Electrochemiluminescence enhanced by molecular engineering linear π-conjugated polymer: An ingenious ECL emitter for the construction of exosome sensing platform

Linear π-conjugated polymers (LCPs) with π-electron conjugation system have many remarkable optical characteristics such as fluorescence and electrochemiluminescence (ECL). However, the extremely strong interchain interaction and π-π stacking limit the luminescence efficiency. In this work, 1H-1,2,4-triazole-3,5-diamine was chosen as the polymer monomer and reacted with terephthalaldehyde via simple Schiff base condensation to synthesize LCPs. Subsequently, molecular engineering strategy was adopted to construct zirconium-based LCPs (MLCPs), which not only prevented π-π stacking but also ensured that extended π-coupling was maintained in the LCPs, thus effectively promoting charge transport and achieving strong luminescence. Second, the coreactant polyethyleneimine (PEI) was assembled onto the MLCPs (MLCPs@PEI) to further promote the emission of ECL. To further explore the potential of the obtained MLCPs@PEI as emerging ECL emitter, colorectal cancer exosome was chosen as model biomarker, and an innovative ECL ratiometric system based on MLCPs@PEI and luminol was designed to improve the validity and accuracy of the sensors. This research provides a fresh nanoplatform for exosome detection and broadens the application of LCPs in ECL immunoassay.

All-visible-light-driven salicylidene schiff-base-functionalized artificial molecular motors

Light-driven rotary molecular motors are among the most promising classes of responsive molecular machines and take advantage of their intrinsic chirality which governs unidirectional rotation. As a consequence of their dynamic function, they receive considerable interest in the areas of supramolecular chemistry, asymmetric catalysis and responsive materials. Among the emerging classes of responsive photochromic molecules, multistate first-generation molecular motors driven by benign visible light remain unexplored, which limits the exploitation of the full potential of these mechanical light-powered systems. Herein, we describe a series of all-visible-light-driven first-generation molecular motors based on the salicylidene Schiff base functionality. Remarkable redshifts up to 100 nm in absorption are achieved compared to conventional first-generation motor structures. Taking advantage of all-visible-light-driven multistate motor scaffolds, adaptive behaviour is found as well, and potential application in multistate photoluminescence is demonstrated. These functional visible-light-responsive motors will likely stimulate the design and synthesis of more sophisticated nanomachinery with a myriad of future applications in powering dynamic systems.

Hydrazone-Linked Covalent Organic Frameworks

Hydrazone-linked covalent organic frameworks (COFs) with structural flexibility, heteroatomic sites, post-modification ability and high hydrolytic stability have attracted great attention from scientific community. Hydrazone-linked COFs, as a subclass of Schiff-base COFs, was firstly reported in 2011 by Yaghi's group and later witnessed prosperous development in various aspects. Their adjustable structures, precise pore channels and plentiful heteroatomic sites of hydrazone-linked structures possess much potential in diverse applications, for example, adsorption/separation, chemical sensing, catalysis and energy storage, etc. Up to date, the systematic reviews about the reported hydrazone-linked COFs are still rare. Therefore, in this review, we will summarize their preparation methods, characteristics and related applications, and discuss the opportunity or challenge of hydrazone-linked COFs. We hope this review could provide new insights about hydrazone-linked COFs for exploring more appealing functions or applications.

Construction of Porous Aromatic Frameworks with Specifically Designed Motifs for Charge Storage and Transport

ConspectusPorous frameworks possess high porosity and adjustable functions. The two features conjointly create sufficient interfaces for matter exchange and energy transfer within the skeletons. For crystalline porous frameworks, including metal organic frameworks (MOFs) and covalent organic frameworks (COFs), their long-range ordered structures indeed play an important role in managing versatile physicochemical behaviors such as electron transfer or band gap engineering. It is now feasible to predict their functions based on the unveiled structures and structure-performance relationships. In contrast, porous organic frameworks (POFs) represent a member of the porous solid family with no long-range regularity. For the case of POFs, the randomly packed building units and their disordered connections hinder the electronic structural consistency throughout the entire networks. However, many investigations have demonstrated that the functions of POFs could also be designed and originated from their local motifs.In this Account, we will first provide an overview of the design and synthesis principles for porous aromatic frameworks (PAFs), which are a typical family of POFs with high porosity and exceptional stability. Specifically, the functions achieved by the specific design and synthesis of in-framework motifs will be demonstrated. This strategy is particularly intuitive to introduce desired functions to PAFs, owing to the exceptional tolerance of PAFs to harsh chemical treatments and synthetic conditions. The local structures can be either obtained by selecting suitable building units, sometimes with the aid of computational screening, or emerge as the product of coupling reactions during the synthetic process. Radical PAFs can be obtained by incorporating a persistent radical molecule as a building unit, and the rigid and porous framework may facilitate the formation of radical species by trapping spins in the organic network, which could avoid the delocalizing and recombining processes. Alternatively, radical motifs can also be formed during the formation of the framework linkages. The coupling reaction plays an important role in the construction of functional motifs like diacetylene. The highly porous, radical PAFs showed significant performance as anodes of lithium-ion batteries. To improve the charge transport within the framework, the building units and their connecting manner were cohesively considered, and the framework with a fully conjugated backbone was built up. In another case, the explicit product of the cross-coupling reaction ensured the precise assembly of two building units with electron donating and accepting abilities; therefore, the moving direction of photogenerated electrons was rationally controlled. Constructing a fully conjugated backbone or rationally designing a D-A system for charge transfer in porous frameworks introduced exciting properties for photovoltaic and photocatalysis, and their highly porous, stable frameworks improved their functional applications for perovskite solar cells and chemical productions. These investigations shed light on the designable combination of intrinsic functional motifs with highly porous organic frameworks for effective energy storage and conversion.

Designing Heterocyclic Covalent Organic Frameworks with Tunable Electronic Structures for Efficient Electrosynthesis of Hydrogen Peroxide

The electrocatalytic production of hydrogen peroxide (H2O2) through the two-electron oxygen reduction reaction (2e- ORR) has garnered significant research attention in recent years due to its numerous appealing advantages, such as being eco-friendly and exhibiting high energy conversion efficiency. Metal-free carbon materials with specific catalytic sites have been recognized as potential electrocatalysts for 2e- ORR; however, the design of highly efficient catalysts with well-defined structures and long-term stability for large-scale H2O2 production remains unsatisfactory. In this study, three covalent organic frameworks (COFs) - imine-linked LZU-1, oxazole-linked LZU-190, and thiazole-linked LZU-190(S), are successfully synthesized to explore their catalytic activity in electrocatalytic H2O2 production. Among these, the carbon sites LZU-190(S) are predominantly activated by the introduced adjacent heteroatoms via electronic effects, resulting in much higher H2O2 selectivity compared to the oxazole and imine linkages. This work provides new insights into developing COFs-based electrocatalysts for efficient H2O2 generation.

