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Graphical abstract, Wearing surgical masks remains the most effective protective measure against COVID-19 before mass vaccination, but insufficient comfortability and low antibacterial/antiviral activities accelerate the replacement frequency of surgical masks, resulting in large amounts of medical waste. To solve this problem, we report new nanofiber membrane masks with outstanding comfortability and anti-pathogen functionality prepared using fluorinated carbon nanofibers/carbon fiber (F-CNFs/CF). This was used to replace commercial polypropylene (PP) nonwovens as the core layer of face masks. The through-plane and in-plane thermal conductivity of commercial PP nonwovens were only 0.12 and 0.20 W/m K, but the F-CNFs/CF nanofiber membranes reached 0.62 and 5.23 W/m K, which represent enhancements of 380% and 2523%, respectively. The surface temperature of the PP surgical masks was 23.9 ℃ when the wearing time was 15 min, while the F-CNFs/CF nanocomposite fibrous masks reached 27.3 ℃, displaying stronger heat dissipation. Moreover, the F-CNFs/CF nanofiber membranes displayed excellent electrical conductivity and produced a high-temperature layer that killed viruses and bacteria in the masks. The surface temperature of the F-CNFs/CF nanocomposite fibrous masks reached 69.2 ℃ after being connected to a portable power source for 60 s. Their antibacterial rates were 97.9% and 98.6% against E. coli and S. aureus, respectively, after being connected to a portable power source for 30 min.

Covalent organic frameworks (COFs), a series of crystalline materials with ordered nanopores, are highly desirable for ultrafast and selective nanofiltration. However, COF-based membranes are typically synthesized via difficult synthetic procedures with long reaction time and show poor mechanical properties, which may hinder their widespread applications. Herein, a facile interfacial method is developed to synthesize COF membranes via the synergistic effect of interfacial diffusion and in-phase Brownian motion. Continuous free-standing COF films with a thickness of 111 nm are obtained within only 3 h under mild reaction conditions. Meanwhile, this synthesis method is suitable for the fabrication of COF membranes with a thin-film-composite (TFC) structure, enabling obtained COF membranes good mechanical properties under external forces and practical nanofiltration tests. Compared with other reported nanofiltration membranes, TFC-COFs exhibit state-of-the-art water permeance (173.94 L m2 h−1 bar−1) and superior rejections exceeding 98.50% to dyes larger than 1.3 nm. Precisely selective sieving of obtained TFC-COFs is systematically studied by separating diverse mixed dye solutions. Furthermore, monomers used in this method can be replaced, creating COF-based membranes with customizable functionality to enable a broad range of selective separations.

Traditional nanofiltration membranes (NFMs) formed by interfacial polymerization (IP) present relatively low water permeance due to the limitation of polymer-based supports. This work reports high-performance carbon nanotubes-polyamide (CNTs-PA) NFMs with interlayer and functional layer covalently coupled. These membranes feature an interpenetrating network structure, which leads to an extremely high Congo red rejection of 99.47%. The water permeance of the optimal membrane (48.98 L m-2h−1 bar−1) is much higher than most membranes with similar Congo red rejection. Meanwhile, the obtained membranes show an excellent selectivity to NaCl/dye mixed solution (the selectivity of NaCl/CR is 150.32). Moreover, this work comprehensively demonstrates the aggregation kinetics of dye molecules under different pH environments, which strongly affects the dye rejection of the CNTs-PA membrane. The membrane exhibits a switchable CR release property that the CR rejection is severely disabled (2.12%) under a strong alkaline environment and immediately re-effective (99.38%) after neutralization. Building on these findings, our work expands the possibilities of NFMs in ultrafast molecular sieving and pH-responsive separation.