Key breakthrough in air purification: new review shows how to cut energy use while boosting indoor air purification

A comprehensive review in Engineering lays out a practical roadmap for the next generation of indoor air-cleaning devices, arguing that the key to better performance lies not in fancier materials but in mastering the physics of mass transfer. By deliberately engineering how pollutants move to—and into—filtration and adsorption media, researchers can simultaneously raise removal efficiency and slash the fan power that currently devours 20%–30% of electricity in Chinese public buildings and even more in cleanrooms.

The paper, led by Jinhan Mo of Shenzhen University and Tsinghua University, coins the term “integration of mass transfer and material regulation.” Instead of treating filter media as passive screens, the team shows how multiscale (milli–micro–nano) and multifield (mass–flow–force) design can turn them into active, low-resistance pollutant traps. For particulate matter (PM), the strategy is electrostatic assistance. When both particles and fibers are oppositely charged, the Coulomb force raises PM migration velocity roughly five-fold at 6 µm from the fiber surface. The resulting electrostatically assisted air (EAA) filters deliver 1–3 orders of magnitude higher “comprehensive quality factor (CQF)” than commercial equivalents once the extra electric-field energy is accounted for.

To keep pressure drop minimal, the authors propose “electrostatically responsive filters”: coarse, low-resistance substrates—polyurethane foam or polyethylene terephthalate (PET)—are lightly coated with high-dielectric-constant cakings such as BaTiO₃ or MnO₂. Physical roll-to-roll gel squeezing works for inexpensive room units, while in-situ polydopamine chemistry gives cleanroom-grade filters 99.48 % efficiency for 0.3–0.5 µm particles at only 9.5 Pa. Either route maintains the large physical porosity that prevents the “tightly compacted medium” problem that plagues conventional high-efficiency particulate air (HEPA) systems.

For gas-phase pollutants like formaldehyde, the review shifts focus from surface area alone to hierarchical pore architecture. Monolithic adsorbents fabricated by direct-ink-writing (DIW) 3D printing replace packed beds of millimeter beads. The printed honeycomb filaments shorten diffusion paths, while sacrificial templates—ammonium carbonate or PMMA microbeads—introduce micron-scale pores that cut Knudsen resistance. A laminated film version with sub-millimeter vertical channels, laser-etched or DIW-ribbed, raises single-pass formaldehyde removal efficiency by 37% and dynamic adsorption capacity by 152% compared with flat films, all without increasing fan load.

The authors caution that real-world deployment must balance space constraints, ventilation face velocity, and the risk of VOCs fouling pores or altering dielectric properties. They call for standardized test protocols and cost-effective manufacturing partnerships between academia and industry. If these challenges are met, the review concludes, electrostatic and structural enhancements could extend filter life, reduce the 200 billion kW·h spent annually on ventilation in China alone, and make high-efficiency air purification viable for extreme environments from deep-sea habitats to lunar bases.

The paper “Advancing Indoor Air Purification by Mass Transfer Enhancement: Bridging the Gap Between High-Performance Materials and Technologies” is authored by Enze Tian, Qiwei Chen, Yilun Gao, Zhuo Chen, Yan Wang, Jinhan Mo. Full text of the open-access paper: https://doi.org/10.1016/j.eng.2025.07.003. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.