Three new super water-stable lanthanide–organic frameworks for luminescence sensing and magnetic properties

Abstract

Three new lanthanide compounds, [Ln(HL)(H₂O)₃]_n (1-Ln) (Ln = Eu, Tb and Dy), with isostructural structures have been constructed by a semi-rigid ligand 1-(3,5-dicarboxylatobenzyl)-3,5-pyrazole dicarboxylic acid (H₄L) and Ln(NO₃)₃·6H₂O using the solvothermal method. Three compounds show two-dimensional (2D) grid layer-stacking frameworks with interlayer channels decorated with carboxylic acid groups. 1-Eu exhibits excellent water stability and strong luminescence. Importantly, as a probe for sensing different metal ions and anions, 1-Eu shows highly specific recognition to Fe³⁺, CrO₄²⁻ and Cr₂O₇²⁻ ions. Meanwhile, the mechanisms of luminescence quenching were studied, and antiferromagnetic exchange interactions existed in 1-Dy.