Zr-based Metal-organic Framework [Zr6O4(OH)4(3.2b-ttdc)6] for Effective Mercury (II) Sorption from Water

The objective of this work is to study MOFs with ligands containing thienothiophene groups as linkers and evaluate their practical application as sorbents for mercury removal from water. This evaluation will be compared with MOFs containing 2,6-naphthalenedicarboxylic acid and terephthalic acid linkers. The study of Hg2+ sorption from solutions was carried out by shaking the MOFs (10 mg) with the solution at 25 degrees C for 24 hours. Determination of chemical elements in solutions was performed using an Agilent 8800 triple quadrupole ICP-MS spectrometer (ICP-QQQ) equipped with an octopole reaction-collision cell in a standard configuration. Within 24 hours, 97.8% of Hg2+ ions were removed from the solution, even at an initial Hg2+ concentration as low as 1 mg center dot L-1. An important part of the work was studying the possibility Zr-ttdc regeneration for repeated use. Using iodide solution as a desorbing agent proved more productive, ensuring the desorption of Hg2+ through competitive complex formation due to the high stability constants of the corresponding mercury complexes. With a 0.1 M potassium iodide solution at pH 6.5, 99% of the sorbed mercury was desorbed in one desorption cycle. The efficiency of [Zr6O(4)(OH)(4)([3.2-b]ttdc)6] in adsorbing mercury from aqueous solutions was thoroughly evaluated and compared to [Zr6O(4)(OH)(4)(bdc)6] and [Zr6O(4)(OH)(4)(2.6-ndc)6], which lack sulfur-containing linkers. The findings highlight the potential of functionalized MOFs for water purification as well as application in analytical chemistry for the concentration of mercury. Notably, [Zr6O(4)(OH)(4)([3.2-b]ttdc)6] demonstrated stability in water in a wide pH range, underscoring its promise for diverse environmental chemistry applications.