RESUMEN
Atmospheric water harvesting has attracted much attention because of its potential to escalate the global freshwater shortage. However, the water collection efficiency is hindered by the trade-off between fast droplet nucleating and rapid droplet dripping due to the opposite requirements in the chemistry and the morphology of surfaces. Herein, the hierarchical porous composite film (ZIF-8@PVDF/PMMA, HPCF) with superhydrophobicity is designed for highly efficient and stable water harvesting. It indicates that the HPCF film has a large water contact angle (WCA) of 155.50° and ultralow sliding angle (SA) of 2°, exhibiting the self-cleaning function. Significantly, it is demonstrated that the water collection efficiency of HPCF can achieve 1.13 g·cm-2·h-1, which is much higher than the value of the blank sample, as well as most of the reported values. It is attributed to the hierarchical porous structure with the ZIF-8 crystals enhancing the surface roughness and endowing the film with the hydrophilic/superhydrophobic regions. This design promotes an optimal balance between droplet nucleation and shedding, significantly enhancing the water harvesting efficiency. Consequently, this work introduces an effective approach for water collection materials suitable for fog/mist conditions and provides an effective solution for the foggy area with water scarcity, demonstrating significance for advancing research aimed at mitigating the worldwide water shortage.
RESUMEN
Passive radiative cooling (PRC) is a zero-energy-consumption technology that reflects sunlight and radiates heat to cold outer space. In this work, a porous poly(vinylidene fluoride)-poly(methyl methacrylate) (PVDF-PMMA) composite film is fabricated by decorating zinc-imidazolate metal-organic framework (MOF) (ZIF-8) particles obtained by phase inversion. Due to the competent scattering via the coral-like hierarchical structures and the vibration excitations of specific functional groups, the prepared film exhibits good solar reflectance (92.6%) and intermediate infrared emittance (99.1%), with an average sub-ambient cooling of 10.4 °C under a solar radiation intensity of 0.6 AM1.5. Additionally, poly(vinylidene fluoride) has a low surface energy, while the ZIF-8 particles and coral-like hierarchical structures enhance the surface roughness, endowing the surface with significant superhydrophobicity characterized by a water contact angle (WCA) of 157.5° and a sliding angle (SA) of 2°. These films exhibit excellent antibacterial properties. When the content of ZIF-8 particles in the film is 300 mg·L-1, the antibacterial rate reaches 100% after 1 h of treatment. Thus, the ZIF-8 porous poly(vinylidene fluoride)-poly(methyl methacrylate) composite (ZPPP) film has potential application prospects in areas with high health and environmental requirements, such as cold chain transportation and public spaces.