The filtration performance and light transmittance of nanofiber air filters are restricted by their thick fiber diameter, large pore size, and substrate dependence, which can be solved by constructing substrate-free fibrous membranes with true nanoscale diameters and ultrathin thicknesses, however, it has proven to be extremely challenging. Herein, a roust approach is presented to create free-standing polyurethane (PU) nanofiber/nets air filters composed of bonded nanofibers and 2D nanonets for particular matter (PM) capture via combining electrospinning/netting technique and facile peel off process from designed substrates. This strategy causes widely distributed Steiner-tree structured nanonets with diameters of ≈20 nm and bonded scaffold nanofibers to assemble into ultrathin membranes with small pore size, high porosity, and robust mechanical strength on a large scale based on ionic liquid inspiration and surface structure optimization of receiver substrates. As a consequence, the resulting free-standing PU nanofiber/nets filters exhibit high PM1-0.5 removal efficiency of >99.00% and PM2.5-1 removal efficiency of >99.73%, maintaining high light transmittance of ≈70% and low pressure drop of 28 Pa; even achieve >99.97% removal efficiency with ≈40% transmittance for PM0.3 filtration, and robust purification capacity for real smoke PM2.5 , making them promising high-efficiency and transparent filtration materials for various filtration and separation applications.
Keywords: air filtration; free-standing; high-efficiency; nanofiber/nets; transparent.
© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.