Luminescent Turn-On/Turn-Off Sensing Properties of a Water-Stable Cobalt-Based Coordination Polymer

Using a pyridine-derived molecule 1,3,5-tris(4-pyridyl)benzene (TPB) and a polycarboxylate linker 1,3-benzenedicarboxylic acid (H2BDC), a Co(II)-based coordination polymer {[Co(TPB)(BDC)]·0.5H2O} (1) with a high water stability was successfully prepared and fully characterized. Compound 1 possesses a unique 3D pillar-chained network wherein the adjacent 1D double [Co(BDC)] chains are further connected by TPB pillars. The photoluminescence property of 1 was studied, exhibiting a weak emission with UV light irradiation. Interestingly, the multiresponsive luminescence makes compound 1 a versatile chemosensor for several metal cations and inorganic anions in aqueous solutions. It has a great ability to selectively detect cationic Al3+ and Cu2+ and anionic IO4– through luminescence turn-on or turn-off effects. In particular, the luminescence intensity could be significantly decreased by existence of IO4–, which is seldom reported among the cobalt-based coordination polymers and implies that 1 can act as an effective fluorescence probe to sense corresponding species. The quenching mechanism for various ions has been discussed in detail. In addition, the magnetic property of 1 was investigated.