Hierarchical porous structure endowing fiber membranes efficient PM removal and HCHO decomposition

Multifunctional air-purifying materials have attracted much attention in dealing with indoor air pollution including particulate matter (PM) and hazardous gaseous pollutants (e.g., HCHO), while its development faces long-term challenges of high efficiency and low resistance. Herein, we fabricated a novel hierarchical porous structure TiO₂–SiO₂ (TS) fiber membrane using a handy electrospinning method. The hierarchical porous structure, comprising micropores and mesopores within fibers and fiber stacking-induced macropores, endows the TS fiber membrane with an astonishing specific surface area of 351.4 m² g⁻¹ and a high gas permeability of 1079.4 m³ m⁻²·h⁻¹·kPa⁻¹. The interconnected pore structure offers additional potential pathways for clean air, which contributes to enhancing PM capture and lower filtration resistance. Consequently, the TS fiber membrane showed a gratifying filtration efficiency of 99.89 % for PM_0.3 and 99.98 % for PM_2.5 at a velocity of 5.33 cm s⁻¹ with an air resistance as low as 69.3 Pa. It is noteworthy that the interconnected microporous-mesoporous structure in fiber also facilitates the adsorption and enrichment of HCHO molecules, thereby increasing the local concentration and thus markedly enhancing the catalytic efficiency. As a result, the membrane demonstrated a photocatalytic removal efficiency of 98.46 % for HCHO under UV light at a high gas velocity of 600 L g⁻¹·h⁻¹. Interestingly, we found that the membrane can maintain good long-term cyclic stability by simply replenishing adsorbed water on the surface. This work would provide new insight for developing advanced multifunctional air purification membranes.