Confined Synthesis of Two-Dimensional Covalent Organic Framework Thin Films within Superspreading Water Layer

Rapid Synthesis of Graphdiyne Films on Hydrogel at the Superspreading Interface for Antibacteria

Graphdiyne (GDY), a two-dimensional (2D) carbon material with diacetylenic linkages (-C≡C-C≡C-) structures, has attracted enormous attention in various fields. However, the controlled synthesis of GDY films is still challenging because of the low alkyne coupling efficiency and out-of-plane growth. Here, we employed a highly efficient Cu(II)-N,N,N',N'-tetramethylethylenediamine (Cu(II)-TMEDA) catalyst and constructed a superspreading liquid/liquid interface on a hydrogel for rapid and controllable synthesis of GDY thin films. GDY films with controllable thickness from 4 to 50 nm and large-scale uniform morphology can be prepared within 2 h at room temperature. The mechanism of growth was revealed to be a nucleation and in-plane extension process. Meanwhile, the as-grown GDY films showed excellent photothermal conversion efficiency, which induces the release of Cu(II) ions from the hydrogel and exhibits high efficiency in synergistic antibacteria.

Dispersive 2D Triptycene-Based Crystalline Polymers: Influence of Regioisomerism on Crystallinity and Morphology

The merging of good crystallinity and high dispersibility into two-dimensional (2D) layered crystalline polymers (CPs) still represents a challenge because a high crystallinity is often accompanied by intimate interlayer interactions that are detrimental to the material processibility. We herein report a strategy to address this dilemma using rationally designed three-dimensional (3D) monomers and regioisomerism-based morphology control. The as-synthesized CPs possess layered 2D structures, where the assembly of layers is stabilized by relatively weak van der Waals interactions between C-H bonds other than the usual π-π stackings. The morphology and dispersibility of the CPs are finely tuned via regioisomerism. These findings shed light on how to modulate the crystallinity, morphology, and ultimate function of crystalline polymers using the spatial arrangements of linking groups.

Bioinspired Superspreading Surface: From Essential Mechanism to Application

ConspectusThe dynamic behavior of liquids on surfaces is ubiquitous in nature and has aroused wide attention from researchers. Among them, the superspreading surface has been extensively investigated and applied in areas ranging from film fabrication to antibiofouling, separation, etc. However, the traditional equilibrium contact angle (CA) at the thermodynamic steady-state cannot completely depict the dynamic spreading process of liquids, because the performance of these surfaces is controlled not only by the final steady superhydrophilicity (CA < 5°) but also by the superspreading speed of liquids with a CA of ∼0°. Moreover, as the most basic prerequisite for superspreading, the long-held intrinsic wetting threshold (IWT) of 90°, which divides hydrophobic and hydrophilic surfaces, is also controversial.In this Account, we summarize and condense the commonalities of our related research, further formally propose the concept of "superspreading", and recommend using "superspreading time (ST)" and "curve of superspreading radius versus spreading time (SRST)" to quantify its performance. Learning from nature is the most effective way to artificially fabricate superspreading surfaces. To begin, we first review some typical superspreading surfaces we found in nature and introduce the strategies adopted by the surfaces for surviving or realizing special functions. Then, we systematically review our recent understanding of the essential mechanism of superspreading surfaces across multiple length scales─from the molecular origin of the newly found IWT of ∼65° for water to the macroscopic respective functions of nanostructure and microstructure in superspreading. Armed with the in-depth fundamental mechanism, we propose the designing principle of high-performance superspreading surfaces. Following that, we summarize the commonly utilized methods, including modifying surface composition to give the surface intrinsic hydrophilicity and changing surface structure to improve the superspreading performance. Subsequently, we introduce the recently developed practical applications by virtue of the outstanding property of the superspreading surface, including the fabrication of a self-assembled film on the solid-gas surface and solid-liquid interface, a self-assembled water barrier for antibiofouling and oil repellency, high-efficiency separation and heat dissipation, etc. Finally, we discuss the remaining major challenges and the future development trends in the superspreading field. This Account serves to arouse wide attention and efforts in the superspreading field to strengthen mechanism research and promote practical large-area applications.

