Highly selective Fe3+ sensing and proton conduction in a water-stable sulfonate–carboxylate Tb–organic-framework

Abstract

A new 3D porous terbium–organic framework {[Tb₄(OH)₄(DSOA)₂(H₂O)₈]·(H₂O)₈}_n (Tb-DSOA) has been successfully assembled by Tb³⁺ ions and a sulfonate–carboxylate linker disodium-2,2′-disulfonate-4,4′-oxydibenzoic acid (Na₂H₂DSOA). In this metal–organic framework (MOF), tetranuclear terbium clusters can be sensitized by the organic linker to generate the characteristic photoluminescence of Tb^III ions. Noncoordinated sulfonate oxygen atoms functionalize its channels, which act as basic sites leading to highly selective Fe³⁺ ion sensing by luminescence quenching, and also act as hopping sites for proton transfer, resulting in a proton conductivity of 1.66 × 10⁻⁴ S cm⁻¹ at 98% RH. Exceptional water-stability makes this MOF compatible for these applications in aqueous solution.