Multi-scale nanofiber membrane functionalized with metal-organic frameworks for efficient filtration of both PM2.5 and CH3CHO with colorimetric NH3 detection

Air filtration technology for mitigating pollution due to harmful mixtures of particulate matter (PMs) and yellow dust has been continuously improved. However, significantly small-sized airborne contaminants, such as PM2.5, and toxic gases, including volatile organic compounds (VOCs), remain in the atmosphere and critically affect the human health. Therefore, the development of an integrated filtration system with fast detection and high removal efficiency toward various airborne pollutants without significant interference from airflow is required. Herein, we designed a hybrid air filtration system comprising a colorimetric multi-scale nanofiber (NF)/nanonet (NN) membrane and a metal–organic framework (MOF)-decorated mesh substrate to remove PM2.5 and toxic gases in the air. The electrospinning of a halochromic dye (bromocresol purple; BCP) with a polyacrylonitrile solution spontaneously forms spider-web-like NN networks between NFs, which significantly improves the filtration efficiency, particularly for sub-120 nm aerosol particles with a high quality factor of 0.0387 Pa−1. The BCP components in the NF/NN membrane demonstrated ultrafast and reversible colorimetric sensing properties within 5 s when exposed to 20 ppm ammonia gas. Furthermore, the adsorptive UiO-66-NH2 MOF-grown macroporous mesh contributes to the removal of acetaldehyde as well as provides an efficient membrane support with negligible increase in the pressure drop.