Water-assisted proton conductivity of two lanthanide-based supramolecules

Abstract

By using a multifunctional organic ligand, 2-(3-benzoylthioureido)ethanoic acid (H₃L), an N-containing ligand, 1,10-phenanthroline (Phen), and two kinds of lanthanides (Gd(III) and Ho(III)), two binuclear supramolecules [Gd₂(η²-H₂L)₂(H₂L)₂(Phen)₂(NO₃)₂(CH₃OH)] (1) and [Ho₂(η²-H₂L)₂(H₂L)₂(Phen)₂(NO₃)₂(CH₃OH)] (2) were prepared. 1 and 2 are isostructural 3D supramolecular frameworks supported by intermolecular H-bonds and π–π interactions. Both complexes demonstrate excellent water and thermal stability, which meets the requirements of the proton conductivity study. The highest proton conductivities are 0.87 × 10⁻⁴ and 1.58 × 10⁻⁴ S cm⁻¹ for 1 and 2 at 98% RH and 100 °C, respectively, which can be comparable to those of some reported lanthanide-based MOFs showing great potential as proton conductive materials.