Recent advances of covalent organic frameworks for solid-phase microextraction

Covalent organic frameworks (COFs) are one booming class of porous materials that are assembled through covalent bonds. Owing to the excellent properties including three-dimensional frameworks, large specific surface, porous structure, multiple functional groups, good absorptivity, flexible design about various COFs, it has been introduced in sample preparation and some efficient COF coatings have been developed for solid-phase microextraction (SPME). COFs can be synthesized by different methods, and they also can be functionalized or modified for the regulation of their properties, so as to improve extraction performance. These COF materials presented good extraction effect to organic pollutants from diverse samples. This review paper focuses on the classification of COFs and their applications in SPME (direct immersion fiber SPME, headspace fiber SPME, and other SPME) as well as the extraction mechanism (π-π stacking, hydrogen bonding, hydrophobic, hydrophilic and electrostatic interactions, etc.) for various analytes in recent five years. Based on the flexible design and rich functionalization, COFs have large potential applications in sample preparation, and an outlook for current challenges and future trends about the development of COFs for SPME is also given.