Selective and recyclable tandem sensing of PO43− and Al3+ by a water-stable terbium-based metal−organic framework

Abstract Herein, a luminescent water-stable terbium-based metal−organic framework (MOF) {[Tb(Cmdcp)(H2O)3]2(NO3)2·5H2O}n (1, H3CmdcpBr = N-carboxymethyl-(3,5-dicarboxyl)pyridinium bromide) has been synthesized and used for the recyclable sensing of PO43– and Al3+ in tandem. MOF 1 acts as a fluorescent sensor for PO43– by the luminescence “turn-off” mechanism with high selectivity over other anions, such as F-, Cl−, Br−, I−, NO3−, H2PO4-, HSO4-, HCO3-, HSO3-, SO42-, CO32- and HPO42-. The formed PO43–@1 complex further acts as the Al3+ sensor with the luminescence “turn-on” mechanism, also with high selectivity over diverse inorganic cations of Fe2+, Mn2+, Co2+, Ni2+, Hg2+, Na+, K+, Li+, Ag+, Mg2+, Ca2+, Cd2+, Pb2+, Cu2+, and Zn2+. The detection process for both PO43- and Al3+ can be directly observed with naked eyes under the UV light at 365 nm. The detection limits for PO43- and Al3+ are 1.1 μM and 6.6 μM, respectively. Such a sensing cycle is further transferable to urine and serum samples with a satisfactory near-quantitative recovery, highlighting its good potential in biologically relevant applications.