Recent advances in the tuning of the organic framework materials - The selections of ligands, reaction conditions, and post-synthesis approaches

Organic framework materials, particularly metal-organic frameworks (MOFs), graphene-organic frameworks (GOFs), and covalent organic frameworks (COFs), have led to the revolution across fields including catalysts, sensors, gas capture, and biology mainly owing to their ultra-high surface area-to-volume ratio, on-demand tunable crystal structures, and unique surface properties. While the wet chemistry routes have been the predominant synthesis approach, the crystal phase, morphological parameters, and physicochemical properties of organic framework materials are largely affected by various synthesis parameters and precursors. In this work, we specifically review the influences of synthesis parameters towards crystal structures and chemical compositions of organic framework materials, including selected ligand types and lengths, reaction temperature/solvent/reactant compositions, as well as post-synthesis modification approaches. More importantly, the subsequent impacts on the general electronic, mechanical, surface chemical, and thermal properties as well as the consequent variation in performances towards catalytic, desalination, gas sensing, and gas storage applications are critically discussed. Finally, the current challenges and prospects of organic framework materials are provided.

Ultrathin Membranes for Separations: A New Era Driven by Advanced Nanotechnology

Ultrathin membranes are at the forefront of membrane research, offering great opportunities in revolutionizing separations with ultrafast transport. Driven by advanced nanomaterials and manufacturing technology, tremendous progresses are made over the last 15 years in the fabrications and applications of sub-50 nm membranes. Here, an overview of state-of-the-art ultrathin membranes is first introduced, followed by a summary of the fabrication techniques with an emphasis on how to realize such extremely low thickness. Then, different types of ultrathin membranes, categorized based on their structures, that is, network, laminar, or framework structures, are discussed with a focus on the interplays among structure, fabrication methods, and separation performances. Recent research and development trends are highlighted. Meanwhile, the performances and applications of current ultrathin membranes for representative separations (gas separation and liquid separation) are thoroughly analyzed and compared. Last, the challenges in material design, structure construction, and coordination are given, in order to fully realize the potential of ultrathin membranes and facilitate the translation from scientific achievements to industrial productions.

Freestanding non-covalent thin films of the propeller-shaped polycyclic aromatic hydrocarbon decacyclene

Molecularly thin, nanoporous thin films are of paramount importance in material sciences. Their use in a wide range of applications requires control over their chemical functionalities, which is difficult to achieve using current production methods. Here, the small polycyclic aromatic hydrocarbon decacyclene is used to form molecular thin films, without requiring covalent crosslinking of any kind. The 2.5 nm thin films are mechanically stable, able to be free-standing over micrometer distances, held together solely by supramolecular interactions. Using a combination of computational chemistry and microscopic imaging techniques, thin films are studied on both a molecular and microscopic scale. Their mechanical strength is quantified using AFM nanoindentation, showing their capability of withstanding a point load of 26 ± 9 nN, when freely spanning over a 1 μm aperture, with a corresponding Young’s modulus of 6 ± 4 GPa. Our thin films constitute free-standing, non-covalent thin films based on a small PAH.

Molecularly thin films are important in material sciences but their use in a wide range of applications requires control over their chemical functionalities, which is difficult to achieve. Here, the authors use decacyclene to form such freestanding and mechanically stable molecular films held together by supramolecular interactions without requiring covalent crosslinking of any kind

Electrocleavage Synthesis of Solution-Processed, Imine-Linked, and Crystalline Covalent Organic Framework Thin Films

Developing a general, facile, and direct strategy for synthesizing thin films of covalent organic frameworks (COFs) is a major challenge in this field. Herein, we report an unprecedented electrocleavage synthesis strategy to produce imine-linked COF films directly on electrodes from electrolyte solutions at room temperature. This strategy enables the cathodic exfoliation of the COF powders to nanosheets by electrochemical reduction and protonation, followed by nanosheets migrating to the anode and reproducing the COF structures by anodic oxidation. Our method is adaptable with most imine-linked COFs by virtue of the low redox potential of the imine bonds, whereas the COF films possess high crystallinity and hierarchical porosity. We highlight these COF films as a superb platform for promoting mass transfer by demonstrating their extraordinarily rapid iodine adsorption with record-high rate constants.

