The importance of T...T...T angles in the feasibility of zeolites

The database of prospective zeolites (www. hypotheticalzeolites.net) has been screened in search of feasible zeolites. Previous criteria of zeolite feasibility have been reviewed, based on descriptors such as energy, density, average and distribution of ring sizes, and more importantly that of Li et al. (LID criteria) presented recently [Angew. Chem. Int. Ed. 2013, 52, 1673], based on Si–O, O...O, and Si...Si distances of SLC-minimised structures. In spite of the still large number of feasible zeolites according to this and other criteria, a number of researchers wonder why there are so many feasible and so few synthesised zeolites. Without answering this difficult question, a new criteria is proposed in this study based on the fact that T...T...T angles (T is tetrahedral atom) show specific ranges of values depending on the ring size to which they belong. Based on improved definitions to count and enumerate rings in zeolites, and with data from the IZA database, we introduce the TTT criteria, which we propose to use after the LID criteria, to further narrow the space of feasible zeolites.