Cd(II)-Based Coordination\nPolymer as a Multiresponsive\nFluorescent Sensor for Efficiently Detecting Zn<sup>2+</sup>, Cr<sub>2</sub>O<sub>7</sub><sup>2–</sup>, and Phenylglyoxylic Acid

The\nconcentration of Zn<sup>2+</sup> is closely related to the\necological environment and physical health and must be monitored conveniently\nand accurately. Herein, a novel coordination polymer, namely, {[Cd<sub>2</sub>L<sub>2</sub>(bpy)<sub>2</sub>]·H<sub>2</sub>O·0.25DMF}<sub>n</sub> (<b>CP-1</b>, bpy = 2,2′-bipyridine, H<sub>2</sub>L = 5-(1H-1,2,4-triazole-1-yl)-1,3-phthalic acid) was synthesized\nunder solvothermal conditions and can be used for selective detection\nof Zn<sup>2+</sup> with an extremely low detection limit. Single-crystal\nX-ray diffraction analyses revealed that <b>CP-1</b> exhibits\nan interspersed two-dimensional (2D) layer and further constitutes\na 3D layer by weak interactions. Fluorescence experiments showed that <b>CP-1</b> can be used as an excellent fluorescent sensor for selectively\ndetecting Zn<sup>2+</sup> with the detection limit as low as 0.073\nμM. In addition, <b>CP-1</b> can also be used for the\nefficient detection of Cr<sub>2</sub>O<sub>7</sub><sup>2–</sup> and phenylglyoxylic acid (PGA) with detection limits of 0.68 and\n1.59 μM respectively. Moreover, the mechanism study showed that\nthe turn-on behavior of <b>CP-1</b> for detecting Zn<sup>2+</sup> can be attributed to absorbance-induced enhancement (ACE), and the\nturn-off behavior for detecting Cr<sub>2</sub>O<sub>7</sub><sup>2–</sup> and PGA can be attributed to the “internal filtering effect”\n(IFE) and the combined effect of photoinduced electron transfer (PET)\nand competitive absorption, respectively.