Fast and Selective Adsorption of Methylene Blue from Water Using [BMIM][PF<sub>6</sub>]-Incorporated UiO-66 and NH<sub>2</sub>-UiO-66
Safiyye Kavak, Harun Kulak, H. Mert Polat, Seda Keskın, Alper Uzun
Abstract
Incorporation of ionic liquids (ILs) into metal–organic frameworks (MOFs) offers a broad potential in various applications. However, their applications in wastewater treatment have remained unexplored. Here, we investigate their potential in wastewater treatment and demonstrate a new concept of IL incorporation in ligand-functionalized MOFs, introducing IL/FMOFs. The composites were prepared by incorporating 1-n-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6], into UiO-66 and NH2-UiO-66 and tested for the adsorption of methylene blue (MB) and methyl orange (MO) from aqueous solutions. Data showed that NH2-functionalization and [BMIM][PF6] incorporation improved MB removal performance of UiO-66 by 16- and 48-times, as the capacity increased from 84.8 to 144.7 mg g–1 and 174.1 mg g–1, respectively. When considering both modifications together, [BMIM][PF6]/NH2-UiO-66 was almost 300 times faster than that of UiO-66, and the capacity exceeded 200 mg g–1. Data further suggested that IL incorporation almost doubled MB/MO selectivity because of the strong electrostatic interactions and hydrogen bonding between [PF6]− and MB, and π–π interactions between the [BMIM]+ cation and MB molecules. These results are the first to demonstrate the prospect of combining ligand functionalization with IL incorporation for modifying MOFs, introducing IL/FMOF composites for fast and selective removal of pollutants from wastewater.