Ultrasonic-Assisted Synthesis of a Zn(II) Coordination Polymer in Aqueous Media and Its High-Performance Luminescent Sensing for 2,4,6-Trinitrophenol

Abstract

A novel Zn(II) coordination polymer based on 5-(3-pyridyl)-1,3,4-oxadiazole-2-thiol (Hpzt), namely [Zn(pzt)2]n or Zn-CP, was synthesized by two different synthetic methods. The bulk polycrystals and single crystals of Zn-CP were obtained by a conventional solvothermal method at 90 °C. Zn-CP exhibits a two-dimensional (2D) coordination network that contains the uncoordinated Lewis basic sites within each layer. Interestingly, a simple and environmentally friendly sonochemical synthesis of the Zn-CP in an aqueous media could be performed at room temperature. The optimal synthetic conditions were studied. The uniform microplates of Zn-CP were obtained within 30 min with the addition of pyridine, acting as a size modulator and a deprotonating reagent. The influence of the amount of the modulator and the sonication time on the crystal size was investigated. Moreover, a Zn-CP suspension in an ethanolic media has been used as a luminescence sensor for the detection of nitroaromatic compounds. It shows highly selective and sensitive sensing of 2,4,6-trinitrophenol (TNP) through a quenching (turn-off) process under UV light. Also, the Zn-CP microplates show higher dispersibility and a more stable suspension in comparison to those of bulk products, causing an increase of the luminescent sensing performance for TNP.