A robust Zn(II)/Na(I)-MOF decorated with [(OAc)2(H2O)2]n2n- anions for the luminescence sensing of copper ions based on the inner filter effect

Based on the inner filter effect, a luminescent Zn(II)/Na(I) metal-organic framework (MOF) {[Zn2Na(L) (HL)(2)(H2O)(2)][OAc]center dot 2H(2)O}(n) (1, H2L = 5-methyl-1,3-benzenedicarboxylic acid) with excellent stability was constructed for the fluorescence detection of Cu2+ ions. MOF 1 holds a 3D cationic framework in which [(OAc)(2)(H2O)(2)](n)(2n-) anions are embedded into its 1D channels. Abundant hydrogen-bonding and pi-pi interactions in the MOF facilitate electron transfer from ligand-to-metal, resulting in a good luminescence peak at 412 nm and an efficient fluorescence quenching of MOF 1 in the presence of Cu2+ ions, due to the inner filter effect. The interactions between the Cu2+ ions and the OAc- anion in the channel endowed the Cu2+ ions with facile access to be adsorbed, and afforded the selective quenching of fluorescence. The MOF particles are well dispersed in water and the Cu2+ ions are pre-concentrated by adsorption, thus facilitating the determination of Cu2+ ions with a detection limit down to 0.65 mu M. Our work thus paves a way for developing MOFs as an appealing platform to construct materials for environmental applications.