Structures, photoluminescence and photocatalytic properties of three new metal–organic frameworks based on non-rigid long bridges

Abstract

Three new metal–organic coordination polymers, [Cd₃(5-NO₂-bdc)₂(5-NO₂-bdcH)₂(bpyo)₂]_n (1), [Mn(5-NO₂-bdc)(bbim)]_n (2) and {[Gd(5-NO₂-bdc)(5-NO₂-bdcH)](bpyo)_0.5·2H₂O}_n (3) (5-NO₂-bdcH₂ = 5-nitro-1,3-benzenedicarboxylic acid; bpyo = 4,4′-bipyridine-N,N′-dioxide; bbim = 1,1′-(1,4-butanediyl)bis(benzimidazole)), were obtained under hydrothermal conditions and characterized structurally. The networks exhibit a variety of topologies and coordination modes at the metal centers. Complex 1 exhibits NaCl-type topology and contains the centrosymmetric trinuclear cluster SBU [Cd₃(COO)₄O₂]. Complex 2 adopts CsCl-type topology based on bimetallic cores and is the first example of compounds containing a cis bbim bridge. Moreover, complex 3 possesses a 3D supramolecular framework by stronger contacts between 2D layers and non-rigid bpyo bridges. The thermal stabilities of 1–3, the photoluminescence properties of 1 as well as the photocatalytic performance of 3 were also examined, and the results indicated that 1 seems to be a good candidate for novel hybrid inorganic–organic photoactive materials, especially, compound 3 represents the rare example of coordination polymers with a 4f metal ion that exhibit good photocatalytic activity for dye degradation under UV light.