3D LnIII-MOFs: displaying slow magnetic relaxation and highly sensitive luminescence sensing of alkylamines

Abstract

Six new 3D isomorphous lanthanide metal organic frameworks (Ln-MOFs), [Ln₂(L)₂(DMF)₂(H₂O)₄]·H₂O·DMF (Ln = Pr (1); Sm (2); Eu (3); Gd (4); Dy (5); Ho (6)); H₃L = 5-(2-nitro-4-carboxylphenyl)isophthalic acid, have been solvothermally synthesized and characterized. Crystallographic studies revealed that these MOFs were isomorphous 3D frameworks in which the dinuclear units with double (μ-COO)₂ bridges were interlinked by the L ligands. They represent the (3,6)-connected (4²·6)(4³·6⁸·8²·10·12) topology. The magnetic coupling through double carboxylate bridges is antiferromagnetic in Pr-MOF (1), Gd-MOF (4), Dy-MOF (5) and Ho-MOF (6). Furthermore, Dy-MOF (5) shows slow magnetic relaxation behaviors under zero dc field. The luminescence sensing experiments demonstrated that Eu-MOF (3) displayed highly selective, well-recyclable properties and a low detection limit for sensing alkylamines in water systems. The study of Ln-MOF sensing for alkylamines is very scarce.