Porphyrinic zirconium-based MOF with exposed pyrrole Lewis base site as an efficient fluorescence sensing for Hg2+ ions, DMF small molecule, and adsorption of Hg2+ ions from water solution

Abstract

The microporous zirconium-based MOF, as known [PCN-221], was successfully prepared by the solvothermal reaction method using meso-tetra(4-carboxyphenyl) porphyrin (TCPP) as a ligand and used as a fluorescent sensor for sensitive and selective recognition of Hg2+ ions, DMF small molecule, and adsorption of Hg2+ ions. The sensing of [PCN-221] showed a quenching response of Hg2+ ions with a fast fluorescent response rate under <1 ​min. The fluorescence quenching constant is calculated to be 4021.9 ​M-1 by linear correlation for Hg2+ ions in a low concentration range from 0 to 300 ​μM, also the detection limit was calculated to be 0.01 ​μM. Moreover, the prepared [PCN-221] can perform as a fluorescence turn-off sensor for highly sensitive detection of DMF in methanol solution at the line range of 50–1000 ​μM and, the quenching constant is calculated to be 28.231 ​M-1 by the experiment fluorescence titration for a DMF in low concentration, also the detection limit was calculated to be 0.12 ​μM. As well as, the [PCN-221] exhibited a high adsorption of Hg2+ ions in water solution between hazardous heavy metals and compare to other MOFs reported to date. The Hg2+ adsorption process follows pseudo-second-order kinetics, removing 95% of the metals in 30 ​min. Totally, the UV–Vis study provides insight to assist realized the interaction mechanism between [PCN-221] and Hg2+ ions.