Synthesis, structures and near-infrared luminescent properties of two novel temperature-dependant Er(III) coordination polymers based on 2,2′-bipyridine-3,3′,6,6′-tetracarboxylic acid

Two novel Er(III) metal–organic frameworks, namely, {[Er5(bptc)3(Hbptc)(H2O)12]·4H2O}n (1) and {[Er(bptc′)]}n (2) have been synthesized through the hydrothermal reaction of H4bptc with trivalent erbium salts in different temperatures (H4bptc = 2,2′-bipyridine-3,3′,6,6′-tetracarboxylic acid, H3bptc′ = 2,2′-bipyridine-3,6,6′-tricarboxylic acid). The hydrothermal decarboxylation of H4bptc into H3bptc′ in 2 was found in higher temperature. Compound 1 reveals a 2-D layered structure and 2 exhibits a 3-D framework structure. The near-infrared luminescent properties of compounds 1–2 have been investigated at 77 K.