The structure and dehydration behavior of the porous 3D coordination polymer {[La-2(adipate)(3)(H2O)(4)]6H(2)O}(n) are described. Each La3+ is coordinated by nine oxygen atoms belonging to five carboxylate ligands and to two water molecules. Large infinite interconnected channels filled with hydrogen-bonded water molecules are formed in the structure. Upon heating, this compound transforms reversibly into a nonporous lower hydrate.