A hydrolytically stable europium–organic framework for the selective detection of radioactive Th4+ in aqueous solution

Abstract

Thorium is not only a promising candidate for developing next generation nuclear fuel but also a potential radioactive contaminant. Efficient detection of thorium contamination is critically important in both nuclear science and environmental protection. We present here a 3D luminescent europium organic framework [Eu₂(FDC)₃(DMA)₂]·4H₂O (compound 1), which exhibits excellent hydrolytic stability and features highly selective detection capacity (K_SV = 6.68 × 10⁴) towards radioactive Th⁴⁺ ions among the selected monovalent, divalent and tervalent metal ions in aqueous solution. The detection limit of the material towards Th⁴⁺ is 3.49 × 10⁻⁵ mol L⁻¹ which is close to the WHO standard. The detection capability and the sensing mechanism were demonstrated by Th⁴⁺ uptake kinetics, energy-dispersive spectroscopy mapping, absorption spectroscopy, luminescence lifetime, and competitive adsorption measurements. Compound 1 represents a rare case of a MOF based Th⁴⁺ probe.