Proton Triggered Fluorescence Switching in Self-Exfoliated Ionic Covalent Organic Nanosheets for Applications in Selective Detection of Anions.

The exfoliation of covalent organic frameworks (COFs) into covalent organic nanosheets (CONs) not only help to reduce fluorescence turn-off phenomena but also provide well-exposed active sites for fast response and recovery for various applications. The present work is an example of rational designing of a structure constructed by condensing triaminoguanidinium chloride (TGCl), an intrinsic ionic linker, with a fluorophore 2, 5-dimethoxyterephthalaldehyde (DA) to produce highly fluorescent self-exfoliable ionic CONs (DATGCl-iCONs). These fluorescent iCONs are able to sense fluoride ions selectively down to ppb level via fluorescence turn-off mechanism. A closer look at quenching mechanism via NMR, zeta potential measurement, lifetime measurement and DFT calculations reveal unique proton triggered fluorescence switching behavior of newly synthesized DATGCl-iCONs.