Electrosynthesis of Ionic Covalent Organic Frameworks for Charge-Selective Separation of Molecules

Covalent organic frameworks (COFs) have emerged as potent material platforms for engineering advanced membranes to tackle challenging separation demands. However, the synthesis of COF membranes is currently hampered by suboptimal productivity and harsh synthesis conditions, especially for ionic COFs with perdurable charges. Herein, ionic COFs with charged nanochannels are electrically synthesized on conductive supports to rapidly construct composite membranes for charge-selective separations of small molecules. The intrinsic charging nature and strong charge intensity of ionic COFs are demonstrated to collectively dominate the membrane growth. Spontaneous repairing to diminish defects under the applied electric field is observed, in favor of generating well-grown COF membranes. Altering electrosynthetic conditions realizes the precise control over the membrane thickness and thus the separation ability. Electrically synthesized ionic COF membranes exhibit remarkable molecular separation performances due to their relatively ordered and charged nanochannels. With these charge-selective pathways, the membranes enable the efficient sieving of charged and neutral molecules with analogous structures. This study reveals an electrical route to synthesizing COF thin films, and showcases the great potential of ionic nanochannels in precise separation based on charge selectivity.

2D Covalent Organic Frameworks: From Synthetic Strategies to Advanced Optical-Electrical-Magnetic Functionalities

Covalent organic frameworks (COFs), an emerging class of organic crystalline polymers with highly oriented structures and permanent porosity, can adopt 2D or 3D architectures depending on the different topological diagrams of the monomers. Notably, 2D COFs have particularly gained much attention due to the extraordinary merits of their extended in-plane π-conjugation and topologically ordered columnar π-arrays. These properties together with high crystallinity, large surface area, and tunable porosity distinguish 2D COFs as an ideal candidate for the fabrication of functional materials. Herein, this review surveys the recent research advances in 2D COFs with special emphasis on the preparation of 2D COF powders, single crystals, and thin films, as well as their advanced optical, electrical, and magnetic functionalities. Some challenging issues and potential research outlook for 2D COFs are also provided for promoting their development in terms of structure, synthesis, and functionalities.

Ultralarge Free-Standing Imine-Based Covalent Organic Framework Membranes Fabricated via Compression

Demand continues for processing methods to shape covalent organic frameworks (COFs) into macroscopic objects that are needed for their practical applications. Herein, a simple compression method to prepare large-scale, free-standing homogeneous and porous imine-based COF-membranes with dimensions in the centimeter range and excellent mechanical properties is reported. This method entails the compression of imine-based COF-aerogels, which undergo a morphological change from an elastic to plastic material. The COF-membranes fabricated upon compression show good performances for the separation of gas mixtures of industrial interest, N2 /CO2 and CH4 /CO2 . It is believed that the new procedure paves the way to a broader range of COF-membranes.

A CuS- and BODIPY-loaded nanoscale covalent organic framework for synergetic photodynamic and photothermal therapy

Herein, we report an inorganic photothermal agent, CuS- and an organic photosensitizer, BODIPY-loaded composite nanoscale COF material via a stepwise post-synthetic modification. The obtained CuS@COF-BDP can be a dual-modal therapeutic agent to highly inhibit MCF-7 tumor cell proliferation due to its efficient singlet oxygen generation and photothermal conversion abilities.

Characteristic Synthesis of a Covalent Organic Framework and Its Application in Multifunctional Tumor Therapy

For decades, covalent organic frameworks (COFs) have attracted wide biomedical interest due to their unique properties including ease of synthesis, porosity, and adjustable biocompatibility. Versatile COFs can easily encapsulate various therapeutic drugs due to their extremely high payload and porosity. COFs with abundant functional groups can be surface-modified to achieve active targeting and enhance biocompatibility. In this paper, the latest developments of COFs in the biomedical field are summarized. First, the classification and synthesis of COFs are discussed. Cancer diagnosis and treatment based on COFs are studied, and the advantages and limitations of each method are discussed. Second, the specific preparation methods to obtain specific therapeutic properties are summarized. Finally, based on the combination and modification of COFs with various components, this review system summarizes different combination therapies. In addition, the main challenges faced in COF research and prospects for applying COFs to cancer diagnosis and treatment are evaluated. This review provides enlightening insights into the interdisciplinary research on COFs and applications in biomedicine, which highlight the great expectations for their further clinical transformation.

