Highly ordered, side chain entanglement free mercury removal with high reusing ability and cost effective.
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•The highly ordered AA stacking MTF was prepared via transformation ...strategy.•MTF was used for effective mercury removal, mechanism studied by XPS, 13C CP/MAS NMR.•Role of aromatic triazine was revealed by comparing with aliphatic TAG-TF’s efficiency.•MTF shows high reusing ability, 2.2 times greater removal efficiency than TAG-TF.•MTF is cost-effective, highly efficient, reusable and suitable for practical applications.
The accumulation of mercury in the food chain and environment is harmful to living beings. This raises the need for high affinity, reusable cost-efficient adsorbents for mercury. Herein, we report a side chain entanglement free hetero atom effect bearing covalent organic framework MTF prepared by integrating melamine and thiophene linker. The AA stacked MTF-2 was prepared via transformation strategy from its AB stacked MTF-1 congener. The MTF-1 and MTF-2 were comprehensively analyzed through PXRD, SEM, TEM, 13C CP/MAS, N2 sorption and mercury removal efficiency. The adsorption capacity of MTF-2 revealed a value of 540 mg g−1, which is greater than that of MTF-1 (328 mg g−1). The adsorption mechanism was studied through XPS, 13C CP/MAS and XAFS indicating probable coordination of Hg2+ with both the triazine and sulfur moieties in a cooperative manner. To demonstrate the role of aromatic triazine ring, the analogous aliphatic triaminoguanidine was selected and the removal efficiencies between triaminoguanidine-thiophene COF (TAG-TF) and MTF-2 were compared. It revealed that the triazine unit containing MTF-2 showed 2.2 times greater removal efficiency than TAG-TF. The results reveal the structure-performance relationship, where the high surface area and relatively ordered functional moieties both paly a synergistic role in efficient mercury adsorption.
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•The magnetic covalent organic frameworks (MCOFs) are divided into three categories.•The main characteristics of MCOFs and different synthesis methods are introduced.•The application ...scope of MCOFs is comprehensively investigated.•The application mechanism of MCOFs in various aspects is explained reasonably.•The future development and challenges of MCOFs have been prospected.
Magnetic nanoparticles (MNPs) possess outstanding rapid magnetic separation ability due to their excellent superparamagnetism and stability. Covalent organic frameworks (COFs) have the advantages of porous structure, large specific surface area, remarkable acid–base and thermal stability that can form novel magnetic nanocomposites with MNPs. The formed magnetic covalent organic frameworks (MCOFs) composite material owns high saturation magnetization and prominent chemical stability, which is the great potential material in the fields of environmental remediation and biological applications. Based on the current research results, firstly, this review further simplifies the classification according to the composition and functionalization of the composite: primitive MCOFs, functionalized MCOFs, composite of Fe/Co/Ni and its alloys with COFs. Secondly, several major characteristics and diverse synthesis methods of MCOFs composites are described. Thirdly, the applications of MCOFs in adsorption and enrichment detection, catalysis, sensing and biomedical aspect are reviewed in detail, and the mechanisms of these processes have been fully and reasonably explained. Finally, the future development and challenges of MCOFs composite materials have been prospected. This work aims to provide a theoretical basis for the synthesis and design of MCOFs composite materials in the future.
Covalent Organic Frameworks
In article number 2304989, Lei‐Lei Liu, Zhongyue Li, and co‐workers synthesize a calix4arene‐derived covalent organic framework (COF)‐C4A‐benzothiadiazole (BTD), which ...exhibits high crystallinity and features a non‐interpenetrating undulating 2D layered structure with AA‐stacking. COF‐C4A‐BTD has an appropriate electron donor‐acceptor and energy band structures which can facilitate the generation and separation of ·O2− and h+, resulting in efficient visible‐light‐driven activity for degrading Bisphenol A, Rhodamine B, and Methylene blue.
The ordered π skeletons of covalent organic frameworks make them viable light‐emitting materials but their limited tunability has precluded further implementation. Here we report the synthesis of ...hydrazone‐linked frameworks which are stable in water, acid, and base, and demonstrate their utility as a platform for light emission. The polygonal backbone is designed to be luminescent and partially π conjugated while the pore wall is docked with single atom or unit to induce resonance, hyperconjugation, and tautomerization effects. These effects can be transmitted to the backbone, so that the framework can emit three primary colors of light. The wall can be perturbated with multiple surface sites, rendering the material able to edit diverse emission colors in a predesignable and digital way. The systems show high activity, stability, tunability, and sensibility: a set of features attractive for light‐emitting and sensing applications.
