Two mixed-ligand Cd(ii)–organic frameworks with unique topologies: selective luminescence sensing of TNP and Cu2+ ions with recyclable performances

Abstract

Two novel luminescent Cd(II)–organic frameworks, [Cd₂(2-abpt)(Hbtca)(H₂btca)_0.5(H₂O)]_n (1) and {[Cd₃(2-abpt)(btca)_1.5]·H₂O}_n (2) (2-abpt = 3,5-di(2 -pyridyl)-4-amino-1,2,4-triazole, H₄btca = 1,2,4,5-benzenetetracarboxylic acid), were hydrothermally synthesized from a rigid aromatic carboxylate ligand and a pyridine ligand containing free amino groups. 1 exhibits a novel (4,4,5,5)-c 2D layer architecture with 1D pipe-like chains. 2 shows a 3D framework with an unprecedented (4,4,4,6,7)-c topology. Their structural differences mainly stem from the various coordination modes of the rigid aromatic carboxylate ligand. Luminescence sensing experiments exhibit that 1 can highly sensitively and selectively detect TNP in DMF and H₂O. Moreover, test paper was developed to detect TNP as a convenient and practicable approach. In addition, 1 shows highly sensitive and selective sensing of Cu²⁺. The possible detection mechanisms of 1 towards TNP and Cu²⁺ have been discussed. These experimental results suggest that 1 should be a potential sensor for TNP and Cu²⁺.