High-Strength, Microporous, Two-Dimensional Polymer Thin Films with Rigid Benzoxazole Linkage

Two-dimensional (2D) rigid polymers provide an opportunity to translate the high-strength, high-modulus mechanical performance of classic rigid-rod 1D polymers across a plane by extending covalent bonding into two dimensions while simultaneously reducing density due to microporosity by structural design. Thus far, this potential has remained elusive because of the challenge of producing high-quality 2D polymer thin films, particularly those with irreversible, rigid benzazole linkages. Here, we present a facile two-step process that allows the deposition of a uniform intermediate film network via reversible, non-covalent interactions, followed by a subsequent solid-state annealing step that facilitates the irreversible conversion to a 2D covalently bonded polymer product with benzoxazole linkages. We demonstrate the versatility of this synthesis method by producing films with four different aromatic core units. The resulting films show microporosity and anisotropy with a 2D layered structure that can be exfoliated into few-layer nanosheets using a freeze-thaw method. These films have promising mechanical properties with an in-plane ultimate tensile strength of nearly 40 MPa and axial tensile and transverse compressive elastic moduli on the scale of several GPa, rivaling the performance of solution-cast films of 1D polybenzoxazole, as well as several other 1D high-strength polymer films.

Advances and challenges in the development of nanosheet membranes

The development of highly efficient separation membranes utilizing emerging materials with controllable pore size and minimized thickness could greatly enhance the broad applications of membrane-based technologies. Having this perspective, many studies on the incorporation of nanosheets in membrane fabrication have been conducted, and strong interest in this area has grown over the past decade. This article reviews the development of nanosheet membranes focusing on two-dimensional materials as a continuous phase, due to their promising properties, such as atomic or nanoscale thickness and large lateral dimensions, to achieve improved performance compared to their discontinuous counterparts. Material characteristics and strategies to process nanosheet materials into separation membranes are reviewed, followed by discussions on the membrane performances in diverse applications. The review concludes with a discussion of remaining challenges and future outlook for nanosheet membrane technologies.

Emerging Two-Dimensional Covalent and Coordination Polymers for Stable Lithium Metal Batteries: From Liquid to Solid

Lithium metal anodes (LMAs) have attracted much attention in recent years because of their high theoretical capacity (3860 mAh g^-1) and low electrochemical potential (-3.040 V vs standard hydrogen electrode). Lithium metal can be coupled with various cathodes to construct high-energy-density lithium metal batteries (LMBs) which hold great promise for next-generation batteries. However, the unstable solid electrolyte interphases (SEIs) and the uncontrollable lithium dendrite growth severely hinder the commercial development of LMAs. The emerging 2D polymers (2DPs), which possess high mechanical flexibility, high specific surface area, abundant surface chemistry, and rich chemical modification characteristics, have shown great advantages in addressing the inherent issues of LMAs. Herein, the current progress of 2DPs for stable and dendrite-free LMAs in liquid- and solid-based batteries is comprehensively reviewed. Some perspectives for the application of 2DPs in LMBs are also discussed. It is believed that the emerging 2DPs will provide insights into developing high-energy-density LMBs and beyond.

Facile and Site-Selective Synthesis of an Amine-Functionalized Covalent Organic Framework

Amine-functionalized covalent organic frameworks (COFs) hold great potential in diversified applications. However, the synthesis is dominated by postsynthetic modification, while the de novo synthesis allowing for direct installation of amine groups remains a formidable challenge. Herein, we develop a site-selective synthetic strategy for the facile preparation of amine-functionalized hydrazone-linked COF for the first time. A new monomer 2-aminoterephthalohydrazide (NH₂-Th) bearing both amine and hydrazide functionalities is designed to react with benzene-1,3,5-tricarbaldehyde (Bta). Remarkably, the different activity of amine and hydrazide groups toward aldehyde underpin the highly site-selective synthesis of an unprecedented NH₂-Th-Bta COF with abundant free amine groups anchored in the well-defined pore channels. Interestingly, NH₂-Th-Bta COF exhibits dramatically enhanced iodine uptake capacity (3.58 g g^-1) in comparison to that of the nonfunctionalized Th-Bta COF counterpart (0.68 g g^-1), and many reported porous adsorbents, despite its low specific surface area. Moreover, NH₂-Th-Bta COF possesses exceptional cycling capability and retained high iodine uptake, even after six cycles. This work not only provides a simple and straightforward route for the de novo synthesis of amine-functionalized COFs but also uncovers the great potential of amine-functionalized COFs as adsorbents in the efficient removal of radioiodine and beyond.

