Engineering\nof Hierarchical Porous Composite Film\n(ZIF-8@PVDF/PMMA) with Superhydrophobicity for Highly Efficient Water\nHarvesting

Atmospheric water harvesting has attracted much attention\nbecause\nof its potential to escalate the global freshwater shortage. However,\nthe water collection efficiency is hindered by the trade-off between\nfast droplet nucleating and rapid droplet dripping due to the opposite\nrequirements in the chemistry and the morphology of surfaces. Herein,\nthe hierarchical porous composite film (ZIF-8@PVDF/PMMA, HPCF) with\nsuperhydrophobicity is designed for highly efficient and stable water\nharvesting. It indicates that the HPCF film has a large water contact\nangle (WCA) of 155.50° and ultralow sliding angle (SA) of 2°,\nexhibiting the self-cleaning function. Significantly, it is demonstrated\nthat the water collection efficiency of HPCF can achieve 1.13 g·cm<sup>–2</sup>·h<sup>–1</sup>, which is much higher\nthan the value of the blank sample, as well as most of the reported\nvalues. It is attributed to the hierarchical porous structure with\nthe ZIF-8 crystals enhancing the surface roughness and endowing the\nfilm with the hydrophilic/superhydrophobic regions. This design promotes\nan optimal balance between droplet nucleation and shedding, significantly\nenhancing the water harvesting efficiency. Consequently, this work\nintroduces an effective approach for water collection materials suitable\nfor fog/mist conditions and provides an effective solution for the\nfoggy area with water scarcity, demonstrating significance for advancing\nresearch aimed at mitigating the worldwide water shortage.