8-Hydroxyquinoline and its derivati

8-Hydroxyquinoline and its derivatives have been wellestablished as versatile ligands to construct functional metal−organic materials. 17 For example, aluminum tris-(hydroxyquniolate) has been applied in luminescent devices. 18Our previous reports revealed that 8-hydroxyquinolinateligands can facilitate the formation of multinuclear metalbuilding units with enhanced rigidity and coplanarity, whichfurther assemble into 3D frameworks with hydrophobicchannels. 19 The above two features will be beneficial for thewater stability of the resulting MOFs. Inspired by this, weenvision that water-resistant LMOFs bearing good sensitivityand selectivity toward NACs and metal cations can befabricated using rationally designed ligands and suitablenodes. Herein one 8-hydroxyquinolinate ligand with acarboxylate group was synthesized, characterized, andemployed in the assembly of five MOFs, [Zn 2 L 2 ]·2DMF·2MeOH (1; DMF = N,N-dimethylformamide and MeOH =methanol), [Zn 2 L 2 (py) 2 ] (2; py =pyridine), [Cd 2 L 2 ]·Diox·MeOH·6H 2 O (3; Diox = 1,4-dioxane), [Mn 2 L 2 ]·2DMF·2MeOH (4), and [Co 2 L 2 ]·2DMF·4H 2 O (5), based on thefollowing reasons: (i) the lowest unoccupied molecular orbitalsof 8-hydroxyquinoline are mainly located on the pyridyl ring,implying that the introduction of a carboxylphenyl group cantune the band gap of target complexes, thus modulating theluminescence properties; 20 (ii) the carboxylphenyl group inH 2 L can further enhance the rigidity, π-electron density, andband gap of the ligand, facilitating the formation of robustporous frameworks; (iii) strong metal−ligand bonds can beachieved by the bidentate NO coordination sites of H 2 L. 1−5exhibit a variety of 2D and 3D supramolecular frameworks(Scheme 1). Remarkably, complex 1 is capable of not onlysensing NACs through luminescence quenching but alsobehaving as a highly selective and sensitive luminescent sensorto detect Fe 3+ in water (H 2 O) because of its high waterstability.