TransMaterial has a post on a building coating which can remove pollution from the air - Reynobond with EcoClean.
Reducing air pollution by way of photocatalysis is not limited to concrete. Alcoa Architectural Products has recently partnered with Toto to develop a titanium dioxide coating for their exterior-grade aluminum panels. According to Alcoa, the hydrophobic coating is the world’s first coil-coated, smog-reducing aluminum architectural panel.
In the presence of sunlight, Reynobond with EcoClean causes organic particulate matter near its surface to break down, and this material is washed away later by rain. 10,000 square feet of EcoClean surface has a similar cleansing effect as 80 trees, and can counteract the pollution produced by four cars per day.