With the upgrading of industries such as coal chemical industry, oil and gas processing, and semiconductor manufacturing, the demand for air filtration technologies and materials has been continuously increasing to ensure the production and the sustainable development of the environment. Such demands include the synergetic treatment of fine particulate matter (PM) and harmful gases, as well as the development of novel filtration materials with both environmental friendliness and multifunctional properties. Traditional cellulose paper-based filtration materials suffer from insufficient mechanical strength and stability. By combination with inorganic rigid fibers, we hope to fabricate filtration materials that integrate high strength, multi-functionality, and flexibility, thereby be applicable under complex operating conditions.

Recently, the Energy and Chemical Engineering Research Center in the Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, has made progress in development of environmentally friendly and multifunctional air filtration materials. The research team used Lyocell fibers and basalt fibers as raw materials, and prepared several composite fiber filtration materials via a wet-laid process (Fig. 1A). These materials exhibit excellent flexibility. Compared with pure cellulose fiber-based filtration materials, the burst strength and tear strength of the composite materials (incorporated with basalt fibers) have been significantly improved. Furthermore, zeolitic imidazolate framework-8 (ZIF-8) was in-situ grown on the surface of the filtration materials, endowing them with outstanding air purification and antibacterial properties. The resulting material achieved a filtration efficiency of 97.72% for PM₀.₃. Surface functionalization with ZIF-8 notably enhanced the harmful gas adsorption capacity of the filtration materials: the SO₂ adsorption capacity increased by 93%, and the toluene adsorption capacity increased by 111.5%, demonstrating the ability to synergistically capture particulate matter and harmful gases. Basalt fibers imparted excellent heat resistance to the filtration materials, enabling them to maintain stable filtration performance even at 250 °C. In addition, the loaded ZIF-8 can release Zn²⁺ ions, giving the filtration materials broad-spectrum antibacterial activity. The antibacterial efficiency against E. coli, S. aureus, and S. pneumoniae exceeded 99.8%, and good antifungal effects were also observed. Besides, the composite filtration materials are fabricated using natural biomass and mineral fibers (Lyocell and basalt fibers) via an adhesive-free process, resulting in a good degradability for the filter media. After 21 days of soil burial, the mass loss rate of the materials reached 32.2%. Overall, this research provides an efficient, multifunctional, and sustainable solution for air filtration in complex environments.

Relevant research results have recently been published in the Journal of Hazardous Materials. This work was supported by projects including the Talent Program of the Chinese Academy of Sciences and the Xinjiang "Tianchi Talents" Program.

Fig. 1 Preparation and performance of environmentally friendly multifunctional air filter materials (A: Schematic diagram of filter material preparation; B: Flexibility of the filter material; C: PM_0.3 filtration performance; D: Antibacterial performance).