The adsorption of water in one-dimensional channels in porous aluminophosphate material AlPO4-5 has been studied by a combination of gravimetric analysis techniques, neutron and X-ray diffraction and neutron spectroscopy. Molecular structure of AlPO4-5 consists of 12-membered rings of alternating, corner-sharing AlO4 and PO4 tetrahedra connected by oxygen bridges into sheets in the (a, b) plane. The sheets are connected by oxygen bridges along the c crystal axis and form one-dimensional channels of which the largest, formed by the 12-membered rings, have a van der Waals diameter of about 8.3 Å. Gradually increasing the amount of adsorbed water we could follow the evolution of the confined water mobility in a systematic way and identify the molecular mechanism of water adsorption. We focused particularly on the range of low and medium relative pressures up to p/p0 = 0.32, where a change from a hydrophobic behavior to a steep, capillary condensation like water intake has been observed. At the initial adsorption stages water occupies positions close to the pore walls causing the contraction of channels in the (a, b) plane and the prolongation of the channels along c axis in AlPO4-5. With the progressing intake water molecules form chains along the main channels. The cooperative interactions between water molecules lead to the onset of phonon-like cooperative modes and, surprisingly, to the increase of diffusive-like motion, which slow down only in the final adsorption stages when AlPO4-5 channels are completely filled. Display omitted •Water sorption isotherm with a broad hysteresis has been observed in porous material AlPO4-5 with one-dimensional channels of about 8.3 Å in diameter. It shows changes from a hydrophobic behavior to a steep water intake in the medium range of relative pressures up to p/p0 = 0.32•X-ray and neutron diffraction studies reveal that in the initial adsorption stages water occupies positions close to the pore walls causing a structural contraction of channels in the plane across the pores and an elongation of the channels along the pores. With progressing intake water molecules form chains along the main channels.•These adsorption-induced structural changes can be one of the origins of the broad hysteresis observed in AlPO4-5.•Cooperative effects between confined water molecules lead to an increase of the mean square displacement for increasing hydration values up to relative pressures of p/p0 = 0.32 and are responsible for the major water intake.