Check out this short video from TED talks by Kamal Meattle... on the purification potential of indoor plants... not a new idea, but some new attention and some good fodder for discussion.
From TED: "With its air-filtering plants and sustainable architecture, Kamal Meattle's office park in New Delhi is a model of green business. Meattle himself is a longtime activist for cleaning up India's air." The three plants mentioned in this short video include the Areca Palm, Mother-in-law's Tongue, and Money Plant - which offer a range of beneficial CO2 conversion. These are not the only ones, but it's interesting how Meattle's project quantifies the amount of plants to create air quality per person... plus all of that indoor planting and other benefits (i.e. views of green plants) can't be bad as well.
Some more info from a previous post - making the case for indoor living walls.