Journal of Nanosciences: Current Research

Dual Sensing of Copper Ion and Chromium (VI) Oxyanions by Benzotriazole Functionalized UiO-66 Metal-Organic Framework

Abstract

Aasif Helal

Metal−Organic, Frameworks (MOFs) with porous structure and high surface area has been extensively used for the capture and storage of carbon dioxide, hydrogen and methane. The finely tuned pores with functional sites have enabled us to use MOF in developing materials for separations of small and large molecules, sensing of different analytes, drug delivery, carbon dioxide conversion and heterogeneous catalysis. These pore environments can be engineered by using functionalized linkers for different potential applications. Low concentration of copper effects the enzyme activity owing to the redox-active nature while excessive accretion of copper cause damage to the liver and kidney, hepatolenticular degeneration (Wilson’s disease), Alzheimer’s diseases, Menkes syndrome, neutropenia and myelopathy. Moreover, chromate ion can cause allergic reaction in human and prolonged exposure results in chrome ulcer, contact dermatitis, and irritant dermatitis. In this work a new dual chemosensor UiO-66-NH-BT (BT=1-methylenebenzotriazole) based on the UiO-66 (University of Oslo) framework, containing benzotriazole functionalized dicarboxylate struts was synthesized and characterized. This isoreticular Metal-Organic Framework (MOF) was found to be a very selective and ultrasensitive for copper ion and chromium oxyanions in aqueous media. It showed a detection limit of 16.9 ppb (0.266 mM) for Cu²⁺ ion, 280 ppb (1.3 mM) for Cr₂O7^2- and 47.7 ppb (0.411 mM) for CrO₄^2- anions. The quenching constants (Ksv) for Cu²⁺, Cr₂O7^2-, CrO₄^2- was found to be 1.1x10⁵, 3.9x10³, and 6.7x10³ respectively. The covalently bonded benzotriazole moiety with the UiO-66 framework not only produces an emission peak at 491 nm but also act as an intrinsic binding site for both cations and anions. The nature of the coordinative interaction between the analytes and the UiO-66-NH-BT has also been elaborated with the help of ICP and FTIR. This chemosensor also demonstrated a regenerative property without the loss in performance for five consecutive cycles.