Photochemistry of Nanocage Ca12Al14-xSixO32Cl2+x (x=0.0 and 3.4) Crystals

We observed the photogenerated color centers in Ca12Al14-xSixO32Cl2+x analogs of Ca12Al14O33 (C12A7) crystals with crystallographic subnanometer-sized cages partially occupied by Cl ions. Excimer laser irradiation created electrons trapped in the cages and holes on nonbridging oxygen 2p orbitals, accompanied by the formation of O-, H-0, and H-. These centers were gradually erased at room temperature in ca. 30 min. These results demonstrate that the cages in C12A7 analogs act as traps for active anionic species and electrons generated by light excitation.