A series of lanthanide–organic frameworks possessing arrays of 2D intersecting channels within a 3D pillar-supported packed double-decker network and Co2+-induced luminescence modulation

Abstract

A new family of three-dimensional lanthanide metal–organic frameworks (Ln-MOFs) formulated as {Ln(NDC)_1.5(DMF)(H₂O)_0.5·0.5DMF}_n (Ln = Ce, Pr, Nd, Eu; DMF = N,N′-dimethylformamide; NDC = 2,6-naphthalenedicarboxylic acid) (FJU6) was prepared using a combination of extended dicarboxylate ligands and lanthanide cations under mild hydrothermal conditions. FJU6 contains a rare packed double-decker unit. The adjacent packed double-decker units are further pillared by NDC ligands through different coordination modes, resulting in the generation of a porous 3D framework. Notably, arrays of two-dimensional intersecting channels, occupied by coordinated and guest DMF molecules, are found in FJU6. Strong hard acid–hard base interactions between Ln³⁺ cations and NDC²⁻ anions, along with strong π–π interactions, were observed between packed 2D double-decker architectures, resulting in a high thermal stability of FJU6 as evidenced by TG analysis. The structural diversity and photoluminescence properties of the frameworks were also investigated. Significantly, in the case of Eu-FJU6, the apparent luminescence modulation induced by presence of diverse amounts of cobalt cations is observed.