Covalent organic frameworks: Design, synthesis, characterization, and applications

Covalent organic frameworks (COFs) have emerged as an interesting class of crystalline porous materials with desirable properties (such as highly ordered porosity, structural versatility, high chemical and thermal stabilities, and facile surface modification) and a broad range of potential applications. This critical review is aimed at providing insight into design strategies and synthetic methodologies for COFs. Unlike previous reviews on COFs, this article also focuses on the characterization of COFs, which is important for understanding the physical and chemical properties of COFs that are essential for practical applications. Furthermore, this review highlights the applications of COFs in various fields, including catalysis, photovoltaic devices, sensors, supercapacitors, wastewater treatment, biomedicine, chromatographic and spectroscopic analyses, and gas separation and storage. Lastly, perspectives on future directions and challenges associated with COFs are provided.