Lanthanide (LaIII/HoIII)-oxalate open framework materials formed by in situ ligand synthesis

Two new lanthanide-organic open framework materials, {La(ox)0.5(μ-OH)2(μ-H2O)(H2O)2}n (1) and {[Ho(ox)1.5(H2O)3](en)}n (2) (ox = oxalate dianion and en = ethylenediamine) have been synthesized and structurally characterized. Both the frameworks obtained from in situ synthesis of oxalate ligand from dicarboxylic acid (2,5-dihydroxyterephthalic acid for 1 and tetrabromoterephthalic acid for 2) and lanthanide ions (LnIII) at high temperature. The probable route to the formation of oxalate ligand is the decarboxylation from the corresponding dicarboxylic acid and consecutive reductive coupling catalyze by the corresponding LnIII ions. Compound 1 is a 3D framework formed by pillaring of the oxalate ligand to two dimensional La–O–La inorganic layers, resulting 1D channels along the b-axis. Compound 2 is a 2D honeycomb like oxalate bridged framework of HoIII templated by the en molecules.