Selective and Sensitive Fluorescent Turn-On Switch for Arsenic(III) Monitoring in Rice by a Nitrogen-Rich Functionalized Covalent Organic Framework

Inorganic As(III), the major form of pollutant of arsenic contamination, tends to accumulate easily in rice, causing serious global health risks. Therefore, it is highly desirable to seek credible methods to achieve efficient management of As³⁺ that can conduct selective and sensitive monitoring. Herein, this work presents a rational design of a covalent organic framework (COF)-based turn-on fluorescent-sensing platform to detect As³⁺. The design concept is proven via framing nitrogen-rich functionalized COF material, Dpy-DhBt: these nitrogen-based sites are highly selective As³⁺ receptors, and the π-connection skeleton is a signal responder. Once As³⁺ is introduced to coordinate with Dpy-DhBt, significant fluorescence turn-on emerged with a clear color change via hindering the photoinduced electron transfer (PET) process. As a sensing platform, the remarkable exhibition of Dpy-DhBt was acquired in facile visualization, favorable sensibility, and real-time answer. The exceptional surface area and porous structure of Dpy-DhBt facilitate superior interaction with As³⁺, which contributes to an ultrafast response time of 10 s. For As³⁺ monitoring, Dpy-DhBt achieved an ultrasensitive detection limit of 7.5 nM. More attractively, Dpy-DhBt has also been prosperously employed to detect As³⁺ in actual rice samples in satisfying recovery. This work reveals great prospects of fluorescent COF for detection of As³⁺ and provides new insights into the research of toxic metal detection in food samples with the easy framing of novel COF materials via clever introduction of chelating sites.