A method for preparing a composition including mineral particles functionalized by at least one organic group and having a specific surface defined according to the BET method greater than 500 m2/g, involves: —choosing a phyllosilicate composition, including mineral particles having a thickness of less than 100 nm, a largest dimension of less than 10 μm and belonging to the family of lamellar silicates; —choosing at least one functionalizing agent, from the group formed from the oxysilanes and oxygermanes having at least one organic group, —bringing the phyllosilicate composition into contact with a functionalizing solution including the functionalizing agent, so as to obtain a phyllosilicate composition including mineral particles functionalized by the organic group, while choosing the organic group from the group formed from the cationic heteroaryl groups, the quaternary ammonium groups and the salts of same. The phyllosilicate composition obtained by the method is also described.