Sequential and recyclable sensing of Fe3+ and ascorbic acid in water with a terbium(iii)-based metal-organic framework

A water-stable three-dimensional (3D) metal-organic framework (MOF) of {[Tb(Cmdcp)(H2O)(3)](2)(NO3)(2)center dot 5H(2)O}(n) (1, H(3)CmdcpBr = N-carboxymethyl-(3,5-dicarboxyl)pyridinium bromide) has been synthesized and characterized. MOF 1 is highly emissive, giving rise to green luminescence that can be quenched by Fe3+ due to the partial overlap of its excitation spectrum with the absorption spectrum of Fe3+. The subsequent introduction of ascorbic acid (AA) leads to the reduction of Fe3+ into Fe2+, accompanied by the near-entire recovery of MOF 1 emission. The density functional theory (DFT) calculation results support the proposed mechanism. 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.