The development of catalysts and auxiliaries for the synthesis of covalent organic frameworks

Covalent organic frameworks (COFs) have recently seen significant advancements. Large quantities of structurally & functionally oriented COFs with a wide range of applications, such as gas adsorption, catalysis, separation, and drug delivery, have been explored. Recent achievements in this field are primarily focused on advancing synthetic methodologies, with catalysts playing a crucial role in achieving highly crystalline COF materials, particularly those featuring novel linkages and chemistry. A series of reviews have already been published over the last decade, covering the fundamentals, synthesis, and applications of COFs. However, despite the pivotal role that catalysts and auxiliaries play in forming COF materials and adjusting their properties (e.g., crystallinity, porosity, stability, and morphology), limited attention has been devoted to these essential components. In this Critical Review, we mainly focus on the state-of-the-art progress of catalysts and auxiliaries applied to the synthesis of COFs. The catalysts include four categories: acid catalysts, base catalysts, transition-metal catalysts, and other catalysts. The auxiliaries, such as modulators, oxygen, and surfactants, are discussed as well. This is then followed by the description of several specific applications derived from the utilization of catalysts and auxiliaries. Lastly, a perspective on the major challenges and opportunities associated with catalysts and auxiliaries is provided.

Analysis of COF-300 synthesis: probing degradation processes and 3D electron diffraction structure

Although COF-300 is often used as an example to study the synthesis and structure of (3D) covalent organic frameworks (COFs), knowledge of the underlying synthetic processes is still fragmented. Here, an optimized synthetic procedure based on a combination of linker protection and modulation was applied. Using this approach, the influence of time and temperature on the synthesis of COF-300 was studied. Synthesis times that were too short produced materials with limited crystallinity and porosity, lacking the typical pore flexibility associated with COF-300. On the other hand, synthesis times that were too long could be characterized by loss of crystallinity and pore order by degradation of the tetrakis(4-aminophenyl)methane (TAM) linker used. The presence of the degradation product was confirmed by visual inspection, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). As TAM is by far the most popular linker for the synthesis of 3D COFs, this degradation process might be one of the reasons why the development of 3D COFs is still lagging compared with 2D COFs. However, COF crystals obtained via an optimized procedure could be structurally probed using 3D electron diffraction (3DED). The 3DED analysis resulted in a full structure determination of COF-300 at atomic resolution with satisfying data parameters. Comparison of our 3DED-derived structural model with previously reported single-crystal X-ray diffraction data for this material, as well as parameters derived from the Cambridge Structural Database, demonstrates the high accuracy of the 3DED method for structure determination. This validation might accelerate the exploitation of 3DED as a structure determination technique for COFs and other porous materials.

Modulation of fluorescence and phosphorescence of organoboron compounds from ortho-substituted phenolic Schiff bases by structural modification

Light emission from organoboron compounds of Schiff bases is found to depend strongly on their chemical structure. Two of these compounds (OB1 and OB2), which contain a benzene ring between the Schiff base moieties, exhibit weak fluorescence in methanol, with marked viscosity dependence. Fluorescence lifetimes of these compounds are in picosecond timescale, as determined by femtosecond optical gating (FOG). A significant enhancement in fluorescence intensity and lifetime is observed at 77 K, indicating the operation of an activated nonradiative process. Using fluorescence lifetime imaging microscopy (FLIM), OB1 and OB2 are shown to be potential membrane probes. The third (OB3), which is devoid of this benzene ring, exhibits relatively stronger fluorescence with nanosecond lifetimes at room temperature. No viscosity dependence is observed in this case. The emission spectrum at 77 K is markedly more intense and exhibits an additional red shifted structured feature, which persists for a few seconds. Hence, OB3 seems to have greater promise not only as fluorescent probe but also for light harvesting. The marked improvement of the light emission properties of OB3 compared with OB1 and OB2 is likely to serve as a pointer for the design of Schiff base-derived organoboron luminophores with diverse potential applications.

An Appraisal for Providing Charge Transfer (CT) Through Synthetic Porous Frameworks for their Semiconductor Applications

In recent years, there has been considerable focus on the development of charge transfer (CT) complex formation as a means to modify the band gaps of organic materials. In particular, CT complexes alternate layers of aromatic molecules with donor (D) and acceptor (A) properties to provide inherent electrical conductivity. In particular, the synthetic porous frameworks as attractive D-A components have been extensively studied in recent years in comparison to existing D-A materials. Therefore, in this work, the synthetic porous frameworks are classified into conjugated microporous polymers (CMPs), covalent organic frameworks (COFs), and metal-organic frameworks (MOFs) and compare high-quality materials for CT in semiconductors. This work updates the overview of the above porous frameworks for CT, starting with their early history regarding their semiconductor applications, and lists CT concepts and selected key developments in their CT complexes and CT composites. In addition, the network formation methods and their functionalization are discussed to provide access to a variety of potential applications. Furthermore, several theoretical investigations, efficiency improvement techniques, and a discussion of the electrical conductivity of the porous frameworks are also highlighted. Finally, a perspective of synthetic porous framework studies on CT performance is provided along with some comparisons.

Modular Construction of Vinylene-Linked Covalent Organic Frameworks with Tunable Emission for Tumor Visualization

Covalent organic frameworks (COFs) with ordered π structures are very promising in porous light-emitting materials. However, most of these COFs are either poor in luminescence or lack of water-stability. Herein, a series of isostructural D-A vinylene-linked COFs were constructed based a new D2h symmetric linker 1,4-bis(4,6-dimethyl-1,3,5-triazin-2-yl)benzene (TMTA) with high crystallinity, comparative high surface area and excellent chemical/thermal stability. Impressively, their adsorption and luminescence wavelength vary with respect to the density of π-systems in the electron-donating group, which constitute the foundation for molecular engineering the luminescent properties of vinylene-linked COFs. The DFT calculations further established the relationship between the luminescence properties and the donor electronic structure. Moreover, one of representative COF named FZU-203 showed inspiring applications in bioimaging, which may further provide strategic guidance for the use of vinylene-linked COFs as fluorescent nanoprobes in non-invasive medical diagnosis and visualization therapy of tumors.

Functional Covalent Organic Frameworks' Microspheres Synthesized by Self-Limited Dynamic Linker Exchange for Stationary Phases

Synthesizing uniform functional covalent organic framework (COF) microspheres is the prerequisite of applying COFs as novel stationary phases for liquid chromatography. However, the synthesis of functionalized COF microspheres is challenging due to the difficulty in maintaining microspheric morphology when conferring functions. Here, a facile and universal "self-limited dynamic linker exchange" strategy is developed to achieve surface functionalization of uniform COF microspheres. Six different types of COF microspheres are constructed, showing the universality and superiority of the strategy. The library of COF microspheres' stationary phases can be further enriched on demand by varying different functional building blocks. The "self-limited dynamic linker exchange" is attributed to the result of a delicate balance of reaction thermodynamics and molecular diffusion energy barrier. As a demonstration, the chiral functional COF microspheres are used as stationary phases of chiral chromatography and realized effective enantioseparation.

