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

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.