Aluminium-boron-silicate MCM-41 mesoporous molecular sieves with Al/B ratio in the range 2-0.5 were characterized by XRD, N-2 adsorption, MAS NMR, and DRIFT, and their acid properties were determined by pyridine (Py) adsorption. (Al+B)-MCM-41 samples were prepared by two procedures: (i) direct synthesis by using TEOS, H3BO3 and Cl3Al center dot 6H(2)O as silica, boron and aluminum Sources, respectively and (ii) the as-synthesized samples obtained in (i) were suspended in 300 mL of NH4F 0.1 M for 34 h. The aluminum-boron-silicate MCM-41 materials treated with NH4F improved both the selectivity to epsilon-caprolactam (related mainly to boron content) and the life span (related mainly to NH4F treatment).