Photocatalytic functionalization of thin-layer membranes using a monomer truncation strategy

We present the design and synthesis of two new organic polymer films making use of a liquid-liquid interfacial amine-acid chloride polymerization strategy. One of them was additionally functionalized in situ by the anchoring of N-phenyl-phenothiazine through a monomer truncation strategy, which endowed it with photocatalytic activity. This photoactive film displays interesting luminescence phenomena that were used for the oxidation of a variety of sulphides to their corresponding sulfoxides and reduction of aryl bromines.

Early stages of covalent organic framework formation imaged in operando

Covalent organic frameworks (COFs) are a functional material class able to harness, convert and store energy. However, after almost 20 years of research, there are no coherent prediction rules for their synthesis conditions. This is partly because of an incomplete picture of nucleation and growth at the early stages of formation. Here we use the optical technique interferometric scattering microscopy (iSCAT)1-3 for in operando studies of COF polymerization and framework formation. We observe liquid-liquid phase separation, pointing to the existence of structured solvents in the form of surfactant-free (micro)emulsions in conventional COF synthesis. Our findings show that the role of solvents extends beyond solubility to being kinetic modulators by compartmentation of reactants and catalyst. Taking advantage of these observations, we develop a synthesis protocol for COFs using room temperature instead of elevated temperatures. This work connects framework synthesis with liquid phase diagrams and thereby enables an active design of the reaction environment, emphasizing that visualization of chemical reactions by means of light-scattering-based techniques can be a powerful approach for advancing rational materials synthesis.

Rational Design of Organic Electrocatalysts for Hydrogen and Oxygen Electrocatalytic Applications

Efficient electrocatalysts are pivotal for advancing green energy conversion technologies. Organic electrocatalysts, as cost-effective alternatives to noble-metal benchmarks, have garnered attention. However, the understanding of the relationships between their properties and electrocatalytic activities remains ambiguous. Plenty of research articles regarding low-cost organic electrocatalysts started to gain momentum in 2010 and have been flourishing recently though, a review article for both entry-level and experienced researchers in this field is still lacking. This review underscores the urgent need to elucidate the structure-activity relationship and design suitable electrode structures, leveraging the unique features of organic electrocatalysts like controllability and compatibility for real-world applications. Organic electrocatalysts are classified into four groups: small molecules, oligomers, polymers, and frameworks, with specific structural and physicochemical properties serving as activity indicators. To unlock the full potential of organic electrocatalysts, five strategies are discussed: integrated structures, surface property modulation, membrane technologies, electrolyte affinity regulation, and addition of anticorrosion species, all aimed at enhancing charge efficiency, mass transfer, and long-term stability during electrocatalytic reactions. The review offers a comprehensive overview of the current state of organic electrocatalysts and their practical applications, bridging the understanding gap and paving the way for future developments of more efficient green energy conversion technologies.

Core-Shell Gold Nanoparticles@Pd-Loaded Covalent Organic Framework for In Situ Surface-Enhanced Raman Spectroscopy Monitoring of Catalytic Reactions

A core-shell nanostructure of gold nanoparticles@covalent organic framework (COF) loaded with palladium nanoparticles (AuNPs@COF-PdNPs) was designed for the rapid monitoring of catalytic reactions with surface-enhanced Raman spectroscopy (SERS). The nanostructure was prepared by coating the COF layer on AuNPs and then in situ synthesizing PdNPs within the COF shell. With the respective SERS activity and catalytic performance of the AuNP core and COF-PdNPs shell, the nanostructure can be directly used in the SERS study of the catalytic reaction processes. It was shown that the confinement effect of COF resulted in the high dispersity of PdNPs and outstanding catalytic activity of AuNPs@COF-PdNPs, thus improving the reaction rate constant of the AuNPs@COF-PdNPs-catalyzed hydrogenation reduction by 10 times higher than that obtained with Au/Pd NPs. In addition, the COF layer can serve as a protective shell to make AuNPs@COF-PdNPs possess excellent reusability. Moreover, the loading of PdNPs within the COF layer was found to be in favor of avoiding intermediate products to achieve a high total conversion rate. AuNPs@COF-PdNPs also showed great catalytic activities toward the Suzuki-Miyaura coupling reaction. Taken together, the proposed core-shell nanostructure has great potential in monitoring and exploring catalytic processes and interfacial reactions.

Deciphering the factors influencing electric field mediated polymerization and depolymerization at the solution-solid interface

Strong and oriented electric fields are known to influence structure as well as reactivity. The strong electric field (EF) between the tip of a scanning tunneling microscope (STM) and graphite has been used to modulate two-dimensional (2D) polymerization of aryl boronic acids where switching the polarity of the substrate bias enabled reversible transition between self-assembled molecular networks of monomers and crystalline 2D polymer (2DP) domains. Here, we untangle the different factors influencing the EF-mediated (de)polymerization of a boroxine-based 2DP on graphite. The influence of the solvent was systematically studied by varying the nature from polar protic to polar aprotic to non-polar. The effect of monomer concentration was also investigated in detail with a special focus on the time-dependence of the transition. Our experimental observations indicate that while the nucleation of 2DP domains is not initiated by the applied electric field, their depolymerization and subsequent desorption, are a consequence of the change in the polarity of the substrate bias within the area scanned by the STM tip. We conclude that the reversible transition is intimately linked to the bias-induced adsorption and desorption of the monomers, which, in turn, could drive changes in the local concentration of the monomers.

Turning Non-Emissive Schiff Bases Into Aggregate Emitters

Schiff bases are a crucial component in various functional materials but often exhibit non-emissive behavior which significantly limits their potential applications as luminescent materials. However, traditional approaches to convert them into aggregate emitters often require intricate molecular design, tedious synthesis, and significant time and resource consumption. Herein, we present a cocrystallization-induced emission strategy that can transform non-emissive (hetero)aryl-substituted Schiff bases into green-yellow to yellow aggregate emitters via even simple grinding of a mixture of Schiff bases and 1,2,4,5-tetracyanobenzene (TCB) mixtures. The combined experimental and theoretical analysis revealed that the cocrystallization inhibits the C=N isomerization and promotes face-to-face π-π interaction, which restricts access to both the dark state and canonical intersection to ultimately induce emission. Furthermore, the induced emission enables the observation of solid-state molecular diffusion through fluorescence signals, advancing white light emission diodes, and notably, solution-processed organic light-emitting diodes based on cocrystal for the first time. This study not only highlights the potential of developing new C=N structural motifs for AIEgens but also could boost advancements in related structure motifs like C=C and N=N.

