Hydrothermal syntheses and characterization of novel 3D open-framework and 2D grid lanthanide fumarates:: Ln2(fum)3(H2fum)(H2O)2 (Ln = Ce or Nd), [Sm2(fum)3(H2O)4](H2O)3, and [Yb2(fum)3(H2O)4](H2O)2

Four novel open-framework or rectangular grid coordination polymers of lanthanide fumarates. where the lanthanides ce(III). Nd-III, Sm-III and Yb-III were used, were readily synthesized and structurally characterized. The direct hydrothermal reaction of fumaric acid and appropriate lanthanide oxides provided a highly efficient approach to the syntheses of multidimensional framework solids. Two types of three-dimensional (3D) open frameworks. Ln(2)(fum)(3)(H(2)fum)(H2O)(2) (Ln = Ce or Nd: 1 and 2) and [Sm-2(fum)(3)-(H2O)(4)](H2O)(3) (3), and one two-dimensional (2D) rectangular grid polymer, [Yb-2(fum)(3)(H2O)(4)](H2O)(2) (4), have been isolated from the hydrothermal reaction. The solids 1 and 2 are isostructural and consist of three types of ligand binding modes contributing to link the metal-O polyhedral chains to 3D open-framework architectures. Compound 3 has a 3D open-framework structure remarkably different from those of 1 and 2, owing to distinct ligand bridging patterns. The framework is microporous and incorporates some crystalline water molecules therein by hydrogen-bonding interactions. In contrast, the structure of compound 4 features a 2D rectangular grid-like framework composed of large cavities (10.5 x 9.4 angstrom(2)). Furthermore, the thermal behaviors and PXRD patterns of four compounds correlated with the corresponding structural features have been also investigated.