I never knew Orchids act as the air purifiers, well I never tried to grow them indoor so having not much idea about their plantation.
citrus trees and olives can do well in large pots in a bright conservatory or similar, and can go outside in the warmer months.
I've successfully sprouted some citrus trees from both supermarket bought Lemons, and oranges. They'll never bare fruit of course, but look very pretty and their leaves leave a citrusy smell as well.