Puffy hierarchical nanonet structured multifunctional membranes for NO degradation and ultrafine dust filtration

Multifunctional nanofibrous catalytic membranes are used for comprehensive treatment of fine particulate matter (PM) and toxic gaseous contaminants. However, the need for high purification efficiency with low resistance presents a unique challenge. Herein, a method of optimizing the morphology of manganese oxide (MnO_x) on Zr-TiO₂ (TZ) nanofiber membranes was developed to remove ultrafine PM and nitric oxide (NO) efficiently with relatively low pressure drops. After tailoring the hydrothermal solution properties, the MnO₂ ultrafine nanowires (≈22 nm) and Mn₃O₄ nano-octahedra assembled with scaffold nanofibers formed dual-network structures with high gas permeabilities, superior redox properties, and abundant surface acidities. The resultant M₂TZ (2-MnOx/Zr-TiO₂) catalytic membranes exhibited exceptional NH₃ selective catalytic reduction (NH₃-SCR) activity (T₉₀ = 215 °C) with a gas hourly space velocity of 75,000 h⁻¹, as well as outstanding SO₂ and H₂O tolerance and long-term stability. Meanwhile, owing to the puffy hierarchical nanonet structure, the M₂TZ catalytic membranes also show a high filtration efficiency of 99.99% for PM_0.3 removal with a low air resistance of 125 Pa, high air permeability of 1259 m³ m⁻² h⁻¹ kPa⁻¹, and satisfactory PM capture at 300 °C. This work may shed light on the design of advanced multifunctional membranes for air pollutant purification.