Subnanometer metal organic framework pores can selectively transport alkali metal ions of the same valence and similar sizes.

Herein, we report for the first time on the fabrication of a robust, thermoresponsive polymer membrane produced by the combination of an elastic polyurethane (TPU) microfiber web and poly(N-isopropylacrylamide) (PNIPAM). PNIPAM hydrogel is evenly coated on the surface of TPU microfibers, and thus, the wettability of TPU-PNIPAM membrane is amplified by taking advantage of the hierarchical structure and increased surface roughness. The TPU-PNIPAM membrane possesses switchable superhydrophilicity and superhydrophobicity as the temperature of membrane changes from 25 to 45 °C. The composite membrane is shown successfully able to separate a 1 wt % oil-in-water emulsion and 1 wt % water-in-oil emulsion at 25 and 45 °C, respectively, with a high separation efficiency of ≥99.26%. Furthermore, the composite membranes show excellent mechanical properties, and they are highly flexible and mechanically tough. The smart composite membranes reported here have shown great potential for further development for practical high-efficiency oil-water separations.

Light-responsive materials with high adsorp on capacity and sunlight-triggered regenerability are highly desired for low-cost and environmentally friendly industrial separa on processes. Here we report a poly(spiropyran acrylate) (PSP) func onalized metal-organic framework (MOF) as sunlight-regenerable ion adsorbent for sustainable water desalina on. Under dark condi ons, the zwi erionic isomer quickly adsorbs mul ple ca ons and anions from water within 30 minutes with high ion adsorp on loading up to 2.88 mmol•g −1 . With sunlight illumina on, the neutral isomer rapidly releases these adsorbed salts within 4 minutes. Single-column desalina on experiments show that PSP-MOF works efficiently for desalina ng saline water. A fresh water yield of 1 139.5 L•kg −1 •per day and a low energy consump on of 0.11 Wh•L −1 would be reached for desalina ng 2,233 ppm synthe c brackish water. Importantly, this adsorbent shows excellent stability and cycling performance. This work opens up a new direc on for designing responsive materials for energy-efficient and sustainable desalina on and water purifica on.Desalina on has been increasingly used to address the escala ng water shortage. Its popularity is due to the wide availability of brackish water and seawater, but even more because desalinated produc on is reliable, easily incorporated into the exis ng urban water supply systems, and has minimal health risks 1,2 . Thermal desalina on processes by evapora on, such as mul -stage flash (MSF) and mul ple effect dis lla on (MED), are widely used to produce fresh water. However, these thermal technologies are highly energy-intensive, e.g., 14-27 kWh•m −3 for MSF or MED, because a minimum latent heat of 2260 kJ•kg −1 is essen al for the vaporiza on of subcooled water 3,4 . An alterna ve approach is to take mineral ions out of salt waters using separa ng mediums, e.g., semipermeable membranes or adsorbents 2,5 . By membrane-based techniques, such as the dominant desalina on technology of reverse osmosis (RO), it consumes a much lower energy of 1.5-2.5 kWh•m −3 for trea ng brackish water, and 4-6 kWh•m −3 for seawater desalina on 4 .However, RO has some drawbacks such as rela vely high energy consump on, and chemical usage in membrane cleaning and dechlorina on 4,6 . Membrane dis lla on as another membrane process requires over 100 kWh•m -3 thermal energy, but it consumes around 1.0 kWh•m -3 of electricity if waste heat or renewable hea ng energy is u lized 7 . Electrochemical process, such as electrodialysis (ED) and capaci ve deioniza on (CDI), are also compe ve

Biological proton channels are sub-1-nm protein pores with ultrahigh proton (H+) selectivity over other ions. Inspired by biological proton channels, developing artificial proton channels with biological-level selectivity is of fundamental significance for separation science. Herein we report synthetic proton channels fabrication based on sulfonated metal–organic frameworks (MOFs), UiO-66-X, X = SAG, NH-SAG, (NH-SAG)2 (SAG: sulfonic acid groups), which have sub-1-nm windows and a high density of sulfonic acid groups mimicking natural proton channels. The ion conductance of UiO-66-X channels follows the sequence: H+ ≫ K+ > Na+> Li+, and the sulfonated UiO-66 derivative channels show proton selectivity much higher than that of the pristine UiO-66 channels. Particularly, the UiO-66-(NH-SAG)2 channels exhibit ultrahigh proton selectivities, H+/Li+ up to ∼100, H+/Na+ of ∼80, and H+/K+ of ∼70, which are ∼3 times of that of UiO-66-NH-SAG channels, and ∼15 times of that of UiO-66@SAG channels. The ultrahigh proton selectivity in the sulfonated sub-1-nm MOF channels is mainly attributed to the narrow window-cavity pore structure functionalized with nanoconfined high-density sulfonic acid groups that facilitate fast proton transport and simultaneously exclude other cations. Our work opens an avenue to develop functional MOF channels for selective ion conduction and efficient ion separation.