Three new solvent-directed Cd(ii)-based MOFs with unique luminescent properties and highly selective sensors for Cu2+ cations and nitrobenzene

Abstract

Three new solvent-induced metal–organic frameworks (MOFs)—[Cd(H₂L)(H₂O)₃]·NMP (1), [Cd₃(L)(H₂O)₄(OH)₂] (2) and [Cd(L)_0.5(H₂O)]·H₂O (3)—were designed and successfully prepared via solvothermal reaction by multidentate phenyltetracarboxylic acid [1,1′:4′,1′′-terphenyl]-2′,3,3′′,5′-tetracarboxylic acid (H₄L) and Cd(II) salts in various solvent systems. Structural analyses indicated that the H₂L/L ligands took three different coordination fashions in 1–3, and thus resulted in diversity of the targeted MOFs. Solid-state luminescent properties of the three MOFs were studied under ultraviolet light irradiation at ambient temperature; 3 in particular showed high selectivity and sensitivity for Cu²⁺ ions and nitrobenzene because of the quenching effect, which thus could make it a potential crystalline material for detecting these substances. The mechanisms of the quenching effect and sensing properties of 3 are discussed in detail.