Conductive lithium-ion functionalized covalent organic framework modified electrode for enhanced electrochemical response to sulfamethoxazole

As a broad-spectrum antibacterial sulfonamide antibiotic, sulfamethoxazole (SMZ) is widely used in human disease treatment, veterinary medicine and aquaculture. However, its misemployment and incomplete metabolism pose threats to ecological balance and human health. Due to the fast response speed, low cost and high sensitivity, electrochemical sensing technology has attracted much attention in the field of pollutant detection. This paper designed a novel and simple electrochemical detecting platform for the sensitive determination of SMZ in water samples. A lithium ion-grafted COF (Li-COF) was obtained through a simple cation exchange process between β-ketoamine-linked porous covalent organic framework (TS-COF) synthesized through the condensation reaction of 1,3,5-triformylphloroglucinol (TFP) and sulfonic-functionalized monomer 2-sulfonic-1,4-benzenediamine (Pa-SO 3 H) and lithium acetate. Highly π-conjugated structure of TS-COF provided excellent electronic conductivity while incorporation of Li + ion into the COF significantly enhanced charge mobility, and improved ionic conductivity, thereby accelerating electron transfer kinetics of SMZ at the sensing interface and enhancing electrochemical response of the analyte molecule. At the same time, presence of Li + and -SO 3 H at the sensing interface further enhanced the specific interaction of the resulting sensor with the target analyte for improved analytical selectivity. As a result, the constructed electrochemical sensor exhibited a good potential to quantify SMZ in tap water and Yellow River water with a wide linear range (0.2 ∼ 180 μM) and a low detection limit (0.015 μM).