In-situ dual-MOF functionalized quasi-fractal networks with Janus wettability for high-efficient fog harvesting and intelligent interface materials

The leaf vein (LV) structure is an evolutionarily optimized quasi-fractal network responsible for efficient capture and transport of water with minimum energy consumption. For the first time, a bio-inspired dual-metal organic framework (MOF) functionalized LV network was proposed for water collection. Two MOFs with distinct wettabilities and microstructures are in-situ grown on opposite side of a metallic LV network, yielding a Janus LV (J-LV) network. The integrated strategy by mimicking cactus needles, Janus structures and bionic LV network in water harvesting can be regulated by the multi-cooperation theory in the processes of droplet caption, transport and collection. As such, the fog collection efficiency of J-LV devices can reach 1.23 ± 0.07 g cm -2 h −1 , which is a 292.9 % increase compared to that of the bare LV. Moreover, the J-LV has excellent interfacial floatability, showing capability of not only carrying objects weighing 149.5 times its own weight while keeping afloat, but also attaching firmly to the air–water interface under harsh airflow. We demonstrate that such Janus quasi-fractal LVs networks by in-situ dual-MOF growth will inspire new insight for designing highly efficient fog water collectors and intelligent Janus interface materials.