Dual-Responsive Luminescent Zinc-Based Metal–Organic Framework for Ultrasensitive Detection of Fe ³⁺ and Cr ³⁺ in Aqueous Media

The detection of toxic metal ions in aqueous systems is of utmost importance for environmental security and human welfare. In this work, a zinc-based metal–organic framework (Zn-AIP MOF) was synthesized via a hydrothermal route, employing 5-aminoisophthalic acid as the organic linker. The as-prepared Zn-AIP MOF exhibited strong fluorescence emission, which was effectively utilized for the selective and ultrasensitive detection of Fe 3+ and Cr 3+ ions in an aqueous medium. Upon the addition of Fe 3+ and Cr 3+, the Zn-AIP MOF suspension displayed pronounced fluorescence quenching, attributed to efficient metal–framework interactions and energy/electron transfer processes. Stern–Volmer analysis revealed good linearity, and the detection limits estimated were 0.14 μM for Fe 3+ and 0.24 μM for Cr 3+, indicating the superior performance of the Zn-AIP MOF compared to many other reported MOF-based probes. Importantly, the Zn-AIP MOF demonstrated remarkable selectivity toward Fe 3+ and Cr 3+ even in the presence of competing cations and in a wide range of pH. The most intriguing feature of the Zn-AIP MOF is that it maintains its structural integrity well in an aqueous medium and shows a good recovery percentage in real water samples. These results underscore the promising potential of the Zn- AIP MOF as a robust luminescent probe for on-site water quality monitoring and environmental applications.