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

Abstract

The exfoliation of covalent organic frameworks into covalent organic nanosheets (CONs) not only helps to reduce fluorescence turn-off phenomena but also provides 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 (TG Cl ), an intrinsic ionic linker, with a fluorophore, 2, 5dimethoxyterephthalaldehyde (DA), to produce highly fluorescent selfexfoliable ionic CONs (DATG Cl -iCONs). These fluorescent iCONs are able to sense fluoride ions selectively down to the ppb level via the fluorescence turn-off mechanism. A closer look at the quenching mechanism via NMR, zeta potential measurement, lifetime measurement, and density functional theory calculations reveals unique proton-triggered fluorescence switching behavior of newly synthesized DATG Cl -iCONs.

The Exfoliation of Crystalline Covalent Triazine Frameworks by Glycerol Intercalation

“…So far, many efforts have been devoted to developing a variety of exfoliation methods to produce CONs, including mechanical delamination, [ 4,13 ] chemically oxidative exfoliation, [ 1,14–17 ] and self‐exfoliation. [ 18–21 ] However, these exfoliation methods more or less cause structural damage.…”

Two‐Dimensional Metal‐Organic Frameworks and Covalent Organic Frameworks

“…Singh et al . [ 133 ] prepared the highly fluorescent self‐exfoliating ion CON (DATG Cl ‐iCONs) by condensing triaminoguanidine chloride (TG Cl ) with the fluorophore 2,5‐dimethoxyterephthalaldehyde (DA). These fluorescent iCONs could selectively detect fluoride ions down to the ppb level through a fluorescence shutdown mechanism (shown in Figure 13).…”

Nitrogen-rich covalent organic frameworks: a promising class of sensory materials

“…65b). 114 The addition of Finto the cationic sensor causes great fluorescence quenching with a detection limit of 5 ppb level. A unique property of the guanidinium linker is its ability to donate proton (in the presence of Fions) and abstract it again (by adding HCl).…”