Novel Anthracene and Carbazole Based Aggregation Induced Enhanced Emission Active Schiff Base as a Selective Sensor for Cu2+ ions

In present work our group has synthesized two novel Schiff-bases, Di-Carbazole based Schiff-base (DB-1) and Di-Anthracene based Schiff-base (DB-2) using condensation reaction and characterized thorough different spectroscopic techniques such as mass spectrometry, IR spectroscopy, 1H and 13C NMR spectroscopy. Furthermore, the AIE(Aggregation induced emission) studies were done using water-THF mixture. As compared to pure THF, the DB-2 showed a 17.8-fold increase in fluorescence intensity with a bathochromic shift of 64 nm in 80% water: THF mixture. For DB-1increase was seen at 70% water-THF combination. The analysis of the dynamic light scattering (DLS) further supported this excellent AIEE (Aggregation induced enhanced emission) characteristic. Furthermore, the spectrofluorometric techniques were used to examine the capacity of both Schiff bases to detect the heavy metals. It was discovered that only DB-1, with a detection limit of 2.4 × 10-8 M, was selective for the Cu2+ ion, whereas DB-2 had no sensing capability for metal ions. The Job's plot was used to determine the stoichiometry ratio of the DB-1 with Cu2+ to further examine the process. It was discovered that the ratio was 1:1 (DB-1:Cu2+). Additionally, the association constant of DB-1 for Cu2+ was 5.1 × 1011 M-1, demonstrating the excellent binding affinity of DB-1 for the Cu2+ ion.

State-of-the-art electrochemical biosensors based on covalent organic frameworks and their hybrid materials

As the development of global population and industry civilization, the accurate and sensitive detection of intended analytes is becoming an important and great challenge in the field of environmental, medical, and public safety. Recently, electrochemical biosensors have been constructed and used in sensing fields, such as antibiotics, pesticides, specific markers of cancer, and so on. Functional materials have been designed and prepared to enhance detection performance. Among all reported materials, covalent organic frameworks (COFs) are emerging as porous crystalline materials to construct electrochemical biosensors, because COFs have many unique advantages, including large surface area, high stability, atom-level designability, and diversity, to achieve a far better sensing performance. In this comprehensive review, we not only summarize state-of-the-art electrochemical biosensors based on COFs and their hybrid materials but also highlight and discuss some typical examples in detail. We finally provide the challenge and future perspective of COFs-based electrochemical biosensors.

2D Conjugated Polymer Thin Films for Organic Electronics: Opportunities and Challenges

2D conjugated polymers (2DCPs) possess extended in-plane π-conjugated lattice and out-of-plane π-π stacking, which results in enhanced electronic performance and potentially unique band structures. These properties, along with predesignability, well-defined channels, easy postmodification, and order structure attract extensive attention from material science to organic electronics. In this review, the recent advance in the interfacial synthesis and conductivity tuning strategies of 2DCP thin films, as well as their application in organic electronics is summarized. Furthermore, it is shown that, by combining topology structure design and targeted conductivity adjustment, researchers have fabricated 2DCP thin films with predesigned active groups, highly ordered structures, and enhanced conductivity. These films exhibit great potential for various thin-film organic electronics, such as organic transistors, memristors, electrochromism, chemiresistors, and photodetectors. Finally, the future research directions and perspectives of 2DCPs are discussed in terms of the interfacial synthetic design and structure engineering for the fabrication of fully conjugated 2DCP thin films, as well as the functional manipulation of conductivity to advance their applications in future organic electronics.

Research Progress on the Application of Covalent Organic Framework Nanozymes in Analytical Chemistry

Covalent organic frameworks (COFs) are porous crystals that have high designability and great potential in designing, encapsulating, and immobilizing nanozymes. COF nanozymes have also attracted extensive attention in analyte sensing and detection because of their abundant active sites, high enzyme-carrying capacity, and significantly improved stability. In this paper, we classify COF nanozymes into three types and review their characteristics and advantages. Then, the synthesis methods of these COF nanozymes are introduced, and their performances are compared in a list. Finally, the applications of COF nanozymes in environmental analysis, food analysis, medicine analysis, disease diagnosis, and treatment are reviewed. Furthermore, we also discuss the application prospects of COF nanozymes and the challenges they face.

Recent Progress in Covalent Organic Frameworks for Cathode Materials

Covalent organic frameworks (COFs) are constructed from small organic molecules through reversible covalent bonds, and are therefore considered a special type of polymer. Small organic molecules are divided into nodes and connectors based on their roles in the COF's structure. The connector generally forms reversible covalent bonds with the node through two reactive end groups. The adjustment of the length of the connector facilitates the adjustment of pore size. Due to the diversity of organic small molecules and reversible covalent bonds, COFs have formed a large family since their synthesis in 2005. Among them, a type of COF containing redox active groups such as -C=O-, -C=N-, and -N=N- has received widespread attention in the field of energy storage. The ordered crystal structure of COFs ensures the ordered arrangement and consistent size of pores, which is conducive to the formation of unobstructed ion channels, giving these COFs a high-rate performance and a long cycle life. The voltage and specific capacity jointly determine the energy density of cathode materials. For the COFs' cathode materials, the voltage plateau of their active sites' VS metallic lithium is mostly between 2 and 3 V, which has great room for improvement. However, there is currently no feasible strategy for this. Therefore, previous studies mainly improved the theoretical specific capacity of the COFs' cathode materials by increasing the number of active sites. We have summarized the progress in the research on these types of COFs in recent years and found that the redox active functional groups of these COFs can be divided into six subcategories. According to the different active functional groups, these COFs are also divided into six subcategories. Here, we summarize the structure, synthesis unit, specific surface area, specific capacity, and voltage range of these cathode COFs.

Recent advances in two-dimensional polymers: synthesis, assembly and energy-related applications

Two-dimensional polymers (2DPs) are a class of 2D crystalline polymer materials with definite structures, which have outstanding physical-chemical and electronic properties. They cleverly link organic building units through strong covalent bonds and can construct functional 2DPs through reasonable design and selection of different monomer units to meet various application requirements. As promising energy materials, 2DPs have developed rapidly in recent years. This review first introduces the basic overview of 2DPs, such as their historical development, inherent 2D characteristics and diversified topological advantages, followed by the summary of the typical 2DP synthesis methods recently (including "top-down" and "bottom-up" methods). The latest research progress in assembly and processing of 2DPs and the energy-related applications in energy storage and conversion are also discussed. Finally, we summarize and prospect the current research status, existing challenges, and future research directions of 2DPs.

Porous organic polymers-based fluorescent chemosensors for Fe(III) ions-a functional mimic of siderophores

Extended organic polymers such as amorphous Covalent Organic Polymers (COPs) and crystalline Covalent Organic Frameworks (COFs) are emerging functional polymeric materials that have recently been shown promises as luminescent materials for chemosensing applications. A wide variety of luminescence COPs and COFs have been synthesized and successfully used as fluorescence-sensing materials for hazardous environmental pollutants and toxic contaminants. This review exemplifies various COPs and COFs-based fluorescence sensors for selective sensing of Fe(III) ions. The fluorescence sensors are sorted according to their structural features and each section provides a detailed discussion on the synthesis and fluorescence sensing ability of different COPs and COFs towards Fe(III) ions. Also, this review highlights the limitations of the existing organic polymer-based chemosensors and future perspectives on translating COPs and COFs-based fluorescence sensors for the practical detection of Fe(III) ions.

