Query: COFs

title: Recent development of covalent organic frameworks (COFs) synthesis and catalytic (organic electro photo) applications
abstract: Covalent organic frameworks (COFs) are one of the most important and dynamic members of the porous organic materials and are constructed using reticular chemistry with the building blocks being connected via covalent bonds. Due to their fascinating properties such as large surface area; structural versatility; effortless surface modification; and high chemical stability, COFs are being widely deployed in catalytic; sensing; adsorption; gas storage; and many other valuable applications. This review summarizes selected and most recent espoused synthetic methodologies for their assembly including the formation of magnetic COFs. Potential insights in the field of catalysis; electrocatalysis; and photocatalysis, where COFs can serve as excellent platforms for supporting catalytic species, are also illustrated.

title: Bulk COFs and COF nanosheets for electrochemical energy storage and conversion.
abstract: Covalent organic frameworks (COFs) as an emerging class of crystalline porous materials have received much attention due to their tunable porosity, modifiable skeletons, and atomically precise structures. Besides, COFs can provide multiple high rate charge carrier transport (electron, hole, and ion) pathways, including conjugated skeletons, overlapped p electron clouds among the stacked layers, and open channels with a variable chemical environment. Therefore, they have shown great potential in electrochemical energy storage (EES) and conversion (EEC) However, in bulk COFs, the defects always impede charge carrier conduction, and the difficulties in reaching deep buried active sites by either electrons or ions lead to limited performance. To overcome these obstacles, numerous research studies have been carried out to obtain COF nanosheets (NSs) This review first describes the preparation strategies of COF NSs via bottom up and top down approaches. Then, the applications of bulk COFs and COF NSs in EES and EEC are summarized, such as in batteries, supercapacitors, and fuel cells. Finally, key challenges and future directions in these areas are discussed.

title: Surface nano traps of Fe0/COFs for arsenic(III) depth removal from wastewater in non ferrous smelting industry
abstract: The chemical valence state of arsenic changed with the redox state which influenced by the aquatic environmental factors. One challenge for arsenic control is the depth removal of trivalent arsenic (As(III) from wastewater from non ferrous industries. Immobilization of As(III) could be realized through an enhanced adsorption method. In this study, zero valent iron (Fe0) nanoparticles assembled on porous covalent organic frameworks (COFs) were selected as "nanotraps" for arsenic ions capture and surface stabilization. Fe0/TAPB PDA COFs composites were synthesized through an in situ growth method. The porous surface of COFs offered efficient spaces for Fe0 loading as well as the reaction sites. The results showed that Fe0/COFs exhibited a better performance in As(III) adsorption than pure nZVI (nanoscale zero valent iron) and the maximum adsorption capacity reached to 135.78 mg/g. In addition, the effects of co existed anions and metal ions were also investigated. Such a novel composite exhibited a huge potential for heavy metals purification in future study.

title: Synthesis of robust MOFs@COFs porous hybrid materials via aza Diels Alder reaction: towards high performance supercapacitor materials.
abstract: Metal organic frameworks (MOFs) and covalent organic frameworks (COFs) attracted enormous attention in recent years. Recently, MOF@COF are emerging as hybrid architectures combining the unique features of the individual components to enable the generation of materials displaying novel physicochemical properties. Herein we report an unprecedented use of aza Diels Alder cycloaddition reaction as postsynthetic modification of MOF@COF LZU1, to generate aza MOFs@COFs hybrid porous materials with extended p delocalization. A a proof of concept, the obtained aza MOFs@COFs is used as electrode in supercapacitors displaying specific capacitance of 20.35 uF cm 2 and high volumetric energy density of 1.16 F cm 3 Our approach of postsynthetic modification of MOFs@COFs hybrids implement rational design for the synthesis of functional porous materials and expands the plethora of promising application of MOFs@COFs hybrid porous materials in energy storage applications.

title: Recent advances in covalent organic frameworks (COFs) as a smart sensing material.
abstract: As a newly emerging kind of porous material, covalent organic frameworks (COFs) have drawn much attention because of their fascinating structural features (e.g. divinable structure, adjustable porosity and total organic backbone) Since the seminal work of Yaghi and co workers reported in 2005, the COF materials have shown superior potential in diverse applications, such as gas storage, adsorption, optoelectronics, catalysis, etc. Recently, COF materials have shown a new trend in sensing fields. This critical review briefly describes the synthesis routes for COF powders and thin films. What's more, the most fascinating and significant applications of COFs in sensing fields including explosive sensing, humidity sensing, pH detection, biosensing, gas sensing, metal ion sensing, and other substance sensing are summarized and highlighted. Finally, the major challenges and future trends of COFs with respect to their preparation and sensing applications are discussed.

title: Covalent organic frameworks (COFs) for environmental applications
abstract: 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.

