A 3D porous metal-organic framework (MOF) with 1D open channels has been constructed hydrothermally using Zn-II and a rigid planar ligand IDC3- (imidazole-4,5-dicarboxylate). This MOF can adsorb water selectively over organic solvents and can be regenerated and reused. It also represents a rare example of a MOF with open channels that form/collapse reversibly upon hydration/dehydration.