Mordenite zeolites with diffusion-restricted access to the acid sites located in mono-dimensional 12-ring channels and 8-ring side pockets have found broad applications as catalysts for hydroisomerisation of linear C-5 and C-6 alkanes and other highly relevant acid-catalysed processes. The accessibility of the porous structure of mordenite (MOR) zeolite is traditionally enhanced by dealumination, but this is invariably connected with a dramatic reduction in the aluminium content and corresponding concentration of the acid sites in the zeolites. Here we describe the preparation of MOR zeolite with high micropore volume, three-dimensional supermicropores (d similar to 7.5 angstrom) and good acid site accessibility by concurrent extraction of Si and Al using postsynthesis fluorination alkaline-acid treatment. The concurrent extraction of Si and Al enables formation of more developed super-microporous structure and preservation of the molecular Si/Al. The procedure yields MOR with a crystalline structure in which the Si/Al ratio and the micropore volume can be tailored (Si/Al from similar to 6, V-MI up to 0.25 cm(3).g(-1)) by the chemical conditions of the treatment. The Al-rich 3D supermicroporous structure with accessible Bronsted and Lewis active sites provides strongly enhanced activity, selectivity and long-term catalytic stability in the transformation of n-hexane into the corresponding branched isomers.