Mixed-linker Zr-based metal-organic framework as a highly sensitive probe for ultrafast and selective detection of fluoride ions

Abstract

The application of mixed-linker strategies in the synthesis of metal-organic frameworks (MOFs) has garnered considerable interest owing to their potential as fluorescent sensors, attributed to their facile synthesis and incorporation of diverse functional ligands. In this study, we designed and synthesized a novel fluorescent Zr-based MOFs, denoted as MOF-808-NH₂, through the post-synthetic modification of 2-amino terephthalic acid (BDC-NH₂) on coordinatively unsaturated Zr sites, thereby preserving the structural stability of the parent framework. The MOFs exhibited exceptional turn-on fluorescence in aqueous solutions containing fluoride ions (F⁻). The interaction between the-NH₂ groups on MOF-808-NH₂ and F⁻ facilitated the formation of hydrogen bonds, significantly enhancing the fluorescence emission intensity of BDC-NH₂ at 450 nm and inducing a blue shift in the fluorescence emission peak, enabling the specific recognition of F⁻ even in the presence of various anionic interferences. Notably, MOF-808-NH₂ demonstrates an ultrafast response time (within 30 s), a high detection sensitivity with a limit of detection of 1.56 μM, and remarkable selectivity and anti-interference properties with pronounced fluorescence emission against a dark background. Furthermore, MOF-808-NH₂ retained outstanding thermal, mechanical, and chemical stabilities, underscoring its potential for practical applications in selective F⁻ detection.