A Photoluminescent Cd(II) Coordination Polymer with Potential Active Sites Exhibiting Multiresponsive Fluorescence Sensing for Trace Amounts of NACs and Fe3+ and Al3+ Ions.

The elaborately designed π-electron-rich fluorescent ligand 1,4-bis(1-carboxymethylene-4-imidazolyl)benzene (H2L), possessing bifunctional groups including the carboxylate groups (building units) and 4-imidazoyl groups (N-donor potential active sites) has been employed to construct fluorescent coordination polymers. A luminescent sensor, namely [Cd(L)(phen)2]·5H2O (1), was obtained, which has a one-dimensional structure. The fluorescent material shows a blue emission maximum at 457 nm with a luminescence lifetime of 488 ns and a quantum yield (QY) of 4.56%. Significantly, 1 serves as a promising multiresponsive luminescent sensor to detect trace nitroaromatic compounds (NACs) with the limits of detection (LOD) of 7.21 × 10-8, 1.85 × 10-5, and 1.15 × 10-5 mol/L for 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), and 4-nitrophenol (4-NP), respectively. Furthermore, CP 1 exhibits fluorescent turn-off and turn-on sensing behavior for Fe3+ and Al3+ metal ions with trace amounts of 1.05 × 10-7 and 1.13 × 10-7 mol/L, respectively. Experimental methods and theoretical calculations were employed to elucidate the sensing mechanism in detail.