CO2 insertion into ion-bombarded porous silica

The damage imparted to porous silica by argon bombardment is stabilized and marked by carrying out the bombardment in a controlled CO2 atmosphere. IR spectroscopy shows that CO2 is inserted via the formation of carboxylate groups which, on heat treatment at 500 degrees C, are converted to ester-like groups and, eventually, after exposure to wet air, to carboxylic groups. Dehydration of these structures restores the ester sites almost reversibly.