Recent Advances of Covalent Organic Frameworks in Chemical Sensing

With the rapid development of reticular chemistry, an increasing number of covalent organic frameworks(COFs) have been designed and synthesized over the past decades. Owing to the large surface areas, numerous active sites, and high chemical stability, recent effects gradually were made to investigate the interaction with various small molecules. Among the reported application areas, sensorics is an attractive field, where COFs have exhibited tremendous potential and acquired high- performance sensitivity and selectivity due to their structural merits. In this review, we highlighted the recent progress of COFs as sensors for the detection of various analytes, mainly depending on the analysis of change of fluorescence signals. The basic principles of physics for fluorescence-based sensors were briefly discussed for better understanding of the relationship between structures and functions of COFs. Moreover, we reviewed various classes of small molecule analytes that have been successfully detected by COFs, including explosives, gases, humidity, metal ions, pH, and biological molecules. In this work, we detailedly discussed the components of COFs, functional sites, and sensing performance in each sensing application, aiming to disclose their intrinsic connection. This review also concluded with several issues to be solved and provided the outlook for the future development direction for practical applications.