Topology‐directed polymerization enables the construction of highly emissive stable covalent organic frameworks linked by hydrazone bond. Perturbation of pore wall surface site can tune the emission to achieve three primary colors of light, rendering the materials able to edit various emission colors by organizing different surface sites onto the pore wall.
To date, significant efforts have been devoted to eliminating hazardous components to purify wastewater through the development of various nanomaterials. Covalent organic frameworks (COFs), an ...important branch of the porous crystalline family, possess the peculiarity of ultrahigh surface area, adjustable pore size, and facile functionality. Exciting studies from design fabrication to potential applications in water treatment by COF-based membranes (COMs) have emerged. This review summarizes various preparation strategies and synthesis mechanisms for COMs, including layer-by-layer stacking, in situ growth, interfacial polymerization, and electrochemical synthesis, and briefly describes the advanced characterization techniques for COMs. Moreover, the application of COMs in heavy metal removal, dye separation, purification of radionuclides, pollutant detection, sea water desalination, and so on, is described and discussed. Finally, the perspectives on future opportunities for designing COMs in water purification have been proposed.
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•Analyzing the advantages of covalent organic frameworks for the preparation of COF-based membranes (COMs).•Advanced characterization techniques for COMs are described.•Various strategies for preparation of COMs are comprehensively summarized.•Summarizing the application of COMs in water treatment and analyzing the potential mechanism.
Covalent organic framework based Z-scheme heterostructure for efficient visible-light-driven hydrogen evolution.
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•A WO3@TpPa-1-COF core–shell Z-scheme heterojunction was firstly ...reported.•Bulk WO3 was etched into ultra-small nanostructurer in the synthesis of composite.•WO3@TpPa-1-COF/rGO(30%) exhibits a high H2 evolution rate of 26.73 mmol·g−1·h−1.•The rGO facilitates the separation of charge carriers in the Z-scheme heterojunction.
Covalent organic frameworks (COFs) are a new type of visible-light-driven photocatalysts, while effectively improving the separation and transfer of light-induced charges is of the key point to further enhance their activity. In this work, a new COF-based core–shell Z-scheme heterojunction WO3@TpPa-1-COF was firstly synthesized by in-situ etching bulk WO3 into ultra-small nanostructure. Further, a ternary WO3@TpPa-1-COF/rGO composite with rGO attached on the surface of TpPa-1-COF was prepared by a facile one-pot photoreduction of GO solution containing as-synthesized WO3@TpPa-1-COF. The results of photocatalytic measurements show that the WO3@TpPa-1-COF/rGO(30%) composite material possesses a hydrogen evolution rate of 26.73 mmol·g−1·h−1 under visible-light irradiation, which is 11.73 and 1.6 times higher than that of TpPa-1-COF and WO3@TpPa-1-COF, respectively. Further study demonstrate a Z-Scheme charge transfer pathway exists in WO3@TpPa-1-COF/rGO composite which promote the separation of photogenerated charge carriers from COF, while the rGO attached on COF serves as electron collector in photocatalytic process further facilitating the transfer of photogenerated electrons to active sites. The reported strategy of building core–shell COF-base heterostructure and the resulting architecture with rGO as electron collector in Z-Scheme for facilitating the separation and transfer of charge carriers may open a new way for the design of highly efficient photocatalysts.
•This review focused on the state-of-the-art environmental applications of COFs.•The structural characteristics and functionalization of COFs were briefly introduced.•COFs can be used for catalytic ...degradation of pollutants, H2 storage and CO2 capture.•COFs have been used as adsorbing, separating and sensing toxic pollutants.
Covalent organic frameworks (COFs) is a type of newly developed crystals known for chemical stability, ordered porous structure, and tunable skeleton, as well as luminescence in some cases. By virtue of their advantages, stable COFs play diverse roles in the field of environmental applications, such as adsorbing, separating, sensing and catalytically degrading pollutants. This review mainly focused on the state-of-the-art development of stable COFs in environmental applications, such as adsorption, membrane separation and detection of various environmental pollutants, including heavy metals and radionuclides (Hg2+, UO22+, I2, Nd3+ and TcO4−), toxic organic pollutants (organic dyes, pharmaceuticals, organophosphorus flame retardants, per- and poly-fluorinated alkyl substances and endocrine-disrupting chemicals), as well as the catalytic degradation/conversion and CO2 capture. Their structural characteristics, functional design approaches and specific environmental applications were introduced, and concluding remarks and future research directions were proposed.
