The presence of Al vacancies leads

The presence of Al vacancies leads to a small increase in the Si–O distances due to a weakening of the bond, due to softening of the interaction due the presence of the capping silanol groups (of the hydroxyl nest defect). Note that the cell volume of NZ, despite having similar distances is much lower than that of HZ due to the presence of extra-framework cations which have strong interactions with the oxygen atoms of the framework.Suggesting that in dealuminated zeolites the major portion of water molecules is only weakly coordinated to the zeolite structure: whilst when there are more hydroxyl nests, coordination of water molecules to these defects is restricted as they can form intra-nest hydrogen bonds. The fact that all the dealuminated species have essentially dehydrated below 150℃ is also associated with the lack of extra-framework cations, which have the effect of strongly binding the water molecules within the pores. We therefore conclude that the increase in water is due to the availability of sites associated with silanol nests that can form strong hydrogen fond interactions to water. In the case of HZD5, the partially amorphization is likely to be the cause of the decrease in the number of water molecules present.[21]Photoinduced reactions of surface species also take place and are remarkably different on the two types of nanotubes.