Phytic acid, which is a naturally occurring component that is widely found in many plants, can strongly bond toxic mineral elements in the human body, because of its six phosphate groups. Some of the metal ions present the property of bonding with phytic acid to form insoluble coordination complexes aggregations, even at room temperature. Herein, a superhydrophobic cotton fabric was prepared using a novel and facile nature-inspired strategy that introduced phytic acid metal complex aggregations to generate rough hierarchical structures on a fabric surface, followed by PDMS modification. This superhydrophobic surface can be constructed not only on cotton fabric, but also on filter paper, polyethylene terephthalate (PET) fabric, and sponge. Ag, Fe, Ce, Zr, and Sn are very commendatory ions in our study. Taking phytic acid-Fe-based superhydrophobic fabric as an example, it showed excellent resistance to ultraviolet (UV) irradiation, high temperature, and organic solvent immersion, and it has good resistance to mechanical wear and abrasion. The superhydrophobic/superoleophilic fabric was successfully used to separate oil/water mixtures with separation efficiencies as high as 99.5%. We envision that these superantiwetting fabrics, modified with phytic acid-metal complexes and PDMS, are environmentally friendly, low cost, sustainable, and easy to scale up, and thereby exhibit great potentials in practical applications.

Inspired by the water-collecting mechanism of the Stenocara beetle's back structure, we prepared a superhydrophilic bumps-superhydrophobic/superoleophilic stainless steel mesh (SBS-SSM) filter via a facile and environmentally friendly method. Specifically, hydrophilic silica microparticles are assembled on the as-cleaned stainless steel mesh surface, followed by further spin-coating with a fluoropolymer/SiO nanoparticle solution. On the special surface of SBS-SSM, attributed to the steep surface energy gradient, the superhydrophilic bumps (hydrophilic silica microparticles) are able to capture emulsified water droplets and collect water from the emulsion even when their size is smaller than the pore size of the stainless steel mesh. The oil portion of the water-in-oil emulsion therefore permeates through pores of the superhydrophobic/superoleophilic mesh coating freely and gets purified. We demonstrated an oil recovery purity up to 99.95 wt % for surfactant-stabilized water-in-oil emulsions on the biomimetic SBS-SSM filter, which is superior to that of the traditional superhydrophobic/superoleophilic stainless steel mesh (S-SSM) filter lacking the superhydrophilic bump structure. Together with a facile and environmentally friendly coating strategy, this tool shows great application potential for water-in-oil emulsion separation and oil purification.

Stimulus-responsive materials have great potential in advanced controllable oil/water separation applications. Here, a novel, cost-effective, and green approach is developed to produce a pH-responsive smart fabric with switchable wettability. The approach first involves grafting polydopamine (PDA) and cystamine dihydrochloride (cystamine) on a fabric surface to obtain thiol-functionalized fabric (Fabric-SH). Hydrophobic stearyl methacrylate (SMA) and pH-responsive undecylenic acid are then decorated on the Fabric-SH surface through efficient and green photoinduced thiol–ene click coupling chemistry. The obtained fabric exhibits rapidly switchable wettability between superhydrophobicity and superhydrophilicity depending on the contacting liquid pH value and can be applied in controllable separation of various mixtures of water and oil with high efficiency up to 99%. More importantly, the as-prepared fabric is able to realize the separation of oil/water/oil ternary mixtures and can self-clean and repel oil fouling during the separation process. Its superhydrophobicity is robust, showing no significant change after a 500 cycle peeling test. This novel and cost-effective smart cotton fabric exhibits significant potential in satisfying different separation purposes under complicated conditions.

The maximizing daily freshwater yield on the ocean surface necessitates allday water harvesting technologies and materials. This is realizable by taking advantage of the natural sunlight and humid air, which can drive daytime solar desalination and nighttime fog collection, respectively. To this end, two types of hierarchically porous microneedle array structures, which demonstrate superior capabilities for efficient fog capturing and photothermal evaporation, respectively, are prepared. The gel-forged microneedle arrays with Janus wettability are fabricated via a simple and controllable top-down micro-molding process on a porous platform, and porosity within microneedles is further achieved readily by additional freeze-drying treatment. The developed microneedle structure shows an ultrahigh fog harvesting rate up to 30.5 kg m −2 h −1 , enabling high flux water droplet harvesting from moisture during nighttime. In the daytime, a solar evaporation rate of 2.46 kg m −2 h −1 is realized due to the increased evaporative area of the porous microneedle arrays and enhanced photothermal conversion. By uniting these two waterharvesting routes, a daily cycle can ideally deliver an overall water yield close to 200 kg m −2 , which will offer a promising solution for sustaining future lowcost and decentralized clean water production.

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Oil/water separation is widely studied because of the growing discharge of industrial and domestic oily water, as well as frequent petroleum spills; however, on-demand and continuous oil/water separation has seldom been reported. For this purpose, we prepared opposite wetting nickel meshes by creating FeNiO x (OH) y micro-/nanostructures on the surface and further modification. The surface morphology, chemical composition, and the wetting property were investigated by SEM, EDS, XRD, Raman spectrum, XPS, and contact angle measurement. The as-prepared superhydrophilic/underwater superoleophobic and superhydrophobic/superoleophilic meshes could be used for reusable on-demand oil/water separation with high efficiency. Additionally, continuous oil/water separation was realized by integrating the opposite meshes. The current work will be beneficial for the design and development of materials with special wettabilities and the practical application of oil/water separation.

UiO-66 metal–organic frameworks (MOFs) are unstable in some harsh aqueous environments, which limit their practical applications. We demonstrate a postsynthetic modification methodology to transform hydrophilic Zr­(Hf)-UiO-66 into superhydrophobic Zr­(Hf)-UiO-66-SH-y (SH = thiol, y = fluoroalkyl) by introducing long fluoroalkyl chains into organic linkers through a thiol–ene click reaction. Water contact angles of the four modified UiO-66 MOFs are all larger than 150°. The grafted low-surface-energy fluorine-containing groups become an effective protective shield for the MOFs, making them exhibit remarkable stability in extreme conditions such as alkaline (pH = 12), saturated HCl, and high concentration of NaCl solution (20 wt %). The Zr-UiO-66 MOFs grafted with 1H,1H,2H-perfluoro-1-hexene have high CO2 adsorption contents of 1.54 and 2.88 mmol·g–1 at 298 and 273 K, respectively. Moreover, the superhydrophobic MOFs also showed potential application in oil/water separation.

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