Luminescent Covalent Organic Frameworks for Biosensing and Bioimaging Applications.

Luminescent covalent organic frameworks (LCOFs) have attracted significant attention due to their tunability of structures and photophysical properties at molecular level. LCOFs are built to highly ordered and periodic 2D or 3D framework structures through covalently assembling with various luminophore building blocks. Recently, the advantages of LCOFs including predesigned properties of structure, unique photoluminescence, hypotoxicity and good biocompatibility and tumor penetration, broaden their applications in biorelated fields, such as biosensing, bioimaging, and drug delivery. A specific review that analyses the advances of LCOFs in the field of biosensing and bioimaging is thus urged to emerge. Here the construction of LCOFs is reviewed first. The synthetic chemistry of LCOFs highlights the key role of chemical linkages, which not only concrete the building blocks but also affect the optical properties and even can act as the responsive sites for potential sensing applications. How to brighten LCOFs are clarified through description of structure managements. The ability to utilize the luminescence of LCOFs for applications in biosensing and bioimaging is discussed using state-of-the-art examples of varied practical goals. A prospect finally addresses opportunities and challenges the development of LCOFs facing from chemistry, physics to the applications, according to their current progress.