A luminescent Cd(II) coordination polymer as a fluorescence-responsive sensor for enhancement sensing of Al3+ and Cr3+ ions and quenching detection of chromium(VI) oxyanions

Highlights: • Complex 1 adopts a complicated 2-D gridlike sql layer structure. • Complex 1 exhibits high thermal, chemical, and pH stabilities. • Complex 1 can be a fluorescence turn-on sensor for sensing Al³⁺ and Cr³⁺. • Complex 1 can selectively detect CrO₄²⁻ and Cr₂O₇²⁻ over other anions. A luminescent coordination polymer [Cd(H₂dhbdc)(NI-mbpy-34)₂]_n (1), where H₄dhbdc=2,5-dihydroxyterephthalic acid, NI-mbpy-34=N-(pyridin-3-ylmethyl)-4-(pyridin-4-yl)-1,8-naphthalimide, has been synthesized under hydro(solvo)thermal conditions. From the topological point of view, the crystal structure of 1 is fabricated by 4-connected square-planar nodes, forming a complicated two-dimensional (2-D) gridlike sql layer with the point symbol of (4⁴·6²), which consists of one-dimensional (1-D) {Cd–NI-mbpy-34}_n²ⁿ⁺ribbon chains and H₂dhbdc²⁻ bridges. Complex 1 displays high thermal, chemical, and pH stabilities. Moreover, complex 1 exhibits pH- and solvent-dependent luminescence properties varying in intensity and wavelength, and emits blue fluorescence in H₂O suspension phase. These features promise 1 to be a multifunctional sensor platform for sensitive detection of Al³⁺ and Cr³⁺ through luminescence enhancement as well as CrO₄²⁻ and Cr₂O₇²⁻ through luminescence quenching from most interfering ions.