The development of atmospheric water generators depends critically on the preparation of hygroscopic materials. In our systematic efforts toward producing porous frameworks for effective humidity reduction, a super hygroscopic material, which was composed of hetero-layered 2D (two-dimensional) metal–organic framework nanosheet composites, has been established. The effective hetero-layered interactions have endowed the material with the functionalities of simultaneous humidity capture and in situ liquefaction, reaching an unprecedented value of water adsorption of over 658% (highest) of its own weight under ambient atmospheric and room-temperature conditions. Outdoor experiments have suggested that the fast water release is triggered by natural sunlight. Compared with classical hygroscopic salts that require plenty of energy input for water release, the present work has provided a promising strategy for developing next-generation hygroscopic materials for humidity-related management and advanced atmospheric water generator systems.