sp3-Hybridized carbon atoms are the building blocks for the hypothetical carbon modifications described here, which were obtained by replacing the MO4/2 units in zeolites (M = Si, Al, etc.) with C. According to calculations the modifications derived form zeolite ZSM-39 and melanophlogite are the most stable carbon allotropes after graphite and diamond. Their carbon frameworks are constructed of face-sharing fullerene-like C20, C24, and C28 cages and can thus be considered polymerization products of fullernes.

http://dx.doi.org/10.1002/anie.199307011