Amide-functionalized coordination polymers for fluorescence detection of Fe3+ in aqueous solution

Heavy metal pollution, particularly from Fe³⁺, poses significant environmental and health risks, necessitating sensitive and selective detection methods. This study presents two amide-functionalized coordination polymers (CPs), Zn-CP and Cd-CP, designed for efficient Fe³⁺ sensing in aqueous media. Both CPs exhibit remarkable fluorescence quenching selectivity toward Fe³⁺ due to rich amide functional sites for enhancing sensing capability, achieving low detection limits (LODs) of 3.92/3.35 μM in H₂O and 5.14/4.84 μM in HEPES buffer, surpassing the World Health Organization (WHO) and United States Environmental Protection Agency (USEPA) drinking water standard (5.36 μM). The sensors demonstrate excellent selectivity, anti-interference capability, recyclability, and practical applicability through portable test strips for rapid visual detection. Multiple experiments co‒reveal that fluorescence quenching mechanism arises from competitive energy absorption induced by weak interactions between Fe³⁺ and the N/O-active sites of the amide-decorated frameworks. This work highlights the potential of ligand-engineered CPs for environmental monitoring, offering a robust platform for heavy metal detection with high sensitivity and practical applicability.