Two Co(II)-based coordination polymers as multi-responsive luminescent sensors for the detection of levofloxacin, benzaldehyde and Fe³⁺ ions in water media

Two new ternary metal coordination polymers (CPs), [Co(OBA)(L1)_0.5]_n (1) and [Co(HBTC)(L2)]_n (2) (H₂OBA = 4,4′-oxybis(benzoic acid), H₃BTC = 1,3,5-benzenetricarboxylic acid, L1 = 1,3-bis(1-(pyridin-4-ylmethyl)-1H-benzimidazol-2-yl)propane, and L2 = 1,4-bis(benzimidazol-1-yl)-2-butene), were synthesized under hydrothermal conditions and characterized. 1 features a unique 2D (3,3,4)-connected layer which further extended into a 3D framework through intra-molecular π–π stacking interactions. 2 exhibits a 3D 3,5T21 network with the point symbol of (4²·6⁵·8³)(4²·6). The two CPs present high thermal and chemical stabilities in the pH range from 3 to 12. Moreover, 1/2 can detect levofloxacin (LEV), benzaldehyde (BZH) and Fe³⁺ ions in aqueous solution through the fluorescence quenching process with excellent sensitivity, selectivity, recyclability and extremely low detection limits.