A layer-structured Eu-MOF as a highly selective fluorescent probe for Fe3+ detection through a cation-exchange approach

A new series of lanthanide metal–organic frameworks, LnL (Ln = La, Y, Eu, Tb, and Gd), were prepared under hydrothermal conditions. The five compounds are all isostructural as confirmed by the analyses of single crystal and powder X-ray diffractions. The compounds exhibit layer-like structures with the [H2NMe2]+ cations being located in the interlayer channels, which can be easily replaced by a number of metal ions. Most interestingly, compound EuL performs as a rare example of a highly selective and sensitive luminescence sensor for Fe3+ ions based on total quenching of the Eu-luminescence via cation-exchange. The possible sensing mechanism was further explored in detail. Remarkably, it is the first Eu-MOF luminescent material to exhibit an excellent ability for the detection of Fe3+ ions in a biological system.