Metal–Organic-Framework-Based Chemosensor for Ultrafast and Ultrasensitive Detection of Pd<sup>2+</sup> Ions in Water, Real Specimens, and Test Strips
Pranam Chakraborty, Abhijeet Rana, Srijan Mukherjee, Shyam Biswas
Abstract
A new ultrasensitive and ultrafast Al(III) metal–organic-framework (MOF)-based probe (1) was constructed to detect Pd2+ ions. Extremely selective recognition of Pd2+ ion was demonstrated by the guest-free compound 1 (called 1′) using a fluorescence signal. The quenching in the fluorescence signal was observed due to the weak interaction between the linker alkyne−π bond and Pd2+. The mechanism of isophthalic alkyne−π and Pd2+ interaction was systematically examined with the help of isothermal titration calorimetry (ITC), X-ray photoelectron spectroscopy (XPS), and UV–vis spectroscopy. The response time of the MOF for sensing of Pd2+ was 30 s, which is the lowest response time for MOF-based Pd2+ sensing to date, with an ultralow detection limit (102 nM) and Stern–Volmer constant (4.39 × 103 M–1), evidencing the outstanding ability to sense Pd2+ ion by this probe. The Pd2+ detection limit falls among the lowest values. Activated MOF (1′) also showed considerable recyclability up to five steps with a constant sensing ability. In different water resources (Milli-Q water, lake water, river water, and tap water), the probe also showed excellent sensing ability. A paper-strip device was developed for the applicability of our material for the real field sensing application of Pd2+. The relevance of 1′ is not only up to Pd2+, but it could also sense palladium in other possible oxidation states.