A channel-structured Eu-based metal–organic framework with a zwitterionic ligand for selectively sensing Fe3+ ions

A novel Eu-based MOF [Eu(IMS1)2]Cl·4H2O (1) was successfully constructed based on a semi-rigid zwitterionic 1,3-bis(4-carboxylbenzyl)-imidazolium (IMS1) ligand, featuring a 3-fold interpenetrating dia net structure with a point symbol of 66 and charged permanent micropores. Considering its excellent luminescent property as well as thermal and chemical stability, complex 1 was explored as a potential sensor for detecting Fe3+ ions. The results show that complex 1 has a high sensitivity and selectivity for Fe3+ based on a ‘turn-off’ effect, for which the electrostatic interaction between Fe3+ ions and the inner surface of the micropores may play a critical role. The fluorescence quenching mechanism reveals that dynamic quenching and competitive adsorption between Fe3+ and 1 lead to the quenching effect of 1.