Ionic Covalent Organic Frameworks for Energy Devices

Covalent organic frameworks (COFs) are a class of porous crystalline materials whose facile preparation, functionality, and modularity have led to their becoming powerful platforms for the development of molecular devices in many fields of (bio)engineering, such as energy storage, environmental remediation, drug delivery, and catalysis. In particular, ionic COFs (iCOFs) are highly useful for constructing energy devices, as their ionic functional groups can transport ions efficiently, and the nonlabile and highly ordered all-covalent pore structures of their backbones provide ideal pathways for long-term ionic transport under harsh electrochemical conditions. Here, current research progress on the use of iCOFs for energy devices, specifically lithium-based batteries and fuel cells, is reviewed in terms of iCOF backbone-design strategies, synthetic approaches, properties, engineering techniques, and applications. iCOFs are categorized as anionic COFs or cationic COFs, and how each of these types of iCOFs transport lithium ions, protons, or hydroxides is illustrated. Finally, the current challenges to and future opportunities for the utilization of iCOFs in energy devices are described. This review will therefore serve as a useful reference on state-of-the-art iCOF design and application strategies focusing on energy devices.

Controllable Synthesis and Performance Modulation of 2D Covalent-Organic Frameworks

Covalent-organic frameworks (COFs) are especially interesting and unique as their highly ordered topological structures entirely built from plentiful π-conjugated units through covalent bonds. Arranging tailorable organic building blocks into periodically reticular skeleton bestows predictable lattices and various properties upon COFs in respect of topology diagrams, pore size, properties of channel wall interfaces, etc. Indeed, these peculiar features in terms of crystallinity, conjugation degree, and topology diagrams fundamentally decide the applications of COFs including heterogeneous catalysis, energy conversion, proton conduction, light emission, and optoelectronic devices. Additionally, this research field has attracted widespread attention and is of importance with a major breakthrough in recent year. However, this research field is running with the lack of summaries about tailorable construction of 2D COFs for targeted functionalities. This review first covers some crucial polymeric strategies of preparing COFs, containing boron ester condensation, amine-aldehyde condensation, Knoevenagel condensation, trimerization reaction, Suzuki CC coupling reaction, and hybrid polycondensation. Subsequently, a summary is made of some representative building blocks, and then underlines how the electronic and molecular structures of building blocks can strongly influence the functional performance of COFs. Finally, conclusion and perspectives on 2D COFs for further study are proposed.

A Dually Charged Membrane for Seawater Utilization: Combining Marine Pollution Remediation and Desalination by Simultaneous Removal of Polluted Dispersed Oil, Surfactants, and Ions

Shortage of freshwater and deterioration of the marine environment have a serious effect on the human body and ecological environment. Here, we demonstrated a facile way to prepare a multiple-target superwetting porous material to obtain available water without cumbersome steps. Through the facile immersion and hydrothermal method, a charge-enhanced membrane material combining superwettability, electrostatic interaction, and the steric effect is prepared. Such a material breaks through the limitations of single size sieving and has a universal effect on different kinds of contaminants with accurate wettability manipulation and fluid separation control. The protonation and deprotonation of active carboxyl groups at the novel created solid/liquid interface facilitate the surface wettability and flux transition, which will bring out superior continuous separation and surface lubrication control.

