Bifunctional Zn Coordination Polymers for High-Performance Fluorescence Turn-On Detection of l-Glutamate and Adsorption of Malachite Green in Aqueous Medium

Two time-induced Zn(II) coordination polymers (CPs), namely {[Zn(BIPA-TC)0.5(1,3-bimb)]·0.75DMF}n (1) and {[Zn(BIPA-TC)0.5(1,3-bimb)]·0.5EtOH·DMF·H2O}n (2) were constructed based on 5,5′-(1,3,6,8-tetraoxybenzo[3,8]phenanthroline 2–7-substituent) bis-1,3-benzoic acid (H4BIPA-TC) and zinc salts. The structure analysis showed that 1 is 3D networks with the point symbol {62, 84} {64, 82}2 and 2 is 2D layered structures with the point symbol of {4, 64, 8}2 {42, 64}. Interestingly, the transformation from single crystal 1 to 2 is only due to the prolongation of reaction time, which can be confirmed by structural analysis and powder X-ray diffraction patterns. Meanwhile, the fluorescence sensing properties of 1 and 2 showed that both 1 and 2 had high sensitivity for l-glutamate with limits of detection of 0.10 (1) and 0.13 μM (2). The fluorescence mechanism analysis showed that the fluorescence enhancement of 1 and 2 is attributed to absorbance caused enhancement and photoinduced electron transfer. In addition, 1 and 2 can also be used as recyclable adsorbents to remove malachite green (MG) in aqueous medium. The adsorption isotherms and kinetics of both 1 and 2 follow the Freundlich model and the quasi-second-order kinetic model, respectively. The maximum equilibrium adsorption capacities of 1 and 2 for MG can reach 351.06 and 250.45 mg/g, respectively. The excellent adsorption properties of 1/2 for MG can be attributed to π–π interaction, hydrogen bonding, and electrostatic interaction between 1/2 and the MG molecule. Therefore, 1 and 2 have potential application prospects in fluorescence recognition and adsorption.