Four Cd(II)-CPs as dual-responsive luminescent probes for the sensing of Co2+/Hg2+ and chlortetracycline

Four new ternary Cd(II) coordination polymers (CPs) based on rarely-used 2-(pyridin-2-yl)-1-(pyridin-3-ylmethyl)-1H-benzo[d]imidazole (L) were synthesized via hydrothermal method, namely {[Cd(L)(H2DOBDC)]·H2O}n (1), {[Cd(L)(TP)]·2H2O}n (2), [Cd2(L)(DCTP)2(H2O)]n (3) and {[Cd2(L)(NDA)2]·H2O}n (4) (H4DOBDC = 2,5-dihydroxy terephthalic acids, H2TP = terephthalic acid, H2DCTP = 2,5-dichloroterephthalic acid and H2NDA = 1, 4-naphthalenedicarboxylic acid). 1 and 2 are 4-connected 2D sql layers, in which 2 is further expanded into a 3D supramolecular network by π − π stacking interaction, while 3 and 4 exhibit three-dimensional frameworks with unusual topology. 1 and 3/2 and 4 can act as dual-functional fluorescent sensors for the sensing of Hg2+/Co2+and chlortetracycline (CTC) with response times of 30 s for Hg2+/Co2+ and 20 s for CTC, respectively, in which 2 and 3 as promising fluorescence probes for analytes with detection limits of 1.44 and 0.91 μmoL/L, 3.34 and 0.66 μmoL/L, respectively. The fluorescence sensing mechanism was discussed in detail.