Applications of covalent organic frameworks and their composites in the extraction of pesticides from different samples

Pesticides are used extensively in a wide range of applications and due to their high rate of consumption, they are ubiquitous in the different media and samples like environment, water sources, air, soil, biological materials, wastes (liquids, solids or sludges), vegetables and fruits, where they can persist for long periods. Pesticides often have hazardous side effects and can cause a range of harmful diseases like Parkinson, Alzheimer, asthma, depression and anxiety, cancer, etc, even at low concentrations. To this end, extraction, pre-concentration and determination of pesticides from various samples presents significant challenges caused by sample complexity and the low concentrations of them in many samples. Often, direct extraction and determination of pesticides are impossible due to their low concentrations and the complexity of samples. The main goals of sample preparation are removing interfering species, pre-concentrating target analyte/s and converting the analytes into more stable forms (when needed). The most popular approach is solid-phase extraction due to its simplicity, efficiency, ease of operation and low cost. This method is based on using a wide variety of materials, among which covalent organic frameworks (COFs) can be identified as an emerging class of highly versatile materials exhibiting advantageous properties, such as a porous and crystalline structure, pre-designable structure, high physical and chemical stability, ease of modification, high surface area and high adsorption capacity. The present review will cover recent developments in synthesis and applications of COFs and their composites for extraction of pesticides, different synthesis approaches of COFs, possible mechanisms for interaction of COFs-based adsorbents with pesticides and finally, future prospects and challenges in the fabrication and utilization of COFs and their composites for extraction of pesticides.

De Novo Fabrication of Large-Area and Self-Standing Covalent Organic Framework Films for Efficient Separation

Covalent organic frameworks (COFs) have aroused extensive attention from various fields owing to their numerous advantages, including permanent porosity, high crystallinity, strong robustness, and well-ordered channels. However, the poor processability of the crystallite powder has greatly impeded their further utilization in many advanced devices and frontier areas. In this work, we fabricate a series of COF films using an interfacial polymerization strategy at a liquid-liquid interface under ambient conditions. The as-synthesized freestanding films are continuous, flexible, and defect-free and have large areas of up to 4 × 6 cm². In addition, the pore sizes of these COF films can be well controlled based on the principle of reticular chemistry. These films exhibit high chemical stability even in acidic and basic aqueous solutions. More significantly, the highly robust COF films can serve as a nanofiltration membrane for efficient separation of pollutant molecules with different dimensions. These films show high selectivity for the separation of mixed molecule feed and excellent recyclability without a significant loss in the rejection rate.

Covalent Organic Frameworks and Their Derivatives for Better Metal Anodes in Rechargeable Batteries

Metal anodes based on a plating/stripping electrochemistry such as metallic Li, Na, K, Zn, Ca, Mg, Fe, and Al are recognized as promising anode materials for constructing next-generation high-energy-density rechargeable metal batteries owing to their low electrochemical potential, high theoretical specific capacity, superior electronic conductivity, etc. However, inherent issues such as high chemical reactivity, severe growth of dendrites, huge volume changes, and unstable interface largely impede their practical application. Covalent organic frameworks (COFs) and their derivatives as emerging multifunctional materials have already well addressed the inherent issues of metal anodes in the past several years due to their abundant metallophilic functional groups, special inner channels, and controllable structures. COFs and their derivatives can solve the issues of metal anodes by interfacial modification, homogenizing ion flux, acting as nucleation seeds, reducing the corrosion of metal anodes, and so on. Nevertheless, related reviews are still absent. Here we present a detailed review of multifunctional COFs and their derivatives in metal anodes for rechargeable metal batteries. Meanwhile, some outlooks and opinions are put forward. We believe the review can catch the eyes of relevant researchers and supply some inspiration for future research.

The Ionic Liquid-H2O Interface: A New Platform for the Synthesis of Highly Crystalline and Molecular Sieving Covalent Organic Framework Membranes

