Design, synthesis and applications of two-dimensional covalent organic frameworks

Abstract

Two-dimensional materials have drawn a wide variety of interest because of the excellent properties. Two-dimensional covalent organic frameworks (2D COFs) are a class of porous, crystalline organic materials, which are constructed from well-designed organic monomers via covalent bond linkages. The excellent porosity and crystallinity coupled with the brilliant 2D π-conjugated system and π-π stacking columns endow 2D COFs promising properties. With the predesignable topological structures and functionalized monomer units, 2D COFs can be constructed with the characteristics of lower mass density, highly ordered structures, larger surface area and tunable pore size and shapes. Various 2D COFs with versatile properties and specific functions can be also obtained by post-synthesizing, loading of guest molecules and ions, compositing with other carbon-based materials, etc. Additionally, oriented 2D COF monolayers and thin films are also prepared on the substrate surface. Based on the distinct ordered molecular structures and excellent properties, this review further discusses the extensively promising applications of 2D COFs in the fields of gas absorption and storage, catalysis, molecules delivery, energy capacitance and transform, electronics and optoelectronics.