Dual ligand based 3D Eu(III) MOF as a multifunctional sensor for trace amounts of NACs, Cr3+ and Hg2+ in aqueous medium: synthesis, crystal structure and latent fingerprint detection

A novel 3D luminescent metal-organic framework (MOF) named as [Eu(HPyzdc)(NITA)(H2O)](n) (Cj-3) has been synthesized with the dual ligand approach involving nitro functionalised isophthalic acid (H(2)NITA) and pyrazine based dicarboxylic acid (2,3-H(2)Pyzdc) via a solvothermal method. Analysis of its structure reveals that Cj-3 is composed of tetranuclear secondary building units (SBUs) with uncoordinated carbonyl and hydroxyl groups, which serve as potential recognition sites for interacting with analytes. Cj-3 shows unique luminescence features and is projected for its potential in detecting metal ions (Fe3+ and Cr3+) as well as picric acid (PA) and amine-substituted NACs (nitroanaline). The luminescence experiments show distinct luminescence quenching and enhancement effects, particularly towards nitroaniline (p-NA and o-NA), picric acid (PA), Hg2+ and Cr3+ ions. Cj-3 displays exceptional selectivity and sensitivity towards Cr3+, Hg2+, and PA, along with rapid response times and excellent recyclability. Competitive absorption of excitation energy and electron transfer are probable mechanisms for sensing nitroaromatic compounds, while host-guest interactions are responsible for detecting metal ions. Additionally, visual luminescent test papers based on Cj-3 have been developed which can selectively detect NACs and metal ions. Moreover, Cj-3 can generate latent fingerprints on diverse surfaces, with intricate details observable upon magnification. These findings suggest significant potential for applying Cj-3 as a luminescent MOF in security applications.