Covalent organic frameworks (COFs) represent a new field of rapidly growing chemical research that takes direct inspiration from diverse covalent bonds existing between atoms. The success of linking ...atoms in two and three dimensions to construct extended framework structures moved the chemistry of COFs beyond the structures to methodologies, highlighting the possibility of prospective applications. Although structure to property relation in COFs has led to fascinating properties, chemical stability, processability and scalability were some of the important challenges that needed to be overcome for their successful implementation. In this Perspective, we take a closer look at the growth of COFs from mere supramolecular structures to potential industrializable materials.
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IJS, KILJ, NUK, PNG, UL, UM
Research on covalent organic frameworks (COFs) has recently gathered significant momentum by the virtue of their predictive design, controllable porosity, and long-range ordering. However, the lack ...of solvent-free and easy-to-perform synthesis processes appears to be the bottleneck toward their greener fabrication, thereby limiting their possible potential applications. To alleviate such shortcomings, we demonstrate a simple route toward the rapid synthesis of highly crystalline and ultraporous COFs in seconds using a novel salt-mediated crystallization approach. A high degree of synthetic control in interlayer stacking and layer planarity renders an ordered network with a surface area as high as 3000 m2 g–1. Further, this approach has been extrapolated for the continuous synthesis of COFs by means of a twin screw extruder and in situ processes of COFs into different shapes mimicking the ancient terracotta process. Finally, the regular COF beads are shown to outperform the leading zeolites in water sorption performance, with notably facile regeneration ability and structural integrity.
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IJS, KILJ, NUK, PNG, UL, UM
Gold Au(0) nanoparticles immobilized into a stable covalent organic framework (COF) have been synthesized via the solution infiltration method. The as-synthesized Au(0)@TpPa-1 catalyst shows high ...recyclability and superior reactivity for nitrophenol reduction reaction than HAuCl4·3H2O.
Covalent organic frameworks are a family of crystalline porous materials with promising applications. Although active research on the design and synthesis of covalent organic frameworks has been ...ongoing for almost a decade, the mechanisms of formation of covalent organic frameworks crystallites remain poorly understood. Here we report the synthesis of a hollow spherical covalent organic framework with mesoporous walls in a single-step template-free method. A detailed time-dependent study of hollow sphere formation reveals that an inside-out Ostwald ripening process is responsible for the hollow sphere formation. The synthesized covalent organic framework hollow spheres are highly porous (surface area ∼1,500 m(2 )g(-1)), crystalline and chemically stable, due to the presence of strong intramolecular hydrogen bonding. These mesoporous hollow sphere covalent organic frameworks are used for a trypsin immobilization study, which shows an uptake of 15.5 μmol g(-1) of trypsin.
Two new chemically stable functional crystalline covalent organic frameworkds (COFs) (Tp-Azo and Tp-Stb) were synthesized using the Schiff base reaction between triformylphloroglucinol (Tp) and ...4,4′-azodianiline (Azo) or 4,4′-diaminostilbene (Stb), respectively. Both COFs show the expected keto-enamine form, and high stability toward boiling water, strong acidic, and basic media. H3PO4 doping in Tp-Azo leads to immobilization of the acid within the porous framework, which facilitates proton conduction in both the hydrous (σ = 9.9 × 10–4 S cm–1) and anhydrous state (σ = 6.7 × 10–5 S cm–1). This report constitutes the first emergence of COFs as proton conducting materials.
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Conductive 2D metal–organic frameworks (MOFs) have merits beyond traditional MOFs for electrochemical applications, but reports on using MOFs as electrodes for electrochemical microsupercapacitors ...(MSCs) are practically non‐existent. In this work, a Ni‐catecholate‐based MOF (Ni‐CAT MOF) having good conductivity and exhibiting redox chemistry in the positive and negative voltage windows is developed. A novel process is developed to selectively grow the conductive Ni‐CAT MOF on 3D laser scribed graphene (LSG). The LSG with its superior wettability serves as a functional matrix‐current collector for the hybridization of conductive Ni‐CAT MOF nanocrystals. Impressively, MSCs fabricated using the hybrid LSG/Ni‐CAT MOF show significant improvement compared with MOF‐free LSG electrodes. Specifically, the LSG/Ni‐CAT MOF electrodes can deliver MSCs with a wide operating voltage (1.4 V), high areal capacitance (15.2 mF cm−2), energy density (4.1 µWh cm−2), power density (7 mW cm−2), good rate performance, and decent cycling stability. This work opens up an avenue for developing electrochemical microsupercapacitors using conductive MOF electrodes.
An electrochemical microsupercapacitor with high areal capacitances and power density is fabricated based on laser‐scribed 3D graphene and conductive Ni‐catecholate metal–organic framework (MOF) electrodes. This work shows promising potential of conductive MOF for miniature energy storage devices.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Three thermally and chemically stable isoreticular covalent organic frameworks (COFs) were synthesized via room-temperature solvent-free mechanochemical grinding. These COFs were successfully ...compared with their solvothermally synthesized counterparts in all aspects. These solvent-free mechanochemically synthesized COFs have moderate crystallinity with remarkable stability in boiling water, acid (9 N HCl), and base TpBD (MC) in 3 N NaOH and TpPa-2 (MC) in 9 N NaOH. Exfoliation of COF layers was simultaneously observed with COF formation during mechanochemical synthesis. The structures thus obtained seemed to have a graphene-like layered morphology (exfoliated layers), unlike the parent COFs synthesized solvothermally.
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Covalent‐organic frameworks (COFs) represent a new frontier of crystalline porous organic materials with framework structures in 2D or 3D domains, which make them promising for many applications. ...Herein, the fundamental structural design aspects of 2D‐COFs are reviewed, which position them as suitable electrodes for electrochemical energy storage. The ordered π–π stacked arrangement of the organic building blocks in juxtaposed layers provides a pathway for efficient electronic charge transport; the 2D structure provides a pathway for enhanced ionic diffusion, which enhances ionic transport. Importantly, the tunable pore size enables 2D‐COFs to accommodate mobile ions with different sizes and charges, positioning them as prospect materials for various types of batteries. Distinctively, the ability to functionalize their pore system with a periodic array of redox active species, enriching their potential redox chemistry, provides a pathway to control the redox and capacitive contributions to the charge storage mechanism. The strong covalently linked framework backbone of COFs is an additional merit for achieving long cycle life, and stability against the “leaching out” problem of active molecules in strong electrolytes as observed in other organic materials applied in energy storage devices.
2D covalent‐organic frameworks (2D‐COFs) have emerged as promising electrode materials for energy storage applications. The predesignable structure and tailored porosity of 2D‐COFs allow precise integration of redox‐functionalities for energy storage applications. This review features the categorization of various functional linkages deployed for the construction of 2D‐COFs and their key merits as electrode materials for supercapacitors and rechargeable metal‐ion battery applications.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A strong bond: A strategy based on intramolecular hydrogen‐binding interactions in 2D covalent organic frameworks (COFs) is shown to improve the crystallinity, porosity, and chemical stability of the ...material (see picture). The concept is validated by removing the hydrogen‐bonding interaction in the methoxy analog which showed a lower stability and crystallinity.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Self‐standing, flexible, continuous, and crack‐free covalent‐organic‐framework membranes (COMs) are fabricated via a simple, scalable, and highly cost‐effective methodology. The COMs show long‐term ...durability, recyclability, and retain their structural integrity in water, organic solvents, and mineral acids. COMs are successfully used in challenging separation applications and recovery of valuable active pharmaceutical ingredients from organic solvents.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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