Xiamen University (China) [Nature] Future Technologies for Air Purification by “Liquid Gating Technology”

Among air pollutants, respirable particles such as PM10, PM2.5 and ultrafine particles are of particular concern because their small size allows them to penetrate deep into human bronchi and lungs. Straightforward and effective removal of these fine particles relies on the use of filter units consisting of multilayer fibrous or porous materials with surface treatments to either passively block the motion of solid particles or actively capture pollutants on the filter surface. However, these filter units suffer from fouling issues due to the accumulation of particles on their surfaces and internal pores. As a result, the dust-holding capacity of their surfaces fundamentally limits the efficiency and service life of such filter units. Filter units thus need to be regularly replaced or cleaned to maintain optimal performance, with a trade-off between purification efficiency, service life and maintenance cost.

The researchers from Xiamen University has taken a major step to tackle this challenge by employing liquid-based systems, enabling efficient, continuous and maintenance-free air purification. They built a liquid-based system that composed of an ion-doped conjugated polymer-coated matrix infiltrated with a selected functional liquid. As the air to be purified moves through the system in the form of bubbles, the functional fluid provides interfaces for filtration and for removal of particulate matter and pollutant molecules from air. The system is durable, resistant to fouling and corrosion, and capable of removing bacteria or odors. “Here, we are using liquid to function as filter instead of solid materials, which offers more functional flexibility.” Says Xu Hou, the Professor at Xiamen University, and the corresponding author of the study, which is published in Nature with the title “continuous air purification by aqueous interface filtration and absorption”. This filtration approach will be useful for the development of specialist air purifiers that can be in special environments such as hospitals, factories and mines.

Xu Hou, the corresponding author, is a professor at College of Chemistry and Chemical Engineering, and College of Physical Science and Technology, Xiamen University. Yunmao Zhang, a PhD student at Xiamen University, is the first author of the work.

About liquid gating technology

Inspired by alveolar pores, the liquid gating mechanism based on liquid as structural material was first proposed by Xu Hou et al. Over years, Hou group has fleshed out the concept and formed the framework theory of liquid gating technology, sparking the global development of this technology. In 2020, the International Union of Pure and Applied Chemistry (IUPAC) declared liquid gating technology as one of the Top Ten Emerging Technologies in Chemistry. Liquid gating technologies with antifouling and energy-efficient properties in large-scale filtration and separation processes are sufficiently attractive and can potentially accelerate universal accessibility to clean water and sanitation to meet the goals stated in Sustainable Development Goal (SDG) 6 (United Nations Department of Economic and Social Affairs). Liquid gating technologies can promote research on the applications of liquids as structural materials, which have already been demonstrated in science fiction. With the growing demand for versatile and intelligent materials, liquid-based adaptive materials are expected to play important roles in future applications.

This work was supported by the National Natural Science Foundation of China (grant nos. 52025132, 21975209, 21621091, 22021001 and 22121001), the National Key R&D Programme of China (grant no. 2018YFA0209500), the 111 Project (grant nos. B17027 and B16029) and the Science and Technology Projects of Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (grant no. RD2022070601).