Dysprosium(III) Metal-Organic Framework Demonstrating Ratiometric Luminescent Detection of pH, Magnetism, and Proton Conduction.

ABSTRACT

A multifunctional metal-organic framework, (Hdmbpy)[Dy(H2dobdc)2(H2O)]·3H2O (Dy-MOF, H4dobdc = 2,5-dihydroxyterephthalic acid, dmbpy = 4,4'-dimethyl-2,2'-bipyridine), was synthesized and structurally characterized. The metal center DyIII is connected by four carboxyl groups to form the [Dy2(CO2)4] binuclear nodes, which are further interconnected by eight separate H2dobdc2- ligands to form a three-dimensional (3D) framework including hydrophilic triangular channels and abundant hydrogen-bonding networks. Dy-MOF has good stability in aqueous solution as well as in harsh acidic or alkaline solutions (pH range 2.0-12.0). Furthermore, the luminescence signal of Dy-MOF undergoes a visualized color change as the acidity of the solution alters, which is the typical behavior of pH ratiometric probe. At a 100% relative humidity, Dy-MOF exhibits a high proton conductivity σ (1.70 × 10-4 S cm-1 at 303 K; 1.20 × 10-3 S cm-1 at 343 K) based on the proton hopping mechanism, which can be classified as a superionic conductor with σ exceeding 10-4 S cm-1. Additionally, the ferromagnetic interaction and magnetic relaxation behavior are simultaneously achieved in Dy-MOF. Herein, the combination of luminescence sensing, magnetism, and proton conduction in a single-phase 3D MOF may offer great potential applications in smart multitasking devices.