If photocatalytic clothing can purify the air as the wearer moves around, then why not apply a similar concept to architectural materials to help cleanse the air outside? That is the premise behind aluminum brand Alcoa’s Reynobond with EcoClean, an “architectural panel that cleans itself and the air around it,” in the company’s own words. Introduced in 2011, Alcoa’s innovation is the result of a process that applies a titanium dioxide coating called EcoClean to the prepainted aluminum surface of its Reynobond architectural panels. Utilizing natural sunlight, the coating then acts as a catalyst to break down organic pollutants on its surface and in the air around it; the harmless matter that results is then washed away by rainwater, the New York-based firm says. Some 10,000 square feet of EcoClean has the smog-eradicating power of approximately 80 trees, the company notes, which is equivalent to offsetting the nitrogen oxide created by the pollution output of four cars per day. We’ve already seen rooftop solar panels and wind turbines, but the addition of smog-cleansing capabilities to buildings could be a revolutionary one, especially in cities where smog is a recognized problem. How else can architects and builders use this process?