Harnessing ambient moisture for energy and water is an attractive strategy to address the decentralized demand for sustainable energy and uncontaminated water supplies, especially in arid and hydropenic regions. Although discontinuous harvesting of water and electricity has been endeavored frequently on various nanomaterials, it remains challenging to integrate these two distinct processes into one system for synergetic and persistent harvesting. Herein, by in situ synthesizing solar-thermal and conductive metal–organic-frameworks on a template of sulfonate cellulose nanofibrils, biohybrid fibrils with superior moisture-adsorption, photo-thermal and water-desorption properties were produced and engineered into flexible membranes. When exposing one end of the membrane to moisture and the other to solar irradiation, rapid moisture adsorption could be balanced with solar-driven water desorption to synchronize water and electricity harvesting. A sustained open-circuit voltage of ∼0.65 V is obtained together with persistent water production of up to ∼0.8 g g−1 h−1 (at 25 °C, 99% RH). Thus, this biohybrid strategy may provide a sustainable platform for synergetic and persistent harvesting of electric power and potable water from atmospheric moisture and may be applicable in the decentralized supply of arid and hydropenic regions.