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 of [Si]-MCM-41, its purely siliceous counterpart, and decreases with the increased content of structural gallium. The thickness of the channel wall falls linearly with the decreased fraction of Si at the Q4 sites. The channel diameter is also affected. The effect, which can be used for ‘fine tuning’ of the porosity, is caused by the more difficult condensation of gallosilicate polyanions in comparison with silicate polyanions. Samples with higher gallium contents have a broader distribution of pore sizes.