Covalent organic frameworks (COFs) are highly porous crystalline polymers with uniform pores and large surface areas. Combined with their modular design principle and excellent properties, COFs are an ideal candidate for separation membranes. Liquid-liquid interfacial polymerization is a well-known approach to synthesize membranes by reacting two monomers at the interface. However, volatile organic solvents are usually used, which may disturb the liquid-liquid interface and affect the COF membrane crystallinity due to solvent evaporation. Simultaneously, the domain size of the organic solvent-water interface, named the reaction zone, can hardly be regulated, and the diffusion control of monomers for favorable crystallinity is only achieved in the water phase. These drawbacks may limit the widespread applications of liquid-liquid interfacial polymerization to synthesize diverse COF membranes with different functionalities. Here, we report a facile strategy to synthesize a series of imine-linked freestanding COF membranes with different thicknesses and morphologies at tunable ionic liquid (IL)-H₂O interfaces. Due to the H-bonding of the catalysts with amine monomers and the high viscosity of the ILs, the diffusion of the monomers was simultaneously controlled in water and in ILs. This resulted in the exceptionally high crystallinity of freestanding COF membranes with a Brunauer-Emmett-Teller (BET) surface area up to 4.3 times of that synthesized at a dichloromethane-H₂O interface. By varying the alkyl chain length of cations in the ILs, the interfacial region size and interfacial tension could be regulated to further improve the crystallinity of the COF membranes. As a result, the as-fabricated COF membranes exhibited ultrahigh permeance toward water and organic solvents and excellent selective rejection of dyes.

A covalent organic framework-based nanoagent for H2S-activable phototherapy against colon cancer

Herin, we report a Cu(ii)-porphyrin-derived nanoscale COF, which can be triggered by endogenous H₂S via an intracellular sulfidation reaction to generate a metal-free COF-photosensitizer for PDT against H₂S-enriched colon tumors with controllable singlet oxygen release; meanwhile in situ generated CuS can be synchronously used as a photothermal agent for PTT.

Arylamine-Linked 2D Covalent Organic Frameworks for Efficient Pseudocapacitive Energy Storage

The development of new linkages is one of the most efficient strategies to enrich the diversity of covalent organic frameworks (COFs). Particularly, functional linkages can endow COFs with additional tailored properties besides the building units, which further diversify COFs with desirable functions. Herein, we have developed a new arylamine linkage for the construction of COFs. Two new arylamine-linked COFs (AAm-TPB and AAm-Py) were prepared by condensing cost-effective dimethyl succinyl succinate (DMSS) with corresponding multitopic amines (TPB-NH₂ and Py-NH₂ ). Due to the abundant electroactive diphenylamine moieties in the COF skeletons resembling that of polyaniline (PANI), a state-of-the-art conductive polymer, the pseudocapacitive energy storage performance of AAm-TPB was further investigated. Remarkably, the AAm-TPB electrode exhibits a high capacitance of 271 F g^-1 with a three-electrode setup at a discharge rate of 1 A g^-1 , which represents one of the highest capacitances among the reported COF-based electrode materials.

Recent Advances on Conductive 2D Covalent Organic Frameworks

As a burgeoning family of crystalline porous copolymers, covalent organic frameworks (COFs) allow precise atomic insertion of organic components in the topology construction to form periodic networks and ordered nanopores. Their 2D networks bear great similarities to graphene analogs, and therefore are essential additions to the 2D family. Here, the electronic properties of conductive 2D-COFs are reviewed and their bonding strategies and structural characteristics are examined in detail. The controlling approaches toward the morphologies of conductive 2D-COFs are further explored, followed by a discussion of their applications in field-effect transistors, photodetectors, sensors, catalysis, and energy storage. Finally, research challenges and forthcoming developments are projected. The resulting survey reveals that the extended porous 2D organic networks with conductive properties will provide great opportunities and essential innovations in various electronics and energy-related fields.

Surface-Mediated Construction of an Ultrathin Free-Standing Covalent Organic Framework Membrane for Efficient Proton Conduction

As a new class of crystalline porous organic materials, covalent organic frameworks (COFs) have attracted considerable attention for proton conduction owing to their regular channels and tailored functionality. However, most COFs are insoluble and unprocessable, which makes membrane preparation for practical use a challenge. In this study, we used surface-initiated condensation polymerization of a trialdehyde and a phenylenediamine for the synthesis of sulfonic COF (SCOF) coatings. The COF layer thickness could be finely tuned from 10 to 100 nm by controlling the polymerization time. Moreover, free-standing COF membranes were obtained by sacrificing the bridging layer without any decomposition of the COF structure. Benefiting from the abundant sulfonic acid groups in the COF channels, the proton conductivity of the SCOF membrane reached 0.54 S cm^-1 at 80 °C in pure water. To our knowledge, this is one of the highest values for a pristine COF membrane in the absence of additional additives.