Chemical modification of high-quality large-pore M41S materials

M41S materials with a pore diameter of 80 Å and MCM-41 materials with a pore diameter of 30 Å were grafted with a variety of trimethoxysilanes and chlorosilanes. The obtained hybrid materials were characterised by thermogravimetric analysis, nitrogen adsorption measurements and multi nuclear MAS NMR. A comparison of grafting in the liquid and in the gas phase proved that the former method was more efficient: the amount of grafted material was about 20% higher. Of the 80 Å M41S and the 30 Å MCM-41 material, the former resulted in a higher loading of grafted species and a much larger free pore diameter after grafting. It is, therefore, the better starting material for grafting reactions. By optimising the liquid-phase synthesis the loading of grafted material could be increased by 30% compared to the standard method described in the literature. Furthermore, the degree of condensation of the grafted species was higher with the optimised method, as proven by 29Si MAS NMR.