Bifunctional Zn Coordination Polymers for High-Performance Fluorescence Turn-On Detection of <scp>l</scp>-Glutamate and Adsorption of Malachite Green in Aqueous Medium
Sai Ma, Lingling Gao, Yujuan Zhang, Tuoping Hu
Abstract
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·H 2 O} n ( 2 ) were constructed based on 5,5′-(1,3,6,8-tetraoxybenzo[3,8]phenanthroline 2–7-substituent) bis-1,3-benzoic acid (H 4 BIPA-TC) and zinc salts. The structure analysis showed that 1 is 3D networks with the point symbol {6 2, 8 4 } {6 4, 8 2 } 2 and 2 is 2D layered structures with the point symbol of {4, 6 4, 8} 2 {4 2, 6 4 }. 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.