Covalent Organic Framework Nanosheets Research Articles

Two-dimensional graphdiyne analogue Co-coordinated porphyrin covalent organic framework nanosheets as a stable electrocatalyst for the oxygen evolution reaction

Employing metalloporphyrin as monomer is an effective strategy to overcome the drawback of graphdiyne in electrocatalytic process. The Co–N4 active centers, expanded pores, and conjugated structure altogether endow the Co-PDY with excellent OER catalytic performance.

Graphene oxide membranes with an ultra-large interlayer distance through vertically grown covalent organic framework nanosheets

A GO-based membrane with an ultra-large interlayer distance of 42.2 nm is fabricated via intercalating nanoheterojunction into adjacent GO nanosheets, which exhibits superior morphological stability, and can be used to separate oil-in-water emulsion.

Constructing channel-mediated facilitated transport membranes by incorporating covalent organic framework nanosheets with tunable microenvironments

Facilitated transport membranes with tunable microenvironments are fabricated via incorporation of metal-ion loaded COF nanosheets for gasoline desulfurization.

Restriction of Molecular Rotors in Ultrathin Two-Dimensional Covalent Organic Framework Nanosheets for Sensing Signal Amplification

Covalent organic frameworks (COFs) have emerged as promising crystalline porous materials with well-defined structures, high porosity, tunable topology, and functionalities suitable for various applications. However, studies of few-layered ultrathin two-dimensional (2D) COF nanosheets, which may lead to unprecedented properties and applications, are still limited. Herein, we report the targeted synthesis of three azine-linked and imine-linked 2D COFs named NUS 30–32 using monomers containing aggregation-induced emission (AIE) rotor-active tetraphenylethylene (TPE) moieties, affording micro- and meso-dual pores in NUS-30 and NUS-32 and triple pores in NUS-31. For the first time, we demonstrate that these isostructural bulk COF powders can be exfoliated into ultrathin 2D nanosheets (2–4 nm thickness) by a temperature-swing gas exfoliation approach. Compared with TPE monomers and COF model compounds, the AIE characteristic of NUS 30–32 nanosheets is distinctly suppressed because of the covalent restriction o...

Growth of high-quality covalent organic framework nanosheets at the interface of two miscible organic solvents.

Stronger covalent bonds between monomers, relatively more complex growth processes (polymerization, crystallization, assembly, etc.) and π-π stacking interactions between adjacent layers make it extremely difficult to obtain highly ordered crystalline 2D covalent organic framework (COF) nanosheets. So more effective solutions have to be developed to push the methods reported so far beyond their inherent limitations. Herein, we report the first example of growing high-quality 2D COF nanosheets (NS-COF) at the interface of two miscible organic solvents. The novel approach, which is named as a buffering interlayer interface (BII) method, can be achieved by simply adding a low-density solvent interlayer, as a buffer layer, between the two miscible main solvents based on the self-propelled directed motion of the interface driven by the density differences among the solvents involved. The as-synthesized NS-COF exhibits a super-large size and a relatively regular shape with a smooth surface, which have not been observed before. The proposed strategy offers a facile and effective approach for growing well-structured 2D COF nanosheets and also other kinds of nanosheets.

High Conductive Two-Dimensional Covalent Organic Frameworks for Anodes of Lithium-Ion Batteries

Two-dimensional covalent organic framework (COF) nanosheets based on 5,10,15,20-tetra(4-thiophenephenyl)- porhyrin (TThPP) featuring high conductivity were synthesized using an in-situ chemical oxidative polymerization method. Here, we show for the first time a 2D COF used as the anode for lithium-ion batteries. When used as anode material for lithium ion batteries, the TThPP anode displayed good lithium-ion storage properties with high specific capacities, excellent rate performances, and long cycle lives compared with that of graphitic (372 mAh g−1) and other organic anodes. The reversible capacity is up to 666 mAh g−1. The TThPP also exhibited high energy and power densities of 48.44 Wh kg−1 and 700.36 W kg−1 respectively when used as the anode of a hybrid capacitor. The unique nanosheet morphology of the TThPP anode films provide efficient adsorption sites for Li atoms, short-ended paths for the fast lithium-ion diffusion, and open nanopores for holding electrolyte that contribute to the excellent electrochemical performance.

Ultrathin Two-Dimensional Covalent Organic Framework Nanosheets: Preparation and Application in Highly Sensitive and Selective DNA Detection.

The ability to prepare ultrathin two-dimensional (2D) covalent organic framework (COF) nanosheets (NSs) in high yield is of great importance for the further exploration of their unique properties and potential applications. Herein, by elaborately designing and choosing two flexible molecules with C3v molecular symmetry as building units, a novel imine-linked COF, namely, TPA-COF, with a hexagonal layered structure and sheet-like morphology, is synthesized. Since the flexible building units are integrated into the COF skeletons, the interlayer stacking becomes weak, resulting in the easy exfoliation of TPA-COF into ultrathin 2D NSs. Impressively, for the first time, the detailed structural information, i.e., the pore channels and individual building units in the NSs, is clearly visualized by using the recently developed low-dose imaging technique of transmission electron microscopy (TEM). As a proof-of-concept application, the obtained ultrathin COF NSs are used as a novel fluorescence sensing platform for the highly sensitive and selective detection of DNA.

Two-Dimensional Covalent Organic Framework (COF) Membranes Fabricated via the Assembly of Exfoliated COF Nanosheets.

Exceptionally homogeneous and ultrathin COF membranes were successfully fabricated using exfoliated COF nanosheets with uniform perforations as membrane building blocks. The COF membranes showed highly permeable performance due to the ultrafast molecular diffusion through the perforations of the COF nanosheets and the excellent thermal stability due to the robust covalent bonds in the framework.