Flexible Nanofibrous Membrane with Valley-Cell Array of Rapid Thermal Response and Stability for Efficient Water Harvesting Performance

We demonstrate a flexible nanofibrous membrane featuring a valley-cell array (NMVA). Inspired by honeycombs and spider silk, the NMVA is rationally designed using poly(vinyl alcohol), carbon black, and MOF-303 as its main components. The synergistic effect of the flexible honeycomb network, abundant hydrophilic sites of MOF-decorated nanofibers, rapid photothermal response, and multidimensional structural stability favors highly efficient adsorption and desorption dynamics during water harvesting. The valleys of the honeycomb cell arrays enhance light capture for photothermal conversion and water release, while the abundant hydrophilic sites facilitate water molecule capture and uptake. As a result, NMVA achieves a high water uptake capacity of ∼0.41 g g-1 at 25 °C and 30% RH, and can release 92% of the absorbed water within 30 min under 1 sun irradiation. For an integrated NMVA in outdoor conditions under sunlight of ∼0.76 kW m-2 on average, water harvesting capacities reach 3.85-5.0 L kg-1 day-1 at 42-68% RH through continuous all-day water uptake-release over seven cycles. This study provides insights into the design of novel materials that can be extended into the realms of water engineering for energy systems and portable devices.