THE UNIT-CELL OF THE GALLOSILICATE MESOPOROUS MOLECULAR-SIEVE [SI,GA]-MCM-41 IS SIGNIFICANTLY SMALLER THAN IN THE PURELY SILICEOUS [SI]-MCM-41

The unit cell parameter of [Si, Ga]-MCM-41 is much smaller than that o f [Si]-MCM-41, its purely siliceous counterpart, and decreases with th e increased content of structural gallium. The thickness of the channe l wall falls linearly with the decreased fraction of S-4 at the Q(4) s ites. The channel diameter is also affected. The effect, which can be used for 'fine tuning' of the porosity, is caused by the more difficul t condensation of gallosilicate polyanions in comparison with silicate polyanions. Samples with higher gallium contents have a broader distr ibution of pore sizes.