On the basis of high-level quantum chemical calculations, closed-cage carboranes are shown to be prospective nanoscale mass selective conveyors via a photochemical switch. A mechanism is evidenced in which stable carborane boxes with lithium as endohedral atom, Li@CB11H12, can be photoinduced to sequentially evolve opening the cage, releasing the internal atom through a window in the box structure, and closing the cage toward either ionic or neutral channels where the charge or spin of the fragments may be controlled. (c) 2006 Elsevier B.V.. All rights reserved.