Covalent Organic Framework Membranes and Water Treatment

Covalent organic frameworks (COFs) are an emerging class of highly porous crystalline organic polymers comprised entirely of organic linkers connected by strong covalent bonds. Due to their excellent physicochemical properties (e.g., ordered structure, porosity, and stability), COFs are considered ideal materials for developing state-of-the-art separation membranes. In fact, significant advances have been made in the last six years regarding the fabrication and functionalization of COF membranes. In particular, COFs have been utilized to obtain thin-film, composite, and mixed matrix membranes that could achieve effective rejection (mostly above 80%) of organic dyes and model organic foulants (e.g., humic acid). COF-based membranes, especially those prepared by embedding into polyamide thin-films, obtained adequate rejection of salts in desalination applications. However, the claims of ordered structure and separation mechanisms remain unclear and debatable. In this perspective, we analyze critically the design and exploitation of COFs for membrane fabrication and their performance in water treatment applications. In addition, technological challenges associated with COF properties, fabrication methods, and treatment efficacy are highlighted to redirect future research efforts in realizing highly selective separation membranes for scale-up and industrial applications.

Covalent-Organic Framework-Based Materials in Theranostic Applications: Insights into Their Advantages and Challenges

Nanomedicine has been essential in bioimaging and cancer therapy in recent years. Nanoscale covalent-organic frameworks (COFs) have been growing as an adequate classification of biomedical nanomaterials with practical application prospects because of their increased porosity, functionality, and biocompatibility. The high sponginess of COFs enables the incorporation of distinct imaging and therapeutic mechanisms with a better loading efficiency. Nevertheless, preliminary biocompatibility limits their possibility for clinical translation. Thus, cutting-edge nanomaterials with high biocompatibility and improved therapeutic efficiency are highly expected to fast-track the clinical translation of nanomedicines. The inherent effects of nanoscale COFs, such as proper size, modular pore geometry and porosity, and specific postsynthetic transformation through simple organic changes, make them particularly appealing for prospective nanomedicines. The organic building blocks of COFs may also be postmodified for particular binding to biomarkers. The exceptional features of COFs cause them to be an encouraging nanocarrier for bioimaging and therapeutic applications. In this review, we have systematically discussed the advances of COFs in the field of theranostics by providing essential features of COFs along with their synthetic methods. Further, the applications of COFs in the field of theranostics (such as drug delivery systems, photothermal, and photodynamic therapy) are discussed in detail with the help of available literature to date. Furthermore, the advantages of COFs over other materials for therapeutics and drug delivery are discussed. Finally, the review concludes with potential future COF applications in the theranostic field.

Single Cobalt Ion-Immobilized Covalent Organic Framework for Lithium-Sulfur Batteries with Enhanced Rate Capabilities

Covalent organic frameworks (COFs) are notable for their remarkable structure, function designability, and tailorability, as well as stability, and the introduction of "open metal sites" ensures the efficient binding of small molecules and activation of substrates for heterogeneous catalysis and energy storage. Herein, we use the postsynthetic metal sites to catalyze polysulfide conversion and to boost the binding affinity to active matter for lithium-sulfur batteries (LSBs). A dual-pore COF, USTB-27, with hxl topology has been successfully assembled from the imine chemical reaction between 2,3,8,9,14,15-hexa(4-formylphenyl)diquinoxalino [2,3-a:2',3'-c]phenazine and [2,2'-bipyridine]-5,5'-diamine. The chelating nitrogen sites of both modules are able to postsynthetically functionalize with single cobalt sites to generate USTB-27-Co. The discharge capacity of the sulfur-loaded S@USTB-27-Co composite in a LSB is 1063, 945, 836, 765, 696, and 644 mA h g-1 at current densities of 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 C, respectively, much superior to that of non-cobalt-functionalized species S@USTB-27. Following the increased current densities, the rate performance of S@USTB-27-Co is much better than that of S@USTB-27. In particular, the capacity retention at 5.0 C has a magnificent increase from 19% for the latter species to 61% for the former one. Moreover, S@USTB-27-Co exhibits a higher specific capacity of 543 mA h g-1 than that of S@USTB-27 (402 mA h g-1) at a current density of 1.0 C after electrochemical cycling for 500 runs. This work illustrates the "open metal sites" strategy to engineer the active chemical component conversion in COF channels as well as their binding strength for specific applications.

2D nanomaterial-based 3D network hydrogels for anti-infection therapy

Two-dimensional nanomaterials (2D NMs) refer to nanomaterials that possess a planar topography with a thickness of one or several atomic layers. Due to their large specific surface areas, atomic thickness, rough edges, and electron confinement in two dimensions, they have emerged as promising antimicrobial agents over antibiotics in combating bacterial infections. However, 2D NMs encounter issues such as low bio-safety, easy aggregation, and limited tissue penetration efficiency. To address these concerns, hydrogels with three-dimensional (3D) networks have been developed to encapsulate 2D NMs, aiming to enhance their biocompatibility, biodegradability, and ability to regulate and remodel the tissue microenvironment at the infected site. This review systematically summarizes the current studies on 2D NM-based antibacterial hydrogels with 3D network structures (named 2N3Hs). Firstly, we introduce the emerging types of 2N3Hs and describe their antibacterial actions. Subsequently, we discuss the applications of 2N3Hs in three biomedical fields, including wound dressing, cancer treatment, and bone regeneration. Finally, we conclude the review with current challenges and future developments for 2N3Hs, highlighting their potential as a promising choice for next-generation biomedical devices, particularly in the field of tissue engineering and regenerative medicine. This review aims to provide a comprehensive and panoramic overview of anti-infective 2N3Hs for various biomedical applications.

Synthesis, characterization and NLO properties of 1,4-phenylenediamine-based Schiff bases: a combined theoretical and experimental approach

In the current study, three novel 1,4-phenylenediamine-based chromophores (3a-3c) were synthesized and characterized and then their nonlinear optical (NLO) characteristics were explored theoretically. The characterization was done by spectroscopic analysis, i.e. FT-IR, UV-Visible, and NMR spectroscopy, and elemental analysis. Notably, these chromophores exhibited UV-Visible absorption within the range of 378.635-384.757 nm in acetonitrile solvent. Additionally, the FMO findings for 3a-3c revealed the narrowest band gap (4.129 eV) for 3c. The GRPs for these chromophores were derived from HOMO-LUMO energy values, which showed correspondence with FMO results by depicting a minimum hardness (2.065 eV) for 3c. Among these compounds, 3c displayed the highest nonlinear behavior with maximum μtot, βtot and γtot values of 4.79 D, 8.00 × 10-30 and 8.13 × 10-34 a.u., respectively. Our findings disclosed that the synthesized 1,4-phenylenediamine chromophores may be considered promising candidates for nonlinear optical materials, showing potential applications in the realm of optoelectronic devices.

