Two novel yttrium trimesates with open frameworks have been synthesized by the self-assembly of trimethyl 1,3,5-benzenetricarboxylate and Y(3+) ion in mixed solvent of dimethylformamide (DMF)/water and diethylformamide (DEF)/water, where changes of solvents with different molecular sizes lead to the formation of two similar three-dimensional frameworks with different spatial arrangement styles of the linkers around the Y(3+) centers, and solvent-dependent one-dimensional channels (ca. 6.2 x 7.7 A(2)) along the [100] direction, as shown by X-ray crystallography. Structural analyses indicate that they have excellent thermal stabilities which are endurable up to 490 degrees C.