An Eu3+ post-functionalized nanosized metal-organic framework for cation exchange-based Fe3+-sensing in an aqueous environment

A novel strategy was demonstrated to fabricate a luminescent lanthanide functionalized MOF by encapsulating Eu3+ cations in the pores of MIL-53 COOH (Al) nanocrygtals. The Eu3+ incorporated sample shows excellent luminescence and good fluorescence stability in water due to the sensitization and protection provided by the parented framework. Subsequently, Eu3+ incorporated nanocrystals were developed as a highly selective and sensitive probe for detection of Fe3+ in aqueous solutions. In addition, the possible sensing mechanism based on cation exchange between Fe3+ and the framework Al3+ in MIL-53 COOH (Al) was discussed in detail. This is the first example for detecting Fe3+ in aqueous solutions based on a lanthanide functionalized nanoscale MOF. The good fluorescence stability in an aqueous environment, the low detection limit and the broad linear range, together with the nanoscale nature of this probe suggest it has potential for intracellular sensing and imaging of Fe3+.