Increasing Donor-Acceptor Interactions and Particle Dispersibility of Covalent Triazine Frameworks for Higher Crystallinity and Enhanced Photocatalytic Activity

Covalent triazine frameworks (CTFs) have recently emerged as an efficient class of photocatalysts due to their structural diversity and excellent stability. Nevertheless, the synthetic reactions of CTFs have usually suffered from poor reversibility, resulting in a low crystallinity of the materials. Here, we report the introduction of methoxy groups on the monomer 2,5-diphenylthiazolo[5,4-d]thiazole to reinforce interlayer π-π interactions of the resulting donor-acceptor type CTFs, which improved crystallinity, further increasing the visible light absorption range and allowing for efficient separation and transport of carriers. The morphology is strongly correlated to the wettability, which has a significant impact on the mass transfer capacity and photocatalytic activity in the photocatalytic reaction. To further improve crystallinity and photocatalytic activity, CTF-NWU-T3 photocatalysts in a bowl shape were prepared using a SiO2 template. The energy band structure, photocatalytic hydrogen evolution, and pollutant degradation efficiency of involved materials were investigated. The donor-acceptor type CTF-NWU-T3 with a bowl-shaped morphology, synthesized using the template method and the introduction of methoxy groups, exhibited an excellent photocatalytic hydrogen production rate of 32064 μmol·h-1·g-1. This study highlights the significance of improving donor-acceptor interactions and increasing the dispersibility of catalyst particles in dispersion to enhance the photocatalytic activity of heterogeneous photocatalysts.

Covalent Organic Frameworks: Their Composites and Derivatives for Rechargeable Metal-Ion Batteries

Covalent organic frameworks (COFs) have attracted considerable interest in the field of rechargeable batteries owing to their three-dimensional (3D) varied pore sizes, inerratic porous structures, abundant redox-active sites, and customizable structure-adjustable frameworks. In the context of metal-ion batteries, these materials play a vital role in electrode materials, effectively addressing critical issues such as low ionic conductivity, limited specific capacity, and unstable structural integrity. However, the electrochemical characteristics of the developed COFs still fall short of practical battery requirements due to inherent issues such as low electronic conductivity, the tradeoff between capacity and redox potential, and unfavorable micromorphology. This review provides a comprehensive overview of the recent advancements in the application of COFs, COF-based composites, and their derivatives in rechargeable metal-ion batteries, including lithium-ion, lithium-sulfur, sodium-ion, sodium-sulfur, potassium-ion, zinc-ion, and other multivalent metal-ion batteries. The operational mechanisms of COFs, COF-based composites, and their derivatives in rechargeable batteries are elucidated, along with the strategies implemented to enhance the electrochemical properties and broaden the range of their applications.

MOF (UiO-66-NH2)@COF (TFP-TABQ) hybrids via on-surface condensation reactions for sustainable energy storage

Core-shell MOF@COF hybrids were synthesized via subsequent modification of MOF UiO-66-NH2 with 1,3,5-triformylphloroglucinol (TFP) and 2,3,5,6-tetraaminobenzoquinone (TABQ). The hybrids exhibited significant surface area (236 m2 g-1) and outstanding electrochemical performance (103 F g-1 at 0.5 A g-1), surpassing both COFs and MOFs, thereby showcasing the potential of on-surface condensation reactions for developing high-performance energy storage devices.

Pure Covalent-Organic Framework Membrane as a Label-Free Biomimetic Nanochannel for Sensitive and Selective Sensing of Chiral Flavor Substances

Chiral flavor substances play an important role in the human perception of different tastes. Here, we report a pure covalent-organic framework (COF) membrane nanochannel in combination with a chiral gold nanoparticles (AuNPs) selector for sensing chiral flavor substances. The pure COF membrane with a proper pore size is selected as the nanochannel, while l-cysteine-modified AuNPs (l-Cys-AuNPs) are used as the chiral selector. l-Cys-AuNPs show stronger binding to the S-enantiomer than the R-enantiomer, causing current reduction to different degrees for the R- and S-enantiomer to achieve chiral sensing due to the synergistic effect of the size exclusion of the COF nanochannel and the chiral selectivity of l-Cys-AuNPs. The developed COF membrane nanochannel sensing platform not only allows an easy balance of the permeability and selectivity, which is difficult to achieve in traditional polymer membrane nanochannel sensors, but also exhibits better chiral performance than commercial artificial anodic aluminum oxide (AAO) nanochannel sensors. The developed nanochannel sensor is successfully applied for sensing flavor enantiomers such as limonene, propanediol, methylbutyric acid, and butanol with the enantiomer excess values of 55.2% (propanediol) and 72.4% (limonene) and the low detection limits of 36 (limonene) and 71 (propanediol) ng L-1. This study provides a new idea for the construction of nanochannel platforms based on the COF for sensitive and selective chiral sensing.

Organic electrodes based on redox-active covalent organic frameworks for lithium batteries

Electroactive organic materials have received much attention as alternative electrodes for metal-ion batteries due to their high theoretical capacity, resource availability, and environmental friendliness. In particular, redox-active covalent organic frameworks (COFs) have recently emerged as promising electrodes due to their tunable electrochemical properties, insolubility in electrolytes, and structural versatility. In this Highlight, we review some recent strategies to improve the energy density and power density of COF electrodes for lithium batteries from the perspective of molecular design and electrode optimisation. Some other aspects such as stability and scalability are also discussed. Finally, the main challenges to improve their performance and future prospects for COF-based organic batteries are highlighted.

Synthesis and Additive Manufacturing of Hydrazone-Linked Covalent Organic Framework Aerogels

Covalent Organic Frameworks (COFs) are crystalline, porous organic materials. Recent studies have demonstrated novel processing strategies for COFs to form adaptable architectures, but these have focused primarily on imine-linked COFs. This work presents a new synthesis and processing route to produce crystalline hydrazone-linked COF gels and aerogels with hierarchical porosity. The method was implemented to produce a series of hydrazone-linked COFs with different alkyl side-chain substituents, achieving control of the hydrophilicity of the final aerogel. Variation in the length of the alkyl substituents yielded materials with controllable form factors that can preferentially adsorb water or nonpolar organic solvents. Additionally, a method for additive manufacturing of hydrazone-linked COFs using hydroxymethylcellulose as a sacrificial additive is presented. This work demonstrates an effective and simple approach to the fabrication of hydrazone COF aerogels and additive manufacturing to produce hydrazone COFs of desired shape.

