A new family of lanthanide complexes with open-framework structures has been prepared and characterized by X-ray diffraction. The structure of the polymers with general formula [Ln(Hida)3]·xH2O (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb; H2ida=iminodiacetic acid) presents large hexagonal channels with more than 11Ǻ diameter, and houses the crystallization water molecules. These molecules can be reversibly removed upon heating. This is the first example of this kind of structure with ida as bridging ligand.