Two New Luminescent Cd(II)-Metal–Organic Frameworks as Bifunctional Chemosensors for Detection of Cations Fe³⁺, Anions CrO₄^2–, and Cr₂O₇^2– in Aqueous Solution

Two new luminescent Cd(II)-metal–organic frameworks (MOFs), {[Cd(L)(BPDC)]·2H 2 O} n ( 1 ) and {[Cd(L)(SDBA)(H 2 O)]·0.5H 2 O} n ( 2 ) [L = 4,4′-(2,5-bis(methylthio)-1,4-phenylene)dipyridine, H 2 BPDC = 4,4′-biphenyldicarboxylic acid, H 2 SDBA = 4,4′-sulfonyldibenzoic acid], have been solvothermally synthesized using Cd 2+ ion and L ligand in the presence of auxiliary ligands and characterized by infrared spectroscopy, elemental analysis, powder X-ray diffraction, and thermogravimetry measurement. Topological analyses reveal that MOF 1 is a 6-connected 3-fold interpenetrating pcu network, and MOF 2 is a new 4-connected 2-fold interpenetrating network. Fluorescence titration, cyclic and anti-interference experiments demonstrate that MOFs 1 and 2 both are excellent probes for Fe 3+, CrO 4 2–, and Cr 2 O 7 2– . The mechanisms of quenching are also deeply studied.