Fluorescent Sensors Based on Covalent-Organic Frameworks

Covalent-organic frameworks (COFs) are categorized as a new emerging class of porous materials, which have drawn considerable attention due to fascinating structural features such as controlled porosity, structural predictability, changeable pore size/volume, and high thermal and chemical stability. Due to multiple similar binding sites over the whole extended frameworks, COFs have proved fascinating materials for developing fluorescent sensors. Among all the investigated application areas, sensorics is one of the interesting fields where COFs have unveiled incredible potential and acquired high performance sensitivity and selectivity due to unique structural properties. The large specific surface area promotes guest molecules interacting fully with the recognition site to improve sensitivity. Development of luminescent active materials is found to be challenging due to the π-π contacts of COFs, which trigger a quenching effect. In this regard, efforts have been made to design efficient luminescent materials by introducing functional groups in COF-monomers. This chapter offers design, synthesis, and analytical applications of fluorescent COFs in addition to the exploration of luminescence characteristics, particularly in explosive sensing, humidity sensing, pH detection, bio-sensing, gas sensing, and metal ion sensing. Notable challenges and future developments of COFs pertaining to their production and sensing applications are also discussed.