A water-stable terbium-MOF sensor for the selective, sensitive, and recyclable detection of Al3+ and CO32− ions

Abstract

A terbium metal–organic framework associated with mixed 4-(pyridin-3-yloxy)-phthalic acid (H₂ppda) and oxalic acid (H₂ox) has been synthesized under solvothermal conditions, namely [Tb(ppda)(ox)_0.5(H₂O)₂]_n (1). Compound 1 is constructed of 1D binuclear [Tb(ppda)]₂ chains and is further connected by ox²⁻ ligands, exhibiting a 2D layered structure. It is worth noting that compound 1 exhibits excellent fluorescence stability over a pH range from 2 to 13 in aqueous solution. Interestingly, compound 1 can detect Al³⁺ ions with high selectivity and sensitivity among diverse inorganic cations in aqueous solution. In addition, compound 1 is also a highly selective sensing material for CO₃²⁻ ions without interference from other common anions. Therefore, compound 1 is a promising sensor with a fast response time and low limits of detection for simultaneously detecting Al³⁺ and CO₃²⁻ ions, at 5.66 μM for Al³⁺ ions and 0.38 μM for CO₃²⁻ ions. Compound 1 displays the lowest limit of detection for CO₃²⁻ ions using a fluorescent MOF sensor reported to date. The luminescence quenching mechanisms for the different analytes are further explored in detail.