Single-crystal polymers (SCPs): from 1D to 3D architectures

Single-crystal polymers (SCPs) with unambiguous chemical structures at atomic-level resolutions have attracted great attention. Obtaining precise structural information of these materials is critical as it enables a deeper understanding of the potential driving forces for specific packing and long-range order, secondary interactions, and kinetic and thermodynamic factors. Such information can ultimately lead to success in controlling the synthesis or engineering of their crystal structures for targeted applications, which could have far-reaching impact. Successful synthesis of SCPs with atomic level control of the structures, especially for those with 2D and 3D architectures, is rare. In this review, we summarize the recent progress in the synthesis of SCPs, including 1D, 2D, and 3D architectures. Solution synthesis, topochemical synthesis, and extreme condition synthesis are summarized and compared. Around 70 examples of SCPs with unambiguous structure information are presented, and their synthesis methods and structural analysis are discussed. This review offers critical insights into the structure-property relationships, providing guidance for the future rational design and bottom-up synthesis of a variety of highly ordered polymers with unprecedented functions and properties.

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.

Tailor-made β-ketoenamine-linked covalent organic polymer nanofilms for precise molecular sieving

The membranes that accurately separate solutes with close molecular weights in harsh solvents are of crucial importance for the development of highly-precise organic solvent nanofiltration (OSN). The physicochemical structures of the membrane need to be rationally designed to achieve this goal, such as customized crosslinked networks, thickness, and pore size. Herein, we synthesize a type of covalent organic polymer (COP) nanofilms with tailor-made thickness and pore structure using a cyclic deposition strategy for precise molecular sieving. By elaborately designing monomer structures and controlling deposition cycle numbers, the COP nanofilms linked by robust β-ketoenamine blocks were endowed with sub-nanometer micropores and a linearly tunable thickness of 10-40 nm. The composite membranes integrating COP nanofilms exhibited adjustable solvent permeance. The membranes further demonstrated steep and finely-regulated rejection curves within the molecular weight range of 200 to 400 Da, where the difference value was as low as 40 Da. The efficient purification and concentration of the antibacterial drug and its intermediate was well achieved. Therefore, the exploited COP nanofilms markedly facilitate the application of microporous organic polymers for precise molecular separation in OSN.

Regio- and Enantioselective Macrocyclization from Dynamic Imine Formation: Chemo- and Enantioselective Fluorescent Recognition of Lysine

The dynamic covalent chemistry of imines is utilized to conduct a regioselective as well as enantioselective synthesis of an unsymmetric (C1) chiral macrocycle from the reaction of an unsymmetric (C1) chiral dialdehyde, (S)-4, that contains a salicylaldehyde unit and a benzaldehyde unit, with lysine, an unsymmetric (C1) chiral diamine. The enantioselectivity is further enhanced in the presence of Zn2+. Compound (S)-4 in combination with Zn2+ is found to be a highly chemoselective as well as enantioselective fluorescent probe for lysine. It can be used to detect specific enantiomers of this amino acid.

Schiff Base Reaction in a Living Cell: In Situ Synthesis of a Hollow Covalent Organic Polymer To Regulate Biological Functions

Artificially performing chemical reactions in living biosystems to attain various physiological aims remains an intriguing but very challenging task. In this study, the Schiff base reaction was conducted in cells using Sc(OTf)3 as a catalyst, enabling the in situ synthesis of a hollow covalent organic polymer (HCOP) without external stimuli. The reversible Schiff base reaction mediated intracellular Oswald ripening endows the HCOP with a spherical, hollow porous structure and a large specific surface area. The intracellularly generated HCOP reduced cellular motility by restraining actin polymerization, which consequently induced mitochondrial deactivation, apoptosis, and necroptosis. The presented intracellular synthesis system inspired by the Schiff base reaction has strong potential to regulate cell fate and biological functions, opening up a new strategic possibility for intervening in cellular behavior.

Covalent organic frameworks: linkage types, synthetic methods and bio-related applications

Covalent organic frameworks (COFs) are composed of small organic molecules linked via covalent bonds, which have tunable mesoporous structure, good biocompatibility and functional diversities. These excellent properties make COFs a promising candidate for constructing biomedical nanoplatforms and provide ample opportunities for nanomedicine development. A systematic review of the linkage types and synthesis methods of COFs is of indispensable value for their biomedical applications. In this review, we first summarize the types of various linkages of COFs and their corresponding properties. Then, we highlight the reaction temperature, solvent and reaction time required by different synthesis methods and show the most suitable synthesis method by comparing the merits and demerits of various methods. To appreciate the cutting-edge research on COFs in bioscience technology, we also summarize the bio-related applications of COFs, including drug delivery, tumor therapy, bioimaging, biosensing and antimicrobial applications. We hope to provide insight into the interdisciplinary research on COFs and promote the development of COF nanomaterials for biomedical applications and their future clinical translations.

Developing a fast and catalyst-free protocol to form C=N double bond with high functional group tolerance

The carbon-nitrogen double bond (C=N) is a fundamentally important functional group in organic chemistry. This is largely due to the fact that C=N acts as electrophilic synthon to give nitrogen-containing compounds. Here, we report the condensation of primary amine or hydrazine with very electron-deficient aldehyde to form C=N bond in the absence of any catalysts (metals and acids). The protocol performs at room temperature and applies water as co-solvent. Two hundred examples are presented here. With its intrinsic advantages of wide substrate scopes, excellent efficiency (high yields and short reaction time), operational simplicity, mild condition (room temperature as reaction temperature, no catalysts, no additions, water as co-solvent and opening to air) and available starting materials, the protocol can be compatible with various drugs, prodrugs, dyes and pharmacophores containing primary amino group. In addition, we also successfully apply this protocol to rapidly synthesize the core scaffolds of bioactive molecules.

Antifouling and Injectable Granular Hydrogel for the Prevention of Postoperative Intrauterine Adhesion

Postoperative intrauterine adhesion (IUA), caused by endometrial basal layer injury, is one of the main causes of female infertility. The excessive deposition of fibrin as well as fibroblast is considered the root cause of IUA. However, few clinical strategies are effective in preventing extracellular matrix (ECM) deposition at endometrial wounds that include protein and cell deposits. Herein, the injectable granular poly(N-(2-hydroxyethyl) acrylamide) (PHEAA) hydrogel (granular PHEAA gel), which presents excellent antifouling properties and remarkably prevents protein and cell adhesions, is used to prevent postoperative IUA. The granular PHEAA gel with a jammed network structure exhibits outstanding injectability and superior stability. Compared with the IUA group, the granular PHEAA gel can promote regeneration of the endometrium while reducing the area of endometrial fibrosis. Immunohistochemical staining experiments indicate that the granular PHEAA gel can improve the proliferation of the endometrium, promote vascularization, and enhance anti-inflammatory effect in IUA rats. And the granular PHEAA gel can effectively slow down the fibrosis of uterine tissue. Importantly, the number of embryos is significantly increased after injecting granular PHEAA gel, inferring that there is an obvious reproductive function recovery of injured endometrium.

