Stable metal–organic frameworks modulated by doping Tb3+ for multi-hazard detection and capture†
Abstract
Considering the discharge of radioactive and non-radioactive effluents during the mining process, we report on a study that proposes to use optical sensing for the detection and monitoring of pollutants. This is realized by doping of Tb3+ ions in a metal–organic framework, namely UiO-66-(COOH)2, and taking advantage of the host–guest interactions which allow analyte molecules to be pre-concentrated within the pores of the material, thus influencing the light absorption and emission profile of Tb3+ ions. Concentration-dependent spectroscopy analysis shows that Tb@UiO-66-(COOH)2 has a luminescence turn-off behaviour which is more sensitive in the presence of Ni2+ and UO22+ ions as compared with monovalent (Ag+), bivalent (Co2+), trivalent (Fe3+), and tetravalent (Sn4+) cations. The relative luminescent intensity (I0/I) as a function of the concentrations of both Ni2+ and UO22+ shows a linear response in a broad concentration range (10−7–10−3 M). The limit of detection (LOD) for Ni2+ is 5.7 μg L−1, which is lower than the allowable concentration limit (0.02 mg L−1) defined by the national environmental quality standard of surface water GB 3838. The LOD for UO22+ is 0.02 μg L−1, far below the World Health Organization maximum standards for potable water (30 μg L−1). Therefore, Tb@UiO-66-(COOH)2 enables the detection of these ions with high sensitivity. Notably, the optical response measured at low concentrations of Ni2+ and UO22+ is not affected even in the presence of interfering metallic ions. These results demonstrate for the first time that Tb@UiO-66-(COOH)2 is a versatile multi-hazard sensor for the detection of non-radioactive and radioactive elements. It also opens opportunities for the selective adsorption and extraction of UO22+ due to the high-stability functionality of Tb@UiO-66-(COOH)2.