A Thermally Stable Undulated Coordination Layer Showing a Sequentially Interweaving 2D → 3D Net as a Turn-On Sensor for Luminescence Detection of Al3+ in Water

A Zn coordination polymer, [Zn(H(2)dhbdc)(Cz-3,6-bpy)](n), (1, H(4)dhbdc = 2,5-dihydroxyterephthalic acid, Cz-3,6-bpy = 3,6-bis(pyridin-4-yl)-9H-carbazole), showing high thermal stability up to 407 degrees C, has been prepared under hydro(solvo)thermal conditions. Compound 1 has a two-dimensional (2D) undulated layer structure regarded as the topological sql grid, where the tetrahedral Zn(II) centers act as 4-connected nodes connecting by H(2)dhbdc(2-) and Cz-3,6-bpy ligands as linkers. Interestingly, the 2D undulated layers expanding in the be plane are sequentially interwoven with each other in an offset manner along the a-axis, resulting in a condensed polyinterweaving 2D -> 3D net. Compound 1 emits weak fluorescence at 522 nm in water suspensions; the intensity can be significantly enhanced by adding Al3+ ions, with low limit of detection (LOD) of 0.62 mu M and high anti-interference ability over numerous competitive metal ions except Fe3+ ions. Moreover, the detection performance of 1 toward Al3+ retains high luminescence stability and reusability, being as an excellent candidate for Al3+ detection over a long period. Spectroscopic evidence from XRPD, EDS, IR, and XPS suggest the occurrence of weak framework-analyte interactions between the H(2)dhbdc(2-) ligand units in 1 and the Al(3+ )ions, resulting in luminescence turn-on sensing.

Automated summary

A Zn coordination polymer with high thermal stability was successfully synthesized and showed high sensitivity and anti-interference ability towards Al3+ ions, while maintaining high luminescence stability and reusability over a long period. Spectroscopic evidence suggested weak framework-analyte interactions between the ligand units in the polymer and the Al3+ ions, leading to luminescence turn-on sensing.