Building material that can reduce surrounding emissions within an 8 foot area?! How cool! There is a chemical called titanium dioxide that has been used in coatings for metal, concrete, and other building materials as a deodorizer, to keep things white, and as a general preserving agent. But, it has been found that titanium dioxide is also useful in reducing polluting agents in smog. It undergoes a chemical reaction that breaks down the molecular structure of smog when it is exposed to sunlight. This process is photocatalysis.
If you apply a coating that contains titanium dioxide to a structure or surface, smog in the immediate area will be reduced. Some say as much as 60%. Scientists and engineers in Japan and Italy have been testing out the benefits of titanium dioxide, though the properties of this material have been explored since the 1980s. In Milan, coating containing titanium dioxide was used in order to keep a white church white and has been added to pavement on roads surrounding the city.
Titanium dioxide coating can be used on buildings, asphalt, sidewalks, and many other surfaces. Though the area of smog reduction impact is limited, it is nevertheless a critical area because it falls within the living/breathing spaces for humans in urban centers, and can directly help with car emissions on roads.