Luminescence

Chemistry

Optoelectronics

Photochemistry

Fluorescence

Alkyl

Physics

Chloride

Hydrazone

Fluoride

Organic chemistry

Covalent bond

Halogen

Quantum mechanics

Deprotonation

Inorganic chemistry

Combinatorial chemistry

Quenching (fluorescence)

Bromide

Iodide

Journal of the American Chemical Society

Covalent organic frameworks (COFs) offer ordered π structures that are useful for developing light-emitting materials. However, most COFs are weak in luminescence. Here we report the conversion of less emissive COFs into light-emitting materials via a pinpoint surgery on the pore walls. Deprotonation of the N-H bond to form an anionic nitrogen species in the hydrazone linkage can eliminate the nitrogen-related fluorescence quenching pathway. The resulting COF enhances the fluorescence in a linear proportion to the progress of deprotonation, achieving a 3.8-fold improved emission. This pinpoint N-H cleavage on the pore walls can be driven only by the fluoride anion while other halogen anions, including chloride, bromide, and iodide, remain inactive, enabling the selective fluorescence switch-on sensing of the fluoride anion at a ppb level.

Light-Emitting Covalent Organic Frameworks: Fluorescence Improving via Pinpoint Surgery and Selective Switch-On Sensing of Anions