Particulate matter 2.5 (PM2.5) has become a public hazard to people’s lives and health. Traditional melt-blown membranes cannot filter dangerous particles due to their limited diameter, and ultra-fine electrospinning fibers are vulnerable to external forces. Therefore, creating highly efficient air filters by using an innovative technique and structure has become necessary. In this study, a combination of polypropylene (PP) melt-blown and polyvinyl alcohol (PVA)/zeolite imidazole frameworks-8 (ZIF-8) electrospinning technique is employed to construct a PP/PVA/ZIF-8 membrane with a hierarchical fibrous structure. The synergistic effect of hierarchical fibrous structure and ZIF-8 effectively captures PM2.5. The PP/PVA composite membrane loaded with 2.5% loading ZIF-8 has an average filtration efficacy reaching as high as 96.5% for PM2.5 and quality factor (Qf) of 0.099 Pa−1. The resultant membrane resists 33.34 N tensile strength and has a low pressure drop, excellent filtration efficiency, and mechanical strength. This work presents a facile preparation method that is suitable for mass production and the application of membranes to be used as air filters for highly efficient filtration of PM2.5.

A two‐step strategy is used to produce micro–nano composite filters that are flexible and exhibit charge recovery. Polytetrafluoroethylene (PTFE) electret powders are incorporated during the process to provide melt‐blown micro–nano membranes with good charge recovery and improved fiber fineness. Then the advantages of the nanofiber membrane are utilized to load the PTFE suspension onto the surface of melt‐blown microfiber membranes to construct a composite filtration membrane with a micro–nano structure, to achieve high‐efficiency and gradient filtration. The test results indicate that the gradient filtration composite membranes exhibit 100% filtration efficiency against 2.5 μm particles, 94.96% filtration efficiency against 0.200–2.5 μm particles and 95.39% filtration efficiency against 0.200–4.595 μm particles, which is 232.02% higher than that of polypropylene membranes. In addition, the gradient filtration composite membranes have a pressure drop that is only 86 Pa and a quality factor of 0.0358 Pa−1. Featuring excellent electret property and charge recovery rate, the gradient filtration micro–nano composite membranes are outstanding filters that have high filtration efficiency, low pressure drop, stable surface potential and excellent thermal stability. © 2022 Society of Industrial Chemistry.

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