The construction of three-dimensional (3D) covalent organic frameworks (COFs) remains challenging due to the limited types of organic building blocks. With octahedral Ti(IV) complex as the building ...unit, this study reports on the first 3D anionic titanium-based COF ( Ti-COF-1 ) with an edge-transitive (6, 4)-connected soc topology. Ti-COF-1 exhibits high crystallinity, superior stability, and large specific surface area (1000.4 m 2 g -1 ). Moreover, Ti-COF-1 has a broad absorption band in the UV spectrum with an optical energy gap of 1.86 eV, and exhibits high photocatalytic activity toward Meerwein addition reactions. This research demonstrates an attractive strategy for the design of 3D functional COFs.
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•COFs offer exceptional platform to construct unique photocatalytic systems.•This review provides the utilization of t of COF as photocatalysts for fuel production.•Roadmap to design ...excellent COF-based photocatalysts is highlighted and discussed.
Photocatalysis-driven fuel production has garnered increasing attention as it can potentially address current energy- and environmental-related issues of the 21st century. However, the current performance of materials used for this application is still limited due to poor light absorption, fast photogenerated electron-hole recombination, and inappropriate active sites. Covalent organic frameworks (COFs), which offer an excellent platform to construct unique photocatalytic systems, have emerged as potential materials for the production of solar fuels. In this review, we investigate the development of COFs for three primary solar-driven fuel production strategies: (i) hydrogen (H2) production, (ii) carbon dioxide (CO2) reduction, and (iii) dinitrogen (N2) fixation. This review provides a roadmap to design excellent COF-based photocatalysts and highlights current limitations in the field of photocatalysis.
Covalent organic frameworks (COFs), constructed by organic building blocks through strong covalent bonds, featuring well-defined structures, excellent stability and desired semiconductor-like ...behavior, have been employed for extensive potential applications, especially in photocatalysis. In this review, we summarize the different methods for the synthesis of COFs, such as solvothermal synthesis, microwave synthesis, ionothermal synthesis, room temperature solution synthesis, mechanochemical synthesis and interfacial synthesis firstly. Then, the structural features of COFs such as diversity, tailorability, stability and porosity. Whereafter, the advantages and fundamentals of COFs in photocatalysis are introduced. Furthermore, the photocatalytic applications of COF-based materials toward H2 production, CO2 reduction, organic transformation and pollution degradation are discussed. Particularly, diverse strategies for improving photocatalytic performance and the corresponding structure-activity relationships are highlighted. Finally, the challenges and future prospects for the development of efficient COF-based photocatalysts are briefly indicated.
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•An overview of the introduction of different methods for the synthesis of COFs.•The structural features of COFs including diversity, tailorability, stability and porosity.•The advantages and fundamentals of COFs in photocatalysis.•Photocatalytic applications of COF-based materials in the fields of H2 production, CO2 reduction, organic transformation and pollution degradation.•The challenges and opportunities for the development of COF-based photocatalysts.
Covalent organic frameworks (COFs) are a new class of crystalline porous materials obtained from covalently attached organic building units. By virtue of the unique characteristics such as periodic and well-defined structures, low-density, high surface area, excellent stability as well as desired semiconductor-like behavior, COFs have gained tremendous attention for functional applications in many fields, especially in photocatalysis. In this review, we summarize the different methods for the synthesis of COFs, such as solvothermal synthesis, microwave synthesis, ionothermal synthesis, room temperature solution synthesis, mechanochemical synthesis and interfacial synthesis firstly. Then, the structural features of COFs including diversity, tailorability, stability and porosity are provided. Afterwards, the fundamentals and advantages of COFs for photocatalysis are briefly introduced. Following this, the photocatalytic applications of COF-based materials toward H2 production, CO2 reduction, organic transformation and pollution degradation are discussed. Meanwhile, a series of strategies are highlighted to improve photocatalytic performance for the understanding of the structure-property relationship in this part. Finally, the remaining challenges and prospects on further development of efficient COF-based photocatalysts are indicated.
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