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.