Ionic Salts@Metal-Organic Frameworks: Remarkable Component to Improve Performance of Fabric Filters to Remove Particulate Matters from Air.

The elimination of particulate matters (PMs) from the air is very important for our sustainability. In this study, highly porous metal-organic frameworks (MOFs) like MIL-101 and UiO-67 were first modified, coated onto cotton, and applied in PM removal via filtration. Ionic salts (ISs) like CaCl2 and LiCl, after loading onto the MOFs, remarkably increased the PM removal efficiency. For example, CaCl2(20)@MIL-101/cotton shows 5.7 times the quality factor (QF, which is the most important parameter in filtration) of that of bare cotton and has the most competitive performances in PM removal (with the highest QF of 0.085 Pa-1) compared to any filter modified with porous materials or commercial filters. The noticeable performances of ISs@MOFs can be explained by the contribution of charge separation (that is effective for electrostatic interactions with PMs) of ISs and the high porosity of MOFs. Moreover, how MOFs with small pores of a few nanometers or less can remove large PMs with sizes in the micron range could be explained. Finally, loading ISs onto highly porous materials can be a promising strategy to improve the performances of filters to remove PMs from the air.