Zinc(II)-Based Ring-and-Rod Coordination Layer as an Excitation-Wavelength-dependent Dual-Emissive Chemosensor for Discriminating Fe³⁺, Cr³⁺, and Al³⁺ in Water

Abstract

The reactions of Zn­(NO3)2, 3,6-bis(pyridin-3-yl)-9H-carbazole (bpycz), and 2,5-dihydroxyterephthalic acid (H4dhbdc) or 2-bromoterephthalic acid (Br-1,4-H2bdc) under hydro­(solvo)­thermal conditions yielded corresponding coordination polymers (CPs) {[Zn­(H2dhbdc)­(bpycz)]•0.5H2O} n (1) and [Zn­(Br-1,4-bdc)­(bpycz)]•2DMAc•H2O (2), respectively, with high thermal stability approaching 350 °C. CP 1 adopts a ring-and-rod layer structure, which is topologically described as a 4-connected net with the point symbol of 2•65. 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 2 has a non-interpenetrating ring-and-rod layer structure of 4-connected 2•65 net topology, with extra-framework void space of 16.6%. Thermally activated 1 and 2 revealed CO2 uptakes of 101.1 and 98.6 cm3 g–1, respectively, at P/P 0 = 1 and 195 K. X-ray powder diffraction (XRPD) patterns confirmed that 1 and 2 both possessed high chemical stability in H2O, CH3OH, acetone, and DMF, and framework stability during gas adsorption–desorption. The H2O suspension of 1 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, 1 was capable of detection of Fe3+, Cr3+, and Al3+ ions in H2O, showing good anti-interference ability, excellent selectivity, and high sensitivity. More interesting, the dual-emissive properties make 1 to be an excellent luminescence chemosensor to screen Fe3+, Cr3+, and Al3+ from a pool of metal ions in H2O upon excitation at 300 nm via luminescence quenching effect and then discriminate Fe3+, Cr3+, and Al3+ upon excitation at 365 nm via luminescence quenching, unaltered, and enhancement responses, respectively. On the other hand, the H2O suspension of 2 demonstrated an excitation-independent emission appearing at around 430 nm, which could be utilized to sensitively detect Fe3+ and Cr3+ ions with good anti-interference ability and excellent selectivity via luminescence quenching effect. Further, 1 and 2 were recyclability and possessed cycling stability. The plausible sensing mechanisms for 1 and 2 toward Fe3+, Cr3+, and Al3+ were also explored in detail.

Wavelike zinc coordination polymers: anion-modulated ligand conformation and fluorescence detection of 4-aminobenzylamine

“…The ligand 3,6-bis(pyridin-3-yl)-9 H -carbazole (bpycz) was prepared according to a literature report. 33 X-ray powder diffraction (XRPD) patterns were measured using a Shimadzu XRD-7000 diffractometer. The X-ray study used copper as the anode material and was performed at 30 kV and 30 mA, and the wavelength of Kα radiation was 1.5406 Å. Infrared (IR) spectra were recorded in the transmission mode on a Perkin-Elmer Frontier Fourier-transform infrared spectrometer using the attenuated total reflection (ATR) technique.…”