Anatase TiO2-x and zwitterionic porphyrin polymer-based nanocomposite for enhanced cancer photodynamic therapy

Photodynamic therapy has been used as a treatment option for cancer; however, the existing TiO2 photosensitizer does not have the ability to specifically target cancer cells. This lack of selectivity reduces its effectiveness in overcoming cancer resistance. To improve photodynamic therapy outcomes, an innovative solution is proposed. In this study, we report on the compounding of a zwitterionic covalent organic polymer (COP) with a TiO2 photosensitizer for the first time. The aim is to overcome cancer cellular resistance. A one-pot synthetic strategy, which includes the construction of a porphyrin-based COP has been employed. This strategy has also been applied to the rapid preparation of anatase defective TiO2 (TiO2-x). To improve the hydrophilic and antifouling properties of the polymer, zwitterion L-cysteine has been conjugated with a porphyrin-based COP using a thiol-ene "click chemistry" reaction. The novel zwitterionic porphyrin-based COP has the ability to trigger biodegradation under the acid microenvironment due to the presence of acid-sensitive β-thioether esters. When combined with TiO2-x, the resultant nanocomposite produces an enhanced photodynamic therapy effect for drug-resistant cancer cells under NIR laser irradiation. This is due to the strong mutual sensitization of zwitterionic porphyrin-based COP and TiO2-x. Importantly, the nanocomposite delivery system exhibits excellent cytocompatibility in the dark and has the potential to improve the accuracy of cancer diagnosis through fluorescence imaging. The results of this study demonstrate the potential application of this alternative nanocomposite delivery system for remote-controllable photodynamic therapy of tumors.

Covalent connections between metal-organic frameworks and polymers including covalent organic frameworks

Hybrid composite materials combining metal-organic frameworks (MOFs) and polymers have emerged as a versatile platform for a broad range of applications. The crystalline, porous nature of MOFs and the flexibility and processability of polymers are synergistically integrated in MOF-polymer composite materials. Covalent bonds, which form between two distinct materials, have been extensively studied as a means of creating strong molecular connections to facilitate the dispersion of "hard" MOF particles in "soft" polymers. Numerous organic transformations have been applied to post-synthetically connect MOFs with polymeric species, resulting in a variety of covalently connected MOF-polymer systems with unique properties that are dependent on the characteristics of the MOFs, polymers, and connection modes. In this review, we provide a comprehensive overview of the development and strategies involved in preparing covalently connected MOFs and polymers, including recently developed MOF-covalent organic framework composites. The covalent bonds, grafting strategies, types of MOFs, and polymer backbones are summarized and categorized, along with their respective applications. We highlight how this knowledge can serve as a basis for preparing macromolecular composites with advanced functionality.

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

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

Interfacial chemistries in metal-organic framework (MOF)/covalent-organic framework (COF) hybrids

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been attracting tremendous attention in various applications due to their unique structural properties. Recent interest has been focused on their combination as hybrids to enable the engineering of new classes of frameworks with complementary properties. This review gives a comprehensive summary on the interfacial chemistries in MOF/COF hybrids, which play critical roles in their hybridization. The challenges and perspectives in the field of MOF/COF hybrids are also provided to inspire more efforts in diversifying this hybrid family and their cross-disciplinary applications.

Integrated CO2 capture and electrochemical upgradation: the underpinning mechanism and techno-chemical analysis

Coupling post-combustion CO2 capture with electrochemical utilization (CCU) is a quantum leap in renewable energy science since it eliminates the cost and energy involved in the transport and storage of CO2. However, the major challenges involved in industrial scale implementation are selecting an appropriate solvent/electrolyte for CO2 capture, modeling an appropriate infrastructure by coupling an electrolyser with a CO2 point source and a separator to isolate CO2 reduction reaction (CO2RR) products, and finally selection of an appropriate electrocatalyst. In this review, we highlight the major difficulties with detailed mechanistic interpretation in each step, to find out the underpinning mechanism involved in the integration of electrochemical CCU to achieve higher-value products. In the past decades, most of the studies dealt with individual parts of the integration process, i.e., either selecting a solvent for CO2 capture, designing an electrocatalyst, or choosing an ideal electrolyte. In this context, it is important to note that solvents such as monoethanolamine, bicarbonate, and ionic liquids are often used as electrolytes in CO2 capture media. Therefore, it is essential to fabricate a cost-effective electrolyser that should function as a reversible binder with CO2 and an electron pool capable of recovering the solvent to electrolyte reversibly. For example, reversible ionic liquids, which are non-ionic in their normal forms, but produce ionic forms after CO2 capture, can be further reverted back to their original non-ionic forms after CO2 release with almost 100% efficiency through the chemical or thermal modulations. This review also sheds light on a focused techno-economic evolution for converting the electrochemically integrated CCU process from a pilot-scale project to industrial-scale implementation. In brief, this review article will summarize a state-of-the-art argumentation of challenges and outcomes over the different segments involved in electrochemically integrated CCU to stimulate urgent progress in the field.

Large-Scale Synthesis of Covalent Organic Frameworks: Challenges and Opportunities

Connecting organic building blocks by covalent bonds to design porous crystalline networks has led to covalent organic frameworks (COFs), consequently transferring the flexibility of dynamic linkages from discrete architectures to extended structures. By virtue of the library of organic building blocks and the diversity of dynamic linkages and topologies, COFs have emerged as a novel field of organic materials that propose a platform for tailor-made complex structural design. Progress over the past two decades in the design, synthesis, and functional exploration of COFs in diverse applications successively established these frameworks in materials chemistry. The large-scale synthesis of COFs with uniform structures and properties is of profound importance for commercialization and industrial applications; however, this is in its infancy at present. An innovative designing and synthetic approaches have paved novel ways to address future hurdles. This review article highlights the fundamental of COFs, including designing principles, coupling reactions, topologies, structural diversity, synthetic strategies, characterization, growth mechanism, and activation aspects of COFs. Finally, the major challenges and future trends for large-scale COF fabrication are outlined.

Recent Progress of Covalent Organic Frameworks Applied in Electrochemical Sensors

As an emerging porous crystalline organic material, the covalent organic frameworks (COFs) are given more and more attention in many fields, such as gas storage and separation, catalysis, energy storage and conversion, luminescent devices, drug delivery, pollutant adsorption and removal, analysis and detection due to their special advantages of high crystallinity, flexible designability, controllable porosities and topologies, intrinsic chemical and thermal stability. In recent years, the COFs are applied in analytical chemistry, for instance, chromatography, solid-phase microextraction, luminescent and colorimetric sensing, surface-enhanced Raman scattering and electroanalytical chemistry. The COFs decorated electrodes show high performance for detecting trace substances with remarkable selectivity and sensitivity, such as heavy metal ions, glucose, hydrogen peroxide, drugs, antibiotics, explosives, phenolic compounds, pesticides, disease metabolites and so on. This review mainly summarized the application of COF based electrochemical sensor according to different target analytes.