Sorption and sensing properties of coordination polymers with mixed 1,3,5-tri(1-imidazolyl)benzene and 2,6-naphthalenedicarboxylate ligands

Abstract

Under hydro/solvothermal conditions, the assembly of imidazole-containing ligand 1,3,5-tri(1-imidazolyl)benzene (tib) and 2,6-naphthalenedicarboxylic acid (H₂NDC) with different transition metal salts provides five new coordination polymers [M₂(tib)₂(NDC)(H₂O)₂] SO₄·XH₂O (1: M = Cd, X = 4; 2: M = Co, X = 4; 3: M = Ni, X = 3), [Cd₂(tib)₂(NDC)(NO₃)₂] 2.5DMF·H₂O (4) (DMF = N,N-dimethylformamide) and [Zn(tib)_2/3(NDC)] (5). 1–3 have the same three-fold interpenetrating 3D framework structures with SO₄²⁻ as counteranion, while 4 with NO₃⁻ as terminal ligand exhibits a wave-like 2D layer structure, which is further extended into a 3D framework by hydrogen bonds. In addition, complex 5 obtained at high temperature is an interesting two-fold interpenetrating 3D structure. Sorption and photoluminescence properties of the complexes were investigated. 4 displays selective adsorption of CO₂ over N₂. Furthermore, 1 and 4 can be used to probe acetone molecules selectively and rapidly via fluorescence quenching.