title: Secondary growth of covalent organic frameworks (COFs) on porous substrates for fast desalination
abstract: Covalent organic frameworks (COFs) has emerged as a highly promising platform material for the manufacturing of molecule separating membranes. However, COF membranes are predominantly used in the separation of dyes from water or organic solvents and there are very few reports on COF enabled membranes for desalination. In this work, the secondary growth approach based on unidirectional diffusion synthesis is developed to grow continuous thin films of a COF with an intrinsic pore size of 0.8 nm on macroporous substrates to prepare COF membranes for desalination. The amino modified polymer microfiltration substrate is fixed in a diffusion cell to separate the oil phase containing the aldehyde precursor (1,3,5 triformylphloroglucinol, Tp) and the aqueous phase containing both the amino precursor (hydrazine, Hz) and the catalyst. Because of the immiscible bi phase solutions and the high molar ratio of Hz to Tp, the unidirectional diffusion of Hz molecules in the pore channel of the substrate is achieved and the polycondensation between the two precursors occurs at the phase interface. The unidirectional diffusion synthesis is sequentially performed for two times and the secondary growth is essential to ensure the formation of a defect free, continuous thin film of COF (TpHz) on the top surface of the substrate. Cladding COF coatings are also formed along the skeleton in the near surface region of the substrate. Such an asymmetric structure ensures both a good permselectivity and a strong adhesion between the grown COF layers and the substrates. The continuous COF thin film grown on the substrates serves as the selective layer, and the COF membrane prepared under the optimized condition exhibits an appreciable Na2SO4 rejection of 58.3% and a water permeance of 40.5 Lm 2h 1MPa 1 which are ten times higher than other membranes with similar rejections. This study not only demonstrates the potential of COFs in desalination but also showcases an efficient strategy to grow continuous thin films of COFs on porous substrates which are desired in diverse applications.

title: MOF@COFs with Strong Multi Emission for Differentiation and Ratiometric Fluorescence Detection.
abstract: Aggregation caused quenching (ACQ) is often observed in covalent organic frameworks (COFs) for their low emission. Here, we propose that limited COF layers form on UiO 66 to eliminate the ACQ by the formation of UiO@COF composites. UiO 66 is selected because this metal organic framework (MOF) is easily prepared in nanosize with Zr4+ ion and 2 aminoterephthalic acid (BDC NH2) High affinity of Zr4+ ion to phosphate species improves sensing selectivity. The surface NH2 reacts 2,4,6 triformylphloroglucinol (Tp) to integrate COF1 and COF2, which are prepared with Tp and phenylenediamine or tetraamino tetraphenylethylene, respectively. Hydrogen bond formed between hydroxyl group in Tp and imine nitrogen realizes excited state intramolecular proton transfer, so multi emission is observed from the enol and keto states of the COFs and UiO 66 at 360, 470 and 613 nm for UiO@COF1 and 370, 470, and 572 nm for UiO@COF2. When added phosphate ion in the composites, the emissions from the COFs keep stable, while that from UiO 66 is enhanced. However, adenosine 5' triphosphate (ATP) improves the emissions from UiO 66 and COF's enol state, but that from keto state keeps stable. The differentiation and ratiometric fluorescence detection of ATP and phosphate ion are therefore realized with the multi emission, the affinity of Zr4+ ions, and the structural selectivity of the COFs. Thus, UiO@COF is a novel strategy to integrate multi emission, affinity, and structural selectivity to improve sensing performance for differentiation and ratiometric detection.

title: Proximity Effect in Crystalline Framework Materials: Stacking Induced Functionality in MOFs and COFs
abstract: Metal organic frameworks (MOFs) and covalent organic frameworks (COFs) consist of molecular building blocks being stitched together by strong bonds. They are well known for their porosity, large surface area, and related properties. The electronic properties of most MOFs and COFs are the superposition of those of their constituting building blocks. If crystalline, however, solid state phenomena can be observed, such as electrical conductivity, substantial dispersion of electronic bands, broadened absorption bands, formation of excimer states, mobile charge carriers, and indirect band gaps. These effects emerge often by the proximity effect caused by van der Waals interactions between stacked aromatic building blocks. Herein, it is shown how functionality is imposed by this proximity effect, that is, by stacking aromatic molecules in such a way that extraordinary properties emerge in MOFs and COFs. After discussing the proximity effect in graphene related materials, its importance for layered COFs and MOFs is shown. For MOFs with well defined structure, the stacks of aromatic building blocks can be controlled via varying MOF topology, lattice constant, and by attaching steric control units. Finally, an overview of theoretical methods to predict and analyze these effects is given, before the layer by layer growth technique for well ordered surface mounted MOFs is summarized.

title: Small amount COFs enhancing storage of large anions
abstract: Various alternatives of Li ion batteries (LIBs) have been developed due to the scarcity of Li resources and growing demand of LIBs. However, most of these candidates are suffering the challenges of sluggish intercalations of large sized ions (e.g. Na+ K+ or anions etc. leading to low capacity, poor cycleability and particularly performance decay at high rate. Herein, we report the precise synthesis of a novel conjugated polymer (polypyrene sulfide, PPYS) and its application in storage of anions. Furthermore, we propose a novel concept that the electropositive covalent organic frameworks (COFs) could be able to adsorb anions by electrostatic attractions and thereby facilitate the transport of anions. This novel concept for enhancing the intercalation kinetics of large sized anions is demonstrated by using the PPYS cathodes as proof of concept. After addition of small amount COFs, the capacity, the rate capability and the cycleability of PPYS are improved impressively. Such strategy can be expected to be universal to other redox polymers and may be also applicable to enhance the transport of other large sized ions in multifunctional applications. These results will also extend the application fields of COFs.