Thin-film composite (TFC) membranes show exceptional permeation properties of key importance for many separations. However, their design and development need ultrathin and defect-free nanofilms as the active layer to alleviate the bottleneck of permeation–rejection trade-off. Here, a 25 nm thick film is fabricated on a porous support by introducing polydopamine (PDA) as an adsorption layer, imparting a unique adsorption-assisted interfacial polymerization (IP) strategy. The PDA layer efficiently captures and enriches amine monomers even from ultradilute solution toward uniform stacking on the support, thus generating ultrathin and defect-free films after polymerization. This is superior to the defective one from conventional IP. Such an active layer features ultrafast permeation for organics, favorable solute rejection, and excellent operation stability. Particularly, the acetone permeance of this new TFC membrane reaches 96.3 L m–2 h–1 bar–1, which exceeds that from conventional IP by more than 10 times, ranking among one of the highest performances reported to date. More significantly, the pernicious permeation–rejection trade-off of the TFC membrane is thus alleviated. Besides, this strategy is facile, versatile, and easy to scale-up, giving controllable physical and chemical structures to the active layer. This study may pave a way to well-design highly efficient film materials for various transport and separation applications.
Huanyu Xie,Pai Li,Shuai Xie,Hongchang Jin,Song Jin,Xianghua Kong,Zhenyu Li,Hengxing Ji
Graphical Three is better : Porous organic frameworks is prepared via coupling reaction of diazonium salt as the anode for Li-ion storage, which exhibit high reversible capacities with excellent cycle stability and rate performance. The azo group acts as an electrochemical active site reversibly bonding with Li-ions, and the adjacent oxygen atom electrostatically adsorb Li-ions to promote the lithium storage. Due to the designable structure and capacity, organic materials are promising candidates for lithium-ion batteries. Herein, we report a novel type of porous organic frameworks (POFs) based on the coupling reaction of diazonium salt as the anodes for lithium ion storage. The active center containing an azo group and the adjacent lithium-philic adsorption site is constructed to investigate the electrochemical behaviors and reaction mechanism. As synthesized POF material (named as POF-AN) exhibits high reversible lithium storage capacities of 523 mAh g −1 at 0.5 A g −1 and 445 mAh g −1 at 2.0 A g −1 after 1500 cycles, showing excellent cycle stability and rate performance. The detailed characterizations reveal that the azo group can act as an electrochemical active site that reversibly bonds with Li-ions, and the adjacent oxygen atoms can electrostatically adsorb with Li-ions to promote the lithium storage reaction. This adsorption-assisted three-atom redox center is beneficial to synergistically enhance the adsorption and intercalation of lithium ions, which can further improve the capacity and cycle stability. By replacing the precursor, it is also facile to synthesize more similar structure types. The reversible redox chemistry of the adsorption-assisted three-atom active center provides new opportunities for the development of long lifespan and high-rate organic anodes.
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