Toward high-performance fibrillated cellulose-based air filter via constructing spider-web-like structure with the aid of TBA during freeze-drying process

In consideration of the healthcare issues caused by Particulate Matter (PM) pollution, developing high-performance air-filter materials especially aiming at filtering PM_2.5 has attracted great attention. In this work, we fabricated a novel air filter with spider-web-like structure based on renewable and biodegradable fibrillated cellulose fibers, and demonstrated an effective strategy for network structure regulation during freeze-drying process. The results showed that the air filter with spider-web-like structure, whose filtration efficiency for model PM particles with the diameter of 300 nm could exceed 99%, was obtained from a fibrillated cellulose fiber/water/Tert-Butyl Alcohol (TBA) mixture by freeze-drying. The role of TBA in the construction of spider-web-like structure was mainly due to the following two aspects: (1) TBA molecules could promote the separation of microfibrils which acted as the cobwebs in spider-web-like structure. (2) The presence of TBA resulted in air filter transformed from lamellar porous architecture into spider-web-like structure by changing the morphologies and growth kinetics of ice-crystals. Herein, this work paves a way to fabricate high-performance air filters based on renewable materials and the pore-formation mechanism can provide a guide for structure regulation in porous materials.