A series of two-dimensional metal-organic frameworks based on the assembly of rigid and flexible carboxylate-containing mixed ligands with lanthanide metal salts

A series of lanthanide metal-organic frameworks, [Ln(2) (Suc)(0.5)(BC)(3)(OH)(2)] (Ln = Tb (1), Eu (2), Sm (3), Pr (4); H(2)Suc = succinic acid; HBC = benzoic acid), have been synthesized by the reaction of nitrate salts of Ln(III) with succinic acid and benzoic acid under hydrothermal conditions and were characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. X-ray diffraction analyses reveal that they exhibit the same two-dimensional (2D) architecture and crystallized in triclinic space group Pi for complexes 1-4. Infinite inorganic walls were formed by lanthanide ions,mu(3)-OH, and an edge-sharing "...Ln-O-C-O-Ln..." chain, which link to each other through the carbon atoms of the succinate anions on the [110] plane and phenyl groups of the benzoic acid ligands on the [101] plane, leading to a two-dimensional open framework structure. The thermogravimetric analysis of 1-4 and photoluminescent properties of 1 and 2 are discussed in detail.