Self-assembly-dominated hierarchical porous nanofibrous membranes for efficient high-temperature air filtration and unidirectional water penetration

Increasingly-severe air pollution problem dominated by various air pollutants makes the development of air filtration materials a hotspot. A multi-functional air filter with high efficiency and high temperature resistance was produced using a co-electrospinning method combined with subsequent impregnation treatment. Herein, Cu-MOF was assembled onto polyimide (PI) nanofibers to construct a hierarchical porous structure. Diamine monomers containing amide bonds were copolymerized in the PI skeleton to activate the surface sluggishness of PI. β-cyclodextrin (β-CD) was used as PI fiber inducer to achieve the self-assembly of Cu-MOF crystals via hydrogen bonding. On one hand, PI/CD-MOF nanofiber filter possesses an excellent PM0.3 filtration efficiency (99.85%) and a low pressure drop (136 Pa), which are attributed to high specific surface area of the nanofibrous filter. On the other hand, the filter demonstrates the optimal performance in terms of CO2 adsorption due to the outstanding open metal sites of Cu-MOF. In particular, Janus double-layer composite nanofibrous membrane, which consists of PI/CD-MOF and PI membranes, has unique unidirectional water permeability performance and long-term filtration stability. Base on the above studies, this preparation strategy could provide idea for the development of multifunctional air purifiers.