The hydro­(solvo)­thermal reactions of Zn­(NO3)2·6H2O, bis­(pyridin-4-yl)­benzothiadiazole (BTD-bpy), and benzene-1,3,5-tricarboxylic acid (H3btc) or naphthalene-1,4-dicarboxylic acid (1,4-H2ndc) yielded the corresponding coordination polymers {[Zn2(Hbtc)2(BTD-bpy)­(MeOH)2]·MeOH} n (1) and {[Zn2(1,4-ndc)2(BTD-bpy)]·0.5MeOH·H2O} n (2), respectively. Compound 1 has a two-dimensional (2D) decorated layer structure of an sql net with sufficient free volumes of 19.8%. Compound 2 exhibits a three-dimensional (3D) pillared-layer open framework of a pcu net; two such identical frameworks are mutually interpenetrated with each other to form overall 2-fold interpenetating frameworks with sufficient free volumes of 19.8%. Compounds 1 and 2 both showed blue fluorescence in the solid state and in different solvent suspensions. The luminescence properties of 1 and 2 were exploited as multiresponsive luminescence sensors for the sensitive detection of Cr2O7 2 – and MnO4 – with a low detection limit and high selectivity over other anions in DMF suspensions through luminescence quenching. Additionally, the same DMF suspensions were also utilized to selectively recognize trace amounts of Fe3 + among large pools of different metal ions with excellent anti-interference ability, high sensitivity, and low detection limit. Of particular note, compounds 1 and 2 exhibited two different modes for Fe3 + detection, showing an abnormous luminescence enhancement–quenching (turn-on–turn-off) sensing mechanism for the former and a regular luminescence quenching (turn-off) response for the latter.

Two Cd(II) based coordination polymers, {Cd3(btc)2(BTD-bpy)2]∙1.5MeOH∙4H2O}n (1) and [Cd2(1,4-ndc)2(BTD-bpy)2]n (2), where BTD-bpy = bis(pyridin-4-yl)benzothiadiazole, btc = benzene-1,3,5-tricarboxylate, and 1,4-ndc = naphthalene-1,4-dicarboxylate, were hydro(solvo)thermally synthesized. Compound 1 has a three-dimensional non-interpenetrating pillared-bilayer open framework with sufficient free voids of 25.1%, which is simplified to show a topological (4,6,8)-connected net with the point symbol of (324256)(344454628)(3442619728). Compound 2 has a three-dimensional two-fold interpenetrating bipillared-layer condense framework regarded as a 6-connected primitive cubic (pcu) net topology. Compounds 1 and 2 both exhibited good water stability and high thermal stability approaching 350 °C. Upon excitation, compounds 1 and 2 both emitted blue light fluorescence at 471 and 479 nm, respectively, in solid state and at 457 and 446 nm, respectively, in the suspension phase of H2O. Moreover, compounds 1 and 2 in the suspension phase of H2O both exhibited a fluorescence quenching effect in sensing Ag+, attributed to framework collapse, and a fluorescence enhancement response in sensing Al3+ and Cr3+, ascribed to weak ion–framework interactions, with high selectivity and sensitivity and low detection limit.