Made from sponge, the filter has excellent mechanical properties and is made of environmentally-friendly materials. The sponge has the potential to help fight air pollution in automobiles and in industry.

Increasing dangers of air pollution

Present in many countries around the world, particulate matter from vehicle exhausts and industrial chimneys pose significant threats to humans and the environment. Air pollution affects our central nervous and respiratory systems.

To try and solve the problem of air pollution and improve the quality of the environment, previous researchers have attempted to build better performance air filters. However, previous models have not performed well in harsh environments; where high temperatures, humidity, or the need for long periods of filtration bring extra challenges.

Building a better performance filter

To build a better performance air filter, the team designed a three-dimensional particle capture device. A simple, sacrificial template method was used to create a polydimethylsiloxane (PDMS) sponge. Then, they applied a polydopamine (PDA) coating onto the sponge skeleton using an in-situ loading method.

A large number of ZIF-8 particles were grown on the PDA coating. ZIF-8 is a metal-organic framework, a class of porous materials that are versatile in their structural and chemical tunability. Metal-organic frameworks exhibit good potential for the application of gas adsorption and air filtration. The abundant pores in the composite sponge provide good air flow, and the ZIF-8 particles enhance the sponge’s filtration performance.

The team tested the new filter under the conditions required for use in filtering vehicle exhausts. Because the sponge was able to be easily shaped and had structural stability, it could be used in different scenarios as needed. In the vehicle exhaust tests, which simulated the pollution emitted by vehicles during normal operation, the composite sponge achieved over 99% efficiency in removing particulate matter.

“This study provides a new idea for designing 3D high-performance air filters that can adapt to harsh environments,” said Yuekun Lai, a professor at Fuzhou University. Because the composite sponge has good structural stability and can also be easily shaped, it is suitable for use in applications ranging from automobile exhausts, industrial chimneys, and kitchen fans.

“In the next step, our research team will explore gas filters that can adapt to higher temperatures, as well as ways to treat certain components of air pollutants, not just particulate matter filtration,” Lai concluded.

This further development will allow the researchers to expand the applications scenarios of gas filters, and improve the potential for practical applications. Lai explained: “Our ultimate goal is to achieve a gas filter that can be used in a variety of environments, and a high-efficiency filter material with a variety of functions.”