Efficient particulate matter removal by metal-organic frameworks encapsulated in cellulose/chitosan foams

Particulate matter (PM) is one of the major air pollutants that is harmful to both environment and human health. Herein, Ti-based metal-organic frameworks (MOFs) of MIL-125 and MIL-125-NH2 were integrated into bacteria cellulose/chitosan foam (BCH) and used as air filters. A directional freeze-drying approach was used to construct foam matrix, in which the meso-/macropores of polymer skeleton contribute to the required accessibility toward MOFs and minimize gas diffusion barriers. Benefiting from the hierarchically porous structure, the composites foam presented superior filtration properties with high removal efficiencies and low pressure drops. The filtration efficiency of MIL-125-NH2@BCH filter for PM2.5 could exceed 99.5% with a good long-time (30 days) stability. The pressure drop is determined to be 39.4 Pa. The filtration mechanisms are attributed to the electrostatic interaction between MOFs and PM particles, the presence of amine groups, as well as the inhibition effect of fibrous polymer network. This work will shed light on the development of MOF-polysaccharide composites for air purification applications.