photocatalytic performance towards bacterial disinfection and organic pollutant degradation yet has seldom been investigated. In this study, AgI modified COFs (using 2,5-diaminopyridine and 1,3,5-triformylphloroglucinol as precursors) (COF-PD/AgI) were fabricated and their applications to photocatalytically disinfect bacteria and degrade organic pollutants were investigated. COF-PD/AgI exhibited effective photocatalytic performance towards Escherichia coli disinfection and organic pollutant (Rhodamine B and acetaminophen) degradation. SEM images were employed to investigate cell disinfection process, while theoretical density functional theory (DFT) calculation and intermediates determination were used to elucidate organic pollutant degradation processes. Scavenger experiments, ESR spectra and chemical probes experiments confirmed O₂^-, h⁺ and OH played important roles in the photocatalytic process. The formation of dual-band Z-scheme heterojunction improved photocatalytic performance. COF-PD/AgI remained high photocatalytic activity in the four consecutive cycles and could serve as a promising photocatalyst for water purification.

Fluorescent conjugated microporous polymers containing pyrazine moieties for adsorbing and fluorescent sensing of iodine

Two kinds of fluorescent conjugated microporous polymers containing pyrazine moieties were prepared by the polymerization reaction of 2,5-di-triphenylamine-yl-pyrazine (DTPAPz) and N,N,N',N'-tetrapheny-2,5-(diazyl) pyrazine (TDPz) with 2,4,6-trichloro-1,3,5-triazine (TCT) through Friedel-Crafts reaction using the methanesulfonic acid as a catalysts. Both CMPs have high thermal stability and decomposition temperature reaches above 596 and 248 °C under nitrogen atmosphere, respectively. By right of porous morphology and electron-donating nitrogen, as well as electron-rich π-conjugated structures, the adsorption performance for iodine vapor on the CMPs is very excellent, which can reach 441% and 312%. In addition, fluorescence studies showed that the two CMPs exhibited high fluorescence sensitivity to electron-deficient iodine, o-nitrophenol (o-NP), and picric acid (PA) via fluorescence quenching.

An ionic liquid as a green solvent for high potency synthesis of 2D covalent organic frameworks

The PXRD and simulated profiles of PMDA–TAPA (a) and TFP–EB (b).

Bulk COFs and COF nanosheets for electrochemical energy storage and conversion

The current advances, structure-property relationship and future perspectives in covalent organic frameworks (COFs) and their nanosheets for electrochemical energy storage (EES) and conversion (EEC) are summarized.

Europium Ionic Liquid Grafted Covalent Organic Framework with Dual Luminescence Emissions as Sensitive and Selective Acetone Sensor

Chronical exposure to volatile acetone could damage to the liver and kidney or nerve, and cause inflammation. Design of novel materials for the sensitive and selective detection of acetone is of great importance. We report on a europium (Eu)-containing covalent organic framework (DhaTab-COF-EuIL) synthesized via a Schiff-base reaction between 2,5-dihydroxyterephthalaldehyde (Dha) and 1,3,5-tris(4-aminophenyl)benzene (Tab) followed by an ionic liquid (IL)-modification and then ion displacement. The resulting DhaTab-COF-EuIL is microporous and crystalline, and not only presents unique dual luminescence emissions of Eu³⁺ and COF material, but also exhibits remarkable luminescence quenching toward acetone. Especially, the DhaTab-COF-EuIL could be a novel luminescent sensor, displaying high sensitivity and selectivity for the detection of volatile acetone with a limit of detection down to 1%.

Recyclable magnetic covalent organic framework for the extraction of marine biotoxins

A novel procedure for the preparation of magnetic covalent organic frameworks (COFs) is reported. In situ functionalization of Fe3O4 with dopamine rapidly afforded amino-functionalized magnetic nanoparticles, which after decoration with a COF building block and subsequent COF growth gave access to magnetic composite mTpBD-Me2. The optimized synthesis conditions yielded crystalline and superparamagnetic material with no loss in surface area as compared to bulk COF. The composite material was employed for the first time in magnetic solid-phase extraction of marine biotoxins from seawater with high efficiency, where calculated maximum adsorption capacities of 812 mg g-1 and 830 mg g-1 were found for okadaic acid (OA) and dinophysistoxin-1 (DTX-1), respectively, corresponding to an increase of ∼500-fold for OA and ∼300-fold for DTX-1 as compared to the commonly used non-magnetic macroporous resins. Nearly quantitative desorption efficiency of both biotoxins was obtained using 2-propanol as solvent, rendering the composite materials recyclable with merely minor losses in adsorption capacity after five consecutive cycles of adsorption/desorption. In addition, retention of crystallinity after the adsorption cycles highlights the stability of the composite in seawater. These results illustrate the great efficiency of the novel material in biotoxin adsorption and show great promise for its application in environmental monitoring programs.

Molecular engineering of supercapacitor electrodes with monodispersed N-doped carbon nanoporous spheres

Water phase synthesis of polytriazine nanospheres as the high-nitrogen content carbon spheres precursor for a high-performance EDLC electrode.

Porous Organic Frameworks: Advanced Materials in Analytical Chemistry

Porous organic frameworks (POFs), a general term for covalent-organic frameworks (COFs), covalent triazine frameworks (CTFs), porous aromatic frameworks (PAFs), etc., are constructed from organic building monomers with strong covalent bonds and have generated great interest among researchers. The remarkable features, such as large surface areas, permanent porosity, high thermal and chemical stability, and convenient functionalization, promote the great potential of POFs in diverse applications. A critical overview of the important development in the design and synthesis of COFs, CTFs, and PAFs is provided and their state-of-the-art applications in analytical chemistry are discussed. POFs and their functional composites have been explored as advanced materials in "turn-off" or "turn-on" fluorescence detection and novel stationary phases for chromatographic separation, as well as a promising adsorbent for sample preparation methods. In addition, the prospects for the synthesis and utilization of POFs in analytical chemistry are also presented. These prospects can offer an outlook and reference for further study of the applications of POFs.

Heterogeneous nucleation and growth of highly crystalline imine-linked covalent organic frameworks

A heterogeneous nucleation and growth method is reported to synthesize imine-linked covalent organic frameworks (COFs). Excellent crystallinity and a high surface area are obtained. The introduction of heterogeneous nuclei suppresses the fast precipitation of amorphous structures at the early stage while promoting the crystallization of COFs during the growth process.