Zinc(II)-Based Ring-and-Rod Coordination Layer as an Excitation-Wavelength-dependent Dual-Emissive Chemosensor for Discriminating Fe, Cr, and Al in Water.

The reactions of Zn(NO), 3,6-(pyridin-3-yl)-9-carbazole (bpycz), and 2,5-dihydroxyterephthalic acid (Hdhbdc) or 2-bromoterephthalic acid (Br-1,4-Hbdc) under hydro(solvo)thermal conditions yielded corresponding coordination polymers (CPs) {[Zn(Hdhbdc)(bpycz)]•0.5HO} () and [Zn(Br-1,4-bdc)(bpycz)]•2DMAc•HO (), respectively, with high thermal stability approaching 350 °C. CP adopts a ring-and-rod layer structure, which is topologically described as a 4-connected net with the point symbol of 2•6. Two layers are interpenetrated in parallel interlocking mode to form a double 2D → 2D polyrotaxane entanglement with extra-framework void space of 19.6%. CP has a non-interpenetrating ring-and-rod layer structure of 4-connected 2•6 net topology, with extra-framework void space of 16.6%. Thermally activated and revealed CO uptakes of 101.1 and 98.6 cm g, respectively, at / = 1 and 195 K. X-ray powder diffraction (XRPD) patterns confirmed that and both possessed high chemical stability in HO, CHOH, acetone, and DMF, and framework stability during gas adsorption-desorption. The HO suspension of displayed excitation-dependent dual-emissive properties, appearing at 432 nm upon excitation at 300 nm and at 528 nm upon excitation at 365 nm. Of note, was capable of detection of Fe, Cr, and Al ions in HO, showing good anti-interference ability, excellent selectivity, and high sensitivity. More interesting, the dual-emissive properties make to be an excellent luminescence chemosensor to screen Fe, Cr, and Al from a pool of metal ions in HO upon excitation at 300 nm via luminescence quenching effect and then discriminate Fe, Cr, and Al upon excitation at 365 nm via luminescence quenching, unaltered, and enhancement responses, respectively. On the other hand, the HO suspension of demonstrated an excitation-independent emission appearing at around 430 nm, which could be utilized to sensitively detect Fe and Cr ions with good anti-interference ability and excellent selectivity via luminescence quenching effect. Further, and were recyclability and possessed cycling stability. The plausible sensing mechanisms for and toward Fe, Cr, and Al were also explored in detail.